Allen J. Solomon

Acute Myocardial Infarction Complicated by Atrial Fibrillation in the Elderly Prevalence and Outcomes

BACKGROUND Although atrial fibrillation (AF) is a common complication of acute myocardial infarction (MI), patient characteristics and association with outcomes remain poorly defined in the elderly. METHODS AND RESULTS We evaluated 106 780 Medicare beneficiaries > or =65 years of age from the Cooperative Cardiovascular Project treated for acute MI between January 1994 and February 1996 to determine the prevalence and prognostic significance of AF complicating acute MI in elderly patients. Patients were categorized on the basis of the presence of AF, and those with AF were further subdivided by time of AF (present on arrival versus developing during hospitalization). AF and non-AF patients were compared by univariate analysis, and logistic regression modeling was used to identify clinical predictors of AF. The influence of AF on outcomes was evaluated by unadjusted Kaplan-Meier survival curves and logistic regression models. AF was documented in 23 565 patients (22. 1%): 11 510 presented with AF and 12,055 developed AF during hospitalization. AF patients were older, had more advanced heart failure, and were more likely to have had a prior MI and undergone coronary revascularization. AF patients had poorer outcomes, including higher in-hospital (25.3% versus 16.0%), 30-day (29.3% versus 19.1%), and 1-year (48.3% versus 32.7%) mortality. AF remained an independent predictor of in-hospital (odds ratio [OR], 1. 21), 30-day (OR, 1.20), and 1-year (OR, 1.34) mortality after multivariate adjustment. Patients developing AF during hospitalization had a worse prognosis than patients who presented with AF. CONCLUSIONS AF is a common complication of acute MI in elderly patients and independently influences mortality, particularly when it develops during hospitalization.

Atrial pacing for the prevention of atrial fibrillation after cardiovascular surgery.

OBJECTIVE The purpose of this study was to determine the efficacy of atrial pacing in the prevention of atrial fibrillation following cardiovascular surgery. BACKGROUND Although pharmacologic therapy has been used to help prevent postoperative atrial fibrillation, it suffers from limited efficacy and adverse effects. In the nonoperative setting, novel pacing strategies have been shown to reduce recurrences of atrial fibrillation and prolong arrhythmia-free periods in patients with paroxysmal atrial arrhythmias. METHODS A total of 154 patients (115 men; mean age, 65 +/- 10 years; ejection fraction, 53 +/- 10%) undergoing cardiac surgery (coronary artery bypass surgery, 88.3%; aortic valve replacement, 4.5%; coronary bypass + aortic valve replacement, 7.1%) had right and left atrial epicardial pacing electrodes placed at the time of surgery. Patients were randomized to either no pacing, right atrial (RAP), left atrial (LAP) or biatrial pacing (BAP) for 72 h after surgery. Beta-adrenergic blocking agents were administered concurrently to all patients following surgery. RESULTS There was a reduction in the incidence of postoperative atrial fibrillation from 37.5% in patients receiving no postoperative pacing to 17% (p < 0.005) in patients assigned to one of the three pacing strategies. The length of hospital stay was reduced by 22% from 7.8 +/- 3.7 days to 6.1 +/- 2.3 days (p = 0.003) in patients assigned to postoperative atrial pacing. The incidence of atrial fibrillation was lower in each of the paced groups (RAP, 8%; LAP, 20%; BAP, 26%) compared with patients who did not receive postoperative pacing (37.5%). CONCLUSION Postoperative atrial pacing, in conjunction with beta-blockade, significantly reduced both the incidence of atrial fibrillation and the length of hospital stay following cardiovascular surgery. Additional studies are needed to determine the most effective anatomic pacing site.

Management of Chronic Stable Angina: Medical Therapy, Percutaneous Transluminal Coronary Angioplasty, and Coronary Artery Bypass Graft Surgery: Lessons from the Randomized Trials

Coronary artery disease results in more deaths, disability, and economic loss than any other disease in industrialized nations. In addressing coronary artery disease, the primary focus should be on prevention. This begins with the management of risk factors traditionally linked to coronary artery disease, including hypercholesterolemia, hypertension, cigarette smoking, and diabetes mellitus. Modification of other risk factors, such as elevated homocysteine levels, is the subject of current investigation. In addition, conditions known to precipitate angina, such as thyrotoxicosis, anemia, infection, and tachyarrhythmia, must be identified and treated. However, once symptomatic coronary artery disease has developed, specific treatment-pharmacologic therapy alone or in combination with coronary revascularization-is necessary. This report describes a rational approach to the use of pharmacologic therapy, percutaneous transluminal coronary angioplasty (PTCA), and coronary artery bypass surgery (CABG) in the treatment of coronary artery disease. Methods We reviewed relevant articles on the management of chronic stable angina published in English-language medical journals. We searched the MEDLINE database for articles published between 1976 and 1996 by using the keywords angioplasty, coronary artery bypass, and angina. To identify additional studies, we reviewed the abstracts presented at recent meetings of the American Heart Association and the American College of Cardiology. We also searched the reference lists of identified articles. We selected original research articles, meta-analyses, and abstracts that were related to the management of chronic stable angina and that emphasized comparisons of medical therapy, PTCA, and CABG. Randomized trials that compared PTCA with medical therapy (n = 3), compared CABG with medical therapy (n = 7), or compared PTCA with CABG (n = 9) were then grouped. Two meta-analyses compared PTCA with CABG, and one meta-analysis compared CABG with medical therapy; thus, a new meta-analysis was not done. These articles were used to develop our recommendations for the management of chronic stable angina. Data Synthesis Three large randomized trials done in the 1970s established a role for CABG in the treatment of multivessel coronary artery disease (Table 1). The Veterans Administration Cooperative Study (VACS), the European Coronary Surgery Study (ECSS), and the Coronary Artery Surgery Study (CASS) compared initial CABG with initial medical therapy [1-3]. Patients with the highest risk (as defined by severity of angina and ischemia, extent of coronary artery disease, and presence of left ventricular dysfunction) had the greatest benefit in terms of survival when they were randomly assigned to a surgical strategy [4]. Surgical revascularization thus became the treatment of choice for multivessel coronary artery disease, particularly in patients with left ventricular dysfunction. Table 1. Characteristics of Patients from Three Randomized Trials of Coronary Artery Bypass Graft Surgery Compared with Medical Therapy* Gruntzig introduced PTCA in 1979 as a catheter-based technique for the treatment of simple, concentric lesions involving a single coronary artery [5]. However, over the past two decades, the use of PTCA has been expanded to more complex lesions and to patients with multivessel coronary artery disease. This has resulted in an explosion in the number of PTCA procedures performed: A greater than 10-fold increase was seen during the past decade, and the number of procedures may have approached 500 000 in the United States in 1996 [6]. Despite this growth, however, data from randomized trials on the role of PTCA in the treatment of coronary artery disease were lacking until about 5 years ago. Percutaneous Transluminal Coronary Angioplasty Compared with Medical Therapy Only three randomized trials have compared PTCA with medical therapy, and all three studied patients with single-vessel coronary artery disease. A multicenter Veterans Affairs trial (ACME [Angioplasty Compared to Medicine]) compared the effects of PTCA on angina and exercise tolerance with those of medical therapy in 212 patients with stable single-vessel coronary artery disease [7]. After 6 months of follow-up, more of the patients who received PTCA were free of angina (64% compared with 46%; P < 0.01) (Figure 1). Patients in the PTCA group also had a greater improvement in exercise duration and psychological well-being than did medically treated patients [8]. However, patients who received PTCA had more cardiac procedures and spent more days in the hospital; this increased the initial costs of this strategy. Of note, the mortality rates and rates of myocardial infarction did not differ between the two groups. Figure 1. Percentage of patients who were free of angina after randomization in the ACME (Angioplasty Compared to Medicine) study. A second trial, published in abstract form, compared medical therapy with PTCA in 88 patients with asymptomatic single-vessel coronary artery disease [9]. After 2 years of follow-up, no difference was seen in exercise tolerance or the development of symptoms between the two groups. Death, myocardial infarction, and need for revascularization procedures did not differ between the groups. The Medicine, Angioplasty or Surgery Study (MASS) evaluated the roles of medical therapy, PTCA, and CABG done by using an internal mammary artery graft in 214 patients with stable angina, normal left ventricular function, and stenosis of the proximal left anterior descending coronary artery [10]. The primary end point of cardiac death, myocardial infarction, or refractory angina requiring revascularization was significantly decreased in patients undergoing surgical revascularization compared with those receiving PTCA or medical therapy. In addition, both revascularization strategies resulted in greater relief of symptoms and less inducible ischemia during treadmill testing than did medical therapy. However, no difference was seen in mortality rates, rates of myocardial infarction, or rates of functional class III or IV angina among the three treatment groups. The results of these three trials are consistent. Patients treated with PTCA had greater symptomatic benefit than medically treated patients, and no change in mortality rates or rates of myocardial infarction was seen. However, the limitations of these studies cloud the conclusions that can be drawn from them. Each involved a small number of patients and thus did not have the power to evaluate meaningful differences in mortality rates or rates of myocardial infarction. Furthermore, clinical practice has changed significantly since the completion of these trials. The role of aggressive lipid-lowering therapy in the primary and secondary prevention of cardiac events, respectively, has been shown in the West of Scotland Coronary Prevention Study and the Scandinavian Simvastatin Survival Study [11, 12]. In addition, there is a growing body of data on the safety and efficacy of intracoronary stents in the treatment of stable and unstable ischemic chest pain syndromes [13]. Despite these limitations, the results of these trials suggest that a strategy of initial pharmacologic therapy is a reasonable approach in patients with stable single-vessel coronary artery disease. Nearly half of medically treated patients become asymptomatic, and no excess in morbidity or mortality is seen. If medical therapy does not relieve angina or if it causes adverse effects, PTCA is usually the preferred alternative. However, a large randomized study comparing PTCA, CABG, and medical therapy in patients with single-vessel coronary artery disease is clearly warranted. This study should use intracoronary stents, internal mammary artery grafts, and modern medical therapy. In addition, minimally invasive CABG should be included if its initial promise is sustained. Coronary Artery Bypass Graft Surgery Compared with Medical Therapy Shortly after the introduction of CABG, three large, multicenter, randomized trials began enrolling patients to compare a strategy of initial CABG with a strategy of initial medical therapy [1-3]. In VACS, 686 male patients who had had stable angina for 6 months were randomly assigned to treatment [14]. In ECSS, 768 men with multivessel disease who had had angina for more than 3 months were randomly assigned to treatment [15]. Finally, CASS enrolled 780 patients with single- or multivessel coronary artery disease [16]. Few women or elderly patients were included in these trials (Table 1). Much has been made about the differences among these trials, but the consistencies among them deserve greater emphasis. Yusuf and colleagues [4] performed a meta-analysis of seven randomized trials that compared a strategy of initial surgical therapy with a strategy of initial medical therapy. This analysis involved 2649 patients, of whom 2233 (84%) were from VACS, ECSS, or CASS. Surgical revascularization resulted in substantially lower mortality rates at 5, 7, and 10 years compared with medical treatment (Figure 2). In addition, the greatest absolute benefit for CABG was seen in patients with the highest preoperative risk. Specifically, patients with the most severe symptoms, ischemia, extent of coronary artery disease, and left ventricular dysfunction had the greatest comparative benefit. In each trial, left main coronary artery disease and three-vessel coronary artery disease with moderately impaired left ventricular function were the clearest indications for CABG. However, patients with three-vessel coronary artery disease and normal left ventricular function and patients with significant stenosis in the proximal left anterior descending coronary artery also had benefit from surgical revascularization [4]. In addition, several nonrandomized registry studies emphasized the benefit of surgery over medical therapy in patients with multivessel disease and severe angina

The combination of propranolol and magnesium does not prevent postoperative atrial fibrillation

BACKGROUND Atrial fibrillation is a common complication of cardiovascular surgery. Beta-blockers have been shown to decrease the incidence of postoperative atrial fibrillation. However, the use of magnesium is more controversial. It was our hypothesis that adjunctive magnesium sulfate would improve the efficacy of beta-blockers alone in the prevention of postoperative atrial fibrillation. METHODS We prospectively randomized 167 coronary artery bypass patients (mean age 61+/-10 years, 115 men) to receive propranolol alone (20 mg four times daily) or propranolol and magnesium (18 g over 24 hours). Magnesium was begun intraoperatively, and propranolol was started on admission to the intensive care unit. RESULTS Using an intention-to-treat analysis, the incidence of postoperative atrial fibrillation was 19.5% in the propranolol-treated patients and 22.4% in propranolol + magnesium-treated patients (p = 0.65). Because combination therapy resulted in an excess of postoperative hypotension, which required withholding doses of propranolol, an on-treatment analysis was also performed. In this analysis, the incidence of atrial fibrillation was still not significantly different (18.5% in propranolol-treated patients and 10.0% in propranolol + magnesium-treated patients, p = 0.20). CONCLUSIONS Adjunctive magnesium sulfate, in combination with propranolol, does not decrease the incidence of postoperative atrial fibrillation.

Effect on coronary artery anatomy of radiofrequency catheter ablation of atrial insertion sites of accessory pathways.

OBJECTIVES The purpose of this study was to analyze the effects of radiofrequency catheter ablation of the atrial insertion site of accessory pathways on the angiographic appearance of coronary arteries. BACKGROUND Radiofrequency catheter ablation of accessory pathways requires the application of energy to the endocardial surface of the atrioventricular groove adjacent to the major epicardial coronary arteries. A systematic analysis of the effect of radiofrequency ablation on coronary arteries has not previously been demonstrated. METHODS Seventy consecutive patients with 76 accessory pathways (7 right free wall, 44 left free wall, 12 posteroseptal, 8 anteroseptal and 5 midseptal) were studied. Quantitative coronary angiography was performed before, immediately after and a mean of 69 +/- 42 days after radiofrequency catheter ablation. RESULTS Coronary artery diameter adjacent to the ablating electrode was 2.6 +/- 0.9 mm before ablation, 2.7 +/- 0.9 mm immediately after ablation and 2.7 +/- 1.0 mm at the time of follow-up study. Angiographic findings were unchanged from baseline in 69 of 70 patients immediately after ablation and in all 70 patients at the time of follow-up study. CONCLUSIONS Radiofrequency catheter ablation of the atrial insertion site of accessory pathways does not result in short-term angiographic changes in coronary artery anatomy.

Treatment of Postoperative Atrial Fibrillation: A Nonsurgical Perspective

Atrial fibrillation is a common complication of cardiovascular surgery. The 2 most important risk factors for its development are advancing age and a preoperative history of atrial fibrillation. Long-term sequelae, such as a stroke, are uncommon; however, atrial fibrillation frequently results in an increased length and cost of hospitalization. Strategies to prevent postoperative atrial fibrillation include perioperative beta-blockers, amiodarone, and atrial pacing. These strategies are most effective in high-risk patients. When atrial fibrillation does occur, treatment includes control of the ventricular rate, systemic anticoagulation, and conversion back to sinus rhythm.

Atrial fibrillation in patients after cardiovascular surgery: incidence, risk factors, preventive and therapeutic strategies.

Atrial fibrillation in patients undergoing cardiovascular surgery is a common problem, occurring in 25–50% of patients. Older patients and those with a prior history of atrial fibrillation are at highest risk, as are those patients in whom preoperative treatment with β-blockers has been discontinued. The immediate sequelae of this common complication include hemodynamic instability and congestive heart failure with long-term consequences including thromboembolic phenomena and increased cost and length of hospitalization. β-Blockers, amiodarone, and sotalol have all been shown to decrease the incidence of postoperative atrial fibrillation, but their use may be limited by their adverse effects. Other agents have some promise as prophylactic agents, but need further verification. Biatrial pacing has been shown to be effective, especially when β-blockers are used simultaneously. The goals for the treatment of atrial fibrillation include maintaining hemodynamic stability, controlling ventricular rate, preventing thromboembolic complications, and restoring sinus rhythm. The most effective strategy for the prevention of atrial fibrillation is to identify the highest-risk patients and target them for prophylaxis with β-blockers, amiodarone, sotalol or pacing.

Effect of recent randomized trials on current pacing practice.

The most common indication for a permanent pacemaker is symptomatic bradycardia. An atrial-based pacemaker (dual-chamber or atrial) usually is preferred, except in patients with chronic atrial fibrillation. Several prospective, randomized trials recently have been completed to evaluate new indications for permanent pacemakers. A dual-chamber pacemaker with an optimal atrioventricular interval can reduce the left ventricular outflow tract gradient by >50% in patients with hypertrophic cardiomyopathy. This has been associated with symptomatic improvement in the majority of patients, but an important placebo effect appears likely. Pacing also has been evaluated in patients with medically refractory dilated cardiomyopathy. Despite encouraging initial studies, routine implantation of a permanent pacemaker in dilated cardiomyopathy is not indicated. In patients with cardioinhibitory or mixed vasovagal syncope and carotid sinus hypersensitivity, implantation of a pacemaker markedly decreases syncopal episodes. Pacemaker therapy is clearly indicated in patients with atrial fibrillation associated with symptomatic bradycardia, and exciting new data on the use of pacing to prevent atrial fibrillation appear promising. The best pacing modality for this indication may be dual-site atrial pacing. Finally, permanent pacemakers play an important role in the treatment of symptomatic long QT syndrome, usually in combination with beta-blockers.

A SECOND DEFIBRILLATOR CHEST PATCH ELECTRODE WILL INCREASE IMPLANTATION RATES FOR NONTHORACOTOMY DEFIBRILLATORS

Nonthoracotomy defibrillator systems can be implanted with a lower morbidity and mortality, compared to epicardial systems. However, implantation may be unsuccessful in up to 15% of patients, using a monophasic waveform. It was the purpose of this study to prospectively examine the efficacy of a second chest patch electrode in a nonthoracotomy defibrillator system. Fourteen patients (mean age 62 ± 11 years, ejection fraction = 0.29 ± 0.12) with elevated defibrillation thresholds, defined as ≥ 24 J, were studied. The initial lead system consisted of a right ventricular electrode (cathode), a left innominate vein, and subscapular chest patch electrode (anodes). If the initial defibrillation threshold was ≥ 24 J, a second chest patch electrode was added. This was placed subcutaneously in the anterior chest (8 cases), or submuscularly in the subscapular space (6 cases). This resulted in a decrease in the system impedance at the defibrillation threshold, from 72.3 ± 13.3 Ω to 52.2 ± 8.6 Ω. Additionally, the defibrillation threshold decreased from ≥ 24 J, with a single patch, to 16.6 ± 2.8 J with two patches. These changes were associated with successful implantation of a nonthoracotomy defibrillator system in all cases. In conclusion, the addition of a second chest patch electrode (using a subscapular approach) will result in lower defibrillation thresholds in patients with high defibrillation thresholds, and will subsequently increase implantation rates for nonthoracotomy defibrillators.

A Simple In Vivo Model to Evaluate the Effects of Antiarrhythmic Agents

Antiarrhythmic agents alter cardiac conduction, refractoriness, and action potential duration in a rate dependent fashion. A simple in vivo model was developed to measure these variables over a wide range of cycle lengths. Complete heart block was produced in dogs using an 8 French hexapolar ablation catheter, anterior skin electrode, and radiofrequency current (30 W, 13,6 ± 2.6 seconds). Ventricular pacing and monophasic action potential recordings were performed using a single combination catheter. QRS and action potential durations were measured at multiple cycle lengths and after an abrupt change in paced cycle length. Ventricular effective refractory periods were also measured at multiple cycle lengths. Data obtained during flecainide and d‐Sotalol infusions are presented. This simple model allows detailed in vivo evaluation of the electrophysiological effects of antiarrhythmic agents and combinations.