Faculty Bibliography

BACKGROUND: Left ventricular assist device (LVAD) infections including drivelines, pump pockets, and bacteremia are difficult to manage and conservative treatments may not be effective as the infected foreign material remains. METHODS: We performed a retrospective analysis of all 170 HeartMate II (Thoratec, Pleasanton, CA) implantations as bridge to transplant (BTT) between 2004 and 2012 at our institution. Sixty-one patients (36%) developed a culture positive driveline infection, pump pocket infection, bacteremia, or a combination of these. Twenty-six out of 61 patients with an infection and 49 out of 109 patients without an infection went on to receive a heart transplant. RESULTS: The 1- and 3-year freedom from LVAD infection was 60% and 32%, respectively. While early infection tends to first present as driveline infections, late infections tend to present initially as bacteremia. The 1-year likelihood of receiving a transplant in the patients with an LVAD infection group was 37%, compared with 43% in patients without an infection (p = 0.36). One-year survival to transplantation was 76% in patients with LVAD infection compared with 81% without (p = 0.33). The 1- and 3-year posttransplant survival in patients with a LVAD infection was 96% and 91%, respectively, compared with 92% and 88% in patients without an infection (p = 0.48) . CONCLUSIONS: In this nonmatched cohort of LVAD patients with and without infection, selected patients with controlled LVAD infection have an equal chance of getting transplanted with excellent early and late post-transplant survival.

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.

OBJECTIVE: The Cleveland Clinic continuous-flow total artificial heart (CFTAH) is a compact, single-piece, valveless, pulsatile pump providing self-regulated hemodynamic output to left/right circulation. We evaluated chronic in vivo pump performance, physiologic and hemodynamic parameters, and biocompatibility of the CFTAH in a well-established calf model. METHODS: CFTAH pumps have been implanted in 17 calves total. Hemodynamic parameters, pump performance, and device-related adverse events were evaluated during studies and at necropsy. RESULTS: In vivo experiments demonstrated good hemodynamic performance (pump flow, 7.3 +/- 0.7 L/min; left atrial pressure, 16 +/- 3 mm Hg; right atrial pressure, 17 +/- 3 mm Hg; right atrial pressure-left atrial pressure difference, 1 +/- 2 mm Hg; mean arterial pressure, 103 +/- 7 mm Hg; arterial pulse pressure, 30 +/- 11 mm Hg; and pulmonary arterial pressure, 34 +/- 5 mm Hg). The CFTAH has operated within design specifications and never failed. With ever-improving pump design, the implants have shown no chronic hemolysis. Three animals with recent CFTAH implantation recovered well, with no postoperative anticoagulation, during planned in vivo durations of 30, 90, and 90 days (last 2 were intended to be 90-day studies). All these longest-surviving cases showed good biocompatibility, with no thromboembolism in organs. CONCLUSIONS: The current CFTAH has demonstrated reliable self-regulation of hemodynamic output and acceptable biocompatibility without anticoagulation throughout 90 days of chronic implantation in calves. Meeting these milestones is in accord with our strategy to achieve transfer of this unique technology to human surgical practice, thus filling the urgent need for cardiac replacement devices as destination therapy.

In vivo preclinical testing of mechanical circulatory devices requires large animal models that provide reliable physiological and hemodynamic conditions by which to test the device and investigate design and development strategies. Large bovine species are commonly used for mechanical circulatory support device research. The animals used for chronic in vivo support require high-quality care and excellent surgical techniques as well as advanced methods of postoperative care. These techniques are constantly being updated and new methods are emerging.We report results of our double steel-wire closure technique in large bovine models used for Cleveland Clinic's continuous-flow total artificial heart development program. This is the first report of double-wire sternal fixation used in large bovine models.

OBJECTIVES: Pump-off testing to assess left ventricular recovery is not an option for continuous-flow left ventricular assist devices unless measures are taken to prevent pump regurgitation. The purpose of this bench study was to characterize the hemodynamics and pump flow of the HeartMate II (Thoratec Corp, Pleasanton, Calif) left ventricular assist device at 6000 rpm, the speed commonly used clinically to determine left ventricular recovery. METHODS: The HeartMate II device was operated in a mock loop at 3 speeds (6000, 8000, and 10,000 rpm). We acquired pressure-flow curves in each steady state. In pulsatile mode with the pneumatic ventricle (heart simulator) activated, pump flow, total flow, and aortic pressure data were obtained under conditions simulating normal heart function or heart failure. RESULTS: A large regurgitant flow during diastole was confirmed in normal heart function at 6000 rpm support; however, the net flow was zero, and there were no differences in the mean aortic pressure between 6000 rpm support and no left ventricular assist device support. In contrast, in the heart failure condition, left ventricular assist device flow at 6000 rpm significantly contributed to the mean aortic pressure and total flow because there was less regurgitant flow. CONCLUSIONS: The net pump flow generated by the HeartMate II device at 6000 rpm depends on the degree of residual left ventricular function. In the setting of improved left ventricular function, at 6000 rpm, we noted a large regurgitant flow that reloaded the left ventricle. Although this "marker" can serve as a useful indicator for left ventricular recovery, assessing left ventricular recovery at this speed is flawed unless measures are taken to prevent regurgitant flow.