Atsuko Abe

The Full Stomach Test as a Novel Diagnostic Technique for Identifying Patients at Risk of Brugada Syndrome

Introduction: Autonomic modulation, particularly high vagal tone, plays an important role in the occurrence of ventricular tachyarrhythmias in the Brugada syndrome. Food intake modulates vagal activity. We assessed the usefulness of a novel diagnostic technique, the “full stomach test,” for identifying a high‐risk group in patients with a Brugada‐type electrocardiogram (ECG).

Circadian variation of late potentials in idiopathic ventricular fibrillation associated with J waves: Insights into alternative pathophysiology and risk stratification

BACKGROUND The presence of J waves on ECGs is related to idiopathic ventricular fibrillation (VF). OBJECTIVE The purpose of this study was to investigate the pathophysiology of J waves by assessing risk markers that reflect electrophysiologic abnormalities. METHODS The study enrolled 22 idiopathic VF patients (17 men and 5 women; mean age 36 +/- 13 years). Patients were divided into two groups according to the presence or absence of J waves. The following risk stratifiers were assessed: late potentials (LPs; depolarization abnormality marker) for 24 hours using a newly developed signal-averaging system, and T-wave alternans and QT dispersion (repolarization abnormality markers). Frequency-domain heart rate variability (HRV), which reflects autonomic modulation, also was assessed. The results were compared to those of 30 control subjects with J waves and 30 with no J wave, matched for age and gender to the idiopathic VF patients. RESULTS J waves were present in 7 (32%) idiopathic VF patients. The incidence of LP in the idiopathic VF J-wave group was higher than in the idiopathic VF non-J-wave group (86% vs 27%, P = .02). In contrast, repolarization abnormality markers did not differ between the two groups. In the idiopathic VF J-wave group, dynamic changes in LP parameters (fQRS, RMS(40), LAS(40)) were observed and were pronounced at nighttime; this was not the case in the idiopathic VF non-J-wave group and the control J-wave group. High-frequency components (vagal tone index) on frequency-domain HRV analysis were associated with J waves in idiopathic VF patients (P < .05). CONCLUSION Idiopathic VF patients with J waves had a high incidence of LP showing circadian variation with night ascendancy. J waves may be more closely associated with depolarization abnormality and autonomic modulation than with repolarization abnormality.

Time-domain T-wave alternans measured from Holter electrocardiograms predicts cardiac mortality in patients with left ventricular dysfunction: A prospective study

BACKGROUND Time-domain T-wave alternans (TWA) is useful for identifying patients at risk for serious events after myocardial infarction. OBJECTIVE The purpose of this study was to prospectively evaluate the utility of time-domain TWA measured from Holter ECGs in predicting cardiac mortality in patients with left ventricular (LV) dysfunction. METHODS Two hundred ninety-five consecutive patients with LV dysfunction were enrolled in the study. Patients were divided into two groups: the ischemic group (n = 195) and the nonischemic group (n = 100). Time-domain TWA was assessed using the modified moving average method from routine 24-hour Holter ECGs recorded during daily activity. The maximal time-domain TWA voltage at heart rate <or=120 bpm in either lead V(5) or V(1) was derived and its value defined as positive when the voltage was >or=65 microV. The primary end-point was defined as cardiac mortality. RESULTS Mean maximal time-domain TWA voltage was 54 +/- 16 microV. During follow-up of 390 +/- 212 days, 27 patients (17 in the ischemic group and 10 in the nonischemic group) died of cardiac causes. Fifty-three patients (18%) were time-domain TWA positive and 242 (82%) were time-domain TWA negative. Univariate Cox proportional hazards analyses revealed that older age, New York Heart Association functional class III or IV, diabetes, renal dysfunction, nonsustained ventricular tachycardia, and time-domain TWA were associated with cardiac mortality. In multivariate analysis, time-domain TWA had the most significant value (hazard ratio = 17.1, P <.0001). This index also was significant in both subgroups (ischemic group: hazard ratio = 19.0, P <.0001; nonischemic group: hazard ratio = 12.3, P = .002). CONCLUSION Time-domain TWA measured from 24-hour Holter ECGs predicts cardiac mortality in patients with ischemic and nonischemic LV dysfunction.

Comparison of late potentials for 24 hours between Brugada syndrome and arrhythmogenic right ventricular cardiomyopathy using a novel signal-averaging system based on Holter ECG.

Background— Late potentials (LP) detected with signal-averaged ECGs are known to be useful in identifying patients at risk of Brugada syndrome (BS) and arrhythmogenic right ventricular cardiomyopathy (ARVC). Because the pathophysiology is clearly different between these disorders, we clarified the LP characteristics of these disorders. Methods and Results— This study included 15 BS and 12 ARVC patients and 20 healthy controls. All BS patients had characteristic ECG changes and symptomatic episodes. All ARVC patients had findings that were consistent with recent criteria. Three LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) were continuously measured for 24 hours using a novel Holter-based signal-averaged ECG system. The incidences of LP determination in BS (80%) and ARVC (91%) patients were higher than in healthy controls (5%; P<0.0001 in both) but did not differ between BS and ARVC patients. In BS patients, the dynamic changes of all LP parameters were observed, and they were pronounced at nighttime. On the contrary, these findings were not observed in ARVC patients. When the SD values of the 3 LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) over 24 hours were compared for the 2 patient groups, those values in BS patients were significantly greater than those in ARVC patients (P<0.0001 in all). Conclusions— LP characteristics detected by the Holter-based signal-averaged ECG system over 24 hours differ between BS and ARVC patients. Dynamic daily variations of LPs were seen only in BS patients. This may imply that mechanisms of lethal ventricular arrhythmia in BS may be more correlated with autonomic abnormality than that of ARVC.

Quantitative assessment of cibenzoline administration for vagally mediated paroxysmal atrial fibrillation using frequency-domain heart rate variability analysis

BACKGROUND Cibenzoline (CBZ), a class I antiarrhythmic drug, has been widely used to maintain sinus rhythm in patients with paroxysmal atrial fibrillation (P-AF). This agent has an anticholinergic action and will become the drug of first choice for vagally mediated P-AF. We assessed its efficacy quantitatively by analyzing the frequency-domain heart rate variability (FD-HRV) of the Holter electrocardiogram (ECG) in patients with vagal P-AF. METHODS We enrolled 65 consecutive patients with vagal P-AF, but 31 patients were excluded because of the occurrence of significant arrhythmias during the 24-h Holter recordings. Accordingly, CBZ was administered to the remaining 34 patients. After administration, a Holter ECG recording was made again. High frequency (HF) components, i.e., vagal tone index, on the FD-HRV analysis from 00:00 h to 06:00 h were used for assessment. In 14 patients, the treatment was changed to disopyramide (DSP) and the same analyses were performed. RESULTS In two patients, the FD-HRV analysis was not utilized after administration. Finally, 32 patients were available for evaluation. CBZ was considered effective for vagal P-AF in 24 patients (75%). After administration, the HF component levels decreased (1589+/-795 ms(2) vs. 850+/-524 ms(2), p<0.0001). Comparison of the pre-administration HF component levels between the CBZ-responsive group and the CBZ-non-responsive group showed higher levels in the CBZ-responsive group (1766+/-758 ms(2) vs. 1058+/-690 ms(2), p=0.026). Although no significant difference in the reduction of the HF component levels was found between CBZ and DSP, DSP had anticholinergic side effects in two patients (14%). CONCLUSIONS In vagal P-AF patients, larger HF components on the FD-HRV analysis could be a hallmark of the antiarrhythmic action of CBZ. The reduction in the HF component levels after drug administration is useful for a quantitative assessment of anticholinergic action.

Usefulness of heart rate turbulence for predicting cardiac events in patients with nonischemic dilated cardiomyopathy

BACKGROUND Few studies have described the clinical value of heart rate turbulence (HRT), an autonomic risk stratification index, in stratifying patients with nonischemic dilated cardiomyopathy (NIDCM). We prospectively assessed the utility of HRT for cardiac events in patients with NIDCM. METHODS We enrolled 134 consecutive patients with NIDCM. Heart rate turbulence was automatically measured using an algorithm based on 24-hour Holter electrocardiograms. In addition to HRT, other risk indices such as a reduced left ventricular ejection fraction of 30% or less, the presence of nonsustained ventricular tachycardia (VT), the use of medical treatment, and so on were assessed as well. The primary end point was defined as cardiac mortality and sustained VTs. RESULTS Of the patients enrolled, 106 (79%) were used for HRT assessment. Heart rate turbulence was determined as positive in 26 patients (25%) and negative in 80 patients (75%). During a follow-up of 445 ± 216 days, 23 patients (23%) reached the primary end point. Among indices, documented presence of nonsustained VT and an HRT-positive outcome had significant values with the primary end point (P = .02 and P = .0001, respectively). On multivariate analysis, an HRT-positive outcome was the most significant predictor, with a hazard ratio of 4.5 (95% confidence interval, 2.0-10.4; P = .0004). CONCLUSIONS Heart rate turbulence is a powerful risk stratification index for cardiac events defined as cardiac mortality and sustained VTs in patients with NIDCM.

Prevalence and prognosis of patients with lone and paroxysmal atrial tachyarrhythmias showing Brugada-type electrocardiograms after class IC antiarrhythmic drug administration but no risk-stratifying factors

Class IC antiarrhythmic drugs, used to prevent paroxysmal atrial tachyarrhythmias (ATs), are well known to effectively unmask the electrocardiogram (ECG) pattern of Brugada syndrome. We used these drugs to investigate the prevalence and prognosis of patients with lone and paroxysmal ATs and Brugada‐type ECGs.