MYOCYTE RECOVERY AFTER MECHANICAL CIRCULATORY SUPPORT IN HUMANS WITH END-STAGE HEART-FAILURE

Background-The failing myocardium is characterized by decreased force production, slowed relaxation, and depressed responses to beta-adrener gic stimulation. In some heart failure patients, heart function is so poor that a left ventricular assist device (LVAD) is inserted as a bri dge to transplantation. In the present research, we investigated wheth er circulatory support with an LVAD influenced the functional properti es of myocytes from the failing heart. Methods and Results-Myocytes we re isolated from human explanted failing hearts (HF-myocytes) and fail ing hearts with antecedent LVAD support (HF-LVAD-myocytes). Studies of myocyte function indicated that the magnitude of contraction was grea ter (9.6+/-0.7% versus 6.9+/-0.5% shortening), the time to peak contra ction was significantly abbreviated (0.37+/-0.01 versus 0.75+/-0.04 se conds), and the time to 50% relaxation was reduced (0.55t0.02 versus 1 .45+/-0.11 seconds) in the HF-LVAD-myocytes compared with the HF-myocy tes (P<0.05). The HF-LVAD-myocytes had larger contractions than the HF -myocytes at all frequencies of stimulation tested. The negative force -frequency relationship of the HF-myocytes was improved in HF-LVAD-myo cytes but was not reversed. Responses to beta-adrenergic stimulation ( by isoproterenol) were greater in HF-LVAD-myocytes versus HF-myocytes. Conclusions-The results of the study strongly support the idea that c irculatory support with an LVAD improves myocyte contractile propertie s and increases beta-adrenergic responsiveness.