Global myocardial revascularization without cardiopulmonary bypass using innovative techniques for myocardial stabilization and perfusion

The salvage potential of coronary sinus interventions: meta-analysis and pathophysiologic consequences

OBJECTIVES

Intermittent coronary sinus occlusion has been described to be effective in salvaging ischemic myocardium. This meta-analysis aims to review the efficacy of intermittent coronary sinus occlusion and intermittent coronary sinus occlusion in combination with retroperfusion of arterial blood as methods of myocardial salvage.

METHODS

A Medline search was performed to review the published literature on intermittent coronary sinus occlusion. The study inclusion criterion was a randomized, placebo-controlled trial with area of infarction (expressed as a percentage of the area at risk) as the primary end point.

RESULTS

Seven experimental trials comprising 125 test animals were found that analyzed the effects of intermittent coronary sinus occlusion on ischemic damage during coronary occlusion. A further 5 studies comprising 88 animals were designed to evaluate the effect of intermittent coronary sinus occlusion in combination with retroperfusion of arterial blood on the infarct size. A meta-analysis of the 7 studies analyzing the effect of intermittent coronary sinus occlusion revealed a significant reduction in infarct size of 29.3% in the treatment group compared with that in the placebo group (P <.001; 95% confidence interval, -40.9 to -17.7). A meta-analysis of the 5 trials analyzing the effect of intermittent coronary sinus occlusion in combination with retroperfusion revealed a reduction in infarct size of 39.4% in the treatment group compared with that in the placebo group (P <.001; 95% confidence interval, -48.9 to -29.9). Comparison between intermittent coronary sinus occlusion and intermittent coronary sinus occlusion in combination with retroperfusion of arterial blood showed no statistical difference (P =.19). An inverse relationship between achieved coronary sinus pressure increase per minute and infarct size could be found in the intermittent coronary sinus occlusion group (r = -0.92; P <.007), whereas in combination with retroperfusion, there was a negative correlation both between achieved coronary sinus pressure and the amount of the retroperfusate and myocardial salvage (r = -0.97; P <.004).

CONCLUSIONS

The use of intermittent coronary sinus occlusion and intermittent coronary sinus occlusion in combination with retroperfusion of arterial blood significantly decreases ischemic damage during coronary occlusions. Intermittent coronary sinus occlusion in combination with retroperfusion exhibits no significant profit in salvaging the ischemic myocardium in comparison with that provided by intermittent coronary sinus occlusion alone.

Reduction of systolic and diastolic dysfunction by retrograde coronary sinus perfusion during off-pump coronary surgery

OBJECTIVES

We evaluated the protective effects of retrograde coronary sinus perfusion to offset potential systolic and diastolic dysfunction (myocardial stunning) after temporary regional ischemia needed for off-pump coronary artery bypass grafting.

METHODS

Twenty Yorkshire-Duroc pigs (31.8 +/- 3.9 kg) underwent 15 minutes of mid-left anterior descending coronary artery ischemia in the beating heart. In 8 pigs, no protective measures were used. In 12 pigs, an aorta-coronary sinus shunt (with conventional cannulas) allowed retrograde perfusion during temporary ischemia; in 6 of these pigs, no leakage to the right atrium was ensured. Regional endocardial contraction was measured with sonomicrometer crystals. Systolic dysfunction (impaired regional shortening), diastolic dysfunction (contraction extending into early diastole), and coronary sinus nitric oxide and endothelin-1 levels were recorded.

RESULTS

Before ischemia, contraction did not extend into the diastolic interval. During ischemia, paradoxic bulging occurred in all hearts except in the occlusive coronary sinus shunt group (16% +/- 6% of baseline, P <.01). Sixty minutes after ischemia, systolic segment shortening recovered 36% +/- 24% without retrograde perfusion versus 56% +/- 20% and 61% +/- 14% with coronary sinus shunting (P <.05). Diastolic dysfunction (as percentage of diastolic time in contraction) was 38% +/- 16% in the nontreated group versus 22% +/- 22% and 9% +/- 9% (P <.05) after shunting and occlusive shunting, respectively. This correlated with a left ventricular end-diastolic pressure increase of 4 mm Hg in the ischemic group versus no change in the retrograde perfusion groups. Nitric oxide decreased 15% without shunting and increased 8% after occlusive coronary sinus shunting (P <.05).

CONCLUSIONS

Retrograde coronary sinus perfusion during simulated off-pump coronary revascularization diminishes systolic and diastolic dysfunction. An aortic-coronary sinus shunt is a rapid, recognized approach that can improve myocardial muscle and endothelial safety during off-pump coronary artery bypass grafting.

Our experiences for off-pump coronary artery bypass grafting to the circumflex system

BACKGROUND

Complete revascularization has been difficult in off-pump coronary artery bypass grafting (OPCAB). Hemodynamic deterioration often prevents access to the circumflex territory. This study presents instrumentation for accessing the circumflex territory, and our clinical experience.

METHODS

From August 1999 through December 2002, 140 patients underwent OPCAB via sternotomy in our institution. The 114 requiring reconstruction of the circumflex artery are the subjects of this study. There were no exclusion criteria. A series of techniques and instruments were developed to provide access to the circumflex area while hemodynamic stability was preserved, including the left pericardial traction technique, compression of the right pericardium, a right sternal retractor, and a type of shunt tube.

RESULTS

Patients received an average of 3.2 grafts (range, 2 to 6). Complete revascularization was achieved in 95% of the cases. Complications included respiratory insufficiency (0.8%), renal dysfunction (7%), and sternal wound infection (0.8%). Blood transfusions were required in 10 patients (8%). No patient suffered perioperative myocardial infarction or stroke. No operation was converted to cardiopulmonary bypass. There was no operative death. Predischarge angiography demonstrated a 99% patency rate.

CONCLUSIONS

With our techniques and instruments, off-pump coronary revascularizaion of the circumflex area may be performed safely to achieve complete revascularization. Early clinical results are excellent, but long-term longitudinal follow-up is required to assess the future effectiveness of OPCAB procedure with our techniques.

Off-pump coronary artery bypass graft surgery: the incidence of postoperative atrial fibrillation

Atrial fibrillation (AF) occurs in one quarter to one third of patients after coronary artery bypass graft surgery (CABG). Conventional CABG uses cardiopulmonary bypass, a process that is itself associated with a systemic vascular inflammatory response that contributes to postoperative morbidity. The avoidance of cardiopulmonary bypass is associated with a significant reduction in the inflammatory response and in the release of markers of myocardial necrosis when compared with conventional CABG. There is speculation that off-pump CABG may reduce the incidence of postoperative AF through reduced trauma, ischaemia, and inflammation. Current data, however, do not emphatically answer the question of whether the incidence of post-CABG AF is reduced by off-pump surgery. The evidence from both observational and randomised studies is conflicting and many studies have weaknesses in design, conduct, or interpretation. It remains an attractive hypothesis that postoperative AF is reduced by off-pump CABG but more robust data are required.

Maintaining hemodynamic stability and myocardial performance during off-pump coronary bypass surgery

Patients presenting for coronary artery bypass (CAB) surgery are now older and have more comorbid conditions. Off-pump (OPCAB) methods may reduce morbidity and mortality in these higher risk patients. Multivessel surgery has been limited by the difficulty in maintaining hemodynamic stability during lateral wall vessel grafting. Techniques for providing safe access to lateral wall vessels were applied in a largely unselected group of 665 OPCAB patients with emphasis on the avoidance of right ventricular compression. Safe access to essentially all target coronary arteries was achieved with very little need for pharmacological or mechanical support. No patient required new intraaortic balloon pumping and no patient required urgent conversion to cardiopulmonary bypass. Access to essentially all target coronary arteries can be achieved and myocardial performance can be maintained when strict attention is paid to operative strategies designed to minimize right-side heart compression.

A coronary active perfusion system for off-pump coronary artery bypass: advantage over passive perfusion regarding the physiology of the coronary artery

To avoid myocardial ischemia during off-pump coronary artery bypass, we developed a coronary active perfusion system (CAPS) that perfuses arterial blood to the coronary artery at the diastolic phase of the cardiac cycle by a syringe pump system. We report herein the details and compare CAPS with a passive shunt circuit from the femoral artery (FA shunt), regarding the physiology of the coronary artery. Six pigs were used for this study. After CAPS or FA shunt perfusion was established, coronary flow and coronary pressure were measured. The coronary flows in the native coronary artery, FA shunt perfusion, and CAPS perfusion with syringe pump stroke volume settings ranging from 0.1 to 0.4 ml were 27.2+/-3.0, 4.1+/-1.5, 12.7+/-1.2, 24.8+/-1.9, 33.3+/-1.6, and 42.2+/-1.9 ml/min, respectively. Mean coronary pressures under FA shunt perfusion and CAPS perfusion with stroke settings from 0.1 to 0.4 ml were 23.7+/-4.6, 48.8+/-5.0, 61.3+/-7.5, 70.8+/-5.4, and 82.3+/-5.2 mm Hg, respectively. CAPS had an advantage over the FA shunt regarding coronary flow with safe coronary pressure. Using CAPS, an off-pump coronary artery bypass can be performed safely without myocardial ischemia.

Off-pump coronary artery surgery

Cardiopulmonary bypass has several associated deleterious effects that include a systemic inflammatory response, coagulopathy, central nervous system complications and a variable degree of end-organ damage. The recent upsurge in interest in "beating-heart" surgery attempts to avoid these deleterious effects. Advances in surgical technique, such as the use of intracoronary shunts and the Octopus retractor, have made beating-heart surgery a reality. The challenges for the anaesthetist are greater than for coronary artery surgery using cardiopulmonary bypass, and whilst some advantages are proven, such as the lack of the inflammatory response and the decreased need for blood or blood products, others have yet to be proved and there is a need for further research. The advantages and disadvantages need to be evaluated in randomised studies in order to confirm the safety and efficacy of these new techniques in terms of long-term graft patency and decreased morbidity.

Hemodynamic collapse during off-pump coronary artery bypass grafting

BACKGROUND

The causes of hemodynamic collapse during off-pump coronary artery bypass (OPCAB) remain scarcely defined. We present an analysis of 23 cases of sustained hemodynamic collapse during elective off-pump CABG.

METHODS

During a 54-month period, we performed 1420 elective OPCAB procedures through a sternotomy, constituting 71.2% of the total CABG procedures performed. Twenty-three patients (1.6%) experienced hemodynamic collapse intra-operatively requiring immediate cardiopulmonary bypass. Preoperative characteristics, intraoperative data, and postoperative outcome were retrospectively reviewed in each patient.

RESULTS

In all cases, improvements in intra-operative technique and/or judgment could be made retrospectively. Twenty (20/23) of these patients had an uneventful postoperative course and three (3/23) patients had an unstable course with two deaths.

CONCLUSIONS

The causes of hemodynamic collapse during elective OPCAB were ischemic, mechanical, or a combination of both. A detailed review of our five and a half year experience has revealed a number of suggestions for improving the conduct of the operation.

Myocardial revascularization with and without cardiopulmonary bypass in multivessel disease: impact of the strategy on early outcome

BACKGROUND

The impact of myocardial revascularization without cardiopulmonary bypass (CPB) was evaluated in a series of consecutive patients with multivessel disease.

METHODS

From May 21, 1997 to November 30, 2000, 1,843 consecutive patients underwent isolated myocardial revascularization. From this total, 919 patients were done without CPB (group A, 49.9%) and 924 patients were done with CPB (group B, 50.1%). Patients that converted from without CPB to with CPB were included in group A. Thirty-three variables were evaluated with univariate and multivariate analysis to identify the independent variables predictive of higher incidence of early mortality, acute myocardial infarction, cerebrovascular accident, and early major events.

RESULTS

Early mortality was 2.2% (group A, 1.4%; group B, 3.0%; p = 0.016), acute myocardial infarction incidence was 1.8% (group A, 1.1%; group B, 2.6%; p = 0.027), cerebrovascular accident incidence was 0.9% (group A, 0.8%; group B, 1.0%; p = not significant), and early major events incidence was 6.7% (group A, 5.3%; group B, 8.2%; p < 0.001). Stepwise logistic regression analysis showed that CPB was an independent risk factor for higher mortality (odds ratio, 2.2; p = 0.0217), higher incidence of acute myocardial infarction (odds ratio, 2.5; p = 0.0185), and higher incidence of early major events (odds ratio, 1.8, p = 0.0034).

CONCLUSIONS

When CPB was not used, patients experienced lower early mortality and incidences of acute myocardial infarction were less complicated, both at univariate analysis and stepwise logistic regression analysis.

A new intracardiac microaxial pump: first results of a multicenter study

As coronary artery bypass grafting (CABG) surgery in the beating heart technique is progressing, new devices have been developed to overcome hemodynamic instabilities while tilting the heart for exposure of back wall vessels. A new device for in heart biventricular intracorporeal circulation was applied in 42 patients undergoing CABG surgery (Group 1). The control group consisted of 38 patients operated on using a conventional cardiopulmonary bypass setup (Group 2). The study protocol of the prospective, randomized multicenter study was approved by the local ethics committees. Patients were included following inclusion criteria and patient informed consent. Mean age, procedure time, mean arterial pressure (MAP), and hemolysis by means of plasma free hemoglobin (fHb) were assessed preoperatively, perioperatively, on postoperative Days 1 to 3, at discharge, and at a 3 month follow-up. The mean age was 62.1 (range 59-74) years (Group 1), 62.7 (range 48-72) years (Group 2); procedure time was 112 min +/- 31.9 min (Group 1), 137.4 min +/- 36.2 min (Group 2); and 2.3 +/- 0.6 (Group 1), 2.2 +/- 0.7 (Group 2), vessels were revascularized. The flow on pump was 3.7 (2.5/4.4) L/min (Group 1), 4.9 (3.6/6.2) L/min (Group 2) which resulted in a MAP of 69.8 (4.0/143) mm Hg (Group 1), 58.3 (5.3/94) mm Hg while assessing the vessels of the back wall. Hemolysis defined by fHB was lower than 20 mg/dl at all times pre- and postoperatively. Intraoperative maximum values were up to 100 mg/dl in 4 patients (2 in Group 1 and 2 in Group 2). Body mass index was 26.4 +/- 2.6 (Group 1), 27.9 +/- 3.2. New York Heart Association Class was II to III in both groups. There were no pump related life threatening or severe adverse events. Beating heart procedures with ICC can be reliably and safely achieved. As the device is easy to use, it may deserve a more widespread use in the future.

Complete revascularization in coronary artery bypass grafting with and without cardiopulmonary bypass

BACKGROUND

The feasibility of complete revascularization on the beating heart without cardiopulmonary bypass (CPB) as compared with the standard operation with CPB in elective low-risk patients with multivessel disease has not been clearly demonstrated in a prospective trial.

METHODS

Eighty selected low-risk patients were enrolled. In preoperative study with coronary angiography, the decision was made whether complete revascularization without CPB could be performed. Patients were randomly assigned to receive CABG either with (n = 40) or without CPB (n = 40). Randomization criteria were age, sex, and left ventricular ejection fraction. Completeness of revascularization as well as short- and mid-term clinical outcome in a 13.4 +/- 6.5 month follow-up period were monitored.

RESULTS

Twenty-six of 40 (65%) patients undergoing CABG without CPB underwent complete revascularization. In 5 of these patients (12.5%) suitable vessels were discarded for technical reasons and 9 patients (22.5%) were switched to CABG with CPB owing to the deeply intramyocardial course of target vessels (n = 5) or to hemodynamic instability (n = 4). In the group of patients operated on with CPB, 34 of 40 patients (85%) received complete revascularization. In 6 patients (15%) suitable vessels were discarded for technical reasons. Mean number of bypass grafts was 3.1 +/- 0.8 with CPB and 2.6 +/- 0.5 without CPB (p = 0.043). Clinical outcome and hospital stay were comparable in both groups. No patient died during the study period. No myocardial infarction was observed. Three patients undergoing CABG without CPB underwent successful PTCA 3 months after surgery.

CONCLUSIONS

CABG without the use of CPB is effective for complete revascularization in the majority of selected low-risk patients. Nevertheless, it has to be stated that the rate of incomplete revascularization in this early series of CABG without CPB is higher, and compromises the basic principle of complete revascularization.

Effects of ischemic preconditioning and synchronized coronary venous retroperfusion in an off-pump coronary artery bypass grafting model

Off-pump coronary artery bypass grafting (CABG) has become a popular procedure. However, temporary occlusion of the target vessel is sometimes a threat to the patients. Although ischemic preconditioning (IP) has been proposed to reduce myocardial injury, its effects remain controversial. The coronary veins represent an alternate route for delivery of therapeutic agents and arterial blood to the acutely ischemic myocardium. The aim of this study was to investigate the protective effect against myocardial ischemia and reperfusion injury of combined IP and synchronized coronary venous retroperfusion (SCVR) in an off-pump CABG model. Twenty-one pigs were assigned to 3 groups of 7 animals. In the control group, the left anterior descending coronary artery (LAD) was occluded for 45 min followed by 2 h of reperfusion using a left intrathoracic artery (LITA) bypass circuit. In the IP group, LAD occlusion was done for 5 min with 15 min of reperfusion, followed by 45 min of LAD occlusion. In the SCVR group, pretreatment before LAD occlusion was the same as in the IP group. Then, SCVR was commenced just after the start of LAD occlusion for 45 min. The percent systolic shortening of ischemic myocardium (measured by sonomicrometry) after reperfusion via the LITA was significantly (p < 0.001) greater in the SCVR group (14.6 +/- 3.3%) than in the control group (-1.6 +/- 5.6%, 95%CI: -24.3 - -8.1) or the IP group (0.7 +/- 8.0%, 95%CI: -22.0 - -5.8) after 30 min of reperfusion, and this difference persisted throughout the reperfusion period. Infarct size (expressed as a percentage of the area at risk) was significantly (p < 0.001) smaller in the SCVR group (2.4 +/- 2.7%) than in the control group (83.0 +/- 2.3%, 95%CI: -99.0 - -62.4) or the IP group (42.0 +/- 23.0%, 95%CI: -58.0 - -21.3). Combined SCVR and IP had a potent myocardial protective effect in the present off-pump CABG model. This method may be clinically feasible and may be able to prolong a safe coronary occlusion.

Con: beating-heart surgery for coronary revascularization: is it the most important development since the introduction of the heart-lung machine?

Contrary to what the media tend to suggest, beating-heart coronary artery bypass grafting (BHCABG) is not a new technique. It has been performed since the advent of coronary revascularization but, until recently, was largely abandoned in favor of cardiopulmonary bypass (CPB) and cardioplegic techniques. However, with the introduction of minimally invasive coronary surgery and mechanical methods for target-artery stabilization, interest in BHCABG has been renewed. In carefully selected cases, this approach has the advantages of simplicity, avoidance of the inflammatory response caused by CPB, and a decreased need for blood transfusion. Nevertheless, BHCABG may be technically difficult in some patients, and it involves a steep learning curve. Potential risks include incomplete revascularization, ischemia during temporary target-artery occlusion, and suboptimal anastomoses. Because of the need for special equipment, BHCABG can be expensive and time consuming. It may benefit older or sicker patients who are poor candidates for CPB, especially those with left anterior descending or right coronary artery lesions, but it should be used with discretion and not be considered for all coronary patients.