Shinji Karakawa

Dependency on atrial electrophysiological properties of appearance of paroxysmal atrial fibrillation in patients with Wolff-Parkinson-White syndrome: evidence from atrial vulnerability before and after radiofrequency catheter ablation and surgical cryoablation.

The pathogenesis of paroxysmal atrial fibrillation in patients with Wolff‐Parkinson‐White syndrome and the effects of elimination of accessory pathways on the appearance of atrial fibrillation are still controversial. Fifty‐four patients with Wolff‐Parkinson‐White syndrome were classified into three groups: a No AFgroup (n = 24), patients without paroxysmal atrial fibrillation; an RF‐AF Group (n =12), patients with paroxysmal atrial fibrillation whose accessory pathways were eliminated using radiofrequency catheter ablation; and a Cryo‐AF Group (n = 18), patients with paroxysmal atrial fibrillation whose accessory pathways were eliminated with surgical Cryoablation. The electrophysiological characteristics of each group were evaluated prior to and following the elimination of their accessory pathways. As indices of atrial vulnerability, the presence of fragmented atrial activity and repetitive atrial firing zones were assessed. Deducibility of atrial fibrillation was significantly reduced following ablation of accessory pathways in the Cryo‐AF group (83.3%‐5.6%, P < 0.0001), while it was unchanged in the RF‐AF group (83.3%‐75%). In preablation studies, the effective refractory periods of the atrium in the RF‐AF group and the Cryo‐AF group were significantly shorter compared with the No AF group (204 ± 18 ms, 197 ± 16 ms vs 246 ± 44 ms, respectively, P < 0.0001). Following ablation, the effective refractory period for patients in the Cryo‐AF group was significantly prolonged compared with before ablation (197 ± 16 ms to 232 ± 24 ms, P < 0.0001). As a result of this prolongation of the effective refractory period of the atrium, the fragmented atrial activity and repetitive atrial response zones narrowed following ablation in the Cryo‐AF group, but not in the RF‐AF group. Therefore, the pathogenesis of atrial fibrillation in patients with Wolff‐Parkinson‐White syndrome may depend on the refractory period of the atrium rather than on the presence of accessory pathways.

Early Afterdepolarizations in a Patient with Idiopathic Monomorphic Right Ventricular Tachycardia

To identify the role of afterdepolarizations in the induction of idiopathic monomorphic right ventricular tachycardia (VT), monophasic action potentials (MAPs) were recorded in a patient with this type of VT. The VT had a left bundle branch block configuration and inferior axis, and originated in the right ventricular outflow tract (RVOT). MAPs were recorded with a contact electrode at the origin of the VT, as well as other ventricular sites. The VT was induced by the intravenous administration of isoproterenol and/or rapid ventricular pacing and was preceded by short‐long‐short sequences of RR intervals. Early afterdepolarizations (EADs) in MAPs were recorded at the origin of VT (RVOT), but not recorded at other ventricular sites. These data suggest that catecholamine sensitive triggered activity seems to be the mechanism of idiopathic monomorphic right VT and EADs can be recorded in association with the occurrence of this type of VT.

Time interval determination from left atrial appendage ejection flow in patients with mitral stenosis.

The feasibility of determining the time interval from left atrial appendage (LAA) flow was examined using transesophageal Doppler echocardiography. Time intervals were compared between LAA flow and mitral flow patterns during late diastole in 8 patients with mitral stenosis and in 12 controls. The start of ejection flow from the LAA was later than the initiation of mitral flow, but the termination was same in both flows, indicating the contribution of LAA ejection to the latter half of the left atrial booster pump function. The pre‐ejection time and the time interval from P‐wave to end‐ejection correlated significantly with left atrial dimensions (r = 0.55, and r = 0.70, respectively). The pre‐ejection time, duration of the ejection flow from the LAA, and duration of mitral flow in the atrial contraction phase were significantly longer in patients with mitral stenosis (126 ± 14 msec, 131 ± 36 msec, and 167 ± 28 msec, respectively) than in the controls (109 ± 13 msec, 108 ± 15 msec, and 141 ± 17 msec, respectively). These results indicate that electrical conduction time from the right atrium to LAA can be estimated from the LAA ejection flow, and the time is related to the left atrial size. In patients with mitral stenosis, LAA contraction may contribute to left ventricular filling in the latter half of the atrial contraction phase.

Guidewire Bias in Rotational Atherectomy in the Angled Lesion

The effect of guidewire bias on angled-lesion ablation by rotational atherectomy (RA) was assessed by measuring the changes in vertical lumen diameter, horizontal lumen diameter and the intima-media thickness of the coronary artery, using intravascular ultrasound in 10 lesions with an angle greater than 10 degrees. The vertical and horizontal diameters significantly increased after RA. The intima-media thickness at the 4 orthogonal sites significantly decreased. There was a significant positive correlation between vertical diameter change and angle (r=0.642, p=0.045), but none between horizontal diameter change and angle. There was no correlation between intima-media thickness change at 0 degrees and angle; however, at 180 degrees there was a tendency to correlation with angle (r=0.602, p=0.066). These data suggest that in cases of angled lesions, the increase in vertical lumen diameter is caused more by ablation of the 180 degrees wall than by that of the 0 degrees wall, which is brought about by guidewire bias toward the vascular wall at 180 degrees.