Continuous flow (CF) left ventricular assist devices (LVAD) support diminishes vascular pressure pulsatility. Despite its recent clinical success CF LVAD support has been associated with a higher incidence of gastrointestinal bleeding, aortic valve dysfunction and hemorrhagic strokes. To overcome this limitation, we are developing algorithms to provide vascular pulsatility using a CF LVAD. The effects of timing and synchronizing the CF LVAD flow modulation to the native myocardium, modulation amplitude, and modulation widths were studied on the native ventricle and vasculature using a computer simulation model of the circulatory system simulating heart failure. A total of over 150 combinations of varying pulse widths, beat frequencies, time shifts, and amplitudes to modulate CF LVAD flow were tested. All control algorithms maintained a mean CF LVAD flow of 5.0 ± 0.1 L/min (full support) or 2.5 ± 0.1 L/min (partial support). These algorithms resulted in an increased arterial pressure pulsatility of up to 59 mmHg, reduced left ventricular external work (LVEW) by 10-75%, and increased myocardial perfusion by up to 44% from baseline heart failure condition. Importantly, reduction in LVEW and increase in pulsatility may be adjusted to userdefined values while maintaining the same average CF LVAD flow rate. These methods of CF LVAD flow modulation may enable tailored unloading of the native ventricle to provide rest and rehabilitation (maximal unloading to rest followed by gradual reloading to wean), which may promote sustainable myocardial recovery. Further, these LVAD flow modulation patterns may reduce the incidence of adverse events associated with the CF LVAD therapy by increasing vascular pulsatility.
Unlike the lung allocation score, currently, there is no quantitative scoring system available for patients on heart transplant waiting list. By using United Network for Organ Sharing (UNOS) data, we aim to generate a scoring system based on the recipient and donor risk factors to predict posttransplant survival. Available UNOS data were queried between 2005 and 2013 for heart transplant recipients aged ≥18 years to create separate cox-proportional hazard models for recipient and donor risk scoring. On the basis of risk scores, recipients were divided into five groups and donors into three groups. Kaplan-Meier curves were used for survival. Total 17,131 patients had heart transplant within specified time period. Major factors within high-risk groups were body mass index > 30 kg/m (46%), mean pulmonary artery pressure >30 mmHg (65%), creatinine > 1.5 mg% (63%), bilirubin > 1.5 mg% (54%), noncontinuous-flow left ventricular assist devices (45%) for recipients and gender mismatch (81%) and ischemia time >4 hours (88%) for donors. Survival in recipient groups 1, 2, 3, 4, and 5 at 5 years was 81, 80, 77, 74, and 62%, respectively, and in donor groups 1, 2, and 3 at 5 years was 79, 77, and 70%, respectively (p < 0.001). Combining donor and recipient groups based on scoring showed acceptable survival in low-risk recipients with high-risk donor (75% at 5 years). A higher recipient and donor risk score are associated with worse long-term survival. A low-risk recipient transplanted with high-risk donor has acceptable survival at 5 years, but high-risk recipient combined with a high-risk donor has marginal results. Using an objective scoring system could help get the best results when utilizing high-risk donors.
Continuous flow (CF) left ventricular assist devices (LVAD) diminish vascular pressure pulsatility, which may be associated with clinically reported adverse events including gastrointestinal bleeding, aortic valve insufficiency, and hemorrhagic stroke. Three candidate CF LVAD pump speed modulation algorithms designed to augment aortic pulsatility were evaluated in mock flow loop and ischemic heart failure (IHF) bovine models by quantifying hemodynamic performance as a function of mean pump speed, modulation amplitude, and timing. Asynchronous and synchronous copulsation (high revolutions per minute [RPM] during systole, low RPM during diastole) and counterpulsation (low RPM during systole, high RPM during diastole) algorithms were tested for defined modulation amplitudes (±300, ±500, ±800, and ±1,100 RPM) and frequencies (18.75, 37.5, and 60 cycles/minute) at low (2,900 RPM) and high (3,200 RPM) mean LVAD speeds. In the mock flow loop model, asynchronous, synchronous copulsation, and synchronous counterpulsation algorithms each increased pulse pressure (ΔP = 931%, 210%, and 98% and reduced left ventricular external work (LVEW = 20%, 22%, 16%). Similar improvements in vascular pulsatility (1,142%) and LVEW (40%) were observed in the IHF bovine model. Asynchronous modulation produces the largest vascular pulsatility with the advantage of not requiring sensor(s) for timing pump speed modulation, facilitating potential clinical implementation.
Heart failure (HF) is increasing worldwide and represents a major burden in terms of health care resources and costs. Despite advances in medical care, prognosis with HF remains poor, especially in advanced stages. The large patient population with advanced HF and the limited number of donor organs stimulated the development of mechanical circulatory support (MCS) devices as a bridge to transplant and for destination therapy. However, MCS devices require a major operative intervention, cardiopulmonary bypass, and blood component exposure, which have been associated with significant adverse event rates, and long recovery periods. Miniaturization of MCS devices and the development of an efficient and reliable transcutaneous energy transfer system may provide the vehicle to overcome these limitations and usher in a new clinical paradigm in heart failure therapy by enabling less invasive beating heart surgical procedures for implantation, reduce cost, and improve patient outcomes and quality of life. Further, it is anticipated that future ventricular assist device technology will allow for a much wider application of the therapy in the treatment of heart failure including its use for myocardial recovery and as a platform for support for cell therapy in addition to permanent long-term support.
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