Vascular Dysfunction in Hypertension Revealed by Fourier Analysis of Aortic Blood Flow

Impedance measurements have been used to quantify changes in vascular function associated with hypertension. Fourier analysis based solely on the arterial flow wave may provide a useful alternative to traditional techniques. Therefore the utility of blood flow frequency analysis in differentiating vascular changes in hypertension is tested. A frequency-based method was developed to evaluate the aortic pulse wave under conditions of spontaneous hypertension, sodium nitroprusside (SNP) induced normotension in spontaneously hypertensive rats (SHR), and phenylephrine (PE) induced hypertension in Wistar-Kyoto rats (WKY). Under anesthesia, animals were instrumented and signals were digitized for measurement of arterial blood pressure, aortic blood flow, and electrocardiogram. Hemodynamic parameters were extracted and the aortic flow signal was processed via Fourier analysis to produce a fingerprint of pulse transmission. Results demonstrated significant fingerprint differences between SHR and WKY at baseline pressures. Fingerprint differences are simulated by PE-induced hypertension, however, they did not match the SHR fingerprint despite similar flow-based biomarkers. Conversely, administration of SNP to the SHR creates differences in the fingerprint, however, SNP did not approximate the WKY fingerprint despite similar hemodynamics. Furthermore, characteristic fingerprint differences between SHR and WKY vasculature are maintained regardless of the intervention. In conclusion, results suggest Fourier analysis can be used to reveal functional vascular states regardless of pressure. Data presented demonstrates functional differences in the hypertensive vasculature that cannot be ameliorated with SNP, or reproduced with PE in normotensive vasculature. This may be useful clinically, to identify vascular dysfunction prior to overt hypertension.