Split-Second-Heart-Sound
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1. delayed electrical activation of the right ventricle (as in complete right bundle branch block and premature ventricular beats, and with left ventricular pacemakers)
2. prolonged right ventricular or shortened left ventricular ejection time (as in valvular or infundibular pulmonic stenosis, mitral regurgitation, and ventricular septal defects)
3. altered impedance of the pulmonary vascular bed (massive pulmonary embolism).
Wide and fixed splitting of S2 (splitting of S2 that does not vary with respiration) is found in patients with large atrial septal defects, severe pulmonary stenosis, and right ventricular failure.
Normally splitting is more during inspiration when blood flow to the right heart increases due to negative intrathoracic pressure. In ASD this increase is compensated by left to right to shunt during expiration. So during whole cardiac cycle a fixed amount flows through pulmonic valve making the variation in split very small.
Paradoxical splitting of S2 (when splitting increases with expiration)
is usually due to a delayed A2. This delay in A2 may be due to
1. electrical conduction disorders (complete left bundle branch block, right ventricle premature contractions, and ventricular tachycardia) or
2. mechanical disorders (severe valvular aortic stenosis, left ventricular outflow obstruction, hypertrophic cardiomyopathy, coronary artery disease, myocarditis, and congestive cardiomyopathy).
Category: Pathology Notes
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1 comments:
really good
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