| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
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| Research Abstract |
The purpose of this study is to evaluate risk factors of life-threatening ventricular arrhythmias in childhood. Because increased dispersion of repolarization is thought to be a substrate of lethal ventricular arrhythmia, we examined the distributions of activation recovery interval (ARI), which reflects action potential duration of ventricular myocyte, of children with long QT and ventricular arrhythmias, and compared to normal children. Distributions of ARI were studied by ARI isochrone maps and corrected ARI dispersion (ARIc-d) were calculated. We also examined heart rate variability from Holter ECG of patients with long QT syndrome (LQTS), and analyzed the autonomic nervous activity and their effects to ventricular recovery properties.
Results of this study are as follows.
1. ARIc-d values were almost the same in all ages through childhood and the normal upper limit value of them were around 200msec.
2. In patients having long QT interval in ECG, those with a syncopic event or familia
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l history showed significantly high ARIc-d, but those without symptom showed normal values. In patients having ventricular arrhythmias, those with ventricular tachycardia showed significantly high ARIc-d, compared to those with a single PVC and no couplet, who shoed normal values.
3. Therefore, abnormal heterogeneity of action potential durations of ventricular myocytes, which can induce a lethal ventricular tachycardia could be represented as an increase in ARIc-d value.
4. As to analyzing heart rate variability in this study, instability index of HF power, representing parasympathetic nerve activity, was low in LQTS patients, especially in a patient who died suddenly during his exercise.
5. Two LQTS children showed ventricular premature beats and T-wave change in Holer ECG following rapid increase of LF/HF, which means activating sympathetic nerve power. So, chages of autonomic nerve activity can effect to abnormal repolarization inducing ventricular arrhythmia.
ARI dispersion calculated by body surface map and autonomic nerve activity analized by heart rate variability in children with ECG abnormalities are good method for non-invasive screening of life-threatening ventricular arrhythmias relating to repolarization abnormalities. Less
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