Electrophysiological alterations after mechanical circulatory support in patients with advanced cardiac failure

Background-Recognizing that mechanical circulatory support with a left vent ricular assist device (LVAD) induces changes in myocardial structure and co ntractile function, we examined whether there are changes in ventricular co nduction and/or repolarization among failing human hearts after LVAD implan tation. Methods and Results-We examined 12-lead electrocardiograms before surgery, immediately after LVAD placement, and at a delayed (>1 week) postoperative time point in 23 patients who were receiving LVAD support for refractory he art failure. The immediate effects of hemodynamic unloading via LVAD placem ent included a decrease in QRS duration from 117+/-6 to 103+/-6 ms (P<0.01) , an increase in absolute QT duration from 359+/-6 to 378+/-8 ms (P<0.05), and an increase in the heart rate-corrected QT interval (QTc) from 379+/-10 to 504+/-11 ms (P<0.01). None of these immediate changes were observed amo ng 22 patients undergoing routine coronary artery bypass grafting. With sus tained cardiac unloading via LVAD support, there was a marked decrease in t he QTc from 504+/-11 to 445+/-9 ms (P<0.001). Studies in isolated cardiac m yocytes, obtained at the time of transplantation, confirmed that delayed de creases in heart rate-adjusted QTc were the result of decreases in action p otential duration after LVAD support. Conclusions-Acute electrocardiogram responses to LVAD placement demonstrate the dependence of QRS and QT duration on load in the failing human heart. Delayed decreases in QTc and action potential duration reflect reversal of electrophysiologic remodeling in the failing heart. Shortening of the actio n potential duration likely contributes to the improved cellular contractil e performance observed after sustained LVAD support.