All ETDs from UAB

Advisory Committee Chair

Himanshu Gupta

Advisory Committee Members

Inmaculada B Aban

Thomas S Denney

Roy P Koomullil

Bharat K Soni

Document Type

Dissertation

Date of Award

2015

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

Pulmonary arterial (PA) impedance takes in to account pulsatile blood flow through elastic pulmonary arteries as compared to static pulmonary vascular resistance. Increased PA impedance is an early physiological manifestation of PA remodeling. Currently PA impedance can only be detected invasively, is expensive and cumbersome to calculate and thus not done in routine clinical practice. The ability to assess PA impedance non-invasively can provide fundamental insights in evaluation of patients with normal PA pressures or mild pulmonary hypertension such as in patients with chronic obstructive lung disease. Non-invasive evaluation of right ventricular (RV)-PA axis to detect patients who could develop RV dysfunction will therefore provide a mechanistic rationale for therapeutic interventions that target early changes in cardiac structure and function in otherwise mild pulmonary hypertension. In this study, a novel non-invasive parameter, velocity transfer function (VTF), is described which is related to PA stiffness and impedance. In 20 patients undergoing clinically indicated right heart catheterization, comprehensive phase-contrast and cine-cardiac magnetic resonance imaging was obtained to calculate VTF and to accurately define RV afterload, mass, volumes and function. This novel non-invasive RV-PA axis coupling parameter, VTF, was validated against invasive reference standard (invasive impedance) measured using pressure data from right heart catheterization and velocity data from Doppler echocardiography. In this study, it was shown for the first time that PA impedance can be assessed completely non-invasively using VTF as its surrogate. It was demonstrated that VTF has the potential to differentiate between spectrums of impedances and detection of patients with early PA mechanical remodeling. The study showed the potential of VTF in detecting PA impedance independent of elevation in pulmonary capillary wedge pressure. It also showed significant association of VTF with RV ejection fraction and RV mass index. VTF was robust in its measurement with high intra- and inter- observer agreement on repeated independent measurements on blinded studies. In conclusion, VTF has the potential to assess PA impedance completely non-invasively and reliably using cardiac magnetic resonance imaging with potential to non-invasively detect early PA remodeling.

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