Causes of third heartsound

Etiology of S3
Abnormal increase in transmitral flow

• Mitral regurgitation
• VSD
• PDA

Depression of ventricular function

• LV dysfunction—LV S3
• RV dysfunction—RV S3
• LV S3 and RV S3

LV S3 may be either physiological or pathological
RVS3 is always pathological.
Causes of physiological S3 

• Children
• Young adults (< 40 years)
• Athletes
• Pregnancy.
• Pathological 3rd heart sound
• Pathologic S3 persists in the standing position and is associated with other signs of LV dysfunction.
• LV S3 - MR, LVF
• RV S3 - TR, RV

Causes of pathological S3

• High output states
• Congenital heart diseasis ASD, VSD,
• Regurgitant lesions of aortic, mitral, tricuspid valves.
• Hypertrophic cardiomyopathy
• ischaemic heart diseases
• Constrictive pericarditis
• Systemic hypertension
• Pulmonary hypertension

Differentiating Features between Right and Left Ventricular S3
RV-S3                                              LVS3
Tncmpid area                                      MItral area
Increas esOn inspiration                  Increases on expiration