Impact of vascular adaptation to chronic aortic regurgitation on left ventricular performance

Background-This investigation was designed to test the hypothesis that vasc ular adaptation occurs in patients with chronic aortic regurgitation to mai ntain left ventricular (LV) performance. Methods and Results-Forty-five patients: with chronic aortic regurgitation (mean age 50+/-14 years) were studied using a micromanometer LV catheter to obtain LV pressures and radionuclide ventriculography to obtain LV volumes during multiple loading conditions and right atrial pacing. These 35 patie nts were subgrouped according to their LV contractility (E-es) and ejection fraction values. Group I consisted of 24 patients with a normal E-es. Grou p IIa consisted of 10 patients with impaired E-es values (E-es <1.00 mm Hg/ mL) but normal LV ejection fractions; Group Ilb consisted of 11 patients wi th impaired contractility and reduced LV ejection fractions. The left ventr icular-arterial coupling ratio, E-es/E-s where E-a was calculated by dividi ng the LV end-systolic pressure by LV stroke volume, averaged 1.60+/-0.91 i n Group I. It decreased to 0.91+/-0.27 in Group IIa (P<0.05 versus Group I) , and it decreased further in Group IIb to 0.43+/-0.24 (P<0.001 versus Grou ps I and IIa), The LV ejection fractions were inversely related to the E-a values in both the normal and impaired contractility groups (r=-0.48, P<0.0 5 and r=-0.56, P<0.01, respectively), although the slopes of these relation ships differed (P<0.05). The average LV work was maximal in Group IIa when the left ventricular-arterial coupling ratio was near 1.0 because of a sign ificant decrease in total arterial elastance (P<0.01 versus Group I). In co ntrast, the decrease in the left ventricular-arterial coupling ratio in Gro up IIb was caused by an increase in total arterial elastance, effectively d ouble loading the LV, contributing to a decrease in LV pump efficiency (P<0 .01 versus Group IIa and P<0.001 versus Group I). Conclusions-Vascular adaptation may be heterogeneous in patients with chron ic aortic regurgitation. In some, total arterial elastance decreases to max imize LV work and maintain LV performance, whereas in others, it increases, thereby double loading the LV, contributing to afterload excess and a dete rioration in LV performance that is most prominent in those with impaired c ontractility.