November 1, 1996Pacing and Clinical Electrophysiology

Congestive Heart Failure and VVI Pacing Mode: Dynamic Behavior of the Dispersion of Ventricular Repolarization

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Why the study?

Does the spatial dispersion of ventricular repolarization exhibit circadian variation in continuously paced patients with congestive heart failure compared to controls without structural heart disease?

Structured PICO

Population

14 patients (10 males, 4 females, aged 65 +/- 8 years) with congestive heart failure (CHF) due to dilated cardiomyopathy (DCM) and an echocardiographic ejection fraction of 28% +/- 3%, who underwent AV junctional RF ablation and permanent pacemaker implantation for drug refractory chronic atrial fibrillation (AF).

Intervention

Continuous VVI pacing mode at 70 beats/min, evaluated at 1 month postimplant with a 24-hour Holter monitor.

Comparator

20 patients without structural heart disease, but with AF and complete AV block, continuously paced in VVI mode at 70 beats/min.

Outcome

Circadian variation in the spatial dispersion of ventricular repolarization (measured as the mean value of spike-T interval dispersion of the first five beats for each hour).surrogate

Patients with heart failure and dilated cardiomyopathy exhibit a significant circadian variation in ventricular repolarization dispersion during continuous VVI pacing, with increased dispersion at night.

Implication

Suggests nocturnal arrhythmic vulnerability in paced CHF; hypothesis-generating, requires prospective validation before any practice change.

Abstract

Dynamic Behavior of the Dispersion of Ventricular Repolarization. The aim of this study was to evaluate the circadian variation in the spatial dispersion of ventricular repolarization in continuously paced patients with congestive heart failure (CHF). Fourteen patients (10 males, 4 females, aged 65 +/- 8 years) with CHF due to dilated cardiomyopathy (DCM) and an echocardiographic ejection fraction of 28% +/- 3% were studied. All patients underwent AV junctional RF ablation and permanent pacemaker implantation for drug refractory chronic atrial fibrillation (AF). Patients were evaluated at 1 month postimplant with a three-channel 24-hour Holter monitor, using the three plane Frank orthogonal leads (X, Y, and Z), in VVI pacing mode at 70 beats/min. For each hour, the mean value of spike-T interval dispersion of the first five beats was measured. The control group consisted of 20 patients without structural heart disease, but with AF and complete AV block, continuously paced in VVI mode at 70 beats/min. The dispersion of the spike-T interval had a circadian behavior in the study population, with higher values at night and lower during the daytime. During the daytime, the mean value of spike-T interval dispersion was 39 +/- 5 ms and during the nighttime it was 45 +/- 7 ms (P = 0.003). Such a difference between day and night was not found in the control group (38 +/- 6 ms and 40 +/- 8 ms, respectively, P = NS). In the daytime period the mean value of spike-T interval dispersion of our study population was comparable to that of the control group (P = NS), while during the nighttime it was significantly higher (P = 0.0004). In conclusion, by evaluating the dispersion of ventricular repolarization in two dimensions, space and time, a circadian variation was found in paced patients with CHF due to DCM. The increased QT dispersion in these patients during the nighttime period was attributed to different effects of vagal activity in normal and abnormal myocardial areas.