Mitsuaki Takami

Assessment of Noninvasive Markers in Identifying Patients at Risk in the Brugada Syndrome: Insight Into Risk Stratification

OBJECTIVES The aim of this study was to compare the use of various noninvasive markers for detecting risk of life-threatening arrhythmic events in patients with Brugada syndrome. BACKGROUND The role of conduction disturbance in arrhythmogenesis of the syndrome is controversial, whereas it is well established that repolarization abnormalities are responsible for arrhythmias. The value of noninvasive markers reflecting conduction or repolarization abnormalities in identifying patients at risk for significant arrhythmias has not been shown. METHODS We assessed late potentials (LP) using signal-averaged electrocardiography (ECG), microvolt T-wave alternans (TWA), and corrected QT-interval dispersion (QTD) in 44 consecutive patients who had ECGs showing a pattern of right bundle branch block and ST-segment elevation in leads V1 to V3 but structurally normal hearts. The patients were compared with 30 normal individuals. RESULTS Eleven patients were excluded from data analysis because of an absence of ECG manifestations of Brugada syndrome at the time of the tests. A history of life-threatening events defined as syncope and aborted sudden death was present in 19 of 33 patients (58%); in 15 of the 19 patients, stimulation induced ventricular fibrillation or polymorphic ventricular tachycardia. The LP were present in 24 of 33 patients (73%); TWA were present in 5 of 31 patients (16%); and a QTD >50 ms was present in 9 of 33 patients (27%). The incidence of LP in Brugada patients was significantly (p < 0.0001) higher than in the controls, whereas incidences of TWA and QTD were not significantly different. Multivariate logistic regression analysis revealed that the presence of LP had the most significant correlation to the occurrence of life-threatening events (p = 0.006). CONCLUSIONS Late potentials are a noninvasive risk stratifier in patients with Brugada syndrome. These results may support the idea that conduction disturbance per se is arrhythmogenic.

Combined assessment of T-wave alternans and late potentials used to predict arrhythmic events after myocardial infarction ☆: A prospective study

OBJECTIVES The aim of the present study was to determine whether the combination of two markers that reflect depolarization and repolarization abnormalities can predict future arrhythmic events after acute myocardial infarction (MI). BACKGROUND Although various noninvasive markers have been used to predict arrhythmic events after MI, the positive predictive value of the markers remains low. METHODS We prospectively assessed T-wave alternans (TWA) and late potentials (LP) by signal-averaged electrocardiogram (ECG) and ejection fraction (EF) in 102 patients with successful determination results after acute MI. The TWA was analyzed using the power-spectral method during supine bicycle exercise testing. No antiarrhythmic drugs were used during the follow-up period. The study end point was the documentation of ventricular arrhythmias. RESULTS The TWA was present in 50 patients (49%), LP present in 21 patients (21%), and an EF <40% in 28 patients (27%). During a follow-up period of 13 +/- 6 months, symptomatic, sustained ventricular tachycardia or ventricular fibrillation occurred in 15 patients (15%). The event rates were significantly higher in patients with TWA, LP, or an abnormal EF. The sensitivity and the negative predictive value of TWA in predicting arrhythmic events were very high (93% and 98%, respectively), whereas its positive predictive value (28%) was lower than those for LP and EF. The highest positive predictive value (50%) was obtained when TWA and LP were combined. CONCLUSIONS The combined assessment of TWA and LP was associated with a high positive predictive value for an arrhythmic event after acute MI. Therefore, it could be a useful index to identify patients at high risk of arrhythmic events.

Noninvasive Risk Stratification of Subjects with a Brugada-Type Electrocardiogram and No History of Cardiac Arrest

Background: Recent studies suggest that the Brugada‐type electrocardiogram (ECG) is much more prevalent than the manifest Brugada syndrome. Although invasive electrophysiologic investigations have been proposed as a risk stratifier, their value is controversial, and alternative noninvasive techniques may be preferred. We sought a noninvasive strategy to detect a high‐risk group in a long‐term follow‐up study of subjects with a Brugada‐type ECG, and no history of cardiac arrest.

Relationship Between ST-Segment Morphology and Conduction Disturbances Detected by Signal-Averaged Electrocardiography in Brugada Syndrome

Background: Although arrhythmogenesis of Brugada syndrome is still unknown, it has been reported to be associated with conduction disturbances. Two ST‐segment morphologies (coved and saddle‐back patterns) have been described in this syndrome. No study has sought to determine which morphology has stronger conduction disturbances, thereby associating with life‐threatening events.

Predicting the recurrence of ventricular tachyarrhythmias from T-wave alternans assessed on antiarrhythmic pharmacotherapy : A prospective study in patients with dilated cardiomyopathy

Background: Microvolt T‐wave alternans (TWA) has been proposed as a useful index to identify patients at risk of ventricular tachyarrhythmias. Recent studies have demonstrated that antiarrhythmic drugs, such as amiodarone and procainamide, decrease the prevalence of TWA. In this study, we tested whether TWA in patients on antiarrhythmic pharmacotherapy significantly predicts the recurrence of ventricular tachyarrhythmias in patients with dilated cardiomyopathy.

Time course for resolution of left atrial appendage stunning after catheter ablation of chronic atrial flutter.

OBJECTIVES This study assessed the time course of resolution of left atrial appendage (LAA) stunning after catheter ablation of chronic atrial flutter (AFL). BACKGROUND Although the presence of LAA stunning after ablation of chronic AFL calls for anticoagulation in the post-cardioversion period, limited information has been obtained, particularly regarding its duration. METHODS Sixteen patients who underwent ablation of chronic, pure AFL were studied, only five of whom had structural heart disease and one of whom had a reduced left ventricular ejection fraction. The LAA emptying velocities (LAAEV) and left atrial spontaneous echo contrast (SEC) were assessed using transesophageal echocardiography before, within 24 h after, one week after, and two weeks after ablation. RESULTS Within 24 h after ablation, the LAAEV decreased from 39 +/- 10 cm/s during AFL to 21 +/- 10 cm/s during sinus rhythm (p < 0.01), with eight patients (50%) having documented SEC. After one week, the LAAEV increased (39 +/- 17 cm/s, p < 0.01 vs. within 24 h) and SEC resolved in five of eight patients. After two weeks, the increase in LAAEV persisted (54 +/- 14 cm/s, p < 0.01 vs. 1 week) and SEC was no longer present in any of the patients. The numbers of patients with LAAEV >30 cm/s and absence of SEC were three within 24 h, 11 at one week, and 16 at two weeks after ablation. CONCLUSIONS Patients with chronic, pure AFL and preserved left ventricular function who will undergo catheter ablation may not require anticoagulation therapy for more than two weeks after the procedure because of the presence of forceful mechanical LAA contractions and the absence of SEC.

Effective prediction of response to cardiac resynchronization therapy using a novel program of gated myocardial perfusion single photon emission computed tomography

AIMS The limitation of QRS duration as a surrogate measure for left ventricular (LV) mechanical dyssynchrony (LVMD) in cardiac resynchronization therapy (CRT) patient selection encourages seeking alternatives to QRS duration. Exploring the potential of an analysis program of electrocardiographically gated myocardial perfusion single photon emission computed tomography (SPECT) (GMPS) for the estimation of LVMD to predict CRT response. METHODS AND RESULTS Twenty-four patients undergoing CRT for advanced heart failure caused by non-ischaemic cardiomyopathy were studied. Gated myocardial perfusion single photon emission computed tomographies were performed in the setting of temporary CRT suspension after 1 week of CRT adoption. The GMPS data were computed with a novel program capable of segmental LV time-volume analysis. When a brain natriuretic peptide (BNP) value decreased >50% at 6-month follow-up, the patient was defined as a CRT responder. Receiver operating characteristic (ROC) curves for identification of responders were analysed for standard deviation of time to end systole (TES-SD) among 17 LV segments. Linear regression analyses demonstrated that an increase in percentage reduction in BNP level at 6-month follow-up was predicted by an increase in TES-SD (R(2) = 0.21, P = 0.023). The TES-SD in responders (n = 15, 62.5%) was higher than that in non-responders (100 ± 51 vs. 41 ± 17 ms, P = 0.0008). A cutoff value of TES-SD >49 ms predicted responders with 100% sensitivity and 78.8% specificity and the area under the ROC curve was 0.881 for TES-SD (P = 0.002). CONCLUSIONS The estimation of LVMD using this novel GMPS program could be an alternative or a complementary approach to QRS duration in CRT patient selection. This finding warrants further assessment of our approach in larger studies.

Elimination of non-pulmonary vein ectopy by ethanol infusion in the vein of Marshall

Introduction Myocardial fibers and nerves adjacent to the vein of Marshall (VOM), that is, the ligament of Marshall (LOM), have been implicated as a source of ectopic beats initiating paroxysmal atrial fibrillation (AF), as a connection pathway between the left atrium (LA) and left pulmonary veins (PVs), and as a source of arrhythmogenic autonomic innervation. This various complex nature of the LOM can constitute the genesis of AF. On the other hand, the VOM location coincides with the areas usually ablated during PV isolation. It has recently been reported that VOM ethanol infusion creates a lowvoltage area in the LA adjacent to the VOM and facilitates left PV isolation for AF ablation. This advocates that VOM ethanol infusion has favorable adjunctive effects on PV isolation by radiofrequency (RF) ablation. However, considering the roles that the LOM plays in the pathogenesis of AF, VOM ethanol infusion alone may cure AF in some patients. In this report, we describe the first case that underwent VOM ethanol infusion and had non-PV ectopy initiating AF that is eliminated without RF ablation for PV isolation.

Paradoxical undersensing of atrial electrograms during atrial fibrillation due to repeated activation of the quiet timer blanking interval: Case report and review of the literature

This report describes a case of paradoxical atrial undersensing by a dual‐chamber pacemaker during paroxysmal atrial fibrillation. Undersensing of 5.6 mV atrial signals at a programmed sensitivity of 0.5 mV returned to normal sensing by decreasing atrial sensitivity to 1.0 mV. This uncommon phenomenon can be explained by a repeated activation of the quiet timer blanking interval. Knowledge of this phenomenon is important in the current pacemaker management to improve the accuracy of the diagnostic feature for atrial tachyarrhythmia burden and to avoid unnecessary lead revisions.

Detection of regional low myocardial perfusion helps predict a response to cardiac resynchronization therapy in patients with non-ischemic cardiomyopathy: Results of the Find Index by Nuclear Imaging for Dyssynchrony (FIND) study

The aim of this study was to investigate the use of imaging techniques to predict the response to cardiac resynchronization therapy (CRT) in patients with non‐ischemic cardiomyopathy (NICM) by simultaneous assessment of left ventricular (LV) dyssynchrony and myocardial perfusion in a single nuclear scan of the heart.