Search

Objectives: We sought to determine whether the prehospital electrocardiogram (ECG) improves the diagnosis of an acute coronary syndrome., Background: The ECG is the most widely used screening test for evaluating patients with chest pain., Methods: Prehospital and in-hospital ECGs were obtained in 3,027 consecutive patients with symptoms of suspected acute myocardial infarction, 362 of whom were randomized to prehospital versus hospital thrombolysis and 2,665 of whom did not participate in the randomized trial. Prehospital and hospital records were abstracted for clinical characteristics and diagnostic outcome., Results: ST segment and T and Q wave abnormalities suggestive of myocardial ischemia or infarction were more common on both the prehospital and hospital ECGs of patients with as compared with those without acute coronary syndromes (p < or = 0.00001). Those with prehospital thrombolysis were more likely to show resolution of ST segment elevation by the time of hospital admission (14% vs. 5% in patients treated in the hospital, p = 0.004). In patients not considered for prehospital thrombolysis, both persistent and transient ST segment and T or Q wave abnormalities discriminated those with from those without acute coronary ischemia or infarction. Compared with ST segment elevation on a single ECG, added consideration of dynamic changes in ST segment elevation between serial ECGs improved the sensitivity for an acute coronary syndrome from 34% to 46% and reduced specificity from 96% to 93% (both p < 0.00004). Overall, compared with abnormalities observed on a single ECG, consideration of serial evolution in ST segment, T or Q wave or left bundle branch block (LBBB) abnormalities between the prehospital and initial hospital ECG improved the diagnostic sensitivity for an acute coronary syndrome from 80% to 87%, with a fall in specificity from 60% to 50% (both p < 0.000006)., Conclusions: ECG abnormalities are an early manifestation of acute coronary syndromes and can be identified by the prehospital ECG. Compared with a single ECG, the additional effect of evolving ST segment, T or Q waves or LBBB between serially obtained prehospital and hospital ECGs enhanced the diagnosis of acute coronary syndromes, but with a fall in specificity.

Objectives: The purpose of this study was to determine the relation between clinical variables and the defibrillation threshold by using a standardized testing protocol and a uniform implantable defibrillator system., Background: Past studied have not revealed useful correlations between clinical variables and the energy required to terminate ventricular fibrillation. Most of these studies did not use a uniform implantable defibrillator system or a standardized protocol to measure the defibrillation threshold and, thus, did not control for the influence of these technical influences. We postulated that defibrillator and defibrillation threshold measurement-based sources of variability overshadowed important clinical predictors., Methods: The defibrillation threshold was measured by using a standardized protocol in 101 consecutive patients. We used a transvenous unipolar pectoral defibrillation system that employed a single endocardial right ventricular defibrillation coil as the anode and the shell of an 80-cm3 pulse generator as the cathode to deliver a 65% tilt biphasic pulse., Results: Several clinical variables were found to be significantly associated with the defibrillation threshold: patient gender, height, weight, body surface area, heart rate at rest, QRS and corrected QT (QTc) intervals, left ventricular mass and several measures of heart and chest size by chest roentgenogram. None of these variables had a correlation coefficient > 0.45 with the defibrillation threshold. On multivariate analysis, left ventricular mass and heart rate at rest were the only independent predictors of the defibrillation threshold and explained only 25% of the observed variability., Conclusions: Despite the use of a uniform transvenous defibrillation system and a standardized protocol to measure the defibrillation threshold, no clinically relevant correlation was found between clinical variables and the defibrillation threshold. The defibrillation threshold is probably a function of a complex interaction of anatomic, physiologic and cellular variables that are not adequately represented by easily obtainable clinical information. It is probably not possible to predict defibrillation outcome from standard clinical variables.

Objectives: The aim of this study was to determine the efficacy of implantable cardioverter-defibrillator (ICD) therapy in survivors of sudden cardiac death in whom no ventricular arrhythmias can be induced with programmed electrical stimulation., Background: Survivors of sudden cardiac death in whom ventricular arrhythmias cannot be induced with programmed electrical stimulation remain at risk for recurrence of serious arrhythmias. Optimal protection to prevent sudden death in these patients is uncertain. This study compares survival in the subset of survivors of sudden cardiac death with that of patients treated with or without an ICD., Methods: A retrospective study was performed on 194 consecutive survivors of primary sudden death who had < or = 6 beats of ventricular tachycardia induced with programmed electrical stimulation with at least three extrastimuli. Ninety-nine patients received an ICD and 95 did not., Results: There were no significant differences between the two groups in presenting rhythm, number of prior myocardial infarctions or use of antiarrhythmic agents. Patients treated with an ICD were younger (55 +/- 16 vs. 59 +/- 11 years, p = 0.03) and had a lesser incidence of coronary artery disease (48% vs. 63%, p = 0.04) and a lower ejection fraction (0.43 +/- 0.16 vs. 0.48 +/- 0.18, p = 0.04). There were no significant differences between the groups in the use of revascularization procedures or antiarrhythmic agents after the sudden cardiac death. Patients treated with an ICD had an improvement in sudden cardiac death-free survival (p = 0.04) but the overall survival rate did not differ from that of the patients not so treated (p = 0.91). A multivariate regression analysis that adjusted for the observed differences between the groups did not alter these results., Conclusions: Survivors of sudden cardiac death in whom no arrhythmias could be induced with programmed electrical stimulation remained at risk for arrhythmia recurrence. Although the proportion of deaths attributed to arrhythmias was lower in the patients treated with an ICD, this therapy did not significantly improve overall survival.

The findings in 3,256 consecutive patients hospitalized for acute myocardial infarction were tabulated to assess the history, treatments and outcome in the elderly; 1,848 patients (56%) were greater than 65 years of age, including 28% who were aged greater than or equal to 75 years. The incidence of prior angina, hypertension and heart failure (only 3% of patients less than 55 years of age had a history of heart failure compared with 24% greater than or equal to 75 years old) was found to increase with age. Twenty-nine percent of patients less than 75 years of age were treated with a systemic thrombolytic drug compared with only 5% of patients older than 75 years. Mortality rates increased strikingly with advanced age (less than 2% in patients less than or equal to 55, 4.6% in those 55 to 64, 12.3% in those 65 to 74 and 17.8% in those greater than or equal to 75 years). Both the incidence of complicating illness and a nondiagnostic electrocardiogram (ECG) increased with age. In a multivariate analysis of outcome in older patients (greater than or equal to 65 years), adverse events were related to both prior history of heart failure (odds ratio 3.9) and increasing age (odds ratio 1.4 per each decade of age). Outcome was not improved by treatment with thrombolytic drugs, but these agents were prescribed to only 12% of patients greater than 65 years of age, thereby reducing the power for detecting such an effect.(ABSTRACT TRUNCATED AT 250 WORDS)

A prehospital computer-interpreted electrocardiogram (ECG) was obtained in 1,189 patients with chest pain of suspected cardiac origin during an ongoing trial of prehospital thrombolytic therapy in acute myocardial infarction. Electrocardiograms were performed by paramedics 1.5 +/- 1.2 h after the onset of symptoms. Of 391 patients with evidence of acute myocardial infarction, 202 (52%) were identified as having ST segment elevation (acute injury) by the computer-interpreted ECG compared with 259 (66%) by an electrocardiographer (p less than 0.001). Of 798 patients with chest pain but no infarction, 785 (98%) were appropriately excluded by computer compared with 757 (95%) by an electrocardiographer (p less than 0.001). The positive predictive value of the computer- and physician-interpreted ECG was, respectively, 94% and 86% and the negative predictive value was 81% and 85%. Prehospital screening of possible candidates for thrombolytic therapy with the aid of a computerized ECG is feasible, highly specific and with further enhancement can speed the care of all patients with acute myocardial infarction.

The long-term outcome of 241 survivors of out of hospital ventricular fibrillation who underwent programmed electrical stimulation was evaluated. Patients were categorized according to the rhythm induced at baseline drug-free electrophysiologic testing. Ventricular fibrillation was induced in 39 patients (16%) (Group 1), sustained ventricular tachycardia in 66 patients (27%) (Group 2) and nonsustained ventricular tachycardia in 34 patients (14%) (Group 3); 102 patients (42%) (Group 4) did not have an arrhythmia inducible at baseline electrophysiologic testing. Antiarrhythmic drugs were administered over the long term to 92% of patients in Group 2, 91% of patients in Group 1 and 47% of patients in Group 4. At a mean follow-up time of 30 +/- 15 months, recurrent sudden cardiac death or nonfatal ventricular fibrillation occurred in 11 (28%) of 39 patients with inducible ventricular fibrillation (Group 1), 14 (21%) of 66 patients with inducible sustained ventricular tachycardia (Group 2), 4 (12%) of 34 patients with inducible nonsustained ventricular tachycardia (Group 3) and 16 (16%) of 102 patients without inducible arrhythmias (Group 4). Actuarial analysis revealed a 2 year cumulative arrhythmia-free survival rate of 65% for patients in Group 2, 71% for patients in Group 1, 79% for patients in Group 3 and 81% for patients in Group 4 (p = 0.02). Actuarial survival of patients with inducible sustained ventricular tachycardia or ventricular fibrillation suppressed by electrophysiologically guided drug therapy was not significantly different from that in patients whose arrhythmia was not suppressed. Multivariate regression analysis revealed that only the presence of congestive heart failure was an independent predictor of outcome in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Prehospital initiation of thrombolytic therapy by paramedics, if both feasible and safe, could considerably reduce the time to treatment and possibly decrease the extent of myocardial necrosis in patients with acute coronary thrombosis. Preliminary to a trial of such a treatment strategy, paramedics evaluated the characteristics of 2,472 patients with chest pain of presumed cardiac origin; 677 (27%) had suitable clinical findings consistent with possible acute myocardial infarction and no apparent risk of complication for potential thrombolytic drug treatment. Electrocardiograms (ECGs) of 522 of the 677 patients were transmitted by cellular telephone to a base station physician; 107 (21%) of the tracings showed evidence of ST segment elevation. Of the total 2,472 patients, 453 developed evidence of acute myocardial infarction in the hospital; 163 (36%) of the 453 had met the strict prehospital screening history and examination criteria and 105 (23.9%) showed ST elevation on the ECG and, thus, would have been suitable candidates for prehospital thrombolytic treatment if it had been available. The average time from the onset of chest pain to prehospital diagnosis was 72 +/- 52 min (median 52); this was 73 +/- 44 min (median 62) earlier than the time when thrombolytic treatment was later started in the hospital. Paramedic selection of appropriate patients for potential prehospital initiation of thrombolytic treatment is feasible with use of a directed checklist and cellular-transmitted ECG and saves time. This strategy may reduce the extent and complications of infarction compared with results that can be achieved in a hospital setting.

Amiodarone was used to treat cardiac arrhythmias that had been refractory to conventional medical therapy. The first 70 consecutive patients treated with amiodarone in this study had at least 6 months of follow-up (range 6 to 24, mean 11) and form the basis for this report. Sixty-six patients were treated for ventricular arrhythmias and four for supraventricular tachycardias. Amiodarone therapy consisted of a loading dose of 600 mg orally twice a day for 7 days, and 600 mg daily thereafter. Doses were reduced only if side effects occurred. Because of frequent side effects, the dose was reduced from 572 +/- 283 mg per day (mean +/- standard deviation) at 45 days to 372 +/- 174 mg per day at 6 months. With a mean follow-up of 11 months in the 54 patients who continued to take amiodarone, only 4 patients had ventricular fibrillation. Three additional patients experienced recurrent sustained ventricular tachycardia in long-term follow-up. All 70 patients had extensive clinical and laboratory evaluation in follow-up. Side effects were common, occurring in 93% of patients. Thirteen patients (19%) had to discontinue the medication because of severe side effects. Fifty-six patients had gastrointestinal side effects, most commonly constipation. All patients but 1 eventually developed corneal microdeposits, and 43 patients were symptomatic. Cardiovascular side effects were uncommon. Symptomatic pulmonary side effects occurred in seven patients, with unequivocal pulmonary toxicity occurring in five. Neurologic side effects, most commonly tremor and ataxia, occurred in 52 patients. Thyroid dysfunction occurred in 3 patients, and 32 patients had cutaneous abnormalities. Miscellaneous other side effects occurred in 32 patients. Amiodarone appears to be useful in the management of refractory arrhythmias. Because virtually all patients develop side effects when given a maintenance daily dose of 600 mg, lower maintenance doses should be used. It is unknown if the more severe side effects are dose-related. Amiodarone is difficult to administer because of its narrow toxic-therapeutic range and prolonged loading phase. More importantly, the first sign of antiarrhythmic failure may be manifest as sudden cardiac death.

In order to characterize the day to day reproducibility of arrhythmias provoked during electrophysiologic stimulation, 114 patients with documented sustained clinical ventricular tachyarrhythmias were studied. Two baseline electrophysiologic tests were performed in the drug-free state and within 6 to 24 hours of one another. There was a significant increment (p less than or equal to 0.02) in the induction of sustained ventricular tachyarrhythmias as the number of programmed extrastimuli increased from one (10% induction) to four (64% induction). Provoked arrhythmias were observed to be more frequently nonreproducible (as reflected in a major change in rate or duration, or both, of an induced ventricular arrhythmia between baseline tests) as the number of extrastimuli increased from one (7%) to four (27%). Nonreproducibility with three and four extrastimuli was not significantly greater than when two extrastimuli were utilized. Electrophysiology-directed drug trials should be interpreted in light of this observed variability in induced arrhythmias.