Kohei Yamashiro

Improvement in the quality of the cardiac vein images by optimizing the scan protocol of multidetector-row computed tomography

The present study aimed at optimizing the scan protocol for multidetector-row computed tomography (MDCT) to adequately visualize coronary veins. Circulation time (Cir.T) was defined as the time period from the injection of contrast media into the coronary artery to the pervasion of the contrast media into the coronary sinus as observed by coronary angiography. We investigated the relation between the Cir.T and echocardiographic parameters in 64 patients. The left ventricular end-diastolic diameter (LVDd) and left ventricular end-systolic diameter (LVDs) were correlated with the Cir.T (r = 0.58, P < 0.0001, and r = 0.60, P < 0.0001 respectively). In addition, the left ventricular ejection fraction (LVEF) was negatively correlated with the Cir.T (r = 0.48, P < 0.0001). The average Cir. T was longer in patients with LVEF < 35% (8.0 s vs 6.7 s; P < 0.05) or LVDd > 55 mm (7.9 s vs 6.2 s; P < 0.05) than in the other patients. The quality of the MDCT images of the coronary veins obtained at different scan timings (coronary artery phase and 10 s or 15 s after the coronary artery phase) were graded and classified into four categories (0 = worst, 3 = best) in 25 patients with LVEF < 35%. The delays of 10 and 15 s after the coronary artery phase significantly improved the mean image quality (P < 0.05). The Cir.T was prolonged in patients with low LVEF and LV dilation. An appropriate delay improved the quality of the MDCT images of the coronary veins in patients with LV dysfunction.

Trans-aortic pulmonary vein isolation using magnetic navigation system for paroxysmal atrial fibrillation in a patient with dextrocardia, situs inversus, and inferior vena cava continuity with azygos vein

A 51‐year‐old male with dextrocardia and situs inversus underwent catheter ablation for paroxysmal atrial fibrillation. Because the procedure through the trans‐septal approach was impossible due to the inferior vena cava continuity with azygos vein, we performed pulmonary vein isolation using magnetic navigation system through the retrograde trans‐aortic approach. Superior and inferior left‐sided and superior right‐sided pulmonary veins could be isolated which was confirmed by the ablation catheter. The patient was free from atrial fibrillation episode at the 12 months follow‐up except only one palpitation episode lasting nearly 12 hours at 9 months after the ablation.

Impact of ganglionated plexi ablation on high-frequency stimulation-induced changes in atrial fibrillation cycle length in the pulmonary vein

We assessed high‐frequency stimulation (HFS)‐induced changes in the atrial fibrillation (AF) cycle length (AFCL) in the pulmonary vein (PV) after ganglionated plexi (GP) ablation.

Usefulness of MDCT Guided Mitral Isthmus Ablation

Mitral isthmus (MI) ablation is challenging. Blood flow in the CS and circumflex artery (LCx) may act as a heat sink and reduce the efficacy of radiofrequency ablation. Ablation in the CS also has the risk of injury to the LCx. We have reported to be able to visualize the precise anatomical characteristics between CS and LCx on MI obtained by MDCT. The aim of this study was to evaluate usefulness of MDCT guided MI ablation. Methods: Twenty patients (14 males, 61±11 y) whose CS and LCx images could be obtained simultaneously by MDCT were included in this study. We performed MI ablation between LIPV and the mitral annulus. The strategy for MDCT guided MI ablation were 1. MI line was designed just below LAA, 2. In case of LCx below CS, MI line was designed proximal the crossing point of LCX and CS, and 3. If LCX is presence on MI, MI line designed more laterally on comparatively peripheral LCX. Irrigated-tip catheters were used during MI ablation with the following settings: endocardial surface (maximum power: 40 W); CS (maximum power: 20 W). Results: The MI was blocked in 94.5% (19/20) of patients with 594±293 seconds of radiofrequency application. The epicardial ablation inside the CS was required in 45% (9/20) patients. No complications occurred. Conclusion: The MDCT guided MI ablation resulted in a high success rate of MI block without complications.

Ventricular tachycardia in patients with idiopathic dilated cardiomyopathy is associated with delayed enhancement MRI

of PSVT in the Korean population is limited. In this study, we sought to investigate the differing mechanisms of PSVT according to age and gender in Korean patients. Methods: Database of 3176 patients diagnosed with PSVT excluded atrial flutter or atrial fibrillation and referred for electrophysiologic study from 1986 to 2004 was retrospectively analyzed. The mechanisms of PSVT were classified as: WPW syndrome(WPW), AVRT due to concealed bypass tract(CBT), atrioventricular nodal reentrant tachycardia(AVNRT), atrial tachycardia(AT). Results: The mean age was 40.7 16.0(1-90) and 53.3% of the patients were males. The mean age of females was significantly higher than males.(43.0 16.1 vs 38.6 15.6, p 0.001) Overall, the dominant mechanism of tachycardia was AVRT at 62.6%(WPW: 31.1%, CBT: 31.5%) compared to AVNRT at 34.1% and AT at 3.1%. This was mainly due to the predominance of AVRT(74.2%) in males. The mechanisms of PSVT differed according to gender with 63.2%(1257/1988) of AVRT patients being males where as 64.6%(700/1084) of the AVNRT patients were females. The distribution of PSVT mechanisms differed according to gender. In males, the proportion of AVNRT:CBT:WPW was 22.7%:36.1%:38.1%, whereas in females the proportion was 47.2%:26.3%: 23.0%. Age had a significant influence upon the mechanism of PSVT in both genders with an increasing proportion of AVNRT and a decreasing proportion of AVRT in older age groups. AVRT was the dominant mechanism of PSVT in all age groups for males, where as AVNRT was the dominant mechanism of PSVT for females over 50 years of age. Conclusions: The mechanism of PSVT differs significantly according to age and gender. This may be due to increased degeneration of accessory pathway with age and difference in the conduction properties of the accessory pathway according to gender. In Koreans, the overall dominant mechanism of PSVT was AVRT mainly due to it a greater male population.