14th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 2000

Jan. 29 - Feb. 5, 2000
Marilleva, Trento, Italy

RT-49

Heart rate variability in ventricular rate-responsive pacing in children: a useful tool to evaluate heart rate physiology?

Massimo Stefano Silvetti, Paolo Versacci, Silvia Anaclerio, Fabrizio Drago, Roberto Teodoro Bock*, Antonella Santilli, Emanuela Pompei, Andrea Spampinato**, Pietro Ragonese.
Department of Pediatric Cardiology, Bambino Gesu Hospital, Roma, *S. Camillo De Lellis Hospital, Rieti; **Villa Tiberia Hospital, Roma, Italy

Abstract

Because of small body size, venous access and implant technique, in small children with complete atrioventricular block, the pacing mode of choice is ventricular rate-responsive pacing which can be later upgraded to dual-chamber pacing. Heart rate variability (HRV) is used to evaluate the autonomic modulation of sinus node. Purpose of this study is the comparison of heart rate and HRV in normal children and in children with VVIR pacemakers, to evaluate if this not-physiological pacing mode can simulate a physiological behaviour.

METHODS. We performed clinical examination, standard ECG, doppler-echocardiography and 24-hour ambulatory ECG monitoring in two groups of children: I, 17 patients (9 males) aged 6.1±2.4 years with congenital (10 pts) or post-surgical atrioventricular block (tetralogy of Fallot in 4 pts, ventricular septal defect in 3), with VVIR pacemakers, and II, 52 healthy subjects (35 males) aged 5.8±2.6 years. HRV was computed by SDNN, SDNN index (SDNNi) and SDANN.

RESULTS. Patients were not taking any therapy; echocardiography showed normal ventricular function in all children. No significant arrhythmias were recorded and all patients were continuously paced during Holter recording. Age at PM implant was 3.6±2.1 years. Lower pacing rate was 75±8 b/m, upper rate was 168±15 b/m; activity parameters were programmed with activity threshold at medium and rate-response curve at mean values. Except for age, SDNN-i and mean HR (group I, 87±11 bpm, II 94±13 bpm), differences were statistically significant: SDNN 107±25 ms (I) vs 126±38 (II); SDANN 85±21 ms (I) vs 101±29 ms (II); maximum heart rate 150±24 bpm (I) vs 175±23 bpm (II).

CONCLUSIONS. SDNN and SDANN correlate with global autonomic activity. Thus, even if mean heart rate is comparable in both groups, children with VVIR pacing, during normal daily activities show HRV indexes of global autonomic function that are significantly lower than age-matched controls.

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