Masayuki Yotsukura

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).

Relation of ST-Segment Changes in Inferior Leads During Anterior Wall Acute Myocardial Infarction to Length and Occlusion Site of the Left Anterior Descending Coronary Artery

We investigated the relation between left anterior descending (LAD) coronary artery morphology and inferior lead ST-segment changes to elucidate the clinical significance of such changes in 159 patients with anterior wall acute myocardial infarction (AMI). Patients with 1-vessel LAD artery lesions were divided into an ST depression group (n = 40), an ST elevation group (n = 25), and a no-ST-change group (n = 94) based on ST-segment changes in the inferior leads. The relation between each group and the infarct-related lesion and the presence of a wrapped LAD artery was then investigated. The percentage of patients with the infarct-related lesion in the proximal LAD artery was significantly higher in the ST depression group and significantly lower in the ST elevation group. The percentage of patients with a wrapped LAD artery was significantly higher in the ST elevation group and significantly lower in the ST depression group. The wall motion index determined echocardiographically was significantly higher in the ST depression group and the no-ST-change group than in the ST elevation group. Our findings suggest that inferior lead ST-segment changes during anterior wall AMI arise as a result of competition between reciprocal changes caused by high lateral wall AMI due to lesions of the proximal LAD artery, which depress the ST segment, and inferoapical wall AMI due to a wrapped LAD artery, which elevates the ST segment. In patients with no ST-segment changes, echocardiography was useful for distinguishing the amount of affected LAD artery territory.

Circadian rhythm and variability of heart rate in Duchenne-type progressive muscular dystrophy

Using 24-hour Holter monitoring and time domain and power spectral measurements, we evaluated the variability of the heart rate and its circadian rhythm in 55 male patients with Duchenne-type progressive muscular dystrophy (DMD) to characterize their autonomic function versus findings in 20 normal controls. Comparisons were also made in patients with mild, moderate, and severe stages of DMD. The percent difference between successive RR intervals that exceeded 50 ms, a measure of parasympathetic tone, was significantly lower even in patients with early stage of DMD than in controls (p < 0.01). This trend became marked with disease progression. Power in the high-frequency (HF) range (0.15 to 0.40 Hz), a measure of parasympathetic tone, was lower (p < 0.01), and the ratio of the power in the low-frequency (LF) range (0.04 to 0.15 Hz) and that of HF range (LF/HF ratio), a measure of sympathetic tone, was higher in DMD patients versus controls (p < 0.01). This trend was also marked with disease progression. Patients with mild or moderate disease had a slight circadian alteration in HF and LF/HF ratio. Patients with severe disease had virtually no circadian rhythm in HF. Their LF/HF ratio was higher at night (p < 0.01), lower in the morning (p < 0.01), and still lower during the day (p < 0.01), the opposite of control findings. The autonomic abnormalities in DMD were thus characterized by a significant increase in sympathetic activity and a significant decrease in parasympathetic activity. Thus, heart rate variability and circadian rhythm were useful in assessing autonomic dysfunction in DMD.

Heart rate variability during the first month of smoking cessation

BACKGROUND Heart rate variability (HRV) is known to increase after smoking cessation. However, no work has been performed concerning HRV immediately after smoking cessation. METHODS AND RESULTS We studied HRV before and from 1 day to 1 month after smoking cessation and also determined whether there is a relation between HRV and the withdrawal syndrome immediately after smoking cessation. We determined HRV by using a two-channel 24-hour ambulatory ECG system before and 1, 2, 3, 7, 14, 21, and 28 days after smoking cessation in 20 healthy male volunteers who had smoked one or more packs per day for 2 or more years. One day after smoking cessation, heart rate decreased significantly, and all 24-hour time and frequency domain indices of HRV increased except the standard deviations of the normal R-R intervals and the 5-minute mean R-R. The magnitude of increase in these indices peaked 2 to 7 days after smoking cessation and gradually decreased thereafter. The increase in HRV persisted 1 month after smoking cessation. In the 16 subjects with signs of withdrawal syndrome and in the four subjects without evidence of withdrawal before and immediately and 1 month after smoking cessation, HRV increased immediately after smoking cessation and remained elevated after 1 month. CONCLUSIONS HRV increases immediately after smoking cessation and gradually declines thereafter, which suggests that the effect of smoking on autonomic activity rapidly disappears immediately after smoking cessation. HRV remained unaffected by the presence or absence of the withdrawal syndrome.

Usefulness of P-Wave Dispersion in Standard Twelve-Lead Electrocardiography to Predict Transition from Paroxysmal to Persistent Atrial Fibrillation

A prospective study was conducted to investigate the validity of the hypothesis that P-wave dispersion (Pd) may be a clinically useful predictor of progression from paroxysmal to persistent atrial fibrillation (AF). Two hundred four consecutive patients with a diagnosis of paroxysmal AF were studied. Standard 12-lead electrocardiography and echocardiography were performed on all patients at the time of entry into the study. Pd was measured as the difference between maximum and minimum P-wave duration in any of the 12 leads. Mean follow-up was 66 +/- 8 months. Group I included patients (n = 132) in whom paroxysmal AF did not progress to persistent AF, and group II included those (n = 72) who developed persistent AF. In group II, age, percentage of men, percentage of patients with diabetes mellitus, maximum P-wave duration, Pd, and left atrial dimension were significantly higher than in group I (p <0.05). Multivariate logistic regression analysis using these 6 factors identified age (odds ratio 2.18, 95% confidence interval 1.41 to 3.41, p <0.01) and Pd (odds ratio 1.91, 95% confidence interval 1.51 to 2.44, p <0.01) as independent predictors of a transition to persistent AF. Pd >or=40 ms predicted progression to persistent AF with sensitivity of 71%, specificity of 77%, positive predictive value of 63%, negative predictive value of 83%, and accuracy of 75%. In conclusion, Pd was a clinically useful predictor of progression from paroxysmal to persistent AF.

The prevalence and prognostic significance of arrhythmias in Duchenne type muscular dystrophy

To investigate the prevalence and prognostic significance of cardiac arrhythmias in Duchenne type muscular dystrophy 24-hour ambulatory ECG was performed in 80 patients with Duchenne type muscular dystrophy, and they were followed up for 5 years. Various arrhythmias were observed in 63.8% (51 of 80) of the patients. Ventricular premature beats were found in 30% (24 of 80), and the incidence of ventricular premature beats increased as the clinical severity of skeletal muscle involvement advanced. Forty-seven patients survived for 5 years, but the incidence of arrhythmias increased from 38.3% (18 of 47) to 74.5% (35 of 47) (p < 0.001). During the 5-year period, four of 33 deaths were sudden. Malignant ventricular premature beats (ventricular couplets, ventricular tachycardia, and R-on-T-type ventricular premature beats) were observed in three of these four patients. It appears that cardiac arrhythmias are a common complication of Duchenne type muscular dystrophy and that the incidence of ventricular arrhythmias increases with the progression of myocardial involvement. There is an association between ventricular arrhythmias and sudden death, but the reduction of ventricular arrhythmias may not reduce the incidence of episodes of sudden death.

A new coronary artery disease index of treadmill exercise electrocardiograms based on the step-up diagnostic method

Treadmill exercise electrocardiography (ECG) is one of the most common noninvasive methods for detecting ischemic heart disease. However, this method has problems due to false-positive and false-negative results in a significant number of patients. The aim of this study was to determine whether the diagnostic accuracy of treadmill exercise ECG for detecting significant coronary stenosis can be improved by employing a step-up diagnostic method using multiple diagnostic indicators. We studied 273 consecutive patients (mean age, 56 +/- 9 years; 190 men and 83 women) without a history of myocardial infarction who underwent treadmill exercise ECG and coronary angiography for ischemic chest pain. Of these, 146 patients had no significant coronary stenosis, 61 had single-vessel disease, 56 had multivessel disease, and 10 patients had left main truncus disease. A multivariate logistic regression analysis was used to select 3 treadmill exercise electrocardiographic parameters that were independent predictors of the presence or absence of significant coronary stenosis: exercise-induced maximum ST-segment depression, QT dispersion immediately after exercise, and Athens QRS score. Significant coronary stenosis was diagnosed with a sensitivity of 84% and a specificity of 90% when a step-up diagnostic method using these 3 indicators was employed. These results were better than those obtained for each indicator alone (exercise-induced maximum ST-segment depression: sensitivity, 66%, and specificity, 73%; QT dispersion immediately after exercise [> or =60 ms positive]: sensitivity, 76%, and specificity, 86%; and Athens QRS score [< or =5 mm positive]: sensitivity, 72%, and specificity, 72%). We conclude that this step-up diagnostic method, using multiple diagnostic indicators, is a clinically useful predictor of the presence or absence of significant coronary stenosis.

Usefulness of QT dispersion immediately after exercise as an indicator of coronary stenosis independent of gender or exercise-induced ST-segment depression

Several recent studies suggest that QT dispersion on a standard 12-lead electrocardiogram is a clinically useful indicator of significant coronary stenosis. In this study, we compared the diagnostic accuracy of QT dispersion immediately after exercise as an indicator of coronary stenosis in men and women, and in the presence or absence of exercise-induced significant ST-segment depression. The subjects were 273 consecutive patients (mean age 56 +/- 9 years; 190 men and 83 women) without a history of myocardial infarction who underwent treadmill exercise electrocardiography and coronary angiography for evaluation of angina. Of these, 146 patients had no significant coronary stenosis, 61 had single-vessel disease, 56 had multivessel disease, and 10 had left main coronary artery disease. QT dispersion immediately after exercise was significantly greater in patients with significant coronary stenosis than in those without (64 +/- 14 vs 39 +/- 14 ms, p <0.01). QT dispersion immediately after exercise was significantly more sensitive in men (sensitivity 75%; specificity 85%) and significantly more specific in women (sensitivity 77%, specificity 88%) than exercise-induced significant ST-segment depression (men: sensitivity 62%, specificity 74%; women: sensitivity 81%, specificity 68%) as an indicator of significant coronary stenosis. The addition of factors such as gender and the presence or absence of exercise-induced significant ST-segment depression did not significantly alter the sensitivity and specificity of QT dispersion immediately after exercise for detecting significant coronary stenosis (patients with significant ST-segment depression: sensitivity 77%, specificity 88%; patients without significant ST-segment depression: sensitivity 72%, specificity 86%). In conclusion, QT dispersion immediately after exercise is a clinically useful indicator of significant coronary stenosis independent of gender or the presence or absence of exercise-induced significant ST-segment depression.

Late potentials in progressive muscular dystrophy of the Duchenne type

This study describes the late potentials (LPs) obtained by signal-averaged electrocardiography (SAECG) in 66 patients with Duchennes progressive muscular dystrophy (DMD). It also assesses the possible relationships between LPs and the severity of DMD, and the findings of two-dimensional echocardiography, as well as ventricular arrhythmias examined with the Holter system. SAECGs were performed with a Marquette MAC-1 unit. Based on Swinyard-Deavers system of stages, ranging from the mildest, S1, to the most severe, S8, one patient each could be assigned to S2 and S4, 6 to S5, 20 to S6, 21 to S7, and 17 to S8. LPs were observed in 21 of the 66 patients (32%), including 3 of the 20 assigned to S6 (15%), 10 of the 21 in S7 (48%), and 8 of the 17 in S8 (47%). The total wall motion index evaluated by the method of Hegar was significantly greater in the patients with LPs (8.4 +/- 4.4) than in those without LPs (5.8 +/- 3.1) (p less than 0.05). The incidence of LPs was found to be higher in the dilated cardiomyopathy (DCM) type (8 of 12;67%) than in the normal type (9 of 41;22%) (p less than 0.01). The incidence of ventricular premature complexes (VPCs) was significantly higher in patients with LPs (13 of 21;62%) than in those without LPs (13 of 45;29%) (p less than 0.05). No sustained ventricular tachycardia (VT) was observed, although nonsustained VT was noted in three patients with LPs. The LPs in patients with DMD were thus associated with left ventricular dysfunction, and the presence of LPs might be correlated with the extent of myocardial derangement in DMD.

Value of QT dispersion in the interpretation of treadmill exercise electrocardiograms of patients without exercise-induced chest pain or ST-segment depression

It has recently been reported that increased QT dispersion seen on standard 12-lead electrocardiograms (ECGs) reflects transient myocardial ischemia. The present study investigates whether increased QT dispersion induced by exercise is a useful indicator for detecting significant coronary stenosis in patients who do not have chest pain or significant ST-segment depression in response to exercise. We studied 135 consecutive patients (mean age +/- SD, 55 +/- 9 years; 97 men and 38 women) who complained of anginal chest pain and who did not have exercise-induced chest pain or significant ST-segment depression during treadmill exercise electrocardiography. Coronary angiography was performed in all of patients. Of the 135 patients, 97 had no significant coronary stenosis, 25 had 1-vessel coronary artery disease (CAD), and 13 had multivessel CAD. QT dispersion immediately after exercise was significantly greater in the group with significant coronary stenosis than without significant coronary stenosis (62 +/- 13 vs 40 +/- 14 ms, p <0.0001). When QT dispersion >/=60 ms immediately after exercise was considered a positive result, this indicator had a sensitivity of 74%, a specificity of 85%, and an accuracy of 81% for the diagnosis of significant coronary stenosis. In conclusion, we have shown that QT dispersion immediately after exercise is useful for detecting significant CAD in patients who do not have exercise-induced chest pain or significant ST-segment depression.