Akiko Chishaki

Prevalence of atrial fibrillation in the general population of Japan: An analysis based on periodic health examination

BACKGROUND The mortality and morbidity rates of various cardiovascular diseases differ between Western countries and Japan. The age- and gender-specific prevalence rate of atrial fibrillation (AF) in the general population of Japan was determined using the data from periodic health examinations in 2003. METHODS Data of 630,138 subjects aged 40 years or more (47% were men and 34% were employees of companies and local governments) were collected from northern to southern Japan. The prevalence of diagnosed AF in each 10-year age group of both men and women was determined. Based on these prevalence rates and the Registry of Residents, the number of people having AF in Japan was estimated. RESULTS The prevalence rate of AF increased as both male and female subjects aged, and it was 4.4% for men but only 2.2% for women aged 80 years or more (p<0.0001). As a whole, the AF prevalence of men was three times that of women (1.35 versus 0.43%, p<0.0001). There may be approximately 716,000 people (95% confidence interval (CI), 711,000-720,000) with AF in Japan, an overall prevalence of 0.56%. The number of people having AF was projected to be 1.034 (95% CI, 1.029-1.039) million, an overall prevalence of 1.09%, in 2050. CONCLUSIONS The prevalence of AF increased in Japan as the population aged, as in Western countries. The overall prevalence of AF in Japan is approximately two-thirds of that in the USA. The projected increase in the number of people having AF is modest in Japan in 2050.

Sudden cardiac arrest recorded during Holter monitoring: Prevalence, antecedent electrical events, and outcomes

BACKGROUND Causative arrhythmias of sudden cardiac arrest (SCA) are changing in this age of improved coronary care. OBJECTIVE The purpose of this study was to examine the frequency of terminal arrhythmias and the electrical events prior to SCA. METHODS We analyzed 24-hour Holter recordings of 132 patients enrolled from 41 institutions who either died (n = 88) or had an aborted death (n = 44). The Holter recordings were obtained for diagnosing and evaluating diseases and arrhythmias in those without any episodes suggestive of SCA. RESULTS In 97 patients (73%), SCA was associated with ventricular tachyarrhythmias and in 35 (27%) with bradyarrhythmias. The bradyarrhythmia-related SCA patients were older than those with a tachyarrhythmia-related SCA (70 ± 13 years vs. 58 ± 19 years, P < .001). The most common arrhythmia for a tachyarrhythmia-related SCA was ventricular tachycardia degenerating to ventricular fibrillation (45%). The bradyarrhythmia-related SCA was caused by asystole (74%) or AV block (26%). Spontaneous conversion was observed in 37 patients (38%) with ventricular tachyarrhythmias. Of those, 62% of the patients experienced symptoms including syncope, chest pain, or convulsion. Multivariate logistic analysis revealed that independent predictors of mortality for tachyarrhythmia-related SCAs were advanced age (odds ratio 1.04, 95% confidence interval 1.02-1.08) and ST elevation within the hour before SCA (odds ratio 3.54, 95% confidence interval 1.07-13.5). In contrast, the presence of preceding torsades de pointes was associated with spontaneous conversion (odds ratio 0.20, 95% confidence interval 0.05-0.66). CONCLUSION The most frequent cause of SCA remains ventricular tachyarrhythmias. Advanced age and ST elevation before SCA are risk factors for mortality in tachyarrhythmia-related SCAs.

Identification of the rate-dependent functional refractory period of the atrioventricular node in simulated atrial fibrillation

We continuously observed successive pairs of R-R intervals during atrial fibrillation and hypothesized that the shortest R-R interval for a given preceding R-R interval in a pair represents the functional refractory period of the atrioventricular node at that preceding interval. To test this hypothesis we simulated atrial fibrillation in 28 isolated cross-perfused canine hearts and obtained an R-R interval scatterplot by plotting the R-R intervals as a function of the immediately preceding R-R interval. This scatterplot enabled us to detect a series of the shortest R-R intervals for a wide range of preceding R-R intervals, and this allowed us to estimate the rate-dependent functional refractory period of the atrioventricular node in simulated atrial fibrillation. The estimated functional refractory periods correlated well with those measured by the conventional method (r = 0.93). We conclude that the proposed method makes it possible to estimate the rate-dependent functional refractory periods of the atrioventricular node in atrial fibrillation.

In vivo assessment of prevention of white-noise-induced seizure in magnesium-deficient rats by N- methyl - d - aspartate receptor blockers

The behavioral changes associated with seizures induced by auditory stimulation in magnesium (Mg)-deficient rats originate in deep brain structures and secondarily project to neocortex. In the present study, we examined the roles of N-methyl-D-aspartate (NMDA) receptors in this seizure model. The intraperitoneal administration of the competitive NMDA receptor blocker DL-2-amino-7-phosphonoheptanoic acid (36 and 72 mg/kg) and the non-competitive NMDA receptor blocker MK-801 (1.35 and 2.7 mg/kg), completely prevented the induction of seizure and bradyarrhythmia or sudden death resulting from seizure. Therefore, the white-noise-induced seizures in Mg-deficient rats are linked to increased neuronal excitability via the NMDA receptor.

Effect of cardiac function on aortic peak time and peak enhancement during coronary CT angiography

PURPOSE To examine the manner in which cardiac function affects the magnitude and timing of aortic contrast enhancement during coronary CT angiography (CTA). MATERIALS AND METHODS Twenty-nine patients (21 men, 8 women; mean age, 64.4+/-13.4 years; mean weight, 59.4+/-10.3 kg) underwent measurement of cardiac output within 2 weeks of coronary CTA. The cardiac output of each patient was measured by the thermodilution technique and the cardiac index was calculated from the body surface area. During coronary CTA, attenuation of the descending aorta was measured at the workstation every 3s. The aortic peak time (APT) and aortic peak enhancement (APE) of each patient were calculated. Pearsons correlation coefficient analysis was used to investigate the relationships between the cardiac output or cardiac index and APT or APE. Furthermore, the relationship between patient factors or parameters on test bolus injection and APT or APE was also evaluated. RESULTS The range of cardiac output, cardiac index, APT, and APE was 1.55-10.46 L/min (mean: 4.77+/-2.13), 1.11-5.30 L/(min-m(2)) (mean: 3.28+/-1.08), 25-51 s (mean: 38.3+/-7.5), and 273.1-598.1 HU (mean: 390.4+/-72.1), respectively. With an increase in the cardiac index, both APT (r=-0.698, p<0.0001) and APE (r=-0.573, p=0.0009) decreased. There were significant correlations between the patient body weight and APT and APE with the test bolus injection, and with APT and APE during coronary CTA. CONCLUSION The APT and APE during coronary CTA are closely related to cardiac function.

Case of paroxysmal atrial fibrillation improved after the administration of proton pump inhibitor for associated reflux esophagitis.

A 64-year-old man had demonstrated palpitations caused by paroxysmal atrial fibrillation (AF) documented by ambulatory electrocardiographic monitoring. Effectiveness of antiarrhythmic agent (disopyramide: 300 mg/day) was limited. Based on the gastrointestinal endoscopic findings, proton pump inhibitor (PPI: rabeprazole, 10 mg/day) was administered to eliminate heart burn due to reflux esophagitis. Symptoms of paroxysmal AF and reflux esophagitis were confusing due to the anatomical proximity of the diseased organs and concomitant occurrence in the evening and when in a supine position. After the additional PPI therapy, not only was reflux esophagitis improved subjectively and endoscopically but also paroxysms of AF markedly reduced. Because esophagus is attached to left atrial posterior wall and the role of inflammatory process on the development of AF is highlighted, amelioration of reflux esophagitis by PPI may have been followed by the remarkable reduction of paroxysms of AF.

In vivo assessment of prevention of white-noise-induced seizure in magnesium-deficient rats by N-methyl--aspartate receptor blockers

The behavioral changes associated with seizures induced by auditory stimulation in magnesium (Mg)-deficient rats originate in deep brain structures and secondarily project to neocortex. In the present study, we examined the roles of N-methyl-D-aspartate (NMDA) receptors in this seizure model. The intraperitoneal administration of the competitive NMDA receptor blocker DL-2-amino-7-phosphonoheptanoic acid (36 and 72 mg/kg) and the non-competitive NMDA receptor blocker MK-801 (1.35 and 2.7 mg/kg), completely prevented the induction of seizure and bradyarrhythmia or sudden death resulting from seizure. Therefore, the white-noise-induced seizures in Mg-deficient rats are linked to increased neuronal excitability via the NMDA receptor.

Cumulative Hypoxemia During Sleep Predicts Vascular Endothelial Dysfunction in Patients With Sleep-Disordered Breathing

BACKGROUND Sleep-disordered breathing (SDB) is associated with repeated intermittent hypoxemia, and it is known as one of the risk factors for cardiovascular diseases. Previous studies assessing the effects of frequency and depth of hypoxemia on cardiovascular diseases have shown conflicting results. The aim of the current study was to clarify what SDB-related parameters most predict endothelial dysfunction to better understand the pathogenesis of endothelial dysfunction in patients with SDB. METHODS We conducted polysomnography (PSG) and measured flow-mediated vasodilation response (%FMD) in 50 outpatients suspected of SDB. Evaluated indices included: apnea-hypopnea index (AHI), 3% oxygen desaturation index (3%ODI), averaged arterial oxygen saturation (averaged SpO2), lowest arterial oxygen saturation (lowest SpO2), ratio of arterial oxygen saturation <90% (<SpO2 90%), and averaged time desaturation summation index (TDS: [100%-averaged SpO2] × total sleep time). RESULTS Significant differences were observed only in the TDS between the first and third (P = 0.03) and between the first and forth (P = 0.04) quartile groups, stratified by %FMD. The %FMD showed a significant relationship with TDS (β = -0.47, P = 0.001), even after adjusting for confounding factors (β = -0.33, P = 0.02). In contrast, AHI, 3%ODI, averaged SpO2, lowest SpO2, and <SpO2 90% showed no significant relationships. CONCLUSIONS This study shows the validity of TDS in predicting endothelial damage in patients with SDB. Cumulative hypoxemia, rather than the frequency of hypoxemic events presented as AHI, may be a greater contributing factor in causing endothelial dysfunction. A simple index like TDS may be a useful and novel indicator of the influence of SDB on the vasculature.

Evaluation of cardiac dyssynchrony with longitudinal strain analysis in 4-chamber cine MR imaging.

PURPOSE We investigated the clinical performance of evaluation of cardiac mechanical dyssynchrony with longitudinal strain analysis using four-chamber (4CH) cine magnetic resonance imaging (MRI). MATERIALS AND METHODS We retrospectively enrolled 73 chronic heart failure patients (41 men, 32 women; mean age, 57 years, NYHA 2, 3, and 4) who underwent a cardiac MRI in the present study. The left ventricular dyssynchrony (LVD) and interventricular dyssynchrony (IVD) indices were calculated by longitudinal strain analysis using 4 CH cine MRI. The LVD and IVD indices were compared by the Wilcoxon rank-sum test between the patients with indication for cardiac resynchronization therapy (CRT) (n = 13) and without indication for CRT (n = 60), with LGE (n = 40) and without LGE (n = 27), the CRT responders (n = 8) and non-responders (n = 6), respectively. RESULTS LVD in the patients with indication for CRT were significantly longer than those without indication for CRT (LVD: 92 ± 65 vs. 28 ± 40 ms, P<.01). LVD and IVD were significantly longer in the patients with LGE than those without LGE (LVD: 54 ± 58 vs. 21 ± 30 ms, P<.01 and IVD: 51 ± 39 vs. 23 ± 34 ms, P<.01). LVD and IVD in the CRT responders were significantly longer than the CRT non-responders (LVD: 126 ± 55 vs. 62 ± 55 ms, P<.01 and IVD: 96 ± 39 vs. 52 ± 40 ms, P<.05). CONCLUSION Longitudinal strain analysis with 4CH cine MRI could be useful for clinical examination in the evaluation of cardiac mechanical dyssynchrony.

Noninvasive transcutaneous bionic baroreflex system prevents severe orthostatic hypotension in patients with spinal cord injury

Central baroreflex failure in patients with spinal cord injury results in serious orthostatic hypotension. We examined if transcutaneous electrical stimulation regulates arterial pressure in those patients. We identified skin regions capable of increasing arterial pressure and determined respective transfer function. Using the transfer function, we designed the feedback regulator (i.e., bionic baroreflex system) to control arterial pressure. Orthostatic stress decreased arterial pressure profoundly. Activation of bionic regulator restored and maintained arterial pressure at pre-specified levels. We conclude that the transcutaneous bionic system is noninvasive and capable of stabilizing arterial pressure in patients with spinal cord injury.Central baroreflex failure in patients with spinal cord injury results in serious orthostatic hypotension. We examined if transcutaneous electrical stimulation regulates arterial pressure in those patients. We identified skin regions capable of increasing arterial pressure and determined respective transfer function. Using the transfer function, we designed the feedback regulator (i.e., bionic baroreflex system) to control arterial pressure. Orthostatic stress decreased arterial pressure profoundly. Activation of bionic regulator restored and maintained arterial pressure at pre-specified levels. We conclude that the transcutaneous bionic system is noninvasive and capable of stabilizing arterial pressure in patients with spinal cord injury.