The murmur of chronic mitral regurgitation is the prototype of the holosystolic regurgitant murmur, as shown in Fig. 10-77. It begins with or replaces S1 and continues throughout systole in a plateaulike fashion beyond A2, finally terminating when the LV pressure drops to the level of the left atrial pressure during isovolumic relaxation.287 In contrast to the systolic ejection murmur, there is little variation in its intensity with varying cycle lengths.288 It is heard best at the apex and radiates well into the axilla; only the loudest murmurs are associated with a thrill at the apex. There is little variation in its intensity with respiration, and it is frequently accompanied by a loud diastolic filling sound followed by a short rumble. In this situation, the loud S3 is not a manifestation of congestive failure but a reflection of hemodynamically significant mitral regurgitation. Likewise, the short rumble does not mean concomitant obstruction at the mitral valve but rather is secondary to extremely rapid early diastolic filling. The intensity of the murmur is directly related to the pressure gradient between the left ventricle and the left atrium.
The diagnosis of hemodynamically significant mitral regurgitation is established by the presence of the holosystolic regurgitant murmur and loud S3 associated with a short flow rumble. The etiology, however, is determined by the clinical presentation and associated physical findings and is best confirmed by echocardiography (see Chap. 13).
The classic holosystolic (pansystolic) murmur of tricuspid regurgitation in the setting of RV pressure overload is best heard at the lower left sternal border. At times it may be heard laterally to the midclavicular line, indicating that the right ventricle occupies the region of the cardiac apex. Furthermore, it generally can be differentiated from mitral regurgitation because its intensity is usually strongly influenced by respiration.289 During continuous and accentuated respiration, the murmur increases in intensity with inspiration due to the increased venous return and RV filling associated with inspiration. The inspiratory increase in loudness of right-sided auscultatory events is known as Carvallo's sign. Careful inspection of the JVP while auscultating the murmur will be of further help in defining its tricuspid origin, showing a prominent v wave with a rapid y descent that augments during inspiration. In severe RV failure, this respiratory variation may be absent, but it may reappear as the state of compensation improves. With severe tricuspid regurgitation, a short flow rumble introduced by an S3 can be present, just as with mitral regurgitation, and both will increase with inspiration.290
The holosystolic murmur of VSD is heard best just off the sternal border in the fourth, fifth, and sixth intercostal spaces and is usually accompanied by a forceful thrill.291 The murmur does not radiate to the axilla as with mitral regurgitation and does not have the respiratory variation characteristic of tricuspid regurgitation. Wide physiologic splitting with an easily heard P2 is usually present when the left-to-right shunt is hemodynamically significant. When the shunt is large, there is a left ventricular S4 followed by a short flow rumble. The regurgitant murmur is due to high-velocity flow from the high-pressure left ventricle to the lower-pressure right ventricle, and its intensity correlates poorly with the degree of left-to-right shunting. For example, a grade 5 murmur may be associated with a very high velocity flow through a small hemodynamically insignificant muscular VSD (Roger). On the other hand, an equally loud murmur associated with a thrill may be present with a larger defect having massive left-to-right shunting. When the defect is very large and the RV and LV pressures are equal, however, no murmur may be produced across the defect; instead, the short pulmonary ejection murmur of severe pulmonary hypertension is present (Eisenmenger's VSD). The murmur of VSD is very sensitive to vasoactive agents that alter vascular impedance, and a marked decrease in both the LV-RV pressure gradient and the intensity of the murmur is seen following the administration of amyl nitrite.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...