Increased risk of urgent revascularization

Effect of Aortic Cross-Clamp Time on Myocardial Infarction after Coronary Bypass Surgery

Univariate and multivariate statistical analyses were applied to 1200 consecutive patients undergoing first-time myocardial revascularization. Forty-three patients (3.6%) developed evidence of myocardial infarction as judged by serial electrocardiograms and release of enzymes. Out of 23 preoperative and intraoperative potential risk factors for perioperative myocardial infarction, multivariate regression analysis revealed that duration of aortic cross-clamping was a powerful continuous variable risk factor. The relative risk increased twofold at 44 minutes compared to 17 minutes, approached three times the risk at 53 minutes, and reached more than six times the risk after 84 minutes of aortic cross-clamping. Two other independent predictors for perioperative myocardial infarction were identified: the presence of preoperative arterial hypertension and significant (> 75%) left main coronary artery stenosis. Left ventricular impairment, gender, age, severity of angina, and the number of distal anastomoses were not identified as risk factors for perioperative myocardial infarction. Our data indicate that the incidence of perioperative myocardial infarction may be reduced by consistent efforts to minimize aortic cross-clamp time without compromising the adequacy of myocardial revascularization.

Profile of Coronary Artery Bypass Surgery in United Arab Emirates: Dubai Hospital Experience

Although coronary artery bypass surgery has become a common procedure, there were no data available regarding this type of surgery in the United Arab Emirates. Therefore, we undertook this retrospective study of the first 522 consecutive patients undergoing coronary artery bypass graft surgery between October 1992 and July 1997. The mean age was 49.1 years at operation with a 97.1% male predominance. Patients of Asian origin accounted for 75.8%, Arabs 22.4%, and Europeans 1.7%. Chronic stable angina was the most frequent presenting symptom (70.4%) and 62.1% patients had at least one prior myocardial infarction. There was a 44.6% incidence of hypertension and 32.9% of patients were diabetic. Other prominent risk factors were smoking (55.7%), hyperlipidemia (53.9%), and family history of ischemic heart disease (10.7%). Left main coronary artery obstruction was evident in 6.5% of patients. An average of 3.4 grafts per patient were performed using reverse saphenous vein and endarterectomies were needed in 2.2%. The early mortality rate in elective cases was 2.4%. This study suggests that in spite of a high incidence of multiple risk factors, our patients tolerated coronary artery bypass surgery well. Our findings highlight the trend towards more urgent operations and the decreasing age of patients with severe coronary artery disease.

Amputation and cardiac comorbidity: analysis of severity of cardiac risk

OBJECTIVE

To evaluate population-based cardiovascular risk scores and coronary artery calcification scores (CACS) in amputees.

DESIGN

A retrospective cohort study of 1300 veterans in a cardiac computed tomography database.

SETTING

1B Veterans Administration medical center.

PARTICIPANTS

A total of 76 amputees and similar number of age-, gender-, and Framingham Risk Scores (FRS)-matched control subjects.

METHODS

The amputee population was identified and compared for CACS and traditional cardiac risk factors. Two control groups were used: control group 1, with known risk factors including diabetes mellitus, and control group 2, with all risk factors without diabetes mellitus.

MAIN OUTCOME MEASURES

Statistical associations between amputee and control group FRS scores, CACS, and other cardiac risk factors were assessed.

RESULTS

The study included 57 nontraumatic and 19 traumatic amputees with an average age of 62.4 years. Sixty-six amputees were in the low-to-intermediate cardiac risk groups according to FRS. Despite this classification, the mean CACS were significantly higher in amputees (1285 ± 18) than in either of the control groups: control group 1 (540 ± 84) and control group 2 (481 ± 11), P < .001. CACS also were significantly higher in the nontraumatic subject group (1595 ± 12) compared with the traumatic group (356 ± 57; P < .001). Upon categorization of CACS based on probability of coronary artery disease (CAD), 76% of amputees had a CACS >100 and 38% of amputees had a CACS >1000. Interestingly, CACS were almost the same in finger/toe amputations compared with an above-knee amputation, indicating an already ongoing CAD process irrespective of level of amputation. The predominant clinical significant cardiac risk factors in amputees are hypertension (89.5%), P < .005; chronic kidney disease (31.6%), P < .001; dyslipidemia (72.4%), P < .04; and insulin resistance. Total cholesterol, low-density lipoprotein, and high-density lipoprotein levels were nonsignificantly low in all amputees. Triglycerides were particularly higher in traumatic patients compared with nontraumatic patients, with the triglycerides/high-density lipoprotein ratio >7.

CONCLUSION

This study demonstrates that amputees have a much greater burden of underlying atherosclerotic disease as detected by CACS than do control subjects matched by Framingham risk stratification. Early screening for CAD and aggressive targeted interventions may be an important part of management to reduce early mortality after amputation.

Clinical outcome of urgent coronary artery bypass grafting

Urgent coronary artery bypass grafting (CABG) has a higher mortality rate than elective CABG. The purpose of this study was to evaluate the clinical outcome of urgent CABG. From July 1992 to May 2005, 104 patients underwent urgent CABG. All patients required an urgent surgical revascularization within 24 hr of diagnostic coronary angiography. In-hospital mortality after urgent CABG was 17.3% (18/104). We compared preoperative characteristics and postoperative clinical outcomes between the survival group (n=86) and the mortality group (n=18). The mean age was 61.7 yr (range, 35-83). The most common cause of mortality was low cardiac output. The independent preoperative risk factors of mortality included advanced age (>70 yr) (OR=3.998, p=0.046), preoperative shock status (OR=6.542, p=0.011), and low ejection fraction (<40%) (OR=4.492, p=0.034). Other risk factors of mortality included prolonged cardiopulmonary bypass time, prolonged ventilator use, and extended intensive care unit stay. The 10-yr actuarial survival rate was 61%. Although the operative mortality rate was high after urgent CABG, a favorable long-term clinical outcome can be expected if the patients survive.

Metoprolol and coronary artery bypass grafting surgery: does intraoperative metoprolol attenuate acute beta-adrenergic receptor desensitization during cardiac surgery?

Cardiac surgery results in significant impairment of beta-adrenergic receptor (beta AR) function and is a cause of depressed myocardial function after surgery. We previously demonstrated that acute administration of beta AR blocker during cardiopulmonary bypass (CPB) in an animal model of coronary artery bypass grafting (CABG) surgery attenuates beta AR desensitization, whereas chronic oral beta-blockade therapy in patients undergoing CABG surgery does not prevent it. Therefore we hypothesized that acute administration of metoprolol during CABG surgery would prevent acute myocardial beta AR desensitization. A placebo-controlled initial phase (n = 72) was performed whereby patients were randomized to either metoprolol 10 mg or placebo immediately before CPB. Then a second dose-finding study was performed where patients received 20 mg (n = 20) or 30 mg (n = 20) of metoprolol. Hemodynamic monitoring, atrial membrane adenylyl cyclase activity, atrial beta AR density, and postoperative outcomes were measured. All groups showed similar decreases in isoproterenol-stimulated adenylyl cyclase activity (13%-24%). Cardiac output remained similar in all 4 groups throughout the intraoperative and postoperative period. In addition, patients receiving metoprolol 20 or 30 mg had less supraventricular arrhythmias 24 h postoperatively compared with patients receiving metoprolol 10 mg or placebo. Therefore, unlike our previous animal model of CABG surgery, metoprolol did not attenuate myocardial beta AR desensitization.

IMPLICATIONS

We investigated whether IV metoprolol given during cardiac surgery attenuates myocardial beta-adrenergic receptor (beta AR) desensitization. Although metoprolol did not reduce beta AR desensitization, the incidence of supraventricular arrhythmias was reduced by 75% in patients receiving 20 mg or 30 mg metoprolol.

The efficacy of preemptive Milrinone or Amrinone therapy in patients undergoing coronary artery bypass grafting

Acute deterioration in ventricular function and oxygen transport is common after cardiac surgery. We hypothesized that milrinone or amrinone may reduce their occurrence and catecholamine requirements and increase cellular enzyme levels in patients undergoing coronary artery bypass. In 45 patients, we randomly administered milrinone 50 microg/kg plus 0.5 microg x kg(-1) x min(-1) infusion for 10 h, amrinone 1.5 mg/kg plus 10 microg x kg(-1) x min(-1) infusion for 10 h, or placebo at release of aortic cross-clamp. Hemodynamic variables, dopamine requirement, and laboratory values were recorded. At the postoperative nadir, stroke volume index was higher in the Milrinone and Amrinone groups (mean +/- SD, 27.8 +/- 4.0 and 26.1 +/- 3.2 vs. 20.4 +/- 5.1 mL x min (-1) x m(-2) per beat, P < 0.0001), and oxygen transport index was higher (354.7 +/- 57.8 and 353.7 +/- 91.2 vs 283.0 +/- 83.9 mL. min(-1) x m(-2), P = 0.009). The postoperative dopamine requirement was less (6.6 +/- 2.7 and 6.8 +/- 2.6 vs 10.4 +/- 2.0 mg/kg, P < 0.008), and postoperative serum lactate, alanine and aspartate aminotransferase, lactate dehydrogenase, creatinine kinase, C-reactive protein, and glucose levels were less (P < 0.01). The mean postoperative heart rate was faster in the Milrinone group than in the Amrinone and Placebo groups (96.8 +/- 10.3 vs. 86.9 +/- 9.5 and 87.8 +/- 10.8 bpm, P < 0.01). Milrinone and amrinone administered preemptively reduce postoperative deterioration in cardiac function and oxygen transport, dopamine requirement, and increases in serum lactate, glucose, and enzyme levels, although milrinone may increase heart rate.

IMPLICATIONS

Preemptive milrinone or amrinone administration before separation from cardiopulmonary bypass in cardiac surgical patients not only ameliorates postoperative deterioration in cardiac function and oxygen transport, but also reduces dopamine requirement and increases serum lactate, glucose, and cellular enzyme levels, although milrinone may increase heart rate.

Inhibition of phosphodiesterase type III before aortic cross-clamping preserves intramyocardial cyclic adenosine monophosphate during cardiopulmonary bypass

Inotropes are often used to treat myocardial dysfunction shortly after cardiopulmonary bypass (CPB). beta-Adrenergic agonists improve contractility, in part by increasing cyclic adenosine monophosphate (cAMP) production, whereas phosphodiesterase type III inhibitors prevent its breakdown. CPB is associated with abnormalities at the beta-receptor level and diminished adenyl cyclase activity, both of which tend to decrease cAMP. These effects may be increased in the presence of preexisting myocardial dysfunction. We tested the hypothesis that inhibition of phosphodiesterase type III before global myocardial ischemia and pharmacologic arrest results in the preservation of intramyocardial cAMP concentration during CPB. Twenty adult patients undergoing coronary artery bypass grafting with CPB were studied. After CPB was instituted, a myocardial biopsy was obtained from the apex of the left ventricle. Patients were randomized to receive either placebo or milrinone (50 micro/kg) through the bypass pump 10 min before aortic cross-clamping. Another myocardial biopsy was performed adjacent to the left ventricular apex just before weaning from CPB. Myocardial cAMP concentration was determined by radioimmunoassay. Myocyte protein content was determined by the Bradford method by using a commercial kit. There were no significant demographic differences between the groups; however, patients in the Milrinone group had a lower left ventricular ejection fraction than placebo (41% +/- 13% vs 53% +/- 7%; P < 0.05). Patients who received milrinone had larger cAMP concentrations at the end of CPB compared with placebo (21 +/- 12.5 pmol/mg protein versus 12.8 +/- 2.2 pmol/mg protein; P < 0.05). The administration of milrinone before aortic cross-clamping is associated with increased intramyocardial cAMP concentration at the end of CPB.

IMPLICATIONS

The administration of a single dose of milrinone before aortic cross-clamping resulted in significantly larger intramyocardial cyclic adenosine monophosphate concentration in myocardial biopsy specimens compared with controls.

Safety and cost-effectiveness of MIDCABG in high-risk CABG patients

BACKGROUND

Myocardial revascularization without cardiopulmonary bypass has been proposed as a potential therapeutic alternative in high-risk patients undergoing coronary artery bypass grafting. To evaluate this possibility we compared 15 high-risk (HR) patients in whom minimally invasive direct coronary artery bypass grafting was used as the method of revascularization with 41 consecutive patients who underwent conventional coronary artery bypass grafting during 1 month.

METHODS

Patients undergoing myocardial revascularization without cardiopulmonary bypass were significantly older than their low-risk (LR) counterparts (72.2 +/- 11.6 versus 63.3 +/- 9.7 years, p = 0.006). The demographic profile for HR versus LR patients was as follows: female patients, 60.0% versus 26.8%, p = 0.02; diabetes, 20.0% versus 24.4%, p = 0.7; prior stroke, 33.3% versus 7.4%, p = 0.03; chronic obstructive pulmonary disease, 60.0% versus 9.8%, p < 0.0001; peripheral vascular disease, 33.3% versus 12.2%, p = 0.03, congestive heart failure, 26.6% versus 9.8%, p = 0.09; impaired left ventricular (ejection fraction < 0.40), 40.0% versus 17.0%, p = 0.07; urgent operation, 86.6% versus 46.3%, p < 0.0001; and redo operation, 20.0% versus 0%, p = 0.003.

RESULTS

There were no deaths in the HR group and one death in the LR group. The average intensive care unit stay was 1.1 +/- 0.5 days in HR patients versus 1.6 +/- 1.6 days in LR individuals (p = 0.2), and the average hospital stay was 6.1 +/- 1.8 versus 7.3 +/- 4.4 days, respectively (p = 0.3). We used an acuity risk score index developed by the Adult Cardiac Care Network of Ontario to predict outcome in the HR group. The expected intensive care unit stay in HR patients was 4.1 +/- 1.2 days (versus the observed stay of 1.1 +/- 0.5 days, p < 0.0001), and the expected hospital stay was 12.5 +/- 1.5 days (versus the observed stay of 6.1 +/- 1.8 days, p < 0.0001). The expected mortality in the HR group was 6.1% versus 0%, p = 0.3. A cost regression model was used to examine predicted versus actual cost (in Canadian dollars) for the HR patient cohort (based on Ontario Ministry of Health funding). The expected cost for the HR cohort would have been $11,997 per patient. In contrast, the average cost for these 15 patients was $5,997 per patient, an estimated cost saving of 50%.

CONCLUSIONS

Myocardial revascularization without cardiopulmonary bypass appears to be a safe and cost-effective therapeutic modality for HR patients requiring myocardial revascularization.

Surgical revascularization for acute coronary insufficiency: analysis of risk factors for hospital mortality

BACKGROUND

A retrospective study of 444 patients undergoing urgent and emergent coronary artery bypass grafting for acute coronary insufficiency was performed to identify the risk factors for hospital death specifically associated with the clinical severity of the acute coronary insufficiency syndrome.

METHODS

The patients were divided into three groups-urgent, emergent A, and emergent B-on the basis of the evolution of the clinical pattern of the acute coronary insufficiency syndrome on full medical treatment. The three categories were defined as follows: urgent (257 patients), surgical revascularization could be delayed for 24 to 36 hours after surgical consultation because of adequate control of ischemia; emergent A (127 patients), prompt myocardial revascularization was required because medical treatment achieved only transient regression of an unrelenting ischemic pattern; and emergent B (60 patients), prompt myocardial revascularization was required because the acute coronary insufficiency was entirely refractory to medical treatment.

RESULTS

Mortality rates were 7.4% for the urgent group, 13.4% for the emergent A group, and 31.7% for the emergent B group. Multivariate analysis identified the following as risk factors for hospital mortality: ejection fraction (p = 0.023) and aortic cross-clamp time (p = 0.10) for the urgent group; aortic cross-clamp time (p = 0.017), ejection fraction (p = 0.03), and nonuse of blood cardioplegia (p = 0.04) for the emergent A group; and cardiogenic shock (p = 0.00), preoperative ischemic interval (p = 0.00), aortic cross-clamp time (p = 0.018), and nonuse of blood cardioplegia (p = 0.012) for the emergent B group.

CONCLUSIONS

A more exact definition of patient risk can be achieved when predictive outcome models are constructed using the risk factors specifically related to each level of clinical severity of the ischemic syndrome.

Myocardial stunning, hibernation, and ischemic preconditioning

From the present review, it may be concluded that myocardial ischemia results in far more complicated syndromes than previously realized. Although not all aspects of the issues discussed in this review are currently a clinical reality in the daily practice of cardiovascular anesthesiologists, the understanding and application of these concepts are growing rapidly. Indications for revascularization procedures will be adjusted in patients with evidence of hibernating myocardium. In the future, postoperative myocardial dysfunction may be diminished by the prevention of myocardial stunning, for instance by altering the composition of the cardioplegic solution and other interventions. Finally, additional advances may involve reduction of the extent of perioperative myocardial infarctions by application of ischemic preconditioning.

Predictors of low cardiac output syndrome after coronary artery bypass

The purpose of this study was to identify patients at risk for the development of low cardiac output syndrome after coronary artery bypass. Low cardiac output syndrome was defined as the need for postoperative intraaortic balloon pump or inotropic support for longer than 30 minutes in the intensive care unit to maintain the systolic blood pressure greater than 90 mm Hg and the cardiac index greater than 2.2 L/min per square meter. The preoperative patient characteristics that were independent predictors of low cardiac output syndrome were identified among 4558 consecutive patients who underwent isolated coronary artery bypass at The Toronto Hospital between July 1, 1990, and December 31, 1993. The overall prevalence of low cardiac output syndrome was 9.1% (n = 412). The operative mortality rate was higher in patients in whom low cardiac output syndrome developed than in those in whom it did not develop (16.9% versus 0.9%, p < 0.001). Stepwise logistic regression analyses identified nine independent predictors of low output syndrome (percent frequency in parentheses) and calculated the factor-adjusted odds ratios associated with each predictor: (1) left ventricular ejection fraction less than 20% (27%, odds ratio 5.7); (2) repeat operation (25%, odds ratio 4.4); (3) emergency operation (27%, odds ratio 3.7); (4) female gender (16%, odds ratio 2.5); (5) diabetes (13%, odds ratio 1.6); (6) age older than 70 years (13%, odds ratio 1.5); (7) left main coronary artery stenosis (12%, odds ratio 1.4); (8) recent myocardial infarction (16%, odds ratio 1.4); and (9) triple-vessel disease (10%, odds ratio 1.3). Low cardiac output syndrome is a clinical outcome that may result from inadequate myocardial protection or perioperative ischemic injury. Patients at high risk for the development of low cardiac output syndrome should be the focus of trials of new techniques of myocardial protection to resuscitate the ischemic myocardium.

Operation for unstable angina pectoris: factors influencing adverse in-hospital outcome

Coronary artery bypass grafting for the treatment of unstable angina is still associated with increased operative risk and postoperative morbidity. The impact of the extended use of arterial grafts on early results is incompletely defined. In a 7-year period (1986 to 1993), 474 patients (average age, 65 years; range, 34 to 85 years) underwent coronary artery bypass grafting for the treatment of unstable angina. Sixty-eight patients were operated on emergently and 406 urgently. They received an average of 3.0 distal anastomoses (range, 1 to 6). Seventy-nine patients had exclusively venous grafts, 316 had one internal thoracic artery graft, 79 had bilateral internal thoracic artery grafts, and 20 had inferior epigastric artery grafts. Sequential internal thoracic artery grafting was performed in 70 patients. Redo operations were performed in 26 patients. Thirty-four patients (7.2%) experienced a new myocardial infarction. Eighty-nine patients (18.8%) had an intraaortic balloon pump inserted preoperatively, intraoperatively, or postoperatively. Eight patients (1.7%) died intraoperatively and 24 patients (5.1%) died postoperatively. Seventy-seven patients (16.2%) had an adverse outcome, as shown by the need for an intraaortic balloon pump (intraoperatively or postoperatively) or hospital death, or by both. Forty variables were examined by multivariate analysis for their influence on the occurrence of an adverse outcome. Aortic cross-clamp time (p = 0.0004), transfer from the intensive care unit (p = 0.0023), female sex (p = 0.0023), operation performed in early years (p = 0.0041), left ventricular aneurysm (p = 0.0068), the number of diseased coronary vessels (p = 0.0312), and reoperation (p = 0.0318) were all found to be significant independent predictors of increased risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Determinants of the length of stay in intensive care and in hospital after coronary artery surgery

BACKGROUND

Patients who have coronary artery surgery normally occupy intensive care beds for less than 24 hours. Longer stays may result in under use of cardiac surgical capacity. One approach to optimise surgical throughput is prospectively to identify fast track patients--that is, those who occupy an intensive care bed for less than 24 hours. A prospective audit of patients was performed to identify fast track patients by simple clinical criteria. Total length of hospital stay was also assessed in an attempt to predict which patients were likely to have a short postoperative stay, defined as < or = 7 days.

METHODS

Baseline demographic details, cardiovascular risk factors, angiographic and operative details were recorded for 431 consecutive patients who underwent coronary surgery at a regional centre over a nine month period. Outcome measures were the duration of the stay in the intensive care unit in hours and total duration of the postoperative stay in hospital in days. In addition, two groups of patients who were thought to be fast track were identified prospectively. Fast track 1 patients were identified by criteria selected by cardiovascular physicians. These were age less than 60 years, stable angina, good left ventricular function (ejection fraction > 50%), good renal function (serum creatinine < 120 mumol/l), and no obesity, diabetes, or other serious disease. Fast track 2 patients were identified by criteria defined by cardiovascular surgeons. These were male sex, age less than 65 years, good left ventricular function and no peripheral vascular disease, diabetes, or other serious disease. The efficacy of both sets of criteria in predicting outcome was tested.

RESULTS

344 (79.8%) patients were fast track. Significant factors for the prediction of fast track patients by univariate analysis (with positive predictive accuracy and sensitivity) were left ventricular ejection fraction > 50% (83%, 80%), left ventricular end diastolic pressure < 13 mm Hg (90%, 59%), creatinine less than 120 mumol/l (83%, 87%), and one or two vessel coronary disease (89%, 34%). Of the patients categorised as fast track 1 89% proved to be fast track (sensitivity 24%), however, the fast track 2 characteristics were not significant. Age, sex, obesity, diabetes, hypertension, a history of obstructive pulmonary disease and unstable angina were not predictive of the duration of intensive care stay. Multivariate analysis indicated that only left ventricular end diastolic pressure and the number of diseased coronary arteries predicted fast track patients. These criteria separated patients into three groups. Those who were good risk had one or two vessel disease and left ventricular end diastolic pressure < 13 mm Hg. They comprised 19% of the total and 93% of them were fast track. Those who were intermediate risk had either three vessel disease or left ventricular end diastolic pressure > 13 mm Hg but not both. They comprised 49% of the total and 85% of them were fast track. Those who were poor risk had both three vessel disease and left ventricular end diastolic pressure > 13 mm Hg. They comprised 32% of the total and 62% of them were fast track. The 106 (24%) patients who spent < or = 7 days in hospital after surgery were significantly younger (mean (SD) 55(8) v 58(8) years; P < 0.001) with a lower incidence of previous myocardial infarction (positive predictive accuracy 30%, sensitivity 53%), were less likely to have a history of obstructive pulmonary disease (25%, 98%), and more likely to have one or two vessel coronary disease (33%, 41%). They were more likely to have an internal mammary artery as a bypass conduit (27%, 89%) and more likely to need fewer than three distal anastomoses of the vein graft (29%, 63%). By multivariate analysis only age was significantly predictive of hospital stay. Total hospital stay could not be satisfactorily modelled on the basis of the criteria tested here. Sex, obesity, diabetes, hypertension, unstable angina, renal function, and left ventricular function were not associated with hospital stay. CONCLUSIONS-Most patients who had coronary artery surgery spent less than or equal to 24 hours in intensive care, but most spent > 7 days in hospital. The chance of a patient spending less than or equal to 24 hours in intensive care could be predicted by the number of coronary arteries diseased and the left ventricular end diastolic pressure. Poor risks patients (32%) had only a 62% chance of an intensive care unit stay of less than or equal to 24 hours. A policy of scheduling no more than one such patient for surgery per day would be simple to institute and would maximise the use of surgical capacity.

Changes in patients undergoing coronary artery bypass grafting: 1987-1990. Northern New England Cardiovascular Disease Study Group

A prospective study of 7,590 consecutive patients undergoing isolated coronary artery bypass grafting at five medical centers in Maine, New Hampshire, and Vermont between July 1987 and December 1990 assessed changes in patient characteristics over time. Variables included age, sex, surgical priority, ejection fraction, left ventricular end-diastolic pressure, and left main coronary artery stenosis of 90% or greater. Trends were assessed for each variable and for predicted mortality using linear regression. The mean age increased significantly, whereas ejection fraction decreased. The percentage of urgent cases increased, whereas the elective cases became less frequent. No changes were observed in the percentages of emergent cases, female patients, or patients with severe left main coronary artery disease. The predicted in-hospital mortality rose significantly from 4.2% to 5.2% (p < 0.001). The increase in urgent surgical intervention was the most substantial contributor. Subgroup analyses did not support a systematic misclassification of elective patients into the urgent group. This study demonstrates that the characteristics of the cohort of patients undergoing coronary artery bypass grafting changed substantially from 1987 to 1990. These changes should be considered when interpreting surgical outcomes.

Myocardial function in early hours after coronary artery bypass grafting: comparison of two cardioplegic methods

The theoretical advantages of retrograde blood cardioplegia combined with anterograde blood cardioplegia and warm reperfusion before aortic unclamping during coronary surgery were evaluated in 41 patients (group 2). The early postoperative myocardial function of this group was compared with that of 55 patients (group 1) in whom cold crystalloid cardioplegia was administered. The following variables were measured and analyzed by multivariate statistical analysis: heart rate, left atrial pressure, systemic arterial pressure, cardiac index, left ventricular stroke work index, ventricular function, oxygen delivery, hemoglobin, partial oxygen pressure in mixed venous blood, arteriovenous oxygen difference, carbon dioxide production per square meter, and cardiac isoenzyme of creatine-kinase. The myocardial function improved progressively and cardiac enzymatic release was low for both groups 9 hours after admission to the intensive care unit. However, group 2 had significantly higher oxygen delivery, carbon dioxide production per square meter, cardiac index, left ventricular stroke work index, and ventricular function and significantly lower left atrial pressure and mean systemic arterial pressure than that of group 1. The best separation of group 2 from group 1 occurred at the ninth hour, with a probability of correct recognition of 92.1%.

Acute severe postischemic myocardial depression reversed by triiodothyronine

The purpose of this study was to determine the effects of triiodothyronine (T3) on postischemic left ventricular performance and high-energy phosphate content in a severe injury model. Isolated working rat hearts (n = 63) received 20 mL of hyperkalemic NIH No. 1 cardioplegia and were subjected to 20 minutes of ischemia at 37 degrees C. Treated hearts were reperfused with T3-supplemented modified Krebs-Henseleit buffer. Control hearts did not receive T3 supplementation. All treated hearts (n = 44) performed work after ischemia, whereas 26% (5/19) of the control hearts were not able to perform any left ventricular work after ischemia. Comparisons with preischemic values demonstrated significant progressive hemodynamic recovery with increasing concentrations of T3 (0, 0.06, 0.15, and 0.60 ng/mL) with concomitant recovery of left ventricular stroke work index (63%, 72%, 89% [p less than 0.05], and 99% [p less than 0.05], respectively). There were corresponding increases in recovery of aortic flow, systolic pressure, cardiac index, and stroke volume index (p less than 0.05). There were no significant changes in coronary sinus flow or heart rate in any group compared with preischemic values. Comparisons of postischemic high-energy phosphate concentrations also demonstrated no change between treated and untreated groups (p greater than 0.05). We conclude that administration of T3 in a severe left ventricular injury model significantly augments rapid ventricular recovery with no change in postischemic high-energy phosphate concentrations.

Warm heart surgery and results of operation for recent myocardial infarction

Revascularization procedures after recent myocardial infarction are associated with higher mortality and morbidity compared with elective coronary artery bypass grafting. Traditional methods of myocardial protection impose a further ischemic insult on already compromised myocardium. Continuous cold blood cardioplegia may eliminate ischemia but may still leave the heart anaerobic. Theoretically, warm aerobic arrest addresses both of these issues and may become an attractive alternative to standard hypothermic ischemic arrest in this setting. In 115 nonrandomized patients undergoing coronary artery bypass grafting within 6 hours to 7 days of an acute myocardial infarction, myocardial protection was provided with continuous cold (4 degrees C) or continuous warm (37 degrees C) blood cardioplegia. Fifty-one patients (after 1988) protected with warm blood cardioplegia were compared with a historical cohort of 64 patients (before 1988) protected with cold blood cardioplegia. Results indicate that the warm cardioplegia group had no mortality versus 10.9% for the cold group (p less than 0.05), a myocardial infarction rate of 2.0% in the warm versus 9.3% in the cold group, and use of intraaortic balloon pump of 0% versus 12.5%, respectively (p less than 0.05). It is concluded that continuous warm aerobic arrest may minimize ischemia and anaerobic metabolism during the operative procedure, and may be of benefit to patients who have a limited tolerance to ischemic insult.

Cardiac surgery in the octogenarian: perioperative outcome and clinical follow-up

The perioperative and follow-up results of cardiac operations employing extracorporeal circulation and cold cardioplegic arrest were examined in 191 consecutive patients greater than or equal to 80 years of age having surgery over a 5 year period (1982 to 1986). Most patients had severe preoperative symptoms with functional class III (39.8%) or IV (57.1%) limitation. The overall 30 day postoperative cardiac mortality rate was 15.7%. The total in-hospital mortality rate was 18.8%; the mean postoperative hospital stay was 16.4 +/- 13.3 days. The perioperative mortality rate for elective operations was as follows: coronary artery bypass (5.6%), aortic valve replacement (9.6%), aortic valve replacement with coronary bypass (17.9%) and mitral valve surgery with or without coronary bypass (21.4%). Urgent operations were performed in 39 patients (20.4%) with a total perioperative mortality rate of 35.9%; urgent coronary artery bypass was performed in 26 patients (67%) with an in-hospital mortality rate of 23.1%. Clinical evidence of left ventricular failure, functional class IV symptoms, left ventricular ejection fraction less than 50%, mitral valve repair or replacement for severe mitral regurgitation and urgent operation were associated with an increased perioperative mortality rate. Follow-up study in all 155 patients surviving postoperative hospitalization at 22.6 +/- 14.8 months showed significant improvement in symptom status in all surgical subgroups. There were 18 follow-up deaths (11.6%); 10 were noncardiac. The actuarial survival rate of the entire study group was significantly better than that in age- and gender-matched control subjects (p = 0.037).(ABSTRACT TRUNCATED AT 250 WORDS)

Recent preoperative myocardial infarction increases the risk of surgery for unstable angina

Patients with postinfarction angina undergoing surgery for unstable angina face an increased risk of operative mortality. Between January 1982 and December 1987, clinical, angiographic, and operative data was collected prospectively in 588 unstable patients with a prior myocardial infarction within 30 days of surgery (MI) and 5951 unstable patients without preoperative damage (NONMI). MI patients were characterized as being older (age greater than or equal to 70 years: MI, 19.7%; NONMI, 11.6%; p less than 0.001) and having more left ventricular dysfunction (left ventricular ejection fraction less than 40%: MI, 34.8%; NONMI, 26.4%; p less than 0.001). Semi-elective surgery was performed in 82.0% of NONMI patients while 76.9% of MI patients underwent urgent surgery. Operative mortality was increased in MI patients (MI, 11.1%; NONMI, 4.0%; p less than 0.001) which was related to the extent of preoperative MI (non-Q wave, 8.3%; Q wave, 17.5%; p less than 0.001). Stepwise logistic regression analysis identified preoperative MI as an independent risk variable of operative mortality for unstable angina. Separate multivariate analyses were performed to identify the independent predictors for MI and NONMI patients. The multivariate predictors of operative death for MI patients were left ventricular dysfunction, reoperative coronary surgery, nonuse of the internal mammary, age, transmural MI (relative risk 2.11 vs non-Q wave infarction) and left main stenosis. For NONMI patients, the independent variables were urgent operation, left ventricular dysfunction, reoperation, female gender, left main stenosis, and age. The results of this study indicate that recent preoperative MI adversely influences the surgical results in patients with unstable angina. Alternative treatment strategies are warranted for high risk patients, particularly those with transmural MIs and impaired ventricular function.

Risk assessment in urgent/emergent coronary artery surgery

A statistical model has been developed to allow for prediction of individual patient prognosis following urgent/emergent coronary artery bypass grafting (CABG). None of the models previously described for use in coronary artery surgery has been tested with a prospective patient series that confirms the true predictive capacity of the model. Ideally, the predictive ability of such models should be validated with prospective trials. To examine the feasibility of statistical modeling in this clinical context, a computerized model based on the theorem of Bayes was developed to predict operative mortality for urgent coronary artery surgery. The presence or absence of 20 risk factors was determined for each of 405 consecutive patients undergoing urgent coronary artery surgery from January 1984 to January 1989. The first 100 patients were used to develop a database for the model, which was then used to prospectively evaluate the remaining 305 patients. There was good agreement between predicted and observed results. Models of this kind are particularly advantageous because of the ability to (1) accommodate multiple risk factors, (2) become tailored to a specific practice, and (3) determine individual rather than group prognosis. Validation with a prospective trial confirms the practical utility of this approach. This model has reliably predicted the risk associated with urgent coronary artery surgery and may provide important clinical information for the management of patients being evaluated for urgent revascularization.

Seventeen-year experience with bilateral internal mammary artery grafts

The internal mammary artery (IMA) is being recognized as the conduit of choice for myocardial revascularization. From January 1972 through June 1988, 1,087 patients received bilateral IMA and supplemental vein grafts. There were 917 men (84.4%) and 170 women (15.6%) with a mean age of 62.4 years (range, 29 to 84 years). Three hundred ninety-four patients (36.2%) had unstable angina, and 194 (17.8%) had left main coronary artery stenosis greater than 50%. In all, 3,741 coronary grafts were performed, with a mean of 3.4 per patient. Hospital mortality was 2.7% (29 patients). Hospital complications included reoperation for bleeding, 19 patients (1.7%); sternal infection, 16 patients (1.5%); respiratory failure, 35 patients (3.2%); perioperative myocardial infarction, 22 patients (2.0%); and stroke, 20 patients (1.8%). Post-operative arteriography in 53 patients (mean postoperative time, 53.0 months) showed that 92.1% (58/63) of the left IMA and 84.9% (45/53) of the right IMA grafts were patent. Follow-up was completed on 1,058 hospital survivors. There were 82 late deaths (7.8%). The actuarial survival for patients discharged from the hospital was 80.0 +/- 3.2% (plus or minus standard error of the mean) at 10 years and 60.0% +/- 5.0% at 15 years. At follow-up, 866 patients (90.3%) were asymptomatic and in New York Heart Association class I and 68 (7.1%) were in class II. This longitudinal analysis demonstrates that bilateral IMA grafting has a low operative risk and provides excellent long-term functional improvement and survival.

Dipyridamole for coronary artery bypass surgery

A randomized trial to compare the effects of oral and intravenous dipyridamole was conducted in 58 patients undergoing coronary artery bypass graft (CABG) surgery. Preoperative oral administration of dipyridamole resulted in lower plasma drug concentrations in the early postoperative period than perioperative intravenous administration. Postoperative platelet counts were highest in the patients receiving intravenous dipyridamole, intermediate in those receiving oral dipyridamole and lowest in the control group. Postoperative blood loss was significantly reduced with both oral and intravenous dipyridamole. A second randomized trial was conducted in an additional 40 patients undergoing CABG surgery to evaluate the effects of dipyridamole on myocardial platelet and leukocyte deposition and the cardiac release of thromboxane. Twenty patients received intravenous dipyridamole perioperatively. Autologous platelets and leukocytes were labeled with 111In and 99mTc respectively and were infused before release of the crossclamp. Myocardial biopsies were obtained after aortic declamping and indicated that platelets and leukocytes were deposited in the myocardium during reperfusion. Dipyridamole reduced both platelet and leukocyte deposition. Cardiac release of thromboxane B2 occurred in the early postoperative period and was reduced by dipyridamole. In conclusion, dipyridamole preserved platelets and reduced postoperative bleeding and blood product transfusions in patients undergoing CABG surgery. Dipyridamole also reduced cardiac platelet deposition and thromboxane release and may reduce perioperative ischemic injury.

Delayed myocardial metabolic recovery after blood cardioplegia

Previous studies have demonstrated that both myocardial metabolism and ventricular function were depressed after blood cardioplegic arrest for elective coronary artery bypass grafting. To evaluate the etiology of this metabolic defect, we measured the levels of adenine nucleotides and their precursors in 29 patients undergoing elective coronary revascularization. Myocardial biopsy specimens were obtained at 37 degrees C before cardioplegic arrest, immediately after 74 +/- 4 minutes of cardioplegic arrest, and after 30 minutes of reperfusion. Biopsy specimens were analyzed for levels of adenine nucleotides and their precursors by high-performance liquid chromatography. Adenosine triphosphate concentrations decreased with cardioplegic arrest and with reperfusion. Adenosine monophosphate concentrations increased after cardioplegic arrest and remained nearly twice the initial values after reperfusion. The ratio of adenosine monophosphate to adenosine triphosphate doubled after reperfusion, suggesting defective conversion of adenosine monophosphate to adenosine triphosphate. Levels of adenine nucleotide degradation products (adenosine, inosine, and hypoxanthine) increased after cardioplegia and decreased with reperfusion, suggesting a washout of soluble precursors. This study suggests that improvements in myocardial protection should attempt to stimulate mitochondrial energy production and preserve adenine nucleotide precursors.

Coronary artery bypass grafting for unstable angina pectoris: risk analysis

Unstable angina pectoris is a broad, nonspecific diagnosis encompassing a wide variety of clinical syndromes. The intravenous administration of nitroglycerin preoperatively is indicative of a more acute clinical situation, and allows for selection and analysis of a more homogeneous patient population. We reviewed the results of coronary artery bypass grafting for unstable angina defined as angina necessitating intravenous administration of nitroglycerin preoperatively. There were 129 patients (83 men and 46 women) with a mean age of 63.2 years (range, 36 to 86 years). Complications included operative death in 6.2%, postoperative low cardiac output in 11%, and perioperative myocardial infarction in 9%. Twenty perioperative variables were analyzed to identify risk factors for these end points. For operative death, age (p less than 0.05), cross-clamp time (p less than 0.05), and cardiopulmonary bypass time (p less than 0.001) were significant in the univariate analysis, but only age (p less than 0.05, F = 4.6) was an independent predictor using multivariate analysis (stepwise linear regression). For low cardiac output, univariate analysis demonstrated that cross-clamp time (p less than 0.01), preoperative use of an intraaortic balloon for angina (p less than 0.05), left ventricular score (p less than 0.05), number of diseased coronary vessels (p less than 0.05), and cardiopulmonary bypass time (p less than 0.001) were significant variables. However, only use of an intraaortic balloon for angina (p less than 0.0001, F = 14.3) and left ventricular score (p less than 0.005, F = 11.1) were significant independent predictors in the multivariate model. For perioperative myocardial infarction, only diabetes requiring insulin (p less than 0.005) was a significant predictor.

The changing mortality of myocardial revascularization: coronary artery bypass and angioplasty

The risk factors and outcome for the first 150 consecutive patients undergoing coronary artery bypass grafting (CABG) in 1985 (CABG '85) were compared with those of the first 150 patients undergoing CABG in 1975 (CABG '75) and those of the first 150 patients to have percutaneous transluminal coronary angioplasty (PTCA) in 1985 (PTCA '85). The CABG '85 patients had a significantly higher (p less than 0.05) incidence of known operative risk factors including advanced age, female sex, severity of angina, history of recent infarction, triple-vessel disease, left ventricular dysfunction, and emergency operation than the CABG '75 cohort. The clinical profile of the PTCA '85 patients closely resembled the low-risk profile found in the CABG '75 patients. Overall mortality following CABG more than doubled during the decade studied (3% versus 7%, p = 0.07). This study suggests that the increased mortality associated with CABG in 1985 is due in part to the inclusion of more high-risk patients in the surgical population. In addition, the application of PTCA removes low-risk patients from the surgical candidate pool and adds more patients requiring emergency operations, thereby further contributing to the overall decline in the clinical status of patients referred for operation.

Open-heart surgery in octogenarians

One hundred consecutive patients 80 years of age or older consented to and subsequently underwent open-heart operations at our institution between July 1976 and May 1987. Fifty of the patients had aortic valvular disease (28 with coexisting coronary artery disease), and 41 had isolated coronary artery disease. Eight patients had mitral valvular disease, and one had a dissecting aortic aneurysm. Ninety had Class IV disease that was functional, ischemic, or both. The most compelling indications for operation in 85 patients were unstable or postinfarction angina, syncope, acute pulmonary edema, or cardiogenic shock. Twenty-nine patients died soon after operation (within 90 days). New York Heart Association Class IV disease, previous myocardial infarction, cachexia, and emergency operation were preoperative variables associated with early death. Forty-three patients had no complications except for atrial arrhythmias and were discharged from the hospital a mean (+/- SD) of 11.5 +/- 3.7 days after operation. Low cardiac output, acute myocardial infarction, reoperation for bleeding, renal insufficiency, pneumonia, and prolonged endotracheal intubation were the most common serious postoperative complications. Twenty-eight patients who survived postoperative complications were discharged 24.9 +/- 19.6 days after operation. Seventeen patients died 2 to 104 months after discharge from the hospital. Actuarial calculation predicts the survival of 59 percent of patients at three years and 54 percent at five years. Of the 54 patients still alive at this writing, 53 have disease within New York Heart Association and Canadian Cardiovascular Society Classes I or II. For selected octogenarians with unmanageable cardiac symptoms, operation may be an effective therapeutic option.

Use of a Bayesian statistical model for risk assessment in coronary artery surgery

A computerized statistical model based on the theorem of Bayes was developed to predict mortality after coronary artery bypass grafting. From January, 1984, to April, 1987, at our hospital, 700 patients underwent isolated coronary artery bypass grafting. The presence or absence of 20 risk factors was determined for each patient. The first 300 patients formed the initial database of the Bayesian predictive model, and the remaining 400 patients were prospectively evaluated in four groups of 100 each. Each group was prospectively evaluated and then incorporated into the database to update the model. There was good agreement between predicted and observed results. Bayesian theory is particularly suited to this task because it (1) accommodates multiple risk factors, (2) is tailored to one's specific practice, (3) determines individual, rather than group, prognosis, and (4) can be updated with time to compensate for a changing patient population. These flexible attributes are especially valuable in light of recent changes in the coronary artery bypass graft patient profile.

The changing profile of the patient undergoing coronary artery bypass surgery

The first 100 consecutive patients undergoing isolated coronary artery bypass surgery in 1975 were evaluated with respect to the incidence of operative risk factors and outcome. When compared with an identically selected group from 1985, there was significant worsening of the preoperative condition over the decade with regard to mean age (p less than 0.0005), presence of congestive heart failure (p less than 0.05), left ventricular dysfunction (p less than 0.05), severity of coronary artery disease (p less than 0.001) and incidence of emergency operation (p less than 0.05). More patients in 1985 had associated medical diseases such as diabetes (p less than 0.01) and chronic lung disease (p less than 0.005). There was an increase in the occurrence of vascular diseases (hypertension, renal dysfunction, peripheral vascular and cerebrovascular disease) (p less than 0.05). Overall operative mortality increased from 1 to 8% (p less than 0.05) over the decade. Despite the deterioration in the clinical profile of the patient undergoing coronary bypass surgery, elective procedures were still performed with low mortality. The significant increase in overall mortality was chiefly in patients undergoing emergency operation (p less than 0.05). There were also increases in operative morbidity including low output syndrome (p less than 0.01) and respiratory (p less than 0.005) and neurologic (p = 0.06) complications.

Dipyridamole reduced myocardial platelet and leukocyte deposition following ischemia and cardioplegia

Urgent coronary revascularization for acute myocardial ischemia results in an increased mortality and morbidity. Deposition of activated platelets and leukocytes into the ischemic myocardium during reperfusion may augment perioperative ischemic injury. Dipyridamole reduces platelet activation and may reduce myocardial deposition and prevent ischemic injury during reperfusion. The effects of dipyridamole on myocardial platelet and leukocyte deposition were evaluated in a canine model of acute regional myocardial ischemia with reperfusion during cardioplegia on cardiopulmonary bypass. Eight dogs underwent left anterior descending (LAD) coronary artery ligation for 45 min followed by cardiopulmonary bypass and release of the ligature during 60 min of cold crystalloid cardioplegic arrest to simulate urgent revascularization. Four dogs were randomized to receive an infusion of dipyridamole perioperatively (50 mg/hr) and 4 dogs served as controls. Autologous platelets were labeled with 111In, leukocytes with 99mTc, and erythrocytes with 51Cr. The labeled cells were infused immediately after cross-clamp release and myocardial biopsies were obtained at 10, 20, 30, and 60 min of reperfusion. Platelets were deposited in the myocardium during reperfusion and four times more platelets were found in the LAD region than the circumflex region. Leukocyte deposition was similar in the LAD and circumflex regions. Dipyridamole reduced both platelet and leukocyte deposition and the reduction was greater in the LAD than in the circumflex region. Myocardial platelet and leukocyte deposition was found after regional ischemia, cardioplegia, and cardiopulmonary bypass. Dipyridamole reduced myocardial platelet and leukocyte deposition and may reduce perioperative ischemic injury.