second heart sound (S2)

Introduction

Occurs following the T wave on EKG & reflects closing of the aortic valve & pulmonic valves.

The aortic valve heart sound A2 generally precedes the pulmonic valve heart sound P2 (splitting of S2) & splitting increases with inspiration.

Also see aortic valve heart sound (A2) & pulmonic valve heart sound (P2).

Causes of widened splitting:

• occurs normally with inspiration
• occurs in conditions that delay right ventricular ejection
• right bundle branch block
• pulmonic stenosis
• pulmonary hypertension
• mitral regurgitation
• left to right shunt
  • ventricular septal defect
  • atrial septal defect

Fixed splitting (no changes with inspiration)

• atrial septal defect
• severe pulmonic stenosis with fixed right ventricular output

Paradoxical splitting (splitting narrows with inspiration)

• occurs with conditions that prolong LV ejection
• aortic stenosis
• left bundle branch block
• congestive heart failure (CHF)
• acute coronary syndrome with LV dysfunction
• left ventricular hypertrophy
  • hypertrophic cardiomyopathy
• due to:
  • delayed closure of aortic valve
  • A2 occurring subsequent to P2

At a rate of about 120 beats/second, systole & diastole become indistinguishable by auscultation & S1 must be distinguished from S2 from the timing of the carotid or apical impulse, both which occur in early systole, immediately after S1.

More general terms

• heart sound(s)

More specific terms

• aortic valve heart sound (A2)
• pulmonic valve heart sound (P2)