Browsing by Author "Grant, Andrew"

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    P1.4 Hemodynamics of Pulmonary Hypertension: Application of the Reservoir-Wave Approach
    (2015-11-23) Ghimire, Anukul; Andersen, Mads; Burrowes, Lindsay; Bouwmeester, J. C.; Grant, Andrew; Belenkie, Israel; Fine, Nowell; Borlaug, Barry; Tyberg, John
    Abstract Using the reservoir-wave approach, previously we characterized pulmonary vasculature mechanics with multiple interventions in a canine model. In the present study, we measured high-fidelity pulmonary arterial (PA) pressure, Doppler flow velocity, and pulmonary capillary wedge pressure in 11 patients referred for evaluation of exertional dyspnea. The analysis was performed using the reservoir-wave approach; wave intensity analysis was subsequently utilized to characterize the PA wave pattern. Our objective was to identify specific abnormalities associated with pulmonary hypertension. Seven patients with varying PA pressures had reduced pulmonary vascular conductance (i.e., the amount of flow that the lungs can accept per pressure gradient), suggesting that these patients might benefit from pulmonary vasodilator therapy, some even in the absence of markedly elevated PA pressures. Right ventricular (RV) performance was assessed by examining the work done by the wave component of systolic PA pressure. Wave work, the non-recoverable energy expended by the RV to eject blood, varied directly with mean PA pressure. Wave pressure was partitioned into two components: forward-travelling and reflected backward-travelling waves. Among patients with lower PA pressures, we found pressure-decreasing backward waves that aided the RV during ejection, as previously reported in normal experimental animals. Among patients with higher PA pressures, we detected pressure-increasing backward waves that impede RV ejection. We conclude that it is important to measure pulmonary vascular conductance to properly assess the pulmonary vasculature. The reservoir-wave approach and wave intensity analysis may prove to be valuable tools to evaluate RV performance and may facilitate development of therapeutic strategies.
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    Pulmonary Hypertension: Insights From the Reservoir-Wave Approach
    (2016) Ghimire, Anukul; Tyberg, John; Fine, Nowell; Belenkie, Israel; Grant, Andrew
    We employed the reservoir-wave approach to analyze high-fidelity pulmonary arterial (PA) pressure and Doppler flow velocity in 11 patients with varying cardiac diseases. Our specific objectives were to (1) to characterize PA wave pattern and (2) evaluate right ventricular (RV) performance. Wave pressure was partitioned into its forward and backward components. Among patients with lower PA pressures, pressure-decreasing and flow-increasing reflected waves that assist RV ejection were detected. Among the more pulmonary hypertensive patients, pressure-increasing and flow-decreasing reflected waves that impede RV ejection were detected. The four patients with the highest PA pressures showed an early systolic deceleration in flow, which was found to coincide with reflected pressure-increasing, flow-decreasing waves. Wave work done by the RV increased with PA pressure, but expressed as a fraction of total RV work, did not change. The reservoir-wave approach may prove to be a valuable tool to characterize PA-RV interaction and evaluate RV performance.