Ventricular fibrillation following administration of thrombolytic treatment. The EMIP experience. European Myocardial Infarction Project

Ischemic QRS prolongation as a predictor of ventricular fibrillation in a canine model

OBJECTIVES

An acute coronary occlusion and its possible subsequent complications is one of the most common causes of death. One such complication is ventricular fibrillation (VF) due to myocardial ischemia. The severity of ischemia is related to the amount of coronary arterial collateral flow. In dog studies collateral flow has also been shown to be associated with QRS prolongation. The aim of this study was to investigate whether ischemic QRS prolongation (IQP) is associated with impending VF in an experimental acute ischemia dog model.

METHODS

Degree of IQP and occurrence of VF were measured in dogs (n = 21) during coronary occlusion for 15 min and also during subsequent reperfusion (experiments conducted in 1984).

RESULTS

There was a significant difference in absolute IQP between dogs which developed VF during reperfusion (47 ± 29 ms, mean ± SD) and those which did not (12 ± 10 ms; p = .001).

CONCLUSIONS

IQP during acute coronary occlusion is associated with reperfusion VF in an experimental dog model and might therefore be a potential predictor of malignant arrhythmias in patients with acute coronary syndrome.

Location of acute myocardial infarction and associated arrhythmias and outcome

BACKGROUND

Cardiac arrhythmias and conduction abnormalities complicating acute myocardial infarction (AMI) have been associated with adverse prognosis in numerous reports. Small studies have frequently associated different arrhythmias with various distributions of myocardial infarctions. We analyzed a nationally representative hospital discharge database to evaluate the relationship between the location of AMI and the associated arrhythmias and conduction abnormalities and their impact on in-hospital mortality.

METHODS

We searched the National Hospital Discharge Survey database for patients with a diagnosis of AMI and collected data on the associated arrhythmias and conduction abnormalities. In-hospital death was used as end point for analysis.

RESULTS

A total of 21,807 patients, representing 2,632,217 hospital discharges in the United States, with a primary diagnosis of AMI from 1996 to 2003 were included in this analysis. Patients with inferior or posterior AMI were more likely to develop complete heart block compared to those with anterior or lateral AMI (3.7% vs 1.0%, hazard ratio [HR] = 3.9, p <or= 0.001), but less likely to die prior to hospital discharge (7.7% vs 11.3%, HR = 0.65, p <or= 0.001).

CONCLUSIONS

Patients with an inferior or posterior AMI are more likely to develop conduction system abnormalities when compared to patients with an anterior or lateral AMI. On the other hand, anterior or lateral MI is a significant predictor of in-hospital death.

Ventricular fibrillation in acute myocardial infarction before and during primary PCI

BACKGROUND

There are scarce and sometimes contradictory data about ventricular fibrillation (VF) during the acute phase of MI. In-hospital VF most often occurs with inferior MI, when treated with fibrinolytics. Out-of-hospital VF seems to be associated with anterior MI. We studied characteristics of patients with VF during reperfusion therapy by primary angioplasty (PCI) versus patients with VF before PCI.

METHODS

From January 1995 until December 2001, we treated 2826 patients for acute MI and reviewed clinical records of all patients who developed VF and classified the patients according to the first episode of VF: either before or during the angioplasty procedure.

RESULTS

VF developed in 219 (8%) patients. Patients with VF during reperfusion therapy (n=74, 3%) were older (p=0.03), more frequently female (0.04), less often had heart failure (p=0.04), when compared with patient with VF before PCI (n=145, 5%). Patients with VF during PCI experienced more often preinfarction angina (p=0.009) and suffered more often from inferior MI (p=0.001), when compared with patients with VF before PCI.

CONCLUSIONS

Patients with early VF before reperfusion have different characteristics when compared with patients with VF during reperfusion. Infarct location is a major determinant of timing of VF, when both groups are compared (p<0.001).

Prevention of primary ventricular fibrillation in acute myocardial infarction with prophylactic lidocaine

Primary ventricular fibrillation (VF) during an acute myocardial infarction (AMI) occurs with a high incidence and mortality rate with or without thrombolysis. The incidence varies from 2% to 19% depending on the definition of "primary." Primary VF in this study refers to fibrillation occurring in the absence of shock or pulmonary edema. Mortality rate, when primary VF occurs, is 2 to 4 times greater than when it does not. Prevention of VF has been impeded by the publication of the 1996 recommendations of the American Heart Association and American College of Cardiology against the use of prophylactic lidocaine based on meta-analysis studies implying toxicity. This observational study of 4,254 patients with AMI reports the incidence and mortality rates of primary VF over 32 years. Of the 4,254 patients, 4,150 received prophylactic lidocaine, and 104 patients did not receive prophylactic lidocaine due to the 1996 guidelines, after which administration of prophylactic lidocaine was governed by physician choice. The incidence of primary VF was 0.5% among the 4,150 who received prophylactic lidocaine and 10% among the 104 who did not (p <0.0001). Among the 4,150 receiving prophylactic lidocaine, sinoatrial block occurred in 0.5% and complete infranodal atrial ventricular block occurred in 0.2%, all secondary to the site of infarction (concurrent serum lidocaine levels were < 4 microg/ml). Asystole was an agonal rhythm in 4%; these patients had been off lidocaine for 48 hours. Mortality rates were 10.5% in patients without primary VF and 25% in patients with VF (p <0.001). Thus, prophylactic lidocaine markedly decreased the incidence of VF in 4,150 patients with AMI to 0.5% compared with trials before and after thrombolysis (2% to 19%) and with the 104 patients in this study who did not receive prophylactic lidocaine (10%). No lidocaine-induced sinoatrial or atrial ventricular block or asystole occurred.

Arrhrythmias and haemodynamic effects associated with early versus late prehospital thrombolysis for acute myocardial infarction

The occurrence of arrhythmias and haemodynamic changes was studied prospectively in 226 consecutive patients who received prehospital thrombolysis for acute ST-elevation myocardial infarction (STEMI) in two Helicopter Emergency Medical Service (HEMS) systems in Southern Finland. Of the 226 patients, 129 were classified as receiving early (pain to treatment-time <90 min) and 97 as late (pain to treatment-time >90 min) treatment. Data on all arrhythmias and haemodynamic disturbances during the prehospital phase were collected. Arrhythmias occurred in 39% of all patients (40% in the early and 38% in the late group). A third of the patients received treatment for their arrhythmia (38% in the early group and 24% in the late group, P = NS). The most common arrhythmia was ventricular extrasystoles, which did not require any treatment in the majority of patients. On arrival of the EMS crew, 14% of all patients were hypotensive (14% in the early and 13% in the late group). After thrombolytic treatment, 7% of all patients became hypotensive (7% of the patients in both groups). The most common treatment for hypotension was fluid administration. Of the 15 patients who received thrombolysis after cardiopulmonary resuscitation (CPR), four patients suffered from arrhythmias and six patients developed hypotension after initiation of thrombolytic treatment. Although arrhythmias and haemodynamic changes were frequent in the prehospital setting after initiation of thrombolytic therapy, severe adverse events were rare. Those requiring therapeutic measures responded well to treatment. The occurrence of events was not related to the timing of thrombolysis in relation to the duration of pain.

Mitochondrial gene expression and ventricular fibrillation in ischemic/reperfused nondiabetic and diabetic myocardium

We investigated the mitochondrial gene expression related to cardiac function and ventricular fibrillation (VF) in ischemic/reperfused nondiabetic and diabetic myocardium. To identify potentially more specific gene responses we performed subtractive screening, Northern blotting, and reverse transcription-polymerase chain reaction (RT-PCR) of mitochondrial genes expressed after 30 min ischemia followed by 120 min reperfusion in isolated rat hearts that showed VF or did not show VF. Cytochrome oxidase B subunit III (COXBIII) and ATP synthase subunit 6, studied and selected out of 40 mitochondrial genes by subtractive screening, showed an expression after 30 min ischemia (no VF was recorded) in both nondiabetic and diabetic subjects. Upon reperfusion, the down-regulation of these genes was only observed in fibrillated hearts. Such a reduction in signal intensity was not seen in nonfibrillated myocardium. In additional studies, nondiabetic and diabetic hearts, without the ischemia/reperfusion protocol, were subjected to electrical fibrillation, and a significant reduction in COXBIII and ATPS6 mRNA signal intensity was observed indicating that VF contributes to the down-regulation of these genes. Cardiac function (heart rate, coronary flow, aortic flow, left ventricular developed pressure) showed no correlation between the up- and down-regulation of these mitochondrial genes in both nondiabetic and diabetic ischemic/reperfused myocardium. Our data suggest that COXBIII and ATPS6 may play a critical role in arrhythmogenesis, and the stimulation of COXBIII and ATPS6 mRNA expression may prevent the development of VF in both nondiabetic and diabetic ischemic/reperfused myocardium.

Prophylactic lidocaine use in acute myocardial infarction: incidence and outcomes from two international trials. The GUSTO-I and GUSTO-IIb Investigators

BACKGROUND

Early meta-analyses suggested that prophylactic lidocaine use reduces ventricular fibrillation but increases mortality rates after acute myocardial infarction. We determined the frequency and effect on clinical outcomes with its use in the thrombolytic era.

METHODS AND RESULTS

We studied 43,704 patients enrolled in GUSTO-I or GUSTO-IIb who had ST-segment elevation, underwent thrombolysis, and survived at least 1 hour after enrollment. Odds ratios (OR) and confidence intervals (CI) were calculated for the risk of asystole, atrioventricular block, ventricular fibrillation, and ventricular tachycardia during hospitalization; for 24-hour, in-hospital, and 30-day mortality rates; and for 24-hour and 30-day mortality rates after adjustment for baseline predictors of death. In GUSTO-I and GUSTO-IIb, 16% and 3.5% of patients, respectively, received prophylactic lidocaine. They had a lower risk of death at 24 hours (OR 0.81, 95% CI 0.67 to 0.97) and trends toward lower odds of in-hospital death (OR 0.90, 95% CI 0.81 to 1.01) and death at 30 days (OR 0.92, 95% CI 0.82 to 1. 02). After adjustment for baseline characteristics, however, the odds of death were similar with or without lidocaine (OR 0.90 and 0. 97, respectively). Outside the United States, lidocaine was associated with higher incidences of all serious arrhythmias, but in US patients it conferred a lower likelihood of ventricular fibrillation and no increase in asystole, atrioventricular block, or mortality rates.

CONCLUSIONS

Prophylactic lidocaine use has decreased with the advent of thrombolysis, although its use may not be associated with increased mortality rates.

Pre-hospital thrombolysis

The administration of thrombolytic drugs outside hospital by emergency physicians is becoming more common. However, few in Europe live in areas where such a service is provided. The data suggest that the advantages can be appreciable in some circumstances but that the strategy may not be universally applicable.

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.

Thrombolysis in acute myocardial infarction improves prognosis and prolongs life but will increase the prevalence of heart failure in the geriatric population

This paper will review the hypothesis that early complete thrombolytic therapy in acute myocardial infarction reduces mortality and improves prognosis. ACE inhibitors improve remodelling and anti-platelet drugs or interventional procedures prevent reocclusion of the infarct related coronary artery. Most patients are left with significant myocardial damage and this effect is cumulative with subsequent infarction. The average age of death has increased by 10 years in the last three decades, so that many older patients survive. They have survived acute myocardial infarction and we now have a significant population with important heart failure despite good thrombolytic therapy.