Ventricular fibrillation markers on admission to the hospital for acute myocardial infarction

Ventricular muscarinic receptor remodeling in patients with and without primary ventricular fibrillation. An imaging study

BACKGROUND

Vagal innervation modulates the electrical stability of the left ventricle (LV) during ischemia. Thus, abnormal parasympathetic activity in myocardial infarction (MI) patients with primary ventricular fibrillation (FV) can account for their arrhythmic disorders. We evaluated LV muscarinic receptor density (B (max)) after MI in patients with (FV(G), n = 11) or without (nFV(G), n = 12) primary FV.

METHODS AND RESULTS

The B (max) was measured by positron emission tomography and the specific antagonist [(11)C]methylquinuclidinyl benzilate ([(11)C]MQNB) in 23 patients 39 ± 19 days post-MI, and 10 volunteers. Myocardial damage was quantified by delayed contrast-enhanced magnetic resonance imaging. Three short-axis slices per subject were analyzed and six time-activity curves per slice were fitted to a 3-compartment ligand-receptor model. The B (max) in remote regions of the 23 patients (67 ± 36 pmol/mL · tissue; n = 139) was higher than in normal regions of volunteers (33 ± 16 pmol/mL · tissue; n = 171; P = .01). Receptor density in remote regions was similarly upregulated in nFV(G) (69 ± 31 pmol/mL · tissue, n = 73) and FV(G) (66 ± 40 pmol/mL · tissue, n = 66; P = .72). In damaged regions, the B (max) was reduced in both patient groups (44 pmol/mL · tissue).

CONCLUSIONS

Chronically infarcted patients with or without primary FV share similar patterns of ventricular muscarinic receptor remodeling, characterized by receptor upregulation, in remote non-damaged territories.

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.

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.