Shinobu Imai

Inverse Relationship Between Electrode Size and Lesion Size During Radiofrequency Ablation With Active Electrode Cooling

BACKGROUND Clinical efficacy has driven the use of larger electrodes (7F, length > or =4 mm) for radiofrequency ablation, which reduces electrogram resolution and causes variability in tissue contact depending on electrode orientation. With active cooling, ablation electrode size may be reduced. The purpose of this study was to examine the effect of electrode length on tissue temperature and lesion size with saline irrigation used for active cooling. METHODS AND RESULTS In 11 anesthetized dogs, the thigh muscle was exposed and bathed with heparinized canine blood. A 7F ablation catheter with a 2- or 5-mm irrigated tip electrode was positioned perpendicular or parallel to the thigh muscle. Radiofrequency current was delivered at constant voltage (50 V) for 30 seconds during saline irrigation (20 mL/min) to 148 sites. Tissue temperature at depths of 3.5 and 7 mm and lesion size were measured. In the perpendicular electrode-tissue orientation, radiofrequency applications at 50 V with the 2-mm electrode compared with the 5-mm electrode resulted in lower power at 50 V (26 versus 36 W) but higher tissue temperatures, larger lesion depth (8.0 versus 5.4 mm), and greater diameter (12.4 mm versus 8.4 mm). Also, in the parallel orientation, overall power was lower with the 2-mm electrode (25 versus 33 W), but tissue temperatures were higher and lesions were deeper (7.3 versus 6.9 mm). Lesion diameter was similar (11.1 versus 11.3 mm) for both electrodes. CONCLUSIONS The smaller electrode resulted in transmission of a greater fraction of the radiofrequency power to the tissue and resulted in higher tissue temperature, larger lesions, and lower dependency of lesion size on the electrode orientation.

Takotsubo-shaped cardiomyopathy with type I CD36 deficiency

A transient left ventricular apical ballooning (so-called “ampulla” or “Takotsubo-shaped” cardiomyopathy) with type I CD36 deficiency is described in a 71-year-old woman. The patient was referred because of chest pain and worsening of dyspnea. Electrocardiogram showed T-wave inversions on the precordal leads, and acute coronary syndrome was suspected. Left ventricular apical ballooning was observed by echocardiogram and left ventriculography, and coronary arteriography did not reveal any significant stenosis. Left ventricular motion normalized at the follow-up period and there were no increases in specific markers for myocardial damage, such as myocardial band fraction of creatine kinase and troponin T, through out the admission. 123I-metaiodobengylguanidine myocardial single photon emission computed tomography (SPECT) revealed decreased accumulation areas at the apex, while 201Tl SPECT showed normal accumulation. An abnormal metabolism of cardiac free fatty acid was suggested by lack of accumulation of 123I beta-methyliodophenyl pentadecanoic acid (BMIPP) SPECT. No CD36 expression in either platelets or monocytes/macrophages was shown using flow cytometer analysis and type I CD36 deficiency was diagnosed. DNA sequencing showed that the patient had compound heterozygosity of the CD36 gene (a nucleotide change in C478T and an adenine insertion at nucleotide 1159 in exon 10). Although CD36 deficiency is thought to be involved with many cardiovascular disease and metabolic abnormalities, Takotsubo-shaped cardiomyopathy with CD36 deficiency had not been reported. Further studies of Takotsubo-shaped cardiomyopathy and CD36 deficiency may reveal an association between this cardiomyopathy and specific genetic profiles.

Subendomyocardial perfusion abnormality and necrosis detected by magnetic resonance imaging in a patient with isolated noncompaction of the ventricular myocardium associated with ventricular tachycardia

A 74-year-old man presented with left ventricular failure and nonsustained ventricular tachycardia. Coronary angiography revealed normal coronary arteries; left ventriculography showed hypokinesis of the lateral wall segment. The ejection fraction was 54%. Cine-magnetic resonance imaging showed a double-layered appearance on four-chamber view and marked trabeculations as well as intratrabecular recesses in the inferolateral segments on short-axis view, findings consistent with isolated noncompaction of the ventricular myocardium (INVM). Contrast-enhanced imaging revealed hypoperfusion and delayed enhancement of the endomyocardium in the inferolateral segments. Subendomyocardial perfusion abnormality and necrosis may constitute the diagnostic criteria of INVM.

Long-term Prognosis for Non-ischemic Heart Disease Patients with Premature Ventricular Contraction and Non-sustained Ventricular Tachycardia

There are few long‐term reports of patients with frequent PVCs in the absence of ischemic heart disease. In 86 patients without ischemic heart disease, who had 1000 or more PVCs in 24‐hour Holter ECG, the number of PVCs during 24‐hours Holter ECG and echocardiographic parameters were followed at least 1 year (66.5 ± 39.7 months). PVC was significantly reduced in the patients with or without underlying diseases (UD). The reduction rate in the number of PVCs was prominent in patients with UD. PVC was significantly reduced in patients under medication, but not in patients without medication. In the comparison between the initial and follow up observation using Wilcoxons rank test, the number of PVC was significantly reduced (P < 0.05), and EF was also improved (P < 0.05) in angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) group, and in β‐blocker group. In Ca‐antagonist group and antiarrhythmic drug group, the number of PVCs was also significantly reduced (P < 0.05). Multivariate analysis revealed significantly higher incidence (60% or more with PVC reduction) in ACEI/ARB group.

Basic Autonomic Nervous Function in Patients with Neurocardiogenic Syncope

Basic autonomic nervous function was evaluated in patients with neurocardiogenic syncope (NCS). Atropine, isoproterenol, propranolol, phenylephrine, and phentolamine were administered successively, and parasympathetic nerve activity and β- (and α-) activity, sensitivity, and secretion of the sympathetic nerve were determined in patients with NCS and control subjects. In patients with NCS, β- and α- sensitivity were higher and β-activity and β- and α-secretion lower than in control subjects. In patients with NCS, the increased basic β-sensitivity may contribute to induce strong cardiac contractions and augment ventricular mechanoreceptor response, and a compensatory state against diminished neuronal sympathetic activity is suggested by the increased α-sensitivity.