大坂 元久

Background The nature and significance of the frequency characteristics of the surface electrocardiogram (ECG) in patients with persistent atrial fibrillation (AF) undergoing radiofrequency ablation are unclear. Methods Preablation surface and intracardiac ECGs were obtained using offline fast Fourier transform (FFT) analysis in 40 patients with persistent AF. For the FFT analysis of the surface f-wave, the QRS-T complex was canceled utilizing a template subtraction algorithm. The ablation procedure included isolation of the pulmonary veins (PV) and posterior left atrium and linear ablation of the mitral isthmus and additional lesions using a stepwise approach. Results The dominant frequency (DF) of all the intracardiac signals, except for the left inferior PV, had a significant correlation with the DFs from the surface electrocardiogram. The strongest correlation was observed between the DFs of the left atrial appendage (LAA) and those on the limb leads (correlation coefficient, 0.802-0.882, P&lt 0.001) and between the DFs on the right atrial appendage and those on lead V1 (correlation coefficient, 0.86, P&lt 0.0001). After radiofrequency ablation, AF was terminated in 23 patients and persisted in the remaining 17. The best electrographic predictor of AF termination was the DFs in the LAA (DF&lt 6.5 Hz, sensitivity 75%, specificity 86%) and lead II (DF&lt 5.9 Hz, sensitivity 82%, specificity 78%), respectively. Conclusions The frequency characteristics of the surface ECG correlated with those of the intracardiac signals, and the DF predicted termination of AF during radiofrequency ablation in patients with persistent AF.

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 Hotter recordings of 132 patients enrolled from 41 institutions who either died (n = 88) or had an aborted death (n = 44). The Hotter 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 tachyarrhythmiarelated 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.

Aims The level of circulating soluble elastin (CSE) is reported to increase proportionally with the degree of clinical atherosclerosis; however, its diagnostic use is limited because CSE also increases with age. We aimed to investigate whether alterations in CSE concentrations are implicated in potential cardiovascular dysfunctions (indicated by standard physiological parameters) in medical check-up individuals, taking age into consideration. Methods In a total of 531 individuals (age 20-89 years), CSE levels were correlated most significantly with age. The groups of male and female individuals were each further divided into two subgroups: those with higher and those with lower CSE levels than the reference values determined by polynomial regression. Results Male participants with lower CSE levels (n = 128) than the age-adjusted reference baseline levels showed higher serum glucose (P < 0.008), uric acid (P < 0.008) and triglyceride (P < 0.02) levels than those with higher CSE levels (n = 126). However, most of the parameters tested in female participants with lower CSE levels (n = 140) were statistically comparable to those with higher CSE levels (n = 137). The ratio of CSE level to the age-adjusted reference level was calculated in each of the male participants, and declines in the ratio were significantly correlated with increases of serum glucose, uric acid and triglyceride levels (P < 0.005, P P < 0.006, respectively). Conclusion The decrease in age-adjusted CSE levels is a potential indicator of eventual cardiovascular dysfunction in medical check-up individuals, as predicted by the risk factors dyslipidemia, hyperuricemia or diabetes.

The FitzHugh-Nagumo model of nerve conduction is also used as a model of cardiac excitability. We propose the replacement of a gating variable of the conductance of K+ current with Ca2+ current as a slow variable of the model, in which plays a key role in the cardiac action potential. Since ion currents conduct transversely as well as longitudinally through gap junctions between myocytes, particularly in ischemia, a respective diffusion term is involved to both equations of a fast variable and a slow variable. We show that only a small increase of a coefficient of the diffusion term of Ca2+ current may cause cardiac instabilities, which are presumed to cause breakup of conduction and finally a lethal arrhythmia, ventricular fibrillation. Particularly, these instabilities do not occur without the diffusion term of Ca2+ current. © 2013 American Institute of Physics.

Accentuated sympathetic nerve activity (SNA) is a risk factor for cardiovascular events. In this review, we investigate our working hypothesis that potentiated activity of neurons in the rostral ventrolateral medulla (RVLM) is the primary cause of experimental and essential hypertension. Over the past decade, we have examined how RVLM neurons regulate peripheral SNA, how the sympathetic and renin-angiotensin systems are correlated and how the sympathetic system can be suppressed to prevent cardiovascular events in patients. Based on results of whole-cell patch-clamp studies, we report that angiotensin II (Ang II) potentiated the activity of RVLM neurons, a sympathetic nervous center, whereas Ang II receptor blocker (ARB) reduced RVLM activities. Our optical imaging demonstrated that a longitudinal rostrocaudal column, including the RVLM and the caudal end of ventrolateral medulla, acts as a sympathetic center. By organizing and analyzing these data, we hope to develop therapies for reducing SNA in our patients. Recently, 2-year depressor effects were obtained by a single procedure of renal nerve ablation in patients with essential hypertension. The ablation injured not only the efferent renal sympathetic nerves but also the afferent renal nerves and led to reduced activities of the hypothalamus, RVLM neurons and efferent systemic sympathetic nerves. These clinical results stress the importance of the RVLM neurons in blood pressure regulation. We expect renal nerve ablation to be an effective treatment for congestive heart failure and chronic kidney disease, such as diabetic nephropathy. Hypertension Research (2012) 35, 132-141; doi:10.1038/hr.2011.208; published online 15 December 2011

The aim was to propose techniques for analysis of spatiotemporal patterns of vehicle collisions with an endangered species. We examined Iriomote cat-vehicle collisions from 1978-2008 (n＝46) along only a 50-km trunk road in the Iriomote island of Japan. The collisions obeyed a nonhomoge-neous Poisson process with mean λ(t) that increased with time t. Hence, the collisions turned out to be increasing steadily. To test for spatial distribution, the road was divided into 500 segments. We assumed a null hypothesis that each collision occurred with the same probability on each of the seg-ments. We generated 1000 samples, each of which consisted of 46 randomly selected segments, and counted clusters of various sizes. We defi ned a cluster as collisions 4 (size 4) within 1 km. The results were 1.544/sample for size 4, 0.349/sample for size 5, 0.054/sample for size 6, and 0.008/sam-ple for size 7. The real distribution had 1 cluster of size 4, 2 clusters of size 5 and 2 clusters of size 7 (P＜0.001). In the almost all of these clusters, it have already paid for many eff ort to prevent cat-vehicle collision such as underpasses, elevated segments of the road and zebra zone, our fi ndings suggest that it is reasonable statistically. Because the situation around the cat-vehicle collisions, such as road structure, traffic volume and habitat condition of the cat along the road, has been changed, we think also that it is necessary to examine further analysis using additional data to sug-gest the measurement against collision eff ectively.

Recently we have reported that a previously unidentified V-trough of sympathetic nerve activity (SNA) is a potential precursor of lethal cardiac events by examining 24-hour ambulatory electrocardiograms in which such an event was recorded by chance. The V-trough was marked by three consecutive compartments: a small variation lasting two hours, an abrupt descent lasting 30 min and a sharp ascent for 40 min. We reported that the hemodynamics consisting of heart rate, SNA and blood pressure (BP) is modeled excellently by the modification of a known chaotic electrical circuit, Chua circuit. A V-trough of SNA appears by increasing the resistive element between SNA and BP in the circuit, which corresponds to the impaired regulation of BP by SNA. This finding is consistent with an acknowledged finding that the depressed baroreflex (reflex of BP by SNA) may trigger a lethal arrhythmia.