Let us evaluate together the acoustic events at the upper left sternal edge using the diaphragm of the stethoscope. We're going to focus on the splitting of the second heart sound during respiration. Everybody watch breathing. [Cut-away]
What we heard was wide splitting of the second heart sound during inspiration that persisted during expiration. In inspiration possibly six of seven hundredths of a second splitting, and in expiration possibly three or four hundredths. Now, that may not be so important, the exact number that you assign to the degree of splitting. What is important, is that the behavior of the second heart sound reflects intraventricular conduction abnormalities and intraventricular conduction abnormalities are important in the setting of acute myocardial infarction, whether it be right bundle branch block, which this could reflect, or left bundle branch block, where you would see paradoxic splitting of the second heart sound. Of course, the electrocardiogram is the most sensitive indicator of the intraventricular conduction abnormalities, but the bedside examination may also reflect them.
Oscilloscope
By viewing an oscilloscopic image and simultaneously listening, we can further appreciate these auscultatory events.