Naoki Tezuka

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.

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.

Differences in left ventricular dyssynchrony between high septal pacing and apical pacing in patients with normal left ventricular systolic function.

BACKGROUND AND PURPOSE Permanent right ventricular apical pacing can result in heart failure due to ventricular mechanical dyssynchrony. The purpose of the study was to define differences in left ventricular dyssynchrony between high septal pacing and apical pacing using tissue Doppler imaging (TDI) and two-dimensional (2D) speckle-tracking echocardiography (STE). METHODS The subjects were 60 patients with normal left ventricular systolic function who underwent implantation of a permanent pacemaker. Patients were divided into two groups with high septal pacing (n=36) and conventional right apical pacing (n=24). Left ventricular dyssynchrony was measured using TDI and 2D-STE. The time difference (TD) between the earliest and latest activated segments obtained from each systolic velocity curve by TDI was defined as TD-TDI. The time differences obtained from systolic strain curves obtained by 2D-STE were defined as TD-RS for radial strain, TD-CS for circumferential strain, and TD-LS for longitudinal strain. RESULTS The high septal pacing group had significantly shorter TD-TDI (20.0+/-24.3ms vs. 59.7+/-43.0ms, p<0.0001), TD-RS (13.5+/-19.9ms vs. 45.8+/-24.6ms, p<0.0001), and TD-LS (42.7+/-22.0ms vs. 66.6+/-26.8ms, p=0.001) values compared to the apical pacing group. There was no significant difference in TD-CS between the two groups. CONCLUSION Left ventricular dyssynchrony was smaller in patients with high septal pacing. The results show that 2D-STE is useful for detection of differences in left ventricular mechanical dyssynchrony in patients with permanent pacemaker implantation, in addition to TDI.

Optimal Right Ventricular Pacing Site from the Perspective of QRS Duration, Heart Function and the Configuration of 12-lead Electrocardiogram

Introduction: It has become clear that the onset of heart failure is closely linked to right apex pacing, which lengthens the QRS duration and evokes discoordinate contraction of the left ventricle (LV). Currently, it is thought that the site inducing the shortest QRS duration is optimal for pacing.

Pharmacological Treatment for Atrial Fibrillation

Pharmacological treatment for atrial fibrillation has a variety of purposes, such as pharmacological defibrillation, maintenance of sinus rhythm, heart rate control to prevent congestive heart failure and prevention of both cerebral infarction and atrial remodeling. Sodium channel blockers are superior to potassium channel blockers for atrial defibrillation, while both sodium and potassium channel blockers are effective in the maintenance of sinus rhythm. In general, digitalis or Ca antagonists are used to control heart rate during atrial fibrillation to prevent congestive heart failure, while amiodarone or bepridil also reduce heart rates during atrial fibrillation. Anticoagulant therapy with warfarin is recommended to prevent cerebral infarction and angiotensin converting enzyme antagonists or angiotensin II receptor blockers are also used to prevent atrial remodeling. One should select appropriate drugs for treatment of atrial fibrillation according to the patient’s condition. (J Arrhythmia 2005; 21: 358–371)