Elevated oxidative stress and endothelial dysfunction in right coronary artery of right ventricular hypertrophy.

Remodeling of right coronary artery (RCA) occurs during right ventricular hypertrophy (RVH) induced by banding of the pulmonary artery (PA). The effect of RVH on RCA endothelial function and reactive oxygen species (ROS) in vessel wall remains unclear. A swine RVH model (n = 12 pigs) induced by PA banding was used to study RCA endothelial function and ROS level. To obtain longitudinal coronary hemodynamic and geometric data, digital subtraction angiography was used during the progression of RVH. Blood flow in the RCA increased by 82% and lumen diameter of RCA increased by 22% over a 4-wk period of RVH. The increase in blood flow and the commensurate increase in diameter resulted in a constant wall shear stress in RCA throughout the RVH period. ROS was elevated by ∼100% in RCA after 4 wk of PA banding. The expressions of p47(phox), NADPH oxidase (NOX1, NOX2, and NOX4) were upregulated in the range of 20-300% in RCA of RVH. The endothelial function was compromised in RCA of RVH as attributed to insufficient endothelial nitric oxide synthase cofactor tetrahydrobiopterin. In vivo angiographic analysis suggests an increased basal tone in the RCA during RVH. In conclusion, stretch due to outward remodeling of RCA during RVH (at constant wall shear stress), similar to vessel stretch in hypertension, appears to induce ROS elevation, endothelial dysfunction, and an increase in basal tone.

A comparative analysis of coronary and aortic flow waveforms.

Empirical Mode decomposition (EMD) is a mathematical tool designed to analyze non-stationary, non-linear stochastic waves. EMD separates a waveform into its constituent modes of oscillations or intrinsic mode functions (IMFs) and provides meaningful definitions of instantaneous frequency, instantaneous energy, mean trends and oscillation about the mean trends. This study provides a detailed mathematical analysis of blood flow waveforms in the porcine left anterior descending artery and aorta using EMD. Flow data with non-stationary and non-linear characteristics were obtained for several hours using an implanted wireless biotelemetry device. EMD was validated against modern numerical techniques of principal component analysis (PCA) and wavelet analysis by comparing their predicted mean trends and energy distribution. EMD has an advantage over both techniques since it combines the strengths of both: it is adaptive (similar to PCA), and it can define instantaneous frequencies (similar to wavelet analysis). Because of the iterative nature, however, calculations using EMD can be computationally intensive. Sampling rate reduction was used to reduce computation time, without significantly effecting accuracy of IMF calculations. It was found that IMFs calculated at a sampling rate as low as 20 Hz were not significantly different (<6%) from those obtained at the original sampling rate (200 Hz). Our findings suggest that EMD may be a powerful mathematical tool to characterize flow waveforms.