Myocardial perfusion monitoring during coronary artery bypass using an electrocardiogram-triggered laser Doppler technique.

Electrocardiogram (ECG)-triggered laser Doppler perfusion monitoring (LDPM) was used to assess myocardial perfusion, with minimum myocardial tissue motion influence, during coronary artery bypass grafting (CABG). Thirteen subjects were investigated at six phases: pre- and post-CABG; post aorta cross-clamping; pre and post left internal mammary artery (LIMA) graft declamping; and post aorta declamping. The perfusion signal was calculated in late systole and late diastole, with expected minimum tissue motion, and compared with arrested heart measurements. Patient conditions or artifacts caused by surgical activity made it impossible to perform and analyse data in all six phases for some patients. No significant (n = 5) difference between perfusion signals pre- and post-CABG was found. Diastolic perfusion signal levels were significantly (p < 0.02) lower compared with systolic levels. After aorta cross-clamping, the signal level was almost zero. A distinct perfusion signal increase after LIMA and aorta declamping, compared with pre-LIMA declamping, was found in ten cases out of 13. A significantly (p < 0.04) lower perfusion signal in the arrested heart compared with in the beating heart was registered. Influence from mechanical ventilation was observed in 14 measurements out of 17. In conclusion, ECG-triggered LDPM can be used to assess myocardial perfusion during CABG. Perfusion signals were lower in the arrested heart compared with in the beating heart and in late diastole compared with late systole. No significant difference between pre- and post-CABG was found.

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.

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.

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.

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.

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.

Video-assisted coronary bypass grafting on the beating heart.

BACKGROUND: Concepts to make coronary artery bypass operations less invasive include minimization of access incisions, elimination of cardiopulmonary bypass, and no manipulation of the aorta. A spectrum of minimally invasive coronary bypass procedures now exist that eliminate the median sternotomy (port-access approach), cardiopulmonary bypass ("off-pump bypass"), or both (minimally invasive direct coronary artery bypass procedure). Although all have advantages in decreasing the morbidity of myocardial revascularization, significant limitations exist including surgeon experience, access, exposure, visualization, hemodynamic support, and technique of anastomosis. METHODS: In an attempt to extend the applicability of the current minimally invasive techniques, efforts are being made both to extend the indications for the procedure as well as to modify the technical aspects. Our current experimental protocol involves a ports-only approach with three-dimensional video imaging, percutaneous Hemopump circulatory support, Octopus coronary immobilization, and an endoscopically sutured coronary anastomosis. RESULTS: In a series of animal studies we have been able to successfully accomplish a totally endoscopic coronary artery bypass procedure on a beating heart without cardiopulmonary bypass. CONCLUSIONS: Although endoscopic coronary artery bypass without cardiopulmonary bypass is possible, many technical challenges remain. Three-dimensional video imaging, wall motion immobilization and presentation, and an axial-flow device can facilitate the procedure. Future enabling technology including motion robotics and nonvisual imaging systems may ultimately further minimize the invasiveness of surgical myocardial revascularization.

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.

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.

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.

Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging.

Tissue motion of the beating heart generates large movement artifacts in the laser Doppler perfusion monitoring (LDPM) signal. The aim of the study was to use tissue Doppler imaging (TDI) to localise intervals during the cardiac cycle where the influence of movement artifacts on the LDPM signal is minimum. TDI velocities and LDPM signals were investigated on three calves, for normal heartbeat and during occlusion of the left anterior descending coronary artery. Intervals of low tissue velocity (TDIint, < 1 cm s(-1)) during the cardiac cycle were identified. During occlusion, these intervals were compared with low LDPM signal intervals (LDPMint, <50% compared with baseline). Low-velocity intervals were found in late systole (normal and occlusion) and late diastole (normal). Systolic intervals were longer and less sensitive to heart rate variation compared with diastolic ones. The overlap between LDPMint and TDIint in relation to TDIint length was 84+/-27% (n = 14). The LDPM signal was significantly (p < 0.001, n = 14) lower during occlusion if calculated during minimum tissue motion (inside TDIint), compared with averaging over the entire cardiac cycle without taking tissue motion into consideration. In conclusion, movement artifacts are reduced if the LDPM signal is correlated to the ECG and investigated during minimum wall motion. The optimum interval depends on the application; late systole and late diastole can be used.

Quantitative data analysis for exploring outcomes in cardiac surgery.

The article focuses on possibilities of statistical knowledge exploration to predict outcomes of surgical treatments. The outcomes were defined in relation to the measured peri- and intraoperative data, as well as follow-up patient questionnaire. Clinical consequences are expected in terms of a smaller data set with a better ability to predict the surgery outcomes and a better cost performance. The important questions that could discriminate quality of life (QoL) were: Relief from surgery?, Has cardiac surgery effected earlier symptoms? Work capacity? Consultations after the surgery? The performed data analysis proved to be efficient in the complex data set that was collected. Pain relief was identified to be significant, while relations between measured blood laboratory profile and later QoL were weak.

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.

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.