A 50-year-old man presents to the emergency department with acute-onset
substernal chest pain, diaphoresis, and vomiting for the past 30 minutes. He
has a history of hypertension, diabetes mellitus, and hyperlipidemia, is
nonadherent to medications, and is an active smoker. On examination, blood
pressure is 90/60 mmHg, pulse rate is 58 beats/min, and respiratory rate is 18
breaths/min. Jugular venous pressure is elevated. Electrocardiography shows
sinus bradycardia with ST-segment elevation in leads II, III, and aVF, with
reciprocal ST depression in leads I and aVL. Cardiac troponin is elevated,
although reperfusion therapy should not be delayed while awaiting biomarker
results. Echocardiography shows inferior wall hypokinesis. Diagnosis?
Diagnosis is acute inferior wall ST-segment elevation myocardial
infarction, with suspected right ventricular infarction, most likely from right
coronary artery occlusion.
The combination of inferior ST-segment elevation, hypotension,
elevated JVP, and bradycardia strongly suggests associated right
ventricular involvement, typically from a proximal RCA culprit lesion.
1. Definition
An inferior STEMI is an acute myocardial infarction involving the inferior
myocardium, characterized by persistent ST-segment elevation in the inferior
ECG leads in the appropriate ischemic clinical setting.
The culprit vessel is most commonly:
1. Right
coronary artery, especially in right-dominant circulation
2. Left
circumflex artery less commonly, particularly with left-dominant anatomy
Proximal RCA occlusion can additionally involve:
1. Right
ventricle
2. SA
node
3. AV
node
2. Risk Factors
Major atherosclerotic risk factors include:
1. Smoking
2. Hypertension
3. Diabetes
mellitus
4. Dyslipidemia
5. Older
age
6. Family
history of premature atherosclerotic cardiovascular disease
7. Obesity
and physical inactivity
This patient has several major modifiable risk factors.
3. Pathophysiology
1. Acute
coronary syndrome most commonly begins with atherosclerotic plaque
disruption or erosion.
2. Platelet
activation and thrombus formation can produce acute coronary artery occlusion.
3. Persistent
coronary occlusion causes:
1.
Myocardial ischemia
2.
Loss of contractility
3.
Cardiomyocyte necrosis
4. Inferior
MI commonly involves the RCA.
5. A
sufficiently proximal RCA occlusion may compromise right ventricular perfusion
and cause RV ischemic dysfunction.
6. Reduced
RV output decreases LV preload, causing:
1.
Reduced cardiac output
2.
Hypotension
3.
Elevated right-sided filling pressures
4. Bradycardia and Conduction Abnormalities
Inferior STEMI commonly produces bradyarrhythmias because of:
1. Increased
vagal tone
2. Ischemia
of the SA or AV nodal circulation
3. The
Bezold-Jarisch reflex
The Bezold-Jarisch reflex may produce:
1. Bradycardia
2. Hypotension
3. Peripheral
vasodilation
Conduction disturbances may include:
1. Sinus
bradycardia
2. First-degree
AV block
3. Mobitz
type I AV block
4. High-grade
or complete AV block
AV block associated with inferior MI is often transient, particularly after
successful reperfusion.
5. Clinical Features
Typical manifestations include:
1. Acute
substernal chest pain or pressure
2. Diaphoresis
3. Nausea
and vomiting
4. Dyspnea
5. Weakness
or presyncope
Features suggesting associated RV infarction include:
1. Hypotension
2. Elevated
JVP
3. Relatively
clear lungs when isolated RV failure predominates
4. Bradycardia
or AV block
5. Inferior
STEMI pattern on ECG
The classic hemodynamic pattern is hypotension + elevated JVP +
clear lung fields.
6. ECG Findings
Typical inferior STEMI findings include:
1. ST-segment
elevation in leads II, III, and aVF
2. Reciprocal
ST-segment depression in leads I and aVL
Additional clues include:
1. ST
elevation in lead III greater than lead II favors RCA rather than LCx
involvement, although it is not definitive.
2. Right-sided
ECG leads should be obtained when inferior STEMI is present, especially when RV
involvement is suspected.
3. ST-segment
elevation in the right precordial leads, especially V4R, supports right
ventricular infarction.
4. V3R
to V6R may provide additional evidence of RV involvement.
In this patient, the combination of hypotension and elevated JVP makes a right-sided
ECG essential.
7. Diagnostic Evaluation
7.1 ECG
1. Obtain
a 12-lead ECG as rapidly as possible in suspected ACS.
2. STEMI
is fundamentally an ECG-based emergency diagnosis in the
appropriate clinical setting.
3. Obtain
right-sided leads, particularly V4R, when RV infarction is
suspected.
4. Repeat
ECGs if symptoms evolve or the initial ECG is nondiagnostic.
7.2 Cardiac Troponin
1. High-sensitivity
cardiac troponin is the preferred biomarker of myocardial injury.
2. Elevated
troponin indicates myocardial injury. A rise and/or fall in troponin with
clinical evidence of acute myocardial ischemia establishes acute myocardial
infarction.
3. Reperfusion
therapy should not be delayed while awaiting troponin results when the ECG and
clinical presentation establish STEMI.
7.3 Echocardiography
Echocardiography can identify:
1. Inferior
wall motion abnormalities
2. RV
dilation or hypokinesis
3. LV
systolic function
4. Mechanical
complications
5. Other
causes of hemodynamic instability
Echocardiography should not delay emergency reperfusion.
7.4 Coronary Angiography
Emergency coronary angiography:
1. Identifies
the culprit artery
2. Defines
coronary anatomy
3. Allows
immediate primary PCI
8. Immediate Management
Management priorities are:
1. Immediate
reperfusion
2. Antiplatelet
therapy
3. Anticoagulation
4. Hemodynamic
stabilization
5. Treatment
of bradyarrhythmias
6. Secondary
prevention
8.1 Reperfusion
Primary PCI is the preferred reperfusion strategy.
1. Goal
first-medical-contact to device time is ≤90 minutes for
patients presenting directly to a PCI-capable center.
2. Goal
first-medical-contact to device time is ≤120 minutes when
transfer from a non-PCI-capable hospital is required.
3. Reperfusion
should occur as rapidly as possible because myocardial salvage decreases with
treatment delay.
4. Radial
arterial access is generally preferred for PCI when feasible because it reduces
bleeding and vascular complications.
8.2 Fibrinolysis
If anticipated first-medical-contact to device time will exceed 120
minutes:
1. Fibrinolysis
should be administered in eligible patients presenting within 12 hours of
symptom onset, provided there are no contraindications.
2. A
fibrin-specific agent such as tenecteplase is preferred when available.
3. The
patient should then be transferred promptly to a PCI-capable center.
After fibrinolysis:
1. Rescue
PCI is required when reperfusion fails or when there is persistent
ischemia, hemodynamic instability, electrical instability, or inadequate
ST-segment resolution.
2. In
inferior STEMI, <70% ST-segment resolution in the inferior leads at
approximately 60 to 90 minutes supports failed or inadequate
reperfusion and should prompt urgent rescue PCI.
3. After
successful fibrinolysis, routine coronary angiography is generally performed
within 2 to 24 hours as part of a pharmaco-invasive strategy.
This patient presented only 30 minutes after symptom onset,
so reperfusion should be initiated immediately.
9. Antithrombotic Therapy
9.1 Aspirin
Give:
Aspirin 162 to 325 mg orally, preferably chewed, as soon as
possible.
Long-term maintenance is typically low-dose aspirin.
9.2 P2Y12 Inhibitor
For STEMI treated with primary PCI:
1. Ticagrelor
or prasugrel is generally preferred over clopidogrel.
2. Clopidogrel
is used when the preferred agents are unavailable, contraindicated, or not
tolerated.
3. Prasugrel
should not be used in patients with previous stroke or TIA.
For STEMI treated with fibrinolysis:
Clopidogrel is the standard P2Y12 inhibitor used with
aspirin.
9.3 Anticoagulation
Anticoagulation is required as part of the reperfusion strategy.
Options include:
1. Unfractionated
heparin
2. Enoxaparin
3. Bivalirudin
in selected PCI patients
The specific agent depends on the reperfusion strategy, bleeding risk, renal
function, and local protocol.
10. Management of Suspected Right Ventricular Infarction
The key physiological problem is inadequate LV filling caused by reduced RV
output.
10.1 Preload
1. Carefully
optimize preload.
2. A
small IV crystalloid challenge may be appropriate if hypotension is present
without pulmonary congestion and clinical assessment suggests inadequate
preload.
3. Reassess
blood pressure, JVP, lung examination, oxygenation, and perfusion after any
fluid administration.
4. Avoid
indiscriminate fluid loading, particularly when JVP is already
markedly elevated, because RV overdistension can worsen interventricular
interaction and reduce cardiac output.
10.2 Avoid Preload-Reducing Drugs
In this patient, avoid:
1. Nitroglycerin
2. Other
venodilators
3. Routine
diuretics in the absence of congestion
Avoid nitroglycerin because RV infarction is suspected and the
patient is borderline hypotensive with SBP 90 mmHg.
Nitrates may markedly reduce preload and precipitate severe hypotension in
RV infarction.
10.3 Persistent Hypotension
If hypotension persists despite careful preload optimization and correction
of rhythm disturbances:
1. Vasopressor
support may be necessary.
2. Norepinephrine
is commonly favored when significant hypotension or shock requires vasopressor
support.
3. An
inotrope such as dobutamine may be considered when low cardiac output persists
after adequate perfusion pressure has been established.
4. Severe
refractory RV shock may require mechanical circulatory support.
The definitive treatment remains rapid coronary reperfusion.
11. Bradycardia and AV Block
For clinically significant bradycardia:
1. Atropine
may be given when bradycardia is causing hypotension or other evidence of poor
perfusion.
2. Temporary
pacing may be necessary for:
1.
Persistent symptomatic bradycardia
2.
High-grade AV block
3.
Complete heart block with hemodynamic compromise
Maintaining adequate heart rate and AV synchrony is
particularly important in RV infarction because RV filling is highly dependent
on atrial contraction.
12. Other Acute Medical Therapy
12.1 Oxygen
1. Give
supplemental oxygen when oxygen saturation is <90% or
clinically significant hypoxemia is present.
2. Routine
oxygen is not recommended when oxygen saturation is ≥90%.
12.2 Analgesia
1. Rapid
reperfusion is the most important treatment for ongoing ischemic pain.
2. Opioids
may be considered for severe pain refractory to other appropriate treatment,
but they should be used cautiously because they can worsen hypotension and delay
absorption of oral P2Y12 inhibitors.
12.3 Beta-Blockers
Early oral beta-blocker therapy is appropriate for many patients with ACS
when no contraindication exists.
Beta-blockers should be withheld initially in this patient
because he has:
1. Heart
rate of 58 beats/min
2. Hypotension
3. Suspected
RV hemodynamic compromise
Beta-blocker therapy can be reconsidered after stabilization.
12.4 ACE Inhibitor or ARB
ACE inhibitor or ARB therapy is indicated after ACS in appropriate high-risk
patients, particularly those with:
1. LVEF
≤40%
2. Heart
failure
3. Hypertension
4. Diabetes
mellitus
5. Anterior
STEMI
In this patient, initiation should wait until blood pressure and
hemodynamics have stabilized.
12.5 Lipid-Lowering Therapy
Start high-intensity statin therapy as early as possible
unless contraindicated.
Additional lipid-lowering therapy should be added when LDL cholesterol
remains above recommended secondary-prevention thresholds despite maximally
tolerated statin therapy.
13. Secondary Prevention
Long-term management includes:
1. Dual
antiplatelet therapy for at least 12 months by default in ACS patients who are
not at high bleeding risk, with individualized shorter or modified
antiplatelet strategies when bleeding risk or other clinical factors warrant
2. High-intensity
lipid-lowering therapy
3. Smoking
cessation
4. Blood-pressure
control
5. Diabetes
management
6. Medication-adherence
counseling
7. Regular
physical activity after stabilization
8. Dietary
modification
9. Cardiac
rehabilitation
14. Complications
Important complications include:
1. Sinus
bradycardia
2. AV
block
3. Right
ventricular failure
4. Cardiogenic
shock
5. Ventricular
tachycardia
6. Ventricular
fibrillation
7. Recurrent
ischemia or reinfarction
8. Acute
mitral regurgitation from papillary muscle dysfunction or rupture
9. Ventricular
septal rupture
10. Free-wall
rupture
11. Pericarditis
15. Prognosis
1. Prognosis
depends strongly on infarct size, reperfusion delay, ventricular function,
arrhythmias, and hemodynamic complications.
2. Inferior
STEMI without major complications often has a relatively favorable short-term
course after successful reperfusion.
3. Right
ventricular involvement, hypotension, cardiogenic shock, and high-grade AV
block substantially increase acute risk.
4. Early
reperfusion significantly improves outcomes and facilitates recovery of RV
function.
16. Key Clinical Insight
Inferior STEMI + hypotension + elevated JVP + bradycardia should
immediately raise suspicion for right ventricular infarction.
For this patient:
ST elevation in II, III, and aVF + reciprocal depression in I and
aVL = inferior STEMI.
Hypotension + elevated JVP + bradycardia = suspected RV involvement,
usually from proximal RCA occlusion.
Obtain right-sided leads, especially V4R, avoid nitrates,
carefully optimize preload, treat significant bradyarrhythmias, and proceed to immediate
reperfusion.
References
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SV, O'Donoghue ML, Ruel M, et al. 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for
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RA, Rossello X, Coughlan JJ, et al. 2023 ESC Guidelines for the management of
acute coronary syndromes. Eur Heart J. 2023;44(38):3720-3826.
doi:10.1093/eurheartj/ehad191.
3. Goldstein
JA, Lerakis S, Moreno PR. Right Ventricular Myocardial Infarction: A Tale of
Two Ventricles: JACC Focus Seminar 1/5. J Am Coll Cardiol.
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4. Mills
NL, Newby LK, Zaman S, et al. Fifth Universal Definition of Myocardial
Infarction (2026). J Am Coll Cardiol. 2026;88(11):1314-1368.
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