Biomedical subjects

Akihiko Shimizu

Publications and source records attributed to Akihiko Shimizu.

At least 19 recordsLinked to original sources

PubMed2007

Different effect of the pure Na+ channel-blocker pilsicainide on the ST-segment response in the right precordial leads in patients with normal left ventricular function.

BACKGROUND: The response of the ST-segment in the right precordial leads to Na+ channel blockers in patients without structural heart disease and a typical Brugada-type ECG has not been fully elucidated. METHODS AND RESULTS: A pilsicainide challenge test was performed in 161 patients and according to recently established ECG criteria and an organized computer algorithm, the ST morphology was classified and the maximum increase in the J wave amplitude (maxDeltaJ) from the standard and high right precordial leads V1-3 was examined. Before the test, subjects exhibiting type 1 ECG in the standard leads were excluded. After administering pilsicainide, type 1 ECGs in the standard leads were observed in 31 cases and a maxDeltaJ of >or=200 microV was observed in 29 cases (23 type 1, 2 type 2/3 and 4 normal ECGs). In the additional higher right precordial leads, type 1 ECGs were observed in 55 cases and a maxDeltaJ of >or=200 microV was observed in 45 cases (42 type 1 and 3 type 2/3 ECGs). CONCLUSIONS: A maxDeltaJ>or=200 microV induced by pilsicainide, including that measured in the high right precordial leads, was associated with a change mainly to a type 1 ECG.

Adult↗

PubMed2006

A case of a concealed type of Brugada syndrome with a J wave and mild ST-segment elevation in the inferolateral leads.

We report a patient with a concealed type of Brugada syndrome. The electrocardiogram in the emergency department revealed atrial fibrillation with an almost normal ST segment. Slight electrocardiogram abnormalities of the J wave and mild ST-segment elevation appeared in the inferolateral leads a few days later. Although the ST segment in the right precordial leads, including that recorded from the high intercostal space recording sites, was completely normal, a drug challenge test using pilsicainide revealed a coved-type ST-segment elevation only in a modified V2 lead placed 1 or 2 intercostal spaces higher.

Adult↗

PubMed2006

Accumulation of risk factors increases risk of thromboembolic events in patients with nonvalvular atrial fibrillation.

BACKGROUND: Accumulation of risk factors could increase thromboembolic event rates in patients with nonvalvular atrial fibrillation (NVAF). To validate this hypothesis, a post hoc analysis was performed to determine the relationship of risk levels and thromboembolic events in patients with NVAF from our previous prospective study. METHODS AND RESULTS: Risk levels were quantified using the CHADS2 index in 509 patients with NVAF (66.3+/-10.3 years old). One point each was given for patients with advanced age (>or=75 years), hypertension, congestive heart failure, and diabetes mellitus, and 2 points, to those with prior ischemic stroke or transient ischemic attack. Patients with a CHADS2 score of 0 were classified as low risk, 1 to 2 a moderate risk and 3 or more were high risk. Because hypertrophic cardiomyopathy had emerged as an independent risk factor for thromboembolism, the original CHADS2 score was modified by adding 1 point to patients with hypertrophic cardiomyopathy. Warfarin was given to 263 patients (mean international normalized ratio (INR) at enrollment, 1.86), antiplatelets (aspirin or ticlopidine) to 163 patients and no antithrombotic therapy to 83. During a mean follow-up period of 2 years, 31 thromboembolic events occurred. As the risk level (modified CHADS2 score) increased, the event rate increased for both the patient groups receiving warfarin (p=0.035) and those not receiving warfarin (p=0.048). When a thromboembolic event occurred in patients who had been treated with warfarin, the mean INR level was 1.41. Twelve (75%) of 16 patients complicated with thromboembolism during warfarin treatment had INR levels below the optimal levels (1.6-2.6) for Japanese patients. CONCLUSION: Accumulation of risk factors could increase risk of thromboembolic events in patients with NVAF. Adherence to the guidelines for anticoagulation therapy is recommended.

Aged↗

PubMed2006

Novel mutation of plakophilin-2 associated with arrhythmogenic right ventricular cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disease characterized by dilatation and akinesis of the right ventricle, and causes life-threatening ventricular arrhythmia. Mutations of plakophilin-2 (PKP2) have recently been identified as one causative abnormality in ARVC. A case of ARVC with a mutation of PKP2 is reported here. Direct sequencing of the patient's DNA revealed an insertion mutation in exon 8 of PKP2 (1728_1729insGATG). The mutation caused the frameshift and the premature termination of translation (R577DfsX5). This is the first case report of PKP2 mutation found in Japanese ARVC patients.

Adult↗

PubMed2005

Influence of advancing age on fractionated right atrial endocardial electrograms.

The influence of advancing age on atrial endocardial electrograms recorded during sinus rhythm in humans who do not have atrial fibrillation has not been assessed thus far. The prevalence of atrial arrhythmias has been reported to increase with advancing age. Right atrial endocardial catheter mapping during sinus rhythm was performed in 106 patients who had normal sinus node function and no paroxysmal atrial fibrillation to evaluate the influence of advancing age on atrial endocardial electrograms. The bipolar electrograms were recorded at 12 sites in the right atrium, and an abnormal atrial electrographic result was defined as lasting > or =100 ms and/or showing > or =8 fragmented deflections. A total of 1,272 right atrial endocardial electrograms was assessed and quantitatively measured. The mean number of abnormal atrial electrograms per patient (0.61 vs 0.14, p <0.02) and the incidence of abnormal atrial electrograms (11% vs 30%, p <0.02) were significantly greater in patients who were >60 years of age than in younger patients. The longest duration (r = 0.24, p <0.02) and the maximal number of fragmented deflections (r = 0.28, p <0.005) of atrial electrograms among the 12 right atrial sites showed a slight positive correlation with age. The process of aging modifies the electrophysiologic properties of the atrial muscle. There is a progressive increment in the extension of altered atrial muscle with advancing age in humans who do not have atrial fibrillation. Patients who are >60 years of age have significantly greater abnormalities on atrial endocardial electrograms than do younger patients.

Adolescent↗

PubMed2005

D-dimer level influences thromboembolic events in patients with atrial fibrillation.

BACKGROUND: Elevated coagulative molecular markers could reflect the prothrombotic state in the cardiovascular system of patients with non-valvular atrial fibrillation (NVAF). A prospective, cooperative study was conducted to determine whether levels of coagulative markers alone or in combination with clinical risk factors could predict subsequent thromboembolic events in patients with NVAF. METHODS: Coagulative markers of prothrombin fragment 1+2, D-dimer, platelet factor 4, and beta-thromboglobulin were determined at the enrollment in the prospective study. RESULTS: Of 509 patients with NVAF (mean age, 66.6 +/- 10.3 years), 263 patients were treated with warfarin (mean international normalized ratio, 1.86), and 163 patients, with antiplatelet drugs. During an average follow-up period of 2.0 years, 31 thromboembolic events occurred. Event-free survival was significantly better in patients with D-dimer level < 150 ng/ml than in those with D-dimer level>or==150 ng/ml. Other coagulative markers, however, did not predict thromboembolic events. Age (>or==75 years), cardiomyopathies, and prior stroke or transient ischemic attack were independent, clinical risk factors for thromboembolism. Thromboembolic risk in patients without the clinical risk factors was quite low (0.7%/year) when D-dimer was < 150 ng/ml, but not low (3.8%/year) when D-dimer was >or==150 ng/ml. It was >5%/year in patients with the risk factors regardless of D-dimer levels. This was also true when analyses were confined to patients treated with warfarin. CONCLUSIONS: D-dimer level in combination with clinical risk factors could effectively predict subsequent thromboembolic events in patients with NVAF even when treated with warfarin.

Aged↗

PubMed2005

[Aortitis syndrome].

Explore the source record for details and available documents.

Diagnosis, Differential↗

PubMed2004

Differentiation of the electrophysiological effects on the atrial myocardium between the pure Na channel blocker, pilsicainide, and flecainide.

UNLABELLED: The purpose of this study was to identify the difference between the pure Na channel blocker, pilsicainide and Ic-antiarrhythmic drug, flecainide, on the atrial electrophysiological characteristics. METHODS: The subjects consisted of 24 patients (48 +/- 12 years-old: P-group) in whom pilsicainide was administrated intravenously (1 mg/kg/10 min) and 31 patients (47 +/- 15 years-old: F-group) in whom flecainide was administrated intravenously (2 mg/kg/10 min). The atrial effective refractory period (ERP-A), intra-atrial conduction time (CT), max intra-atrial conduction delay (Max CD), repetitive atrial firing zone (RAFZ), fragmented atrial activity zone (FAZ) and intra-atrial conduction delay zone (CDZ) were measured before and after the drugs. RESULTS: Pilsicainide and flecainide significantly prolonged the ERP-A (211 +/- 27 msec to 246 +/- 39 msec; p < 0.001, 217 +/- 25 msec to 244 +/- 33 msec; p < 0.001, respectively) and CT (121 +/- 33 msec to 149 +/- 43 msec; p < 0.001, 122 +/- 22 msec to 153 +/- 27 msec; p < 0.001, respectively) to the same degree. However, the Max CD was shortened by pilsicainide, but not by flecainide. The RAFZ, FAZ and CDZ decreased in the P-group (21 +/- 25 msec to 4 +/- 10 msec; p < 0.01, 24 +/- 24 msec to 14 +/- 18 msec; p < 0.05, 56 +/- 29 msec to 43 +/- 32 msec, p < 0.05, respectively), but not in the F-group. CONCLUSIONS: The effects of atrial conduction delays may differ between pilsicainide and flecainide. Further examination will be needed to explain this mechanism.

Adult↗

PubMed2004

Effects of anticoagulation intensity on hemostatic markers in patients with non-valvular atrial fibrillation.

BACKGROUND: Elevation of hemostatic markers may account for the increased risk of ischemic stroke in patients with non-valvular atrial fibrillation (NVAF). The aim of this study was to determine the effects of anticoagulation intensity on hemostatic markers in patients with NVAF. METHODS AND RESULTS: In 509 patients with NVAF, comprising 263 patients treated with warfarin and 246 patients without warfarin, the hemostatic markers of prothrombin fragment F1.2 (F1.2), fibrin D-dimer, platelet factor 4 (PF4), and beta-thromboglobulin were determined and compared with those in 111 patients with sinus rhythm. F1.2 was inversely related with anticoagulation intensity and D-dimer increased with age. All hemostatic markers, except F1.2, were greater in patients with NVAF than in patients with sinus rhythm. F1.2 and D-dimer were significantly lower in patients with international normalized ratio (INR) > or =1.5 than in NVAF patients without warfarin and were not different between NVAF patients with INR of 1.5-1.9 and with INR > or =2.0. CONCLUSIONS: Low intensity of anticoagulation (INR 1.5-1.9) suppresses the elevated concentration of F1.2 and D-dimer in patients with NVAF, and might be favorable in Japanese patients with NVAF in view of the balance between prevention of thromboembolism and the adverse effect by warfarin (ie, bleeding).

Adult↗

PubMed2004

Attitudes of Japanese cardiologists toward anticoagulation for nonvalvular atrial fibrillation and reasons for its underuse.

BACKGROUND: Although warfarin reduces embolic events in patients with nonvalvular atrial fibrillation (NVAF), it is used less frequently in Japan and so the aim of the present study was to determine the attitudes of Japanese cardiologists toward antithrombotic therapy for NVAF patients. METHODS AND RESULTS: Subjects were NVAF patients enrolled in a prospective study in 1999. Clinical characteristics, type of NVAF and antithrombotic therapy, risk factors for embolism, and contraindications to warfarin were analyzed. Risk factors included advanced age (>75 years), hypertension, diabetes mellitus, congestive heart failure, and prior embolic events. Contraindications to warfarin included bleeding tendency, malignant tumors and others. Among 509 patients (66.6+/-10.3 years old), 359 had at least one risk factor for embolism and of these 359 patients, 200 (55.7%) received warfarin (ie, modest adherence to the guideline for antithrombotic therapy). There were 159 patients who had at least one risk factor but did not receive warfarin; 70.4% of these received antiplatelet drugs. Contraindications were found in only 22.6% and paroxysmal nature of NVAF seemed a possible reason for non-use of warfarin in 47.2% of 159 patients. CONCLUSIONS: In Japan warfarin is not used extensively for treatment of NVAF patients having risk factors and the reasons for not using antithrombotic therapy seemed inappropriate in most of patients.

Anticoagulants↗

PubMed2004

Prothrombotic activity is increased in patients with nonvalvular atrial fibrillation and risk factors for embolism.

STUDY OBJECTIVES: The aim of this study was to investigate whether risk factors for embolism would promote thrombus formation in patients with nonvalvular atrial fibrillation (NVAF). METHODS: Hemostatic markers for platelet activity (ie, platelet factor-4 and beta-thromboglobulin [TG]), thrombotic status (ie, prothombin fragments 1 and 2), and fibrinolytic status (ie, d-dimer) were determined in 246 patients with NVAF (mean age, 66.1 years) and 111 control subjects without NVAF (68.3 years). RESULTS: The beta-TG level was higher in NVAF patients than in control subjects. D-dimer levels were higher in NVAF patients having risk factors (mean [+/- SE] d-dimer level, 158.6 +/- 9.2 ng/mL) than in those without risk factors (mean d-dimer level, 92.1 +/- 6.7 ng/mL; p < 0.01) and in control subjects (mean d-dimer level: control subjects with risk factors, 79.1 +/- 10.3 ng/mL; control subjects without risk factors, 31.0 +/- 7.4 ng/mL; p < 0.01). NVAF (odds ratio [OR], 3.94; 95% confidence interval [CI], 1.87 to 8.30; p = 0.0003) and age of >/= 75 years (OR, 5.68; 95% CI, 2.87 to 11.23; p < 0.0001) emerged as predictors of elevated levels of d-dimer, and only NVAF (OR, 10.30; 95% CI, 5.67 to 18.72; p < 0.0001) emerged as a predictor of elevated levels of beta-TG. CONCLUSIONS: NVAF patients whose conditions were complicated with risk factors for embolism could be in the prothrombotic state. Advanced age is a strong predictor of the prothrombotic state in NVAF patients.

Aged↗

PubMed2003

Relation between microvolt-level T-wave alternans and cardiac sympathetic nervous system abnormality using iodine-123 metaiodobenzylguanidine imaging in patients with idiopathic dilated cardiomyopathy.

We examined the relation between microvolt-level T-wave alternans and cardiac sympathetic nervous system abnormality using iodine-123 metaiodobenzylguanidine imaging in patients with idiopathic dilated cardiomyopathy. Our results strongly indicate that cardiac sympathetic denervation and accelerated sympathetic nervous activity play important roles in the presence of microvolt-level T-wave alternans in patients with idiopathic-dilated cardiomyopathy.

3-Iodobenzylguanidine↗

PubMed2003

Comparison of expression of connexin in right atrial myocardium in patients with chronic atrial fibrillation versus those in sinus rhythm.

An abnormal distribution of the gap junction occurs in chronic atrial fibrillation (AF). There are conflicting data regarding changes in connexins (Cxs) in experimental models of AF. We examined whether patients with chronic AF have alterations in atrial Cxs. We analyzed the expression of Cx40 and Cx43 in the right atrial myocardium from 10 patients with mitral valvular disease (MVD) who had AF (MVD/AF), 10 patients with MVD who were in normal sinus rhythm (MVD/NSR), and 10 control patients in NSR (tissue obtained during coronary artery bypass surgery). Hemodynamic and echocardiographic data were obtained before surgery, and an electrophysiologic examination was performed during the operation. An immunohistochemical study was performed on atrial tissue. The relative expression level of Cx40 protein was significantly lower in MVD/AF patients (6.5 +/- 4.6) than in either MVD/NSR patients (17.7 +/- 8.9, p <0.05) or controls (24.7 +/- 11.1, p <0.01). The relative expression level of Cx40 messenger ribonucleic acid was also significantly lower in MVD/AF patients (0.23 +/- 0.13) than in MVD/NSR patients (0.47 +/- 0.26, p <0.01) or controls (0.47 +/- 0.17, p <0.01). For Cx43 protein and messenger ribonucleic acid, there was no significant difference in relative expression levels among the 3 groups. Interestingly, the level of serine-phosphorylated Cx40 was approximately 52% greater in MVD/AF patients than in controls. In MVD/AF patients, the immunoreactive signal of Cx40 was significantly lower than in controls. There was no significant difference in the connective tissue-volume fraction among the groups. Thus, downregulation of Cx40 and abnormal phosphorylation of Cx40 may result in abnormal cell-to-cell communication and alteration in the electrophysiologic properties of the atrium, leading to the initiation and/or perpetuation of AF.

Adult↗

PubMed2003

The effects of aging on atrial endocardial electrograms in patients with paroxysmal atrial fibrillation.

BACKGROUND: The prevalence of atrial fibrillation (AF) has been reported to increase with advancing age. Histologic studies in AF have demonstrated that the percentage of fibrosis and degenerative changes in the atrial muscle increase significantly with age. HYPOTHESIS: This study was undertaken to assess the influence of advancing age on atrial endocardial electrograms recorded during sinus rhythm in patients with paroxysmal atrial fibrillation (PAF), which had not been assessed previously. METHODS: Right atrial endocardial catheter mapping during sinus rhythm was performed in 111 patients with PAF to evaluate the influence of advancing age on atrial endocardial electrograms. The bipolar electrograms were recorded at 12 sites in the right atrium, and an abnormal atrial electrogram was defined as lasting > or = 100 ms, and/or showing eight or more fragmented deflections. RESULTS: In all, 1,332 right atrial endocardial electrograms were assessed and measured quantitatively. The number of abnormal atrial electrograms in patients with PAF showed a significantly positive correlation with age (r = 0.34; p < 0.0005). Patients aged > 60 years had a significantly greater mean number of abnormal electrograms (2.58 +/- 2.05) than those aged < 60 years (1.43 +/- 2.03; p < 0.004). The longest duration (r = 0.35; p < 0.0005) and the maximal number of fragmented deflections (r = 0.29; p < 0.005) of atrial electrograms among the 12 right atrial sites also showed a significantly positive correlation with age. CONCLUSIONS: Aging alters the electrophysiologic properties of the atrial muscle in patients with PAF. Elderly patients have a significantly greater abnormality of atrial endocardial electrograms than do younger ones. There is a progressive increment in the extension of altered atrial muscle with advancing age in patients with PAF.

Adult↗

PubMed2003

New method of determining the atrial fibrillation cycle length during human atrial fibrillation.

INTRODUCTION: The aim of this study was to investigate the usefulness of the autocorrelation function (reversed fast Fourier transform analysis) in determining the atrial fibrillation cycle length (AFCL) during human atrial fibrillation (AF). METHODS AND RESULTS: From 30 episodes of atrial electrograms recorded for 30 seconds from the high right atrium during type I AF in 16 patients, the mean, 5th percentile (p5), and 95th percentile (p95) of the AFCLs were measured by using a computer-picked activation time. The peak, minimum, and maximum AFCLs also were measured by using the autocorrelation function. The mean AFCL was retrieved at the point of the maximum peak of the coefficient of the first positive autocorrelogram. The minimum AFCL (min AFCL) was chosen as the point where the first positive autocorrelogram crossed the baseline from negative to positive, and the maximum AFCL (max AFCL) was chosen as the point where the first positive autocorrelogram crossed the baseline from positive to negative. There was a significantly strong correlation between the mean and peak AFCLs (r = 0.995, P < 0.0001), p5 and min AFCLs (r = 0.953, P < 0.0001), and p95 and max AFCLs (r = 0.98, P < 0.0001). CONCLUSION: The autocorrelation function was useful in determining the AFCLs, at least during type I AF. The min AFCL may be used as an index of the refractory period during AF when the p5 AFCL approximates the refractory period.

Aged↗

PubMed2003

Effects of flecainide on the electrophysiological properties of atrial vulnerability in humans.

The aims of this study were to evaluate the changes in the electrophysiological characteristics of the right atrium after the administration of flecainide and to clarify whether flecainide has a selective effect on human atrial tissue. Electrophysiological measurements were made in 38 patients, before and after intravenous administration of flecainide (2 mg/kg per 10 min). The effective refractory period of the right atrium (ERP-A), maximum conduction delay (Max.CD), repetitive atrial firing zone (RAFZ), fragmented atrial activity zone (FAAZ), and conduction delay zone (CDZ) were studied in the patients who were divided into 2 groups based on whether repetitive atrial firing (RAF) was induced in the baseline study. Flecainide significantly prolonged the ERP-A (202+/-22 to 238+/-33 ms, p<0.001) and shortened Max.CD (77+/-17 to 63+/-32 ms, p<0.05) in the patients with RAF, but not in those without RAF in the baseline study. After flecainide administration, there were significant reductions in the RAFZ (43+/-22 to 13+/-19 ms, p<0.0001), FAAZ (51+/-22 to 28+/-26 ms, p<0.001) and CDZ (70+/-21 to 48+/-30 ms, p<0.01) in the patients with RAF. However, atrial fibrillation (AF) was induced by stimulation after flecainide in 2 patients without RAF in the baseline study. There was a significant negative correlation between the ERP-A in the baseline study and the change in the ERP-A upon flecainide administration (r=0.45, p<0.01). Flecainide may preferentially activate the substrate for AF and RAF, but that action is mainly based on the electrophysiological characteristics found in the baseline study.

Anti-Arrhythmia Agents↗

PubMed2003

Decrease in the spatial dispersion at the termination of atrial fibrillation by intravenous cibenzoline.

Atrial electrograms were recorded from the high right atrium, coronary sinus, and right lateral wall in 15 patients with induced atrial fibrillation (AF). Intravenous cibenzoline terminated AF in 8 patients (T group), but not in 7 patients (non-T group). The cycle length of the AF (AFCL) obtained by the autocorrelation function was measured every 5 s during the 30 s prior to the cibenzoline administration, and just before the termination of AF or at the end of the cibenzoline infusion in the non-T group. The mean AFCL, and spatial and temporal dispersion of the AFCL were then compared between the 2 groups (dispersion = standard deviation x 100 /mean AFCL). Cibenzoline significantly increased the mean AFCL and decreased the spatial dispersion in both groups. No significant difference in either the mean AFCL or temporal dispersion before or after cibenzoline was observed between the 2 groups. In addition, no significant difference in the spatial dispersion before the cibenzoline was observed, but the spatial dispersion after the cibenzoline was significantly smaller in the T group than in the non-T group. The mean AFCL, and the spatial and temporal dispersion before the cibenzoline did not predict the termination of AF. The decrease in the spatial dispersion may be the most important mechanism by which intravenous cibenzoline terminates AF.

Aged↗

PubMed2003

Effect of long-term beta-blocker therapy on microvolt-level T-wave alternans in association with the improvement of the cardiac sympathetic nervous system and systolic function in patients with non-ischemic heart disease.

The purpose of this study was to test a hypothesis that T-wave alternans (TWA) is improved in association with an improvement in cardiac sympathetic nervous system and systolic function by oral beta-blocker therapy in patients with non-ischemic heart disease (NIHD). TWA testing, (123)I-metaiodobenzylguanidine (MIBG) imaging and echocardiography were performed at the baseline and 3 months after beta-blocker therapy in 26 patients with NIHD and positive TWA. The alternans voltage (V(alt)), the heart-to mediastinal-ratio on the early (e-H/M) and delayed (d-H/M) images, the washout rate (WR), the left ventricular ejection fraction (LVEF), and the calculated rate of change by beta-blocker therapy in each parameter (ie, deltaV(alt), deltae-H/M, deltad-H/M, deltaWR and deltaLVEF) were measured. After therapy, TWA turned negative in 8 patients (group A) and remained positive in 18 (group B); V(alt) was significantly decreased in group B (p<0.001). In group A, e-H/M, d-H/M and LVEF were significantly increased (e-H/M: p<0.05, d-H/M and LVEF: p<0.01), as were e-H/M and LVEF in group B (p<0.05). There were significant correlations between deltaV(alt) and deltae-H/M (r=-0.61, p<0.01), deltad-H/M (r=-0.82, p<0.0001), deltaWR (r=0.60, p<0.01) and deltaLVEF (r=-0.70, p<0.01). In patients with NIHD, the TWA is improved in association with the improvement in cardiac sympathetic nervous system abnormalities and left ventricular systolic dysfunction by beta-blocker therapy.

Action Potentials↗