Amplitude Of Cyclic Variation Research Articles

Constituent factors of heart rate variability ALLSTAR big data analysis

Various indices have been reported regarding heart rate variability (HRV), but many of them correlate to each other, suggesting the existence of the underlying common factors. We tried to extract factors underlying HRV indices and investigated their features. Using big data of 24-h electrocardiogram (ECG) called Allostatic State Mapping by Ambulatory ECG Repository (ALLSTAR), we calculated 4 time-domain, 4 frequency-domain, and 2 nonlinear HRV indices and the amplitude of cyclic variation of heart rate (Acv) in 113,793 men and 140,601 women with sinus rhythm ECG. Factor analysis revealed that there were two factors with eigenvalue ≥ 1 by which 91% of variance among the HRV indices was explained. Factor 1 that was strongly contributed by very-low frequency, low frequency (LF), and high frequency (HF) components and Acv and it increased with age from 0 to 20 year, then decreased until 65 year, and increased slightly after 80 year. It also increased with daily physical activity at the mild level of activity. Factor 2 that was contributed strongly by scaling exponent α1 and LF-to-HF ratio increased with age until 35 year, plateaued between 35 and 55 year, and decreased thereafter. It also increased with mild to moderate physical activity. HRV indices are constituted by two common factors relating to cardiac vagal function and complexity of heart rate dynamics, respectively, which differ in the relationships with age and physical activity from each other. Although many indices have been proposed for HRV, their constituent factors may be a few.

The influence of the permanent pacemaker on myocardial tissue characterization

This study was designed to investigate how pacemaeker would influence the myocardial tissue, accessing tissue characterization by ultrasonic integrated backsatter (IBS). Study Group included 30 cases underwent pacemaker implantation from Jan. 1 1988 to Apr. 30 2002. The group was divided into two subgroups; one group included patients implanted DDD mode pacemaker (DDD:16cases) and the other included patients implanted VVI mode pacemaker (VVI:14cases). Parasternal short axis view was shown using SONOS 5500 and recorded with IBS mode. The ROI was set in the interventricular anteroseptum (AS) and the posterior wall (PW) and measured the value of IBS (IB), then was corrected to reduce the IB of left ventricular cavity as standard value from IB (CIB). The amplitude of cyclic variation (CVIB) was defined the difference between enddiastolic IB and endsystolic IB. There was no correlation between CIB and CVIB in AS or PW and the term during pacing but CIB in both AS and PW in VVI was greater than that in DDD (15.3 ± 2.1:12.5 ± 3.4 p < 0.05). CVIB in AS and PW in VVI was not different from that in DDD (7.1 ± 0.6:7.8 ± 2.7).The increase of CIB signifies the fibrous change. So this result suggested unphysiological hemodynamics induced by pacing with VVI mode pacemaker, might cause the myocardial fibrosis.

674 Assessment of myocardial viability by acoustic densitometry in patients with left ventricle dysfunction due to coronary artery disease

Aim: The purpose of our study was to assess whether acoustic densitometry could distinguish between viable and irreversible dysfunctional myocardium in patients with coronary artery disease before myocardial revascularization. Methods: Seventy patients with chronic coronary artery disease and dysfunctional myocardial segments before planned myocardial revascularization were examined by acoustic densitometry. Fifty four patients had revascularization of at least one coronary artery supplying dysfunctional segments. Control echocardiography of these patients was performed after 3 months after bypass surgery or percutaneous coronary intervention for assessing contractility of revascularized, initially dysfunctional myocardial segments. The dysfunctional segments were defined as viable if they exhibited improvement in their thickening after revascularization. Wall motion was scored using 16-segment model of left ventricle, acoustic densitometry was evaluated from parasternal long axis view, parasternal short axis view at the level of papilary muscles and apical four-chamber and two-chamber views. Amplitude of cyclic variation of integrated backscatter (CVIB) was evaluated from each dysfunctional segment. Optimal cut off value of CVIB for distinction between viable and irreversible dysfunctional myocardium was found using receiver operating characteristic curves. Results: Cut off values for anteroseptal, posterior, interventricular septal, lateral, inferior and anterior segments were 4,1; 4,3; 4,4; 4,2; 4,5; 4,0 and 4,2 decibels, respectively. Sensitivity, specificity, positive and negative predictive values for identification of myocardial viability by acoustic densitometry using this cut off values were 918%, 81%, 87%, and 86%, respectively. Conclusion: Acoustic densitometry can differentiate viable and irreversible dysfunctional myocardium in patients with coronary artery disease before myocardial revascularization.

Force-Time Behaviour of Flat Tines in Dry Sand

Studies conducted in a laboratory soil bin filled with dry sand indicated that the nature of soil reactions on tines of 90° rake angle were cyclic for tine aspect ratios (width/depth) of 0·6 and greater. For tine aspect ratio of four, soil reactions were observed to be cyclic for all the tine rake angles studied (15-140°), These variations were found to be closely related to the observed soil failure patterns. Wave ratio (wave length/tine depth) for tines with a rake angle of 90° increased with increase in tine aspect ratio up to four. The amplitude of cyclic variations in draught increased with tine width for a rake angle of 90°.