Clinical implication of main pulmonary artery Windkessel size after banding operation

The Windkessel model, proposed in 1895 by O. Frank, successfully explained systemic and abnormal pulmonary hemodynamics of congenital cardiac defects. The model is essentially a functional one and describes only hemodynamics, not anatomical or geographic structures. Because pulmonary arterial banding (PAB) adds a substantial resistance proximal to arterioles, it provides an ideal anatomical structure of the Windkessel model, namely, an elastic reservoir of much dilated main pulmonary artery (mPA) followed by a substantial artificial resistance of banding.

The pulmonary artery (PA) Windkessel size (WS) of 10 patients, several months to years after PAB, were estimated both in peak systole (WSs) and minimum diastole (WSd), as the product of Windkessel compliance and proximal to distal pulmonary arterial pressure difference at each cardiac phase. They were compared to cineangiogram-determined corresponding volumes (Vs, Vd) of PA proximal to the band or mPA.

WSs and WSd correlated well with Vs and Vd, respectively, with the correlation coefficient of 0.91 and 0.62, indicating that the Windkessel in these patients corresponds to mPA. Among five patients whose resistance at the band comprised more than half of the whole PA resistance, the coefficients proved even better.

Much bigger secondarily developed Windkessel, as placed proximal to the band on top of a substantial resistance at PAB, contributed much to alleviate the stress downstream at the periphery caused by greatly increased systolic stroke volume into mPA in these cardiac defects.