Michiro Maruyama

Spectral analysis of heart rate, arterial pressure, and muscle sympathetic nerve activity in normal humans

We investigated the frequency components of fluctuations in heart rate, arterial pressure, respiration, and muscle sympathetic nerve activity (MSNA) in 11 healthy women using an autoregressive model and examined the relation among variables using Akaikes relative power contribution analysis with multivariate autoregressive model fitting. Power spectral analysis of MSNA revealed two peaks, with low-frequency (LF) and high-frequency (HF) components. The LF component of MSNA was a major determinant of the LF component of arterial pressure and R-R interval variability (0.70 +/- 0.07 and 0.18 +/- 0.05, respectively). The effect of the LF component of MSNA on arterial pressure showed no change in response to propranolol but was diminished (0.35 +/- 0.08) by phentolamine (P < 0.02). The effect of the LF component of MSNA on R-R interval was not altered by pharmacological sympathetic nerve blockade. The HF component of MSNA did not influence other variables but was influenced by R-R interval, arterial pressure, and respiration. These findings indicate that the LF component of MSNA reflects autonomic oscillations, whereas the HF component is passive and influenced by other cardiovascular variables.

A case of delayed occlusive dissection of the right coronary artery during coronary intervention of the left anterior descending artery.

Abstract Catheter-induced coronary artery dissection occurs rarely during selective coronary angiography but generally progresses to complete coronary occlusion. We present a case of delayed occlusive dissection of the right coronary artery during coronary intervention of the left anterior descending artery. Bailout stenting was employed to treat the giant hematoma quickly using a unique technique. The use of two guidewires created a high probability that the true lumen was selected, and aspiration of the hematoma with the microcatheter and indeflator effectively repaired a catheter-induced coronary artery dissection.

Impact of left atrial size on isolation area in the acute phase of pulmonary vein isolation using 28 mm cryoballoon

The impact of left atrial (LA) size on isolation area (ISA) using a 28‐mm second‐generation cryoballoon (CB) in the acute phase after pulmonary vein isolation (PVI) and the differences of CB from contact force‐guided radiofrequency (RF) ablation have not been fully investigated.

Adaptive cardiac resynchronization therapy for dilated cardiomyopathy with functional mitral regurgitation

We report the case of a man in his 60s who had dilated cardiomyopathy with severe functional mitral regurgitation. Four years after a cardiac resynchronization therapy (CRT) device with an implantable cardioverter defibrillator was implanted, this device was replaced with an adaptive CRT device because of battery consumption. Seven months after replacement of this device, the left ventricular pacing to right ventricular activation and the atrioventricular delay from automatic adjustments contributed to less functional mitral regurgitation. The findings from our case suggest that optimal CRT, by measuring intracardiac conduction parameters, is effective for functional mitral regurgitation.

Altered gene expression in T-cell receptor signalling in peripheral blood leucocytes in acute coronary syndrome predicts secondary coronary events

Objective Comprehensive profiling of gene expression in peripheral blood leucocytes (PBLs) in patients with acute coronary syndrome (ACS) as a prognosticator is needed. We explored the specific profile of gene expression in PBLs in ACS for long-term risk stratification. Methods 30 patients with ACS who underwent primary percutaneous coronary intervention (PCI) and 15 age-matched adults who participated in medical check-ups were enrolled from three centres. Peripheral blood samples were collected to extract RNA for microarray analyses. Results During the 5-year follow-up, 36% of this cohort developed the expected non-fatal coronary events (NFEs) of target lesion revascularisation (TLR) and PCI for a de novo lesion. Class comparison analysis (p<0.005) demonstrated that 83 genes among 7785 prefiltered genes (41 upregulated vs 42 downregulated genes) were extracted to classify the patients according to the occurrence of NFE. Pathway analysis based on gene ontology revealed that the NFEs were associated with altered gene expression regarding the T-cell receptor signalling pathway in ACS. Univariate t test showed that the expression level of death-associated protein kinase1 (DAPK1), known to regulate inflammation, was the most significantly negatively regulated gene in the event group (0.61-fold, p<0.0005). Kaplan-Meier curve analysis and multivariate analysis adjusted for baseline characteristics or clinical biomarkers demonstrated that lower DAPK1 expression in PBL emerged as an independent risk factor for the NFEs (HR: 8.73; CI 1.05 to 72.8, p=0.045). Conclusions Altered gene expression in T-cell receptor signalling in PBL in ACS could be a prognosticator for secondary coronary events. Trial registration number UMIN000001932; Results.

The Rho/Rho-kinase Systems Are Involved in Rapid Pacing-induced Changes of Atrial Refractory Period in a Canine Model

Introduction: The Rho/Rho‐kinase pathway has been related to various physiological responses of the cardiovascular system. Previous reports have suggested a significant effect of Rho signals on the electrophysiological characteristics of the heart. We hypothesized that the Rho/Rho‐kinase system would contribute to the rapid pacing‐related change of atrial effective refractory period (AERP).

Effect of pimobendan on cardiopulmonary baroreflex control of sympathetic nerve activity in healthy young men.

In order to determine the effect of pimobendan on sympathetic nerve activity and cardiopulmonary baroreflex (CPB), electrocardiogram, direct arterial pressure, central venous pressure (CVP) and cardiac output were recorded along with muscle sympathetic nerve activity (MSNA) in 8 healthy young men. CPB function was evaluated before and 60 min after oral administration of 5 mg pimobendan using the response of MSNA to lower body negative pressure (LBNP) of -5 and -10 mm Hg. The same protocol also was performed during handgrip exercise. Cardiac index, MSNA increased and CVP decreased significantly (p<0.01, respectively), but arterial pressure and heart rate unchanged after pimobendan administration. During LBNP, CVP decreased and MSNA increased significantly. CPB sensitivity was augmented from 5.53+/-0.75 to 8.59+/-0.78 burst incidence/mm Hg after pimobendan administration (p<0.01). Pimobendan did not alter the percentage increase of MSNA during handgrip exercise. In conclusion, pimobendan induces an increase in basal sympathetic nerve activity by decreasing CVP and augmenting CPB sensitivity without changing arterial pressure in healthy young men.