Lance Deeter, University of Utah
Continuous-flow left ventricular assist devices (LVADs) are used in advanced heart failure patients either to bridge them to transplantation or as a permanent-destination therapy. We determined whether chronic exposure to non-pulsatile blood flow and acute increases in coronary perfusion pressure associated with LVAD implantation would influence arterial function. Arteries from a transmural biopsy of the left-ventricle were obtained from ten male patients (54±4 years old) at the time of LVAD implant (n=17, 184±25 µm i.d.) and 239±51 days later upon LVAD explant (n=21, 281±22 µm i.d.). Lmax tension was determined and dose-response curves to potassium chloride (KCl, 10-100 mM) were performed using isometric tension techniques. Next, bradykinin (BK, 10-6 to 10-10 M) and sodium nitroprusside (SNP, 10-4 to 10-9 M) concentration-response curves were completed on vessels precontracted to ~65% of maximal tension development. Maximal BK-induced vasorelaxation was greater (p<0.05) at explant (85±5%) vs. implant (59±9%), while SNP evoked responses (~90%) were similar between time-points. These findings suggest coronary endothelial function is improved by LVAD implantation. Heart failure was precipitated by a myocardial infarction in six of the ten patients. These are referred to as “ischemic” patients whereas the remaining four are “non-ischemic” patients. We hypothesized that coronary vascular responses would be improved by LVAD implantation to a greater extent in ischemic vs. non-ischemic patients. In ischemic patients maximal BK-induced vasorelaxation was greater (p<0.05) in coronary arteries obtained at explant (87±6%, n=14, 305±30 μm i.d.) vs. implant (53±11%, n=12, 204±33 μm i.d.). In non-ischemic patients maximal BK-induced vasorelaxation was similar in arteries obtained at explant (79±9%, n=7, 232±21 μm) and implant (72±17%, n=5, 135±13 μm). SNP responses were similar (~90%) between groups at implant and explant. Collectively, our data suggest that LVAD implantation improves endothelium-dependent vasorelaxation in ischemic but not in non-ischemic patients.