Ventricular Septal Defect - Size - Findings

Findings in our patient suggest a small-to-moderate defect, meaning one with a small-to-moderate left-to-right shunt. A defect of this size allows right ventricular pressures to remain normal or nearly so, and it also restricts flow producing high velocity, turbulent flow from left ventricle to right ventricle, causing the typical murmur. Flow occurs in this direction, unless some additional abnormality is present. A very small defect produces a short murmur that may end well before the second sound. An absent mid diastolic murmur at the apex also indicates no more than a moderate size defect. It implies that left ventricular filling volume is not significantly enhanced by the addition of flow across the defect when this flow returns to the left heart following passage through the lungs.

Bedside findings in our patient provide additional information indicating that pressures in the right ventricle and pulmonary artery are near normal, an important observation. Jugular venous pressure and wave form are normal, suggesting normal right ventricular filling pressure. Absence of a right ventricular impulse suggests that there is no right ventricular dilation or hypertrophy. We heard normal respiratory splitting of the second heart sound and normal intensity of the pulmonic component, P2, expected findings when pulmonary artery pressure is normal.

Patients with a large ventricular septal defect usually present with symptoms of heart failure beginning early in infancy. They feed with difficulty, resulting in poor weight gain, failure to thrive. Excessive sweating occurs commonly, as does fretfulness, due to fatigue and hunger.

Bedside findings typically demonstrate a thin infant with rapid respiratory rate, often with intercostal retractions and nasal flaring, due to use of accessory muscles in respiration. Inspiratory rales may be heard. Arterial pulses often are increased in amplitude, due to increased left ventricular stroke volume; and heart rate is greater than normal. Precordial examination reveals a right ventricular impulse and an apical impulse that is displaced, enlarged, hyperdynamic and non sustained.

Auscultation of the patient with a large ventricular septal defect includes a systolic ejection murmur at the upper left sternal edge, due to increased right ventricular ejection volume; narrow inspiratory splitting of the second heart sound, with a pulmonic component increased in intensity, because diastolic pressure in the pulmonary artery is increased; a third heart sound followed by a mid diastolic rumble at the apex, due to enhanced left ventricular filling. A fourth heart sound occasionally can be heard at the apex. The heart rate may be so rapid, greater than 150, that the third and fourth heart sounds blend with the diastolic murmur as a single event. The typical murmur of a ventricular septal defect may be absent, because a large ventricular septal defect allows left and right ventricular pressures to equalize. In effect, the two ventricles become as one. Substantial left-to-right flow occurs across such a defect, because pulmonary vascular resistance is less than systemic vascular resistance. This flow occurs without significant turbulence and, therefore, without a significant murmur at the ventricular septal defect. On the other hand, some ventricular septal defects may be large enough to allow substantial flow while still creating a pressure difference between the ventricles, thereby, producing the typical systolic murmur.