Intuitive use and usability of ventricular assist device peripheral components in simulated emergency conditions.

Ventricular assist devices (VADs) are now increasingly used to prolong the lives of end-stage heart failure patients. These patients vary greatly in age, alertness, activity, and home environment. In daily routine, but especially in emergencies or in conjunction with non-VAD-correlated diseases, the untrained, intuitive use and application of VAD peripherals by relatives, laypersons, and paramedics becomes important. Correct intuitive use may be a matter of life and death. The aim of this study was to evaluate the intuitive usability of these systems and to identify key features needed to optimize intuitive use. Paramedics (n=96) were confronted with a simulated emergency situation involving VAD peripherals mounted on a dummy. Three conditions were simulated: the VAD disconnected from its power source (n=44); both VAD batteries empty (n=44); and a discharged VAD battery mistakenly connected in place of a charged one (n=8). Two VAD systems were assessed: the Heartware HVAD and the Thoratec HeartMate II. An appropriate emergency card developed by our center was available in each case. Actions were videotaped, response times were measured, and a standardized questionnaire was completed after the simulation. The problem was solved by 71% of the participants (HVAD 83%, HMII 60%) with 87% using the emergency card. Only 4% could solve the problem without. Cardiac massage, which was unnecessary, was started by 44%, while 18% complained about unnecessarily difficult conditions (e.g., irritation from the acoustic alarm, complexity of the emergency card, error-prone procedures). Better component labeling (e.g., displays, control elements, connectors) was recommended by 56%. A thoroughly color-coded connection system was especially desired. Cable- and connector-related difficulties were reported by 23%. The study indicated that VAD systems should be self-explaining, with clear labeling of components and connectors, that a clearer emergency card is pivotal and that similar basic handling and emergency procedures for all VAD types would be desirable.

Usability and safety of ventricular assist devices: human factors and design aspects.

The purpose of this study was the investigation of the usability and ergonomics of ventricular assist devices (VADs) in everyday usage. Patients with four different VAD types were observed. After implantation, instruction, and discharge from the hospital, the patients returned on a regular basis to the outpatient clinic, where the investigation took place. Data collection took place in two phases. In phase I home-released VAD patients were asked about perceived problems with the system at home. Additionally health-care professionals were interviewed to gather information on frequent VAD inconveniences and shortcomings. This inquiry resulted in a standardized self-assessment questionnaire and a manual skill test, which were performed in phase II by the whole collective (16 patients and ongoing). As a result, 38% of the patients disconnected parts of their system unintentionally at least once. All of them ascribed this problem to their own carelessness. Thirty-eight percent had to replace a cable. Seventy-five percent desired an additional cable strain relief. Thirty-eight percent suffered from rubbing of parts on the body. Sixty-three percent used a separate repository aside from the factory-provided transportation systems. The overall noise emission (pump, ventilators, and alarms) annoyed 56%; however, for 32% the alarm signals were too quiet to wake them up. No correlation between the assessed manual skills and the number of adverse events was found. To conclude, this preliminary study revealed considerable potential for improvements in the usability of ventricular assist systems.

Low molecular weight heparin as an alternative to unfractionated heparin in the immediate postoperative period after left ventricular assist device implantation.

We present a regimen for anticoagulation in the immediate postoperative period after left ventricular assist device (LVAD) implantation using low molecular weight heparin (LMWH) as an alternative to unfractionated heparin. Between May and September 2007, eight consecutive patients undergoing LVAD implantation for advanced heart failure received the LMWH nadroparin. Nadroparin was given twice daily to achieve anti-Factor Xa activity target peak levels of 0.4 +/- 0.1 U/mL. The antiplatelet therapy consisted of aspirin (100 mg/day) and dipyridamole (3 x 75 mg/day). One patient underwent heart transplantation, three patients died, and four patients continued to receive device support. The median duration of support was 78 days (range, 46 to 174). No major bleeding was observed; minor bleeding occurred in three patients. In two patients, pump thrombosis was suspected. There were two ischemic and no hemorrhagic strokes. The use of LMWH may provide a new anticoagulation treatment option in the immediate postoperative period after LVAD implantation.

Post-transplant survival after lowering fixed pulmonary hypertension using left ventricular assist devices.

OBJECTIVE: We have previously shown that fixed pulmonary hypertension in cardiac transplant candidates can be lowered using left ventricular assist devices (LVADs). The post-transplant survival of these patients is uncertain as pulmonary hypertension may reappear, possibly affecting post-transplant survival. MATERIALS AND METHODS: Between 01/2000 and 01/2005 a total of 26 cardiac transplant candidates (92% male; mean age 56.2 years) in whom fixed pulmonary hypertension was lowered by LVAD implantation (pulmonary vascular resistance (PVR) before implantation: 5.1+/-2.8wood units (WU); PVR before cardiac transplantation: 2.0+/-.9WU) underwent cardiac transplantation at our institution. These patients were age and sex matched with 52 cardiac transplant candidates without pulmonary hypertension undergoing cardiac transplantation during the same time period. Study endpoints were peri-transplant complications and long-term survival. Mean follow-up was 36+/-14 months. RESULTS: Peri-transplant mortality was 5% in patients after LVAD therapy and 7% in patients without prior LVAD therapy (p=.089). We observed 2 cases (4%) of acute right heart failure requiring mechanical support in patients without prior LVAD therapy. None of the patients with LVAD therapy developed peri-transplant right heart failure requiring mechanical support. Incidence of other peri-transplant complications was comparable between the two groups. Log-rank (p=.124) revealed comparable long-term survival between patients with (1 year: 85%, 2 year: 85%, 3 year: 85%) and without (1 year: 90%, 2 year 82%, 3 year prior 79%) prior LVAD therapy. CONCLUSION: LVAD therapy lowers fixed pulmonary hypertension in cardiac transplant candidates with fixed pulmonary hypertension. Thereafter, long-term post-transplant survival is comparable to cardiac transplant recipients without pulmonary hypertension.

Neurocognitive function in patients with ventricular assist devices: a comparison of pulsatile and continuous blood flow devices.

The effect of successful ventricular assist device (VAD) implantation on neurocognitive function in terminal heart failure is uncertain. Additionally, the different impact of continuous versus pulsatile blood flow devices is unknown. A total of 29 patients (mean age 53 years), surviving implantation of a ventricular assist device as bridge to transplantation were prospectively followed (continuous flow: Micromed DeBakey, n = 11; pulsatile flow: Thoratec and Novacor, n = 18). Normative data were obtained in 40 age- and sex-matched healthy subjects (mean age 54 years). Neurocognitive function was objectively measured by means of cognitive P300 auditory evoked potentials before operation (baseline), at intensive care unit (ICU) discharge, and at the 8-week and 12-week follow-up. Before implantation of the VAD, cognitive P300 evoked potentials were impaired (prolonged) compared with age- and sex-matched healthy subjects (p < 0.001). After successful VAD implantation, P300 evoked potentials markedly improved compared with before operation (ICU discharge, p = 0.007; 8-week follow-up, p = 0.022; 12-week follow-up, p < 0.0001). Importantly, there was no difference between continuous and pulsatile VADs (before operation, p = 0.676; ICU discharge, p = 0.736; 8-week follow-up, p = 0.911 and 12-week follow-up, p = 0.397; respectively). Nevertheless, P300 peak latencies did not fully normalize at 12-week follow-up compared with healthy subjects (p = 0.012). Successful VAD implantation improves neurocognitive impairment in patients with terminal heart failure. Importantly, this effect is independent of the type of VAD (pulsatile vs. continuous blood flow).

Extended in vivo evaluation of a miniaturized axial flow pump with a novel inflow cannula for a minimal invasive implantation procedure.

BACKGROUND: Minimally invasive techniques are desirable to minimize surgical trauma during left ventricular assist device (LVAD) implantation. This is particularly challenging for full-flow support. In this study, a minimally invasive implantation technique was developed for a microaxial rotary pump. The system was evaluated in a chronic sheep model. METHODS: A HeartWare MVAD (HeartWare, Miami Lakes, FL) pump (length, 50 mm; diameter, 21 mm; maximum flow, 7-8 liters/min) was combined with a novel inflow cannula, including a new flow-optimized tip. The device was implanted into sheep (range, 60-80 kg, mean, 71.6 ± 6.8 kg) through a right-sided minithoracotomy. The inflow cannula was inserted through the superior pulmonary vein, passing through the left atrium into the left ventricle. Scheduled implant period was 30 days for 8 sheep and 100 days for 3 sheep. Mean support flow was set to half of the nominal cardiac output. RESULTS: Six of 8 sheep finished the scheduled 30-day investigation period (one failed due to early non-pump-related post-operative bleeding and one due to prototype controller failure). The 3 sheep scheduled for 100 days reached the study end point. Peak pump flows of up to 6.9 liters/min were achieved. At necropsy, no signs of mitral valve lesions or thrombus formation around the cannula, the tip, or the insertion site were observed, except for valve leaflet erosion in 1 animal, where the cannula had been entangled in the sub-valvular chords due to lack of ultrasound monitoring. CONCLUSIONS: The minimally invasive implantation technique using the HeartWare MVAD pump, together with a new cannula, provided excellent results in a chronic animal model.

Age and outcome after continuous-flow left ventricular assist device implantation as bridge to transplantation.

OBJECTIVE: The effect of age on outcomes after continuous-flow left ventricular assist device (LVAD) implantation as a bridge to transplantation (BTT) was determined. METHODS: From November 1998 to July 2007, 86 patients with advanced heart failure underwent continuous-flow LVAD implantation as BTT and were retrospectively analyzed. Patients were categorized into 2 groups by age at LVAD implantation: 56 patients (65.1%) younger than 60, Group 1; and 30 (34.9%) aged 60 years or older, Group 2. RESULTS: Group 2 patients had a higher incidence of heart failure caused by ischemic heart disease (63.3% vs 32.1%, p = 0.005) and more severely impaired renal function by Modification of Diet in Renal Disease-derived glomerular filtration rates (51.9 +/- 15.9 vs. 68.0 +/- 20.5 ml/min/1.73 m(2), p < 0.001) than Group 1. Age was the only independent predictor of post-LVAD death (hazard ratio, 1.4 p = 0.003). The BTT rate was lower (33.3% vs 62.5%, p = 0.010), and incidence of post-LVAD renal failure was higher (53.3% vs 30.4%, p = 0.037) in Group 2 vs Group 1. Post-LVAD survival at 1, 3, and 6 months was 92.9%, 79.9%, and 74.0% for Group 1 and 90.0%, 62.0%, and 37.0% for Group 2 (p = 0.007). Post-transplant survival at 1, 3, and 5 years was 87.8%, 82.3%, and 76.0% for Group 1 and 90.0%, 67.5%, 67.5% for Group 2 (p = 0.517). CONCLUSIONS: Patients aged 60 years and older have inferior post-LVAD survival; however, post-transplant survival is excellent. We advocate LVAD placement as bridge-to-transplant therapy only in carefully selected older patients most well suited for transplantation.

Renal function and outcome after continuous flow left ventricular assist device implantation.

BACKGROUND: Renal dysfunction as a risk factor with the use of left ventricular assist devices (LVAD) is controversial. We determined the effect of renal function on outcomes after continuous flow LVAD implantation. METHODS: Eighty-six patients with advanced heart failure undergoing continuous flow LVAD implantation as bridge to transplantation from November 1998 to July 2007 were retrospectively analyzed. Renal function was assessed using the Modification of Diet in Renal Disease study-derived glomerular filtration rates (GFR [mL x min(-1) x 1.73 m(-2)]). Patients were categorized into two groups based on pre-LVAD GFR: those with normal renal function (GFR > 60, n = 46), and those with renal dysfunction (GFR < 60, n = 40). RESULTS: Post-LVAD survival at 1, 3, and 6 months for GFR greater than 60 was 91.3%, 79.9%, 72.6%, respectively, and for GFR less than 60, it was 92.5%, 66.5%, 47.9%, respectively (p = 0.038). Bridge-to-transplant rate was lower for GFR less than 60 than for GFR greater than 60 (40.0% versus 63.0%, p = 0.033). For GFR less than 60, GFR improved on LVAD support: implant to month 6, 41.7 +/- 11.5 to 62.7 +/- 25.0 (p = 0.021). Post-LVAD survival was improved in GFR less than 60 patients who after LVAD implantation recovered renal function to GFR greater than 60 (p < 0.001). Patients with post-LVAD renal failure had significantly lower post-LVAD survival regardless of pre-LVAD renal function (p < 0.001). CONCLUSIONS: Patients with renal dysfunction have poorer outcomes after continuous flow LVAD implantation. However, renal function improves after LVAD implantation and is associated with improved survival. Our data underscore the importance of end-organ function in patient selection for LVAD therapy.

Renal function after implantation of continuous versus pulsatile flow left ventricular assist devices.

BACKGROUND: This study was designed to determine the effect of continuous vs pulsatile flow devices on renal function after left ventricular assist device (LVAD) implantation. METHODS: Ninety-two patients undergoing LVAD implantation as bridge-to-transplant therapy were retrospectively analyzed. Patients receiving continuous flow devices (n = 63, 68.5%) were compared with patients receiving pulsatile flow devices (n = 29, 31.5%). Renal function was assessed by 2 calculated glomerular filtration rates (GFR) using the Modification of Diet in Renal Disease (MDRD)-derived GFR (ml/min/1.73 m(2)) and the Cockcroft-Gault-derived creatinine clearance (CrCl, ml/min). RESULTS: Mean GFR/CrCl was comparable between the groups at LVAD implantation, in the post-implantation period, and at transplantation. Both groups had a significant increase in mean GFR at Week 1 post-implantation (continuous, 59.4 +/- 22.8 to 76.4 +/- 38.6, p = 0.001; pulsatile, 52.5 +/- 21.1 to 69.2 +/- 34.7; p = 0.007), Week 4 (continuous, 59.9 +/- 23.0 to 84.3 +/- 32.9; p < 0.001; pulsatile, 50.3 +/- 21.1 to 79.9 +/- 38.7, p = 0.007), and Week 12 (continuous, 60.3 +/- 23.1 to 75.3 +/- 30.2, p = 0.004; pulsatile, 55.5 +/- 23.1 to 74.2 +/- 27.2, p = 0.037) that was also seen with the Cockcroft-Gault-calculated CrCl. No significant increase occurred in mean GFR/CrCl to transplantation. Incidence of post-implantation renal failure was comparable between the groups (continuous, 38.1%; pulsatile, 31.0%; p = 0.512). CONCLUSIONS: After LVAD implantation, patients with continuous flow devices and patients with pulsatile flow devices have comparable renal function.

Left ventricular assist devices decrease fixed pulmonary hypertension in cardiac transplant candidates.

OBJECTIVE: Fixed pulmonary hypertension is a contraindication for cardiac transplantation because of the increased risk of donor heart failure. We sought to determine whether left ventricular assist devices improve fixed pulmonary hypertension in cardiac transplant candidates to enable safe cardiac transplantation. METHODS: Thirty-five consecutive cardiac transplant candidates (age 56 +/- 6 years, 88.5% were men) with fixed pulmonary hypertension (5.1 +/- 2.6 Wood units) resistant to medical treatment received a left ventricular assist device as a bridge to transplantation. Three left ventricular assist device systems were used (pulsatile blood flow: Novacor [World Heart Inc, Oakland, Calif] n = 8; continuous blood flow: MicroMed DeBakey [MicroMed Technology Inc, Houston, Tex] n = 24, DuraHeart [Terumo Heart Inc, Ann Arbor, Mich] n = 3). Right-sided heart catheter data were obtained before left ventricular assist device implantation at 3-day and 6-week follow-ups. Clinical data and complications were recorded. RESULTS: Before left ventricular assist device implantation, the pulmonary vascular resistance was 5.1 +/- 2.8 Wood units. Values were comparable in patients receiving pulsatile (5.1 +/- 3.4 Wood units) or continuous blood flow left ventricular assist devices (5.1 +/- 2.7 Wood units, P = .976). Left ventricular assist device implantation decreased pulmonary vascular resistance at 3-day (2.9 +/- 1.3 Wood units, P < .0001) and 6-week (2.0 +/- 0.8 Wood units, P < .0001) follow-ups compared with before implantation. This effect was independent of the type of left ventricular assist device system used (3-day follow-up: pulsatile flow: 3.2 +/- 1.3 Wood units vs continuous flow: 2.7 +/- 1.2 Wood units; P = .310 and 6-week follow-up: pulsatile flow: 1.9 +/- 0.9 Wood units vs continuous flow: 2.1 +/- 0.8 Wood units; P = .905). Twenty-four patients had successful bridges to transplantation (69%, mean time on left ventricular assist device 210 +/- 83 days), and 11 patients died before transplantation (31%, mean time on left ventricular assist device 67 +/- 30 days). The 1-year survival after transplantation was 95%. CONCLUSION: Left ventricular assist devices decrease fixed pulmonary hypertension in cardiac transplant candidates and allow patients to overcome a contraindication for cardiac transplantation. Therefore, left ventricular assist devices should be considered in all cardiac transplant candidates with fixed pulmonary hypertension.