Use of continuous flow ventricular assist devices in patients with heart failure and a normal ejection fraction: a computer-simulation study.

Continuous flow left ventricular assist devices are used in end-stage systolic heart failure. However, about one half of the patients with heart failure exhibit diastolic dysfunction with a normal ejection fraction. In the present study, the possible hemodynamic consequences of continuous flow left ventricular assist devices use for these patients were investigated. A previously developed cardiovascular model was modified to reproduce the peculiar hemodynamics of heart failure with a normal ejection fraction. The model was based on and validated with patient data derived from the published data. A continuous flow left ventricular assist device model was included and the hemodynamic effects of pump support evaluated at rest and during exercise. The model accurately reproduced the published data both at rest and during exercise, leading to simulated hemodynamic values within the standard deviations of patient variability. At rest, pump support decreased the end-diastolic left ventricular pressure (6 vs 15 mm Hg) and volume (88 vs 135 mL). During exercise, maximal pump support substantially unloaded the left ventricle (end-diastolic pressure, 14 vs 35 mm Hg; volume, 133 vs 158 mL) and the pulmonary venous circulation (left atrial pressure, 12 vs 24 mm Hg) and resulted in a slight increase in cardiac output (11.7 vs 9.9 L/min). The simulation results suggested that continuous flow left ventricular assist devices improve the hemodynamics in patients with heart failure and a normal ejection fraction. For an optimal use of continuous flow left ventricular assist devices, low speeds should be maintained at rest, to avoid suction. However, during physical activity, higher speeds are needed to prevent an abnormal increase in the ventricular filling pressures typical of patients with heart failure and a normal ejection fraction.

Moscato F ，Wirrmann C ，Granegger M ，Eskandary F ，Zimpfer D ，Schima H ... -  《-》

Hemodynamic effects of partial ventricular support in chronic heart failure: results of simulation validated with in vivo data.

Morley D ，Litwak K ，Ferber P ，Spence P ，Dowling R ，Meyns B ，Griffith B ，Burkhoff D ... -  《-》

Physiology of the native heart and Thermo Cardiosystems left ventricular assist device complex at rest and during exercise: implications for chronic support.

Branch KR ，Dembitsky WP ，Peterson KL ，Adamson R ，Gordon JB ，Smith SC Jr ，Jaski BE ... -  《JOURNAL OF HEART AND LUNG TRANSPLANTATION》

Improved left ventricular unloading and circulatory support with synchronized pulsatile left ventricular assistance compared with continuous-flow left ventricular assistance in an acute porcine left ventricular failure model.

Controversy exists regarding the optimal pumping method for left ventricular assist devices. The purpose of this investigation was to test the hypothesis that pulsatile left ventricular assist synchronized to the cardiac cycle provides superior left ventricular unloading and circulatory support compared with continuous-flow left ventricular assist devices at the same level of ventricular assist device flow. Seven male pigs were used to evaluate left ventricular assist device function using the TORVAD synchronized pulsatile-flow pump (Windmill Cardiovascular Systems, Inc, Austin, Tex) compared with the Bio-Medicus BPX-80 continuous-flow centrifugal pump (Medtronic, Inc, Minneapolis, Minn). Experiments were carried out under general anesthesia, and animals were instrumented via a median sternotomy. Hemodynamic measurements were obtained in the control state and with left ventricular assistance using the TORVAD and BPX-80 individually. Left ventricular failure was induced with suture ligation of the mid-left anterior descending coronary artery, and hemodynamic measurements were repeated. During left ventricular assist device support, mean aortic pressure and total cardiac output were higher and left atrial pressure was lower with pulsatile compared with continuous flow at the same ventricular assist device flow rate. During ischemic left ventricular failure, pulsatile left ventricular support resulted in higher total cardiac output (5.58 ± 1.58 vs 5.12 ± 1.19, P < .05), higher mean aortic pressure (67.8 ± 14 vs 60.2 ± 10, P < .05), and lower left atrial pressure (11.5 ± 3.5 vs 13.9 ± 6.0, P < .05) compared with continuous flow at the same left ventricular assist device flow rate. Synchronized, pulsatile left ventricular assistance produces superior left ventricular unloading and circulatory support compared with continuous-flow left ventricular assist at the same flow rates.

Letsou GV ，Pate TD ，Gohean JR ，Kurusz M ，Longoria RG ，Kaiser L ，Smalling RW ... -  《-》

Exercise hemodynamics in patients with and without diastolic dysfunction and preserved ejection fraction after myocardial infarction.

Andersen MJ ，Ersbøll M ，Bro-Jeppesen J ，Gustafsson F ，Hassager C ，Køber L ，Borlaug BA ，Boesgaard S ，Kjærgaard J ，Møller JE ... -  《-》