S3 in Ventricular Volume Overload

In volume overload states such as mitral and tricuspid regurgitations, the inflow volume during diastole into the ventricle is larger because the regurgitant blood into the atrium as well as the usual venous (systemic or pulmonary) return will enter the ventricle during diastole. The ventricle is also hyperdynamic in its contraction in these states because of the Starling effect caused by the large volume of diastolic filling. The relaxation following such stronger contraction will also be expected to be very rapid because of better restoring forces. In addition, the v wave peak pressure in the atrium will be higher because of the regurgitation (through the mitral and the tricuspid valves). For these reasons, the inflow into the ventricle not only will be large in volume but will also move with greater velocity, achieving greater energy. In fact, an apexcardiogram obtained in patients with volume-overloaded left ventricle will often show an exaggerated large rapid filling wave with an overshoot (Figs. 34A,B). The response of the ventricles to chronic volume overload is to dilate and enlarge. This is accompanied by increased compliance. Therefore, the deceleration is mainly brought about from the rapid expansion to slow expansion alone. The S3 in these states may in fact have enough duration and sound like a short murmur. In late stages when the ventricles have developed secondary hypertrophy and focal fibrosis, particularly in the subendocardial regions, the resulting decrease in compliance will also play a part in the production ofthe S3. Similar situations are also likely to occur and result in left-sided S3 in large left-to-right shunts through persistent ductus arteriosus and ventricular septal defects. In these conditions, the increased pulmonary flow received through the communication has to exit through the pulmonary veins into the left atrium.

In atrial septal defect with large shunts, the increased flow from the left atrium into the right atrium causes a right ventricular volume overload. Similar considerations apply.

Fig. 34. Phonocardiogram (Phono) recordings taken from the apex area along with apexcardiogram (Apex) from two patients, both with significant mitral regurgitation causing left ventricular volume overloads. In both, overshoot of the rapid filling phase can be seen on the Apex coinciding with the S3 on the Phono.

Fig. 34. Phonocardiogram (Phono) recordings taken from the apex area along with apexcardiogram (Apex) from two patients, both with significant mitral regurgitation causing left ventricular volume overloads. In both, overshoot of the rapid filling phase can be seen on the Apex coinciding with the S3 on the Phono.

Fig. 35. Phonocardiogram (Phono) recording from a patient with severe aortic stenosis and left ventricular failure taken from the apex area along with the recoding of the apexcardiogram (Apex). The Phono shows both the fourth (S4) and third heart (S3) sounds.

However, because the right ventricle is more compliant than the left ventricle, increased flow through the tricuspid valve alone will not be sufficient to produce a right-sided S3. One can expect to hear a tricuspid inflow murmur in diastole instead (83).

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