Cardiac Death in the first 6 months after myocardial infarction: potential for mortality reduction in the early posthospital period

Evaluation of premature ventricular complexes during in-hospital ECG monitoring as a predictor of ventricular tachycardia in an intensive care unit cohort

In-hospital electrocardiographic (ECG) monitors are typically configured to alarm for premature ventricular complexes (PVCs) due to the potential association of PVCs with ventricular tachycardia (VT). However, no contemporary hospital-based studies have examined the association of PVCs with VT. Hence, the benefit of PVC monitoring in hospitalized patients is largely unknown. This secondary analysis used a large PVC alarm data set to determine whether PVCs identified during continuous ECG monitoring were associated with VT, in-hospital cardiac arrest (IHCA), and/or death in a cohort of adult intensive care unit patients. Six PVC types were examined (i.e., isolated, bigeminy, trigeminy, couplets, R-on-T, and run PVCs) and were compared between patients with and without VT, IHCA, and/or death. Of 445 patients, 48 (10.8%) had VT; 11 (2.5%) had IHCA; and 49 (11%) died. Isolated and run PVC counts were higher in the VT group (p = 0.03 both), but group differences were not seen for the other four PVC types. The regression models showed no significant associations between any of the six PVC types and VT or death, although confidence intervals were wide. Due to the small number of cases, we were unable to test for associations between PVCs and IHCA. Our findings suggest that we should question the clinical relevance of activating PVC alarms as a forewarning of VT, and more work should be done with larger sample sizes. A more precise characterization of clinically relevant PVCs that might be associated with VT is warranted.

Role of platelets in the development of atherosclerotic disease and possible interference with platelet inhibitor drugs

During the last two decades, significant advances have been made in the understanding of atherosclerotic disease. The pathogenesis of atherosclerosis appears to depend on a precise sequence of critical events based on the interaction of blood elements and lipids with the arterial wall. The major critical events and their sequence appears to be as follows: hemodynamic stress and endothelial injury; arterial wall-platelet interaction; smooth muscle cell proliferation; lipid entry and accumulation; significant arterial narrowing with fibrosis and development of thrombi; and complications in the form of calcification, ulceration, aneurysm, acute thrombotic occlusion and embolization. This sequence of critical events starts at a young age and in all geographic racial groups. Their evolution into advanced symptomatic lesions takes many years and varies in incidence and extent among different geographic and ethnic groups. It appears that in promoting and accelerating this process into the advanced stage of the disease, the presence at a young age of the so-called risk factors of atherosclerotic disease is most important. The recent advances in the understanding of the atherosclerotic process will be highlighted in this chapter with particular attention being focused on the role of platelets and thrombosis in the development of the disease and the possible role of platelet inhibitor drugs on the prevention of coronary atherosclerotic disease.

Assessment, significance and mechanism of ventricular electrical instability after myocardial infarction

The mechanism of reentrant tachycardia was established nearly a century ago, but the relationships between myocardial infarction and predisposition to sudden death were not unravelled until much later. In the latter half of the twentieth century many studies sought to ascertain what variables were predictive of death following myocardial infarction. Approximately one half of all deaths during the year following myocardial infarction are sudden and due to ventricular tachycardia (VT) or ventricular fibrillation (VF). We aimed to utilise non-invasive signal-averaging, along with programmed electrical stimulation of the heart, to determine whether one could predict spontaneous ventricular tachycardia and sudden death late after myocardial infarction. The sensitivity of ventricular electrical instablility (inducible ventricular tachycardia or fibrillation) as a predictor of instantaneous death or spontaneous VT was 86%, and the specificity was 83%. When other variables (delayed ventricular activation at signal-averaging, ejection fraction at gated heart pool scan, ventricular ectopic activity at ambulatory monitoring and exercise testing) were taken into account, inducible VT at electrophysiological study was the single best predictor of spontaneous VT and sudden cardiac death after myocardial infarction. The Westmead studies of Uther et al. in the decade or so from 1980 established programmed stimulation as the best predictor of sudden death after myocardial infarction. Subsequent studies by others have demonstrated a survival advantage of defibrillator implantation in patients with low ejection fraction (and inducible ventricular tachycardia) after myocardial infarction.

Assessment of heart rate turbulence in the acute phase of myocardial infarction for long-term prognosis

This study is designed to assess the value of heart rate turbulence (HRT) in the acute phase of MI for prediction of long-term mortality risk. The study included 128 consecutive acute MI patients with 24-hour Holter recordings to evaluate HRT (turbulence onset and slope), SDNN, mean RR interval, and ventricular premature beat frequency. LVEF was evaluated by two-dimensional echocardiography. Data from 117 patients (mean age 58 +/- 11 years) were available for further analysis. Twelve patients died during follow-up (mean 312 +/- 78 days). Although SDNN < 70 ms was the most powerful predictor of mortality among all presumed risk factors (hazard ratio 20 [95% CI 2.6-158]; P = 0.004) in univariate Cox regression analysis, in multivariate analysis LVEF < or = 0.40 and turbulence slope < or = 2.5 ms/RR interval were the only independent predictors of mortality (hazard ratio 6.9 [95% CI 1.8-26]; P = 0.006, hazard ratio 7.3 [95% CI 1.4-37]; P = 0.016, respectively). Addition of HRT parameters for LVEF increased remarkably the positive predictive value (60%) without any decrease in the negative predictive value (92%). Blunted HRT reaction within the first 24 hours of acute MI is an independent predictor of long-term mortality. Furthermore, its predictive power is comparable and also additive to that of LVEF.

Risk stratification post-myocardial infarction: is early coronary angiography the more effective strategy?

The primary management strategy for the post-myocardial infarction patient continues to be controversial despite published guidelines. In part, this is the consequence of study designs that are not directly applicable to individual patients, but also to the rapidly changing pharmacological and mechanical device armamentarium that rapidly renders clinical trial results obsolete within a few years. This review attempts to highlight those areas where there is consensus as well as to explicate those situations where common clinical practice appears to be in conflict with accepted guidelines.

Use of stress echocardiography for risk assessment of patients after myocardial infarction

The main predictors of outcome after infarction (exercise capacity, ejection fraction, and extent of jeopardized myocardium) can all be identified using stress echocardiography. This review addresses the place of stress echocardiography in postinfarct risk evaluation, relative to clinical evaluation, and other technologies. The test is accurate for identification of multivessel disease and for predicting outcomes, is versatile, and can be used early after infarction.

Does the induction of ventricular flutter or fibrillation at electrophysiologic testing after myocardial infarction have any prognostic significance?

This study examines the significance of inducing sustained ventricular fibrillation (VF) or ventricular flutter by programmed stimulation after infarction. Programmed ventricular stimulation was performed for prognostic reasons from the right ventricular apex at twice diastolic threshold using a protocol containing 4 extrastimuli. Of 502 patients tested 11 +/- 4 days after acute infarction, VF was induced in 164 (33%), ventricular flutter in 134 (27%), ventricular tachycardia (VT) in 44 (9%), and no arrhythmia in 160 (32%). All groups were similar in age, sex distribution, and sites of index infarction. Those with inducible VT had a higher incidence of multiple infarctions and a lower mean left ventricular ejection fraction at the time of testing. Without antiarrhythmic drug therapy, 8 patients (18%) with inducible VT experienced spontaneous VT or died instantaneously during the first year of follow-up. By contrast, only 1 (0.6%) patient with inducible VF, 1 (0.7%) with ventricular flutter, and 1 (0.6%) without any inducible arrhythmias experienced similar events in the same period (p < 0.001). By relating the cycle length of the induced monomorphic arrhythmia to later spontaneous electrical events, induced arrhythmias with cycle length as low as 230 ms still identified patients at high risk for spontaneous arrhythmias. Only the induction of sustained monomorphic VT with a cycle length > 230 ms indicates patients with ventricular electrical instability after infarction. The induction of VF or ventricular flutter is a negative test result with no adverse long-term prognostic significance.

Should all patients undergo cardiac catheterization after a myocardial infarction?

Between one half and two thirds of patients who survive an acute myocardial infarction (AMI) may be at low risk for future complications and hence can be managed with medical therapy. However, the remaining patients are prone to future complications, which by and large occur within the subsequent 3 months and include cardiac death, recurrent AMI, unstable angina, and congestive heart failure. Current available methods for risk stratification include a good clinical evaluation, rest and stress electrocardiograms (preferentially combined with radionuclide imaging), and possibly two-dimensional stress echocardiography. In patients unable to exercise, pharmacologic perfusion scintigraphy affords a powerful means to identify high-risk patients. Patients deemed to be at high risk should be referred for cardiac catheterization and myocardial revascularization. The practice of performing routine cardiac catheterization after an AMI has led to an over use of resources in the United States. Such a practice is not based on any scientific evidence of enhanced benefit. In fact, in other Western world countries where only selected patients are referred for cardiac catheterization, patient survival appears to be similar to that in the United States. In conclusion, most patients after AMI, whether treated with thrombolytic therapy or not, can be managed conservatively and risk stratified on the basis of noninvasive testing, after which patients deemed to be at high risk should undergo invasive evaluation.

Current usefulness of the signal-averaged electrocardiogram

Signal-averaged electrocardiography is a relatively simple, noninvasive technique by which valuable information can be gained to help in the management of patients with cardiovascular disease. The presence of late potentials on the SAECG is a good marker for the presence of an arrhythmogenic substrate that is believed to be the source of ventricular tachycardia in patients with coronary artery disease. The value of the detection of late potentials has been studied best after myocardial infarction, when the absence of late potentials makes the occurrence of an arrhythmic event very unlikely. The positive predictive value for an arrhythmic event to occur in the presence of late potentials is low, however, comparable to the predictive value of decreased left ventricular function, complex ventricular ectopy, or abnormal autonomic tone. This appears to have its explanation in the complex pathophysiology behind the occurrence of arrhythmic events. Improved accuracy for the SAECG is achieved when the result of the test is interpreted with consideration of the presence or absence of other predictive markers. A thorough understanding of the signal-averaged electrocardiogram makes optimal clinical use of the information gained from this easily acquired test possible.

How long should high-risk patients with acute anterior wall myocardial infarction be monitored?

In 143 patients with an acute anterior wall myocardial infarction, left ventricular ejection fraction was determined within 72 h of admission. Left ventricular ejection fraction was below 40% in 114 patients. In this group late ventricular tachycardia or ventricular fibrillation occurred in 30 patients (26%). A left ventricular ejection fraction below 40% identified all patients who developed any late ventricular tachycardia and a left ventricular ejection fraction below 30% identified all who developed late ventricular fibrillation. After discharge another 2 patients with late ventricular tachycardia were detected. Death between 48 h and 3 weeks only occurred in patients with a left ventricular ejection fraction below 30%. Thus in patients with an acute anterior wall myocardial infarction a left ventricular ejection fraction below 30% within the first 72 h after the acute event identifies a high risk for late ventricular tachycardia or ventricular fibrillation. The occurrence of late ventricular tachycardia showed a gradual increase during 3 weeks of monitoring and no cut-off point could be detected within this time-window.

Results of Electrophysiological Testing and Long-Term Follow-Up in Patients Sustaining Cardiac Arrest Only While Receiving Type IA Antiarrhythmic Agents

Therapeutic management of patients sustaining a cardiac arrest while receiving antiarrhythmic agents can be difficult since the role of the drug in possibly facilitating the arrhythmia is often difficult to define. To determine if the response to programmed stimulation could give insight into which patients may have experienced a drug-induced cardiac arrest, we studied 29 patients (61 +/- 9 years) with no prior history of sustained ventricular tachyarrhythmias (VT) who suffered a cardiac arrest only while receiving type Ia antiarrhythmic agents. Patients with documented myocardial infarction, acute ischemia, electrolyte abnormalities, or torsade de pointes were excluded from the study. Twenty-four patients had coronary artery disease with prior myocardial infarction (ejection fraction 28% +/- 9%) and five patients had idiopathic dilated cardiomyopathy (ejection fraction 31% +/- 6%). During baseline electrophysiological testing, 19 patients (66%) had inducible sustained ventricular arrhythmias: uniform VT, n = 14 (group I), polymorphic VT or ventricular fibrillation, n = 5 (group II). Ten patients (group III) had no inducible sustained ventricular arrhythmias. To determine if rechallenge with a type Ia agent could facilitate induction of a sustained ventricular arrhythmia in group III, eight patients underwent ten electrophysiological studies during therapy with either procainamide or quinidine. Only two patients developed sustained VT in response to programmed stimulation. Patients in groups I and II received therapy guided by electrophysiological testing, including antiarrhythmic agents alone (n = 8), subendocardial resection (n = 4), or an implantable cardioverter defibrillator (n = 7). Patients in group III received antiarrhythmic agents empirically (n = 3), or for treatment of atrial tachyarrhythmias (n = 2) or nonsustained VT (n = 1). In addition, four patients in group III received an implantable cardioverter defibrillator. During a mean follow-up of 28 +/- 27 months (range: 1 day-84 months) 13 patients died suddenly or received a defibrillator shock preceded by syncope or presyncope: group I: n = 5; group II: n = 2; group III: n = 6.

IN CONCLUSION

(1) most patients sustaining a cardiac arrest only in the presence of type Ia antiarrhythmic agents have inducible sustained VT in the absence of antiarrhythmic agents, and (2) the risk of recurrent VT persists in patients without inducible sustained arrhythmias in the drug-free state, regardless of whether they manifest inducible arrhythmias after rechallenge with a type Ia agent.

Comparison of one-, six- and 24-hour ambulatory electrocardiographic monitoring for ventricular arrhythmia as a predictor of mortality in survivors of acute myocardial infarction. CAMIAT Pilot Study Group. Canadian Amiodarone Myocardial Infarction Arrhythmia Trial

To compare 1-, 6- and 24-hour ambulatory electrocardiograms for prediction of mortality after acute myocardial infarction (AMI), all patients with AMI hospitalized in Hamilton, Ontario during 1 year were identified. There were 683 patients discharged alive after AMI. One-, 6- and 24-hour ambulatory electrocardiographic results were available in 565 patients, and follow-up mortality data at 1 year was available in 560. Mean age of the patients was 64 years; 160 (29%) had previous AMI and 105 (19%) had had congestive heart failure. One hundred and fifty-two patients (27%) were receiving beta blockers, and 31 (6%) were receiving antiarrhythmic drugs. Regression modeling of survival times up to 1 year showed that all 3 durations of recording were univariate predictors of mortality. Using greater than 10 ventricular premature complexes/hour as the criterion of a positive test, neither the 6- nor 24-hour data contained statistically significant residual explanatory power after the 1-hour data were accounted for by the model. The longer durations of recording increased sensitivity at a cost of decreased specificity. The positive and negative predictive values of the 3 durations of recording were virtually identical. The presence of ventricular tachycardia was not a significant predictor of mortality in this population. There appears to be no benefit to ambulatory electrocardiographic recordings greater than 1 hour when they are to be used for prediction of 1-year mortality after AMI.

Did prognosis after acute myocardial infarction change during the past 30 years? A meta-analysis

Much effort has been spent to improve survival after acute myocardial infarction. To investigate how effective this effort has been, a meta-analysis was performed of studies published between 1960 and 1987 concerning mortality after acute myocardial infarction. Thirty-six studies were analyzed. They were classified with respect to deaths in the hospital and at 1 month and the 5-year mortality rate starting at hospital discharge. Mortality was assessed from all studies by comparing studies from different institutions with use of identical inclusion criteria (externally controlled studies) and by analyzing studies reporting on changes in mortality in two or more comparable patient cohorts admitted to the same institution at different time periods (internally controlled studies). Reports on clinical trials (for example, thrombolytic therapy, beta-adrenergic blockade) in acute myocardial infarction were excluded. Average overall in-hospital mortality decreased from 29% during the 1960s to 21% during the 1970s and to 16% during the 1980s. The externally controlled studies also showed a declining trend: from 1960 to 1969, 32%, from 1970 to 1979, 19% and from 1980 to 1987, 15%. The 1-month overall mortality rate decreased from 31% during the 1960s to 25% during the 1970s and 18% during the 1980s externally controlled studies. Most internally controlled studies also showed significant improvement in in-hospital and 1-month survival. In contrast, 5-year mortality after hospital discharge did not significantly decrease (33% from 1960 to 1969 and 33% from 1970 to 1979). It is concluded that in the prethrombolytic era, short-term prognosis after acute myocardial infarction has improved since 1960.(ABSTRACT TRUNCATED AT 250 WORDS)

Routine programmed electrical stimulation in survivors of acute myocardial infarction for prediction of spontaneous ventricular tachyarrhythmias during follow-up: results, optimal stimulation protocol and cost-effective screening

Of 3,286 consecutive patients treated for acute myocardial infarction, electrophysiologic testing was performed in 1,209 survivors (37%) free of significant complications at the time of hospital discharge to determine their risk of spontaneous ventricular tachyarrhythmias during follow-up. Sustained monomorphic ventricular tachycardia was inducible by programmed electrical stimulation in 75 (6.2%). Antiarrhythmic therapy was not routinely prescribed regardless of the test results. During the 1st year of follow-up, 14 infarct survivors (19%) with inducible ventricular tachycardia experienced spontaneous ventricular tachycardia or fibrillation in the absence of new ischemia compared with 34 (2.9%) of those without inducible ventricular tachycardia (p less than 0.0005). During the extended follow-up period (median 28 months) of those with inducible ventricular tachycardia, 19 (25%) had a spontaneous electrical event; 37% of these first events were fatal. These results suggest that the most cost-effective strategy for predicting arrhythmia will be obtained by restricting electrophysiologic testing to infarct survivors whose left ventricular ejection fraction is less than 40% and using a stimulation protocol containing four extrastimuli. Electrophysiologic testing is the single best predictor of spontaneous ventricular tachyarrhythmias during follow-up in infarct survivors. The majority (94%) with a negative test benefit from the more reliable reassurance that all is well, whereas the 25% risk of electrical events in those with inducible ventricular tachycardia justifies a prospective trial of effective prophylactic antiarrhythmic interventions.

Risk stratification in survivors of acute myocardial infarction: routine cardiac catheterization and angiography is a reasonable approach in most patients

Noninvasive risk assessment in survivors of AMI can effectively subdivide patients into groups with differing risk profiles after hospital discharge, but some patients at risk for late death or recurrent AMI may be incorrectly identified; data from cardiac catheterization and angiography provide complementary and generally more powerful prognostic information. Many patients may derive particular benefit from early cardiac catheterization and angiography, including: (1) patients with AMI complicated by recurrent myocardial ischemia, congestive heart failure, and/or complex ventricular arrhythmias; (2) patients with abnormal or inconclusive results of noninvasive testing or those patients unable to perform an exercise test; (3) patients with abnormal left ventricular global systolic function and those with increased left ventricular end-systolic volume; (4) "young" patients (younger than 50 years of age?); (5) older patients (older than 65 to 70 years of age?); (6) patients with non-Q wave AMI; and (7) patients who are receiving thrombolytic therapy. Performance of early cardiac catheterization and angiography in virtually all survivors of AMI, with selective use of appropriate noninvasive tests, may provide a more efficacious means of risk assessment after AMI; if all tests are performed judiciously, the cost of such an approach need not be excessive. A combination of invasive and selected noninvasive tests probably provides optimal information. The risks to the routine performance of diagnostic cardiac catheterization and angiography in all survivors of AMI are: (1) adequate care and attention may not be paid to proper performance of the procedure(s) and to detailed and proper analyses of the data; (2) the need for additional noninvasive testing in selected patients may be ignored; and most importantly, (3) premature or unnecessary revascularization procedures may be performed subsequently. For optimal patient care, the clinician must obtain all necessary data, avoid unnecessary and repetitive tests, know the accuracy of individual tests at his or her own facility, interpret all data in proper context, and then counsel patients objectively about available management strategies. With this approach, all patients who might appropriately benefit from coronary artery revascularization will be correctly identified, and patients who are truly at very low risk (minimal residual coronary artery disease and preserved left ventricular function particularly if associated with a patent infarct-related artery) may be similarly identified and managed appropriately with elimination of unnecessary additional testing and pharmacologic therapy. Finally, whatever approach to risk stratification one chooses for an individual patient, the importance of and the need to correct and/or ameliorate risk factors for coronary artery disease must be recognized and undertaken.

The Cardiac Arrhythmia Suppression Trial: background, interim results and implications

The Cardiac Arrhythmia Suppression Trial (CAST) was designed to test the hypothesis that suppression of ventricular premature complexes (VPCs) in survivors of acute myocardial infarction would reduce arrhythmic death risk. Instead, a preliminary finding from the CAST was that the encainide and flecainide groups had a 3.6-fold increase in arrhythmic death compared with their placebo group. These unfortunate results were especially surprising in that the CAST population represented patients in whom the risk of arrhythmic death was only moderate and the risk of proarrhythmia was thought to be low. In contrast, the arrhythmic death rate of the CAST placebo group was unusually low, to the extent that it paralleled the arrhythmic death rate in previous clinical trials of patients surviving myocardial infarction with no ventricular arrhythmia. The excessive arrhythmic death rate in patients taking encainide and flecainide occurred over the duration of the CAST, implying a proarrhythmic effect that may be due to mechanisms that are unique in this population, and thus challenging traditional concepts of proarrhythmia. The existing knowledge regarding the proarrhythmic and negative inotropic effects of encainide and flecainide are reviewed. The previous pharmaceutical database experience with these 2 antiarrhythmic drugs exceeded 3,000 patients; however, there was no indication of this serious proarrhythmic effect. In contrast, the CAST population taking encainide and flecainide totaled only 725 patients who were followed for 10 months and had an extremely high proarrhythmic event rate. The reasons for this discrepancy are discussed. The results of the CAST emphasize the power of a randomized, placebo-controlled clinical trial to uncover previously unsuspected benefits or liabilities of traditional therapies.

Cost-effective management of patients following myocardial infarction: the impact of ischemia on alternative approaches

Following uncomplicated myocardial infarction patients are at varying risk for cardiovascular morbidity and mortality. In order to identify and treat high risk patients, various management approaches can be employed. We performed a decision analysis to examine the cost-effectiveness of seven alternative strategies under the assumption that prognosis is affected by both the location of anatomic obstruction and the degree of myocardial ischemia. Strategies included combinations of angiography and two theoretical diagnostic tests capable of detecting ischemia with different degrees of accuracy. The strategy associated with the lowest overall six month mortality initiated testing with the diagnostic test most sensitive for ischemia, slightly better than proceeding initially to angiography. Initial use of a test sensitive for ischemia was also considerably more cost-effective than proceeding directly to angiography. Future analyses evaluating the role of diagnostic tests in coronary artery disease should incorporate the dimension of ischemia.

Prognosis following sustained ventricular tachycardia occurring early after myocardial infarction

Eighty-seven patients with sustained ventricular tachycardia (VT) between 3 and 90 days after acute myocardial infarction (AMI) were evaluated to define factors associated with a high risk of arrhythmia recurrence or death. Most patients had poor left ventricular function (mean ejection fraction 29 +/- 12%), multivessel coronary artery disease (71%) and inducible sustained VT with programmed stimulation (87%). During a mean follow-up of 26 months, 36 patients (41%) died and 21 patients had arrhythmia recurrence (with 19 sudden deaths). Factors independently associated with mortality included: (1) treatment before 1981 (p less than 0.01); (2) anterior AMI (p less than 0.05); (3) short time from AMI to first episode of VT (p less than 0.06); and (4) multivessel coronary artery disease (p less than 0.07). Factors independently associated with arrhythmia recurrence were: (1) medical treatment (as opposed to surgical) (p less than 0.01); (2) greater than or equal to 3 episodes of spontaneous VT (p = 0.01); (3) multivessel coronary disease (p less than 0.05); and (4) anterior AMI (p less than 0.07). Medically and surgically treated patients did not differ significantly in overall survival (49 vs 61%, respectively), although short-term (6 month) surgical survival improved from 31% during the first half of the study to 96% in the latter half (p less than 0.01). For patients with sustained VT early after AMI the risk of death and arrhythmia recurrence can be assessed based on clinical and angiographic characteristics; in addition, surgical treatment is associated with a lower incidence of arrhythmia recurrence than medical treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic cardiac catheterization variables in survivors of acute myocardial infarction: a five year prospective study

The prognostic variables from predischarge coronary angiography and left ventriculography in survivors of acute myocardial infarction during the years 1974 to 1978 were evaluated in 143 patients (less than or equal to 66 years of age) with documented myocardial infarction who were then followed up prospectively for 5 years. One half of the study population had triple vessel coronary disease (greater than or equal to 50% stenosis). However, only 7% of patients had severely depressed left ventricular function with an ejection fraction less than or equal to 29%. Evaluation of the contribution of many clinical and angiographic variables to a first cardiac event (death, nonfatal reinfarction or coronary artery bypass surgery) was considered with Kaplan-Meier actuarial curves and multivariate Cox's hazard function analysis. A risk segment was defined as an area of contracting myocardium supplied by a coronary artery with a greater than 50% stenosis. Multivariate analysis demonstrated that right plus left anterior descending coronary artery stenoses (p less than 0.01), ejection fraction (p less than 0.01) and the presence of risk segments (p less than 0.05) were significant predictors of outcome. Furthermore, on separate multivariate analyses, the angiographic variables added significantly to the clinical variables to predict cardiac events over 5 years of follow-up. Therefore, in survivors of acute myocardial infarction who undergo cardiac catheterization, additive prognostic information is obtained that can be used to stratify risk over 5 years.

Neurobehavioral contributions to cardiac arrhythmias during aversive pavlovian conditioning in the rabbit receiving digitalis

Clinical observations suggest that a prevalent condition for the occurrence of cardiac arrhythmias is the synergistic interaction of several risk factors including digitalis glycosides, myocardial ischemia and psychological stress. However, little research has been directed toward controlled, systematic investigations of such synergistic interaction, particularly with respect to psychological stress and digitalis glycosides. The present research was undertaken to develop an animal model with which to study the behavioral and neurobiological contributions to arrhythmias during psychological stress in the presence of digitalis. The model used the rabbit as the experimental animal, a pavlovian aversive conditioning procedure and ouabain, a digitalis glycoside. Rabbits received pavlovian conditioning trials in which a tone as a conditioned stimulus (CS) was paired with an eyelid shock as an unconditioned stimulus (US). Twenty-four hours later, a retention test was given in which either of two doses of ouabain or saline was given, followed by 20 CS presentations alone. The CS presentations were given every 120 s (+/- 10 s). During ouabain infusion, the CS significantly increased the frequency of arrhythmic episodes compared to pre-CS baseline frequencies. These arrhythmic episodes were invariably preceded by CS-induced bradycardia. Both parasympathetic and sympathetic involvement were suggested in arrhythmogenesis, since the CS-induced increase in arrhythmic episodes was blocked by pretreatment with either atropine methylnitrate or atenolol. Furthermore, electrical stimulation of the amygdaloid central nucleus, an area implicated in the expression of bradycardia to a pavlovian CS in the rabbit produced arrhythmic episodes in the presence of ouabain. These arrhythmic episodes were similar in topography to CS-induced arrhythmias within any one animal and were decreased by atropine methylnitrate pretreatment. Insights into central and peripheral nervous system mechanisms by which psychological stress is capable of evoking cardiac arrhythmias in the presence of ouabain should ultimately lead to more effective treatment strategies for the prevention of these arrhythmias.

Death after acute myocardial infarction: interrelation between left ventricular dysfunction, arrhythmias and ischemia

Patients who survive an acute myocardial infarction face an increased risk of sudden death for approximately 6 months after hospital discharge; their prognosis is determined by the severity of their coronary arteriosclerosis and the degree of left ventricular dysfunction. Frequent ventricular premature complexes and evidence of ischemia either spontaneously or on treadmill are also markers for early morbidity and mortality in patients who are discharged from the hospital after acute myocardial infarction. The degree of left ventricular dysfunction is the strongest predictor of mortality; patients who have both left ventricular dysfunction, frequent premature ventricular beats and evidence of ischemia are at the highest risk of mortality after hospital discharge. It appears likely that all 3 of these risk factors interact and that therapy to reduce morbidity and mortality after myocardial infarction should aim at the amelioration of each of these risk factors. A model for the interaction of these risk factors is proposed and an approach to treatment for patients at high risk of mortality after hospital discharge after myocardial infarction is suggested.

Time-dependent change in electrophysiologic milieu after myocardial infarction in conscious dogs

This study was designed to assess the time-dependent change in propensity to induction of malignant ventricular tachyarrhythmia after myocardial infarction. Instrumented conscious dogs were assessed during serial drug-free electrophysiologic studies over 26 +/- 9 days (range 17 to 35 days) after 2 hr occlusion-reperfusion of the left anterior descending coronary artery. Of the 19 animals studied, 11 continued to have sustained ventricular tachyarrhythmias inducible (group I) over this time period. In the eight remaining animals, spontaneous loss in the ability to induce sustained ventricular tachycardia occurred (group II). Myocardial infarct size in group I animals (18 +/- 8%) was significantly greater than that in group II dogs (12.5 +/- 5%; p less than .05). Even in group I animals, time-dependent changes occurred in the number of extrastimuli required to induce ventricular tachycardia and the frequency with which left ventricular stimulation was necessary. A differential pattern of time-dependent changes in electrophysiologic variables was observed when comparing group I and II animals. The conduction time to the infarct zone was prolonged during follow-up in group I animals, while in group II animals this variable was unchanged. Repolarization time recorded in the border zone remained unchanged in group I animals, but it was significantly shortened in group II animals. In addition, ventricular effective refractory period in the infarct zone shortened over time in group I animals but did not change in group II animals. In conclusion, time-dependent changes occur in electrophysiologic variables that are associated with a progressive decrease in propensity to induction of ventricular tachycardia after myocardial infarction. A critical determinant of whether propensity to ventricular tachycardia resolves over time is size of myocardial infarction.

Cost-effectiveness analysis of patient management alternatives after uncomplicated myocardial infarction: a model

Quantitative decision analyses provide a means whereby the effectiveness, in terms of patient outcome, and costs of diverse clinical approaches to the care of patients with cardiovascular disease can be made explicit and understandable. Increasingly, the profession is being required to justify the costs of clinical care to society, government and third party payers. Such justifications can be effectively presented when structured in decision analytic format. To demonstrate the utility of decision analysis and its extension--cost-effectiveness analysis--as a technique for presenting the rationale for clinical practices and technology utilization, the Cardiovascular Norms Committee of the American College of Cardiology sponsored a model cost-effectiveness analysis. Alternative management options, 6 month mortality and costs for the post-myocardial infarction patient were compared. The options included exercise electrocardiography, exercise thallium scintigraphy and coronary angiography, followed by coronary artery bypass surgery for patients with left main coronary disease only or patients with left main disease, three vessel disease or single or double vessel disease and a significant amount of myocardium in jeopardy. Within the constraints of the model, proceeding directly to angiography for risk stratification was the most effective approach, lowering expected mortality from 8% to approximately 3%. The marginal costs for this strategy, however, were high. The most cost-effective approach was to screen patients initially with exercise electrocardiography.

The proarrhythmic effects of antiarrhythmic drugs

Although antiarrhythmic drugs are effective for controlling cardiac arrhythmias, they may also induce or exacerbate them. Case reports have appeared implicating all classes of antiarrhythmic drugs. It is difficult to assess the size of the problem in practice, as it varies with different subgroups of patients, but rates of up to 13% have been found where proarrhythmic effects were actively sought. Their occurrence is affected both by the electrophysiologic characteristics of the drugs and by the arrhythmia substrate. Mechanisms of proarrhythmic effects may be classified according to the electrophysiologic and hemodynamic effects of the drugs. Detection of drug-induced arrhythmias depends on appreciation of the problem by physicians and, although there are few clear predictors, some form of monitoring of antiarrhythmic drug treatment is recommended. Management of such arrhythmias when they occur involves withdrawal of the offending agent, correcting contributory factors, and reassessing the initial arrhythmia and the strategy for its management.

Prognostic significance of ventricular ectopic activity in survivors of acute myocardial infarction

Twenty-four hour ambulatory electrocardiography was performed on 3,290 survivors of acute myocardial infarction participating in the Beta-Blocker Heart Attack Trial (BHAT). History of myocardial infarction before the qualifying event, congestive heart failure and age were independently associated with the frequency and complexity of ventricular premature beats. Of the 1,640 patients randomized to placebo therapy, 163 died (76 suffered sudden death) during a 25 month average follow-up period. Ventricular ectopic activity was an independent predictor of total mortality after taking into consideration 16 other prognostic factors describing past history, risk factors, physical examination and laboratory investigations. Seven categoric definitions of ventricular ectopic activity predicted mortality, with similar odds ratios ranging from 2.27 to 2.69. A reciprocal relation of the sensitivity and specificity of each definition in predicting mortality was observed. Three clinical criteria (ST depression, cardiomegaly and prior infarction) allowed stratification of patients into four subsets with respective mortality rates of 35.5% (three criteria present), 19.0% (two criteria), 11.5% (one criterion) and 4.7% (none). Presence of ventricular ectopic activity (greater than or equal to 10 ventricular premature beats/h or pairs, ventricular tachycardia or multiform complexes) was associated with higher mortality rates in all four risk strata. The relative risk was higher (3.86) in the lowest risk stratum (mortality 2.4% without and 9.1% with ventricular ectopic activity). Thus, in survivors of acute myocardial infarction, ventricular ectopic activity was more pronounced in patients with prior myocardial infarction and congestive heart failure. It predicted mortality independently of other factors. Although mortality ratios were similar for all seven arrhythmia definitions, a reciprocal relation between sensitivity and specificity of the definitions in predicting mortality existed; ventricular ectopic activity was associated with increased mortality in all risk strata, but with a higher risk ratio in the numerically larger, low risk subset.

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.

Long-term reproducibility and significance of provokable ventricular arrhythmias after myocardial infarction

The long-term reproducibility and significance of inducible ventricular arrhythmias were assessed in 21 survivors of a myocardial infarction. Programmed ventricular stimulation performed a mean of 12 +/- 2 days (range 8 to 18) after infarction provoked ventricular fibrillation in 2 patients, sustained monomorphic ventricular tachycardia in 8 and nonsustained ventricular tachycardia in 11. Patients were restudied using the same protocol a mean of 8 +/- 2 months (range 4 to 11) after infarction. All patients underwent programmed ventricular stimulation studies in the absence of antiarrhythmic drug treatment. Ventricular tachyarrhythmias could be reinitiated in 16 patients (76%): ventricular fibrillation in 2, sustained ventricular tachycardia in 5 (monomorphic in 4) and nonsustained ventricular tachycardia in 9. A preponderance of inferior infarction was observed among patients with reinducible tachycardias (9 of 16 patients versus 0 of 5 with noninducible tachycardias) (p less than 0.05). No significant difference existed between patients with and without reinducible arrhythmias with respect to severity of coronary artery disease, degree of left ventricular dysfunction, occurrence of ventricular fibrillation in the acute phase of infarction and ventricular arrhythmias detected by 24 hour ambulatory electrocardiographic (Holter) monitoring. There was no significant difference between patients with and without a positive late study in stimulation thresholds, ventricular refractory periods, time interval between initial and repeat testing and use of beta-adrenergic blocking agents. During a mean follow-up period of 17 months (range 10 to 23) one patient with inducible sustained monomorphic ventricular tachycardia at both studies died suddenly. The remaining patients have survived follow-up without experiencing an arrhythmic event.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of early reperfusion in acute myocardial infarction on arrhythmias induced by programmed stimulation: a prospective, randomized study

This study compares inducibility of ventricular tachyarrhythmias by programmed electrical stimulation of the heart in patients with myocardial infarction with and without reperfusion after streptokinase therapy. Sixty-two consecutive patients admitted with an acute myocardial infarction were randomized to either combined intravenous and intracoronary streptokinase (streptokinase group) or to standard coronary care unit treatment (control group). Thirty-six of the 62 patients (21 patients from the streptokinase and 15 from the control group) with a first myocardial infarction were studied by programmed ventricular stimulation after a mean of 26 +/- 14 days. No patient had a history of antiarrhythmic drug use or documentation of a ventricular arrhythmia before the initial admission. A sustained ventricular arrhythmia was induced in 10 (48%) of the 21 patients randomized to streptokinase therapy and in all 15 (100%) control patients (p less than 0.001). Sustained monomorphic ventricular tachycardia was induced in 6 (29%) and 10 (67%) patients, respectively (p less than 0.05). To terminate an induced arrhythmia, direct current countershock was required in 33% of patients in the streptokinase group and 73% of patients in the control group (p less than 0.02). Seventeen of the 21 patients treated with streptokinase and no control patient had evidence of early reperfusion 200 +/- 70 minutes after the onset of pain. In comparison with patients without early reperfusion, patients in the reperfused group had a lower maximal serum creatine kinase value (p less than 0.01), a shorter time to peak creatine kinase value (p less than 0.001) and a higher angiographic left ventricular ejection fraction (62 versus 45%, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiologic characteristics of ventricular tachycardia or fibrillation in relation to age of myocardial infarction

Evaluation of ventricular myocardium after the onset of acute myocardial infarction (AMI) suggests that the substrate for ventricular arrhythmias changes as the substrate for ventricular arrhythmias changes as the AMI heals. To determine if the ability of programmed stimulation to initiate ventricular tachycardia (VT) varies according to the interval between AMI and electrophysiologic testing, the clinical and electrophysiologic data of 42 patients with spontaneous sustained VT and 12 patients with ventricular fibrillation (VF) more than 3 days after a single AMI were analyzed. For patients with VT, there were no significant differences in the incidence of initiation of sustained monomorphic VT among those evaluated 1 to 3 weeks (100%), 3 to 8 weeks (75%), 2 to 6 months (100%), 6 to 18 months (80%) or more than 18 months (81%) after AMI, and the mean number of extrastimuli required for initiation did not differ among the groups. Patients evaluated more than 4 weeks after the initial episode of VT had a lower incidence of inducible VT than those studied earlier (14 of 21 [71%] vs 21 of 21 [100%], p less than 0.05), although this appeared to be a result of earlier termination of the stimulation protocol owing to initiation of polymorphic arrhythmias in those studied later. The 14 patients evaluated within 8 weeks of AMI had significantly faster VT rates (mean cycle length 269 +/- 45 ms) than the 28 patients studied later (320 +/- 75 ms, p less than 0.01), possibly because of more out-of-hospital presentations of VT in patients studied later.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency and significance of induced sustained ventricular tachycardia or fibrillation two weeks after acute myocardial infarction

Electrophysiologic study, 24-hour ambulatory electrocardiographic monitoring, treadmill exercise test and angiographic evaluations were performed in 45 patients 14 +/- 3 days (mean +/- standard deviation) after acute myocardial infarction. Electrophysiologic study protocol included burst ventricular pacing and 1 to 3 ventricular extrastimuli at 2 cycle lengths from right ventricular apex, right ventricular outflow and left ventricle. Sustained monomorphic ventricular tachycardia (VT) (13 patients) or ventricular fibrillation (VF) (7 patients) was induced in 20 patients (44%) (group I). In these 20 patients, VT/VF was inducible with 2 extrastimuli in 10 patients, 3 extrastimuli in 9 patients and burst pacing in 1 patient. In the remaining 25 patients (56%), induction of no fewer than 7 ventricular beats were noted (group II). Severe left ventricular (LV) wall motion abnormalities occurred in 70% of group I patients and 22% of group II patients (p less than 0.005). There was no difference in the site of infarction, frequency and grade of ventricular ectopic rhythm on ambulatory electrocardiographic monitoring, double product on submaximal exercise, LV ejection fraction, and number of obstructed coronary arteries (70% or greater) (p greater than 0.1) between group I and group II patients. During a mean follow-up of 10 +/- 3 months, 1 patient in each group died suddenly, and in 1 group I patient spontaneous sustained VT developed which was identical in morphologic configuration to that induced during electrophysiologic study. In conclusion, electrical induction of sustained VT or VF during electrophysiologic study is common in patients 2 weeks after acute myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Value of programmed stimulation and exercise testing in predicting one-year mortality after acute myocardial infarction

The ability of programmed ventricular stimulation and exercise testing to predict 1-year mortality after acute myocardial infarction (AMI) was investigated in 228 clinically well survivors of AMI. Patients with inducible ventricular tachycardia (VT) or ventricular fibrillation (VF) had a higher mortality rate than those without inducible arrhythmias (26% vs 6%, p less than 0.001). Exercise-induced ST-segment change of 2 mm or more was associated with a higher mortality rate than ST change of less than 2 mm (11% vs 4%, 0.05 less p less than 0.10). Of patients who had both tests, 62% had no inducible ventricular tachycardia or ventricular fibrillation and ST change of less than 2 mm, and only 1% died during the first year. Thus, in clinically well survivors of AMI, programmed stimulation is a powerful predictor of first-year mortality; programmed stimulation and exercise testing together predict virtually all deaths within the first year, and they can identify a large group of patients with a very low mortality rate.

Prediction of sudden death and spontaneous ventricular tachycardia in survivors of complicated myocardial infarction: value of the response to programmed stimulation using a maximum of three ventricular extrastimuli

The prognostic significance of ventricular arrhythmias induced by programmed electrical stimulation was evaluated in 50 survivors of acute myocardial infarction complicated by a major new conduction disturbance (38 patients), congestive heart failure (33 patients) or sustained ventricular tachyarrhythmias (22 patients), alone or in combination. Programmed stimulation was performed in patients in stable condition 7 to 36 days (mean 16) after infarction using one to three extrastimuli at four times diastolic threshold at a maximum of two right ventricular sites. Two groups were identified by the response to programmed stimulation: 17 patients with sustained (greater than 15 seconds) or nonsustained (greater than 7 beats but less than or equal to 15 seconds) ventricular tachycardia (group I), and 33 patients with 0 to 7 intraventricular reentrant complexes in response to maximal stimulation efforts (group II). Group I patients had a higher incidence of anterior infarction than that of patients in group II (71 versus 42%), had lower left ventricular ejection fraction (mean 0.35 versus 0.48) and were more often treated with antiarrhythmic drugs (47 versus 18%, p less than 0.05). There were no significant differences between groups in the occurrence of congestive failure, new conduction disorders or sustained ventricular arrhythmias with infarction, or in the proportions treated with a beta-receptor blocking agent, coronary bypass grafting or a permanent pacemaker. Total cardiac mortality was 24% during a mean follow-up period of 23 months and did not differ between groups; however, the response to programmed stimulation identified a group at high risk of late sudden death or spontaneous ventricular tachycardia: 7 (41%) of 17 group I patients compared with 0 of 33 group II patients (p less than 0.001). The induction of sustained or nonsustained ventricular tachycardia identified all patients who died suddenly or had spontaneous tachycardia (sensitivity 100%), but triple extrastimuli were required to induce prognostically significant arrhythmias in five of these seven patients; the specificity of this protocol was only 57%. When the clinical variables of the group were evaluated individually, the response to programmed stimulation had a stronger association with occurrence of late sudden death than did any other factor (Fisher's exact test, p less than 0.001); however, a type II error could not be excluded.(ABSTRACT TRUNCATED AT 400 WORDS)

Intramural reentry as a mechanism of ventricular tachycardia during evolving canine myocardial infarction

We evaluated the contribution of intramural electrical events in initiation and maintenance of ventricular tachycardia in 15 dogs 3-8 days after either permanent (n = 2) or transient (n = 13) coronary artery occlusion. Seven of the dogs (47%) demonstrated eight distinct monomorphic ventricular tachycardia patterns which were mapped by means of a recently designed computerized system capable of simultaneously detecting, storing, and assessing information from 232 individual cardiac sites. Using both epicardial and intramural electrodes, we found definitive evidence for intramural reentry in seven of the eight monomorphic tachycardias analyzed. Furthermore, five of these animals (71%) demonstrated microreentry, in which small epicardial conduction loops exited intermittently into nonrefractory subendocardium to initiate succeeding beats, while, in the remaining two dogs, ventricular tachycardia was due to macroreentry, during which the broad subendocardial wavefronts depolarizing the ventricle constituted the proximal (fast) reentry limbs. Detailed anatomical analysis of the resultant infarcts demonstrated the thin surviving epicardial tissue rim to be the site of conduction delay necessary for reentry, whereas "preferred pathways" of exit into the subendocardial plane occurred at the infarct borders and were of variable configuration. Successful interruption of these rhythms should accompany interference with the process of exit into nonrefractory subendocardial tissue.

Prognosis after myocardial infarction--prediction in ambulatory patients by use of the bedside Valsalva maneuver

One hundred survivors of first myocardial infarction were studied prior to hospital discharge by 24 hour ambulatory electrocardiography as well as radionuclide ventriculography. The bedside Valsalva maneuver, with simple sphygmomanometric determination of arterial pressure response, was performed 6 weeks post infarction and patients were followed for a mean of 22 months. The arterial pressure response pattern provided a semiquantitative estimate of resting left ventricular systolic function when related to the radionuclide ejection fraction (SIN, 0.56 +/- 0.13; ABO, 0.43 +/- 0.18; SQW, 0.16 +/- 0.06) (P less than 0.02). Abnormal Valsalva responses (ABO and SQW) were found more commonly in patients with diminished left ventricular systolic function and high grade ventricular arrhythmias. The SQW response pattern was highly predictive of future sudden cardiac death. The bedside Valsalva maneuver, performed 2-4 weeks after hospital discharge, upon the ambulatory patient is a simple, safe, inexpensive and uniformly applicable method which may serve as the basis for a strategy with which to approach the post-infarction patient regarding risk stratification and further clinical management.

Prognostic implications of complicated ventricular arrhythmias early after hospital discharge in acute myocardial infarction: a serial ambulatory electrocardiography study

To assess the prevalence and prognostic implications of complicated ventricular ectopic depolarizations (VEDs) after hospital discharge in patients with acute myocardial infarction (AMI), we obtained serial 24-hour Holter recordings in 85 patients during the first 6 weeks after AMI. Recordings were obtained during two coronary care unit time intervals, two hospital ward time intervals, and during four weekly time intervals after discharge. Complicated VEDs were defined as unifocal VEDs greater than or equal to 10/1000 beats for 24 hours, multiform VEDs, pairs, or ventricular tachycardia. At 1 year follow-up, there were nine cardiac deaths (six sudden deaths and three deaths from recurrent AMI). The mean left ventricular ejection fraction at discharge in the cardiac death patients was 29 +/- 12% (sudden death patients 24 +/- 11% and AMI death patients 40 +/- 6%) compared to 49 +/- 13% in the survivors (p less than 0.001). Patients with complicated VEDs at discharge (2 weeks after AMI) or during the first 4 weeks after discharge (3 to 6 weeks after AMI) were significantly more likely to have sudden death at follow-up compared to patients without complicated VEDs. Of the six sudden death patients, four (66%) had complicated VEDs at discharge compared to 18 of 68 survivors (26%) (p less than 0.05). One of three patients who died of recurrent AMI had complicated VEDs. No Holter data were obtained at hospital discharge in eight of the survivors.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of early prehospital transtelephonic coronary intervention on morbidity and mortality: experience with 284 postmyocardial infarction patients in a pilot program

We have evaluated, in a pilot study, the effects of subsequent mortality and morbidity of a prehospital program for postmyocardial infarction patients experiencing recurrent chest pain. Two hundred eighty-four patients were enrolled during their late hospital period: 161 in a program incorporating patient education, routine transtelephonic follow-up, and emergency prehospital CCU-controlled intervention; 124 in a control group receiving usual medical care. Cardiac mortality over a median of 13 months of follow-up was significantly reduced in the treatment group (5.8%) vs control (12.9%), p = 0.036, although the incidence of acute events (nonfatal infarction plus cardiac death) was similar in both groups. This suggests that the program does not affect the acute incident but rather the mortality subsequent to it. Prehospital ventricular arrhythmias present in 7 of 54 treatment patients with recurrent chest pain did not recur following self-injection by a prefilled lidocaine syringe; only one patient who was initially arrhythmia-free had ventricular ectopic beats after lidocaine injection. Delay from onset of symptoms to hospital arrival was 1.9 hours. Routine telephone follow-up uncovered ventricular arrhythmias in 30% of treatment patients and, despite the program's patient educational efforts, unreported angina in 20% of the treatment group. In the treatment group there were 99 emergency calls placed by 62 patients, 50% within 12 weeks after discharge and 80% by 35 weeks, resulting in 74 Emergency Department evaluations and 57 hospital admissions. Overuse of the emergency system occurred with only one patient, and physician acceptance was high.(ABSTRACT TRUNCATED AT 250 WORDS)

Identifying patients at risk of sudden death after myocardial infarction: value of the response to programmed stimulation, degree of ventricular ectopic activity and severity of left ventricular dysfunction

The ability of programmed ventricular stimulation to identify risk of sudden death after acute myocardial infarction (MI) was compared with 24-hour electrocardiographic assessment of ventricular ectopic activity and determination of left ventricular (LV) dysfunction. Forty-six patients underwent programmed stimulation 8 to 60 days (mean 22) after documented MI. Programmed stimulation consisted of single and double extrastimuli from the right ventricular apex at 2 times diastolic threshold during ventricular pacing and normal sinus rhythm. Of the 46 patients, 44 underwent electrocardiographic monitoring at least 6 days after MI. In 43 of the 46 patients, LV ejection fraction (EF) and the presence of LV aneurysm were determined. In response to programmed ventricular stimulation, 5 patients had sustained ventricular tachycardia (VT), 5 had nonsustained VT (greater than or equal to 4 beats), 13 had intraventricular reentrant repetitive responses, and 23 had either bundle branch reentrant repetitive responses or no extra responses to programmed ventricular stimulation (negative study). During a mean follow-up of 18 months, 10 patients died, 6 suddenly. One of the 10 patients with sustained or nonsustained VT died suddenly, compared with 3 of 13 patients with intraventricular reentrant responses and 2 of 23 patients with a negative study (difference not significant). Of 25 patients with Grade 0 to 2 ventricular ectopic activity, 3 died suddenly after MI, compared with 3 of 19 patients with Grade 3 or 4 activity (difference not significant). By comparison, the frequency of sudden death was greater in patients with an LVEF of less than 40% (5 of 16 versus 1 of 27 patients) or an LV aneurysm (5 of 13 versus 1 of 30 patients).(ABSTRACT TRUNCATED AT 250 WORDS)