Primary ventricular fibrillation

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.

Prognosis of early versus late ventricular fibrillation complicating acute myocardial infarction

Earlier studies have suggested that patients exhibiting late (> 24 h) ventricular fibrillation during acute myocardial infarction had a poorer outcome in comparison to myocardial infarction patients with early (< 24 h) ventricular fibrillation. Between August 1981 and July 1983, 5839 consecutive patients with acute myocardial infarction were hospitalized in 13 out of 21 operating coronary care units in Israel. Demographic and medical data were collected from hospitalization charts and during 1 year of follow-up. Mortality assessment was done for 99% of hospital survivors up to mid-1988 (mean, 5.5 years). The incidence of ventricular fibrillation in the SPRINT Registry was 6% (371/5839). Patients with ventricular fibrillation in the setting of cardiogenic shock (n = 107) were excluded from analysis. Patients with late ventricular fibrillation (n = 109; 41%) were older and had a more complicated hospital course than patients with early ventricular fibrillation (n = 155; 59%). In-hospital and 1-year post-discharge mortality were significantly higher in patients with late ventricular fibrillation (63% and 17%) as compared to patients with early ventricular fibrillation (26% and 4%, respectively; P < 0.05 for each). This difference vanished 5 years after hospital discharge. After multiple logistic regression analysis late occurrence of ventricular fibrillation emerged as an independent predictor of increased in-hospital mortality (Odds ratio, 4.29; 95% confidence interval, 2.11-8.74) but not for subsequent death. Patients with late ventricular fibrillation during the hospital course of acute myocardial infarction had a poorer immediate and subsequent outcome in comparison to patients with early ventricular fibrillation.

Declining incidence of ventricular fibrillation in myocardial infarction. Implications for the prophylactic use of lidocaine

BACKGROUND

The purposes of the present investigation were 1) to track the incidence of primary ventricular fibrillation (VF) in the control and lidocaine-treated groups in the randomized control trials (RCTs) of lidocaine prophylaxis against primary VF in acute myocardial infarction, with particular emphasis on the time frame of the randomized trial, and 2) to estimate the number of patients who must receive lidocaine currently to prevent one episode of VF.

METHODS AND RESULTS

The following variables from RCTs published between 1969 and 1988 were entered into logistic regression models to predict the percent of patients developing VF: year of publication of the RCT, method of data analysis used in the RCT, route and technique of lidocaine administration, duration of monitoring for VF, and exclusion criteria before randomization (congestive heart failure/cardiogenic shock, ventricular tachycardia/VF, or bradycardia/atrioventricular block). Year of publication was a significant predictor of VF in both the control and lidocaine groups (p less than or equal to 0.002) even after adjusting for other covariates. Based on a univariate logistic regression model with year as the predictor variable, it was estimated that the incidence of primary VF in the control group fell from 4.51% in 1970 to 0.35% in 1990 and from 4.32% down to 0.11% for the lidocaine group over the same time period. Thus, about 400 patients would currently need prophylaxis with lidocaine to prevent one episode of VF.

CONCLUSIONS

Present estimates of the risk:benefit ratio of lidocaine prophylaxis should consider the low risk of VF in control patients and the large number who need lidocaine prophylaxis to prevent one episode of VF. When added to the previously reported trend toward excess mortality in lidocaine-treated patients, these data argue against the routine prophylactic use of lidocaine in patients with acute myocardial infarction.

Prognosis of late versus early ventricular fibrillation in acute myocardial infarction

To determine the prognosis of late ventricular fibrillation (VF) after acute myocardial infarction (AMI), the length of the monitoring period after AMI was extended. All patients in this series were continuously monitored in a coronary care unit to ensure observation of all VF within 18 days of AMI. From 1977 to 1985, 4,269 patients were admitted with AMI and 413 (9.6%) had in-hospital VF. Of these 281 (6.8%) had early VF (less than 48 hours after AMI) and 132 (3.2%) had late VF (greater than or equal to 48 hours after AMI). In-hospital mortality was 50 and 54% for early and late VF, respectively (p = 0.31). Kaplan-Meier survival analysis showed better survival after discharge for patients with early versus late VF (p = 0.009) but this difference was fully explained by the presence of heart failure. Survival analysis showed the same prognosis after 1, 3 and 5 years for early and late VF, when VF was not associated with heart failure. When VF was associated with heart failure (secondary VF) early VF had a greater mortality than late VF after 2 and 5 years. Logistic regression analysis showed that heart failure (relative risk 1.9 [1.1 to 3.1]) and cardiogenic shock (relative risk 3.9 [1.8 to 8.5]) were significant risk factors for in-hospital death. Late VF compared to early VF had no prognostic implication (relative risk 1.0 [0.6 to 1.6]). For patients discharged from the hospital, risk factors were heart failure (1.8 [1.1 to 2.8]) and previous AMI (1.6 [1.3 to 2.1]).(ABSTRACT TRUNCATED AT 250 WORDS)