What if breathlessness is due to an underlying cardiac etiology?

Cardiac Causes of Breathlessness: Diagnostic and Management Approach

When breathlessness is suspected to be cardiac in origin, transthoracic echocardiography should be performed immediately to assess cardiac structure and function, as this is the key diagnostic tool for identifying heart failure, valvular disease, and ventricular dysfunction. 1

Initial Clinical Assessment

The clinical presentation provides critical clues to cardiac etiology:

• Orthopnea and paroxysmal nocturnal dyspnea are highly suggestive of cardiac causes and should be specifically elicited during history-taking 2
• Tachycardia, tachypnea, and basal rales extending throughout lung fields indicate pulmonary congestion from cardiac dysfunction 1
• A third heart sound (S3) is a key physical finding that suggests heart failure 1
• However, physical examination alone has poor sensitivity for detecting cardiac dysfunction, and symptoms correlate poorly with the severity of cardiac impairment 1

Immediate Diagnostic Priorities

Vital Signs and Oxygen Assessment

• Measure oxygen saturation by pulse oximetry in all breathless patients as the "fifth vital sign" 3, 4
• Check vital signs including respiratory rate, pulse rate, blood pressure, and temperature using a track-and-trigger system like NEWS 4
• For patients at risk of hypercapnic respiratory failure, target oxygen saturation of 88-92% rather than 94-98% 3

Electrocardiography

• Obtain an ECG within 10 minutes of presentation to distinguish between STEMI and non-ST-segment elevation acute coronary syndromes 5
• If symptoms are episodic, capture an ECG during symptomatic episodes to diagnose conditions like vasospastic angina, which shows transient ST-segment elevation 2

Cardiac Biomarkers

• Measure high-sensitivity cardiac troponin to exclude Type 2 myocardial infarction from supply-demand mismatch 2
• Check BNP or NT-proBNP levels, as elevated levels warrant echocardiography even without classic heart failure symptoms 2, 6

Imaging Strategy

First-Line Imaging

• Chest radiography should be performed promptly to assess for pulmonary congestion, cardiomegaly, and interstitial edema, though it has high specificity (96%) but low sensitivity (59%) for cardiac causes 1, 4
• Portable chest X-rays can assess pulmonary congestion in acute settings 1

Definitive Cardiac Assessment

• Transthoracic echocardiography is the diagnostic standard and should be performed in all patients with dyspnea of suspected cardiac origin to assess left ventricular ejection fraction, valvular function, and identify mechanical complications 1, 4
• Stress echocardiography can characterize cardiovascular etiologies including global or regional systolic dysfunction from myocardial ischemia 1

Advanced Imaging When Indicated

• Coronary CT angiography (CCTA) is appropriate as a noninvasive alternative to catheter angiography for assessing coronary artery disease 1
• Consider cardiac MRI with function and vasodilator stress perfusion for evaluating viable myocardium in patients with acute heart failure 1

Specific Cardiac Etiologies to Consider

Heart Failure

• Approximately 85% of chronic breathlessness cases are attributable to congestive heart failure, myocardial ischemia, or COPD 3
• Heart failure may result from myocardial damage, arrhythmia, or mechanical complications such as mitral regurgitation or ventricular septal defect 1
• Up to 40-50% of heart failure patients have preserved ejection fraction (HFpEF), with mortality similar to systolic heart failure 1, 6
• Clinical features include breathlessness, sinus tachycardia, third heart sound, and pulmonary rales 1

Acute Coronary Syndromes

• Approximately 40% of men and 48% of women with ACS present with dyspnea, either isolated or combined with chest pain 5
• Women are at particular risk for underdiagnosis of cardiac causes and should always have cardiac etiologies considered 4
• Resting chest tightness with dyspnea requires urgent evaluation to exclude acute coronary syndrome 2

Valvular Heart Disease

• Aortic stenosis/insufficiency and mitral valve stenosis/insufficiency are important cardiac causes of dyspnea 1
• Echocardiography identifies these structural abnormalities and assesses their hemodynamic significance 1

Arrhythmias

• Atrial fibrillation, inappropriate sinus tachycardia, sick sinus syndrome, and bradycardia can all cause breathlessness 1
• Consider 30-day event monitoring or implantable cardiac monitor to detect rare arrhythmias causing episodic symptoms 2

Mechanical Complications

• Ventricular septal defect and acute mitral regurgitation from papillary muscle rupture are life-threatening complications of myocardial infarction 1
• Cardiac tamponade from subacute free wall rupture presents with sudden hemodynamic deterioration and classical tamponade signs 1

Severity Classification

Use the Killip classification for heart failure in acute myocardial infarction 1:

• Class 1: No rales or third heart sound
• Class 2: Pulmonary congestion with rales over <50% of lung fields or third heart sound
• Class 3: Pulmonary edema with rales over >50% of lung fields
• Class 4: Cardiogenic shock

Management Considerations for Severe Cardiac Breathlessness

Killip Class III and IV (Severe Heart Failure and Shock)

• Administer oxygen and monitor oxygen saturation with pulse oximetry 1
• Check blood gases regularly 1
• Consider non-invasive ventilation (continuous positive airway pressure) as early as possible 1
• Endotracheal intubation with ventilatory support may be required 1

Identification of Viable Myocardium

• Patients with acute heart failure may have stunned (reperfused but with delayed contractile recovery) or hypoperfused viable myocardium 1
• Identification of viable myocardium followed by revascularization can lead to improved left ventricular function 1

Critical Pitfalls to Avoid

• Do not assume relief with nitroglycerin is diagnostic of myocardial ischemia—this should not be used as a diagnostic criterion 4
• Avoid administering high-concentration oxygen to patients at risk of hypercapnic respiratory failure, as this can worsen respiratory acidosis 4
• Do not overlook cardiac causes in elderly patients who may present atypically with confusion, delirium, or falls rather than classic breathlessness 4
• Recognize that more than 30% of breathlessness cases are multifactorial, requiring assessment for both cardiac and pulmonary contributions 3
• Do not rely on symptoms alone to guide optimal titration of neurohormonal inhibitors (ACE inhibitors, ARBs, beta-blockers, aldosterone antagonists), as these drugs impact mortality independent of symptom improvement 1

When to Refer for Advanced Cardiac Evaluation

• Hospitalization is warranted when ventricular arrhythmia or acute coronary syndrome cannot be excluded 2
• Breathlessness with syncope or presyncope may indicate pulmonary embolism or serious cardiac pathology requiring immediate investigation 4
• Ripping chest pain with sudden onset in a hypertensive patient suggests acute aortic syndrome and requires immediate investigation 4
• For high-risk patients with non-ST-elevation ACS, prompt invasive coronary angiography and revascularization within 24-48 hours reduces mortality from 6.5% to 4.9% 5