Clinical significance of reduced systemic Windkessel size in severe ventricular septal defect patients.

Background: Large-shunt ventricular septal defect (VSD) infants manifest varied serious symptoms resulting from peripheral arterial constriction to compensate for increased pulmonary blood flow (Qp) and concomitantly decreased systemic blood flow (Qs). The aim of the present paper was therefore to estimate the whole arterial space proximal to arterioles as the systemic Windkessel size (WS) in these infants and compare it with aortic volume (AV) estimated angiographically. Method: Subjects were divided into three groups. Group la consisted of the so-called balanced-pressure VSD infants; group 1b consisted of those with normal or moderately increased pulmonary artery pressure (PAP) and highly augmented Qp; and group 2 consisted of those with a history of mucocutaneous lymph node syndrome as controls for Qp and pulmonary artery pressure. WS was computed from the Windkessel model, while the AV was calculated from the angiogram. Maximal systolic (WSs), mean (WSm), and minimum diastolic (WSd) WS were defined, computed, and compared. Result: All WS were significantly smaller in group la; those of group 1b were between group la and group 2, with Qs-dependent reduction of WS throughout all these three groups. WSs, WSm, and WSd had negative correlations with right ventricular systolic pressure/left ventricular systolic pressure in group la and group 1b. WSm, or the time averaged size, proved to be larger than the corresponding AV in all patients. The ratio of WSm/AV was significantly reduced in group la compared to group 1b and group 2, indicating that systemic arterial Windkessel space in severe VSD infants is significantly small, especially so in terms of space distal to aortic valve and proximal to arterioles. Conclusion: In severe VSD infants the whole systemic arterial space proximal to arterioles (WS) is reduced in size according to severity.