We shall now listen at the lower left sternal edge with the diaphragm of the stethoscope. Listen particularly to the diastolic murmur and notice its variation with respiration. [Cut-away]
The murmur of pulmonary regurgitation is heard here in diastole because that is the direction of the regurgitant jet back into the right ventricle. You do not hear the systolic flow murmur going back across the pulmonary valve that was heard higher up at the base. And notice the respiratory variation. [Sounds] That is because the right sided murmur of pulmonary regurgitation and right sided murmurs in general, will augment with inspiration, as blood flow is augmented into the right ventricle.
Oscilloscopic image
By viewing an oscilloscopic image and simultaneously listening we can further appreciate these auscultatory events. Note that the diastolic mumur increases in intensity during inspiration.
Pulmonary regurgitation due to pulmonary hypertension
The high frequency decrescendo murmur of pulmonary regurgitation due to pulmonary hypertension is best heard at the mid-to-lower left sternal edge, since the regurgitant flow is into the right ventricle. The murmur also increases with inspiration, as right-sided filling is augmented by the drop in intrathoracic pressure.
Pulmonary hypertension - other patients
In other patients, progressive increases in right ventricular pressure and dilatation contributes to functional tricuspid regurgitation. This results in a holosystolic murmur heard best at the lower left sternal edge that increases with inspiration. A right ventricular S4 that increases with inspiration can often be heard at the lower left sternal edge in patients with pulmonary hypertension. In our patient, although the S4 was palpable, it was not audible due to its extremely low frequency.