Implications of the ESVEM trial for use of antiarrhythmic drugs that prolong cardiac repolarization

Predictive factors of ventricular fibrillation triggered by pause-dependent torsades de pointes associated with acquired long QT interval: role of QT dispersion and left ventricular function

INTRODUCTION

Death due to acquired torsades de pointes usually is caused by ventricular fibrillation (VF), but the contributing factors to VF triggered by pause-dependent torsades de pointes are not understood.

METHODS AND RESULTS

We evaluated 91 patients who fulfilled four criteria: (1) pause-dependent torsades de pointes; (2) prolonged QT interval and/or corrected QT (QTc) (>0.44 sec); (3) long-short initiation sequence; and (4) conditions known to induce pause-dependent torsades de pointes. There were 38 patients with a documented VF (group I) and 53 without VF (group II). Absolute and relative dispersions of QT and QTc were calculated based on the 12-lead standard ECG. Group I differed from group II with regard to myocardial infarction history (32% vs 13%; P = 0.035), left ventricular ejection fraction (44% +/- 14% vs 65% +/- 9%; P < 0.0001), presence of structural heart disease (100% vs 20.8%; P < 0.0001), QT mean (591 +/- 73 msec vs 514 +/- 78 msec; P < 0.0001), QTc mean (563 +/- 76 msec vs 508 +/- 90 msec; P = 0.002), absolute QT dispersion (166 +/- 56 msec vs 84 +/- 49 msec; P < 0.0001), relative QT dispersion (9.9% +/- 3.5% vs 6.3% +/- 3.2%; P < 0.0001), absolute QTc dispersion (158 +/- 57 msec vs 81 +/- 44 msec; P < 0.0001), and relative QTc dispersion (9.9% +/- 3.6% vs 6.2% +/- 3%; P < 0.0001). Multiple regression analysis showed that ejection fraction (P = 0.0001), presence of structural heart disease (P < 0.0001), and relative QTc dispersion (P = 0.038) were the only independent predictors of VF.

CONCLUSION

Left ventricular function, presence of structural heart disease, and QTc relative dispersion should be evaluated carefully in patients with conditions susceptible to inducing torsades de pointes.

Compared effects of sotalol, flecainide and propafenone on ventricular repolarization in patients free of underlying structural heart disease

Antiarrhythmic drugs are known to affect the depolarization and repolarization time in a different fashion. The aim of the present study was to compare the effects of Sotalol, Flecainide and Propafenone on some common (QT, QTc, JT, JTc) or uncommon (QTc dispersion, T-peak to T-end interval) electrocardiographic parameters in order to evaluate the effects of these antiarrhythmic drugs on ventricular repolarization time both in terms of absolute values and of dispersion across the myocardium. The analysis of these antiarrhythmic drug effects was performed on the standard 12-lead electrocardiograms of 31 patients (17F and 14M, age 38.1+/-17 years, range 11-67 years) in the free-drug state and at the steady state after oral treatment with Sotalol (160 mg daily), Flecainide (200 mg daily) and Propafenone (450 mg daily). These drugs were prescribed, separately, to all the 31 patients, free of underlying structural heart disease, for the treatment of their atrio-ventricular nodal re-entry tachycardia. Data of the present study show that Sotalol, over the range prescribed, significantly prolongs ventricular repolarization index QT (P=0.001), JT (P=0.0001) and JTc (P=0.0001) values in an homogeneous fashion, as shown by the significant decrease in QTcD (P=0.019) and Tp-Te (P=0.01). On the contrary, Flecainide treatment was associated with an increase in QTcD (P=0.029), Tp-Te (0.0001), QT (P=0.001), QTc (P=0.0001) and QRS (P=0.0001), with no significant changes in JT and JTc. Propafenone, over the range prescribed, did not affect repolarization time, resulting only in a prolongation of depolarization time as expressed by the increase of QRS (P=0.0001).

The usefulness of Holter monitoring in selecting pharmacologic therapy for patients with sustained monomorphic ventricular tachycardia: studies in patients in whom no effective pharmacologic therapy could be determined by electrophysiologic study

The usefulness of Holter monitoring (HM) in selecting pharmacologic therapy for patients with sustained monomorphic ventricular tachycardia (VT) was evaluated in patients in whom no effective pharmacologic therapy could be determined in an electrophysiologic study (EPS). The study population consisted of 49 consecutive patients with sustained VT who were receiving long-term pharmacologic therapy despite the fact that no pharmacologic therapy had been found to be effective in the EPS. The efficacy of the pharmacologic therapies was assessed by HM. A reduction in frequent (10/h) premature ventricular contractions (PVCs) was used as an index of treatment efficacy, with therapies achieving substantial PVC suppression (>70% of all PVCs) being considered to be effective (HM effective group). When no therapy was found to be effective when assessed by HM, a drug with any other beneficial effect, eg, reduction in VT rate, was chosen (HM ineffective group). VT recurrence and survival were compared between groups. During the follow-up period of 31+/-28 months, VT recurrence was observed in a total of 25/49 patients: 3/17 patients in the HM effective group, in 18/25 in the HM ineffective group, and in 4/7 in the HM undetermined group (p=0.0487). Sudden cardiac death occurred in a total 7/49 patients: 2/17 patients in the HM effective group, 4/25 patients in the HM ineffective group, and 1/7 patient in the HM undetermined group (p=0.2828). Among patients in whom no effective therapy could be determined by EPS, the VT recurrence rate was significantly lower in the group in whom treatment was effective as assessed by HM than among those in whom treatment was assessed by HM to be ineffective. Sudden cardiac death rate was also lowest in the HM effective group, although the difference was not statistically significant. HM assessment was considered useful in selection of pharmacologic therapy for patients in whom no effective therapy could be determined in the EPS.

A summary and assessment of the findings and conclusions of the ESVEM trial

The Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial was completed in 1992 and the primary results were reported in 1993. Since then, considerable discussion about this trial has taken place and new trial results have been reported. Trial analysis has yielded seven principal findings to date concerning treatment of patients with ventricular tachyarrhythmias, ie: (1) similar accuracy of electrophysiologic study (EPS), Holter monitoring (HM), and EPS combined with HM for predicting antiarrhythmic drug efficacy; (2) greater efficiency and lower cost of HM; (3) improved survival associated with predicted drug efficacy; (4) predictors of response to EPS and HM; (5) greater efficacy and lower cost of therapy with sotalol compared with drugs with class-l effects; (6) lack of a relationship between presenting and recurring arrhythmia; and (7) preponderance of nonarrhythmic deaths in trial participants. A number of additional specific findings of the trial are reviewed in this symposium. Several criticisms of the trial's enrollment, methods, and efficacy criteria are reviewed and discussed. Some criticisms are valid. Many are related to misunderstandings of ESVEM trial methodology and to bias of the individual critics. Some are simply incorrect. The importance of the ESVEM trial in the present day may be limited by the growing use of implanted devices rather than drugs for treatment of ventricular tachyarrhythmias. If clinical trials ultimately prove devices to be no more effective than drugs, the findings of the ESVEM investigators will grow in importance.