Takefumi Oka

Greater than normal expression of the collagen-binding stress protein heat-shock protein-47 in the infarct zone in rats after experimentally-induced myocardial infarction.

BackgroundThe heat‐shock protein with relative molecular mass 47 000 (HSP47) can bind to procollagen molecules in the endoplasmic reticulum, and acts as a molecular chaperone during the processing and secretion of procollagen. ObjectiveTo test our hypothesis that HSP47 is expressed in the myocardial infarct zone. MethodsWe induced myocardial infarction in male Sprague–Dawley rats by ligation of left coronary artery. The expression of HSP47 was examined by Northern blotting, in‐situ hybridization, Western blotting and immunohistochemistry. The time‐dependent change in the distribution of HSP47 messenger RNA (mRNA) signal was compared with the changes in expression of α1(I) and α1(III) collagen mRNA by in‐situ hybridization. The hypoxic induction of HSP47 in cultured cardiac fibroblasts was examined by Northern‐blot analysis. ResultsNorthern blotting demonstrated that the expression of HSP47 mRNA had increased on day 2, reaching a maximum level around day 14 (induced 3.5‐fold compared with the preligation hearts) and was maintained at a high level up to day 28. In‐situ hybridization analysis revealed HSP47 mRNA signals in spindle‐shaped mesenchymal cells located between surviving myocytes in the infarcts peripheral zone 24 h after the ligation, and in the entire infarct zone on day 14. The sequential changes in distribution of HSP47 mRNA signal were identical to those of the α1(I) and α1(III) collagen mRNA. Western blotting demonstrated that expression of HSP47 protein in the infarct zone had increased. Immunofluorescent staining revealed positivity for HSP47 in the infarcts peripheral zone on day 2 and in the entire infarct zone on day 14. Northern blotting revealed that the expression of HSP47 mRNA in cultured cardiac fibroblasts in hypoxic cultures was greater than that in normoxic cultures. ConclusionThe present data demonstrated that an increase in expression of HSP47 is produced by spindle‐shaped mesenchymal cells in the infarct zone. Expression of HSP47 mRNA was concurrent with the expression of collagen mRNA of types I and III. Hypoxia is one of the factors which induces expression of HSP47.

Abnormal restitution property of action potential duration and conduction delay in Brugada syndrome: both repolarization and depolarization abnormalities

AIMS This study sought to examine the action potential duration restitution (APDR) property and conduction delay in Brugada syndrome (BrS) patients. A steeply sloped APDR curve and conduction delay are known to be important determinants for the occurrence of ventricular fibrillation (VF). METHODS AND RESULTS Endocardial monophasic action potential was obtained from 39 BrS patients and 9 control subjects using the contact electrode method. Maximum slopes of the APDR curve were obtained at both the right ventricular outflow tract (RVOT) and the right ventricular apex (RVA). The onset of activation delay (OAD) after premature stimulation was examined as a marker of conduction delay. Maximum slope of the APDR curve in BrS patients was significantly steeper than that in control subjects at both the RVOT and the RVA (0.77 +/- 0.21 vs. 058 +/- 0.14 at RVOT, P = 0.009; 0.98 +/- 0.23 vs. 0.62 +/- 0.16 at RVA, P = 0.001). The dispersion of maximum slope of the APDR curve between the RVOT and the RVA was also larger in BrS patients than in control subjects. The OAD was significantly longer in BrS patients than in control subjects from the RVOT to RVA and from the RVA to RVOT (from RVOT to RVA: 256 +/- 12 vs. 243 +/- 7 ms, P = 0.003; from RVA to RVOT: 252 +/- 11 vs. 241 +/- 9 ms, P = 0.01). CONCLUSIONS Abnormal APDR properties and conduction delay were observed in BrS patients. Both repolarization and depolarization abnormalities are thought to be related to the development of VF in BrS patients.

Differential effects of cardiac sodium channel mutations on initiation of ventricular arrhythmias in patients with Brugada syndrome

BACKGROUND Premature ventricular contractions (PVCs) do not occur frequently but can induce ventricular fibrillation (VF) in patients with Brugada syndrome. The effect of SCN5A mutation on the onset of ventricular arrhythmias is unknown. OBJECTIVE The purpose of this study was to evaluate PVC morphology and onset of VF in patients with Brugada syndrome. METHODS Morphology of PVCs was evaluated by 12-lead ECG in 32 patients with Brugada syndrome. Patients had spontaneous ventricular arrhythmia (n = 17) or sodium channel blocker-induced ventricular arrhythmia (n = 19). Patients were classified into two groups according to the existence of SCN5A mutation (22 mutation negative, 10 mutation positive). RESULTS Patients without mutation often had PVCs of left bundle branch block (LBBB) morphology (82%), especially with inferior axis (77%). Patients with mutation had PVCs of both right bundle branch block (36%) and LBBB (64%) morphologies. Only two patients with mutation had PVCs of LBBB, inferior-axis morphology. CONCLUSION Patients without SCN5A mutation often had PVCs of LBBB, inferior-axis morphology, suggesting a right ventricular outflow tract origin. Patients with SCN5A mutations had PVCs that originated from both the right and left ventricles.

Abnormal transmural repolarization process in patients with Brugada syndrome

BACKGROUND Repolarization abnormality, especially during bradycardia, might be critical for initiation of ventricular fibrillation (VF) in patients with Brugada syndrome (BrS), but the contribution of the rate-dependent repolarization dynamics to the occurrence of VF is still unknown. OBJECTIVE The aim of our study was to determine the differences in rate-dependent repolarization dynamics between BrS with and without spontaneous VF and between BrS with and without SCN5A mutation. METHODS The subjects were 37 BrS patients with VF (VF(+) group: 10 male subjects) and without VF (VF(-) group: 27 male subjects) and 20 control subjects. Genetic analysis of SCN5A was performed in all 37 BrS patients. The relationships between QT, QTp, Tp-e, and RR intervals were obtained from Holter recordings as first linear regression lines, and the slopes of QT/RR, QTp/RR, and Tp-e/RR linear regression lines as the sensitivity of rate-dependent repolarization dynamics were compared. RESULTS QT/RR and Tp-e/RR slopes showed loss of a rate-dependent property in the VF(+) group compared with those in the VF(-) and control groups. There was no significant difference in QTp/RR slope among the VF(+), VF(-) and control groups. The Tp-e interval had a negative correlation with the RR interval in the VF(+) group and a positive correlation with the RR interval in the VF(-) and control groups. There was no significant difference in QT/RR, QTp/RR, and Tp-e/RR slopes between BrS patients with SCN5A mutation and those without SCN5A mutation. CONCLUSIONS Loss of rate-dependent QT dynamics may be associated with occurrence of VF in BrS.

Double-Sector Lorenz Plot Scattering in an R-R Interval Analysis of Patients With Chronic Atrial Fibrillation Incidence and Characteristics of Vertices of the Double- Sector Scattering

Abstract Animal experiments have demonstrated that the minimum R-R interval during atrial fibrillation is proportional to the functional refractory period of the atrioventricular node. On Lorenz plots, atrial fibrillation is characterized by sector-shaped scattering; the vertex of the sector (ie, the minimum R-R interval) represents the functional refractory period. According to the atrioventricular nodal dual-pathway theory, it was hypothesized that the dual atrioventricular nodal pathways associated with chronic atrial fibrillation represent two vertices with two sectors. Detection of two-sector Lorenz plot scattering was attempted in 48 patients with chronic atrial fibrillation who underwent 24-hour ambulatory electrocardiography. Lorenz plot scattering was constructed by means of a computer. Two sectors, suggesting dual pathways, were detected in 19 (40%) of the 48 patients. The two vertices, located at 388 ± 61 ms (mean ± SD) and 580 ± 60 ms were considered to represent the functional refractory periods of the fast and slow pathways, respectively. The vertex indicating the fast pathway showed greater circadian variation than that indicating the slow pathway. In one patient with dual-sector Lorenz plot scattering, whose atrial fibrillation spontaneously converted to sinus rhythm, an electrophysiologic study demonstrated dual atrioventricular nodal pathways. Thus, the Lorenz plot analysis identified two sectors, indicating the dual pathways, in approximately 40% of the patients with chronic atrial fibrillation, and the characteristics of the functional refractory periods of both pathways were estimated from the characteristics of the vertices. Although this study did not provide direct evidence of the dual atrioventricular nodal pathways, the analysis of Lorenz plot scattering may be clinically useful for studying the effects of drugs and/or ablation on the ventricular response in patients with atrial fibrillation based on the dual atrioventricular nodal pathway theory.

Effect of remote ischemia or nicorandil on myocardial injury following percutaneous coronary intervention in patients with stable coronary artery disease: A randomized controlled trial

BACKGROUND The effect of remote ischemic preconditioning (RIPC) and nicorandil on periprocedural myocardial injury (pMI) in patients with planned percutaneous coronary intervention (PCI) remains controversial. The aim of this randomized trial was to evaluate the effect of RIPC or nicorandil on pMI following PCI in patients with stable coronary artery disease (CAD) compared with a control group. METHODS Patients with stable CAD who planned to undergo PCI were assigned to a 1:1:1 ratio to control, RIPC, or intravenous nicorandil (6mg/h). Automated RIPC was performed by a device, which performs intermittent arm ischemia through three cycles of 5min of inflation and 5min of deflation of a pressure cuff. The primary outcome was the incidence of pMI, determined by an elevation in high-sensitive troponin T or creatine kinase myocardial band at 12 or 24h after PCI. The secondary outcomes were ischemic events during PCI and adverse clinical events at 8months after PCI. RESULTS A total of 391 patients were enrolled. The incidence of pMI following PCI was not significantly different between the control group (48.9%) and RIPC group (39.5%; p=0.14), or between the control group and nicorandil group (40.3%; p=0.17). There were no significant differences in ischemic events during PCI or adverse clinical events within 8months after PCI among the three groups. CONCLUSIONS This study demonstrated moderate reductions in biomarker release and pMI by RIPC or intravenous nicorandil prior to the PCI consistently, but may have failed to achieve statistical significance because the study was underpowered.

Relationship between circulating levels of monocyte chemoattractant protein-1 and systolic dysfunction in patients with hypertrophic cardiomyopathy

BACKGROUND Progression of hypertrophic cardiomyopathy (HCM) to left ventricular dilatation and systolic dysfunction sometimes occurs. However, the mechanism of the transition from hypertrophy to dysfunction has not been elucidated. It has been reported that circulating levels of monocyte chemoattractant protein-1 (MCP-1), which is a major factor promoting the accumulation of macrophages, are increased in patients with congestive heart failure. We measured circulating levels of MCP-1 in patients with HCM and examined whether MCP-1 was expressed in the myocardium of HCM patients. We also examined whether circulating levels of MCP-1 were correlated with left ventricular dysfunction. METHODS Circulating levels of MCP-1 were measured by an enzyme immunoassay in 26 patients with HCM (60+/-2 years old) and 20 control subjects (57+/-2 years old). Cardiac function was evaluated by two-dimensional echocardiography and cardiac catheterization. RESULTS HCM patients had significantly elevated levels of MCP-1 (HCM: 309+/-30 vs. control: 178+/-8 pg/ml, P<.001). MCP-1 levels in patients with systolic dysfunction were significantly higher than those in patients without systolic dysfunction (P<.05) and were also significantly higher than those in patients with outflow obstruction (P<.05). Immunohistochemical analysis revealed that MCP-1 was expressed in endomyocardial biopsy samples obtained from HCM patients with systolic dysfunction. Furthermore, MCP-1 levels were inversely correlated with fractional shortening (r=-.401, P<.05) and correlated with left ventricular end-diastolic pressure (r=-.579, P<.01). CONCLUSION These results show that MCP-1 is associated with, and might be involved in the pathogenesis of, left ventricular systolic dysfunction in patients with HCM.

Effect of Intensive and Standard Pitavastatin Treatment With or Without Eicosapentaenoic Acid on Progression of Coronary Artery Calcification Over 12 Months ― Prospective Multicenter Study ―

BACKGROUND The effect of lipid-lowering agents on progression of coronary artery calcification (CAC) remains unclear. We evaluated the effects of pitavastatin 2 mg/day (PIT2), pitavastatin 4 mg/day (PIT4), and PIT2 combined with eicosapentaenoic acid (PIT2+EPA) on CAC progression.Methods and Results:This prospective multicenter study in Japan included patients with an Agatston score of 1-999, hypercholesterolemia, and no evidence of cardiovascular disease. Patients were allocated into PIT2, PIT4, or PIT2+EPA groups. The primary outcome was the annual percent change in Agatston score in all patients. In total, 156 patients who had multi-detector row computed tomography without any artifacts were included in the primary analysis. Pitavastatin did not significantly reduce the annual progression rate of the Agatston score (40%; 95% CI: 19-61%). The annual progression rate of Agatston score in the PIT2 group was not significantly different from that in the PIT4 group (34% vs. 42%, respectively; P=0.88) or the PIT2+EPA group (34% vs. 44%, respectively; P=0.80). On post-hoc analysis the baseline ratio of low- to high-density lipoprotein cholesterol was a significant predictor of non-progression of Agatston score by pitavastatin (OR, 2.17; 95% CI: 1.10-44.12; P=0.02). CONCLUSIONS Pitavastatin does not attenuate progression of CAC. Intensive pitavastatin treatment and standard treatment with EPA does not reduce progression of CAC compared with standard treatment.

EFFECTS OF A DIRECT RENNIN INHIBITOR OR A DIURETIC ADDED ON AN ANGIOTENSIN II RECEPTOR BLOCKER ON CENTRAL AORTIC PRESSURE IN HYPERTENSIVE PATIENTS (ALEA STUDY)

To achieve the target blood pressure recommended by the latest guidelines, multiple antihypertensive drugs are needed in most patients. Furthermore, recent studies showed that central aortic pressure is closely associated with target organ damages. We compared the effects of a direct rennin