Relation between acute ventricular arrhythmias, ventricular late potentials and mortality in acute myocardial infarction

Electrocardiographic Markers of Reperfusion in ST-elevation Myocardial Infarction

The outcome of patients who fail to reperfuse with thrombolytic therapy or percutaneous coronary intervention (PCI) for ST-elevation acute myocardial infarction (STEMI) may be improved with additional pharmacologic and mechanical interventions such as rescue PCI or intravenous glycoprotein IIb/IIIa infusion. The standard 12-lead ECG is the most commonly available and suitable tool for routine bedside evaluation of the success of reperfusion therapy for STEMI. This article reviews and discusses the current data on the four ECG markers for prediction of the perfusion status of the ischemic myocardium: ST-segment deviation, T-wave configuration, QRS changes, and reperfusion arrhythmias.

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

Long-term prognostic significance of ventricular late potentials after a first acute myocardial infarction

Ventricular late potentials (VLP) have been shown to be independent predictors of arrhythmic events after myocardial infarction. However, many studies have had one or more limitations: limited follow-up period, small study group, possible selection bias, inadequate statistical analysis, or inclusion of patients with previous infarction. The purpose of this study was to assess the long-term prognostic value of VLP in a large group of unselected patients after a first acute myocardial infarction. Time-domain signal averaging was performed in 458 patients (380 male, 78 female, mean age 59 +/- 11 years) a mean of 10 days (range 7 to 13 days) after a first acute myocardial infarction. The overall prevalence of VLP was 20% (90 of 458 patients). By univariate analysis a left ventricular ejection fraction <40% (p = 0.002) and the presence of an occluded infarct-related artery (p = 0.006) were the only statistically significant predictors for the development of VLP. During a median follow-up of 70 months, 21 (5%) patients died suddenly, and 11 (2%) patients had documented sustained ventricular tachycardia. The presence of VLP (p < 0.0001), older age (p = 0.02), and an occluded infarct-related artery (p = 0.045) were the only variables significantly associated with the occurrence of serious arrhythmic events during follow-up. The probability of having no arrhythmic events was 99% at 1 year and 96% at 5 years in the absence of VLP and 87% at 1 year and 80% at 5 years in the presence of VLP (4.6-fold increase in arrhythmic risk; 95% confidence interval: 2.3 to 9.1). VLPs are powerful predictors of serious arrhythmic events in patients after a first acute myocardial infarction, and their prognostic value, although waning with time, persists for at least 7 years. This study also provides further evidence that an open infarct-related artery may reduce the arrhythmic risk after myocardial infarction.

Use of signal-averaged electrocardiography for predicting inducible sustained monomorphic ventricular tachycardia in patients with bundle branch block with and without a history of syncope

The aim of this study was to examine the utility of signal-averaged electrocardiography in relation to inducible sustained monomorphic ventricular tachycardia in patients with bundle branch block. One hundred fourteen patients with bundle branch block underwent signal-averaged electrocardiography in the time domain and programmed ventricular stimulation. Sustained monomorphic ventricular tachycardia was induced in 17 patients. The mean values of the three signal-averaged electrocardiographic variables analyzed differed significantly between the inducible and the noninducible group. The filtered QRS duration showed the most prominent difference between the two groups, and a filtered QRS duration > or = 155 msec had a sensitivity of approximately 80%, a specificity of 60%, and a total predictive value of 65%. In the subgroup of patients with syncope, a combination of these criteria with a history of coronary artery disease had a sensitivity of 100% and a specificity of 90%.

Usefulness of late potentials on the immediate postoperative signal-averaged electrocardiogram in predicting ventricular tachyarrhythmias early after isolated coronary artery bypass grafting

The present study was undertaken to determine the value of abnormal late ventricular potentials on signal-averaged electrocardiograms (ECG) in identifying patients at risk of developing ventricular tachycardia or ventricular fibrillation in the early postoperative period after coronary artery bypass grafting. Signal-averaged ECGs were recorded immediately after operation in 72 patients. Abnormal late potentials were defined as the presence of 2 or 3 of the following: (1) root-mean-square amplitude of the last 40 ms of the QRS < 20 microV; (2) duration of the terminal QRS potentials (after 40 microV) > or = 39 ms; and (3) high-frequency QRS duration > 120 ms (in patients with conduction defects, only the first 2 criteria were used). Abnormal late ventricular potentials were present on the immediate postoperative signal-averaged ECG in 26 of the 72 patients (36%). Life-threatening ventricular tachyarrhythmias occurred in 6 patients. Late potentials were present in all 6 patients, but only in 20 of 66 (30%) who did not develop ventricular tachyarrhythmias (p < 0.005) (sensitivity 100%, specificity 70%, predictive accuracy 72%). Of 12 pre- and perioperative variables examined by univariate and multivariate regression analysis, the presence of late potentials on the signal-averaged ECG and low cardiac output postoperatively were found to be independent predictors of life-threatening tachyarrhythmias.