Biomechanical hearts - Muscular blood pumps, performed in a 1-step operation, and trained under support of clenbuterol

Background-As shown previously in goats, clenbuterol increased the power of electrically conditioned skeletal muscle ventricles (SMVs) of clinically r elevant size (150 mL), which were constructed around a mock system. They pu mped against a pressure of 60 to 70 mm Hg immediately during surgery and up to several months after, finally at >1 L/min. SMVs without clenbuterol adm inistration failed. Thus, we expected that clenbuterol-supported SMVs might become integrated into the circulation by a 1-step operation instead of th e 2-step procedure required up to now. Methods and Results-In adult Boer goats (n=5), latissimus dorsi muscle was wrapped around a polyurethane chamber of 150 mL that was connected to the d escending aorta. This muscular flow-through pumping chamber containing a st abilizing inner layer (called a biomechanical heart [BMH]) was formed and i mmediately made to work against a systemic load with the support of clenbut erol (5 X 150 mug/wk). During surgery, the mean stroke volume of BMHs was 5 3.8 +/- 22.4 mL. One month after surgery, in peripheral arterial pressure, the mean diastolic (PID) and minimal diastolic (P-min) pressures of BMH-sup ported heart cycles differed significantly from unsupported ones (P-MD= +2. 9 +/-1.1 mm Hg [P <0.04], P-min=- 2.4 +/-0.9 mm Hg [P <0.04]). After BMH-su pported heart contractions, the subsequent maximal rate of pressure generat ion, dP/dt(max), increased by 20.5 +/-8.1% (P <0.02). One BMH, catheterized 132 days after surgery, shifted a volume of 34.8 mL per beat and 1.4 L/min with a latissimus dorsi muscle of 330 g. Depending on duration of training , the percentage of myosin heavy chain type I ranged between 31% and 100%. Conclusions-Under support of clenbuterol, BMHs of a clinically relevant siz e can be trained effectively in the systemic circulation after a 1-step ope ration and offer the prospect of a sufficient volume shift and probably unl oading of the left ventricle.