Dynamic Auscultation Topic Review

Dynamic auscultation refers to using maneuvers to alter hemodynamic parameters during cardiac auscultation in order to diagnose the etiology of a heart sound or murmur.

Valsalva Maneuver

The Valsalva maneuver is performed by having a patient “bear down” — as if they are going to have a bowel movement, exhaling forcefully with the airway closed. The hemodynamic changes that occur are complex; however, the ultimate result is a decrease in left ventricular preload.

The most important use of the Valsalva maneuver is to distinguish the murmur of aortic stenosis from hypertrophic obstructive cardiomyopathy — or simply to bring forth the murmur of HOCM. Aortic stenosis will soften or not change, whereas the murmur of HOCM becomes quite loud with Valsalva.

HOCM

The Valsalva maneuver is also performed during routine echocardiographic examinations to see if a patient with grade II or worse diastolic function can decrease his or her left ventricular filling pressures adequately. If the Valsalva maneuver fails to reduce the left ventricular pressure in the setting of diastolic heart failure, then grade IV diastolic dysfunction is said to be present — indicating a poor prognosis.

Squatting from a Standing Position

Squatting forces the blood volume that was stored in the legs to return to the heart, increasing preload and thus increasing left ventricular filling.

This maneuver will decrease the murmur of HOCM, as the increased left ventricular volume helps displace the hypertrophied interventricular septum, causing less outflow tract obstruction.

This maneuver causes the click of MVP to move later in systole.

MVP

Standing from a Squatting Position

Standing quickly from a squatting position causes blood to move from the central body to the legs, resulting in less blood returning to the heart and decreasing left ventricular preload — similar to the effect seen with the Valsalva maneuver.

This maneuver will increase the murmur of HOCM and decrease that of aortic stenosis.

This maneuver causes the click of MVP to move earlier in systole.

Leg Raising

Passive leg raising is done simply by raising the legs high in a patient lying supine. This results in blood that was pooled in the legs returning to the heart, increasing left ventricular filling and preload — similar to the effect seen with squatting from a standing position.

This maneuver will decrease the murmur of HOCM, as the increased left ventricular volume helps displace the hypertrophied interventricular septum, causing less outflow tract obstruction.

This maneuver causes the click of MVP to move later in systole.

Handgrip Exercise

Isometric handgrip exercises are performed by having a patient squeeze hard repetitively. This results in increased blood pressure, similar to exercise, and thus increased afterload. Elderly individuals may have a hard time with this maneuver, and transient arterial occlusion (described below) can be used instead.

This maneuver will increase the intensity of left-sided regurgitant murmurs including MR and AR. However, handgrip exercises will have no effect on the murmur of AS, which helps distinguish the presence of coexistent MR from Galliverdin phenomenon.

Transient Arterial Occlusion

This maneuver is performed by placing a blood pressure cuff on both arms and inflating it to 20 to 40 mmHg above the systolic blood pressure for 20 seconds — effectively resulting in increased afterload.

This maneuver will increase the intensity of left-sided regurgitant murmurs including MR and AR and is especially useful in elderly individuals who are unable to perform adequate handgrip exercises.

Amyl Nitrate Inhalation

Amyl nitrate decreases left ventricular afterload by dilating the peripheral arteries and would decrease the murmur of MR.

When the afterload is decreased, there is less resistance to blood flow from the LV through the aortic valve; this means less blood regurgitates through the mitral valve, thereby decreasing the intensity of the murmur.

Amyl nitrate can be given via inhalation to reduce afterload for diagnostic purposes in the cardiac catheterization laboratory (to invoke a LV outflow tract gradient in patients with HOCM) or as a diagnostic tool during cardiac physical examination. Due to the advancement of echocardiography, it is not commonly used any longer.