Effect of aortocoronary saphenous vein bypass grafting on death and sudden death. Comparison of nonrandomized medically and surgically treated cohorts with comparable coronary disease and left ventricular function

On-Pump Coronary Artery Bypass Graft: The State of the Art

BACKGROUND

Coronary artery bypass grafting (CABG) remains the standard of care for patients with coronary artery disease (CAD). Debate exists concerning several factors, which include percutaneous coronary intervention (PCI) vs. CABG, single vs. bilateral mammary artery grafts, radial artery vs. saphenous vein grafts, right internal mammary artery vs. radial artery grafts, endoscopic vs. open vein-graft harvesting, and on-pump vs. off- pump surgery. Moreover, challenging is the management of diabetic patients with CAD undergoing CABG. This review reports current indications, practice patterns, and outcomes of CABG.

METHODS

Randomized controlled trials comparing CABG to other therapeutical strategies for CAD were searched through MEDLINE, EMBASE, Cochrane databases, and proceedings of international meetings.

RESULTS

Large multicenter randomized and observational studies (SYNTAX, BEST, PRECOMBAT, ASCERT) have reported excellent outcomes in CABG patients, with always fewer rates of operative mortality and major morbidity, than PCI. The 10-year follow-up of ARTS II trial showed no difference between single and bilateral mammary artery. BARI 2D, MASS II, CARDia, FREEDOM trials showed that CABG is the best choice for diabetic patients.

CONCLUSION

CABG still represents one of the most widespread major surgeries, with well-known benefits on symptoms and prognosis in patients with CAD. However, further studies and follow-up data are needed to validate these evidences.

Pathophysiology and prevention of sudden cardiac death

Sudden cardiac death (SCD) is known to occur in individuals with diverse diseases. Each disease state has a specific etiology and pathophysiology, and is diagnosed and treated differently. Etiologies for SCD include cardiac arrhythmias, coronary artery disease, congenital coronary artery anomalies, hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, dilated cardiomyopathy, and aortic valve stenosis. A potential unifying mechanism of SCD in these diseases involves a massive stimulation of the sympathetic nervous system’s stress response and the subsequent elevation of circulating catecholamines. The diagnosis of cardiac diseases that contribute to an increased risk for SCD is accomplished by a combination of different techniques including electrocardiography, echocardiography, magnetic resonance imaging, and invasive cardiac catheterization. Several therapies including anti-arrhythmic drugs, β-blockers, and antiplatelet agents may be used as medical treatment in patients for the prevention of SCD. Invasive therapies including percutaneous angioplasty, coronary artery bypass surgery, and implantable cardioverter-defibrillators are also used in the clinical management of SCD.

The STICH trial (Surgical Treatment for Ischemic Heart Failure): mode-of-death results

OBJECTIVES

This study sought to assess the effect of the addition of coronary artery bypass grafting (CABG) to medical therapy on mode of death in heart failure.

BACKGROUND

Although CABG therapy is widely used in ischemic cardiomyopathy patients, there are no prospective clinical trial data on mode of death.

METHODS

The STICH (Surgical Treatment for Ischemic Heart Failure ) trial compared the strategy of CABG plus medical therapy to medical therapy alone in 1,212 ischemic cardiomyopathy patients with reduced ejection fraction. A clinical events committee adjudicated deaths using pre-specified definitions for mode of death.

RESULTS

In the STICH trial, there were 462 deaths over a median follow-up of 56 months. The addition of CABG therapy tended to reduce cardiovascular deaths (hazard ratio [HR]: 0.83; 95% confidence interval [CI]: 0.68 to 1.03; p = 0.09) and significantly reduced the most common modes of death: sudden death (HR: 0.73; 95% CI: 0.54 to 0.99; p = 0.041) and fatal pump failure events (HR: 0.64; 95% CI: 0.41 to 1.00; p = 0.05). Time-dependent estimates indicate that the protective effect of CABG principally occurred after 24 months in both categories. Deaths post-cardiovascular procedures were increased in CABG patients (HR: 3.11; 95% CI: 1.47 to 6.60), but fatal myocardial infarction deaths were lower (HR: 0.07; 95% CI: 0.01 to 0.57). Noncardiovascular deaths were infrequent and did not differ between groups.

CONCLUSIONS

In the STICH trial, the addition of CABG to medical therapy reduced the most common modes of death: sudden death and fatal pump failure events. The beneficial effects were principally seen after 2 years. Post-procedure deaths were increased in patients randomized to CABG, whereas myocardial infarction deaths were decreased.

The effect of coronary artery bypass grafting on specific causes of long-term mortality in the Bypass Angioplasty Revascularization Investigation

OBJECTIVES

We sought to examine the effect of revascularization with coronary artery bypass grafting on specific causes of death in the Bypass Angioplasty Revascularization Investigation cohort. Although the effect of coronary revascularization on long-term mortality has been previously described, there are limited data describing its effect on specific causes of death in patients with coronary artery disease. Evaluation of cause of death might help elucidate disease mechanisms and be useful for developing treatment strategies.

METHODS

In the Bypass Angioplasty Revascularization Investigation randomized trial and registry, 3610 patients underwent initial revascularization with coronary artery bypass grafting or balloon angioplasty and were followed for an average of 7.7 years. Causes of all deaths were classified by an independent committee.

RESULTS

Among 3610 revascularized patients, 2239 underwent coronary artery bypass grafting as an initial or subsequent procedure. Over 7.7 years of follow-up, 3% of all patients died of sudden cardiac death, 3% died of myocardial infarction-related death, 2% died of congestive heart failure and other cardiac causes, and 9% died of noncardiac causes. Coronary artery bypass grafting (vs no coronary artery bypass grafting) was associated with a significantly lower risk of sudden cardiac death (relative risk, 0.60; P = .01) but was not significantly associated with any other causes of long-term mortality.

CONCLUSIONS

In the Bypass Angioplasty Revascularization Investigation coronary artery bypass grafting significantly decreased the risk of sudden cardiac death but not any other cause of long-term mortality. Because major risk factors for sudden cardiac death have historically favored a revascularization strategy of coronary artery bypass grafting over angioplasty, evaluation of the current practice of extending angioplasty as an alternative to coronary artery bypass grafting in similar high-risk subgroups is paramount.

Surgical coronary revascularization and antiarrhythmic therapy in survivors of out-of-hospital cardiac arrest

BACKGROUND

Patients who survive out-of-hospital cardiac arrest are at high risk for recurrent arrest. Coronary artery bypass grafting (CABG) confers a survival advantage, but it is unclear whether antiarrhythmic drugs or an implanted defibrillator confer added benefit. This study was designed to determine predictors for further treatment, survival, and therapeutic internal cardiac defibrillator (ICD) discharge in this patient population.

METHODS

One hundred and eight patients undergoing CABG after out-of-hospital cardiac arrest were identified over a 12-year period. Case records were retrospectively reviewed. Follow-up was obtained and predictors of outcome events were analyzed.

RESULTS

Fifty-four (50%) patients underwent CABG only. Fifty-four received additional treatment that included ICD placement in 23 (21%), antiarrhythmic medications in 19 (18%), or both in 12 (11%). Predictors of ICD placement included left ventricular ejection fraction (LVEF) less than 40% and perioperative intraaortic balloon counterpulsation. ICD or medical management increased survival in patients with LVEF <40%. Predictors of increased mortality included age >65 years, Cleveland Severity Score >8, and female gender. Predictors of therapeutic ICD discharge included age >65 years, reoperative CABG, LVEF <40%, and positive postoperative electrophysiological (EP) study. No patient with a negative postoperative EP study received an ICD, and none suffered sudden cardiac death during follow-up.

CONCLUSIONS

Patients with coronary artery disease anatomically suitable for CABG who survive an acute out-of-hospital cardiac arrest should undergo EP testing after CABG. Approximately half of these patients are adequately treated by CABG alone. The remainder may benefit from ICD placement or medical antiarrhythmic management.

Prior coronary artery bypass surgery and risk of death among patients with ischemic left ventricular dysfunction

BACKGROUND

Patients with ischemic LV dysfunction are at high risk of sudden death. However, no benefit from prophylactic defibrillator therapy was observed in a group of patients with LV dysfunction undergoing CABG (CABG Patch trial). Thus, the effect of CABG on future risk of sudden death in patients with LV dysfunction is of considerable interest.

METHODS AND RESULTS

Mortality and modes of death in 5410 patients with ischemic LV dysfunction who were enrolled in the Studies of Left Ventricular Dysfunction (SOLVD) trials were evaluated. Outcomes of patients with (n=1870, 35%) versus without (n=3540) history of prior CABG were compared, and stratification by baseline ejection fraction (EF) values (<0.25, 0.25 to 0.30, and >0.30) was performed. Prior CABG was associated with a 25% (95% CI, 15% to 36%) reduction in risk of death and a 46% (95% CI, 30% to 58%) reduction in risk of sudden death independent of EF and severity of heart failure symptoms. As baseline EF declined, absolute reduction in risk of sudden death with prior CABG increased (P<0.01). No alteration in risk of death from progressive heart failure was observed with prior CABG. When these results were applied to a group of patients with LV dysfunction who had not undergone prior surgery (Coronary Artery Surgery Study Registry) predicted annual rates of death (8.2%) and sudden death (2.4%) were similar to those observed in the CABG Patch trial (7.9% and 2.3%, respectively).

CONCLUSIONS

In patients with ischemic LV dysfunction, prior CABG is associated with a significant independent reduction in mortality. These results appear to account for the lack of benefit from defibrillator therapy in the CABG Patch trial.

Effect of antithrombotic therapy on risk of sudden coronary death in patients with congestive heart failure

Data from epidemiologic, autopsy, Holter monitoring, and electrophysiologic studies support the hypothesis that acute myocardial ischemia, even in the absence of myocardial infarction, is a critical component of the pathophysiology of sudden coronary death. Acute myocardial ischemia superimposed upon ventricles damaged from previous infarctions has been demonstrated to enhance the generation of lethal ventricular arrhythmias. This is a retrospective analysis of 6,797 participants in the Studies of Left Ventricular Dysfunction prevention and treatment trials. Both univariate and multivariate Cox proportional-hazards modeling were used to study the association of anticoagulant and antiplatelet therapy with the risk for sudden cardiac death. The following covariates were adjusted for in the analysis: age, ejection fraction, gender, atrial fibrillation, diabetes, a history of angina, prior infarction, prior revascularization, and the regular use of beta blockers, diuretics, digoxin, antiarrhythmic agents, or enalapril. The overall incidence of sudden cardiac death per 100 patient-years of follow-up was 2.24%. In multivariate analysis, antiplatelet and anticoagulant monotherapy each remained independently associated with a reduction in the risk of sudden cardiac death: antiplatelet therapy with a 24% reduction (relative risk [RR] 0.76; 95% confidence interval [CI] 0.61-0.95) and antiplatelet monotherapy with a 32% reduction (RR 0.68; 95% CI 0.48-0.96). Thus, in patients with moderate to severe left ventricular systolic dysfunction resulting from coronary artery disease, antiplatelet and anticoagulant therapy are each associated with a reduction in the risk of sudden cardiac death.

Incidence of implantable defibrillator discharges after coronary revascularization in survivors of ischemic sudden cardiac death

Coronary revascularization has been suggested as sole therapy for secondary prevention of sudden cardiac arrest associated with ischemia. The use of implantable defibrillators (ICD) in combination with coronary revascularization for this patient population is unclear. Among 412 consecutive patients receiving an ICD, 23 (6%) were identified as sudden cardiac arrest survivors who were noninducible with programmed stimulation and had unstable angina or ischemia on a functional study; they underwent successful coronary revascularization. During a follow-up of 34 +/- 18 months, 10 (43%) of the 23 patients received ICD shocks (8 +/- 8 per patient, range 1 to 22 shocks), and nine of the 10 patients had syncope/presyncope associated with at least one ICD discharge. Patients with ICD discharges were compared with those without ICD discharges, and no clinical characteristics were statistically different between the two groups. In conclusion, revascularization alone may be inadequate therapy for survivors of sudden cardiac arrest associated with ischemia who are noninducible with programmed stimulation, and clinical variables cannot predict which patients are likely to have recurrent malignant ventricular arrhythmias.

Impaired left ventricular function, one- or two-vessel coronary artery disease, and severe ischemia: outcome with medical therapy versus revascularization

OBJECTIVE

To determine whether patients with impaired left ventricular function and one- or two-vessel coronary artery disease who manifest severe ischemia during exercise radionuclide angiography have a lower rate of subsequent cardiac events when initial management is revascularization rather than medical therapy.

DESIGN

During a median follow-up of 100 months, we compared the outcome between 37 patients who underwent a revascularization procedure and 22 who received medical therapy at the Mayo Clinic between September 1980 and December 1985.

MATERIAL AND METHODS

The revascularization therapy consisted of coronary artery bypass grafting in 31 patients and coronary angioplasty in 6. Overall survival and survival free of initial cardiac events were compared statistically for the medically and surgically treated patients.

RESULTS

Eleven deaths occurred in the patients who received medical therapy and 9 in the revascularization group. Five-year overall survival was 58% in the medically treated patients versus 84% in the revascularization group. A significant association was noted between type of treatment and overall survival (adjusted chi 2 = 6.20; P = 0.013). Twenty patients had initial cardiac events--7 in the medically treated group (3 cardiac deaths and 4 nonfatal myocardial infarctions) and 13 in the revascularization group (3 cardiac deaths, 3 out-of-hospital cardiac arrests, and 7 nonfatal myocardial infarctions). Survival free of cardiac events at 5 years was 72% in the medically treated patients and 66% in those who underwent revascularization. No association was detected between type of treatment and survival free of cardiac events.

CONCLUSION

These nonrandomized data suggest that overall survival for patients with one- or two-vessel coronary artery disease, impaired left ventricular function, and severe exercise-induced ischemia may be improved by revascularization, but the subsequent cardiac event rates are not.

The effect of coronary bypass graft surgery for the prevention of sudden cardiac death: recurrent episodes after ICD implantation and review of literature

Sudden cardiac death (SCD) accounts for at least 50% of the mortality of patients with ischemic heart failure. Ventricular arrhythmias are responsible for most cases of sudden cardiac death. There is some evidence that coronary artery bypass graft (CABG) surgery may reduce the incidence of recurrent episodes of SCD by prevention of myocardial ischemia. To test the hypothesis that CABG surgery is effective in the prevention of SCD, we compared the recordings of implantable cardioverter defibrillators (ICD) in patients who underwent ICD implantation alone (n = 64) or ICD implantation and concomitant CABG surgery respectively (n = 11). All patients had experienced out of hospital cardiac arrest. ICD recordings were obtained every 3 months and the number of recurrent episodes of ventricular tachycardia (VT) for each time period was noted. Three months following ICD implantation patients in the surgically treated group had an average of one episode of VT per patient as compared to 2.7 episodes in the nonsurgical group. This difference was observed during the following months as well. However, at no time (up to 18 months of follow-up) this difference reached statistical significance. There were no deaths in the surgically treated group. Although we could not demonstrate a statistical significant difference between the two groups, there was a tendency in the surgically treated group to have less episodes of recurrent VT than in the medically treated group. We, therefore, conclude that survivors of SCD presenting with multivessel coronary artery disease (CAD) should undergo coronary artery bypass grafting to prevent myocardial ischemia as the triggering event for lethal ventricular arrhythmias.

Influence of coronary bypass surgery on subsequent outcome of patients resuscitated from out of hospital cardiac arrest

The effect of coronary bypass surgery on recurrent cardiac arrest was estimated in 265 patients resuscitated from out of hospital cardiac arrest between 1970 and 1988. From this cohort, 85 patients (32%) underwent coronary bypass surgery after recovery from cardiac arrest and 180 patients (68%) were treated medically. A multivariate Cox analysis was used to estimate the effect of coronary bypass surgery on subsequent survival after adjusting for effects of age, prior cardiac history, ejection fraction, year of the event, history of angina, antiarrhythmic drug use and whether the arrest was related to acute myocardial infarction. The use of coronary bypass surgery had a significant effect in reducing the incidence of subsequent cardiac arrest during follow-up study (risk ratio [RR] 0.48, 95% confidence interval [CI] 0.24 to 0.97, p less than 0.04). There was also a trend consistent with a reduction in total cardiac mortality (RR 0.65, 95% CI 0.39 to 1.10, p = 0.10). These findings suggest that coronary bypass surgery may reduce the incidence of sudden death in suitable patients resuscitated from an episode of ventricular fibrillation.

Clinical significance of simple heart rate-adjusted ST segment depression in supine leg exercise in the diagnosis of coronary artery disease

To evaluate the clinical significance of simple heart rate-adjusted ST segment depression (delta ST/delta HR) in the diagnosis of coronary artery disease, 42 patients with stable exertional angina underwent supine leg exercise testing and cardiac catheterization. During exercise, heart rate, a multilead electrocardiogram, and pulmonary artery wedge pressure were recorded. The sensitivity and accuracy of the delta ST/delta HR criteria (greater than or equal to 3.0 microV/beat/min) were significantly greater than the conventional analysis of ST segment depression criteria (greater than or equal to 0.2 mV) for detecting three-vessel coronary artery disease at a matched specificity of 72% (100% versus 46%, 81% versus 64%, p less than 0.01). A significant linear correlation was found between maximum pulmonary artery wedge pressure increments during exercise (delta PAWP) or Gensini score and the delta ST/delta HR (delta PAWP: r = 0.51, p less than 0.001; Gensini score: r = 0.47, p less than 0.001). There were no statistically significant differences in the delta PAWP or Gensini score between patients with three-vessel disease who had delta ST/delta HR greater than or equal to 3.0 microV/beat/min and those with one- or two-vessel disease who had delta ST/delta HR greater than or equal to 3.0 microV/beat/min (delta PAWP: 18.1 +/- 2.0 versus 21.9 +/- 3.3, p = NS; Gensini score: 68.5 +/- 6.6 versus 66.3 +/- 11.3, p = NS). These findings demonstrate that delta ST/delta HR is more useful than a conventional analysis of ST segment depression for identifying not only anatomically severe coronary artery disease but also functionally severe coronary artery disease.

Risk stratification of single or double vessel coronary artery disease and impaired left ventricular function using exercise radionuclide angiography

Patients with 3-vessel coronary artery disease (CAD) and normal left ventricular (LV) function have a worse prognosis if they manifest ischemia during exercise testing. The present study determines if exercise radionuclide angiography can aid in the risk stratification of patients with 1- or 2-vessel CAD and impaired LV function (ejection fraction less than 50%). Sixty-five consecutive patients with these findings were followed for a median duration of 24 months (range 12 to 49). Eleven of the 65 patients (17%) had severely ischemic exercise radionuclide angiograms, defined as: a decrease in ejection fraction with exercise; greater than or equal to 1.0 mm of ST-segment depression; and peak exercise workload less than or equal to 600 kg-m/min. During follow-up 11 patients had initial significant cardiac events: 4 cardiac deaths, 1 cardiac arrest, 4 myocardial infarctions and 2 bypass or angioplasty procedures for unstable angina greater than or equal to 3 months after the exercise study. Four of 11 patients (36%) with severely ischemic exercise radionuclide angiograms had events, compared to 7 of 54 patients (13%) without ischemic radionuclide angiograms. Event-free survival at 18 months was 73% for patients with severe exercise ischemia versus 92% for those without ischemia (p less than 0.05). Univariate analysis showed that severe ischemia on radionuclide angiography was the only variable of several tested that significantly predicted future cardiac events (chi-square = 8.16, p less than 0.005). Among patients with 1- or 2-vessel CAD and impaired resting LV function, severe ischemia on exercise radionuclide angiography identifies a subgroup at high risk for future cardiac events.

Sudden cardiac death: etiologies, pathogenesis, and management

Sudden death claims an estimated 350,000 lives per year in the United States. When death occurs within 1 hour of the onset of symptoms, 90% are the result of ventricular tachyarrhythmias. The majority of victims are middle-aged men with coronary artery disease, but in approximately 25%, sudden death is the presenting manifestation of their problem. In some populations, the detection of premature ventricular complexes (PVCs) by ambulatory monitoring is predictive of an increased risk of sudden death. However, the arrhythmia that best predicts this risk is unclear, and ambient arrhythmias are only a modest marker of this risk. Therapy to suppress asymptomatic PVCs has not been shown to be effective in preventing sudden death, and in some cases, lethal arrhythmias can be prevented without significant effects on ambient arrhythmias. Other risk markers such as depressed left ventricular function and the presence of low-amplitude, long-duration, late potentials recorded on a signal averaged electrocardiogram are more powerful predictors of risk than are PVCs. These latter findings in particular support the presence of areas of slow electrical conduction (a requirement for reentrant mechanism arrhythmias) and suggest that an abnormal electrical environment or "substrate" is the most important factor in this problem. The management of patients at risk for sudden death is controversial. While postinfarct survivors with arrhythmias constitute a population at increased risk, the absolute risk is only about 5% in the first year and has not been shown to be improved by conventional antiarrhythmic drugs. Small study size, arrhythmia variability, ill-defined end points, and proarrhythmia may partially explain this apparent lack of efficacy. The prophylactic use of antiarrhythmic drugs other than beta-blockers to prevent sudden death in asymptomatic populations at risk is therefore of unproven benefit. By contrast, patients who have survived a life-threatening arrhythmia unrelated to an acute myocardial infarction have an approximately 30% risk of recurrence in the following year. In these patients, the use of ambulatory monitoring to guide therapy is limited by the high incidence of false-negative responses (lethal arrhythmia recurrence despite ambient arrhythmia suppression) and the lack of frequent spontaneous arrhythmias in many patients. In this patient population, electrophysiological testing can be used to prognosticate recurrence and gain insight into arrhythmia mechanism, stability, and hemodynamic tolerance. The technique is also useful in guiding both pharmacological and nonpharmacological therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Risk factor profiles of patients with sudden cardiac death and death from other cardiac causes: a report from the Coronary Artery Surgery Study (CASS)

Identification of patients at risk of sudden death is essential if optimal preventive treatment strategies are to be developed. In the Coronary Artery Surgery Study (CASS) Registry, 19,946 patients were analyzed to characterize baseline clinical, hemodynamic and angiographic features of patients dying from sudden cardiac death and to compare them with features of patients dying from other cardiac causes, of those dying from noncardiac causes and of survivors. Of the 11,843 medically treated patients, 1,621 died during a mean follow-up period of 5.0 years: death was sudden in 557 (34%), nonsudden but cardiac in 813 (50%) and noncardiac in 251 (16%). In 8,103 surgically treated patients, 824 deaths occurred during a mean follow-up period of 5.1 years: death was sudden in 204 (25%), nonsudden but cardiac in 390 (47%) and noncardiac in 230 (28%). In general, the patients (both medically and surgically treated) who died of cardiac causes, either suddenly or nonsuddenly, were similar to each other but significantly different from patients who either survived or died of noncardiac causes. Although patients with an increased risk of any type of cardiac death could be identified, there were no measures of angiographic or hemodynamic characteristics that were significantly different between patients with sudden cardiac death and those with nonsudden cardiac death. Identification of patients at high risk for sudden cardiac death will require approaches in addition to clinical, angiographic and hemodynamic assessment, such as electrophysiologic assessment or monitoring techniques to identify triggering mechanisms.

Assessment of coronary bypass surgery and percutaneous transluminal coronary angioplasty

Coronary bypass surgery developed as another in a line of surgical procedures dating back more than 60 years. The medical profession at first assessed this procedure with time-honored anecdotal techniques. Gradually, for a variety of reasons, improved methods of comparisons worked their way into assessments of bypass surgery. Randomized controlled trials met resistance but have been very influential. Assessment of percutaneous transluminal coronary angioplasty has benefited from the knowledge generated during the last 25 years, but clinicians have been slower to apply the most advanced techniques.

Comparison of effects of medical and surgical therapy on survival in severe angina pectoris and two-vessel coronary artery disease with and without left ventricular dysfunction: a Coronary Artery Surgery Study Registry Study

This nonrandomized study compared the results of early coronary artery bypass grafting to those of initial medical therapy in a group of 2,023 patients with severe angina pectoris and 2 major epicardial coronary arteries having greater than or equal to 70% diameter luminal narrowing. Medical therapy was selected for 706 patients, and 1,317 patients were treated by coronary artery bypass grafting. The 6-year survival rate was 76% for patients treated medically and 89% for patients treated surgically (p less than 0.0001). Cox multivariate analysis showed that surgical treatment was a beneficial independent predictor of survival (p less than 0.001). For patients with 2-vessel coronary artery disease who had Canadian Heart Association class III and IV angina at presentation, surgical therapy provided a survival advantage for patients with impaired left ventricular function and proximal narrowing of 1 or more coronary arteries.

CASS in retrospect: lessons from the randomized cohort and registry. Coronary Artery Surgery Study

The Coronary Artery Surgery Study (CASS) was a prospective, randomized evaluation of the value of coronary artery bypass grafting compared with medical therapy for stable, mildly symptomatic coronary artery disease. Also, the CASS registry collected clinic information and follow-up data from 24,959 nonconsecutive patients undergoing cardiac catheterization from 1974 to 1979. CASS has had a major impact on current management of the coronary disease patient and represents an important contribution to the cardiovascular knowledge base. Despite the large size and valuable contributions of CASS, its findings have been widely misinterpreted, especially regarding indications for coronary artery bypass surgery. This review examines CASS from the viewpoint of its methodology and some of its many published reports. A full understanding of CASS is requisite to avoid clinical misapplication of the findings of this study.

Efficacy and tolerance of spironolactone in essential hypertension

The long-term efficacy and tolerance of spironolactone in essential hypertension was evaluated among 20,812 patients referred to the Broussais and St. Joseph systemic hypertension clinics between 1976 and 1985 by using information prospectively collected in the computerized ARTEMIS data bank. In 182 patients (51 men, 131 women) treated with spironolactone alone during a mean follow-up period of 23 months, a mean dose of 96.5 mg decreased systolic and diastolic blood pressure (BP) by 18 and 10 mm Hg, respectively, below pretherapeutic levels. The BP decrease was greater with doses of 75 to 100 mg (12.4% and 12.2%) than with doses of 25 to 50 mg (5.3 and 6.5%, p less than 0.001), but no additional decrease was found with doses above 150 mg. Plasma creatinine level increased modestly (8.3 mumol/liters), as did plasma potassium level (0.6 mmol/liters) (both p less than 0.001); uric acid level increased, but not significantly (10.5 mumol/liter). Fasting blood glucose and total cholesterol levels did not change, triglyceride levels increased slightly (0.1 mmol/liter, p less than 0.05). These changes were similar in both sexes and were not influenced by length of follow-up. Among the 699 men prescribed spironolactone alone or in association with another antihypertensive treatment, 91 cases of gynecomastia developed (13%). Gynecomastia was reversible and dose-related; at doses of 50 mg or less the incidence was 6.9%, but 52.2% for doses of 150 mg or higher. Despite limitations inherent in the interpretation of data banks, it is concluded that spironolactone administered in daily practice reduced BP without inducing adverse metabolic adverse effects and that in patients with essential hypertension, doses should be kept below 100 mg.

Prophylactic antiarrhythmic therapy of high-risk survivors of myocardial infarction: lower mortality at 1 month but not at 1 year

To determine whether prophylactic antiarrhythmic therapy influences mortality in high-risk patients after acute myocardial infarction, 143 such patients were randomized in a double-blind individually dose-adjusted, placebo-controlled trial an average of 14 +/- 7 days after myocardial infarction and followed for 1 year. Patients were judged to be at high risk on the basis of (1) ejection fraction less than 40% (n = 60), (2) arrhythmias of Lown class 3 or higher (n = 26), or (3) both (n = 57). Aprindine was chosen because of its long half-life, few side effects, and antiarrhythmic efficacy. Baseline characteristics in the treatment arms did not differ. Holter-detected arrhythmias were reduced in aprindine-treated patients at 3 months (p less than .001) and at 1 year (p less than .001). One patient was lost to follow-up; in the remaining patients 1 year mortality was 20% (28/142; 12 aprindine and 16 placebo). There was no significant difference between the two study arms in overall mortality and sudden death. However, among those who died, median duration of survival was longer in aprindine-treated patients (86 vs 21.5 days) (p = .04). Although antiarrhythmic treatment with aprindine of high-risk patients after myocardial infarction does not affect 1 year survival, mortality appears to be delayed; thus there may be a role for short-term treatment before more definitive therapy such as surgery.

Prediction of left ventricular ejection fraction using simple quantitative clinical information

The left ventricular ejection fraction is useful in characterizing cardiac performance and evaluating prognosis in patients with known or suspected cardiac disease. The purpose of this study was to determine if simple, quantitative clinical information generated as part of a routine patient evaluation could be used to predict ejection fraction determined by radionuclide ventriculography. Multiple regression analysis was used to study a group of 64 patients selected to represent the full range of ejection fraction values. All patients had undergone cardiac catheterization and standard chest radiography in addition to resting and exercise radionuclide ventriculography. Using easily determined clinical variables, a regression formula was developed that predicted the radionuclide ventriculographic ejection fraction (r = 0.73). Plain film heart volume, heart rate, pulse pressure, and thoracic width were highly significant terms in the optimal regression equation. For validation, the formula was applied to a second, independent verification data set composed of 41 cases and revealed similar correlation (r = 0.78). A radionuclide ventriculographic ejection fraction below 40 was identified in the verification data set with a sensitivity of 87 percent and specificity of 83 percent. Use of this method, requiring only direct heart rate, blood pressure, and chest radiographic measurements and simple calculations, may assist physicians in patient management and facilitate the optimal use of more invasive and expensive studies.

The effect of medical and surgical treatment on subsequent sudden cardiac death in patients with coronary artery disease: a report from the Coronary Artery Surgery Study

The effect of medical and surgical treatment on subsequent sudden cardiac death was assessed in 13,476 patients in the Coronary Artery Surgery Study registry who had significant coronary artery disease, operable vessels, and no significant valvular disease. (Patients were assigned to medical or surgical therapy on the basis of clinical judgment and not according to a randomization scheme; therefore, biases associated with unknown variables could not be evaluated.) Sudden cardiac death occurred in 452 patients (3.4%) during a mean follow-up of 4.6 years. Five year survival free of sudden death for medically treated patients was 94 +/- 0.3%, and that for surgically treated patients was 98 +/- 0.2% (p less than .0001). Twelve baseline clinical, electrocardiographic, and angiographic variables were significantly different between patients alive at the last follow-up and those suffering sudden death. Data on these variables were available for 11,508 patients. Sudden death occurred in 257 (4.9%) of 5258 medically treated and 101 (1.6%) of 6250 surgically treated patients. In a high-risk patient subset with three-vessel disease and history of congestive heart failure, 91% of surgically treated patients had not suffered sudden death compared with 69% of medically treated patients. After Cox survival analysis was used to correct for baseline variables, surgical treatment had an independent effect on sudden death (p less than .0001). This reduction was most pronounced in high-risk patients.

Long-term follow-up of survivors of prehospital sudden cardiac death treated with coronary bypass surgery

Although coronary artery bypass surgery is beneficial to patients with severe coronary artery disease, its role in preventing the recurrence of prehospital cardiac arrest in patients is not clear. In this article, we report on the long-term follow-up of 49 survivors of prehospital coronary arrest who had coronary artery bypass surgery. Prior to their prehospital cardiac arrest, 14% of the patients had a history of unstable angina. Coronary angiograms obtained after prehospital cardiac arrest showed that 71% of the patients had three-vessel coronary artery disease and 6% had single-vessel disease. The mean left ventricular ejection fraction was 45%. There were four postoperative deaths; three were caused by pump failure, and one was caused by refractory ventricular arrhythmias. After a maximum follow-up period of 102 months (mean of 55.4 months), there were seven cardiac deaths; five of the patients died of recurrent ventricular fibrillation, and two patients' deaths were related to refractory heart failure. Actuarial analyses of the 49 patients showed that the probability of survival at 6 months, 1 year, 2 years, 3 years, and 5 years was 92%, 92%, 89%, 82%, and 72%, respectively. After surgery, 35 of the 45 patients who were discharged from the hospital were asymptomatic, and 23 of the 32 patients who were employed when their prehospital cardiac arrest occurred returned to their employment. We concluded that coronary artery bypass surgery is beneficial to certain survivors of prehospital sudden death. After surgery, most patients are asymptomatic and capable of returning to their employment and the recurrence of prehospital sudden death is low.

Percutaneous transluminal coronary angioplasty in left main stem coronary stenosis: a five-year appraisal

Left main stem coronary stenosis is now uniformly treated with coronary artery bypass grafting. The advent of percutaneous transluminal coronary angioplasty has permitted a non-operative improvement in myocardial blood flow in many cases of single- and multi-vessel coronary atherosclerosis. The use of percutaneous transluminal coronary angioplasty in left main stem coronary stenosis has been sporadic and controversial. Twenty percutaneous transluminal coronary angioplasties were attempted in 19 patients as the treatment of choice for left main stem coronary stenosis in the past 66 months. The primary success rate was 95% (19/20 patients). The emergency surgery was performed only once (5%), and no death occurred secondary to percutaneous transluminal coronary angioplasty itself. In the follow-up (mean 41 months) period, 12 patients (63%) remained in satisfactory condition with no further need for surgical intervention. Seven patients (37%) ultimately required coronary artery bypass grafting. Although coronary artery bypass grafting will remain the fundamental treatment for left main stem coronary stenosis, this series delineates those anatomic and clinical exceptions wherein percutaneous transluminal coronary angioplasty may be utilized as the primary therapy for left main stem coronary stenosis.

Surgical survival in the Coronary Artery Surgery Study (CASS) registry

The overall surgical survival data in the Coronary Artery Surgery Study (CASS) registry have not been published to date, pending the report of the randomized medical-surgical comparison (CASS randomized trial). Non-randomized surgical survival data from the CASS registry are given in this article. The overall medical survival data from the registry were reported previously as a natural history study. There were 8,991 patients in the registry portion of CASS who had primary isolated coronary artery bypass grafting and 8,971 with follow-up of more than 30 days. The 5-year survival for all 8,971 patients was 90%, and the operative mortality was 2.37%. Patients with left main coronary artery disease had an operative mortality of 3.84% and a 5-year survival of 85%, while patients with lesions in other vessels had an operative mortality of 2.12% and a 5-year survival of 91%. Among patients without left main coronary disease, the 5-year survival was 93% in those with single-vessel and 92% in those with double-vessel disease (operative mortality was 1.50% and 1.92%, respectively) and 88% in patients with triple-vessel disease (operative mortality was 2.62%; p = 0.009). When results for patients with left main coronary artery obstruction were compared with those for triple-vessel disease, the 5-year survival figures were 85% and 88%, respectively (p = 0.02) and the operative mortality, 3.84% and 2.62%, respectively (p = 0.03). Patients with normal or nearly normal left ventricular (LV) function (i.e., LV segmental wall motion scores ranging from 5 through 11) had a 5-year survival of 92% and an operative mortality of 1.97%. Patients with moderate impairment (LV score range, 12 through 16) had a 5-year survival of 80% and an operative mortality of 4.21%. In those with poor ventricular function (LV score of 17 or greater), the 5-year survival was 65% and the operative mortality was 6.21%. The difference in survival among the three groups was significant (p less than 0.0001). Of 29 variables used in a stepwise Cox regression analysis, LV wall motion score, congestive heart failure score, age, number of operable vessels, smoking history, LV end-diastolic pressure, and percent of left main coronary artery stenosis were found to have a significant effect on long-term survival (excluding 30-day mortality), and these variables plus surgical priority and height influenced surgical mortality. When height was used in the Cox proportional hazards model, female sex was no longer a significant variable.

Ischemic cardiomyopathy

The term "ischemic cardiomyopathy" was used initially to describe a clinical syndrome that was indistinguishable from primary congestive cardiomyopathy but due to severe, diffuse coronary artery disease. The term has been expanded to include the larger category of myocardial disease secondary to coronary artery disease. Using this expanded definition, we have discussed the varied clinical presentations of congestive ischemic cardiomyopathy and restrictive ischemic cardiomyopathy (stiff heart syndrome and right ventricular infarction), and how the effects of ischemia on left ventricular systolic and diastolic performance may cause these varied presentations. The prognosis of any ischemic cardiomyopathy is related primarily to the degree of ventricular dysfunction and the extent of coronary artery disease. Therapy is aimed at preventing or ameliorating myocardial ischemia and halting the progression of, or even reversing, the deterioration in myocardial function.

Natural history of severe left ventricular dysfunction after myocardial infarction

The prevalence and prognosis of severe left ventricular dysfunction after infarction was prospectively analyzed in a series of 259 male patients aged 60 years or less surviving an acute myocardial infarction. All patients underwent coronary angiography 30 days after the acute event and were followed up for a mean period of 34 months (range, 15 to 55 months). Forty-five patients (17 percent) were found to have severe left ventricular dysfunction (ejection fraction less than or equal to 30 percent). Comparison of patients with and without severe impairment of left ventricular function showed the former to have a lower cardiac index (p less than 0.001), higher left ventricular end-diastolic volume index (p less than 0.001), and a higher prevalence of three-vessel disease (p less than 0.025) and of total or subtotal occlusion of at least one coronary artery (p less than 0.025). While the occurrence of congestive heart failure was higher in patients with severe left ventricular dysfunction (p less than 0.001), the probability of developing angina was similar in both groups. Cox's regression analysis showed ejection fraction to be the only independent predictor of survival in patients with severe impairment of left ventricular function. An ejection fraction of 20 percent or less identified a subset of patients with the highest mortality (62 percent at four years), significantly different from that of patients whose ejection fraction was between 21 and 30 percent (28 percent) (p less than 0.001).

Exercise testing provides additional prognostic information in angiographically defined subgroups of patients with coronary artery disease

We examined whether exercise testing with measurement of cardiac output during maximal exercise can provide additional prognostic information for medically treated patients in whom left ventricular function and extent of coronary artery disease are known. We followed 1034 patients with normal or mildly impaired left ventricular function; 410 of these patients (group 1) had single-vessel disease, 316 had double-vessel disease (group 2), and 308 had triple-vessel disease (group 3). In addition, 204 patients with double- or triple-vessel disease and moderately impaired left ventricular function (group 4) were followed. Mean follow-up in these 1238 patients was 4.5 years. End point of follow-up was death. Groups 1, 2, and 3 were divided into terciles according to the maximally achieved values of the following exercise variables: exercise tolerance, angina-free exercise tolerance, maximal heart rate, and cardiac output during maximal exercise. Group 4 was divided into halves accordingly. Survival curves (according to the method of Cutler and Ederer) for group 2 showed a 15% difference in 5 year survival rate between the highest and lowest terciles (p less than .005) by use of the noninvasive variables exercise tolerance, angina-free exercise tolerance, and maximal heart rate (95% vs 80%). The separation into terciles according to cardiac output during maximal exercise resulted in a significant difference in survival rates between the highest and lowest terciles (halves) in all groups of patients. The differences in 5 year survival rates were 9% (p less than .05), 16% (p less than .05), and 19% (p less than .005) for groups 1, 2, and 3, respectively, and 22% for group 4 (p less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)

Fifteen year survival study of patients with obstructive coronary artery disease

Survival rates were determined for a group of 598 patients in whom severe coronary disease was demonstrated by arteriography; initially they were treated medically and were followed-up for 15 years. Deaths due to noncoronary causes were uncommon (5% of total) in the first 5 year period but were frequent (36%) in the third period. Survival rates were 48%, 28%, 18%, and 9% for patients with single-, double-, triple-, and left main artery disease, respectively. Abnormalities documented by ventriculography were related to survival. In 386 patients who would have been candidates for bypass surgery, survival rates were 58%, 35%, 26%, and 11% for those with single-, double-, triple-, and left main artery disease, respectively. Cardiac survival curves for single-, double-, and triple-artery disease in candidates for surgery and curves constructed on the basis of 3% mortality per artery per year corresponded fairly closely. When an abnormal electrocardiogram (ECG) is considered as a single variable in multivariate analysis, 5 year survival rates of candidates for surgery were influenced by the following in order of importance: abnormal ECG, symptoms at least 5 years in duration, triple-artery disease, double-artery disease, and arteriosclerosis obliterans. A simple prognostic stratification was devised that used only ECGs and duration of symptoms for each subset based on the number of arteries affected.

Prognostic and predictive value of exertional hypotension in suspected coronary heart disease

The prognostic and predictive value of exertional hypotension was assessed in 1,241 patients having treadmill maximal exercise testing, coronary arteriography, and follow-up averaging 5.4 years. Medically treated patients with coronary artery disease (CAD) with exertional hypotension had poorer survival than did those without such hypotension; however, maximum systolic pressure during exercise was a more powerful predictor of survival. Patients with exertional hypotension had more extensive CAD and more left ventricular (LV) dysfunction than did patients who had an increase in blood pressure with exertion; these findings probably account for the impaired survival. However, exertional hypotension, was an insensitive indicator of significant left main coronary artery stenosis, 3-vessel disease, or severe resting LV dysfunction.

Ventricular cryosurgery: short-term effects on intramural electrophysiology

The acute effects of cryothermia on regional electrophysiology were examined in order to devise a means of localizing and monitoring the intramural progression of ventricular cryolesions during a two-minute period of cryothermia application. Intramural unipolar electrograms were recorded from multipoint plunge electrodes placed in the left ventricle in 15 dogs. Epicardial, intramural, and endocardial applications of cryothermia were then employed, and changes in the unipolar peak-to-peak amplitude (UPPA) of electrograms were recorded. The location and depth of the ultimate permanent cryolesion could be predicted by noting locations of those electrograms demonstrating a decrease in the UPPA to less than 30% of the control values. Such electrophysiological monitoring of the region of myocardium undergoing cryothermic ablation provides a means of limiting the ultimate cryolesion to the desired location and depth within the ventricular wall. This allows precise placement of cryolesions in specific areas of the left ventricle for the treatment of ventricular tachyarrhythmias by selectively ablating arrhythmogenic ventricular myocardium without inducing injury in surrounding nonarrhythmogenic myocardium.

Effect of coronary artery bypass grafting on subsequent hospitalization

The rates of hospitalization during follow-up for a matched pair cohort of medically and surgically treated patients from the Angiography Registry of Seattle Heart Watch were compared. Medically and surgically treated patients were matched according to extent of disease, left ventricular ejection fraction, age, and 3 other survival rate-related characteristics. There was a 26% reduction in cardiovascular hospitalizations in the surgically treated patients (19%/year) compared with the medically treated patients (26%/year). This was due to a significant reduction in hospitalization rate for myocardial infarction (surgically treated patients 1.1%/year, medically treated patients 2.6%/year), and for other cardiovascular reasons (surgically treated patients 12.5%/year, medically treated patients 15.7%/year). No significant (p = 0.146) reduction occurred in hospitalization rate for chest pain not due to myocardial infarction (surgically treated patients 5.6%/year, medically treated patients 7.7%/year). When the perioperative infarctions are included for the surgical cohort, the overall myocardial infarction rate is not significantly different (p = 0.173) between the 2 treatment groups (surgically treated patients 1.9%/year, medically treated patients 2.6%/year). Acute myocardial infarction was an uncommon reason for hospitalization, accounting for only 8% (55 of 685) of all cardiovascular hospitalizations, and was not related to the number of stenotic vessels in medically treated patients.

Prognosis of asymptomatic or mildly symptomatic patients with coronary artery disease

One hundred forty-seven asymptomatic or mildly symptomatic patients with coronary artery disease, who did not have significant left main coronary occlusion and had an ejection fraction greater than 20 percent, were followed up prospectively for 6 to 67 months (average 25). Significant obstruction of one coronary artery was present in 28 percent of patients, of two coronary arteries in 31 percent and of three coronary arteries in 41 percent. Ejection fraction was 55 percent or greater in 69 percent of patients. During the follow-up there were eight deaths (annual mortality rate 3 percent for the entire group, 1.5 percent for patients with single and double vessel disease but 6 percent for those with triple vessel disease). Better definition of high and low risk subgroups of patients with three vessel disease was accomplished with exercise testing. Despite a history of mild symptoms, 25 percent of the patients with triple vessel disease exhibited poor exercise capacity on exercise testing after administration of beta adrenoceptor blocking agents and nitrates was discontinued; of these, 40 percent either died (20 percent) or had progressive symptoms requiring operation (20 percent) (annual mortality rate 9 percent). Of the patients with good exercise capacity, only 22 percent either died (7 percent) or had progressive symptoms (15 percent) (annual mortality rate 4 percent). Thus, prognosis is excellent in patients with no or mild symptoms who have one or two vessel coronary disease. Patients with three vessel disease who have good exercise capacity documented by objective testing have an annual mortality rate of 4 percent. However, because patients with three vessel disease and poor exercise capacity have an extremely grave prognosis, it would appear reasonable to recommend coronary bypass surgery for this subgroup, even in the absence of supporting data derived from a definitive randomized study.

Coronary artery graft surgery

The last decade has seen significant technical advances in equipment for the procedure of, and the surgeon's operating skill in coronary artery by pass surgery. Such surgery is indicated when, despite medical treatment, angina is disabling; although evidence is increasing that patients whose pain is controlled should be considered for surgery. Late operations are more complex and expensive, and patients are exposed to a higher risk of sudden death in the intervening period. Delay may also allow the disease to progress to an inoperable state. Patients unlikely to benefit from medical treatment should be offered surgery as soon as their disease is identified by angiography. Intensive medical treatment, with its poorer control of symptoms, leads to an increasing dependence on the State of medicine, hospital facilities and sickness benefits. The reputedly expensive coronary artery bypass operation is cheaper both to the State and to the patient tha unoperated invalidism.

Clinical and angiographic predictors of operative mortality from the collaborative study in coronary artery surgery (CASS)

Fifteen institutions participating in the Collaborative Study in Coronary Artery Surgery (CASS) have performed isolated coronary artery bypass surgery upon 6630 patients (1061 women and 5569 men) for coronary artery disease. The overall operative mortality (OM) was 2.3% (range 0.3-6.4%). Mortality increased with age, from 0 in the group 20-29 years old to 7.9% in the group 70 years and older. OM was higher for women in each group, ranging from 2.8% for ages 30-39 years to 12.3% for age 70 years and older (0.8% and 5.8% for men). Clinical manifestations of congestive heart failure were associated with increased OM. Mortality was 1.4% in one-vessel, 2.1% in two-vessel and 2.8% in three-vessel disease (diameter narrowing greater than or equal to 70%). Among 1019 patients with left main coronary artery (LMCA) stenosis, OM ranged from 1.6% in patients with mild stenosis and a right-dominant system to 25% in patients with severe (greater than or equal to 90%) stenosis and left dominance. OM varied with ejection fraction (EF) (1.9% for EF greater than or equal to 50% to 6.7% for EF less than 19%) and left ventricular wall motion score (1.7% for least abnormal to 9.1% for most abnormal). For elective surgery, OM was 1.7%, for urgent surgery 3.5%, and for emergency surgery 10.8%. Mortality was 40.0% among 30 patients with severe LMCA stenosis who underwent emergency revascularization. Advanced age, female sex, symptoms of heart failure, LMCA stenosis, impaired left ventricular function and nonelective surgery are associated with a higher OM. These factors should be considered in the selection of patients for coronary artery surgery.

Comparisons of the effects on survival after coronary artery surgery in subgroups of patients from the Seattle Heart Watch

We compared the survival of medically and surgically treated coronary artery disease patients in subgroups of patients to determine those most or least likely to benefit from surgery after an average of 5.5 years of follow-up. Cox's regression model for survival analysis was used in conjunction with data from all patients to estimate and test for the significance of the effects of surgery on survival in subgroups of patients, defined by one or more of the following variables: number of stenotic vessels (greater than or equal to 70%), ejection fraction, age, heart murmur, diuretic therapy, ventricular arrhythmia on resting ECG, left main coronary artery stenosis greater than or equal to 50%, previous myocardial infarction, cardiomegaly, congestive heart failure, unstable angina, and functional class. The Cox model adjusts for differences between medical and surgical patients in variables shown to be predictive of survival. A statistically beneficial effect of surgery on survival was seen in patients with two- or three-vessel disease, ejection fraction greater than or equal to 30%, age greater than or equal to 48 years, no heart murmur, no diuretic therapy, no ventricular arrhythmia on resting ECG, left main coronary artery stenosis less than 50%, no cardiomegaly, and no congestive heart failure. The converse subgroups defined by these variables did not show a significant beneficial effect from surgery. However, patient subgroups defined by presence or absence of prior myocardial infarction or unstable angina and New York Heart Association functional class I-II vs III-IV all showed beneficial effects from surgery.