Ventricular performance and prognosis after primary ventricular fibrillation complicating acute myocardial infarction

Time-dependent predictors of primary cardiac arrest in patients with acute myocardial infarction

To understand predictors of cardiac arrest early in acute myocardial infarction (AMI), for the Thrombolytic Predictive Instrument, we developed a multivariable regression model predicting primary cardiac arrest using time-dependent variables based on a case-control study of emergency department (ED) patients with AMI: 65 cases with sudden cardiac arrest and 258 without cardiac arrest. Within the first hour of AMI symptom onset, adjusting for age, systolic blood pressure, serum potassium, and infarct size, increased risk of cardiac arrest was associated with electrocardiographic prolonged QTc interval and a greater sum of ST-segment elevation. After 1 hour, the effect of ST-segment elevation was much reduced and the effect of the QTc interval was reversed, so prolonged QTc appeared protective. Accordingly, for patients presenting 30 minutes after chest pain onset, compared with a QTc of 0.44, the risk for cardiac arrest for patients with QTc of 0.50 was more than doubled (odds ratio [OR] 2.20, 95% confidence intervals [CI] 1.17 to 4.13), whereas for those presenting after an hour, it was much lower (e.g., at 1.5 hours, OR 0.21, 95% CI 0.06 to 0.73). Patients presenting 30 minutes after chest pain onset with a sum of ST elevation of 20 mm had a threefold higher risk than patients with a sum of ST elevation of 5 mm (OR 3.37, 95% CI 1.83 to 6.20). However, if presenting 1.5 hours after chest pain onset, the risk was barely elevated (OR 1.18; 95% CI 1.09 to 1.29). Thrombolytic therapy was protective, halving the odds of cardiac arrest (OR 0.51, 95% CI 0.27 to 0.93). Thus, the relation of prolonged QTc interval and substantial ST segment elevation to cardiac arrest in AMI may be obscured because patients with these risks are more likely to die soon after AMI onset, before ED presentation, and are thereby unavailable for study. Those with prolonged QTc or substantial ST elevation who survive the initial 1.5-hour period are those less susceptible to these risks.

Incidence and prognosis of early primary ventricular fibrillation in acute myocardial infarction--results of the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI-2) database

Primary ventricular fibrillation (VF) complicating acute myocardial infarction (MI) predicts short-term mortality. The broad category of patients with primary VF might include subgroups with different outcomes. It is still not certain whether early-onset (< or =4 hours) primary VF is a risk predictor, and information on correlates of these early fibrillations is scarce. This study sought to prospectively analyze the incidence and prognosis of early, as opposed to late (time window >4 to 48 hours) primary VF and retrospectively identify predisposing factors for early-onset primary VF. We analyzed the incidence and recurrence rate of early and late primary VF in 9,720 patients with a first acute MI, treated with thrombolytics, enrolled in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI)-2 trial. The independent prognostic significance of early and late primary VF was assessed by logistic regression analysis. The incidence rates of early and late primary VF were 3.1% and 0.6%, respectively; recurrence rates were 11% and 15%, respectively. The 2 variables most closely related to early primary VF were hypokalemia and systolic blood pressure < 120 mm Hg on admission. Patients with early primary VF had a more complicated in-hospital course than matched controls. Both early (odds ratio [OR] 2.47, 95% confidence interval [CI] 1.48 to 4.13) and late primary VF (OR 3.97, 95% CI 1.51 to 10.48) were independent predictors of in-hospital mortality. Postdischarge to 6-month death rates were similar for both primary VF subgroups and controls. Primary VF, irrespective of its timing, was an independent predictor of in-hospital mortality. Postdischarge to 6-month prognosis was unaffected by the occurrence of either early or late primary VF.

Is ventricular wall stress rather than left ventricular hypertrophy an important contributory factor to sudden cardiac death?

Sudden cardiac death comprises a significant proportion of cardiac mortality in Western society. Left ventricular hypertrophy has been identified by many authors as a possible risk factor for sudden cardiac death, however, left ventricular hypertrophy develops in response to external stimuli on the heart as a means of normalizing wall stress. It is possible that the fundamental abnormalities in wall stress, rather than the left ventricular hypertrophy itself, pose the increased risk of sudden death. Left ventricular hypertrophy, the consequence of raised wall stress, is easy to measure and easy to study and it is understandable why this parameter should have received more attention. Wall stress by contrast is difficult to measure, and worse, is variable throughout the ventricle so that it cannot be measured in a single quantifiable figure. As a consequence, only a limited amount of attention has been paid to wall stress as a possible trigger mechanism for cardiac arrhythmia. However, there is evidence from both basic and clinical research to suggest that raised wall stress may be a risk factor for sudden cardiac death and cardiac arrhythmia. This review discusses the evidence for and against left ventricular hypertrophy and wall stress as risk factors for sudden cardiac death, and also presents recent evidence that left ventricular hypertrophy in isolation can protect the heart against the arrhythmogenic effects of raised wall stress.

Ventricular arrhythmias in trials of thrombolytic therapy for acute myocardial infarction. A meta-analysis

BACKGROUND

Although thrombolytic therapy reduces long-term mortality in acute myocardial infarction, many clinicians remain concerned about an increased risk of ventricular arrhythmias associated with the use of these agents.

METHODS AND RESULTS

To determine whether thrombolytic therapy increases the risk of ventricular tachyarrhythmias and whether an increase in arrhythmias could be responsible for the increased mortality seen in the first 24 hours after lytic therapy, we performed a meta-analysis of 15 randomized trials of thrombolysis in acute myocardial infarction in which the odds of developing in-hospital ventricular fibrillation (VF) and ventricular tachycardia (VT) in patients receiving thrombolysis was compared with that of patients receiving placebo. For trials that reported the incidence of VF during the first 6 hours after thrombolysis, the summary odds ratio for developing VF in the thrombolytic group was 0.98 (95% confidence interval [CI], 0.6 to 1.6; P = .94). For trials that reported the incidence of VF during the first hospital day, the summary odds ratio for developing VF was 1.00 (95% CI, 0.85 to 1.2; P = .95). The summary odds ratio for the development of VF at any time during hospitalization in the thrombolytic group was 0.83 (95% CI, 0.76 to 0.90; P < .0001). In trials that reported the incidence of VT any time during hospitalization, the summary odds ratio for the development of VT in the thrombolytic group was 1.34 (95% CI, 1.15 to 1.55; P < .0001).

CONCLUSIONS

The likelihood of developing VF in the early hours after thrombolysis for acute myocardial infarction is similar in patients receiving thrombolytics or placebo. However, throughout the hospital course, the risk of VF is greater in patients receiving placebo, whereas the risk of VT is higher in patients receiving thrombolysis.

Incidence and significance of ventricular tachycardia and fibrillation in the absence of hypotension or heart failure in acute myocardial infarction treated with recombinant tissue-type plasminogen activator: results from the Thrombolysis in Myocardial Infarction (TIMI) Phase II trial

OBJECTIVES

The purpose of this study was to determine the incidence of ventricular tachycardia and fibrillation without hypotension or heart failure after treatment with recombinant tissue-type plasminogen activator (rt-PA), anatomic correlates of their development, the effect of immediate intravenous metoprolol on their occurrence and the outcome of patients with these arrhythmias.

BACKGROUND

Malignant arrhythmias after thrombolytic therapy have been reported to occur as a result of coronary reperfusion, which is associated with reduced mortality in patients receiving thrombolytic therapy.

METHODS

We analyzed data from 2,546 patients in the Thrombolysis in Myocardial Infarction (TIMI) Phase II trial without congestive heart failure or hypotension during the 1st 24 h after study entry. Forty-nine patients (1.9%) developed sustained ventricular tachycardia or ventricular fibrillation within 24 h of study entry (group 1), and 2,497 patients (98.1%) did not (group 2).

RESULTS

Baseline characteristics and admission laboratory values were similar in the two groups. In patients undergoing protocol angiography 18 to 48 h after rt-PA, the infarct-related artery was patient in a greater percent of group 2 patients (87% [1,015 of 1,169]) than group 1 patients (68% [15 of 22], p = 0.01), although angiography was performed less frequently in group 1 than in group 2. More group 1 than group 2 patients died within 21 days (20.4%) (1.6%, p < 0.001). For patients surviving to 21 days, there was no difference in mortality between patients in the two groups in the following year.

CONCLUSIONS

Ventricular tachycardia and fibrillation are not markers for reperfusion after thrombolytic therapy. These arrhythmias are associated with occlusion, not patency, of the infarct-related artery. Early mortality is increased in patients who develop ventricular tachycardia and fibrillation, even in the absence of congestive heart failure and hypotension.

Prognosis of acute myocardial infarction complicated by primary ventricular fibrillation. Principal Investigators of the SPRINT Study

In 5,839 consecutive patients with acute myocardial infarction (AMI), hospitalized between July 1981 and July 1983 in 14 coronary care units in Israel, the incidence of primary ventricular fibrillation (VF) was 2.1%. Patients with primary VF resembled counterparts without VF in terms of age, gender, frequency of previous AMI and past cigarette smoking habits. The hospital course of patients with primary VF revealed increased incidence of primary atrial fibrillation and atrioventricular block. Increased serum levels of glutamic oxaloacetic transaminase and lactic dehydrogenase were noted among the patients with primary VF. In-hospital mortality rate was 18.8% in 122 patients with primary VF compared with 8.5% in 3,707 patients forming the reference group (p less than 0.01). Adjustment by age using logistic function yielded an estimate of 2.86 for relative mortality odds associated with primary VF, and further adjustment by gender, history of AMI, systemic hypertension, and by enzymatically estimated infarct size slightly reduced the estimated odds, at 2.52 (95% confidence interval, 1.42 to 4.46). Prognosis after discharge from the hospital was independent of primary VF. In conclusion, primary VF exerts an independent, significant effect on in-hospital mortality.

Six year follow up of a consecutive series of patients presenting to the coronary care unit with acute chest pain: prognostic importance of the electrocardiogram

In a retrospective 6 year follow up data were obtained for 536 of 566 (95%) consecutive patients admitted to a coronary care unit with acute chest pain. Their diagnoses were acute myocardial infarction in 290 (54%), myocardial ischaemia in 164 (31%), pericarditis in 16 (3%), and non-cardiac in 66 (12%). Six year mortality was 36%, 24%, 0%, and 16% respectively. In patients with acute myocardial infarction a higher mortality rate during follow up was associated with a higher than average age, a higher than average creatine kinase, previous myocardial infarction, Q wave infarction, and the presence of reciprocal changes. The presence of reciprocal changes was associated with higher than average concentration of serum creatine kinase, indicating more extensive infarction. Infarction complicated by ventricular fibrillation or left bundle branch block was associated with a higher death rate. The electrocardiogram recorded at the time of acute myocardial infarction contains much useful prognostic information.

Long-term prognosis after resuscitation from primary ventricular fibrillation complicating acute transmural myocardial infarction in the north east of Scotland

The aim of this study is to determine the long-term prognosis of patients successfully resuscitated from primary ventricular fibrillation in the acute phase of transmural myocardial infarction and to identify predictors of mortality. Details of 75 consecutive patients between October 1971 and May 1981 were reviewed in October 1985. The cumulative survival rates at one year, two year, five year and 10 year were 84%, 77% 67% and 40.5% respectively with a median survival time of 8.7 years. Univariate and Cox survival analyses were used to determine predictors of mortality. Only the age of the patient at the time of infarction was found to be highly significant with a greatly increased mortality rate in the older age group (p less than 0.001). The sex, site of infarction (anterior or inferior) and time of entry in the study did not significantly influence long-term prognosis.

In-hospital prognosis of patients with acute myocardial infarction complicated by primary ventricular fibrillation

The in-hospital prognosis of patients with acute myocardial infarction complicated by primary ventricular fibrillation has not been satisfactorily defined. We addressed this question by studying patients with primary ventricular fibrillation derived from a large study (11,712 patients) of intravenous streptokinase in the treatment of acute myocardial infarction. Ventricular fibrillation was considered to be primary when it complicated a first myocardial infarction not associated with heart failure or shock and occurred within 48 hours of hospital admission. The 332 patients with primary ventricular fibrillation represented an overall incidence of 2.8 percent. A significant excess of in-hospital deaths was found in the patients with primary ventricular fibrillation as compared with those in the reference group (10.8 percent vs. 5.9 percent; relative risk, 1.94; 95 percent confidence interval, 1.35 to 2.78). Thrombolytic treatment with intravenous streptokinase did not afford protection against primary ventricular fibrillation. We observed that being over 65 years old had a protective effect against primary ventricular fibrillation (relative risk, 0.6; 95 percent confidence interval, 0.45 to 0.80). Our data do not indicate whether primary ventricular fibrillation is simply a marker for patients at increased risk of death or a direct cause of the increase in mortality. Our results do show, however, that primary ventricular fibrillation occurring in a coronary care unit is a negative predictor of short-term survival in patients with acute myocardial infarction.

Survival to leave hospital from ventricular fibrillation

In 125 consecutive patients with 173 arrests due to ventricular fibrillation, 53 survived to leave hospital. At the initial arrest and using univariate analysis, those who had primary ventricular fibrillation, had ventricular fibrillation less than 24 hours from the onset of symptoms, received the first DC shock less than 1 minute after the onset of ventricular fibrillation, who required less than 4 shocks to terminate the ventricular fibrillation, whose first established rhythm within the first minute of correction of ventricular fibrillation was atrial fibrillation, sinus rhythm or paced rhythm, or who were not receiving prior antiarrhythmic agents had a significantly improved survival to leave hospital (p less than 0.05). To predict survival to leave hospital using discriminant function analysis, the most significant factors ranking in order of importance at the time of the initial arrest were: less than or equal to 5 shocks to correct ventricular fibrillation, no prior antiarrhythmic therapy, primary ventricular fibrillation, and time from onset of ventricular fibrillation to first shock less than 1 minute. For the last arrest, the most significant factors were: no prior cardiac arrest, less than or equal to 5 shocks to correct ventricular fibrillation, no prior antiarrhythmic therapy, and primary ventricular fibrillation. The most significant factors measured at the time of the last arrest provided a better prediction of survival to leave hospital (sensitivity 77%, specificity 75%) than did similarly defined factors for the initial arrest (sensitivity 59%, specificity 89%).

Intravenous magnesium in acute myocardial infarction

In a double-blind, placebo-controlled study, 273 patients with suspected acute myocardial infarction (AMI) were randomised to receive either magnesium intravenously or placebo immediately on admission to hospital. Of 130 patients with proven AMI 56 received magnesium and 74 received placebo. During the first 4 weeks after treatment mortality was 7% in the magnesium group and 19% in the placebo group. In the magnesium group 21% of patients had arrhythmias that needed treatment, compared with 47% in the placebo group. No adverse effects of intravenous magnesium were observed.

Effect of propranolol in patients with myocardial infarction and ventricular arrhythmia

The Beta-Blocker Heart Attack Trial was a placebo-controlled, randomized, double-blind clinical trial of the long-term administration of propranolol hydrochloride to patients who had had at least one myocardial infarction. Among 3,837 patients followed up for an average of 25 months, 3,290 (85.7%) had 24 hour ambulatory electrocardiograms performed at the baseline examination. Four classifications of arrhythmia were examined. One of these, the presence of complex ventricular arrhythmias (at least 10 ventricular premature beats/h, or at least one pair or run of ventricular premature beats or multiform ventricular premature beats) was the subgroup of major interest. Regardless of the classification, the presence of arrhythmia identifies a group of patients with a higher risk of total mortality, coronary heart disease mortality, sudden cardiac death and instantaneous cardiac death. The a priori subgroup hypothesis that sudden death would be preferentially reduced by propranolol in patients with complex ventricular arrhythmias was not supported. The relative benefit of propranolol in reducing sudden death for this subgroup was 28 versus 16% for the subgroup without ventricular arrhythmia (relative risk of 0.72 versus 0.84, a nonsignificant relative difference of 14%). There were similar findings for two of the three other classifications of arrhythmia and for the other response variables. Although propranolol does not appear to be of special relative benefit in patients with ventricular arrhythmia, the presence of the arrhythmia does identify a high-risk group. The mechanism by which propranolol reduces mortality is still unclear, but is probably not solely an antiarrhythmic one.