Table 4.17 - Characteristics in large/unrestrictive VSD.

Defect approaches diameter of aorta (low flow resistance); equalization of LV & RV pressures.
Direction and magnitude of flow controlled only by resistances of pulmonary and systemic vascular beds; low pulmonary resistance means massive L ---> R shunting, until pulmonary congestion and edema causes vasoconstriction (eventual pulmonary vascular obstructive disease, surgery by 12 mo. prevents irreversible condition, othewise death by 10 yrs of age).
Congestive heart failure may supervene.
Large O₂ step-up in RV.
Massive flow returning from lungs enlarges LA & LV (seen with ECG, echo), as well as RV and pulmonary vessels (increased vascularity seen with X-ray).
A low pitched rumbling mid-diastolic murmur of increased mitral flow is heard during rapid filling phase.
Intensity and duration of systolic murmur is dependent upon orifice size and flow dynamics.
Heart sound S₂ may be increased due to pulmonary hypertension.
Pulmonary vascular resistance increases until shunting reverses R ---> L.
Altered pressures and saturation -