Intraoperative 2-dimensional echocardiography: Ejection of microbubbles from the left ventricle after cardiac surgery

Although the presence of entrapped air in the left ventricle at surgery has long been a concern, its prevalence and clinical significance are unknown. Two-dimensional echocardiography provides a unique means for observing intracardiac microbubbles intraoperatively. Accordingly, intraoperative 2-dimensional echocardiograms obtained in 79 patients immediately after cardiopulmonary bypass were examined for the presence of microbubbles. Left ventricular microbubbles were detected in 14% of coronary artery bypass operations (n = 22), 50% of multiple valve replacements (n = 8), 67% of single valve replacements (n = 58), and 100% of atrial septal defect closures (n = 4), left atrial myxoma resections (n = 2), and mitral commissurotomies (n = 2). Microbubbles were not observed in patients undergoing coronary artery bypass with valve replacement (n = 4) or with removal of left ventricular aneurysm (n = 1). Continuous ejection of microbubbles from the left ventricle was frequently noted for extended periods of time and, although no patient in this study showed evidence of gross neurologic dysfunction, the possibility of subclinical organ damage exists. We conclude that 2-dimensional echocardiography is useful for detection of intracardiac microbubbles and therefore may be instrumental in their elimination.     

Coronary Artery Bypass Grafting without Cardiopulmonary Bypass: Improvement in Cardiac Function Following Enflurane Anaesthesia during Coronary Occlusion

Severe adverse effects, especially neurologic complications after cardiopulmonary bypass have lead to the development of techniques for performing coronary artery bypass graft surgery without cardiopulmonary bypass. Laboratory and clinical studies confirmed the positive role of enflurane anaesthesia in preventing myocardial dysfunction following an ischaemic interval. The aim of this study was to evaluate the haemodynamic response to enflurane anaesthesia during single graft coronary bypass surgery without cardiopulmonary bypass. Twenty one patients were divided randomly into two groups: control and enflurane groups. Haemodynamic parameters and those derived from a pulmonary artery catheter were recorded and analysed. In the enflurane group, the amount of fentanyl administered was considerably less than in the control group: 25.7 +/- 3.8 microg/kg vs 36.8 +/- 1.6; p=0.03. The mean arterial pressure during enflurane administration was lower than in control group, but the difference was not significant. Despite a dearease in left ventricular function during the performance of the anastomosis in the enflurane group, a significant recovery was noted after 20 minutes of reperfusion: cardiac index increased from 1.4 +/- 0.1 to 1.85 +/- 0.1 L/min/m2 and left ventricular stroke work index from 15.8 +/- 1.1 to 27.7 +/- 6.7 g.m.m2 . In the control group, the deterioration in cardiac function observed during the graft anastomosis did not recover till the end of the surgical procedure. We conclude that enflurane anaesthesia may be a positive addition to fentanyl-based anaesthesia by improving myocardial function following CABG without bypass surgery.     

PGE1治疗鱼精蛋白中和肝素诱发肺动脉高压的疗效观察

本研究的目的观察PGE1对鱼精蛋白中和肝素所致肺动脉高压的治疗作用.7例体外循环心内直视手术患者,心内操作结束主动脉根部注射鱼精蛋白对抗肝素后肺动脉平均压≥30mmHg即行PGE1 0.02～0.04蘥*min-1*Kg-1持续输注,并于注射前后不同时间分别监测动脉收缩压(SABP)、舒张压(DABP)、平均动脉压(MABP)、中心静脉压(CVP)、平均肺动脉压(MPAP)、肺毛细血管嵌压(PCWP),采用热稀释法测定心输出量(CO),并计算心指数(CI)、每搏指数(SI)、左心室和右心室做功指数(LVSWI,RVSWI)、肺循环阻力(PVR)及体循环阻力(SVR).结果:PGE1持续输注后,SABP、DABP、CVP、CO、SI未发生变化.肺动脉压、右室做功指数和肺血管阻力在持续PGE1 0.02～0.04μg*min-1*Kg-1注射后30min降低为注射前水平(P＜0.05).结论:持续静脉输注PGE1 0.02～0.04μg*min-1*Kg-1可以逆转体外循环心内直视手术鱼精蛋白中和肝素所致的肺动脉高压,降低肺血管阻力,对动脉压和心排血量无明显影响.     

Effect of peripheral cardiopulmonary bypass on left ventricular size, afterload and myocardial function during elective supported coronary angioplasty.

Although cardiopulmonary bypass support has been increasingly used for high risk coronary angioplasty, few data exist regarding its effects on left ventricular function. Accordingly, in 20 patients changes in left ventricular size, afterload and myocardial function were assessed by continuous hemodynamic monitoring and simultaneous two-dimensional echocardiography during cardiopulmonary bypass-supported high risk angioplasty. The cross-sectional left ventricular area during bypass support remained unchanged during diastole, whereas during systole it decreased (from 29.6 +/- 11.4 to 27.6 +/- 10.4 cm2, p less than 0.05). Global left ventricular function expressed as fractional area change remained unchanged from baseline to bypass support but decreased during balloon inflation (from 0.27 +/- 0.11 to 0.17 +/- 0.09, p less than 0.001). The end-systolic meridional wall stress decreased during bypass support (from 141 +/- 75 to 110 +/- 58 x 10(3) dynes/cm2, p less than 0.02). Regional myocardial function was assessed by a wall motion score (0 = normal, 1 = hypokinesia, 2 = akinesia and 3 = dyskinesia). Regions supplied by a stenotic (greater than or equal to 50% diameter) vessel deteriorated during bypass support (score from 0.9 +/- 0.8 to 1.06 +/- 0.8, p less than 0.01), whereas regions supplied by a nonstenotic vessel did not. Regions supplied by the target vessel deteriorated further during balloon inflation (score from 0.7 +/- 0.6 to 1.7 +/- 0.75, p less than 0.001). Thus, although left ventricular size and global function remain unchanged and afterload decreases during bypass support, myocardial dysfunction in regions supplied by a stenotic vessel may occur. Furthermore, regional and global left ventricular dysfunction still occur with angioplasty balloon inflation during cardiopulmonary bypass support.     

Left main coronary artery stenosis: factors predicting cardiac events in patients awaiting coronary surgery

Although most patients with left main coronary artery stenosis undergo urgent coronary artery bypass grafting, limited information is available regarding the risk factors that might lead to cardiac events between angiographic diagnosis and surgery. We retrospectively reviewed 1,731 cases of coronary artery bypass grafting at our institution, 97 of which were performed in patients with significant (> or = 50%) left main coronary artery stenosis. These patients were placed in 1 of 2 groups: eventful waiting or uneventful waiting. We analyzed multiple preoperative variables, and the incidence of serious cardiac events (death, myocardial infarction, unstable angina, left ventricular failure, and life-threatening ventricular arrhythmias) during the waiting period between angiography and surgery Four patients (4.1%) experienced serious cardiac events while awaiting surgery (1 had non-ST-elevation myocardial infarction; 3 had life-threatening ventricular arrhythmias); none died. All the events occurred more than 24 hours after cardiac catheterization. Of the preoperative variables analyzed (acute coronary syndrome, age, history of diabetes, hypertension, hyperlipidemia, smoking, renal failure, severity of left main stenosis, right coronary artery involvement, ejection fraction, and use of intra-aortic balloon pump), only acute coronary syndrome predicted the incidence of preoperative cardiac events (P=0.001). The occurrence of severe cardiac events while patients await coronary artery bypass grafting is rare. Carefully selected patients with severe left main coronary artery stenosis can safely await surgery. Concomitant acute coronary syndrome and severe left main coronary artery stenosis indicate a high risk for cardiac events. Therefore, in patients with these conditions, emergency coronary artery bypass may be preferable.     

Beating heart surgery and left ventricular dysfunction

We report our experience with systematic coronary revascularization on the beating heart among patients with left ventricular dysfunction as defined by a left ventricular ejection fraction < or = 40%. Between September 1996 and April 2000, 500 off-pump (OPCAB) revascularizations were performed (95% of all revascularizations for the same time frame, single surgeon). Among them, 76 patients qualified as left ventricular dysfunction and were compared to a similar cohort of 237 patients operated on with cardiopulmonary bypass (CPB) during the same time frame. Age and sex distribution, average preoperative left ventricular ejection fraction and incidence of preoperative unstable angina were the same for both groups. On average, 3.04 +/- 0.89 and 2.97 +/- 0.69 grafts/patient were made in the OPCAB and CPB groups respectively (p = NS). Complete revascularization was achieved in 95% of the OPCAB group. Incidence of preoperative intra-aortic balloon assistance were higher in OPCAB (22% versus 9%, p = 0.005) whereas postoperative need for new intra-aortic balloon assistance was higher in CPB (8% versus 0%, p = 0.02). Incidence of postoperative myocardial infarction was comparable in both groups (6.5% versus 5.5%). Maximal creatinine phosphate of myocardial origin were lower in OPCAB group (beating heart: 32 +/- 52%, cardiopulmonary bypass: 45 +/- 51%, p = 0.055). Operative mortality was lower in OPCAB group although it did not reach statistical significance (beating heart: 2.6% versus cardiopulmonary bypass: 4.6%, p = 0.3). Complete coronary revascularization on the beating heart can be achieved in patients with left ventricular dysfunction with excellent outcome and low operative mortality.     

Surgical ablation of ventricular tachycardia with sequential map-guided subendocardial resection: electrophysiologic assessment and long-term follow-up

A new operative technique of sequential map-guided subendocardial resection (SER) was used in 45 consecutive patients for the treatment of sustained ventricular tachycardia due to coronary artery disease. This technique is characterized by map-guided SER or cryothermic ablation during normothermic cardiopulmonary bypass, followed by repeated sequences of programmed stimulation to assess adequacy of resection. The patients' mean age was 59 +/- 10 years and the mean left ventricular ejection fraction was 34 +/- 12%. Twenty-five (56%) patients had a history of myocardial infarction within the previous 2 months. After ventriculotomy, 34 patients (76%) had inducible monomorphic ventricular tachycardia. These patients underwent repeated sequences of ventricular tachycardia induction and mapping during normothermic bypass followed by successive SER or cryothermic ablation until sustained monomorphic ventricular tachycardia was no longer inducible. Twenty-seven patients had a total of 60 discrete, mappable tachycardias induced and seven patients had 10 discrete tachycardias that were too fast to accurately map. In the remaining 11 patients, no ventricular tachycardia was inducible after ventriculotomy and SER, which included all visually identifiable scar, was performed. The mean cardiopulmonary bypass time was 102 +/- 27 min. Forty-one of 45 patients (91%) survived to hospital discharge, and 35 of 41 patients (85%) had no inducible ventricular tachycardia at postoperative electrophysiologic evaluation performed in the absence of all antiarrhythmic drugs. The remaining six patients had no inducible ventricular tachycardia with drug therapy. All four operative nonsurvivors had refractory cardiac collapse preoperatively. Over 19 +/- 12 months of follow-up, there were four sudden cardiac deaths and no nonfatal recurrences of ventricular tachycardia. There were seven additional cardiac deaths. Actuarial cardiac survival was 0.57, and freedom from arrhythmic events was 0.76 at 42 months. Thus, in the absence of cardiogenic shock, the technique of sequential map-guided SER achieves: (1) a high operative survival with acceptable perfusion times, (2) excellent long-term arrhythmia control, and (3) survival comparable to that in patients with similar left ventricular function and no history of ventricular tachyarrhythmia.     

Right ventricular function in an operating room model of mechanical left ventricular assistance and its effects in patients with depressed left ventricular function

Approximately 20% of patients who receive left ventricular assist devices (LVADs) for refractory cardiac failure after open heart surgery have had complications of right ventricular failure. To evaluate this problem in the diseased heart we simulated an LVAD in the operating room by bypassing and unloading the left ventricle with the heart-lung machine before routine open heart surgery. Right ventricular function was assessed in 12 patients with preoperative left ventricular ejection fractions of less than 0.55 (poor left ventricular function) (mean +/- SEM 0.40 +/- 0.03) and 10 patients with ejection fractions greater than 0.55 (normal left ventricular function) (0.63 +/- 0.02). Measurements before and during left ventricular bypass in the normal left ventricular function group revealed no change in cardiac output (from 5.7 +/- 0.6 to 5.8 +/- 0.4 liters/min), with a decrease in right ventricular end-diastolic pressure (from 8 +/- 2 to 6 +/- 1 mm Hg). However, in the poor left ventricular function group, cardiac output was increased significantly during left ventricular bypass from 4.5 +/- 0.2 to 5.3 +/- 0.4 liters/min and right ventricular end-diastolic pressure was decreased significantly from 13 +/- 2 to 8 +/- 2 mm Hg. During bypass there were significant reductions in mean pulmonary arterial pressure from 17 +/- 3 to 10 +/- 2 mm Hg in the normal left ventricular function group and from 27 +/- 3 to 12 +/- 2 mm Hg in the poor left ventricular function group. These measurements reflect passive changes in pulmonary pressures due to reductions in left ventricular filling pressure during left ventricular bypass.(ABSTRACT TRUNCATED AT 250 WORDS)     

Predictors of emergency conversion to on-pump during off-pump coronary surgery

The purpose of this study was to determine predictors and evaluate outcomes of emergency conversion to cardiopulmonary bypass during planned off-pump coronary artery bypass grafting. From January 2001 to November 2005, of 467 consecutive patients aged >or= 60 years who underwent off-pump coronary surgery, 17 (3.6%) were converted to cardiopulmonary bypass. Those converted to an on-pump technique had significantly higher rates of postoperative cerebrovascular accident (17.6% vs 1.1%), intraaortic balloon pumping (5.9% vs 0%), and red blood cell transfusion (82.4% vs 57.3%), as well as prolonged intensive care unit stay (52.9% vs 25.2%), ventilation time (25% vs 5.3%) and hospital stay (64.7% vs 31.3%) compared to patients whose operation was completed off-pump. Multivariable logistic regression identified left ventricular ejection and left main stenosis as significantly associated with conversion. The rate of emergency conversion to cardiopulmonary bypass during planned off-pump coronary surgery was acceptable, but patients who required conversion had less favorable early outcomes than those who remained off-pump.     

The role of the intra-aortic balloon in cardiac anesthesia and surgery.

The use of the intra-aortic balloon pump (IABP) in cardiac surgical patients has become accepted treatment. The purposes of this study were (1) to determine the frequency of use of the balloon, (2) to re-evaluate the indications for the IABP, and (3) to assess the hemodynamic effects of the balloon during surgery.In the past 24 months, the IABP was used in 63 of 1,738 (3.62%) adult cardiac surgical patients. Eight patients required the IABP prior to surgery due to complicated acute myocardial infarctions. In 13 patients, the IABP was used in the operating room before bypass for complicated infarctions or severe left ventricular dysfunction. It was not considered necessary before bypass in patients with left main coronary artery disease, moderately depressed left ventricular function, or unstable angina. In addition, 42 patients required the IABP to discontinue cardiopulmonary bypass.Detailed hemodynamic measurements were made in 11 patients. The IABP decreased systolic blood pressure, left and right ventricular filling pressures, and peripheral resistance, while it increased diastolic and mean arterial pressures, stroke work, cardiac output, and the endocardial viability ratio. The intra-aortic balloon was shown to be life-saving in certain patients. However, it should only be used selectively for specific indications. Careful surgical and anesthetic management with good monitoring can be used in many patients instead of the balloon.     

Clinical and angiographic prediction of cardiac death after coronary artery bypass graft surgery.

OBJECTIVES--To study the risk factors for cardiac mortality after coronary artery bypass graft surgery. DESIGN AND SETTING--Follow up study of patients who had undergone coronary artery bypass graft surgery at the University Hospital of Oulu, Finland. PATIENTS AND INTERVENTIONS--339 consecutive patients who underwent cardiac catheterisation three months after bypass surgery. MAIN OUTCOME MEASURES--Incidence of cardiac deaths during the follow up period of five years and predictive value of clinical and angiographic variables for subsequent cardiac mortality. RESULTS--The incidence of cardiac deaths was 5.1%, and 81% of these were sudden deaths. The postoperative ejection fraction was significantly lower in the patients with subsequent cardiac death than in the survivors (p less than 0.001), and their left ventricular end systolic and end diastolic volumes were higher (p less than 0.001 and p less than 0.05 respectively). The incidence of cardiac deaths was 43% in the patients with a postoperative ejection fraction of less than 40%. The myocardial jeopardy index after surgery and the rate of graft patency were not significantly different in the survivors and patients who died. The only clinical factors that were different between the groups were postoperative use of diuretics (p less than 0.001) or digitalis (p = 0.02). After adjustment for other prognostic variables by the proportional hazards method, a low postoperative ejection fraction remained significant as a predictor of the relative risk of cardiac mortality five years after operation (p less than 0.01). CONCLUSIONS--Patients with angiographic evidence of impaired left ventricular function after bypass surgery are still at relatively high risk of dying suddenly, but myocardial ischaemia due to incomplete revascularisation is not strongly associated with an increased risk of cardiac mortality. Conventional clinical methods do not seem to be helpful for identifying patients with an increased risk of cardiac death after bypass surgery.     

Clinical and angiographic prediction of cardiac death after coronary artery bypass graft surgery.

OBJECTIVES--To study the risk factors for cardiac mortality after coronary artery bypass graft surgery. DESIGN AND SETTING--Follow up study of patients who had undergone coronary artery bypass graft surgery at the University Hospital of Oulu, Finland. PATIENTS AND INTERVENTIONS--339 consecutive patients who underwent cardiac catheterisation three months after bypass surgery. MAIN OUTCOME MEASURES--Incidence of cardiac deaths during the follow up period of five years and predictive value of clinical and angiographic variables for subsequent cardiac mortality. RESULTS--The incidence of cardiac deaths was 5.1%, and 81% of these were sudden deaths. The postoperative ejection fraction was significantly lower in the patients with subsequent cardiac death than in the survivors (p less than 0.001), and their left ventricular end systolic and end diastolic volumes were higher (p less than 0.001 and p less than 0.05 respectively). The incidence of cardiac deaths was 43% in the patients with a postoperative ejection fraction of less than 40%. The myocardial jeopardy index after surgery and the rate of graft patency were not significantly different in the survivors and patients who died. The only clinical factors that were different between the groups were postoperative use of diuretics (p less than 0.001) or digitalis (p = 0.02). After adjustment for other prognostic variables by the proportional hazards method, a low postoperative ejection fraction remained significant as a predictor of the relative risk of cardiac mortality five years after operation (p less than 0.01). CONCLUSIONS--Patients with angiographic evidence of impaired left ventricular function after bypass surgery are still at relatively high risk of dying suddenly, but myocardial ischaemia due to incomplete revascularisation is not strongly associated with an increased risk of cardiac mortality. Conventional clinical methods do not seem to be helpful for identifying patients with an increased risk of cardiac death after bypass surgery.     

Residual effects when chronic propranolol therapy is discontinued within 48 hours of cardiopulmonary bypass.

Recommendations regarding the safe waiting period between discontinuing chronic oral propranolol therapy and beginning cardiopulmonary bypass have varied from a few hours to 2 weeks. In the present study, utilizing adult dogs, propranolol was discontinued 8 or 48 hours prior to surgery. A reduction in cardiac output and elevations of left ventricular end-diastolic pressure, peak systolic pressure, and systemic resistance were noted when cardiac function was evaluated following the induction of anesthesia and prior to undertaking cardiopulmonary bypass. The magnitude of these differences was directly related to the degree of volume loading and inversely related to the interval between the last dose of propranol and the determination of cardiac function. Reduction of heart rate was the most evanescent of propranolol's hemodynamic effects as the marked bradycardia which persisted throughout the course of propranolol therapy was no longer evident 8 hours after the last oral dose of the drug. Following total cardiopulmonary bypass of 1 hour's duration, undertaken 8 hours after the last oral dose of propranolol, cardiac output and left ventricular end-diastolic pressure had returned to normal but peak systolic pressure and systemic resistance remained significantly elevated, When 48 hours had elapsed between discontinuing propranolol and beginning cardiopulmonary bypass, postbypass cardiac function was essentially normal with only slight persistent elevations of peak systolic pressure and systemic resistance detected. When the combined effects of ischemic heart disease and propranolol therapy, the altered metabolic and hemodynamic effects of different routes of drug administration, and the varying durations of cardiopulmonary bypass are taken into consideration, some of the discrepancies between previously reported clinical and experimental findings regarding the duration of persistent propranolol effects can be understood. The clinical course is usually benign in patients who have received propranolol to within a few hours of surgery without specific indication. However, it is often complicated when the drug is continued until just prior to surgery in patients dependant on propranolol for pain or arrhythmia control. In patients demonstrating propranolol dependence, control of symptoms with intra-aortic balloon counterpulsation is recommended followed by the gradual withdrawal of propranolol and elective aortocoronary bypass surgery.     

Emergency coronary surgery after transluminal angioplasty. Immediate results and long-term outcome of 100 operations]

The increasing application of percutaneous transluminal coronary angioplasty (PTCA) requires evaluation of emergency coronary artery surgery for complications of this procedure. In a consecutive series of 2,576 angioplasties performed between April 1980 and January 1990, 100 patients (82 men and 18 women, average age 54 +/- 10 years, 3.9%) underwent emergency coronary artery surgery because of complications. The artery involved was the left anterior descending artery in 81% of cases. The causal lesion was a dissection and/or thrombus in 95% of cases; 85% of patients were referred for surgery with acute myocardial infarction. The average delay before surgery was 110 +/- 15 minutes (interval between coronary occlusion and starting cardiopulmonary bypass) and 155 coronary grafts were implanted (1.5 per patient). The hospital mortality was 19%; the infarction rate was 57%. The left ventricular ejection fraction decreased from 63 +/- 10% (preoperatively) to 52 +/- 9% (postoperatively), p less than 0.001. Hospital mortality was significantly related to three factors, old age, unstable angina before PTCA, and cardiogenic shock or the necessity for external cardiac massage. In the subgroup of patients developing cardiogenic shock (n = 7) or requiring external cardiac massage during transfer to the operating theatre (n = 16) the mortality was 44%. Among the 81 survivors, the global 7 year survival rate was 96% (Kaplan-Meier) with 3 cardiac deaths, 2 other patients developing myocardial infarction and 4 undergoing repeat angioplasty. After an average follow-up of 55 +/- 38 months, 80% of patients are asymptomatic, 34% have no antianginal drugs and 73% of those who were previously employed have returned to work.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ventricular arrhythmias after coronary artery bypass graft surgery: incidence, risk factors and long-term prognosis

The incidence, risk factors and long-term prognosis of complex ventricular arrhythmias after coronary artery bypass graft surgery are not known. Complex ventricular arrhythmias are defined as Lown grades 4a (couplets), 4b (ventricular tachycardia) and 5 (R on T phenomenon). Ninety-two patients with normal left ventricular function who underwent elective coronary artery bypass graft surgery were prospectively evaluated. Ventricular arrhythmias were documented by predischarge 24 hour ambulatory electrocardiographic monitoring; 43% of patients had no or simple ventricular arrhythmias (Lown grades 1 to 3) and 57% had complex ventricular arrhythmias. Risk factors analyzed included age, sex, diabetes, hypertension, smoking, preoperative digoxin or propranolol therapy, cardiopulmonary bypass time, aortic cross-clamp time, number of vessels bypassed, peak creatine kinase (CK) elevation and pericarditis. No risk factor identified patients at higher risk for complex ventricular arrhythmias. Patients were followed up for 6 to 24 months (mean 16). Patients with complex ventricular arrhythmias did not have a higher incidence of sudden death, cardiac death, syncope, angina, myocardial infarction or cerebrovascular accident. It was concluded that: Complex ventricular arrhythmias are common after coronary artery bypass graft surgery. None of the risk factors considered identify high risk patients. Complex ventricular arrhythmias after coronary artery bypass graft surgery do not indicate a poor prognosis in patients with normal left ventricular function.     

Metabolic and haemodynamic changes in the heart during the early phase of cardiopulmonary bypass: I. Clinical observations

Knowledge of the effects of cardiopulmonary bypass on the myocardium and on cardiac function is limited. We therefore studied changes in haemodynamics and myocardial metabolism during the initial phase of cardiopulmonary bypass in two patient groups. In one group "normothermia" (34 degrees C) was used while on bypass, with an empty beating heart; in the other group hypothermia (range 27-33 degrees C) with ventricular fibrillation was used. Mean aortic pressure and myocardial oxygen consumption decreased significantly in both groups after instalment of CPB. The arterial-coronary sinus differences in lactate changed to negative values within 5 min of the start of bypass, indicating release instead of uptake of lactate. This release was maintained during the observation period and increased significantly in the hypothermic patient group when the ventricles were fibrillating. Therefore in patients undergoing aorto-coronary bypass surgery, detrimental changes in the myocardium must be anticipated during the initial phase of cardiopulmonary bypass prior to aortic cross clamping.     

Coronary surgery of the beating heart. First year of experience in a series of 317 non-selected coronary patients

From May 1999 to May 2000, 317 unselected patients, representing 92.7% of all coronary artery surgery procedures, underwent open heart surgery of the beating heart by median sternotomy with the aid of a cardiac stabilising device. The main preoperative characteristics were: mean age = 66.1 years; men = 78.9%; left main stem disease = 31.8%; mean left ventricular ejection fraction = 54.1%; mean Parsonnet index = 16.9. These 317 patients were compared with a group of 303 patients who underwent coronary bypass surgery the year before by the same surgical team with cardiopulmonary bypass (CPB) and cardiac standstill. Seven hundred and eighty-six distal anastomoses were carried out in the beating heart group (2.48 grafts per patient) compared with 2.91 in the CPB group: p < 0.001). There were 10.1% single bypass, 37.5% double bypass, 47.3% triple bypass and 5% quadruple bypass procedures. A cardiopulmonary bypass was required in 13 patients (4.1%). The mortality at 30 days was 3.1% versus 4.6% in the CPB group (p = NS). The need for blood transfusion was reduced by nearly 40% in the beating heart group (23.7% versus 39.9%, p < 0.001). The incidence of cerebrovascular complications was reduced from 3% in the CPB group to 0.6% in the beating heart group (p = 0.06). The peak postoperative troponine I levels were much lower in the beating heart group (2.5 versus 6.4 ng/ml, p < 0.001). The authors conclude that surgery on the beating heart is feasible in most patients. Compared with conventional surgery under CPB, there seems to be less requirement for blood transfusion and a tendency to reduce the cerebral risk. Nevertheless, a large prospective randomised trial is required to validate the potential advantages and limitations of this technique with respect to conventional surgery and to determine the optimal indications of surgery on the beating heart.     

Haemodynamics during maximal exercise after coronary bypass surgery.

Fifty patients underwent an objective measurement of physical working capacity by means of a multistage test of maximally tolerated exertion before and after coronary bypass surgery; 29 patients also had haemodynamic measurements during maximal exercise before and after coronary bypass surgery. The patients were divided into 3 groups according to the degree of revascularisation: adequate (n = 20), partial (n = 17), or none (n = 13). Adequate revascularisation induces a large increase in physical working capacity because of an increased maximal heart rate and maximal cardiac output; stroke volume during maximal exercise and ejection fraction at rest were not modified, suggesting no major changes in left ventricular function. After unsuccessful coronary bypass surgery, the physical working capacity was unchanged despite an increased maximal heart rate; maximal cardiac output was unchanged and stroke volume during maximal exercise was significantly lower. These undesirable results are often associated with perioperative myocardial infarction and are attended by a decreased ejection fraction at rest; these data suggest an impaired left ventricular function after unsuccessful coronary bypass surgery. The results of partial revascularisation are intermediate but appear to be determined by the incidence of partial graft failure which is also often associated with perioperative myocardial infarction. From individual changes in data collected during maximal exercise testing, it is often impossible to predict the degree of revascularisation.     

Valvular-ventricular interaction: importance of the mitral apparatus in canine left ventricular systolic performance

As the mitral valvular apparatus tenses during systole, forces transmitted along the chordae tendineae to the left ventricular chamber may influence left ventricular performance. To test this hypothesis, 10 dogs anesthetized with fentanyl were studied during cardiopulmonary bypass. The importance of the mitral apparatus in left ventricular systolic function was assessed independent of load by means of the slope of the contractile state-dependent left ventricular peak isovolumetric pressure-volume relationship (Emax), which was measured at constant heart rate and aortic pressure with a micromanometer inside a left ventricular intracavitary balloon before and immediately after all chordae tendineae were severed. Herniation of the balloon was prevented by a disk secured to the mitral anulus. Emax decreased from 11.97 +/- 3.35 (+/- SD) to 6.38 +/- 0.96 mm Hg/ml (p less than .001) with chordal severing. The volume intercept (Vo) was unchanged. Fluoroscopic studies of the balloon contour in eight additional dogs revealed dyskinesia in the area of the papillary muscle insertion and substantial alterations in chamber geometry during systole after the chordae were severed. Accordingly, we conclude that global left ventricular systolic performance is impaired when chordal attachments of the mitral valve are disrupted. Changes in left ventricular geometry or loss of inward force normally transmitted to the left ventricular wall as the valve tense may underlie these changes. These findings suggest that postoperative left ventricular dysfunction after mitral valve replacement may be attributable, in part, to excision of the native mitral apparatus at the time of surgery and support efforts to spare chordae during mitral valve surgery.     

Systemic pattern of free radical generation during coronary bypass surgery

Diffuse impairment of ventricular function after cardiac surgery may be related to the generation during reperfusion of the myocardium of free radicals derived from oxygen. Fifteen patients undergoing elective coronary bypass surgery were studied by previously described assays for peroxidised lipids and for isomerised lipids which were used as indices of free radical activity. Serial blood samples were obtained from systemic arterial, mixed venous, and coronary sinus catheters before, during, and after the ischaemic period. The patients underwent coronary artery surgery on cardiopulmonary bypass with a membrane oxygenator, relative hypothermia 30-34 degrees C, and intermittent cross-clamping of the aorta. During the ischaemic periods there were no significant changes in the indices of free radical activity. During the reperfusion phase there was a significant increase in free radical indices in arterial and mixed venous blood. A small rise in free radical indices in coronary venous blood was not statistically significant. These data indicate that free radical activity is increased in patients shortly after the cessation of cardiopulmonary bypass. The pattern of distribution between the different sampling sites suggests that much of the observed increase in isomerised and peroxidised lipids originates from tissues other than the myocardium.