Brad Rasmusson

Multicenter experience : Prevention and management of left ventricular assist device infections

Implantable left ventricular assist devices (LVADs) have demonstrated clinical success in both the bridge-to-transplantation and destination-therapy patient populations; however, infection remains one of the most common causes of mortality during mechanical circulatory support. Thus, serious LVAD infections may negate the benefits of LVAD implantation, resulting in decreased quality of life, increased morbidity and mortality, and increased costs associated with implantation. Prevention of device-related infection is crucial to the cost–effective use of mechanical circulatory support devices. Therefore, adherence to evidence-based infection control and prevention guidelines, meticulous surgical technique and optimal postoperative surgical site care form the foundation for LVAD associated infection prevention.

Improving outcomes with long-term “destination” therapy using left ventricular assist devices

OBJECTIVE Destination therapy experience using long-term left ventricular assist devices was analyzed relative to the benchmark Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure trial to evaluate the potential for improving outcomes with this groundbreaking therapy for advanced heart failure. METHODS The largest single-center experience with destination therapy in the United States (Utah Artificial Heart Program, LDS Hospital, Salt Lake City, UT) was retrospectively analyzed. All destination therapy recipients (n = 23) presented with chronic, advanced heart failure, meeting indications for destination therapy adopted from the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure trial. All received HeartMate left ventricular assist devices (Thoratec Corp, Pleasanton, Calif), with 87% receiving an improved XVE model. Advanced practice guidelines were implemented using a multidisciplinary approach. Survivals (Kaplan-Meier, log-rank analyses) and adverse events (Poisson regression) were compared with those of the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure left ventricular assist device group (n = 68). RESULTS Survival in the destination therapy group was significantly increased (P = .007), with an overall reduction in mortality of 66%. The 2-year survival was 77% for destination therapy compared with 29% for the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure left ventricular assist device group (P < .0001). The 1-year survival was 77% for destination therapy compared with the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure left ventricular assist device rate of 52% (P = .036). Adverse events decreased by 38% (3.90 per patient-year in the destination therapy group compared with the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure left ventricular assist device rate of 6.32). Factors related to severity of illness met Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure-like criteria for both groups. CONCLUSIONS This analysis provides evidence that long-term destination therapy can be improved well beyond the pioneering experience of the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure trial. With continued evolution of devices, management, and patient selection, outcomes approaching those of heart transplantation may be possible.

Outcome of noncardiac surgery in patients with ventricular assist devices.

An increasing number of patients are living with ventricular assist devices (VADs). Many of these patients will require noncardiac surgery for conditions not directly related to their VADs. The aim of this study was to assess the risks and outcomes of noncardiac surgery in these patients. Perioperative and follow-up data from patients with VADs who underwent noncardiac surgery from 1993 to 2006 were analyzed. In that period, 184 VADs were implanted in 155 patients. Thirty-seven patients (24%) subsequently underwent 59 noncardiac surgeries. The mean duration of VAD support before surgery was 229 days. Bleeding was the most common postsurgical complication (10%), necessitating reexploration in 20% of abdominal surgeries. Thirty-day mortality was 12%. No deaths were caused by direct complications of surgery. Successful transplantation occurred in 72% of bridge to transplantation patients who required noncardiac surgery, compared with 71% of these patients who did not require noncardiac surgery (relative risk 1.0, p = 0.9). The average duration of VAD support after noncardiac surgery for destination therapy patients was 324 days, most of which time was spent at home. In conclusion, outcomes after noncardiac surgery in patients with VADs are favorable, and most patients continue to benefit from the intended purpose of mechanical circulatory support after recovering from noncardiac surgery.

Electromagnetic interference of automatic implantable cardioverter defibrillator and HeartWare left ventricular assist device.

The use of continuous-flow left ventricular assist devices (LVAD) have markedly improved outcomes in patients with advanced heart failure (HF). The HeartWare LVAD is a miniaturized centrifugal pump implanted within the pericardial space. Implantable cardioverter-defibrillators (ICDs) are susceptible to oversensing of extracardiac signals (electromagnetic interference [EMI]). We report two cases of EMI in patients that received a HeartWare LVAD as destination therapy for advanced HF. The patients were 75 and 78 years old, both with severe ischemic dilated cardiomyopathy (ejection fraction < 0.20) and New York Heart Association class 4 heart failure. Both patients had a St. Jude Medical Unify ICD with a 7 Fr dual coil St. Jude Medical Durata ICD lead. In both patients, the lead location was in the right ventricular apex with an inferior orientation. Both patients experienced immediate ICD therapies after LVAD placement, requiring the tachytherapies to be disabled. ICD programming changes to increase sensitivity and the detection windows were ineffective. Both patients underwent ICD system revision. In one patient, the existing lead was moved to an anteroseptal location that stopped the EMI. In the other patient, the ICD system was changed to allow a separate right ventricular sensing lead in an anteroseptal location and a dual coil ICD lead placed in an apical location, a strategy used to obtain an acceptable defibrillation threshold. The patients have had no subsequent EMI detected on clinical and remote monitoring. Patients with a right ventricular apical ICD lead placement that undergo placement of a HeartWare LVAD are susceptible to EMI and inappropriate ICD therapies. These cases suggest the primary mechanism is proximity of the ICD lead to the device and as such relocation to an anteroseptal location can overcome the problem. These data suggest that all patients that receive a HeartWare LVAD with an ICD should have the device carefully checked at maximum LVAD output to determine if EMI may be present. ASAIO Journal 2013;59:136–139. Key Words: left ventricular assist device, electromagnetic interference, improper ICD shocks, end-stage heart failure.

Lactic acidosis after cardiac transplantation: foe or common innocent bystander?

Background Lactic acidosis (LA) frequently occurs after heart transplantation (HTx). It is hypothesized to be related to inotropic support or metabolic derangements from chronic heart failure. As such, restoring hemodynamic stability with mechanical circulatory support before HTx should mitigate this problem. Our aim was to evaluate the incidence and outcomes of LA after HTx. Methods We evaluated HTx recipients January 2000 to May 2011. Post-HTx outcomes included graft dysfunction, length of intensive care unit stay, length of hospital stay, inotropic support, and survival. Results Of 143 eligible patients, 98.6% had LA, 67% severe, after HTx. Data were analyzed based on the severity of LA. Time to peak lactate, intensive care unit stay, length of hospital stay, peak glucose, inotropic dose, graft dysfunction, and survival after HTx were similar between groups. Statistically significant differences included pretransplant support (25.6% mechanical circulatory support in nonsevere vs. 44.9% severe LA), hospitalization at the time of HTx (37.2% vs. 21.4%), glucose at the time of peak lactate (182.88 ± 69.80 vs. 221.31 ± 56.91), ischemic time (187.4 ± 63.1 vs. 215.5 ± 68.1), and duration of inotrope. Conclusion Severe LA is common after HTx, though it appears to be transient and benign. Mechanical circulatory support after HTx does not prevent LA. High lactate levels are associated with longer ischemic times, longer duration of inotrope, and correspond with higher glucose levels. The underlying mechanism is yet to be satisfactorily elucidated.

Noninvasive predictor of HeartMate XVE pump failure by neural network and waveform analysis.

Patients increasingly require longer durations of left ventricular assist device (LVAD) therapy. Despite a recent trend toward continuous flow VADs, the HeartMate XVE is still commonly used, but its longevity remains a significant limitation. Existing surveillance methods of pump failure often give inconclusive results. XVE electrical current waveforms were collected regularly (2001–2008) and sorted into quartiles according to number of days until pump failure (Q1, 0–34; Q2, 34–160; Q3, 160–300; and Q4, 300–390 days). Thoratec waveform files were converted into text files. The 10-second electrical current, voltage waveform was identified and isolated for analysis. Waveforms were analyzed by principal component analysis (PCA) and with a fast Fourier transform. Quartiles were compared with analysis of variance (ANOVA). Waveforms (n = 454) were collected for 21 patients with failed pumps. An artificial neural network was used to predict pump failure within 30 days from the waveform characteristics identified though signal processing.