Management of patients with end-stage heart disease treated with an implantable left ventricular assist device in a nontransplanting center.

OBJECTIVE: To describe the setup of a left ventricular assist device (LVAD) program in a nontransplanting center. DESIGN: A prospective study from February 1993 to June 1999. SETTING: A university hospital. PARTICIPANTS: Ten patients, 6 men, with a mean age of 44 years (range 16 to 63 years) and with end-stage heart failure resulting from dilated cardiomyopathy (n = 7) or ischemic heart disease (n = 3). INTERVENTIONS: The patients received the TCI (Thermo Cardiosystems Inc, Woburn, MA) Heart Mate implantable assist device. Five patients had a pneumatic device, and 5 had an electric device. All except 1 patient with an electric device had the pump for an extended period. MEASUREMENTS AND MAIN RESULTS: Median time on the ventilator was 6.2 days, and median time in the ICU was 14 days. Significant hemodynamic improvement was observed by echocardiography and invasive monitoring. Milrinone and epinephrine supplemented by prostaglandin E1 were the most commonly used drugs to avoid right-sided heart failure. Nine patients were transplanted after pump therapy of 241 days (median) (range, 56 to 873 days). One patient died because of endovascular infection and septicemia. Infectious complications were frequent, especially when the pump time was extended. CONCLUSIONS: The introduction of an LVAD program in a nontransplanting center can be achieved with good results. Intense collaboration with a transplant center is mandatory. The complication rate increased when treatment times were extended.

Anesthetic management of patients undergoing coronary artery bypass grafting with the use of an axial flow pump and a short-acting beta-blocker.

OBJECTIVES: To describe the clinical protocol regarding monitoring, pharmacologic interventions, and postoperative care during and after coronary artery bypass grafting (CABG) on the beating heart with an axial flow pump and a short-acting beta-blocker. DESIGN: A retrospective study. SETTING: A university hospital. PARTICIPANTS: Seventeen patients scheduled for elective CABG. INTERVENTIONS: Invasive monitoring was performed with either a standard pulmonary artery catheter (PAC) or a surgically placed PAC. An axial flow pump was inserted through a graft sutured to the ascending aorta. A short-acting beta-blocker was administered to decrease the motion of the heart and make conditions for CABG adequate and safe. MEASUREMENTS AND MAIN RESULTS: Compared with baseline measurements, there were significant decreases in mean arterial blood pressure, mixed venous oxygen saturation, and right ventricular ejection fraction during maximal axial flow pump support and beta-blockade. No significant change in heart rate was observed at this time. Hemodynamic variables were normalized in the intensive care unit. All patients were separated from the Hemopump without inotropic support, and values of troponin-T, aspartate aminotransferase, and alanine aminotransferase were low postoperatively. All patients survived and were discharged from the hospital. CONCLUSION: The anesthetic protocol for patients undergoing surgery with a beating heart and the combined use of an axial flow pump and a short-acting beta-blocker is outlined. Multiple-vessel CABG on the beating heart was performed with maintenance of an acceptable hemodynamic situation.

Initial tests with a new cardiac assist device.

Before, during, and after cardiac intervention, there is occasionally a need for circulatory support because of hemodynamic deterioration. For this purpose, a new minimally invasive cardiac assist device has been developed, and an early prototype has been studied in a bench test and in three pigs. The pump is a catheter system with a distal motor driven propeller (0-15,000 rpm) surrounded by a cage. The catheter was first tested in a tube in a water bath, where efficiency with respect to pressure generation and flow properties was measured. In the pig experiments, the pump was placed in the descending part of the aorta via a graft, and hemodynamic effects were recorded with three different propellers. The bench tests showed a velocity dependent pressure generation in the tube to the second power of the rpm, and 30 cm of water (> 22 mm Hg) could easily be achieved with all propellers. A pressure dependent flow in the tube was observed, with maximum flows of 20 L at 12,000 rpm and 27 L at 15,000 rpm. In the animal experiments, there was a velocity dependent mean pressure difference across the propeller, with up to 48 mm of mercury for the biggest propeller. An increase in cardiac output in all of the pigs was observed as well as a drop in pressure in the proximal part of the aorta. This study demonstrates the efficiency of this new device in vitro and in vivo. Hemodynamic changes are pronounced and are related to the speed and size of the propeller.

Beating heart coronary surgery supported by an axial blood flow pump.

BACKGROUND: We have previously presented a method for performing coronary artery bypass graft operation on the beating heart without cardiopulmonary bypass (CPB). This method has now been explored. METHOD: Thirty-two patients were prospectively randomized. The study group was operated on using an axial blood flow pump (Hemopump; HP) as circulatory support. Operations were performed on the beating heart. The control group was operated on using CPB, aortic cross-clamping, and cardioplegic arrest. RESULTS: All patients went through the procedure without major complications, and were discharged from the hospital. No statistical differences were observed between the groups for time on support (HP, 60.5 minutes; CPB, 70.5 minutes) or total operating time (HP, 178 minutes; CPB, 162 minutes). The number of grafts was greater in the CPB group (HP, 1.8; range, 1 to 3; CPB, 2.5; range, 1 to 4; p = 0.03). Statistical differences were found for intraoperative bleeding (HP mean, 312 mL; CPB mean, 582 mL; p = 0.0003) and myocardial trauma as measured by postoperative troponin-T values (HP, 0.23 microg/L; CPB, 1.17 microg/L; p = 0.004). CONCLUSIONS: Hemopump-supported coronary artery bypass graft operation has been shown to be a safe and feasible procedure with the potential benefits of reduced operative bleeding and myocardial damage without prolonging intraoperative support or total operating time.

Flow characteristics of the Hemopump: an experimental in vitro study.

BACKGROUND: The Hemopump (DLP/Medtronic) has been in clinical use for about 7 years. There is still no adequate way of determining actual output from the three available pump systems in the clinical situation. If the pump is completely stopped during weaning from the device, there is a possibility of back-leakage through the pump, endangering the patient from regurgitation into the left ventricle. It can also make it more difficult to judge the recovery of heart function because of a volume load of the left ventricle. The aim of this study was to evaluate in a standardized, experimental in vitro model the output from three different-sized Hemopump catheters at various pressure levels and to quantify the back-flow through the pumps. METHODS: The Hemopump models were tested in an in vitro study regarding total outflow at various speeds at three pressure levels. The back-flow through the pumps was also measured with the pumps at a complete stop. RESULTS: The outflow from the Hemopumps ranged from 0.4 to 4.5 L/min, depending on which pump and speed were used. Variations in total output, depending on speed and various pressure settings, could be up to 0.4 L/min. Back-flow through the pump into the left ventricle may be as great as 1.6 L/min. CONCLUSIONS: The flow outputs from the different Hemopump models were reproducible over time and were closely related to the resistance of the model. The Hemopump, if not running, can induce substantial regurgitation through the pump into the left ventricle.

Postoperative management of patients with Hemopump support after coronary artery bypass grafting.

BACKGROUND: In this study, we describe postoperative monitoring, pharmacologic therapy, and hemodynamic responses in patients receiving Hemopump support after postcardiotomy heart failure. METHODS: The Hemopump was used in 24 patients with severe left ventricular dysfunction after coronary artery bypass grafting. RESULTS: Fourteen patients (58%) were weaned from the Hemopump. Low to moderate doses of a combination of catecholamines, phosphodiesterase inhibitors, vasodilators, and vasoconstrictors were required to optimize Hemopump function and left ventricular unloading. Mean arterial blood pressure, mixed venous oxygen saturation, and urinary output were the most important therapy guidelines. CONCLUSIONS: Together with our clinical protocol, the Hemopump effectively unloaded the failing ventricle while maintaining vital-organ perfusion. Doses of vasoactive drugs could be kept low. This approach to treatment provides good conditions for recovery of the stunned myocardium.

Hemopump treatment in patients with postcardiotomy heart failure.

BACKGROUND: This study examined the use of the Hemopump to treat low cardiac output syndrome after cardiopulmonary bypass. METHODS: We used the Hemopump temporary cardiac assist system in 29 patients with severe left ventricular dysfunction after open heart operations from September 1991 to November 1994. RESULTS: Five patients were excluded from the study due to initial patient/device-related problems. Ten patients died in the operating room or early during the stay in the intensive care unit due to progressive biventricular failure. Fourteen patients (58.3%) were weaned from the device, and all of them were later discharged. In a subgroup of patients (54%) in whom we had a more aggressive approach for early insertion of the pump, the survival rate was 85%. Preoperative Higging risk score was significantly related to survival. CONCLUSIONS: The Hemopump can effectively unload a failing left ventricle with preservation of multiorgan perfusion. A minor decrease in kidney function was observed in most patients, but none of the surviving patients needed hemodialysis. One patient required a short period of peritoneal dialysis to get rid of fluid overload. Hemolysis or platelet dysfunction was not a clinical problem.

Clinical use of the Hemopump cardiac assist system for circulatory support.

We have used the Hemopump in 15 patients in whom weaning from cardiopulmonary bypass was unsuccessful. The median time for the patients having the device on was 1.6 days postoperatively. They spent an average of 6 days in the intensive care unit and had a total hospital stay of about 17 days. Nine of 15 patients (60%) survived and were able to leave the hospital. There were some reversible decreases in kidney function in all patients, but none of them needed hemodialysis. Coronary artery bypass grafting supported by the Hemopump instead of cardiopulmonary bypass and with the use of a short-acting beta-blocker, esmolol, was carried out successfully in 12 patients. In this method the blood is oxygenated by the patient's lungs and the heart is perfused with its own warm blood. The Hemopump supports the circulation and if the patient needs circulatory support after the operation, a left ventricular assist device is already in place. There were no device-related complications apart from two initial cable fractures. The Hemopump fits well in the intensive care unit environment; it is silent, and the management of the console is easily learned. The Hemopump has shown to be an effective and safe tool for unloading the left ventricle while maintaining multiorgan perfusion. There are several potential applications for surgeons and cardiologists.

The Linköping-Lund surgical experience with the HeartMate left ventricular assist system.

Four transplant candidates fulfilling the Food and Drug Administration criteria for a permanent left ventricular assist device received a pneumatic HeartMate system as a bridge to heart transplantation. All patients survived and were fully rehabilitated at the time of transplantation, which was carried out 2 to 6 months after the initial operation. There were no major complications associated with the procedures. We are impressed by the effectiveness and safety of the device.

Coronary artery operation supported by the Hemopump: an experimental study on pig.

Twelve pigs undergoing coronary artery bypass grafting had the Hemopump to decompress the heart and as circulatory support. The pigs also were given a short-acting beta-blocker, esmolol, to make the heart flaccid. Extracorporeal circulation was not used. During Hemopump support, a bolus dose of 0.5 to 5 mg/kg of esmolol was given before incremental titration steps from 100 to 600 micrograms.kg-1.min-1 over 15 to 20 minutes. The internal thoracic artery was sutured to the distal part of the left anterior descending artery. The Hemopump was withdrawn to the aorta after a weaning period of 20 to 30 minutes. Seven of 12 pigs went through the whole procedure and the Hemopump was weaned off without complications. Five animals died due to right ventricular failure in association with esmolol administration. There was a big interindividual difference in esmolol dose-response curves in the surviving animals. No significant differences in the hemodynamic variables were observed during the experiment. The Hemopump in combination with a short-acting beta-blocker could be an alternate way of performing coronary artery bypass grafting in selected patients.

Coronary artery operation with support of the Hemopump cardiac assist system.

Five patients with one- or two-vessel disease had one to three bypass grafts using the Hemopump cardiac assist system instead of cardiopulmonary bypass to decompress the heart and as circulatory support. In addition, the short-acting beta-blocker esmolol was given as a bolus and stepwise titrated to make the heart flaccid and facilitate operation. All patients had a 24F Hemopump placed into the left ventricle. The patients were given 7,500 U of heparin. Average time on Hemopump support was 56 minutes. All patients went through the procedure uneventfully. Thirty minutes after pump removal all patients were back to baseline hemodynamic values. None of the patients needed blood transfusion. No postoperative renal impairment was seen. This method has great potential and could avoid the drawbacks associated with cardiopulmonary bypass and cardioplegic arrest. Careful evaluation in randomized studies is the next step.