Impact of unstable angina on operative mortality with coronary revascularization at varying time intervals after myocardial infarction

Optimal timing of coronary artery bypass grafting in acute myocardial infarction

The timing of surgical coronary artery revascularization after an acute myocardial infarction is not well defined. The inherent difficulties of mobilizing a surgical team at odd hours has led to the adoption of a percutaneous coronary intervention strategy when possible or a clot-busting drug regimen when percutaneous coronary intervention is not available. Despite the difficulties and risks of surgical revascularization, there are situations where it may be indicated. We conducted a review of the literature to better understand the timing, scope, and risks of surgical coronary revascularization after an acute myocardial infarction.

Timing of bypass surgery in stable patients after acute myocardial infarction

OBJECTIVES

To determine the optimal timing for bypass surgery in stable patients after acute myocardial infarction (MI).

BACKGROUND

Coronary artery bypass graft surgery (CABG) is a proven treatment for coronary artery disease. Because of the hypothesized risk of hemorrhagic transformation, it had become common practice to wait four to six weeks after MI. Recently, improvements in surgical and perioperative management, as well as an increase in pre-CABG in-hospital waiting times and excess burden on health care resources, have pushed surgeons to operate earlier. The optimal timing for a stable patient to undergo CABG after MI is unclear, because there have been no randomized trials to answer this question.

METHODS

The published literature comparing early versus late surgical revascularization procedures in stable post-MI patients was reviewed.

RESULTS

No randomized, prospective trials were found; however, several retrospective studies were identified. Most series examining Q wave MIs showed that mortality is higher in the early stages post-MI and progressively decreases with time post-MI. When studies examined non-Q wave MIs separately, there appeared to be less of a mortality difference between early and late surgical revascularization. There was a large disparity between the definitions of early surgery post-MI among the studies, some as early as 6 h and others up to eight days. Factors that increased mortality include abnormal left ventricular function and urgency of surgery, and some studies found risk models helpful to define increased risk after infarction. The possible increased risk of early surgery may be balanced against the potential for improved remodelling, improved quality of life and decreased hospital stay costs.

CONCLUSIONS

There is a need for a randomized, prospective trial examining the optimal timing for CABG in stable post-MI patients.

On-pump beating-heart coronary artery bypass grafting for acute myocardial infarction

BACKGROUND

The early results of emergent coronary artery bypass grafting by conventional operative method for acute myocardial infarction are reported to be poor. The purpose of this study is to evaluate on-pump beating-heart coronary artery bypass grafting for acute myocardial infarction.

METHODS

Thirty-one patients with acute myocardial infarction underwent emergent surgery between January 1998 and June 2004 at Nayoro City General Hospital. In 16 patients, on-pump surgery was performed on the arrested heart, and in the other 15, on-pump surgery was performed on the beating heart. Early results were compared between the two groups.

RESULTS

Preoperative and perioperative patient characteristics revealed no significant differences between the two groups. Although there was no statistically difference between the two groups, the early mortality rates of on-pump arrested-heart coronary bypass grafting (31.3%) was higher than that of on-pump beating-heart coronary bypass grafting (13.3%). Postoperatively, the creatine kinase myocardial band value for the on-pump beating-heart group was significantly lower than that for the on-pump arrested-heart group (221 +/- 200 IU/L versus 666 +/- 540 IU/L, p = 0.008). The incidence of postoperative acute renal failure was significantly higher in the on-pump arrested-heart group than in the on-pump beating-heart group (p = 0.034). The durations of ventilator use and inotropic agent use were longer in the on-pump arrested-heart group than in the on-pump beating-heart group, though the differences were not statistically different (p = 0.152, p = 0.223).

CONCLUSIONS

On-pump beating-heart coronary artery bypass grafting has the possibility to eliminate intraoperative global myocardial ischemia and to be an acceptable surgical option for acute myocardial infarction associated with lower postoperative mortality and morbidity.

Off-Pump Coronary Artery Bypass Grafting for Acute Myocardial Infarction

BACKGROUND

The aim of this study was to evaluate the surgical results of off-pump coronary artery bypass grafting (OPCAB) for patients with acute myocardial infarction (AMI) within 14 days of the infarction.

METHODS AND RESULTS

From April 2000 to January 2005 among 841 patients who underwent OPCAB, 43 consecutive patients (5.1%) were examined. Mean age at operation was 69.5 years and mean time from the onset of AMI to surgery was 4.6 days. Seventeen patients (39.5%) had left main trunk disease. Three patients (7.0%) underwent OPCAB following unsuccessful percutaneous coronary intervention, and 1 patient (2.3%) underwent redo procedure 9 years after previous coronary artery bypass grafting (CABG). Six patients (14%) were admitted in cardiogenic shock. Intraaortic balloon pumping was inserted preoperatively in 20 patients (46.5%). The average maximum creatine kinase-myocardial band was 139+/-181 (U/L). The mean number of grafts was 3.2 and the rate of complete revascularization was 91%. Two of six patients with preoperative cardiogenic shock were converted to on-pump beating CABG due to ventricular arrythmia. The early graft patency rate was 98%. All patients survived except 2 with preoperative cardiogenic shock.

CONCLUSIONS

OPCAB can be performed after AMI as a relatively low-risk procedure with an acceptable mortality rate, even within 14 days of the infarction.

Evaluation of coronary artery bypass grafting in acute myocardial infarction

OBJECTIVES

We evaluated coronary artery bypass grafting (CABG) in acute myocardial infarction (AMI) within 14 days of onset.

METHODS

Of 1,450 patients undergoing isolated CABG in the last 12 years we retrospectively analyzed operative risk factors and studied the use of CABG in treating AMI in 66 undergoing surgery during the AMI phase. We divided them into 2 groups: Group D (deceased: n = 8) and Group S (survivors: n = 58).

RESULTS

Total operative mortality was 12.1% (8/66). Univariate analysis showed the following preoperative parameters to be significant in Group D: diabetes mellitus, cardiogenic shock, shortness of the interval between AMI onset and surgery, mean peak creatine phosphokinase-MB, AMI of the left main trunk, and failed recanalization of the infarcted artery. Multivariate analysis showed diabetes mellitus, cardiogenic shock, and AMI of the left main trunk as independent risk factors for hospital mortality. Intra-operative parameters between groups showed no statistical difference. Mortality in patients who did not suffer cardiogenic shock was zero.

CONCLUSION

Maintenance of hemodynamics in the early phase is vital in treating AMI. The most important element in surgical intervention is revascularization of main branches. We concluded that CABG in AMI involves relatively low risk.

Functional status outcomes of patients with a coronary artery bypass graft over time

OBJECTIVE

To examine functional status outcomes among patients with a coronary artery bypass graft (CABG) over time (ie, at baseline; 3 months, 6 months, and 12 months after surgery) and the impact of selected patient characteristics (ie, age, sex, comorbidities, and cardiac rehabilitation participation) on functional outcomes.

DESIGN

A prospective, repeated-measures design was used to examine functional status in patients with a CABG over time.

SETTING

A midwestern community hospital and regional cardiac referral center was the setting for enrolling patients with a CABG.

OUTCOME MEASURES

Functional status outcomes were measured by using the Medical Outcomes Study (MOS) Short Form 36 (SF-36) and Modified 7-Day Activity instruments.

METHODS

Baseline data were obtained by patient interview in the hospital setting after CABG surgery. At 3 months, 6 months, and 12 months after surgery, telephone interviews were conducted to administer research instruments.

RESULTS

Baseline scores on 7 of the 8 subscales of the MOS SF-36 were significantly lower than at 3 months, 6 months, or 12 months after surgery. Role-emotional functioning baseline scores were not significantly lower than 3-month scores; however, baseline scores were significantly lower than 6-month and 12-month scores. Three-month subscale scores were also significantly lower than 6-month or 12-month scores except for the subscales measuring social and general health functioning. Functional status as measured by the Modified 7-Day Activity tool did not demonstrate any significant differences between 3-month, 6-month, or 12-month activity levels. There were no significant differences by age group on any of the 8 subscales of the MOS SF-36 instrument. Women and subjects with more than 1 comorbidity had a significantly lower preoperative level of physical functioning. Cardiac rehabilitation participants had lower preoperative scores on role-emotional functioning than subjects who were not in rehabilitation.

CONCLUSION

Findings from this study can assist nurses and other health care workers to gain a perspective of the recovery and rehabilitation trajectory of patients with a CABG. The results of the study provide a basis for determining areas of functional limitations during recovery from CABG surgery. Study results can also be the foundation for evaluating outcomes of patients with a CABG when specific interventions (eg, pain management, psychosocial support, physical strengthening, fatigue management) are implemented during hospitalization, home recovery, and rehabilitation to target optimal psychosocial and physiologic functioning of patients with a CABG.

Myocardial revascularisation after acute myocardial infarction

One hundred and twenty-three patients had coronary artery bypass grafting (CABG) within 30 days of acute myocardial infarction (AMI) from May 1992 to November 1997. Commonest infarct was anterior transmural (61.8%) and commonest indication of surgery was post-infarct persistent or recurrent angina (69.1%). Ten patients were operated within 48 h and 36 between 48 h to 2 weeks of having MI. Out of these, nine patients were having infarct extension and cardiogenic shock at the time of surgery. Pre-operatively fourteen patients were on inotropes of which six also had intra-aortic balloon pump (IABP) support. All patients had complete revascularisation with 3.8+/-1.2 distal anastomoses per patient. By multivariate analysis, we found that independent predictors of post-operative morbidity [inotropes >48 h, use of IABP, ventilation >24 h, ICU stay >5 days] and complications [re-exploration, arrhythmias, pulmonary complications, wound infection, cerebrovascular accident (CVA)] were left ventricular ejection fraction (LVEF) <30%, Q-wave MI, surgery <48 h after AMI, presence of pre-operative cardiogenic shock and age >60 years (P < or = 0.01). Mortality at 30 days was 3.3%. LVEF <30%, Q-wave MI, surgery <48 h after AMI, presence of pre-operative cardiogenic shock and age >60 years were found to be independent predictors of 30 days mortality (P < or = 0.01). Ninety patients were followed up for a mean duration of 33 months (1 to 65 months). There were three late deaths and five patients developed recurrence of angina. To conclude, CABG can be carried out with low risk following AMI in stable patients for post-infarct angina. Patients who undergo urgent or emergent surgery and who have pre-operative cardiogenic shock, IABP, poor left ventricular functions, age >60 years and Q-wave MI are at increased risk.

Management of high-risk subsets in unstable angina

This article focuses on the optimal treatment of postinfarction, refractory, or recurrent angina based on the results of recent clinical trials. Many of our recommendations hold true for the general management of unstable angina, but special considerations for the high-risk subsets are emphasized. Specifically, we discuss acute medical management and suggest that an early aggressive strategy that leads to early coronary angiography with the goal of revascularization when feasible best serves this subset. A special emphasis on the emerging role of glycoprotein IIb-IIIa antagonists is made because the important role of platelets in coronary thrombosis has dominated recent views on the pathophysiology of unstable angina.

Cardiovascular surgery in the elderly

The elderly segment of the population is increasing rapidly, and surgeons are more frequently being requested to operate on this group of patients. A number of reports suggest that elderly patients have a significantly higher incidence of operative mortality and 30-day hospital mortality as compared with younger patients. Elderly patients also had a significantly higher increased incidence of complications, such as renal failure, prolonged ventilation, and incidence of strokes and postoperative cardiac arrest. Regarding coronary artery disease, elderly patients are more acutely sick on admission, are more likely to have triple-vessel disease, more likely have comorbid disease, and are usually less likely to receive an internal mammary artery graft. The presence of valvular disorders with concomitant coronary disease (especially mitral ischemic related valve disease) increases operative time, morbidity, and mortality. Efforts must continue to be made to gather data on outcomes of cardiac surgery in the elderly. Consideration must be given to modify the operative approach that minimizes cardiopulmonary bypass time, mitigates the multisystem organ injury associated with cardiopulmonary bypass, and decreases the likelihood of embolization from the ascending aorta. Future efforts must be made to develop measures to decrease the complications rate identified in elderly patients.

Danish multicenter randomized study of invasive versus conservative treatment in patients with inducible ischemia after thrombolysis in acute myocardial infarction (DANAMI). DANish trial in Acute Myocardial Infarction

BACKGROUND

The aim of the DANish trial in Acute Myocardial Infarction (DANAMI) study was to compare an invasive strategy of percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) with a conservative strategy in patients with inducible myocardial ischemia who received thrombolytic treatment for a first acute myocardial infarction (AMI).

METHODS AND RESULTS

Of the 503 patients randomized to an invasive strategy, PTCA was performed in 266 (52.9%) and CABG in 147 (29.2%) from 2 to 10 weeks after the AMI. Of the 505 patients in the conservative treatment group, only 8 (1.6%) had been revascularized 2 months after the AMI. The patients were followed up from 1 to 4.5 years. The primary end points were mortality, reinfarction, and admission with unstable angina. At 2.4 years' follow-up (median), mortality was 3.6% in the invasive treatment group and 4.4% in the conservative treatment group (not significant). Invasive treatment was associated with a lower incidence of AMI (5.6% versus 10.5%; P=.0038) and a lower incidence of admission for unstable angina (17.9% versus 29.5%; P<.00001). The percentages of patients with a primary end point were 15.4% and 29.5% at 1 year, 23.5% and 36.6% at 2 years, and 31.7% versus 44.0% at 4 years (P=<.00001) in the invasive and conservative treatment groups, respectively. At 12 months, stable angina pectoris was present in 21% of patients in the invasive treatment group and 43% in the conservative treatment group.

CONCLUSIONS

Invasive treatment in post-AMI patients with inducible ischemia results in a reduction in the incidence of reinfarction, fewer admissions due to unstable angina, and lower prevalence of stable angina. We conclude that patients with inducible ischemia before discharge who have received treatment with thrombolytic drugs for their first AMI should be referred to coronary arteriography and revascularized accordingly.

Coronary revascularization surgery after myocardial infarction: impact of bypass surgery on survival after thrombolysis. GUSTO Investigators. Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries

OBJECTIVES

This study sought to investigate the impact of surgical revascularization on outcome after myocardial infarction.

BACKGROUND

Small variations in rates of coronary artery bypass graft surgery (CABG) were noted among thrombolytic regimens in the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO) trial, prompting the question of whether survival differences were partly related to differences in CABG rates.

METHODS

Patients in the GUSTO trial were randomized to one of four thrombolytic strategies. Of 40,861 patients with complete data, 3,526 underwent surgical revascularization during their initial hospital admission. Thirty-day and 1-year mortality rates were estimated using Kaplan-Meier techniques, and the impact of CABG as a time-dependent covariate on death was evaluated using a Cox survival model, adjusting for baseline prognostic factors.

RESULTS

The median time from study enrollment to CABG was 7 days across treatment groups. A 15% reduction in mortality for the tissue-type plasminogen activator (t-PA)-treated group was evident by the seventh day. Bypass surgery was a significant independent predictor of 30-day mortality (risk ratio 1.87) and a weaker predictor of 1-year mortality (risk ratio 1.21). Operative mortality was highest in patients with acute mitral regurgitation, ventricular septal defect or poor left ventricular function and in those undergoing CABG within the first 4 days of randomization.

CONCLUSIONS

The survival benefit of accelerated t-PA was not related to surgical revascularization. Bypass surgery was associated with excess mortality in the first year, but the added short-term mortality associated with CABG may be balanced by anticipated long-term benefit in specific groups of patients.

Inappropriate use of bivariable analysis to screen risk factors for use in multivariable analysis

The use of bivariable selection (BVS) for selecting variables to be used in multivariable analysis is inappropriate despite its common usage in medical sciences. In BVS, if the statistical p value of a risk factor in bivariable analysis is greater than an arbitrary value (often p = 0.05), then this factor will not be allowed to compete for inclusion in multivariable analysis. This type of variable selection is inappropriate because the BVS method wrongly rejects potentially important variables when the relationship between an outcome and a risk factor is confounded by any confounder and when this confounder is not properly controlled. This article uses both hypothetical and actual data to show how a nonsignificant risk factor in bivariable analysis may actually be a significant risk factor in multivariable analysis if confounding is properly controlled. Furthermore, problems resulting from the automated forward and stepwise modeling with or without the presence of confounding are also addressed. To avoid these improper procedures and deficiencies, alternatives in performing multivariable analysis, including advantages and disadvantages of the BVS method and automated stepwise modeling, are reviewed and discussed.

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)

Coronary revascularization in the elderly: determinants of operative mortality

Over a 13-year period, 668 patients 70 years of age or older underwent isolated primary coronary artery bypass grafting at our institution. There were 472 men and 196 women, ranging from 70 to 90 years of age (median age, 74 years). Hospital mortality was 5.2% (35/668). In patients 70 to 79 years of age, hospital mortality was 4.2% (25/600), whereas in patients 80 years of age or older, mortality was 14.7% (10/68; p < 0.001). Twenty-seven clinical or hemodynamic variables hypothesized as predictors of operative mortality were examined. Mortality was higher in women than in men (9% versus 3.6%; p = 0.006). Those who died were a mean of 3 years older (77 versus 74 years old; p < 0.05) and were more likely to have unstable angina or Canadian class III or IV angina (p < 0.01). Patients requiring urgent operations, preoperative intraaortic balloon assist, intravenous nitroglycerin, or inotropic agents, and those with preoperative hypotension or cardiac arrest were most likely to die in the hospital (p < 0.001). Multivariate logistic regression analysis revealed advancing age, female sex, bypass time, urgency of operation, preoperative cardiac arrest, and unstable angina as primary determinants of mortality (p < 0.05). Although mortality after coronary artery bypass grafting increases with age, the greatest risk of death is in the acutely ill patient with few options for management other than surgical intervention.

Combination antithrombotic therapy in unstable rest angina and non-Q-wave infarction in nonprior aspirin users. Primary end points analysis from the ATACS trial. Antithrombotic Therapy in Acute Coronary Syndromes Research Group

BACKGROUND

The purpose of this study was to compare combination antithrombotic therapy with aspirin plus anticoagulation versus aspirin alone, when added to conventional antianginal therapy in patients with unstable rest angina or non-Q-wave myocardial infarction who were nonprior aspirin users.

METHODS AND RESULTS

Two hundred fourteen patients were randomized; 109 were randomized to receive aspirin alone (162.5 mg daily) and 105 to receive a combination of aspirin plus anticoagulation, ie, aspirin 162.5 mg daily plus heparin (activated partial thromboplastin time, two times control) followed by aspirin 162.5 mg daily plus warfarin (international normalized ratio, 2 to 3). Trial therapy was begun by 9.5 +/- 8.8 hours of qualifying pain and was continued for 12 weeks. Primary end points were recurrent angina with ECG changes, myocardial infarction, and/or death. Analysis by intention to treat of primary events at 12 weeks was performed. At 14 days, there was a significant reduction in total ischemic events in the combination group versus aspirin alone (10.5% versus 27%, P = .004). An efficacy analysis of primary events at 12 weeks also revealed a large reduction in total ischemic events in the combination group versus aspirin alone (13% versus 25%, P = .06). Bleeding complications were slightly more common with combination therapy.

CONCLUSIONS

In nonprior aspirin users, combination antithrombotic therapy with aspirin plus anticoagulation significantly reduces recurrent ischemic events in the early phase of unstable angina.

One-year prognosis in patients hospitalized with a history of unstable angina pectoris

The prognosis during 1 year of follow-up in 715 patients admitted to one single hospital due to suspected acute myocardial infarction (AMI) with a history of unstable angina pectoris immediately preceding hospitalization is described. AMI developed in 192 patients (27%) during the first three days and in 255 patients (38%) during the first year. The mortality during hospitalization was 7% (50 patients) and during 1 year 19% (130 patients). Of the nonsurvivors, 54% died of AMI, 28% of congestive heart failure, and 20% of cardiogenic shock. Based on simple clinical parameters on admission to the emergency room, risk indicators for death during the following year could be identified as follows, in the order of significance: high age (p < 0.001), ST-segment depression on admission (p < 0.001), and a history of diabetes mellitus (p < 0.05). At admission to the emergency room, risk indicators for development of AMI during the following year were as follows: initial degree of suspicion of AMI (p < 0.001), electrocardiographic signs of acute ischemia on admission (p < 0.001), ST-segment elevation on admission (p < 0.01), age (p < 0.05), and lack of a previous history of chronic stable angina pectoris (p < 0.05). We conclude that, among patients admitted to hospital due to suspected AMI with a history of unstable angina pectoris immediately preceding hospitalization, 38% developed a confirmed infarction and 19% died during the following year.