[Sudden death (II). Myocardial ischemia and ventricular arrhythmias in experimental models: triggering mechanisms]

QRS duration and dispersion for predicting ventricular arrhythmias in early stage of acute myocardial infraction

OBJECTIVE

To determine the relationship between QRS duration and dispersion and the occurrence of ventricular arrhythmias in early stages of acute myocardial infarction (AMI).

DESIGN

A retrospective, longitudinal descriptive study was carried out.

SETTING

Hospital General Universitario "Camilo Cienfuegos", Sancti Spíritus, Cuba. Secondary health care.

PATIENTS OR PARTICIPANTS

A total of 209 patients diagnosed with ST-segment elevation AMI from January 2012 to June 2014.

MAIN VARIABLES OF INTEREST

The duration and dispersion of the QT interval, corrected QT interval, and QRS complex were measured in the first electrocardiogram performed at the hospital. The presence of ventricular tachycardia/fibrillation was assessed during follow-up (length of hospital stay).

RESULTS

Arrhythmias were found in 46 patients (22%); in 25 of them (15.9%), arrhythmias originated in ventricles, and were more common in those subjects with extensive anterior wall AMI, which was responsible for 81.8% of the ventricular fibrillations and more than half (57.1%) of the ventricular tachycardias. The widest QRS complexes (77.3±13.3 vs. 71.5±6.4ms; P=.029) and their greatest dispersion (24.1±16.2 vs. 16.5±4.8ms; P=.019) were found on those leads that explore the regions affected by ischemia. The highest values of all measurements were found in extensive anterior wall AMI, with significant differences: QRS 92.3±18.8ms, QRS dispersion 37.9±23.9ms, corrected QT 518.5±72.2ms, and corrected QT interval dispersion 94.9±26.8ms. Patients with higher QRS dispersion values were more likely to have ventricular arrhythmias, with cutoff points at 23.5ms and 24.5ms for tachycardia and ventricular fibrillation, respectively.

CONCLUSIONS

Increased QRS duration and dispersion implied a greater likelihood of ventricular arrhythmias in early stages of AMI than increased duration and dispersion of the corrected QT interval.

Sustained ventricular tachycardia as a marker of inadequate myocardial perfusion during the acute phase of myocardial infarction

BACKGROUND

Sustained ventricular tachycardia (VT) complicating the acute phase of myocardial infarction (AMI) is a quite rare event but with short-term unfavorable prognosis. The clinical characteristics as well as the therapeutic implications have not yet been well defined.

HYPOTHESIS

This paper attempts to prove that VT may be considered a marker of inadequate myocardial perfusion after thrombolysis.

METHODS

To assess the clinic-electroangiographic characteristics and prognosis of patients with VT occurring within the first 4 days of an AMI, a case-control study was carried out in 23 patients from a total of 1,100 patients (1.9%) hospitalized with AMI between March 1993 and July 1997. These patients were compared with a control group of 131 patients hospitalized consecutively. A statistical analysis was made using the chi-square test, t-test, and logistic regression.

RESULTS

There were no differences among groups with regard to age, gender, and area of necrosis. Average time for the onset of VT was 26 h (range 0-92 h). Sixteen patients underwent coronary angiography: 4 patients had left main coronary artery disease, 2 had single-vessel disease, 8 had lesions in two vessels, and 2 had triple-vessel disease. Univariate analysis showed that patients with VT had a higher incidence of creatine phosphokinase (CPK)-MB peak > 300 UI/l (61 vs. 30%; p<0.001), more frequent occurrence of previous AMI (48 vs. 17%; p<0.001), and acute intraventricular conduction disorders (26 vs. 4%; p<0.001). Furthermore, these patients suffered ischemia previous to VT more frequently (65 vs. 11%; p<0.0001), and had a greater mortality rate than that in the control group (35 vs. 4%; p<0.0001). In the multivariant analysis, the variables related to the occurrence of VT were CPK-MB peak > 300 IU/l (OR 5.9; 95% CI 1.6-21), acute intraventricular conduction disorders (OR 9.02; 95% CI 1.7-48), and ischemia immediately prior to VT (odds ratio [OR] 19.64; 95% confidence interval [CI] 5.3-73).

CONCLUSIONS

Ventricular tachycardia may be considered a marker of inadequate myocardial perfusion after thrombolysis; therefore, a more aggressive revascularization treatment in these patients would be advisable. The profile of patients with AMI, hospitalized in the coronary care unit, who will likely suffer from VT is previous AMI, CPK-MB peak > 300, acute intraventricular conduction disorders, Killip > I, and ischemia previous to VT.

[ST-segment and myocardial enzymes evolution during myocardial infarction after fibrinolysis therapy and its relation with postinfarction angina, Killip class and mortality in intensive unit care]

INTRODUCTION

The prognostic value of enzyme peaks, the sum of the ST segment and reperfusion arrythmias during myocardial infarction remains unclear.

AIM

The aim of this study was to relate the early enzymatic peaks, the sum of the ST segment and reperfusion arrythmias after thrombolytic therapy with postinfarction angina, Killip class and mortality during the acute phase of myocardial infarction.

PATIENTS AND METHODS

Of 187 patients receiving fibrinolytic therapy, 169 were consecutively and prospectively included in the study. The following myocardial enzymes were determined: CK, MB, TGO, LDH. Electrocardiograms were performed prior to and 2, 6, 12 and 24 hours after the administration of the fibrinolytic drug.

RESULTS

The mean age of the patients was 60.12 +/- 11.3 years, with 138 (81.7%) being males. Myocardial infarction was anterior in 74 (43.7%) and inferior in 95 cases (56.3%). Reperfusion arrythmias were observed in 65 cases (38.5%). One hundred thirty-one (77.5%) were Killip class I, 12 (7.1%) presented postinfarction angina, and 8 (4.7%) died. A peak was observed in MB at 6 hours in cases of anterior myocardial infarction and the sum of the ST segment decreased less than 50% in the first 2 hours. No statistically significant correlation was observed between the enzymatic peaks, the reperfusion arrythmias, Killip class, postinfarction angina or early mortality. The greater the ST segment sum, the greater the severity according to the Killip class. On multivariate analysis no model was found to be related to postinfarction angina. However, age was related to mortality and sex and age were associated with heart failure.

CONCLUSIONS

In our population, the variables studied were not found to be useful to determine the prognosis during the early phase of acute myocardial infarction.