Kaoru Okishige

Electrophysiologic effects of ischemic preconditioning on QT dispersion during coronary angioplasty

OBJECTIVES The aim of this study was to examine the effect of ischemic preconditioning on the manner of ventricular repolarization by assessing the change in QT dispersion during coronary angioplasty. BACKGROUND QT interval dispersion reflects regional variations in ventricular repolarization and cardiac electrical instability. Previous studies have suggested that increased QT dispersion is associated with an increased incidence of malignant ventricular arrhythmias, whereas brief episodes of myocardial ischemia can render the heart more resistant to subsequent ischemic episodes, a phenomenon called ischemic preconditioning. METHODS To assess the effects of ischemic preconditioning on myocardial repolarization by examining the change in QT dispersion during coronary angioplasty, we studied 47 consecutive patients (39 men and 8 women; mean age 57 +/- 16 years). QT dispersion was measured after each balloon inflation during coronary angioplasty. Statistical analysis was performed by using repeated measurement of analysis of variance. RESULTS There were significant differences in QT dispersion as the number of balloon inflations increased (mean +/- SD 52 +/- 14, 42 +/- 11, 36 +/- 9, 31 +/- 10 and 29 +/- 11 ms, respectively [p < 0.01], for the first, second, third, fourth and fifth balloon inflations). The magnitude of decrease in QT dispersion was significant in the first and second balloon inflations, then became insignificant with later inflations. CONCLUSIONS These data indicate that the gradual decrease in QT dispersion provoked by coronary artery occlusion and reperfusion during coronary angioplasty may be associated with electrophysiologic effects of ischemic preconditioning on myocardium in the human heart.

Ethanol infusion in the vein of Marshall facilitates mitral isthmus ablation

BACKGROUND Treatment of perimitral flutter (PMF) requires bidirectional mitral isthmus (MI) block, which can be difficult with radiofrequency ablation (RFA). The vein of Marshall (VOM) is located within the MI. OBJECTIVE To test whether VOM ethanol infusion could help achieve MI block. METHODS Perimitral conduction was studied in patients undergoing ablation of atrial fibrillation. Group 1 included 50 patients with a previous atrial fibrillation ablation undergoing repeat ablation, 30 of whom had had MI ablation. Spontaneous (8 of 50) or inducible PMF (21 of 50) was confirmed by activation mapping. Group 2 included 21 patients undergoing de novo VOM ethanol infusion. The VOM was cannulated with a quadripolar catheter for pacing and with an angioplasty balloon to deliver up to four 1-mL infusions of 98% ethanol. Voltage maps were created before and after VOM ethanol infusion. Bidirectional MI block was verified by differential pacing. RFA times required to achieve it were assessed. RESULTS In group 1, VOM ethanol infusion acutely terminated PMF in 5 of 29 patients. RFA needed to achieve bidirectional MI block was 2.2 ± 1.6 minutes. Presence of PMF or previous MI ablation did not affect RFA times. In group 2, RFA needed to achieve bidirectional MI block was 2.0 ± 1.6 minutes (P = NS). Five patients had bidirectional MI block achieved solely by VOM ethanol infusion without RFA. In both groups, ablation after VOM ethanol infusion was required in the annular aspect of the MI. There were no acute complications. CONCLUSION VOM ethanol infusion is useful in the treatment of PMF and assists in reliably achieving bidirectional MI block.

Radiofrequency Catheter Ablation for AV Nodal Reentrant Tachycardia Associated with Persistent Left Superior Vena Cava

Slow A V nodal pathway ablation using RF is highly effective for patients with refractory A V nodal reentrant tachycardia (AVNRT). We report three catheter ablation cases using RF current in patients associated with persistent left superior vena cava (PLSVC). Three patients with drug refractory AVNHT of common variety were involved in this study. An electrode catheter introduced through the left subclavian vein inserted directly into the coronary sinus, a typical anatomical finding of PLSVC. The ablation procedure was initially performed at the posteroinferior region of Kochs triangle. A slow pathway potential could not be found from that area; nonsustained junctional tachycardia (NSJT) did not occur during the delivery of RF current; there was failure to eliminate slow AV nodal pathway conduction. The catheter then was moved into the bed of the proximal portion of the markedly enlarged coronary sinus. A slow AV nodal pathway potential was recorded through the ablation catheter, and the delivery of RF current caused NSJT in two patients. Complete elimination of slow AV nodal pathway conduction was accomplished in these two patients by this method. No adverse effects were provoked by this procedure. Catheter ablation of the slow A V nodal pathway guided by a slow pathway potential and the appearance of NSJT was feasible and safe in the area of the coronary sinus ostium in patients associated with PLSVC.

Clinical Study Regarding the Anatomical Structures of the Right Atrial Isthmus Using Intra-Cardiac Echocardiography: Implication for Catheter Ablation of Common Atrial Flutter

Background: The construction of complete bi-directional block in the isthmus (ITH) between the tricuspid annulus and inferior vena cava by radiofrequency energy (RF) applications is sometimes hampered due to anatomical problems such as a thick isthmus or aneurysmal pouch in patients with common atrial flutter (AFL).Methods and Results: Fifteen patients were referred for RF ablation of AFL. The anatomical thickness of the right atrial ITH, diameter of the right atrium and thickness of the right atrial free wall were determined using intracardiac echocardiography (ICE), along with the endocardial electrogram recordings at the ITH. RF was applied at the ITH to create a transmural incision to treat the AFL. A significant parallel relationship between the maximum amplitude of the atrial electrogram and the thickness of the ITH, was observed. When the maximum amplitude of the atrial electrogram at the ITH exceeded 1.5 mV, the thickness at the ITH was approximately larger than 5 mm.Conclusions: Using ICE, the precise measurement of the anatomical structures in the heart, including the ITH, was feasible. From the amplitude of the atrial electrogram, a deduction of the thickness at the ITH was possible, which is indispensable information for the appropriate selection of the RF devices.

Suppression of incessant polymorphic ventricular tachycardia by selective intracoronary ethanol infusion.

Two weeks after an extensive anterior myocardial infarction, a 68‐year‐old man developed incessant polymorphic ventricular tachycardia (PMVT), unresponsive to all conventional treatment modalities. After requiring > 40 direct current cardioversions in < 3 hours, he underwent attempted intracoronary chemical ablation of his arrhythmia as a treatment of last resort. An infusion catheter was positioned selectively in the subtotally occluded left anterior descending (LAD) coronary artery, the putative “tachycardia‐related vessel.” Fifty percent ethanol was delivered to the anterior wall through this catheter by slow, constant infusion. Following selective intracoronary ethanol infusion, spontaneous, unprovoked episodes of PMVT ceased, despite discontinuation of all antiarrhythmic drugs. The LAD remained patent. Several days later, the patient underwent coronary artery bypass surgery and implantation of an implantable defibrillator, succumbing in the early postoperative period from recrudescent intractable ventricular fibrillation and cardiogenic shock. Slow intracoronary infusion of 50% ethanol does not cause abrupt vessel occlusion such as occurs after rapid injection of higher concentrations of ethanol. Selective intracoronary infusion of 50% ethanol may provide temporary lifesaving suppression of otherwise intractable polymorphic ventricular tachycardia.

Factors leading to failure to diagnose acute aortic dissection in the emergency room

BACKGROUND Acute aortic dissection (AAD) is often missed on initial assessment. PURPOSE The aim of our study was to identify features associated with misdiagnosis of AAD. METHODS AND RESULTS We examined a total of 109 emergency room (ER) patients who were ultimately diagnosed with AAD. Misdiagnosis of AAD was defined as failure to diagnose AAD at the end of the initial assessment in the ER, and occurred in 17 patients (16%). The alternate diagnosis consisted of acute coronary syndrome (n=10), other cardiovascular disease (n=3), abdominal disease (n=3), and cerebral infarction (n=1). In the misdiagnosed patients, walk-in mode of admission to the ER (29% vs. 10%, p=0.042) and anterior chest pain (71% vs. 41%, p=0.025) were more frequent, and widened mediastinum (25% vs. 55%, p=0.023) was less frequent than in diagnosed patients. The number of imaging studies performed per patient was also fewer in misdiagnosed patients than in diagnosed patients (0.82 ± 0.81 vs. 1.53 ± 0.52, p<0.001). However, there was no significant difference in in-hospital mortality (18% vs. 15%, p=0.520). Multivariate analysis showed that the strongest predictor of misdiagnosis was walk-in mode of admission (odds ratio 4.777; 95% confidence interval 1.267-18.007; p=0.021). CONCLUSIONS Both diversity of symptoms and variability of the severity of symptoms, especially walk-in mode of admission lead ER physicians to miss AAD in about 1 in 6 cases of AAD. It is therefore important to keep AAD as a differential diagnosis in mind, even when patients present with mild enough symptoms that allow them to walk into the ER.

Radiofrequency ablation of tachyarrhythmias in patients with Ebstein's anomaly

We performed radiofrequency catheter ablation in five patients associated with Ebsteins anomaly to cure their refractory tachyarrhythmias. The presenting arrhythmias were four cases of orthodromic circus movement tachycardia using accessory pathways as a requisite limb, including one case of a Mahaim fiber and one of atrial flutter of common variety. All accessory pathways, including the Mahaim fiber, were ablated by RF energy delivered through the catheter placed at the AV annulus rather than the displaced anatomical AV groove. Interestingly, the antegrade or retrograde conduction interval over these accessory pathways was relatively longer than that of usual accessory pathways, and the accessory pathway potential was fractionated in some cases. The location of the atrioventricular node was displaced from the usual position to the postero-inferior area of Kochs triangle in one case. The configuration of the flutter wave was larger than usual in height as well as in width. All tachyarrhythmias were cured by RF catheter ablation. In the case of RF catheter ablation for patients with Ebsteins anomaly, close attention is indispensable in order to accomplish it safely and successfully, because of the anatomical and functional differences peculiar to Ebsteins anomaly.

Novel method for earlier detection of phrenic nerve injury during cryoballoon applications for electrical isolation of pulmonary veins in patients with atrial fibrillation

BACKGROUND Diaphragmatic electrogram recording during cryoballoon ablation (CB-A) of atrial fibrillation is commonly used to predict phrenic nerve palsy (PNP). OBJECTIVE The purpose of this study was to investigate a novel method for predicting PNP at an earlier stage to prevent sustained PNP. METHODS A total of 197 patients undergoing CB-A were enrolled. We attempted to detect PNP using fluoroscopic images of diaphragmatic contractions and by monitoring diaphragmatic compound motor action potentials (CMAPs) provoked by superior vena cava (SVC) and left subclavian vein (LCV) pacing during CB-A for bilateral pulmonary veins (PVs). Pacing of the SVC and LCV was performed at 2 outputs, 1 exceeding the pacing threshold by 10% (MIN) and the other at maximum output (MAX). The time from freezing to the initiation of PNP, values of the CMAP amplitude, and severity of PNP were compared for the 2 outputs. RESULTS There was a significant difference in the time from freezing to initiation of PNP between MIN and MAX pacing (25.7 ± 5.7 vs 81.3 ± 7.4 seconds, P<.01). CMAP amplitudes also differed significantly (0.71 ± 0.39 vs 1.13 ± 0.42, P<.0001). SVC/LCV pacing with MIN output was able to detect PNP significantly earlier than MAX (27 ± 8 vs 91 ± 12 seconds, P<.01), and the time to PNP recovery was significantly shorter for the MIN output (20.2 ± 8.88 hours vs 4.8 ± 1.6 months, P<.001). CONCLUSION Pacing the SVC and LCV with lower output detect PNP significantly earlier than maximal output pacing and leads to recovery from PNP on the order of hours postprocedure rather than months.

Comparative study of hemorrhagic and ischemic complications among anticoagulants in patients undergoing cryoballoon ablation for atrial fibrillation

OBJECTIVE Few data exist to evaluate the safety and efficacy of direct oral anticoagulants (DOACs) in patients with atrial fibrillation (AF) undergoing cryoballoon ablation (CB-A). This study is aimed to clarify the usefulness of DOACs in patients undergoing CB-A. METHODS The patients (average age; 65.8±11.9 years old, male 69%) were stratified into one of five subsets based on the type of anticoagulation (warfarin, apixaban, dabigatran, rivaroxaban, or edoxaban), and underwent CB-A. A brain MRI was performed in all patients the day after the CB-A for AF. A total of 257 (19 on warfarin, 30 on apixaban, 66 on dabigatran, 81 on rivaroxaban, and 61 on edoxaban) patients met the inclusion criteria. RESULTS The incidence of silent cerebral ischemic lesion was 1 (11.1%) patients on warfarin, 5 (33.3%) on apixaban, 8 (27.6%) on dabigatran, 10 (21.3%) on rivaroxaban, and 10 (29.4%) on edoxaban (p=0.17). Major ischemic events occurred in one patient (1.6%) on edoxaban and one (5.3%) on warfarin. Minor bleeding complications occurred in 1 patient (5.3%) on warfarin, 2 (6.7%) on apixaban, 1 (1.2%) on rivaroxaban, 5 (7.6%) on dabigatran, and 2 (3.3%) on edoxaban (p=0.24). Of note, major bleeding complications occurred in 2 patients (3.3%) on apixaban, 1 (1.2%) on rivaroxaban, 1 (1.5%) on dabigatran, 1 (1.6%) on edoxaban, and 2 (10.5%) on warfarin (p<0.05). CONCLUSIONS Warfarin use significantly increased the risk of serious bleeding, in contrast, CB-A did not place the patients at an increased risk of complications under a DOAC treatment. There were no significant differences regarding preventing embolic events among the DOAC drugs.

Electrophysiological Demonstration of Anterograde Concealed Conduction in Accessory Atrioventricular Pathways Capable Only of Retrograde Conduction

Anterograde concealed conduction into the concealed accessory atrioventricular (AV) pathway has been postulated to be one of the factors preventing the reciprocating process via the accessory pathway in patients with the concealed Wolff‐Parkinson‐White(WPW) syndrome but its presence has not been documented. To demonstrate the occurrence of anterograde concealment, 12 patients with the concealed WPW syndrome were selected for study. A pacing protocol was designed in which the retrograde conduction of the ventricular extrastimulus over the accessory pathway was assessed during ventricular pacing aione (conventional method) and during the AV simultaneous pacing (simultaneous method); the results were then compared. When the high right atrium was simultaneously paced, the effective refractory period of the concealed accessory pathway shortened as compared with the conventional method in five of 12 patients (from 341.7 ± 110.8 to 312.5 ± 108.2 msec, n = 12), whereas, it decreased in all patients studied when the coronary sinus near the accessory pathway was simultaneously paced (from 375.7 ± 135.0 to 287. ± 116.1 msec, n = 7). These results demonstrate that the AV simultaneous pacing frequently shortens the refractoriness of the concealed accessory AV pathway and such facilitation seems to he well explained by the probable anterograde concealment in it and peeling back of the refractory barrier.