Chest pain emergency units.

Each year in the United States, more than 2 million patients are hospitalized with chest pain suggestive of myocardial ischemia, with fewer than 20% of these patients having an acute coronary event. Chest pain emergency units have been created to facilitate urgent therapy for patients with a serious cardiovascular event and to triage lower risk patients to less intensive, more cost-effective inpatient care or discharge to home. The clinical history, physical examination, and initial electrocardiogram are key to initial stratification of patients for further management, but additional methods are necessary to clearly distinguish patients with inconclusive findings at presentation as high- and low-risk. Innovative electrocardiographic methods have increased sensitivity for detecting myocardial ischemia. Accelerated diagnostic protocols with new cardiac serum markers can detect myocardial ischemia or infarction with increasing accuracy. Early echocardiographic, scintigraphic, and treadmill stress protocols can further evaluate patients who have nondiagnostic electrocardiograms and negative serum markers. This review presents the current status of chest pain emergency units and the evolving management strategies they encompass.

Evaluation of low-risk patients with chest pain in the emergency department: value and limitations of recent methods.

More than 2 million patients are hospitalized annually in this country because of chest pain suggestive of myocardial ischemia. However, a coronary event is demonstrated in <20% of this population. It has been further shown that among patients presenting with acute chest pain, a very low-risk group, with <5% probability of a coronary event, can be identified by the initial clinical assessment. Recognition of this group could prevent many unnecessary hospital admissions, affording more appropriate patient care and improved cost-effectiveness. To enhance identification and management of low-risk patients with chest pain, several diagnostic approaches are currently being investigated to determine their value in the early detection of myocardial ischemia to select those requiring admission. In addition to the initial history, these strategies include physical examination and electrocardiogram, new serum markers, early noninvasive cardiac imaging by echocardiography or myocardial scintigraphy, new electrocardiographic methods, and early exercise testing. Most of these methods have shown promise for stratifying patients presenting with chest pain into high-risk and low-risk groups, thereby extending the initial clinical assessment in the critical decision of patient admission or discharge from the emergency department with early follow-up. This review presents the current status of these techniques with emphasis on our experience with immediate treadmill testing of selected patients in the emergency department. These methods are still in the developmental phase and their long-term utility will be determined by their safety, accuracy, cost, and specific institutional expertise.

Immediate exercise testing of low risk patients with known coronary artery disease presenting to the emergency department with chest pain.

OBJECTIVES: The purpose of this study was to demonstrate the safety and utility of immediate exercise treadmill testing (IETT) of low risk patients presenting to the emergency department with known coronary artery disease (CAD). BACKGROUND: More than 70% of the two million patients admitted to U.S. hospitals annually for suspected acute myocardial infarction (AMI) are found not to have had a cardiac event. We have previously demonstrated the safety and efficacy of IETT of selected low risk patients without known CAD presenting to the emergency department with chest pain. This study extends this approach to selected patients with a history of CAD. METHODS: One hundred patients evaluated by the chest pain emergency room to rule out AMI underwent IETT using a modified Bruce protocol upon admission to the hospital (median time <1 h). RESULTS: Twenty-three patients (23%) had positive exercise electrocardiograms (ExECGs); an uncomplicated non-Q wave AMI was diagnosed in two patients. Thirty-eight patients (38%) had negative ExECGs and 39 patients (39%) had nondiagnostic ExECGs. Of these 100 patients, 64 were discharged immediately after IETT, 19 were discharged in less than 24 h after negative serial cardiac enzymes and stable electrocardiograms and 17 were discharged after further evaluation and treatment. There were no complications from exercise testing and no late deaths or AMI during six-month follow-up. CONCLUSIONS: Immediate exercise treadmill testing of low risk patients with chest pain and known CAD is effective in further stratifying this group into patients who can be safely discharged and those who require hospital admission.

Evaluation of chest pain in low-risk patients presenting to the emergency department: the role of immediate exercise testing.

STUDY OBJECTIVES: To determine the safety and utility of immediate exercise testing in the evaluation of low-risk patients presenting to the emergency department with chest pain and its applicability to a heterogeneous population of men and women. METHODS: We conducted a prospective study of the safety and utility of immediate exercise testing in low-risk patients, as indicated by clinical and ECG criteria. The study group was large, heterogeneous, and included patients with a history of coronary artery disease. The patients were treated at a large, university medical center. Exercise testing (immediate exercise treadmill testing) was performed by internists, and cardiac serum enzyme levels were not measured before the exercise test. RESULTS: A total of 212 patients (121 men, 91 women) underwent exercise testing with no adverse effects. Twenty-eight (13%) patients had positive results on exercise ECGs. Twenty-three of the latter had further evaluation that revealed evidence of coronary artery disease in 13 (57%). Fifty-nine percent (125/212) of patients had negative exercise test results and 28% (59/212) had nondiagnostic tests. All patients with negative test results and 93% with nondiagnostic test results were discharged directly from the ED. Thirty-day follow-up was achieved in 201 (95%) patients and revealed no mortality in any of the patients in the three groups. One patient with a positive exercise test result returned to the ED within 30 days with mild congestive heart failure. CONCLUSION: Our results in this patient population support the safety and utility of immediate exercise testing of low-risk patients who present to the ED.

Conversion efficacy and safety of intravenous ibutilide compared with intravenous procainamide in patients with atrial flutter or fibrillation.

OBJECTIVES: This multicenter study compared the efficacy and safety of ibutilide versus procainamide for conversion of recent-onset atrial flutter or fibrillation. BACKGROUND: Ibutilide fumarate is an intravenous (IV) class III antiarrhythmic agent that has been shown to be significantly more effective than placebo in the pharmacologic conversion of atrial flutter and fibrillation to sinus rhythm. Procainamide is commonly used for conversion of recent-onset atrial fibrillation to normal sinus rhythm. METHODS: One hundred twenty-seven patients (age range 22 to 92 years) with atrial flutter or fibrillation of 3 h to 90 days' (mean 21 days) duration were randomized to receive either two 10-min IV infusions of 1 mg of ibutilide fumarate, separated by a 10-min infusion of 5% dextrose in sterile water, or three successive 10-min IV infusions of 400 mg of procainamide hydrochloride. RESULTS: Of the 127 patients, 120 were evaluated for efficacy: 35 (58.3%) of 60 in the ibutilide group compared with 11 (18.3%) of 60 in the procainamide group had successful termination within 1.5 h of treatment (p < 0.0001). Seven patients were found to have violated the protocol and were not included in the final evaluation. In the patients with atrial flutter, ibutilide had a significantly higher success rate than procainamide (76% [13 of 17] vs. 14% [3 of 22], p=0.001). Similarly, in the atrial fibrillation group, ibutilide had a significantly higher success rate than procainamide (51% [22 of 43] vs. 21% [8 of 38], p=0.005). One patient who received ibutilide, which was found to be a protocol violation, had sustained polymorphic ventricular tachycardia requiring direct current cardioversion. Seven patients who received procainamide became hypotensive. CONCLUSIONS: This study establishes the superior efficacy of ibutilide over procainamide when administered to patients to convert either atrial fibrillation or atrial flutter to sinus rhythm. Hypotension was the major adverse effect seen with procainamide. A low incidence of serious proarrhythmia was seen with the administration of ibutilide occurring at the end of infusion.

Platelet activation during dobutamine stress echocardiography.

BACKGROUND: Dobutamine stress echocardiography (DSE) is a common, useful test for the evaluation of coronary artery disease. Two of 650 patients who underwent DSE at our institution sustained nonfatal myocardial infarction either during DSE or shortly thereafter. Although DSE is associated with low morbidity rates, this rate is higher than our experience with exercise treadmill testing (ETT). METHODS: Six individuals who did not undergo DSE or ETT were enrolled to evaluate direct in vitro effects of dobutamine on platelets. Nine patients undergoing DSE and seven patients undergoing ETT were enrolled to evaluate in vivo platelet activation. We used flow cytometry and fluorescent-labeled monoclonal antibodies to activation-dependent platelet antigens to detect dobutamine-associated platelet activation both in vitro and in vivo. RESULTS: In vitro we found a synergistic increase in epinephrine-induced CD62 expression in the presence of dobutamine. The response to the combination of dobutamine and epinephrine was 151% to 565% of the expected response. In vivo there was a dose- and time-dependent rise in the percentage of platelets expressing CD62 in all nine subjects undergoing DSE. The median percentage of platelets expressing CD62 was 1.6% (range 0.1% to 6.8%), 6.5% (range 0.2% to 11.7%), 11.6% (range 5.9% to 19.1%), and 11.4% (range 7.2% to 25.0%) in the samples obtained at baseline, 20 microg/kg/min of dobutamine, 40 microg/kg/min of dobutamine, and during the recovery phase, respectively (repeated measures analysis of variance, p = 0.02). There was no increase in CD62 expression on platelets obtained from seven patients at peak ETT. The median percentage of CD62 at baseline ETT was 1.9% (range 0.2% to 7.3%) and at peak was 2.6% (range 0.4% to 7.0%) (p = 0.156, Wilcoxon signed rank test). CONCLUSION: We conclude that platelet activation occurs in vivo in patients undergoing DSE and that this may be caused by a synergistic effect of dobutamine with physiologic platelet agonists.

Management of cardiac complications in neuromuscular disease.

Cardiovascular complications are common and varied in neuromuscular diseases. Knowledge of the complications specific to each disease is essential for appropriate screening for cardiovascular disease. Appropriate treatment of complications varies between neuromuscular diseases and draws primarily on experience from patients without neuromuscular disease. This article details the known cardiovascular complications and treatments for some of the major neuromuscular diseases.

Systolic blood pressure at rest, not the degree of beta blockade, predicts the result of follow-up tilt-table testing for vasovagal syncope.

Tilt-table testing after therapy with beta blockade is frequently used to predict clinical success. This study found that heart rate and blood pressure reductions after beta-blocker therapy did not predict the results of the follow-up tilt-table test, but low blood pressure at rest before the initial test predicts failure of this therapy.

Acute myocardial infarction associated with dobutamine stress echocardiography.

Acute myocardial infarction as a complication of dobutamine stress echocardiography (DSE) is described in two patients during or shortly after undergoing the procedure. Both clinical events resulted in characteristic elevations in cardiac enzymes and the development of new electrocardiographic Q waves in the inferior leads. Subsequent coronary angiography was performed in both cases; one patient required two-vessel coronary artery bypass grafting to his first obtuse marginal and posterior descending arteries, and the other underwent successful angioplasty of an occluded proximal right coronary artery. Only two cases of DSE-associated myocardial infarction have been reported previously in the literature.

Evaluation of the patient with 'rule out myocardial infarction'.

Evaluation in the emergency department of the patient with chest pain remains a common problem. Large numbers of patients are admitted to the hospital because of diagnostic uncertainty. Strategies dealing with this population include risk stratification by clinical presentation, serial cardiac enzyme assays to exclude myocardial infarction, and detection of myocardial ischemia with nuclear scintigraphy or echocardiography. Each of these strategies is rational with specific benefits and weaknesses. Bypassing these steps and performing immediate exercise testing is the newest approach that appears to be safe, timely, and cost-effective.

Advantages of continuous noncardioplegic warm blood retrograde perfusion over antegrade perfusion during proximal coronary anastomoses.

Retrograde perfusion via the coronary sinus supplies vascular beds distal to coronary stenoses and has been used for administration of cardioplegia. An additional application is to supply noncardioplegic retrograde perfusion while performing proximal anastomoses (a time when cardiac arrest is not critical). The aim of this study was to determine the safety of this technique and to study the metabolic changes with antegrade versus retrograde warm blood perfusion. Sixty-six patients, with good left ventricular function, underwent distal coronary bypass in a similar fashion. Proximal anastomoses were done with 1) partial occlusion clamp (n = 29) or 2) cross-clamp on and continuous, warm, noncardioplegic retrograde blood perfusion (n = 37). In an additional 10 patients, metabolism was assessed with antegrade and retrograde perfusion during proximal anastomoses. Despite longer cross-clamp times (96.4 +/- 6.2 vs 80.8 +/- 3.1 min, p < 0.05) with retrograde perfusion, the total duration of cardiopulmonary bypass was significantly less (119.6 +/- 6.2 vs 136.6 +/- 4.6 min, p < 0.05). There was superior postbypass, intraoperative hemodynamics (cardiac index) with retrograde perfusion (4.0 +/- 0.2 vs 3.6 +/- 0.1 L/min/m2). The incidence of postoperative dysrhythmia was not significantly different between groups. Oxygen and glucose utilization was more efficient with retrograde perfusion. Retrograde perfusion during proximal anastomoses is a safe technique. There is diminished risk of aortic dissection, atheroembolism, delayed aneurysm formation, or rupture due to avoidance of application of partial occlusion clamps. There is evidence of superior substrate utilization.