Henrik Casimir-Ahn

When do cerebral emboli appear during open heart operations? A transcranial Doppler study

The transcranial Doppler technique enabled the detection of cerebral air emboli in 10 of 10 patients during open-heart valve operations despite standard deairing procedures. With this technique, the occurrence of emboli in the right middle cerebral artery was followed continuously in patients undergoing aortic or mitral valve replacement. Membrane oxygenators were used. Scattered emboli were observed during the insertion of the aortic cannula, at the start of cardiopulmonary bypass, and after the declamping of the aorta with the heart beating while empty. During the period of aortic cross-clamping, no emboli were detected. Despite careful deairing procedures, the recordings indicated a large amount of emboli during filling of the empty beating heart in all 10 patients. Thus, this study indicates that cerebral emboli in open heart procedures are most likely to occur during the redistribution of blood from the heart-lung machine to the patient when the heart is beginning to eject actively, despite careful standard deairing procedures. Meticulous deairing before declamping the aorta is strongly advocated. In addition, a short period of filling of the beating heart before final closure of the aortic incision or vent may decrease the incidence of cerebral emboli. A concomitant reduction in cerebral blood flow by hyperventilation or anesthetics or both during filling of the empty beating heart may also be beneficial.

HeartMate Left Ventricular Assist Device as Bridge to Heart Transplantation

BACKGROUND Because of the limited supply of donor hearts, prospective recipients continue to die while on the waiting list for heart transplantation. Use of long-term mechanical circulatory support devices as a bridge to transplantation may reduce this mortality. However, with the present state of technology, continued clinical evaluation of the various long-term, mechanical circulatory support devices available is mandatory. METHODS Sixteen patients were bridged with the HeartMate left ventricular assist device (LVAD) to heart transplantation for New York Heart Association functional class IV cardiac failure. Twelve pneumatic and six electric devices were used. The mean cardiac index and the mean pulmonary vascular resistance of the patient cohort were 1.71 x min(-1) x m(-2) and 3.1 Wood units, respectively. RESULTS The mean LVAD support time per transplanted patient was 237 days, with a cumulative LVAD support time of about 7.2 years. Bleeding was the main operative and postoperative complication. Two patients suffered from neurologic complications and there were two major incidents of device malfunction. Twelve patients (75%) now have received a transplant, 3 (19%) are awaiting a transplant, and in 1 patient (6%), the device was explanted after spontaneous left ventricular recovery. Eleven of the 12 patients who received a transplant are alive and doing well. The HeartMate LVAD gave adequate circulatory support over extended periods of time and reversed the vital organ dysfunction. Since the start of the LVAD program, only 1 patient has died on our heart transplantation waiting list, compared to nine deaths in the 2 preceding years. CONCLUSIONS The HeartMate LVAD bridge to heart transplantation can be performed with low post-LVAD implantation and posttransplantation mortality and offers 1- and 2-year posttransplantation actuarial survival rates comparable to those for nonbridged heart transplant recipients.

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.

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.

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.

Analysis and processing of laser Doppler perfusion monitoring signals recorded from the beating heart

Laser Doppler perfusion monitoring (LDPM) can be used for monitoring myocardial perfusion in the non-beating heart. However, the movement of the beating heart generates large artifacts. Therefore the aim of the study was to develop an LDPM system capable of correlating the laser Doppler signals to the cardiac cycle and to process the signals to reduce the movement artifacts. Measurements were performed on three calves, both on the normal beating heart and during occlusion of the left anterior descending coronary artery (LAD). The recorded LDPM signals were digitally processed and correlated to the sampled ECG. Large variations in the output (perfusion) and DC signals during the cardiac cycle were found, with average coefficients of variation of 0.36 and 0.14 (n-14), respectively. However, sections with a relatively low, stable output signal were found in late diastole, where the movement of the heart is at a minimum. Occlusion of the LAD showed the importance of recording the laser Doppler signals at an appropriate point in the cardiac cycle, in this case late systole, to minimise movement artifacts. It is possible to further reduce movement artifacts by increasing the lower cutoff frequency when calculating the output signal.

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.

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 patients 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.

Long-term follow-up of patients treated with an implantable left ventricular assist device as an extended bridge to heart transplantation

Four patients were given the TCI implantable left ventricular assist device as a bridge to heart transplantation. The median treatment time was 541 days (range 462 to 873 days), with a total of 2,417 treatment days. The patients were followed with exercise tests and echocardiography 3 to 18 months after implantation. An invasive method was used for quantification of inflow valve incompetence.

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

Abstract 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 β-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 β-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 β-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 β-blocker is outlined. Multiple-vessel CABG on the beating heart was performed with maintenance of an acceptable hemodynamic situation.