Comparison of the characteristics of nonsustained ventricular tachycardia on Holter monitoring and sustained ventricular tachycardia observed spontaneously or induced by programmed stimulation

QRS morphologies of the surface ECG of nonsustained ventricular tachycardias during holter monitoring compared with QRS morphologies of spontaneous sustained ventricular tachycardias

The purpose of this study was to compare electrocardiographic (ECG) morphologies of nonsustained ventricular tachycardias (VTs) during Holter monitoring with the ECG morphology of documented, sustained, monomorphic VTs during the spontaneous event of tachycardia in 14 patients (9 with coronary artery disease), in whom a sustained, spontaneous monomorphic VT had been documented in a 12-lead ECG. All patients had a 24-hour Holter ECG without antiarrhythmic medication. Channel 1 of the Holter ECG was compared with leads V1, V2, and V3, and channel 2 with leads V4, V5, and V6. The Holter ECG of 10 patients in whom the QRS complex during sinus rhythm was similar to the QRS complex in the corresponding ECG leads was accepted for analysis. In 8 of the 10 patients, nonsustained VTs were detected during Holter monitoring. In one of these eight, the ECG morphology of at least one nonsustained VT in the Holter recordings was identical with the sustained VTs. Thus, incidences and ECG morphologies of nonsustained VTs during Holter monitoring do not correlate closely with those of spontaneous sustained monomorphic VTs. Therefore, most ventricular runs during Holter monitoring may have a mechanism different from that of spontaneous sustained VTs.

Frequency domain measures of heart rate variability before the onset of nonsustained and sustained ventricular tachycardia in patients with coronary artery disease

BACKGROUND

Low heart rate variability (HRV) is associated with an increased risk of arrhythmic death and ventricular tachycardia (VT). The purpose of this study was to examine whether there is a temporal relation between changes in HRV and the onset of spontaneous episodes of VT in patients at high risk of life-threatening arrhythmias.

METHODS AND RESULTS

Components of HRV in the frequency domain were analyzed before the onset of 28 episodes of nonsustained VT (more than four impulses; duration < 30 seconds) and 12 episodes of sustained VT (> 30 seconds or requiring defibrillation) in 18 patients with coronary artery disease. Seven patients had survived cardiac arrest not associated with acute myocardial infarction, and 11 had a history of sustained VT. All frequency domain measures of HRV, i.e., total power (p < 0.001), high-frequency power (p < 0.05), low-frequency power (p < 0.01), very-low-frequency power (p < 0.01), and ultralow-frequency power (p < 0.05), were significantly lower before the onset of sustained VT than before nonsustained VT. Total power of HRV was also lower during the 1-hour period before the onset of sustained VT than the average 24-hour HRV (p < 0.05). An indirect correlation existed between the length of VT and the total power of HRV analyzed during the 15 minutes before the onset of VT (r = 0.54, p < 0.01). HRV had a trend toward increasing values before the onset of nonsustained VT (p < 0.01) but not before the sustained VT episodes. The ratio between low-frequency and high-frequency powers increased substantially before both nonsustained and sustained VT episodes (p = 0.06 and p = 0.05, respectively). The rate of VT or the coupling interval initiating the VT did not differ significantly between the nonsustained and sustained VT.

CONCLUSIONS

Spontaneous episodes of VT are preceded by changes in HRV in the frequency domain. Divergent dynamics of HRV before the onset of nonsustained and sustained VT episodes may reflect differences in factors that can facilitate the perpetuation of these arrhythmias.

Comparison of QRS morphologies of spontaneous premature ventricular complexes and ventricular tachycardia induced by programmed stimulation

We addressed the hypothesis that premature ventricular complexes (PVCs) and sustained ventricular tachycardia (VT) have identical QRS morphologies in 20 patients with recurrent sustained VT. Continuous six-lead ECGs of PVCs and sustained VT induced with programmed stimulation were recorded. A computer program divided the PVCs and VT beats of each patient into distinct morphologic groups and a representative waveform was obtained by averaging the PVC and VT beats of the group members. A correlation coefficient was then derived between the QRS complexes of each PVC and VT morphology. The mean number of PVC morphologies was 12 +/- 8 per patient (range 1 to 26), the mean number of VT morphologies was 2 +/- 1 per patient (range 1 to 5). The correlation coefficient between the dominant PVC morphology and a VT morphology was greater than 0.7 in only three patients. The combined percent contribution of all PVCs with morphologies that were at least possibly identical to those of VT averaged only 13%. Thus PVCs with morphologies identical to those of VT are present in some patients with sustained VT, but these constitute a small proportion of all PVCs.

Values and limitations of programmed stimulation and ambulatory monitoring in the management of ventricular tachycardia

Programmed stimulation (PES) and ambulatory electrocardiographic (Holter) monitoring are both widely used to evaluate the efficacy of antiarrhythmic drugs in patients with recurrent ventricular tachycardia (VT). PES is sensitive but nonspecific, and Holter is specific but insensitive. A failure to suppress ventricular premature complexes (VPCs) on Holter during drug therapy predicts a poor outcome. A suppression of VPCs by drug therapy, however, does not preclude a poor outcome. If VT is no longer induced by PES during drug therapy, the patients will have a good outcome. A persistent induction of VT during drug therapy, however, does not preclude good outcomes. Therefore some investigators have suggested alternative PES efficacy criteria such as the changes in the rate of induced VT during therapy. Further studies should be conducted to confirm this. Because both methods have values and limitations, a combined use of the 2 methods is recommended to improve the clinician's ability to predict the outcome of antiarrhythmic therapy. Studies designed to prove that 1 method is better than the other may prove futile.