Predictor Of Arrhythmic Events Research Articles

Assessment of QT dispersion in symptomatic patients with congenital long QT syndromes

It has been suggested that QT dispersion recorded on the surface electrocardiogram may be a predictor of arrhythmic events in patients with congenital QT prolongation. To evaluate this, 9 patients (6 female, mean age 17.6 years) with congenital long QT syndromes, all of whom had syncope and documented torsades de pointes, were studied. Patients were studied off treatment and during therapy with β-blocking agents. Three patients were also studied after left stellate ganglionectomy. An age-matched control group was also studied. Good quality 12-lead electrocardiograms were recorded from all patients. For each lead, QT and RR intervals were measured, and QTc value was calculated. QT and QTc dispersions were calculated for each patient. Patients had a significantly longer mean QT interval compared with that of the control group (450 ± 100 vs 359 ± 63 ms; p = 0.015) at similar mean RR intervals (736 ± 231 vs 783 ± 289 ms), with a longer mean QTc value (0.53 ± 0.08 vs 0.41 ± 0.02 s 1 2 ; p = 0.004). Patients also had longer QT and QTc dispersions compared with those of the control group (110 ± 45 vs 43 ± 12 ms [p = 0.004], and 0.108 ± 0.03 vs 0.05 ± 0.02 s 1 2 [p = 0.002], respectively). QT and QTc dispersions on and off β-blocking agents were not significantly different. Comparing patients with frequent and those with infrequent symptoms, there was no difference in QT or QTc dispersion either off treatment or during therapy with β-blocking agents. There was an increase in mean QT interval and QTc value in patients with frequent symptoms on β-blocking agents. On β-blocking agents, patients with frequent symptoms had a significantly longer mean QTc value compared with that of those with infrequent symptoms. There was no change in QT or QTc dispersion, mean QT or RR interval, or mean QTc value after left stellate ganglionectomy. QT-interval dispersion is observed in patients with congenital long QT syndromes; however, the degree of dispersion is not related to the severity of symptoms, nor influenced by treatment with β-blocking agents.

Risk stratification for arrhythmic events in postinfarction patients based on heart rate variability, ambulatory electrocardiographic variables and the signal-averaged electrocardiogram

The value of heart rate variability, ambulatory electrocardiographic (ECG) variables and the signal-averaged ECG in the prediction of arrhythmic events (sudden death or life-threatening ventricular arrhythmias) was assessed before hospital discharge in 416 consecutive survivors of acute myocardial infarction. During the follow-up period (range 1 to 1,112 days), there were 24 arrhythmic events and 47 deaths. The initial relation between several prognostic factors and arrhythmic events was explored with use of the Kaplan-Meier product limit estimates of survival function.Impaired heart rate variability <20 ms (p < 0.0000), late potentials (p < 0.0000), ventricular ectopic beat frequency (p < 0.0000), repetitive ventricular forms (p < 0.0000), left ventricular ejection fraction <40% (p < 0.02) and Killip class (p < 0.02) were identified as significant univariate predictors of arrhythmic events. When these variables were analyzed by using a stepwise Cox regression model, only impaired heart rate variability, followed by late potentials and repetitive ventricular forms remained independent predictors of arrhythmic events. The combination of impaired heart rate variability and late potentials had a sensitivity of 58%, a positive predictive accuracy of 33% and a relative risk of 18.5 for arrhythmic events and was superior to other combinations including those incorporating left ventricular function, exercise ECG, ventricular ectopic beat frequency and repetitive ventricular forms.These results suggest that a simple method of assessment based on heart rate variability and the signal-averaged ECG can select a small subgroup of survivors of myocardial infarction at high risk of future life-threatening arrhythmias and sudden death.

Prediction of arrhythmic events in patients following myocardial infarction.

The value of techniques used to predict arrhythmic events (sudden cardiac death not preceded by reinfarction and spontaneous sustained ventricular tachycardia) after acute myocardial infarction is reviewed. A full clinical assessment allows the detection of patients with major infarction, present in the majority of those suffering arrhythmic events during follow-up. More sophisticated noninvasive tests, including Holter monitoring, and the high gain, signal averaged ECG, add prognostic accuracy to clinical assessment in patients with major infarction but are by themselves nonspecific. Noninvasive assessment of autonomic function from baroreceptor sensitivity analysis and heart rate variability measurement may also provide useful prognostic information. The results of programmed ventricular stimulation studies in patients with recent acute infarction have been contradictory, though many of the disagreements can be explained by methodological differences. At best this technique is highly invasive, and probably adds little to what can be discovered from a thorough noninvasive assessment. The treatment to be adopted in those judged to be at high risk remains to be established, and this may include nonpharmacological modalities such as the implantable defibrillator and surgical ablation as alternatives to drug therapy.

Prognostic Significance and Evolution of Late Ventricular Potentials in the First Year After Myocardial Infarction: A Prospective Study

We performed a prospective study of the high-frequency components of the terminal portion of the QRS complex in 220 patients who survived acute myocardial infarction. Signal-averaged electrocardiograms (SA-ECGs) were performed before hospital discharge (16 +/- 6 days) and then serially at regular intervals over the following year. SA-ECGs were processed using a 40 Hz high-pass bidirectional filter. Duration of "filtered" QRS (D-normal value less than 120 ms), duration of the low-amplitude signals (D40 - n.v. less than 39 ms) and last 40 ms voltage of the QRS complex (V40 - n.v. greater than 20 microV) were measured. Late potentials (LPs) were defined as the presence of two or more abnormal values. In addition, 24-hour Holter monitoring was performed in 208 patients and left ventricular ejection fraction (LVEF) was determined by scintigraphy in 111. Sixty-two patients (group 1) had LPs, 158 had normal SA-ECGs (group 2). Spontaneous normalization of SA-ECGs occurred in 20% of patients after 6 months, although the mean values of D, D40 and V40 did not change significantly and the reproducibility was very good for all the indexes during all the follow-up controls. Three patients had sudden death and three presented again with spontaneous, sustained ventricular tachycardia. Five of 62 (8%) group 1 patients had an arrhythmic event compared with one of 158 patients (0.6%) in group 2. The sensitivity of SA-ECGs as a predictor of arrhythmic events was 83% with a specificity of 73%. Patients with subsequent arrhythmic events had longer filtered QRS (133 +/- 19 vs 104 +/- 16 ms; P less than 0.001), longer duration of the low-amplitude signals (54 +/- 15 vs 33 +/- 14 ms; P less than 0.01), and lower voltages in the last 40 ms of the filtered QRS (11 +/- 3 vs 36 +/- 25 microV; P less than 0.02) and, moreover, higher peak CK values and lower LVEF than those without such events. In conclusion, SA-ECGs provide important prognostic information in identifying patients at risk of arrhythmic events after myocardial infarction although dynamic changes of LPs are observed during the first year after myocardial infarction.