Faculty Bibliography

A total artificial heart (TAH) is the sole remaining option for patients with biventricular failure who cannot be rescued by left ventricular assist devices (LVADs) alone. However, the pulsatile TAH in clinical use today has limitations: large pump size, unknown durability, required complex anticoagulation regimen, and association with significant postsurgical complications. That pump is noisy; its large pneumatic driving lines traverse the body, with bulky external components for its drivers. Continuous-flow pumps, which caused a paradigm shift in the LVAD field, have already contributed to the rapidly evolving development of TAHs. Novel continuous-flow TAHs are only in preclinical testing or developmental stages. We here review the current state of TAHs, with recommended requirements for the TAH of the future.

A growing number of solid organ transplant survivors require surgery for cardiac disease. We examined the effect of having a previous transplant on outcomes after cardiac surgery in these patients from a population-based perspective. Of 1,709,735 patients who underwent coronary artery bypass grafting, valve, or thoracic aorta surgery from 2004 to 2008 in the Nationwide Inpatient Sample, 3,535 patients (0.21%) had a previous organ transplant (2,712 kidney, 738 liver, 300 pancreas). Multivariate logistic regression analysis and propensity score matching were used to determine the effect of a previous solid organ transplant on outcomes. In-hospital mortality rate was 7% for patients who underwent transplantation versus 4% for patients who did not undergo transplantation (odds ratio [OR] 1.66, 95% confidence interval [CI] 1.16 to 2.38). Patients who underwent transplantation were at an increased risk for acute renal failure (OR 1.62, CI 1.36 to 1.94) and blood transfusions (OR 1.63, CI 1.36 to 1.95). Median length of stay was longer (10 vs 9 days), with greater median total charges ($111,362 vs $102,221; both p <0.001). Occurrence of stroke, gastrointestinal complication, infection, and pneumonia was similar between groups. In conclusion, previous solid organ transplantation is an incremental risk factor for postoperative mortality after cardiac surgery. Renal protective strategies and bleeding control should be stressed to mitigate complications.

Post-explant evaluation of the continuous-flow total artificial heart in preclinical studies can be extremely challenging because of the device's unique architecture. Determining the exact location of tissue regeneration, neointima formation, and thrombus is particularly important. In this report, we describe our first successful experience with visualizing the Cleveland Clinic continuous-flow total artificial heart using a custom-made high-definition miniature camera.

The biocompatibility assessment of the Cleveland Clinic continuous-flow total artificial heart is an important part of the device developmental program. Surgical and postoperative management are key factors in achieving optimal outcomes. However, the presence of vascular anatomical abnormalities in experimental animal models is often unpredictable and may worsen the expected outcomes. We report a technical impediment encountered during total artificial heart implantation complicated by unfavorable bovine anatomy of the ascending aorta and brachiocephalic arterial trunk.

BACKGROUND: Data from 3 institutions revealed an abrupt increase in HeartMate II (Thoratec) pump thrombosis starting in 2011, associated with 48% mortality at 6 months without transplantation or pump exchange. We sought to discover if the increase occurred nationwide in Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) data, and if so (1) determine if accelerated risk continued, (2) identify predictors, (3) investigate institutional variability, and (4) assess mortality after pump thrombosis. METHODS: From April 2008 to June 2014, 11,123 HeartMate II devices were implanted at 146 institutions. Machine learning, non-parametric Random Forests for Survival was used to explore risk-adjusted thrombosis based on 87 pre-implant and implant variables, including implant date. RESULTS: A total of 995 pumps thrombosed, with risk peaking within weeks of implant. The risk-adjusted increase in pump thrombosis began in 2010, reached a maximum in 2012, and then plateaued at a level that was 3.3-times higher than pre-2010. Pump exchange, younger age, and larger body mass index were important predictors, and institutional variability was largely explained by implant date, patient profile, and duration of support. The probability of death within 3 months after pump thrombosis was 24%. CONCLUSIONS: Accelerated risk of HeartMate II thrombosis was confirmed by Interagency Registry for Mechanically Assisted Circulatory Support data, with risk subsequently leveling at a risk-adjusted rate higher than observed pre-2010. This elevated thrombosis risk emphasizes the need for improved mechanical circulatory support systems and post-market surveillance of adverse events. Clinicians cognizant of these new data should incorporate them into their and their patients' expectations and understanding of risks relative to those of transplantation and continued medical therapy.

The Cleveland Clinic continuous-flow total artificial heart passively regulates itself in regard to the relative performance of systemic and pulmonary pumps. The system incorporates real-time monitoring to detect any indication of incipient left or right suction as input for automatic controller response. To recognize suction, the external controller compares the waveforms of modulating speed input and power feedback. Deviations in periodic waveforms indicate sudden changes to flow impedance, which are characteristic of suction events as the pump speed is modulating. Incipient suction is indicated within 3 seconds of being detected in the power wave form, allowing timely controller response before mean flow is affected. This article describes the results obtained from subjecting the system to severe hemodynamic manipulation during an acute study in a calf.