Haemodynamic and EKG changes in patients undergoing minimally invasive direct coronary artery bypass

BACKGROUND AND OBJECTIVES: The objective of the report is to monitor, in patients undergoing minimally invasive direct coronary artery bypass surgery (MIDCAB), the haemodynamic parameters, ST segment changes and the incidence of arrhythmias during clamping of the coronary artery and following reperfusion. METHODS: Twelve patients scheduled for elective MIDCAB surgery during isoflurane anesthesia were enrolled in the study. Patients were monitored by a pulmonary artery thermodilution catheter, an arterial line and 5 leads ECG. The different haemodynamic parameters, the ST segment changes, as well as the occurrence of arrhythmias during coronary clamping and ten minutes following reperfusion were compared to the control values. RESULTS: No significant changes in the cardiac index followed clamping of the coronary artery. However, the ST segment was significantly elevated. Following coronary reperfusion, the ST segment recovered to the baseline values, and the cardiac index significantly increased more than the baseline value (3.5 +/- 1.1 l/min/m2 vs 2.6 +/- 0.7 l/min/m2). However, reperfusion was associated with multiple ventricular extrasystoles in four patients. The elevation of the ST segments during coronary clamping was higher in the four patients who developed reperfusion arrhythmias (0.9 +/- 0.4 mm); one of the patients had preoperative frequent VPBs, two patients had history of unstable angina, while the fourth patient had 70% proximal stenosis of the LAD and recent myocardial infarction. CONCLUSIONS: Coronary occlusion in patients undergoing MIDCAB can result in ST segment elevation, followed by reperfusion ventricular extrasystoles. The reperfusion arrhythmias were observed in patients showing a significant elevation of the ST segment during coronary occlusion; risk factors included a preoperative history of arrhythmia, unstable angina, recent MI, and/or 70% LAD stenosis. The rapid restoration of the control ST segment level and the significant increase of cardiac output following coronary reperfusion suggest that isoflurane anesthesia may have provided a degree of myocardial protection during coronary clamping and reperfusion.     

Cost-effectiveness of minimally invasive coronary artery bypass surgery.

BACKGROUND: Coronary artery bypass grafting without cardiopulmonary bypass is gaining popularity as an alternative to conventional on-pump technique for myocardial revascularization. This includes minimally invasive direct coronary artery bypass (MIDCAB) and full sternotomy off-pump (OPCAB) methods. These two approaches should be evaluated for financial and clinical appropriateness. METHODS: Records of patients who had single or double bypass (internal mammary artery and/or saphenous vein) grafts between January 1997 and June 1998 were reviewed. These included 44 MIDCAB, 62 OPCAB, and 243 conventional coronary artery bypass (CCAB) patients. Univariate analysis was applied to pre, intra, and postoperative variables, comparing MIDCAB and OPCAB to the CCAB group. Procedural cost information was obtained from participating institutions. RESULTS: MIDCAB patients compared to CCAB patients had a higher predicted risk (5.4+/-11 versus 2.3+/-2.8, p = 0.012) and OPCAB patients had a predicted risk of 5.3+/-7.8. MIDCAB and OPCAB procedures required less operating room time and blood utilization. Observed operative mortality rates were MIDCAB 4.5%, OPCAB 1.6%, and CCAB 2.8% (not significant). Mean hospital costs were CCAB at $19,000, OPCAB at $15,000, and $17,000 for MIDCAB. CONCLUSIONS: Off pump procedures currently reflect acute episode-of-care cost savings over CCAB.     

Reoperative coronary artery bypass grafting using a minimally invasive direct coronary artery bypass procedure

OBJECTIVE: Reoperative coronary artery bypass grafting with cardiopulmonary bypass tends to cause a higher mortality and morbidity than the primary operation. The purpose of this study was to discuss the effectiveness and safety of a minimally invasive coronary artery bypass procedure for patients who had previously undergone coronary artery bypass surgery. METHODS: We performed redo single coronary artery bypass grafting to the left anterior descending coronary artery in 9 patients and to the right coronary artery in 3 patients using minimally invasive cardiac surgery. The graft to the left anterior descending coronary artery was taken from the left internal thoracic artery in 5 patients, the right gastroepiploic artery in 3 patients, and from the saphenous vein in the other 1 patient. The graft to the right coronary artery was from the right gastroepiploic artery in all 3 patients. RESULTS: All grafts were patent. There was no major postoperative complication and no surgical or hospital death except one late death. CONCLUSIONS: In selected patients, we could safely and completely perform coronary artery bypass re-grafting to the left descending coronary artery or right coronary artery using a minimally invasive operation.     

A xiphoid approach for minimally invasive coronary artery bypass surgery.

BACKGROUND: The premise for adopting minimally invasive cardiac surgery techniques for myocardial revascularization is to reduce the patient's morbidity without compromising the efficacy of conventional coronary artery bypass. However, opening the pleura has been a limitation of using these approaches. Aim: We used the xiphoid approach as an alternative to opening the pleura and to minimize pain after minimally invasive coronary artery bypass surgery. METHODS: We review our surgical experience in 55 patients who underwent minimally invasive direct coronary artery bypass (MIDCAB) surgery through a xiphoid approach between October 1997 and August 1999. Thoracoscopy (n = 31) or direct vision (n = 24) were used for internal mammary artery (IMA) harvesting. Mean patient age was 67 +/- 10 years and 65% were men. The mean Parsonnet score was 23 +/- 10. Performed anastomoses included left IMA (LIMA) to the left anterior descending (LAD) artery (n = 53), LIMA-to-LAD and saphenous vein graft from the LIMA to the right coronary artery (n = 1), and LIMA-to-LAD and right IMA (RIMA) to right coronary artery (n = 1). RESULTS: Postoperative complications included atrial fibrillation (12%), acute noninfectious pericarditis (12%), and acute renal failure (5%). Mean postoperative length of stay was 4 +/- 2 days. Angiography was performed in 16 patients and demonstrated excellent patency of the anastomoses. There was no operative mortality. Actuarial survival was 98% in a mean follow-up period of 11 +/- 5 months. CONCLUSIONS: Minimally invasive coronary artery bypass can be performed safely through a xiphoid approach with low morbidity, mortality, and a relatively short hospital stay.     

Comparative economic analyses of minimally invasive direct coronary artery bypass surgery

OBJECTIVE: This study was undertaken to assess the degree to which published cost comparisons of minimally invasive direct coronary artery bypass through a thoracotomy versus conventional coronary artery bypass grafting, off-pump bypass surgery through a sternotomy, or angioplasty with or without stenting adhered to existing guidelines for performing economic analyses. METHODS: We used minimally invasive direct coronary artery bypass (MIDCAB), off-pump bypass surgery, cost-effectiveness, economic analysis, and related keywords to search MEDLINE, other literature databases and article reference lists for English-language economic analyses of minimally invasive direct coronary artery bypass procedures versus other procedures that were published from 1990 to February 2002. We critically appraised article adherence to a 10-item methodologic checklist modified to address issues particularly relevant to minimally invasive direct coronary artery bypass evaluations. Assessment discordance was reconciled by consensus. RESULTS: Ten articles published from June 1997 to March 2001 compared costs and (generally) outcomes of minimally invasive direct coronary artery bypass with those of other procedures. All were nonrandomized comparisons, generally of concurrent intrainstitutional clinical series. Stated results generally favored minimally invasive direct coronary artery bypass, angioplasty, or off-pump bypass surgery through a sternotomy relative to conventional coronary artery bypass grafting. Studies adequately addressed an average of only 24% of applicable checklist items (range 0%-67%). Few studies adequately ensured the comparability of treatment groups, clearly performed intent-to-treat analyses, comprehensively and credibly measured costs that were considered, or clearly addressed costs and results of preprocedural angiography or postprocedural imaging. Only 1 study compared success of revascularization between minimally invasive direct coronary artery bypass and competing alternatives. No studies specified the cost-analysis perspective or included costs of physician or physician assistant care. CONCLUSIONS: Most published comparative economic analyses of minimally invasive direct coronary artery bypass have failed to adequately address issues crucial to such evaluations. Future studies should more closely follow well-described principles of clinical epidemiology and cost-effectiveness analysis.     

Sevoflurane but not propofol preserves myocardial function during minimally invasive direct coronary artery bypass surgery

Volatile anesthetics exert cardioprotective properties in experimental and clinical studies. We designed this study to investigate the effects of sevoflurane on left ventricular (LV) performance during minimally invasive direct coronary artery bypass grafting (MIDCAB) without cardiopulmonary bypass. Fifty-two patients scheduled for MIDCAB surgery were randomly assigned to a propofol or a sevoflurane group. Apart from the anesthetics used, there was no difference in surgical and anesthetic management. After determination of cardiac troponin T, creatine kinase, and creatine kinase MB, electrocardiographic (ECG) data and echocardiography variables (myocardial performance index and early to atrial filling velocity ratio) the left anterior descending coronary artery (LAD) was clamped until anastomosis with the left internal mammary artery was completed. During LAD occlusion and during reperfusion, echocardiography measurements were repeated. Blood samples were obtained repeatedly for up to 72 h. After LAD occlusion, myocardial performance index and early to atrial filling velocity ratio in the propofol group deteriorated significantly from 0.40 +/- 0.12 and 1.29 +/- 0.35 to 0.49 +/- 0.10 and 1.13 +/- 0.22, respectively, whereas there was no change in the sevoflurane group. In the propofol group myocardial performance index remained increased (0.47 +/- 0.11) compared with baseline during reperfusion. There were no significant differences in ECG and laboratory values between groups. In conclusion, during a brief period of ischemia in patients undergoing MIDCAB surgery, sevoflurane preserved myocardial function better than propofol.     

Minimally invasive coronary artery bypass surgery

From 19.06.97 to 06.01.2000 36 patients with coronary heart disease underwent direct myocardium revascularization surgery by minimally invasive method (through minithoracotomy, off-pump and on the beating heart), anastomosis between left internal mammaria artery and anterior descending artery (ADA). The majority of the patients (55.6%) had one-vessel damage of ADA coronary bed, in the patients with damage of two and more vessels full revascularization of coronary bed was achieved by two coronary arteries bypass at once or by combination of minimally invasive coronary bypass (MICB) with PTCA. MICB is performed in specially selected patients according to stuct indications. Technique of operation, early postoperative course, possibilities of combination of MICB with other methods of treatment is described. Potential of MICB is discussed.     

Refractory coronary artery spasm after minimally invasive direct coronary artery bypass grafting

Postoperative coronary arterial spasm is a rare but potentially fatal complication. A 51-year-old male patient with a history of a reactive ergonovine stress test coronary angiogram developed refractory coronary artery spasm after undergoing minimally invasive direct coronary artery bypass grafting of the left anterior descending coronary artery. The patient was successfully managed with rapid implementation of intra-aortic balloon-pump counter pulsation and extracorporeal membrane oxygenation.     

Immunologic changes during minimally invasive surgery

Although recent experimental and clinical trials have documented that postoperative inflammation and changes in different immunologic parameters are less pronounced after laparoscopic approaches in comparison to open surgery, it still remains unclear what influence the pneumoperitoneum itself has on immunologic defense and function. This is mainly due to the endpoints of the different studies which investigate changes in the so-called immunologic parameters (cell subunits, C-reactive protein, cytokines, catecholamines or other stress hormones in plasma samples) rather than analyzing immunologic functions, such as cell activation, production of proteins, cell proliferation or in vivo immune defenses. So far, especially in clinical trials, no correlation has been demonstrated between the changes in immunologic parameters and relevant postoperative clinical endpoints, such as postoperative complications. Thus further clinical prospective randomized studies with relevant clinical endpoints and additional investigations of immunologic parameters are needed to prove the consequences of either minimally invasive surgery or open procedures on postoperative immune functions.     

Haemodynamic effects of heparin during coronary bypass surgery

Heparin has been suggested as an activator of the plasma kallikrein-kinin system, with possible formation of bradykinin, a potent vasodilator. Haemodynamic effects and changes in the kallikrein-kinin system were studied after heparin- and saline-injections in ten patients undergoing coronary bypass surgery. A moderate decrease in mean arterial pressure was found in all patients in the observation period, but significantly more at 2 and 3 min after heparin-injection compared with saline-injection. None of the other haemodynamic variables measured were significantly different when comparing heparin- to saline-injection. Heparin-injection resulted in significant changes in the kallikrein-kinin system, with a marked increase in spontaneous kallikrein-like activity as the most prominent feature, while no changes were found after saline-injection. Liberation of bradykinin would be expected to give a decrease in systemic vascular resistance with an increase in cardiac output. The results indicate that the plasma kallikrein-kinin system, though apparently activated after heparin-injection, does not contribute significantly to the decrease in arterial pressure in the patients studied.     

Stroke after conventional versus minimally invasive coronary artery bypass

BACKGROUND: Postoperative stroke is a serious complication after coronary artery bypass grafting with cardiopulmonary bypass (on-pump), and portends higher morbidity and mortality. It is unknown whether an off-pump cardiopulmonary bypass (OPCAB) approach may yield a lower stroke rate over conventional on-pump coronary artery bypass grafting. METHODS: From June 1994 to December 2000, OPCAB was performed in 2,320 patients and compared with 8,069 patients who had on-pump coronary artery bypass grafting, during the same period of time. The patients undergoing OPCAB were randomly matched to on-pump patients by propensity score. A logistic regression model was used to test the difference in the postoperative stroke rate between OPCAB and on-pump procedures controlling for the correlation between matched sets. A multiple logistic regression model predicting the risk of stroke adjusted by stroke risk factors and operation type was also computed. RESULTS: Matches by propensity score were found for 72% of the patients undergoing OPCAB. Patients undergoing on-pump coronary artery bypass grafting were 1.8 (95% confidence interval 1.0 to 3.1, p = 0.03) times more likely to suffer a stroke postoperatively than OPCAB patients after controlling for preoperative risk factors through matching. Independent predictors of stroke identified from the multiple logistic model included on-pump operation (versus OPCAB operation), female gender, 4 to 6 vessels grafted (versus <4 grafts), hypertension, history of previous cerebrovascular accident, carotid artery disease, chronic obstructive pulmonary disease, and depressed ejection fraction. CONCLUSIONS: Off-pump cardiopulmonary bypass avoids the risks of cardiopulmonary bypass and atrial trauma. A substantially lower stroke rate suggests that OPCAB is a neurologically safe treatment option for revascularization.     

Two cases of minimally invasive reoperative coronary artery bypass

Reoperative coronary artery bypass grafting (CABG) are still associated with higher mortality than primary CABG. This is due in part to the potential for cardiac and patent graft injury during their dissection and the reopening of the sternum. Therefore, in two patients with recurrent angina attributable to occulusion of the old vein graft to the LAD, we performed reoperative CABG by the minimally invasive direct coronary artery bypass (MIDCAB) procedures. The left internal thoracic artery was anastomosed to the LAD through small anterolateral thoracotomy without cardiopulmonary bypass. Both patients recovered fast and underwent postoperative angiogram, showing the new grafts widely patent. About two weeks later, both discharged in the conditiions of nearly normal activities. The reoperative MIDCAB grafting might be expected to be as safe and promissing as the primary one.     

Clinical experience with minimally invasive reoperative coronary bypass surgery

Objective.

To minimize the risk of standard and reoperative coronary artery bypass, we developed a minimally invasive approach. In this study we have evaluated the effectiveness of this technique.

Method.

Between April 1994 and September 1995, 12 men and 6 women, aged 55–84 years (mean, 69 years) with chronic stable angina (4) and recent post-myocardial infarction unstable angina (14), with left ventricular ejection fractions ranging 17–60% (mean 37%), underwent reoperative coronary artery bypass grafting using 7-cm mini-left and right anterior thoracotomy and subxiphoid incisions. Coronary artery anastomoses were carried out on beating hearts with local coronary occlusion. Ischemic preconditioning, beta and calcium channel blockers and the maintenance of mean arterial pressure at 75–80 mmHg, were used as adjuncts for myocardial protection. The internal mammary artery was isolated under direct vision up to the second rib with excision of the fourth costal cartilage. Coronary artery target sites were the left anterior descending in 12, right coronary artery in 4, obtuse marginal in 3, posterior descending in 1 and diagonal branch in 1 patient. Arterial grafts (mammary, right gastroepiploic, radial), either as single or composite grafts, were used liberally. Preoperative risk factors included congestive heart failure (7), chronic renal insufficiency (5), second reoperation (2), third reoperation (1), cerebrovascular disease (5), prior angioplasty (8) and preoperative intra-aortic balloon pumping in two patients.

Results.

There was no perioperative mortality with minimal morbidity. Twelve patients underwent patency study of the grafts 48–72 h postoperatively. Ten of the twelve grafts were patent; one internal mammary artery graft to the left anterior descending coronary artery (<1.5 mm) early in our series was occluded and one additional left internal mammary graft had a kink several centimeters away from the anastomosis, which was successfully opened by angioplasty. At a mean follow-up interval of 8 months all 16 surviving patients are in functional class I or II and all of them remain free of angina.

Conclusion.

In selected patients reoperative coronary artery bypass grafting can be performed with this minimally invasive approach with a low perioperative morbidity and mortality rate and satisfactory early graft patency rate with good symptomatic improvement.