John Woodard

A Prospective, Multicenter Trial of the VentrAssist Left Ventricular Assist Device for Bridge to Transplant : Safety and Efficacy

BACKGROUND The increasing prevalence of chronic heart failure has stimulated the ongoing development of left ventricular assist devices (LVADs) for both bridge-to-transplant (BTT) and destination therapy (DT). The aim of this prospective, multicenter clinical trial was to determine the efficacy and safety of a third-generation LVAD, the VentrAssist, in a BTT cohort. METHODS Patients (n = 33) with end-stage chronic heart failure who required circulatory support as BTT therapy were implanted with a VentrAssist device. The primary outcome was survival until transplant or transplant eligibility with the device in situ at trial end-point (Day 154 after implant). The secondary outcomes were pump flow index and end-organ function. Safety, patient functional status and resource use were also assessed. RESULTS At trial end-point, the success rate was 82% (39.4% transplanted, 42.4% transplant-eligible). The LVAD pump flow index (median >or=2.7 liters/min/m(2)) was sufficient to maintain an adequate circulation and significantly improve end-organ function. Of the 77 protocol-defined serious adverse events, most occurred within 30 days of implantation. No patients died as a direct result of pump failure or malfunction. After implantation, patient functional status improved, with 70% of patients achieving hospital discharge, and resource use was reduced. CONCLUSIONS This trial demonstrated a favorable efficacy and safety profile for use of the VentrAssist LVAD in BTT patients.

Effect of alteration in pump speed on pump output and left ventricular filling with continuous-flow left ventricular assist device

Third-generation continuous-flow left ventricular assist devices (LVAD) provide reduced pulsatility flow. We examined the safe working range for LVAD pump speed and the effect on pump output and cardiac function in 13 stable outpatients with VentrAssist-LVAD (Ventracor Ltd, Australia). Pump speed was decreased from a baseline mean of 2,073 ± 86 revolutions per minute (RPM, with corresponding mean flow of 5.59 ± 1.18 L/min, mean ± standard deviation) to an average low-speed of 1,835 ± 55 RPM (corresponding flow 4.68 ± 0.99 L/min) and up to high-speed of 2,315 ± 66 RPM (corresponding flow 6.30 ± 1.29 L/min). There was a strong linear relationship between alteration in speed and flow rates (r2 = 0.89, p < 0.00001) but marked interpatient variation. Downward titration to preset minimum 1,800 RPM was achieved in 9/13 (69%) and upward titration to the preset maximum 2,400 RPM was achieved in 4/13 (31%). Upward titration was stopped due to ventricular suction or nonsustained ventricular tachycardia (VT) in 4/13 (31%). Ventricular suction or VT (in 4/13) tended to be more common in patients with poor right ventricular (RV) function (p = 0.07). In summary, pump flow is stable within a relatively small speed range and should not be altered without close monitoring due to variation in response between patients, particularly with concomitant RV impairment.

Fluid Mechanics of Left Ventricular Assist System Outflow Housings

Using the Novacor (Baxter Novacor, Oakland, CA) Left Ventricular Assist System (LVAS) as a test bed, phasic flow patterns were analyzed for three outflow valve housing designs: 1) a triple sinus; 2) an axisymmetric concentric sinus (CS); and 3) a modified triple sinus (MS). The 21 mm Carpentier-Edwards trileaflet pericardial heart valve prosthesis was used for all experiments done on the three housing designs. The LVAS was actuated by a laboratory model of the Novacor LVAS control console, and it was connected to a mock flow loop with an adjustable afterload system to provide physiologic pressures and flows (Pao, 120/80 mmHg; pump output [PO], 2-6 L/min). Laser illuminated flow visualization techniques were used to investigate the phasic flow patterns of the housings, and the visualization derived velocity was verified by laser Doppler velocimetry at several selected points in the field. Formation of vortices behind the leaflets during the LVAS ejection phase was observed in each of the housing designs. They were well organized, and they circulated with the greatest strength in MS. These vortices tended to lie in a plane parallel to the main flow axis, with the rotational velocity increasing with the stroke volume of the LVAS. In the CS and the MS housings, a circumferential flow that provided good washing of this region was observed behind the stents.

Recovery From Anthracycline Cardiomyopathy After Long-term Support With a Continuous Flow Left Ventricular Assist Device

We report the clinical course of a 16-year-old girl in remission from non-Hodgkins lymphoma who presented in cardiogenic shock due to a severe anthracycline cardiomyopathy. The patient was initially stabilized using central extracorporeal membrane oxygenation support, followed by conversion to a left ventricular assist device. Unexpected evidence of cardiac recovery 9 months after implant enabled device weaning during a 3-month period, culminating in successful device explantation 1 year after implant. The patient survives 18 months after explant in New York Heart Association class I, on conventional heart failure medical management and metabolic therapy.

Twelve-hour reanimation of a human heart following donation after circulatory death.

Despite increasing use of donation after cardiac death (DCD) and encouraging results for non-cardiac transplants, DCD cardiac transplantation has not been widely adopted because, (1) the DCD heart sustains warm ischaemic injury during the death process and (2) conventional static cold storage significantly adds to the ischaemic injury. We have developed a simple system for perfusion of the DCD heart with cold crystalloid solution using gravity-feed that can reduce ischaemic injury and potentially render the heart suitable for transplantation. This report describes the first application of this technique to a human DCD heart with good functional metabolic recovery over 12h on an ex vivo rig.

Impact of Left Ventricular Assist Device Speed Adjustment on Exercise Tolerance and Markers of Wall Stress

Introduction Left ventricular assist devices are crucial in rehabilitation of patients with end-stage heart failure. Whether cardiopulmonary function is enhanced with higher pump output is unknown. Methods 10 patients (aged 39 ± 16 years, mean ± SD) underwent monitored adjustment of pump speed to determine minimum safe low speed and maximum safe high speed at rest. Patients were then randomized to these speed settings and underwent three 6-minute walk tests (6MWT) and symptom-limited cardiopulmonary stress tests (CPX) on separate days. Results Pump speed settings (low, normal and high) resulted in significantly different resting pump flows of 4.43 ± 0.6, 5.03 ± 0.94, and 5.72 ± 1.2 l/min (P<.001). There was a significant enhancement of pump flows (greater at higher speed settings) with exercise (P<0.05). Increased pump speed was associated with a trend to increased 6MWT distance (P = .10); and CPX exercise time (p = .27). Maximum workload achieved and peak oxygen consumption were significantly different comparing low to high pump speed settings only (P<.05). N-terminal-pro-B-type natriuretic peptide release was significantly reduced at higher pump speed with exercise (P<.01). Conclusions We have found that alteration of pump speed setting resulted in significant variation in estimated pump flow. The high-speed setting was associated with lower natriuretic hormone release consistent with lower myocardial wall stress. This did not, however, improve exercise tolerance.