Developmental Pathophysiology, Develop. Physiol., Dr. D. Penney
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 -
|PA ||20/5, 70%||100/30, 92%|
|LA ||2, 70%||30, 95%|
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