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J Thorac Cardiovasc Surg 2007;133:517-524
© 2007 The American Association for Thoracic Surgery

Cardiopulmonary Support and Physiology

Vascular pulsatility in patients with a pulsatile- or continuous-flow ventricular assist device

^a Cardiovascular Innovation Institute, University of Louisville, Louisville, Ky
^b Institute of Molecular Cardiology, Department of Medicine, University of Louisville, Louisville, Ky
^c Advocate Christ Medical Center, Oak Lawn, Ill
^d Departments of Pediatrics, Surgery and Bioengineering, Penn State College of Medicine, Hershey, Pa
^e The Thoratec Corporation, Pleasanton, Calif

Received for publication July 7, 2006; revisions received July 7, 2006; accepted for publication September 25, 2006.

^_* Address for reprints: Steven C. Koenig, PhD, Cardiovascular Innovation Institute, University of Louisville, 500 South Floyd St, Room 118, Department of Surgery, University of Louisville, Louisville, KY 40202 (Email: sckoen01{at}gwise.louisville.edu).

OBJECTIVE: We sought to investigate differences in indices of pulsatility between patients with normal ventricular function and patients with heart failure studied at the time of implantation with continuous-flow or pulsatile-flow left ventricular assist devices.

METHODS: Eight patients with normal ventricular function and 22 patients with heart failure were studied. A high-fidelity aortic and left ventricular pressure catheter was inserted retrograde through the aortic valve into the left ventricle, and transit-time flow probes were placed on the aorta and device outflow graft. Hemodynamic waveforms were recorded at native heart rate before cardiopulmonary bypass and over a range of device flow rates controlled by adjusting beat rate or rpm. These data were used to calculate vascular input impedance and 2 indices of vascular pulsatility: energy-equivalent pressure and surplus hemodynamic energy.

RESULTS: At low support levels, pulsatile support restored surplus hemodynamic energy to within 2.5% of normal values, whereas continuous support diminished surplus energy by more than 93%. At high support levels, pulsatile support augmented surplus energy by 49% over normal values, whereas continuous support further diminished surplus energy by 97%. Pulsatile support diminished vascular impedance from baseline failure values, whereas continuous support increased impedance. Vascular impedances at baseline for patients undergoing pulsatile and continuous support and during pulsatile support revealed normal vascular compliance, whereas impedance during continuous support indicated a loss of compliance (or "stiffening") of the vasculature.

CONCLUSION: These results suggest that selection of device type and flow rate can influence vascular pulsatility and input impedance, which might affect clinical outcomes.

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