What are the diagnostic and treatment approaches for cardiac causes of shortness of breath?

Cardiac Causes of Shortness of Breath: Diagnostic and Treatment Approach

Transthoracic echocardiography (TTE) is the primary diagnostic tool for evaluating cardiac causes of shortness of breath and should be performed urgently in patients with acute dyspnea to identify life-threatening conditions and guide immediate management. 1

Initial Diagnostic Evaluation

Immediate Assessment and Testing

• Obtain an ECG immediately to assess for acute coronary syndrome, arrhythmias, and other cardiac abnormalities in all patients presenting with shortness of breath 2
• Measure vital signs including pulse rate, respiratory rate, blood pressure, and oxygen saturation via pulse oximetry 2
• Check arterial blood gas tensions noting the inspired oxygen concentration (FiO₂) 2
• Obtain chest radiograph to evaluate for pulmonary edema, cardiomegaly, and rule out pulmonary causes 2
• Measure natriuretic peptides (BNP or NT-proBNP) as elevated levels support the diagnosis of heart failure 1

Echocardiographic Assessment

TTE is mandatory and should be performed urgently in patients with acute shortness of breath when cardiac pathology is suspected, as it provides critical diagnostic and prognostic information 1. The echocardiogram should assess:

• Left ventricular size, wall thickness, and systolic function (ejection fraction) 1
• Right ventricular size and function 1
• Valvular structure and function 1
• Pericardial effusion and tamponade 1
• Regional wall motion abnormalities suggesting ischemia 1

Major Cardiac Causes to Identify

Heart Failure

Heart failure is the most common cardiac cause of shortness of breath, with HFpEF now accounting for more than 50% of heart failure cases and having outcomes comparable to HFrEF 1. The diagnostic criteria require:

• Symptoms and/or signs of heart failure caused by structural/functional cardiac abnormalities 1
• Either elevated natriuretic peptides OR objective evidence of cardiogenic pulmonary or systemic congestion 1
• LVEF ≥50% defines HFpEF, while LVEF 40-50% defines HFmrEF, and LVEF <40% defines HFrEF 1

Acute Valvular Heart Disease

A murmur in a patient with acute cardiorespiratory compromise is an indication for urgent TTE 1. Echocardiography detects:

• Valve morphology and function abnormalities 1
• Etiology including infective endocarditis 1
• Hemodynamic effects on chamber size 1
• Acute valvular regurgitation (particularly mitral or aortic) which can cause rapid decompensation 1

Pulmonary Embolism

TTE has limited sensitivity for directly visualizing PE but provides critical prognostic information 1:

• May rarely identify main and proximal PE, which is associated with increased mortality 1
• Tricuspid annular plane systolic excursion (TAPSE) below 15 mm carries adverse prognostic significance in normotensive patients 1
• Right ventricular dysfunction on TTE identifies high-risk patients who may benefit from escalated therapy 1
• McConnell's sign (RV free wall hypokinesis with apical sparing) supports PE diagnosis 1

Acute Coronary Syndrome and Mechanical Complications

In patients with suspected acute coronary syndrome presenting with shortness of breath, coronary angiography should be performed emergently in those with highest risk features 1. TTE identifies:

• Regional wall motion abnormalities indicating ischemia or infarction 1
• Mechanical complications of MI including ventricular septal rupture, free wall rupture, and papillary muscle dysfunction 1
• Acute severe mitral regurgitation from papillary muscle rupture 1

Pericardial Disease

TTE is the primary tool to diagnose pericardial effusions with and without tamponade 1. Look for:

• Pericardial effusion size and distribution 1
• Signs of tamponade physiology (right atrial and ventricular diastolic collapse, respiratory variation in mitral/tricuspid inflow) 1
• Constrictive physiology in chronic cases 1

Aortic Dissection

In patients with acute shortness of breath where there is clinical concern for aortic dissection, computed tomography angiography (CTA) of the chest, abdomen, and pelvis is recommended for diagnosis and treatment planning 1. If CT is contraindicated or unavailable, TEE or cardiac MRI should be performed 1. TTE can identify:

• Proximal aortic dissection flaps 1
• Acute aortic regurgitation from dissection 1
• Pericardial effusion from aortic rupture 1

Critical Pitfalls to Avoid

HFpEF Mimics

Do not assume all patients with congestion and preserved EF have HFpEF 1. Systematically evaluate for:

• Noncardiac mimics: kidney disease, liver disease, chronic venous insufficiency causing congestion 1
• Cardiac mimics requiring specific therapy: infiltrative cardiomyopathy (particularly cardiac amyloidosis), hypertrophic cardiomyopathy, pericardial disease, valvular heart disease, high-output heart failure 1
• Red flags for cardiac amyloidosis include increased LV wall thickness with low voltage on ECG, carpal tunnel syndrome, lumbar spinal stenosis, and peripheral neuropathy 1

Post-Cardiac Arrest Patients

In patients with return of spontaneous circulation after cardiac arrest, early identification of cardiac versus non-cardiac causes is critical 1:

• Perform coronary angiography first if clinical or ECG evidence suggests myocardial ischemia 1
• If no causative coronary lesions found, obtain brain and chest CT scan to identify neurological or respiratory causes 1
• In the absence of signs suggesting neurological or respiratory causes, coronary angiography takes priority 1

Treatment Approach Based on Etiology

Acute Heart Failure Management

Target mean arterial pressure should maintain adequate end-organ perfusion (normal or decreasing lactate, urine output ≥1 mL/kg/h) while considering the patient's baseline blood pressure and severity of myocardial dysfunction 1.

• Initiate diuretics for volume overload 1
• Consider vasodilators if blood pressure permits 1
• For HFpEF specifically, initiate guideline-directed medical therapy (GDMT) including SGLT2 inhibitors and other evidence-based therapies 1

Hemodynamic Instability

Immediate echocardiography is mandatory in patients with hemodynamic instability, particularly when suspected acute, life-threatening structural or functional cardiovascular abnormalities such as acute valvular regurgitation, pericardial tamponade, or aortic dissection 1.

• Treat based on specific etiology identified 1
• Serial echocardiography may help guide treatment in hemodynamically unstable patients 1
• Cardiac output monitoring may be considered but lacks outcome data 1

Oxygen Therapy Considerations

• Avoid excessive oxygen administration as it does not improve outcomes in patients without hypoxemia 1
• Target appropriate oxygen saturation based on underlying condition 2
• In patients with concurrent COPD, target oxygen saturation of 88-92% to prevent hypercapnic respiratory failure 2