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Background: T-wave alternans based on the modified moving average method (MMA-TWA) and heart rate turbulence (HRT) have been introduced as predictors for cardiac mortality. In this study, we simultaneously recorded MMA-TWA and HRT in patients after myocardial infarction (MI) and designed a prospective observational study., Methods and Results: We prospectively enrolled 313 consecutive post-MI patients (age 70 ± 12 years, 232 men). The MMA-TWA and HRT were simultaneously measured using algorithms based on 24-h Holter ECG monitoring during daily activity. MMA-TWA was determined positive when the maximal voltage was >64 µV, and HRT was determined positive when both turbulence onset and turbulence slope were abnormal. The endpoint was defined as overall cardiac mortality and fatal arrhythmic events. MMA-TWA was positive in 14 patients (4.4%) and HRT was positive in 61 patients (19.5%). During follow-up of 1,190 ± 441 days, 28 patients (9%) reached the endpoint, including 12 patients with fatal arrhythmic events. Both MMA-TWA and HRT were significant predictors for the endpoint. On multivariate analysis, HRT had the most significant value, with a hazard ratio (HR) of 5.7 (P=0.0008). When focused on fatal arrhythmic events including sudden cardiac death, MMA-TWA had the most significant value (HR 5.8, P=0.0072)., Conclusions: The present study revealed that both MMA-TWA and HRT were significant predictors. MMA-TWA is more associated with arrhythmic events than cardiac mortality in post-MI patients.

Background: It has been reported that cardiovascular events occur more frequently in the morning than in the evening. The purpose of the present study was to assess the characteristics of out-of-hospital cardiac arrests due to cardiac cause in a 24-h period in Japanese patients., Methods and Results: Of 2,199 consecutive patients with cardiopulmonary resuscitation outside hospital, 1,293 cardiogenic patients were enrolled. The incidence of cardiac arrests was assessed as hourly data (ie, circadian variation), and investigated for differences in age, gender, and the location at onset. Cardiac arrests had an apparent circadian rhythm that was characterized by 2 long zeniths in the morning and evening. The peak was at 17:00-18:00 hours. Younger patients had more cardiac arrests in the morning than in the evening. In contrast, older patients had more events in the evening than in the morning. The circadian rhythm did not differ in gender. Regarding location, the patient's residence was the most common place for cardiac arrest. In the residence, the bathroom was associated with the evening zenith of circadian variation., Conclusions: Out-of-hospital cardiac arrests due to cardiac cause in Japanese patients have an apparent circadian variation with 2 long zeniths, with an evening predominance in older patients. Aging affects the evening zenith, in that elderly patients > or =80 years old have a zenith associated with bath time in the evening.

Background: Occasionally it is difficult to inhibit electrical storm (ES) with standard pharmacological treatment. In the present study the effect of landiolol, an ultra-short-acting beta(1)-selective blocker, on ES refractory to class III antiarrhythmic drugs was evaluated., Methods and Results: The study group comprised 42 consecutive patients who developed ES for which intravenous class III antiarrhythmic drugs, such as amiodarone and nifekalant, were ineffective. Landiolol was administered intravenously with an initial dose of 2.5 microg x kg(-1) x min(-1), which was doubled if it was ineffective, up to a maximum dose of 80 microg x kg(-1) x min(-1). Landiolol inhibited ES in 33 patients (79%) at a mean dose of 7.5+/-12.2 microg x kg(-1) x min(-1). All patients in whom landiolol was ineffective died of arrhythmia. Of the 33 patients in whom landiolol was effective, 25 survived and were discharged (60% of all patients). Landiolol significantly decreased heart rate (P<0.0001), but did not affect blood pressure. Landiolol was not discontinued for adverse effects in any of the responders. Age, APACHE II score, and pH of arterial blood gas differed significantly between the responders and nonresponders., Conclusions: Landiolol is useful as a life-saving drug for class III antiarrhythmic drug-resistant ES. The main mechanism of ES refractory to class III antiarrhythmic drugs could be abnormal automaticity but not reentry.

Background: Intravenous amiodarone (AMD) has been used for the treatment of ventricular tachycardia/fibrillation (VT/VF) in emergency care medicine. However, AMD acts slowly and is occasionally accompanied by hypotension and bradycardia. The antiarrhythmic effect of intravenous nifekalant (NIF) was assessed in patients with VT/VF complicating acute coronary syndrome (ACS) according to our study protocol., Methods and Results: Among a series of 1,143 ACS patients, 41 patients who suffered sustained VT/VF were enrolled; 19 failed to respond to a preceding lidocaine (LID) injection. NIF was given first as an intravenous bolus injection (0.2 mg/kg) and then as a continuous intravenous infusion at a relatively low dose level (0.2 mg x kg(-1) x h(-1)). Sustained VT/VF was successfully inhibited by NIF in 34 patients (83%). In subgroup analysis, NIF achieved VT/VF inhibition in 79% of patients who received preceding LID and in 86% of patients who received direct NIF. There were no significant changes in systolic blood pressure or heart rate following NIF therapy. A corrected QT interval was significantly prolonged (P<0.01), whereas torsade de pointes developed in only 1 patient (2%)., Conclusions: An intravenous bolus injection and subsequent continuous infusion of NIF at a relatively low dosage were effective in treating severe ventricular tachyarrhythmias complicating ACS, reducing the potential risk of proarrhythmia.

Sudden cardiac death (SCD) is a leading cause of mortality in industrialized countries, and ventricular fibrillation and sustained ventricular tachycardia are the major causes of SCD. Although there are now effective devices and medications that can prevent such serious arrhythmias, it is crucial to have methods of identifying patients at risk. Numerous studies suggest that most patients dying of SCD have coronary artery disease or cardiomyopathy. Functional or electrophysiological measurements are effective in risk stratification. Left ventricular ejection fraction measured by echocardiography or cardiac imaging techniques is the gold standard to detect high-risk patients. Electrophysiological studies have also been used for risk stratification. Noninvasive techniques and measurements, such as T-wave alternans, signal-averaged electrocardiography, nonsustained ventricular tachycardia, heart rate variability, and heart rate turbulence, have been proposed as useful tools in identifying patients at risk for SCD. This article reviews the epidemiology, mechanisms, substrates, and current status of risk stratification of SCD.