What is the etiology of the third heart sound (S3)?

From the Guidelines

The third heart sound (S3) is primarily associated with heart failure (HF).

Etiology of S3

• The presence of an S3 is a significant predictor of increased risk during noncardiac surgery, particularly in patients with a history of heart failure 1.
• Heart failure is often caused by underlying conditions such as hypertensive heart disease or coronary artery disease (CAD), which can lead to the development of an S3 1.
• A careful history and physical examination are essential in detecting unsuspected heart failure and identifying the underlying cause of the S3 1.
• Systemic hypertension is a major risk factor for the development of heart failure, increasing its development by two- to four-fold 1.
• The S3 can also be associated with other conditions such as valvular disease or congenital heart disease, which can be identified through a thorough physical examination and history taking 1.

From the Research

Etiology of the Third Heart Sound (S3)

The etiology of the third heart sound (S3) is a complex phenomenon that has been studied extensively. The main factors contributing to the S3 include:

• Abrupt deceleration of left ventricular (LV) inflow during early diastole 2
• Increased LV filling pressures 2, 3
• Decreased LV compliance 2, 4
• Sudden intrinsic limitation of longitudinal expansion of the left ventricular wall during early diastolic filling 5
• Ventricular inflow velocity exceeding the local wave velocity, resulting in a shock wave 6

Key Findings

Some key findings from the studies include:

• The ratio of early mitral inflow velocity to diastolic velocity of the mitral annulus (E/E') is independently associated with the S3 confidence score 2
• The spectral energy of S3 is distributed in the lower frequency bands, with 50% of the energy in the 0-15 Hz band 4
• The energy distribution of S3 tends towards the higher frequencies with increase in age 4
• The S3 occurs earlier in the cardiac cycle with increase in age of the subject 4
• Phonocardiography and echocardiography can successfully confirm early-diastolic rapid distension of the left ventricle along with rapid ventricular filling and abrupt deceleration of the atrioventricular blood flow as the precise etiology of the S3 3