In an elderly woman with diabetes, hypertension, and prior ischemic heart disease who presents with worsening orthopnea, normal vital signs, ECG showing ST‑elevation in leads II, III, aVF, V5, V6, and chest X‑ray showing pulmonary edema, what is the cause of her shortness of breath?

Acute Coronary Syndrome (Acute Myocardial Infarction) is the Cause

This patient is experiencing an acute inferior-lateral ST-elevation myocardial infarction (STEMI) that has precipitated acute decompensated heart failure with pulmonary edema. The ST-elevations in leads II, III, aVF, V5, and V6 represent acute myocardial injury requiring immediate reperfusion therapy, and the pulmonary edema is a consequence of this acute cardiac event 1.

Why This is Acute Coronary Disease (Answer A)

The question asks for the cause of her complaint, not merely a description of her symptoms. While pulmonary edema and decompensated heart failure are present, they are consequences of the underlying acute coronary syndrome, not the root cause 1.

• ST-elevation on ECG is pathognomonic for acute myocardial infarction requiring immediate reperfusion therapy (primary PCI within 90 minutes or fibrinolytic therapy) 1
• The distribution (inferior leads II, III, aVF plus lateral leads V5, V6) indicates an extensive acute MI involving the inferior and lateral walls 1
• Acute MI is the most common precipitating factor for acute pulmonary edema, present in 15-25% of cases presenting with pulmonary edema 2, 3
• The European Society of Cardiology explicitly states that acute myocardial infarction during hospital stay is a predictor of increased mortality (p<0.001) in patients presenting with pulmonary edema 3

Why the Other Answers Are Incorrect

Pulmonary edema (Answer B) is a clinical manifestation visible on chest X-ray, not the underlying cause. It describes what is happening in the lungs but does not explain why it is happening 1.

Decompensated heart failure (Answer D) is also a consequence rather than the primary cause. The European Society of Cardiology classifies this presentation as acute heart failure precipitated by an underlying event 1. In this case, the acute MI is the precipitating event causing the decompensation 1.

Pulmonary embolism (Answer C) would not produce ST-elevations in this distribution and is inconsistent with the ECG findings 1.

Clinical Reasoning Framework

The European Society of Cardiology provides clear guidance on distinguishing the precipitating cause from the clinical syndrome 1:

1. Identify the acute precipitant: ST-elevation MI is present on ECG 1
2. Recognize the hemodynamic consequence: Acute MI has caused left ventricular dysfunction leading to pulmonary congestion 1
3. Classify the severity: This represents Killip class 3 (rales over >50% of lung fields) complicating acute MI 1

Critical Management Implications

Identifying acute coronary syndrome as the cause fundamentally changes management:

• Immediate reperfusion therapy is mandatory (primary PCI preferred, or fibrinolytic therapy if PCI cannot be performed within 90 minutes) 1
• Aspirin 150-325 mg chewable should be administered immediately 1
• Anticoagulation with weight-adjusted heparin is required 1
• Pulmonary edema management (oxygen, vasodilators, diuretics) is adjunctive to reperfusion therapy, not the primary treatment 1

Common Pitfall to Avoid

Never assume dyspnea without chest pain is non-cardiac—this assumption leads to underdiagnosis and increased mortality, particularly in women with diabetes 4. Up to 25% of acute MIs present without chest pain, especially in elderly patients, women, and diabetics 4. The absence of chest pain in this patient with clear ECG evidence of STEMI should not delay recognition of acute coronary syndrome as the primary diagnosis.

The European Society of Cardiology emphasizes that acute myocardial infarction is associated with the highest in-hospital mortality (p<0.001) among all precipitants of pulmonary edema, making rapid identification and treatment essential 3.