Left ventricular hypertrophy and exercise-induced hypertension can occur in patients after repair of coarctation of the aorta (CoA) in the absence of residual obstruction. This study addresses the hypothesis that compliance mismatch due to decreased proximal aortic compliance results in hypertension and a higher ventricular workload, resulting in ventricular hypertrophy.Methods: Two models of a postoperative CoA repair without obstruction were studied. Model 1 consisted of two segments of equally compliant silicone tubing sutured at their midpoint. Model 2 consisted of a proximal segment of less compliant silicone tubing sutured to the more compliant distal tubing used for Model 1. Using a pulsatile flow model with a blood analog fluid, the static and oscillatory components of the vascular workload were measured. Comparisons of workload for the two models were performed at cardiac outputs of 1, 3 and 5 l/min. Simultaneous pressure (P) and flow (Q) waveforms from the proximal vessel were recorded and resolved into ten harmonics using Fourier series analysis. Static work was calculated as Pmean · Qmean. Pulsatile work was calculated as 1/2Σ PiQi cosΘ, where Pi and Qi are the magnitudes of the ith pressure and flow harmonics and Θ is the phase between them. Results: For both models the mean arterial pressure increased linearly with flow. Model 2 had higher pressures than Model 1 for each condition. Total workload increased exponentially with increases in flow in both models (Fig). For Model 2, this increase was significantly greater than in Model 1. Conclusion:Compliance mismatch alone increases the workload imposed upon the left ventricle, and this workload is exaggerated with exercise. Early repair of aortic coarctation may prevent proximal aortic stiffening. Therefore, early repair may prevent arterial hypertension with exercise, and the development of ventricular hypertrophy after successful coarctectomy.

figure 1

Figure 1