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Eur J Cardiothorac Surg 2003;24:926-931
© 2003 Elsevier Science NL

Distal thoracic aorta hemodynamics during exercise with continuous flow left ventricular assist system

^a McGowan Institute for Regenerative Medicine, University of Pittsburgh, 3025 East Carson Street, Pittsburgh, PA 15203, USA
^b Sun Medical Technology Research Corporation, Nagano, Japan
^c Tokyo Women's Medical University, Tokyo, Japan
^d University of Maryland, College Park, MD, USA

Received 20 January 2003; received in revised form 30 July 2003; accepted 6 August 2003.

^* Corresponding author. Present address: The Heart Institute of Japan, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan. Tel.: +81-3-3353-8111; fax: +1-412-383-9460
e-mail: shinkihara{at}aol.com

Objectives: Continuous flow left ventricular assist systems (LVAS) are being discussed as a destination therapy. LVAS patients will have expanded activity of daily life, including exercise. In this study, we analyzed the effects of exercise on blood flow in the distal thoracic aorta of LVAD implanted animals. Methods: Five calves with a continuous flow LVAS exercised on treadmill at two different pump flow rates (PFR), 60–80% (high PFR) and 25–30% (low PFR) of pulmonary artery flow rate. Pump, pulmonary artery and descending thoracic aorta flow waves were recorded before, during and after exercise. Systolic and diastolic flow volume in each cardiac cycle in pump and descending thoracic aorta flow was calculated. Results: (1) Average flow rates – Pulmonary artery and descending thoracic aorta flow rates increased with heart rate during exercise and there was no difference between groups. (2) Pump flow wave – Pump regurgitation increased temporally during exercise at both PFRs, but sustained incidences of regurgitation after exercise were only observed at low PFR. Systolic and diastolic pump flow volume decreased during exercise at both PFRs, but systolic volume increased and diastolic volume decreased significantly after exercise at low PFR. (3) Descending thoracic aorta flow wave – At high PFR, systolic volume of descending thoracic aorta increased but diastolic flow volume decreased during exercise. At low PFR, both systolic and diastolic volume of the descending thoracic aorta decreased during exercise, but systolic volume increased and diastolic volume decreased after exercise. Systolic volume of the descending thoracic aorta in low PFR was significantly greater and diastolic volume was less than those in high PFR during and after exercise. Conclusion: Exercise temporarily increases pump regurgitation with continuous flow LVAS support. Average flow rate of the descending thoracic aorta was maintained by compensation from increased heart rate, although the diastolic flow of the descending thoracic aorta decreased after exercise at the lower pump flow rate. Further study will be needed to evaluate whether or not this flow decrease causes hemodynamic and/or an oxygen delivery mismatch to peripheral tissue.

Key Words: Left ventricular assist device • Continuous flow • Regurgitation • Exercise • Heart failure