Atsunobu Nomura

Repolarization dynamics in patients with long QT syndrome.

Repolarization Dynamics in LQTS. Introduction: Dynamics of ventricular repolarization may contribute to cardiac arrhythmias in subjects with the long QT syndrome (LQTS). The aim of the present study was to assess the dynamics of repolarization duration and the dynamics of repolarization complexity in LQTS patients and their unaffected family members.

Developmental Changes of α1-Adrenergic Chronotropic Action on Human Sinus Node

The important role of α 1 -adrenergic receptors in the genesis of cardiac arrhythmias in ischemia and during reperfusion 1 , 2 has recently been elucidated. On the other hand, α 1 -adrenergic modulation of cardiac rhythm has promoted interest in myocardial α 1 -adrenoceptor research. The chronotropic action of α 1 -adrenergic stimulation is usually reported as inhibitory rather than excitatory. 3 However, in some species and in certain tissues, the positive chronotropic action of α 1 -adrenergic stimulation has also been reported. Moreover, there is an important developmental component to the α 1 -adrenergic receptor-effector system. Although α 1 -adrenergic stimulation decreases automaticity in the human atrium and in the ventricular conducting system of the adult rat, 4 , 5 an increase in automaticity brought about by α 1 adrenergic stimulation was reported in isolated neonatal canine Purkinje fibers. 6 These findings suggest that the chronotropic response of cardiac tissues to α 1 -adrenergic stimulation changes from excitatory to inhibitory during development. This study clarifies the effect of α 1 -adrenergic stimulation on human sinus node automaticity, especially in relation to age.

Obesity does not influence electrocardiographic parameters in coronary patients.

Although elevated body mass index (BMI) was found to be associated with QT prolongation in healthy subjects, electrocardiographic findings in coronary patients in relation to BMI have not been investigated. We studied 936 coronary patients whose electrocardiographic parameters were compared according to their BMI and found that BMI did not affect the overall QT duration, but QT dispersion was significantly higher in normal-weight coronary patients than in obese patients.

Clinical and electrophysiologic effects of dofetilide in patients with supraventricular tachyarrhythmias.

The clinical and electrophysiologic effect of intravenous dofetilide was evaluated in patients with paroxysmal atrial fibrillation (AF) of recent onset (< 7 days) and paroxysmal supraventricular tachycardia (PSVT). From 2.5 to 5.0 micrograms/kg of dofetilide was administered intravenously for the termination of arrhythmias. For the electrophysiologic study (EPS), 3.0 micrograms for loading and subsequently 2 micrograms/kg was injected for 45 min as a maintenance dose. The EPSs were performed before the loading and during the maintenance dose. AF was successfully converted to sinus rhythm in seven (54%) of 13 patients. The duration of AF from its onset was significantly shorter in responders than that of nonresponders (p < 0.05). Dofetilide also terminated PSVT in four of six patients. In the EPS, dofetilide proportionately lengthened the effective refractory period of the atrium, ventricle, and the accessory pathways without slowing of the intracardiac conduction. Dofetilide completely suppressed the induction of PSVT in seven of 13 patients, restricted the induction zone in five, and inhibited perpetuation of the arrhythmia in the remaining one. The cycle length of PSVT remained unchanged after dofetilide. These results imply that the suppression of the development and maintenance of reentrant arrhythmias may result from the lengthening effect of dofetilide on the refractoriness and the consequent elimination of the excitable gap at the critical part of the reentrant loop.

Are multiple plaque disruptions more common in patients with acute coronary syndrome than in patients with stable ischemic heart disease

Background Plaque disruption with or without thrombus plays a key role in acute ccrcnary syndrome(ACS) and sudden progression of coronary lesions. Previous cur study demonstrated that plaque disruptions in culprit lesion is mere ccmmcn in patients with ACS than stable ischemic heart disease(SIHD). We investigated whether the prevalence of plaque disruptions in non ischemic related arteries is different between in patients with ACS and SIHD in living subjects. Methods We performed coronary angioscopy in non ischemic related artery on coronary angiography in 32 patients with ACS and 30 patients with SIHD. Forty-one arteries were explored in each groups. Results At least one plaque disruption was found somewhere other than on the culprit artery I” 31 patients(50%). Plaque disruption was found mere frequently in ACS group(Zlpts.65.6%) than in SIHD group(lOpts.33.3%)(pcO.O01). Conclusion Multiple plaque disruptions were mere ccmmcn in patients with acute ccrcnary syndrome than in patient with stable ischemic heart disease. These results indicate that acute coronary syndrome is not a local vascular accident but a pancoronary process.