Elizabeth Johnson, University of Utah
College of Health, and Division of Endocrinology, Metabolism, and Diabetes
Constant-flow left ventricular assist devices (LVAD) are implanted in heart failure patients to assist the heart in pumping blood through the body either temporarily as a “bridge” mechanism until a heart transplant or permanently as a destination therapy. The blood flows constantly with an LVAD contrary to the natural pulsatile flow of the human heart. We wanted to determine if this constant flow attenuated the function of the arteries. A transmural biopsy was taken from seven male patients (52±6 years old) when the LVAD was implanted (pre) and again 142±2 days later upon LVAD explant (post). Arteries were obtained from the pre and post tissue biopsies. Vessel function was assessed using isometric tension techniques. After Lmax tension was determined for each vessel, the contraction-response curve of each vessel was tested using potassium chloride (KCl, 10-100 mM). Next the vessels were pre-contracted to ~65% maximal tension and treated with bradykinin (BK, 10-6 to 10-10 M) and sodium nitroprusside (SNP, 10-4 to 10-9 M) to determine, respectively, endothelium-dependent and -independent vasorelaxation. Maximal KCl-evoked contraction (0.99±0.22 and 0.69±0.14 mg tension development / μm vessel length), maximal BK-evoked vasorelaxation (64±13% and 80±7%), and maximal SNP-evoked vasorelaxation (92±3% and 92±4%), was similar in arteries obtained from pre (n=13 arteries, 206±40 μm i.d.) and post (n=14 arteries, 288±24 μm i.d.) transmural biopsy samples, respectively. These preliminary data indicate that coronary vascular function is not attenuated by LVAD implantation.