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Cardiology

Inferior MI, right ventricular failure, and AV block

Read inferior STEMI through coronary anatomy, right ventricular filling, and AV conduction. Practice reperfusion decisions and recognize evolving complications.

An inferior infarct can produce three different problems at once. The inferior left ventricle is ischemic, the right ventricle may stop delivering enough blood to the lungs, and atrial impulses may fail to reach the ventricles. The useful question is which of those problems is lowering this patient's cardiac output.

A raised jugular venous pressure does not automatically mean that a patient needs diuresis. It also does not prove that more fluid will help. Pair the venous pressure with lung findings, right-sided ECG leads, echocardiography, and the response to treatment.

Read the inferior leads, then locate the branches

Pressure or burning in the upper abdomen, nausea, breathlessness, and sweating can accompany myocardial ischemia. They deserve an ECG and clinical assessment even when the patient calls the sensation indigestion. Chest discomfort remains common in women, and diabetes does not make every infarct painless. Conversely, absence of chest pain cannot exclude an infarct. Sweating increases concern but is not exclusive to cardiac disease. Avoid explaining all epigastric symptoms as direct irritation of one nerve. The clinical task is recognizing an anginal equivalent. [6]

ST elevation in II, III, and aVF during an ischemic presentation identifies an inferior STEMI pattern. Reciprocal depression in aVL, often with depression in I, supports that interpretation. These are different electrical views of the same injury pattern; lateral depression alone does not establish a second infarct. It also cannot exclude coexisting coronary disease. ST elevation reflects acute injury currents, not proof that every cell under that lead is already irreversibly dead. Do not wait for troponin to rise before activating a clear STEMI pathway. [1]

One upstream lesion, several downstream territories

Right-dominant circulation
RCA in the right atrioventricular groove

  • RV branches supply the RV free wall. An occlusion before these branches can add RV dysfunction.
  • The AV nodal branch usually arises near the crux and supplies the AV node.
  • The posterior descending artery supplies inferior and posterior septal territory.

Left-dominant circulation
LCx gives rise to the posterior descending artery. Inferior infarction and AV nodal ischemia can therefore arise from LCx disease.

A branch map, not a drawing of surface anatomy. Dominance names the artery giving rise to the posterior descending artery; it does not name the side containing most heart muscle. [4] [10]

The left main divides into the LAD and LCx. LAD disease usually involves anterior or septal myocardium, whereas LCx disease often affects lateral or posterior territories. Individual branches and dominance matter more than memorizing one artery for every lead. The SA node is high in the right atrium near the superior vena cava; its artery often arises from the RCA, but LCx supply and dual supply occur. [13] SA nodal arterial origin does not reliably follow coronary dominance. The AV node lies in the inferior right atrial septal region. Its arterial supply is more closely related to dominance. [10]

Record right-sided leads early in inferior STEMI. V4R lies at the fifth right intercostal space on the midclavicular line, mirroring standard V4. ST elevation there supports RV involvement, but an isolated lead is not an infallible diagnostic test. If anterior leads V1 to V3 show horizontal ST depression with prominent R waves, consider posterior involvement and record V7 to V9. Posterior extension and RV involvement are separate findings that can coexist. [1] [7]

Try it here · Checkpoint 1 of 3

Make your prediction before reading the choices. A first attempt is just a starting point.

Case 2

A 58-year-old man has 70 minutes of chest pressure. ECG shows ST elevation in II, III, and aVF with depression in aVL. Angiography demonstrates a right-dominant circulation and thrombotic proximal RCA occlusion. Which territory is directly threatened by loss of flow through its posterior descending branch?

Show answer and explanations for case 2

  1. A. Inferior LV and posterior septal myocardium (Best answer)

    In right dominance the RCA supplies the posterior descending artery, explaining this inferior injury pattern.

  2. B. Anterior LV wall supplied by diagonal branches (Why this does not fit)

    Diagonal branches arise from the LAD and are not the stated downstream branch.

  3. C. Lateral LV myocardium supplied by obtuse marginal branches (Why this does not fit)

    Obtuse marginal branches generally arise from the LCx. They are not the posterior descending branch named in this angiogram.

  4. D. Anterior septal myocardium supplied by LAD perforators (Why this does not fit)

    LAD perforators predominantly supply the anterior septum; the stated posterior descending branch instead explains inferior and posterior septal jeopardy.

Takeaway: Use the documented arterial branches to interpret the ECG territory.

Case sources: [1] [4] [10]

Separate a slow sinus node from interrupted AV conduction

With sinus bradycardia, atrial activation itself is slow and each sinus P wave conducts. In AV block, the atria may continue at a normal rate while ventricular activation is delayed or interrupted. Inferior ischemia can affect nodal perfusion and increase vagal influence. The Bezold-Jarisch reflex describes a cardioinhibitory response with bradycardia and hypotension; it can appear during inferior ischemia or reperfusion. Persistent shock should not be assigned to that reflex without checking ventricular function, bleeding, and structural complications. [2] [11]

Read the P-to-QRS relationship

First-degree AV block
Every P wave conducts, with a PR interval longer than 200 ms. The delay is in AV conduction, not necessarily in the sinus node.
Mobitz I, or Wenckebach
PR intervals progressively lengthen before a P wave is not followed by a QRS. The QRS is missing, not the P wave. Inferior MI commonly produces a transient nodal pattern.
Mobitz II
Conducted PR intervals remain constant before intermittent failure of conduction, with other diagnostic criteria satisfied. His-Purkinje disease is a concern. A 2-to-1 strip alone usually cannot distinguish Mobitz I from Mobitz II.
Complete AV block
No atrial impulses conduct. P waves and a slower ventricular escape rhythm are independent. A narrow junctional escape suggests a higher escape origin; a broad slow escape raises concern for distal disease. QRS width alone does not establish the exact site of block.

[2]

Complete AV block does not prove a dead AV node or permanent damage. Some inferior-MI blocks resolve after reperfusion. Stable, asymptomatic Wenckebach can be monitored while the infarct is treated. Hypotension, altered mentation, shock, ischemic discomfort, or acute heart failure attributable to bradycardia requires support. Stop contributing AV nodal suppressants and address hypoxia or electrolyte abnormalities. [2] [3]

For adult bradycardia with hemodynamic compromise, atropine is 1 mg IV, repeatable every 3 to 5 minutes to a maximum total of 3 mg. [12] It blocks muscarinic effects; it does not reopen the artery. If ineffective, transcutaneous pacing and/or dopamine or epinephrine infusion can bridge to expert assessment and transvenous pacing. Do not wait to finish every atropine dose when perfusion remains poor, particularly with a broad escape rhythm.

Confirm pacing with a pulse or arterial pressure response as well as electrical capture. Permanent pacing depends on persistent disease after an appropriate period of observation, not merely on having needed temporary support. [2] [3]

The right ventricle can be full while the left ventricle is underfilled

Follow blood forward and pressure backward
  1. Systemic veins and right atrium
    Poor RV emptying raises upstream venous pressure. Neck veins become distended.
  2. Ischemic right ventricle
    Reduced contractility limits delivery into the pulmonary artery.
  3. Lungs and left ventricle
    Reduced pulmonary flow can limit LV filling. The lungs may remain clear even as systemic output falls.
  4. Aorta and organs
    Reduced forward output produces hypotension, cool skin, confusion, or oliguria.

This explains the classic hypotension, raised JVP, and clear-lung combination. It is most useful for predominant RV failure. Coexisting LV failure or acute MR can produce pulmonary edema. [4]

Right atrial pressure is often disproportionately high relative to pulmonary capillary wedge pressure in predominant RV infarction. Wedge pressure estimates left atrial pressure under suitable measurement conditions. It need not be below normal in every RV infarct. A patient with biventricular injury can have high pressures on both sides. Tamponade and pulmonary embolism can also produce raised JVP with hypotension, so examine the pericardium and both ventricles rather than diagnosing from the triad alone. [4] [5]

If underfilling is contributing and there is no pulmonary congestion, a small monitored crystalloid challenge may improve output. Recheck blood pressure, perfusion, JVP, lung findings, and ultrasound after each increment. More preload helps only while the heart can use it. Excess RV distension can impair LV filling through ventricular interdependence, worsen tricuspid regurgitation, and increase congestion. A small randomized physiological study found that volume loading could raise filling pressures without improving cardiac index in severe RV infarction. That is a reason to reassess, not a universal volume prescription. [4] [8]

Avoid nitrates in suspected RV infarction or hypotension. Withhold beta-blockers during shock, marked bradycardia, or significant AV block. Opioids are not a reflex replacement for nitrates; they can worsen hypotension and delay oral antiplatelet absorption. Diuresis is inappropriate for an underfilled hypotensive patient, but congestion after excessive fluid or combined ventricular failure changes the decision. Persistent low output needs critical care assessment for vasoactive or mechanical support alongside reperfusion. [1] [4]

Try it here · Checkpoint 2 of 3

Make your prediction before reading the choices. A first attempt is just a starting point.

Case 18

A 65-year-old woman with inferior and RV infarction has BP 84/52 mm Hg and clear lungs. Catheter measurements show right atrial pressure 16 mm Hg, wedge pressure 9 mm Hg, and cardiac index 1.7 L/min/m². What best explains this pattern?

Show answer and explanations for case 18

  1. A. RV failure limits left-heart filling despite systemic venous congestion (Best answer)

    High right-sided pressure with relatively low left-sided filling and low output fits predominant RV failure.

  2. B. An isolated hyperdynamic distributive state (Why this does not fit)

    A low cardiac index with the documented RV infarct and disproportionate venous pressure is not a hyperdynamic pattern.

  3. C. Severe isolated LV failure with pulmonary congestion (Why this does not fit)

    That would more commonly raise wedge pressure and cause pulmonary congestion; neither is present here.

  4. D. Isolated hypovolemia reduces cardiac filling despite preserved RV contractility (Why this does not fit)

    Isolated volume loss does not explain the markedly raised RA pressure and documented ischemic RV dysfunction, although underfilling can coexist.

Takeaway: Congested systemic veins can coexist with limited LV filling.

Case sources: [4]

Support perfusion while arranging definitive reperfusion

Obtain IV access, continuous monitoring, and defibrillation or pacing capability. Give oxygen for hypoxemia, rather than routinely when saturation is at least 90%. Aspirin, a P2Y12 inhibitor selected for the reperfusion strategy, and appropriate parenteral anticoagulation address thrombosis. They inhibit platelet activity and clot propagation; they do not replace mechanical or fibrinolytic reperfusion. Initial stabilization and cath laboratory activation happen together. [1]

Primary PCI is preferred when achievable within guideline time targets. The usual system targets are first medical contact to device within 90 minutes for direct presentation to a PCI center and within 120 minutes when transfer is required. For an eligible patient within 12 hours of symptom onset whose expected PCI delay exceeds 120 minutes, fibrinolysis followed by transfer is an alternative. Check contraindications first. Any prior intracranial hemorrhage and active bleeding are absolute contraindications, not just events within a recent three-month window. Shock and complex anatomy require individualized emergency revascularization decisions. [1]

Transfer all patients after fibrinolysis. Failed reperfusion calls for immediate angiography and rescue PCI; successful fibrinolysis still calls for early angiography, generally within 2 to 24 hours. After PCI, TIMI grade 0 means no antegrade passage beyond the obstruction; grade 1 has penetration beyond it without complete distal filling; grade 2 has complete distal filling, with slower filling or clearance than normal; grade 3 describes normal epicardial flow. No grade alone measures collateral supply or proves normal tissue perfusion. [1] [9]

A new finding deserves a new explanation

Sudden pulmonary edema after inferior MI raises concern for acute mitral regurgitation from posteromedial papillary muscle rupture. This is a mitral apparatus problem in the LV, with arterial supply influenced by dominance. A loud apical murmur may occur, but severe acute MR can be quiet. A left sternal murmur with LV-to-RV Doppler flow suggests septal rupture. An effusion with tamponade physiology raises concern for free wall rupture; a contained rupture communicating with the LV is a pseudoaneurysm. Obtain urgent echo and surgical assessment for suspected mechanical complications. [5]

RV enlargement can stretch the tricuspid annulus and impair leaflet coaptation, causing functional TR. An inspiratory increase in its systolic murmur and systolic hepatic pulsation fit regurgitation into systemic veins. Do not rename the mitral posteromedial papillary muscle as a tricuspid structure. New atrial fibrillation is another possible complication and requires a fresh rhythm assessment rather than assuming all post-infarct rhythm changes are AV block. [4] [3]

Inferior ST elevation prompts reperfusion activation and right-sided leads. A slow ventricular rate prompts analysis of atrial conduction and perfusion. Raised JVP prompts assessment of both ventricles and the pericardium. New shock, pulmonary edema, a murmur, or recurrent ischemic symptoms prompts immediate reassessment. Persistent ST elevation at 48 hours does not by itself diagnose an aneurysm or prove a patent stent. [1] [5]

Try it here · Checkpoint 3 of 3

Make your prediction before reading the choices. A first attempt is just a starting point.

Case 30

A 66-year-old woman recovering from RV infarction develops a systolic murmur that increases with inspiration and systolic hepatic pulsation. Echo shows RV enlargement, a dilated tricuspid annulus, intact leaflets and chordae, and systolic RV-to-RA flow. What mechanism explains the regurgitation?

Show answer and explanations for case 30

  1. A. Functional failure of leaflet coaptation from RV and annular enlargement (Best answer)

    The valve tissue is intact, but the enlarged annulus and altered RV geometry prevent effective closure.

  2. B. Rupture of a mitral papillary muscle into the LA (Why this does not fit)

    That would produce MR and does not match the intact tricuspid apparatus and RV-to-RA flow.

  3. C. A ventricular septal defect (Why this does not fit)

    No trans-septal flow is described; the regurgitant jet passes through the tricuspid valve.

  4. D. Tricuspid vegetation destroying a leaflet (Why this does not fit)

    No vegetation or leaflet destruction is present, while functional geometry is directly demonstrated.

Takeaway: Use actual echo anatomy to distinguish functional TR from structural rupture.

Case sources: [4]

Practice the clinical decisions

Case 1

A 64-year-old woman develops upper abdominal pressure and nausea while carrying groceries. Symptoms persist for 45 minutes despite an antacid. She is sweaty, BP is 108/68 mm Hg, and there is no abdominal guarding or hematemesis. Which investigation should be obtained promptly to assess a potentially time-sensitive cause?

Show answer and explanations for case 1

  1. A. Outpatient Helicobacter pylori testing (Why this does not fit)

    This evaluates chronic dyspepsia, but it cannot address the acute exertional symptoms and sweating described here.

  2. B. 12-lead ECG (Best answer)

    Exertional upper abdominal pressure with autonomic symptoms can be an anginal equivalent. An ECG assesses acute coronary ischemia without waiting for classic chest pain.

  3. C. Abdominal CT as the first test (Why this does not fit)

    Imaging may become appropriate for abdominal findings, but the absence of guarding and the exertional pressure make an immediate ECG a better initial discriminator.

  4. D. A second antacid trial before cardiac testing (Why this does not fit)

    Response to an antacid does not reliably exclude ischemia, and the first trial has not resolved her symptoms.

Takeaway: Upper abdominal discomfort can warrant the same initial ischemia assessment as chest discomfort.

Case sources: [1] [6]

Case 3

A 71-year-old man with 50 minutes of chest pressure has inferior ST elevation and complete AV block with a narrow escape. Angiography shows a dominant LCx giving the posterior descending and AV nodal branches; the RCA is patent. Which lesion best accounts for both findings?

Show answer and explanations for case 3

  1. A. A distal LAD lesion beyond its septal branches (Why this does not fit)

    That location does not match the documented inferior and nodal arterial supply.

  2. B. An isolated first diagonal occlusion (Why this does not fit)

    This would not interrupt the documented LCx-derived AV nodal and posterior descending branches.

  3. C. An isolated acute marginal RCA occlusion (Why this does not fit)

    It threatens RV myocardium but does not explain loss of the two stated LCx-derived territories.

  4. D. LCx occlusion upstream of those branches (Best answer)

    The stated left-dominant anatomy places both inferior myocardium and AV nodal supply downstream of the LCx lesion.

Takeaway: Left dominance changes the culprit artery inference.

Case sources: [2] [10]

Case 4

A 62-year-old woman has acute chest pressure and ST elevation in II, III, and aVF. Lead aVL shows simultaneous ST depression. Echo shows inferior hypokinesis without a separate lateral abnormality. Which interpretation best fits the aVL finding?

Show answer and explanations for case 4

  1. A. Proof of a separate lateral infarction (Why this does not fit)

    Reciprocal depression does not by itself establish necrosis in a second territory.

  2. B. Diagnostic evidence of isolated posterior infarction (Why this does not fit)

    Posterior reciprocal changes are sought particularly in V1 to V3; aVL depression fits the inferior injury vector here.

  3. C. A reciprocal electrical view of the inferior injury (Best answer)

    The simultaneous territorial elevation and opposing lead depression can arise from one inferior injury pattern.

  4. D. Proof that no other coronary stenosis exists (Why this does not fit)

    Reciprocal changes explain this tracing but cannot exclude additional coronary disease.

Takeaway: Reciprocal depression supports localization without providing a complete coronary inventory.

Case sources: [1]

Case 5

A 75-year-old man with inferior STEMI becomes lightheaded. BP is 82/50 mm Hg, neck veins are distended, and breath sounds are clear. Which additional ECG recording most directly evaluates associated RV injury?

Show answer and explanations for case 5

  1. A. V7 to V9 only (Why this does not fit)

    These posterior leads address posterior LV injury, a different question from RV involvement.

  2. B. V3R and V4R (Best answer)

    Right-sided precordial leads provide an electrical view of the RV; they complement the examination and echo.

  3. C. A longer aVL strip only (Why this does not fit)

    It may show reciprocal inferior changes but does not directly sample the RV free wall.

  4. D. A limb-lead tracing without precordial leads (Why this does not fit)

    Removing precordial information would not answer the RV localization question.

Takeaway: Inferior STEMI warrants early assessment of right-sided leads.

Case sources: [1] [7]

Case 6

A 55-year-old woman has inferior ST elevation and 2 mm horizontal ST depression with prominent R waves in V1 to V3. V4R is isoelectric. Which recording best assesses the additional territory suggested by the anterior depression?

Show answer and explanations for case 6

  1. A. Posterior leads V7 to V9 (Best answer)

    Anterior depression with prominent R waves can mirror posterior ST elevation, so posterior leads assess extension.

  2. B. Repeat only V4R (Why this does not fit)

    V4R assesses RV injury and does not substitute for posterior leads.

  3. C. An esophageal rhythm lead (Why this does not fit)

    It may improve atrial activity recognition but is not the standard test for posterior STEMI.

  4. D. Only a 30-second lead II strip (Why this does not fit)

    A longer rhythm strip evaluates conduction, not the suspected posterior injury distribution.

Takeaway: Posterior extension and RV involvement are different additions to an inferior infarct.

Case sources: [1]

Case 7

A 68-year-old man undergoing PCI has an RCA occlusion before the origins of several RV marginal branches. A second patient has a lesion distal to those patent branches. Which additional problem is more directly predicted in the first patient?

Show answer and explanations for case 7

  1. A. Isolated inferior LV injury without RV involvement (Why this does not fit)

    Both lesions may threaten downstream inferior myocardium, but loss of the RV branches adds an extra threatened territory in the first patient.

  2. B. Isolated high lateral LV ischemia (Why this does not fit)

    High lateral injury more directly implicates left coronary branches; it is not the additional territory lost by interrupting the stated RV branches.

  3. C. An isolated posterior septal infarct with fully preserved RV perfusion (Why this does not fit)

    Posterior septal injury may occur downstream, but preserved RV perfusion is less likely when all stated RV branch inflow is interrupted.

  4. D. RV free-wall ischemia (Best answer)

    The proximal lesion interrupts RV branch inflow, while the distal lesion may spare it.

Takeaway: Describe lesion location relative to branches rather than treating proximal and distal as absolute labels.

Case sources: [4]

Case 8

A 60-year-old man develops a pulse of 46/min during inferior ischemia. ECG shows a sinus P wave before every QRS, a constant PR of 170 ms, and QRS duration of 90 ms. BP is 116/70 mm Hg and he is alert. Which rhythm is present?

Show answer and explanations for case 8

  1. A. Complete AV block (Why this does not fit)

    Complete block requires failure of atrial impulses to conduct; this strip has consistent one-to-one conduction.

  2. B. Mobitz II AV block (Why this does not fit)

    No nonconducted P waves are described, so intermittent conduction failure is absent.

  3. C. Sinus bradycardia (Best answer)

    A slow sinus rate with intact P-to-QRS conduction defines sinus bradycardia.

  4. D. Atrial fibrillation (Why this does not fit)

    Organized sinus P waves with regular conduction contradict atrial fibrillation.

Takeaway: A low pulse does not itself establish AV block.

Case sources: [2]

Case 9

A 73-year-old woman is monitored after RCA reperfusion. Each P wave is followed by a QRS, the PR interval is consistently 260 ms, and the rate is 64/min. She has no dizziness. Which finding is present?

Show answer and explanations for case 9

  1. A. Mobitz I AV block (Why this does not fit)

    There is no progressive PR lengthening followed by a nonconducted atrial impulse.

  2. B. First-degree AV block (Best answer)

    The PR exceeds 200 ms but every atrial impulse conducts.

  3. C. Complete AV block (Why this does not fit)

    The persistent P-to-QRS relationship excludes complete AV dissociation in this tracing.

  4. D. Sinus arrest (Why this does not fit)

    Regular P waves are present; sinus arrest would produce a pause in sinus atrial activation.

Takeaway: A long PR with one-to-one conduction is first-degree block.

Case sources: [2]

Case 10

A 66-year-old man after inferior MI has PR intervals of 180, 220, and 280 ms, then a P wave without a QRS; the sequence repeats. BP is 122/74 mm Hg and he denies presyncope. What is the best rhythm-directed approach while infarct care continues?

Show answer and explanations for case 10

  1. A. Continuous monitoring and reassessment (Best answer)

    This is stable Mobitz I. Reperfusion and observation are appropriate without immediate invasive pacing.

  2. B. Immediate permanent pacemaker implantation (Why this does not fit)

    This transient nodal pattern has not established an irreversible pacing indication.

  3. C. IV digoxin to improve conduction (Why this does not fit)

    Digoxin can increase AV nodal suppression and aggravate this block.

  4. D. Synchronized cardioversion (Why this does not fit)

    There is no unstable tachyarrhythmia for cardioversion to terminate.

Takeaway: Stable Wenckebach is managed differently from bradycardia causing hypoperfusion.

Case sources: [2] [3]

Case 11

A 69-year-old woman with an inferior STEMI has regular P waves at 92/min and regular narrow QRS complexes at 41/min. The PR relationship continually changes and no atrial impulses conduct. Which diagnosis is established?

Show answer and explanations for case 11

  1. A. Sinus bradycardia (Why this does not fit)

    The atrial rate is not slow, and atrial and ventricular activation are not linked.

  2. B. Atrial flutter with fixed conduction (Why this does not fit)

    There are sinus P waves and no organized flutter activity or fixed atrioventricular relationship.

  3. C. First-degree AV block (Why this does not fit)

    First-degree block preserves one-to-one conduction with a fixed prolonged PR.

  4. D. Complete AV block (Best answer)

    Atrial impulses fail to conduct while an independent slower escape activates the ventricles.

Takeaway: Complete block is defined by conduction failure, not by an assumed permanently infarcted node.

Case sources: [2]

Case 12

A 57-year-old man with inferior STEMI has a short ECG strip showing every second P wave blocked. The conducted PR intervals are 210 ms and QRS complexes are narrow. Which statement is most accurate?

Show answer and explanations for case 12

  1. A. The strip proves Mobitz II because some P waves fail to conduct (Why this does not fit)

    A 2-to-1 pattern does not show the consecutive conducted intervals needed for this classification.

  2. B. The strip proves complete AV block (Why this does not fit)

    Half of the atrial impulses appear to conduct with a fixed relationship, so complete block is not established.

  3. C. The strip shows 2-to-1 AV block with an uncertain subtype (Best answer)

    Additional rhythm information and clinical assessment are needed to localize and classify the block.

  4. D. The narrow QRS proves the conduction disorder is harmless (Why this does not fit)

    QRS width is informative but cannot guarantee stability or exclude progression.

Takeaway: Do not force a Mobitz subtype onto a 2-to-1 strip.

Case sources: [2]

Case 13

A 63-year-old man becomes nauseated and hypotensive during restoration of flow to an inferior infarct. His sinus rate falls from 78 to 39/min. Echo shows no effusion or new severe ventricular dysfunction, and the episode resolves after atropine. Which mechanism best fits?

Show answer and explanations for case 13

  1. A. A new fixed septal rupture (Why this does not fit)

    No new structural lesion is seen, and prompt resolution with vagolysis is not the expected behavior of a rupture.

  2. B. A vagally mediated cardioinhibitory reflex (Best answer)

    The transient bradycardia and hypotension during inferior reperfusion fit the Bezold-Jarisch response.

  3. C. Direct beta-1 stimulation (Why this does not fit)

    Adrenergic beta-1 stimulation would generally increase the sinus rate rather than explain its fall.

  4. D. A baroreceptor response to acute hypertension (Why this does not fit)

    A hypertensive stimulus could produce baroreflex slowing, but this episode begins with hypotension during inferior reperfusion rather than a rise in arterial pressure.

Takeaway: A transient vagal contribution can coexist with ischemic nodal disease.

Case sources: [2] [11]

Case 14

A 72-year-old woman with inferior STEMI has a narrow-complex rate of 36/min, confusion, and BP 76/44 mm Hg. Pacing pads are applied and reperfusion is being arranged. Which atropine regimen matches current adult resuscitation guidance?

Show answer and explanations for case 14

  1. A. 1 mg IV, repeat as needed every 3 to 5 minutes; maximum 3 mg (Best answer)

    This is the current adult dose; persistent instability also requires timely escalation rather than waiting for the maximum.

  2. B. 0.5 mg IV, repeat as needed every 3 to 5 minutes; maximum 3 mg (Why this does not fit)

    This is the older adult algorithm dose; current AHA adult bradycardia guidance uses 1 mg per dose.

  3. C. 1 mg IV once, with no repeat doses permitted (Why this does not fit)

    The adult algorithm permits repeat 1 mg doses to a total of 3 mg while reassessing perfusion and arranging escalation when needed.

  4. D. 1 mg IV, repeat as needed every 3 to 5 minutes; maximum 6 mg (Why this does not fit)

    The interval and individual dose fit, but the adult algorithm limits the total to 3 mg.

Takeaway: Use the current adult atropine dose and reassess perfusion after treatment.

Case sources: [3] [12]

Case 15

A 61-year-old man with inferior STEMI remains confused with BP 70/42 mm Hg after atropine. ECG shows complete AV block with a broad escape at 28/min. Transcutaneous pacing is immediately available. What is the best next action?

Show answer and explanations for case 15

  1. A. Wait for three atropine doses before taking further action (Why this does not fit)

    Persistent severe hypoperfusion does not justify waiting to reach a medication maximum.

  2. B. Give an AV nodal calcium-channel blocker (Why this does not fit)

    Further conduction suppression can worsen the already slow ventricular response.

  3. C. Continuous monitoring alone because escape complexes are present (Why this does not fit)

    An escape rhythm is maintaining electrical activation but is not providing adequate organ perfusion at this rate.

  4. D. Initiate transcutaneous pacing while arranging expert and transvenous support (Best answer)

    An unreliable broad escape with shock requires escalation; electrical and mechanical capture must be checked.

Takeaway: Atropine failure with shock requires escalation without a mandatory dosing delay.

Case sources: [2] [3]

Case 16

A 67-year-old woman with symptomatic post-infarct bradycardia has no response to atropine. External pacing does not achieve capture despite troubleshooting, and a transvenous team is en route. Which pharmacological bridge is supported by the adult algorithm?

Show answer and explanations for case 16

  1. A. Dobutamine infusion as the algorithm-listed chronotropic bridge (Why this does not fit)

    Dobutamine may support contractility in selected low-output states, but it is not the dopamine or epinephrine bridge specified in the AHA adult bradycardia algorithm.

  2. B. Norepinephrine infusion as the algorithm-listed chronotropic bridge (Why this does not fit)

    Norepinephrine can support blood pressure in shock, but it is not the rate-accelerating infusion listed for this bradycardia branch.

  3. C. Dopamine or epinephrine infusion titrated to response (Best answer)

    These adrenergic infusions are algorithm-supported bridges after ineffective atropine, with ongoing pacing arrangements.

  4. D. Isoproterenol infusion as the algorithm-listed post-MI bridge (Why this does not fit)

    Isoproterenol can increase rate in selected settings, but it is not the AHA algorithm choice here and can worsen myocardial ischemia.

Takeaway: The algorithm allows adrenergic support as well as pacing after atropine fails.

Case sources: [3] [12]

Case 17

A 70-year-old man required temporary pacing during an inferior infarct. After PCI, one-to-one conduction returns with PR 180 ms and remains stable during observation. No prior syncope or conduction disease is documented. What is the best conclusion about permanent pacing?

Show answer and explanations for case 17

  1. A. Temporary pacing automatically mandates a permanent device (Why this does not fit)

    Temporary support during a reversible ischemic episode is not itself a permanent pacing indication.

  2. B. Reassess for a persistent indication rather than implant automatically (Best answer)

    Recovered conduction after reperfusion supports observation and individualized assessment.

  3. C. A permanent device should be implanted solely because the infarct was inferior (Why this does not fit)

    Infarct location does not substitute for persistent conduction disease.

  4. D. Follow-up is unnecessary because recurrence is impossible (Why this does not fit)

    Recovery is reassuring but does not guarantee that no future conduction issue can occur.

Takeaway: Reversible post-MI block and permanent conduction disease require different decisions.

Case sources: [2]

Case 19

A 59-year-old man with RV infarction has BP 88/56 mm Hg after vomiting repeatedly. Echo shows RV hypokinesis, no pericardial effusion, and no severe LV dysfunction. There are no lung B-lines. Which volume strategy is most appropriate alongside reperfusion?

Show answer and explanations for case 19

  1. A. An unlimited saline infusion until JVP normalizes (Why this does not fit)

    JVP may remain high from RV dysfunction, and unlimited fluid can worsen distension and output.

  2. B. Avoid all hemodynamic treatment until angiography is complete (Why this does not fit)

    Supportive care and reperfusion planning should occur together.

  3. C. Immediate aggressive diuresis based only on RV dysfunction (Why this does not fit)

    The patient has hypotension and potential underfilling without demonstrated pulmonary congestion.

  4. D. A small crystalloid challenge followed by reassessment of perfusion and congestion (Best answer)

    Possible underfilling and absent pulmonary congestion support a monitored trial rather than a fixed large volume.

Takeaway: Use a fluid challenge as an assessed intervention, not as an automatic large-volume prescription.

Case sources: [4] [8]

Case 20

A 74-year-old woman with RV infarction receives several fluid boluses. JVP rises, bilateral B-lines and crackles appear, oxygen saturation falls to 87%, and BP remains 82/48 mm Hg. What is the best next approach?

Show answer and explanations for case 20

  1. A. Continue identical boluses because RV infarction always improves with volume (Why this does not fit)

    The treatment is now associated with congestion and no perfusion benefit.

  2. B. Conclude that the RV has fully recovered (Why this does not fit)

    Congestion does not establish RV recovery; combined LV disease or excessive filling may be present.

  3. C. Stop automatic fluid loading and reassess both ventricles, valves, and support needs (Best answer)

    New congestion and persistent shock require a new hemodynamic assessment and consideration of vasoactive support.

  4. D. Give sublingual nitroglycerin despite hypotension (Why this does not fit)

    The low pressure and RV involvement make an unmonitored preload reduction unsafe.

Takeaway: Loss of fluid responsiveness and new congestion should change management.

Case sources: [1] [4] [8]

Case 21

A 62-year-old man with inferior STEMI and V4R ST elevation has ongoing chest pressure and BP 80/46 mm Hg. Which prescribed intervention should be withheld because it can further reduce venous return?

Show answer and explanations for case 21

  1. A. Chewed aspirin without an allergy or bleeding contraindication (Why this does not fit)

    Aspirin addresses platelet activation and is not withheld for its effect on venous return.

  2. B. Sublingual nitroglycerin (Best answer)

    Nitrates can worsen hypotension through venodilation and are avoided in suspected RV infarction.

  3. C. Reperfusion activation (Why this does not fit)

    Restoring coronary flow addresses the cause of the infarct and should not be withheld.

  4. D. Continuous ECG monitoring (Why this does not fit)

    Monitoring does not reduce preload and is needed for associated arrhythmias.

Takeaway: Hypotension and suspected RV infarction are reasons to avoid nitrates.

Case sources: [1]

Case 22

A 76-year-old woman with inferior STEMI has Mobitz I block, a ventricular rate of 42/min, and BP 90/54 mm Hg. Which medication order should be held pending stabilization?

Show answer and explanations for case 22

  1. A. Metoprolol (Best answer)

    Further slowing of sinus and AV nodal activity can aggravate her bradycardia, block, and low pressure.

  2. B. Aspirin (Why this does not fit)

    No bleeding or allergy is given, and aspirin does not cause AV nodal blockade.

  3. C. A statin (Why this does not fit)

    Lipid-lowering therapy is not an AV nodal suppressant.

  4. D. Strategy-appropriate anticoagulation (Why this does not fit)

    Anticoagulation does not worsen AV conduction through nodal suppression, although bleeding risk still requires assessment.

Takeaway: Post-MI benefit does not override acute contraindications to beta-blockade.

Case sources: [1] [2]

Case 23

A 56-year-old man with inferior STEMI arrives 90 minutes after symptom onset. He is at a PCI-capable center with an available team. BP is 120/72 mm Hg. Which strategy best addresses the coronary occlusion?

Show answer and explanations for case 23

  1. A. Observe for a troponin peak before intervention (Why this does not fit)

    A clear acute STEMI does not require waiting for a biomarker peak.

  2. B. Use aspirin and heparin as the sole reperfusion treatment (Why this does not fit)

    These limit thrombosis but do not replace definitive reperfusion.

  3. C. Schedule an exercise stress test (Why this does not fit)

    Stress testing is inappropriate during an active STEMI requiring reperfusion.

  4. D. Activate primary PCI with indicated initial therapy (Best answer)

    Timely primary PCI is preferred in this available-capability setting.

Takeaway: Treat a clear STEMI through the emergency reperfusion pathway.

Case sources: [1]

Case 24

A 60-year-old woman has 2 hours of inferior STEMI symptoms at a non-PCI hospital. Expected first-medical-contact-to-device time is 165 minutes. BP is 128/76 mm Hg; careful review finds no fibrinolysis contraindication. What is the preferred strategy among these choices?

Show answer and explanations for case 24

  1. A. Anticoagulation alone until the following week (Why this does not fit)

    This leaves the occluded coronary artery without an appropriate reperfusion strategy.

  2. B. Fibrinolysis followed by transfer to a PCI-capable center only if pain returns (Why this does not fit)

    All patients receiving fibrinolysis should be transferred, including those with initial apparent success.

  3. C. Fibrinolysis followed by immediate transfer to a PCI-capable center (Best answer)

    Within the early symptom window, excessive PCI delay and no contraindication support a pharmacoinvasive strategy.

  4. D. Wait locally until 12 hours have elapsed (Why this does not fit)

    The 12-hour interval is not a waiting requirement and delay reduces potential benefit.

Takeaway: Successful lysis does not eliminate the need for transfer and angiography.

Case sources: [1]

Case 25

A 68-year-old man presents within 3 hours of inferior STEMI at a remote facility. PCI transfer is being arranged. Which history is an absolute contraindication to STEMI fibrinolysis?

Show answer and explanations for case 25

  1. A. Daily low-dose aspirin use (Why this does not fit)

    Aspirin is commonly part of the accompanying antithrombotic regimen.

  2. B. Intracranial hemorrhage eight years earlier (Best answer)

    Any prior intracranial hemorrhage is an absolute contraindication; it is not limited to the preceding three months.

  3. C. A healed duodenal ulcer ten years earlier without current bleeding (Why this does not fit)

    Remote healed ulcer disease is different from active bleeding or an active ulcer.

  4. D. Age 68 years alone (Why this does not fit)

    Age affects risk assessment but is not by itself an absolute contraindication.

Takeaway: Remote intracranial hemorrhage still changes the reperfusion decision.

Case sources: [1]

Case 26

A 54-year-old woman reports substantial relief after fibrinolysis for inferior STEMI. ST elevation has largely resolved, BP is 122/70 mm Hg, and no arrhythmia is present. Which plan is appropriate?

Show answer and explanations for case 26

  1. A. Transfer and plan early angiography, generally within 2 to 24 hours (Best answer)

    This is the pharmacoinvasive pathway for apparent successful fibrinolysis.

  2. B. Give another fibrinolytic dose routinely (Why this does not fit)

    Repeat lysis is not the routine response to successful initial treatment.

  3. C. Cancel transfer because reperfusion appears successful (Why this does not fit)

    Early success does not remove the risk of residual stenosis or reocclusion.

  4. D. Delay coronary evaluation until symptoms recur months later (Why this does not fit)

    Deferring evaluation misses the recommended early invasive assessment.

Takeaway: Rescue PCI is for failed lysis; early angiography also follows successful lysis.

Case sources: [1]

Case 27

A 63-year-old man undergoing RCA intervention has no contrast passage beyond the lesion before PCI and normal distal epicardial filling afterward. The report records TIMI 0 then TIMI 3. What do these grades describe?

Show answer and explanations for case 27

  1. A. Absence then complete restoration of collateral vessels (Why this does not fit)

    The scale describes antegrade flow in the imaged artery, not collateral development.

  2. B. Absent then normal LV ejection fraction (Why this does not fit)

    TIMI flow grades are not ventricular ejection fraction measurements.

  3. C. The amount of irreversible myocardial scar (Why this does not fit)

    Flow at angiography does not directly quantify established scar.

  4. D. Absent then normal antegrade epicardial coronary flow (Best answer)

    TIMI flow describes contrast passage through the epicardial artery; collateral and tissue-level perfusion are separate assessments.

Takeaway: An open epicardial artery does not by itself prove intact microvascular perfusion.

Case sources: [9]

Case 28

Four days after an inferior MI, a 77-year-old woman develops pulmonary edema and BP 78/46 mm Hg. The apical systolic sound is faint. Echo shows a ruptured posteromedial papillary muscle and severe eccentric MR. Which interpretation is correct?

Show answer and explanations for case 28

  1. A. The faint murmur excludes severe MR (Why this does not fit)

    Acute pressure equalization and low forward output can make severe MR surprisingly quiet.

  2. B. The named muscle is part of the tricuspid valve (Why this does not fit)

    This transfers mitral anatomy to the wrong valve.

  3. C. The lesion involves the mitral supporting apparatus and requires urgent surgical evaluation (Best answer)

    The posteromedial LV papillary muscle supports the mitral valve; structural rupture is not corrected by diuresis alone.

  4. D. The patient must have a normal cardiac output because LV ejection fraction may be preserved (Why this does not fit)

    Ejection into the low-pressure left atrium can preserve measured EF while systemic forward flow is poor.

Takeaway: Severe acute MR may have a soft murmur and a deceptively preserved EF.

Case sources: [5]

Case 29

A 69-year-old man becomes dyspneic three days after inferior MI. A new holosystolic murmur is heard at the left sternal border. Doppler shows flow from LV to RV, and oxygen saturation rises from 63% in the RA to 81% in the RV. Which complication is present?

Show answer and explanations for case 29

  1. A. Functional tricuspid regurgitation (Why this does not fit)

    TR sends RV blood backward to the RA and does not create the demonstrated oxygenated LV-to-RV shunt.

  2. B. Ventricular septal rupture (Best answer)

    The Doppler defect and RA-to-RV oxygen step-up establish a ventricular-level left-to-right shunt.

  3. C. Papillary muscle rupture with MR (Why this does not fit)

    MR sends blood to the LA rather than through the septum into the RV.

  4. D. Free wall rupture into the pericardium (Why this does not fit)

    The imaged flow remains between ventricular chambers rather than entering the pericardial space.

Takeaway: Shunt direction is more decisive than murmur location alone.

Case sources: [5]

Case 31

A 70-year-old man has persistent inferior ST elevation 48 hours after PCI. He is pain-free and troponin is falling, but no follow-up echo has been obtained. What can be concluded from these data alone?

Show answer and explanations for case 31

  1. A. A true ventricular aneurysm is proven (Why this does not fit)

    An aneurysm requires structural assessment; persistent ST elevation at this stage is insufficient.

  2. B. The stent is certainly patent (Why this does not fit)

    Symptoms and biomarkers alone do not demonstrate stent patency or exclude silent ischemia.

  3. C. No additional assessment could be useful (Why this does not fit)

    The persistent abnormality cannot be explained confidently from the limited data provided.

  4. D. Clinical and ECG comparison with ventricular imaging is needed before assigning a cause (Best answer)

    Residual injury, tissue perfusion problems, and structural complications require assessment rather than an automatic label.

Takeaway: Do not use absence of pain and falling troponin as proof of a specific structural diagnosis.

Case sources: [1] [5]

Case 32

A 59-year-old woman notices palpitations two hours after RCA PCI. BP is 118/72 mm Hg. ECG shows narrow QRS complexes at irregular intervals, no discrete P waves, and an irregular fibrillatory baseline without organized flutter waves. Which rhythm best fits?

Show answer and explanations for case 32

  1. A. Typical atrial flutter with fixed 2-to-1 conduction (Why this does not fit)

    Fixed flutter conduction would be regular and would have organized atrial flutter activity.

  2. B. Sinus tachycardia (Why this does not fit)

    Sinus tachycardia has discrete sinus P waves with an organized relationship to QRS complexes.

  3. C. Atrial fibrillation (Best answer)

    The absence of organized atrial activity with an irregularly irregular ventricular response supports AF.

  4. D. Complete AV block with a regular escape (Why this does not fit)

    A regular independent escape would not explain this irregularly irregular ventricular pattern.

Takeaway: Reassess the actual rhythm rather than assigning every post-inferior-MI arrhythmia to AV block.

Case sources: [3]

Case 33

A 73-year-old woman develops new dyspnea and hypotension six days after inferior MI. Echo shows an inferolateral wall defect communicating with a narrow-necked sac bounded by pericardium and thrombus. What is the best interpretation?

Show answer and explanations for case 33

  1. A. A true LV aneurysm suitable for routine follow-up only (Why this does not fit)

    An intact scarred myocardial wall is required for a true aneurysm; wall discontinuity is demonstrated here.

  2. B. A pseudoaneurysm requiring urgent surgical evaluation (Best answer)

    The pericardium contains a free wall rupture, which may fail and cause further bleeding.

  3. C. An inflammatory effusion without ventricular communication (Why this does not fit)

    Doppler demonstrates a communication with the LV, not merely fluid surrounding an intact wall.

  4. D. An isolated ventricular septal rupture (Why this does not fit)

    The communication crosses the free wall into a sac, rather than the septum into the RV.

Takeaway: A communicating sac outside disrupted myocardium is a contained rupture.

Case sources: [5]

Case 34

A 58-year-old man with inferior MI develops symptomatic sinus bradycardia. After atropine 1 mg IV, his rate rises from 38 to 64/min. PCI is still being arranged. Which mechanism explains the rate response?

Show answer and explanations for case 34

  1. A. Muscarinic blockade relieves parasympathetic suppression (Best answer)

    Atropine opposes vagal effects on nodal tissue; the coronary obstruction still needs reperfusion.

  2. B. Direct stimulation of cardiac beta-1 adrenergic receptors (Why this does not fit)

    That is an adrenergic mechanism, whereas atropine is an antimuscarinic agent.

  3. C. Fibrin breakdown restores coronary flow (Why this does not fit)

    Atropine is not a fibrinolytic, so the rate response does not prove reperfusion.

  4. D. Increased AV nodal calcium-channel blockade (Why this does not fit)

    Further calcium-channel suppression would slow nodal conduction rather than explain the rate increase.

Takeaway: An atropine response supports a vagal contribution without proving restored coronary flow.

Case sources: [2] [3]

Sources

  1. 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the Management of Patients With Acute Coronary Syndromes (2025)

    ECG extensions, oxygen, antithrombotics, nitrate and opioid precautions, PCI and fibrinolysis selection, contraindications, post-lysis transfer and reassessment. Live-checked guideline sections and tables 6 and 14.

  2. 2018 ACC/AHA/HRS Guideline on Bradycardia and Cardiac Conduction Delay (2018)

    AV block definitions, nodal versus infranodal disease, temporary support, reversible post-MI block and permanent pacing observation.

  3. 2025 AHA Adult Advanced Life Support (2025)

    Adult symptomatic bradycardia, atropine 1 mg and 3 mg maximum, pacing and adrenergic infusions, capture confirmation, rhythm discrimination.

  4. AHA Scientific Statement on Evaluation and Management of Right-Sided Heart Failure (2018)

    RV physiology, volume assessment, ventricular interdependence, functional TR and circulatory support.

  5. AHA Scientific Statement on Mechanical Complications of Acute Myocardial Infarction (2021)

    Papillary muscle blood supply, quiet acute MR, septal and free wall rupture, pseudoaneurysm and structural reassessment. Publisher and PMC direct fetches were blocked; live indexed full-text passages were read.

  6. 2021 AHA/ACC Guideline for Evaluation and Diagnosis of Chest Pain (2021)

    Upper abdominal symptoms as anginal equivalents and avoidance of sex-based symptom exclusions.

  7. The early recognition of right ventricular infarction. Diagnostic accuracy of the electrocardiographic V4R lead (1983)

    Primary diagnostic study supporting early V4R recording and its imperfect sensitivity and specificity.

  8. Hemodynamics of volume loading compared with dobutamine in severe right ventricular infarction (1994)

    Small randomized crossover physiological study showing increased filling pressures without increased output after volume loading; limits of universal fluid rules.

  9. T-TIME three-arm RCT: Appendix 3, Supplementary methods (2020)

    Trial report definitions of TIMI flow and distinction between epicardial flow and microvascular reperfusion.

  10. Anatomical aspects of the arterial blood supply to the sinoatrial and atrioventricular nodes of the human heart (2008)

    Primary anatomical study of variable nodal arterial origins and relationship of AV nodal supply to dominance.

  11. Elevation of ST segment and Bezold Jarisch reflex as evidence of early post-thrombolysis reperfusion (1992)

    Primary case report supporting the occurrence of bradycardia and hypotension during inferior infarct reperfusion; not used to infer universal incidence or diagnostic certainty.

  12. 2025 AHA Adult Bradycardia With a Pulse Algorithm (2025)

    Official one-page algorithm specifying atropine dose and maximum, dopamine and epinephrine infusions, pacing and escalation.

  13. Origin of the sinoatrial node and atrioventricular node arteries in right, mixed, and left inferior emphasis systems (1975)

    Primary angiographic study documenting variable and dual nodal arterial origins. Used for the existence of dual SA supply, not a universal prevalence estimate.

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