What is the significance of a third heart sound (S3) over the pulmonary area?

From the Guidelines

A third heart sound (S3) heard over the pulmonary area is a significant finding that typically indicates right ventricular dysfunction or volume overload, requiring prompt evaluation for potential right heart failure, pulmonary hypertension, or other cardiac pathology. This sound occurs during early diastole when blood rapidly flows into a ventricle with decreased compliance. When specifically heard over the pulmonary area, it suggests right-sided heart issues rather than left ventricular dysfunction. Common causes include pulmonary hypertension, right ventricular failure, tricuspid regurgitation, or atrial septal defect 1.

Clinical Significance

The presence of an S3 gallop is associated with a poor short- and long-term prognosis, especially in the context of acute myocardial infarction 1. The clinical features of heart failure, including breathlessness, sinus tachycardia, a third heart sound, and pulmonary rales, are critical for diagnosis and management.

Evaluation and Management

Evaluation should include a complete cardiac workup with:

• Echocardiography to assess right ventricular size and systolic performance, as well as to evaluate for valvular or pericardial abnormalities 1
• ECG to assess for arrhythmias or signs of ischemia
• Chest X-ray to evaluate for pulmonary congestion or cardiomegaly
• Possibly cardiac MRI for further evaluation of right ventricular function and structure

Treatment depends on the underlying cause but often includes:

• Diuretics like furosemide to reduce volume overload
• Specific therapies for the primary condition, such as pulmonary hypertension or right ventricular failure
• Monitoring for arrhythmias and checking for electrolyte abnormalities and concomitant conditions 1

Key Points

• The S3 gallop has a low-pitched "lub-dub-dub" quality and is best heard with the bell of the stethoscope with the patient in left lateral decubitus position.
• Prompt evaluation and management are crucial to improve outcomes in patients with an S3 gallop heard over the pulmonary area.

From the Research

Significance of a Third Heart Sound (S3) over the Pulmonary Area

• The presence of a third heart sound (S3) over the pulmonary area is associated with severe hemodynamic alterations, including right ventricular dysfunction and pulmonary regurgitation 2, 3.
• An S3 is more prevalent in patients with primary left ventricular dysfunction and is related to a higher early filling velocity, restrictive filling, and severe regurgitation 2.
• The presence of an S3 is also associated with elevated right ventricular filling pressure and a non-compliant right ventricle, as seen in cases of right-sided heart failure due to free pulmonary regurgitation 3.
• However, not all cases of right ventricular dilatation result in significant tricuspid regurgitation, and the relationship between RV dilatation and functional tricuspid regurgitation is complex 4.

Clinical Implications

• An audible S3 is an important clinical finding that indicates severe hemodynamic alterations and should lead to a comprehensive assessment and consideration of vigorous medical or surgical treatment 2.
• The presence of an S3, along with other clinical findings such as a harsh diastolic regurgitant murmur and a widely split first heart sound, can aid in the diagnosis of right-sided heart failure due to severe pulmonary regurgitation 3.
• The evaluation of right ventricular systolic function, including the use of strain analysis, is crucial in patients with severe tricuspid regurgitation, as it can provide prognostic information and guide treatment decisions 5.