II. Physiology
- S2 Heart Sound represents closure of the aortic valve and pulmonic valve
- The aortic valve typically closes slightly before the pulmonic valve
- Higher pressures in the systemic circulation force the aortic valve closed sooner
- During expiration, the S2 Heart Sound is typically heard as one sound (not split)
- During inspiration, the S2 Heart Sound is physiologically split
- Represents a more significant timing difference between the closure of aortic (A2) and pulmonic valves (P2)
- Greater right sided than left sided filling with inspiration results in a greater duration between A2 and P2
- Inspiration creates negative intrathoracic pressure
- Negative chest pressure increases right ventricular filling and volume (Preload)
- Negative chest pressure decreases left sided filling from lungs
III. Causes: S2 Wide Split
-
Right Bundle Branch Block
- Slower right ventricular contraction delays pulmonic valve closure
- Pulmonic Stenosis
- Prolonged right ventricular emptying due to obstructed flow, results in delayed pulmonic valve closure
- Mitral Regurgitation
IV. Causes: S2 Fixed Split
- Atrial Septal Defect
- Right Heart Failure
-
Pulmonary Hypertension
- P2 is also louder due to forced closure of the pulmonic valve
V. Causes: S2 Paradoxical Split (S2 splits during expiration)
-
Left Bundle Branch Block
- Slower left ventricular contraction delays aortic valve closure
- Pulmonic valve (P2) closes before aortic valve (A2), most prominent during expiration
- During inspiration, P2 is delayed, and therefore coincides with A2, resulting in paradoxical split
-
Aortic Stenosis
- Prolonged left ventricular emptying due to obstructed flow, results in delayed aortic valve closure
VI. Causes: Loud S2
- Pulmonic Stenosis
- P2 is louder due to forced closure of the pulmonic valve
- Arterial Hypertension
- A2 is louder due to forced closure of the aortic valve
VII. Resources
- University of Michigan Heart Sound and Murmur Library
VIII. References
- Goldberg (2014) Clinical Physiology, MedMaster, p. 48-9
Images: Related links to external sites (from Bing)
Related Studies
| Concepts | Finding (T033) |
| SnomedCT | 28827006 |
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| Spanish | segundo ruido cardíaco, R2 (función), segundo ruido cardíaco, R<sub>2</sub> (función), segundo ruido cardíaco, R2, segundo ruido cardíaco, R<sub>2</sub>, segundo ruido cardíaco, R2 (entidad observable), segundo ruido cardíaco, R<sub>2</sub> (entidad observable), segundo ruido cardíaco, R>2< (entidad observable), segundo ruido cardíaco, R>2< (función), segundo ruido cardíaco, R>2< |
