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EVALUATION OF HEMODYNAMICS IN PATIENTS WITH CONTINUOUS FLOW LEFT VENTRICULAR ASSIST DEVICES
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End-stage heart failure (HF) is characterized by specific hemodynamic abnormalities. These abnormalities are a result of left ventricular (LV) systolic and diastolic dysfunction. This in turn leads to right ventricular (RV) dysfunction due to secondary pulmonary hypertension (PH). Systolic dysfunction in end-stage HF is manifested by low cardiac output and elevated left ventricular end-diastolic pressure (LVEDP) as measured by pulmonary capillary wedge pressure (PCWP). The elevation of PCWP increases pulmonary arterial pressure and hence increases afterload of the RV. In both ischemic and nonischemic cardiomyopathies, RV often has intrinsic contractile dysfunction and its performance is worsened by increased loading due to secondary PH. Left ventricular assist devices (LVADs) have been shown to decrease left ventricular end-diastolic volume and pressure and, in turn, decrease left atrial pressure (LAP) and pulmonary arterial pressure (PAP), while increasing effective cardiac output (CO).
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Currently, the 2 most widely used durable LVADs are HeartMate II (St Jude Medical, Pleasanton, CA) and HeartWare (HVAD, HeartWare Inc., Framingham, MA), both of which are continuous-flow devices (CF-LVAD) (Figure 38-1). Although the 2 devices have a different mechanism of pumping blood—HeartMate II is an axial flow pump and HVAD is an intrapericardial, centrifugal pump—the hemodynamic effects are similar. A newer generation HM III device is currently under investigation.
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For simplicity, this chapter will focus on the hemodynamic effects of continuous-flow LVADs. Furthermore, the role of echocardiography in evaluation of device function will be discussed.
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HEMODYNAMIC EFFECTS OF ...