Takuro Nishimura

Clinical assessment of cryoballoon ablation in cases with atrial fibrillation and a left common pulmonary vein

Pulmonary vein isolation (PVI) using a cryoballoon (CB) is a useful tool for treating atrial fibrillation (AF); however, the clinical efficacy of the CB has never been fully investigated in patients with a left common pulmonary vein (LCPV).

Left Atrial Appendage Thrombi Formation in Japanese Non-Valvular Atrial Fibrillation Patients During Anticoagulation Therapy ― Warfarin vs. Direct Oral Anticoagulants ―

BACKGROUND Atrial fibrillation (AF) is a common cardiac arrhythmia, associated with increased cardiovascular morbidity and mortality including thromboembolic events. The aims of this study were to assess the prevalence of left atrial appendage (LAA) thrombi in Japanese non-valvular atrial fibrillation (NVAF) patients undergoing preprocedural transesophageal echocardiography (TEE) during anticoagulation therapy, and to compare the efficacy of warfarin and direct oral anticoagulants (DOAC).Methods and Results:This retrospective study reviewed records of 559 consecutive NVAF patients (445 men; age, 62±11 years) undergoing preprocedural TEE following at least 3 weeks of anticoagulation therapy. Of these, 275 patients had non-paroxysmal AF (49%). LAA thrombus was observed in 15 patients (2.7%). The prevalence of LAA thrombi was similar between the DOAC group (2.6%) and the warfarin group (2.8%, P=0.86). No patients with CHA2DS2-VASc score=0, or paroxysmal AF without prior stroke or transient ischemic attack, had LAA thrombi. On univariate analysis, non-paroxysmal AF, structural heart disease, antiplatelet therapy, larger left atrium, higher brain natriuretic peptide (BNP), reduced LAA flow, and higher CHA2DS2-VASc score were all associated with LAA thrombi. On multivariate analysis, BNP ≥173 pg/mL remained the only independent predictor of LAA thrombi. CONCLUSIONS LAA thrombi were found in 2.7% of Japanese NVAF patients scheduled for procedures despite ongoing oral anticoagulation therapy. Incidence of thrombi was similar for patients on DOAC and on warfarin.

Novel Dielectric Coagulometer Identifies Hypercoagulability in Patients with a High CHADS2 Score without Atrial Fibrillation.

Background Recent reports showed that the CHADS2 score predicted the risk of strokes in patients without atrial fibrillation (AF). Although the hypercoagulability may contribute to the thrombogenesis, it has not been fully investigated due to a lack of a sensitive evaluation modality. Recently a novel dielectric blood coagulometry (DBCM) was invented for evaluating the coagulability by measuring the temporal change in whole blood dielectric permittivity. Objective We evaluated the utility of the DBCM for identifying the coagulability. Patients/Methods For fundamental experiments, 133 citrated blood samples were drawn from subjects with or without heparin administration. A DBCM analysis was performed to find the adequate coagulation index, and to delineate its measurement range by adding recombinant human tissue factor (TF) or heparin. Then the coagulability was assessed by DBCM and conventional coagulation assays in 84 subjects without AF, who were divided into 3 groups by their CHADS2 score. Another 17 patients who received warfarin were also assessed by DBCM to evaluate the effect of anticoagulants. Results and Conclusions We calculated the derivative of the dielectric permittivity change after recalcification, and extracted the end of acceleration time (EAT) as a novel index. The EAT showed a dose-dependent shortening with the addition of serial dilutions of TF (×10−2 to ×10−4), and a dose-dependent prolongation with the addition of heparin (0.05 to 0.15 U/ml). The EAT was significantly shorter in the higher CHADS2 score group (19.8 ± 4.8, 18.6 ± 3.1, and 16.3 ± 2.7 min in the CHADS2 = 0, 1, and ≥2 groups, respectively, p = 0.0065 by ANOVA). Patients receiving warfarin had a significantly more prolonged EAT than those without warfarin (18.6±4.2 vs. 25.8±7.3 min, p <0.001). DBCM detected the whole blood coagulability with a high sensitivity. Subjects with higher CHADS2 scores exhibited hypercoagulability without AF.

Automatic switching between the AAI and the DDD algorithm can prevent repetitive non-reentrant ventriculoatrial synchrony

A 67‐year‐old man with non‐obstructive hypertrophic cardiomyopathy had received an implantable cardioverter‐defibrillator (ICD) for an unstable, sustained ventricular tachycardia (VT) induced by programmed stimulation during an electrophysiological study 5 years earlier. An intracardiac electrogram recorded by the ICD revealed repetitive, non‐reentrant ventriculoatrial synchrony (RNRVAS) associated with hypotension. Electrophysiologic and hemodynamic studies indicated that RNRVAS was induced and reproducibly termed by a single ventricular extrastimulus from the right ventricular apex. Following attainment of the elective replacement indicator, we replaced the ICD with another having managed ventricular pacing, which automatically switched AAI and DDD, thereby avoiding unnecessary ventricular pacing. Thus far, the patient has not experienced further RNRVAS. Thus, we believe that automatic switching between AAI and DDD can prevent RNRVAS.

Differential Assessment of Factor Xa Activity and Global Blood Coagulability Utilizing Novel Dielectric Coagulometry

An easy-to-use assessment for activated factor X (FXa) is lacking despite its pivotal role in the coagulation. Dielectric blood coagulometry (DBCM) was recently invented as a novel assessment tool for determining the whole blood coagulability by measuring the temporal change in the permittivity of blood. We previously reported that it could evaluate the global blood coagulability. This study aimed to apply the DBCM for assessing FXa activity and its inhibition by anticoagulants. We performed the DBCM analysis along with measurement of the FXa activity by a fluorometric assay in samples from healthy subjects, and identified a new index named maximum acceleration time (MAT) that had a correlation to the FXa activity. Next the DBCM analysis was performed using blood samples mixed with anticoagulants (unfractionated heparin, dalteparin, and edoxaban). Blood samples with three anticoagulants had different profiles of the temporal change in the permittivity, reflecting their different selectivity for FXa. We compared the MAT with the anti-FXa activity assay, and found that the prolongation of MAT was similarly correlated with the anti-FXa activity regardless of the type of anticoagulants. In conclusion, the DBCM has the possibility for evaluating the innate FXa activity and effect of anticoagulants focusing on their FXa inhibition.

Right coronary artery wall edema provoked by cavotricuspid isthmus radiofrequency ablation

Introduction Acute coronary stenosis has been reported as a rare but potentially serious complication of cavotricuspid isthmus (CTI) ablation. Various causes of the stenosis have been reported (thrombus, coronary spasm), but cause is often unknown. Most of the cases receive coronary intervention regardless of the cause. We present a case of “temporary edema” of the coronary artery wall provoked by CTI radiofrequency (RF) ablation.

High-risk transseptal puncture in a patient with a “pancake” deformity in the left atrium caused by descending aorta displacement

Catheter ablation via the transseptal approach has recently become a widely performed technique for treating atrial fibrillation (AF). However, fluoroscopic imaging provides limited anatomic guidance for the left atrial structure. We describe the case of a 78‐year‐old man who was referred to our hospital for pulmonary vein isolation for symptomatic paroxysmal AF. He had a history of pulmonary tuberculosis for which he had undergone a right upper lobectomy. A “pancake” deformity of the left atrium (LA) was observed using 64‐slice multislice computed tomography. We performed a transseptal puncture by using real‐time three‐dimensional transesophageal echocardiography (RT3D‐TEE) in combination with fluoroscopic imaging, without any complications. Although transseptal puncture can be performed without echocardiographic guidance in most patients, in our patient, RT3D‐TEE proved to be a very helpful imaging technique to access the LA.