Normal and stenotic human aortic valve opening: in vitro assessment of orifice area changes with flow

Abstract

The ability to measure aortic valve area clinically has emphasized the need to understand the changes in aortic valve orifice area during flow. To compare the performance of normal and stenotic human aortic valves we used a pulsatile flow model that simulated in vivo flow conditions. Five normal autopsy specimens and 15 stenotic valves removed at operation were mounted into the model. Valve function was assessed by analysis of video recordings of valve leaflet motion during flow. Over the flow rates tested normal valves demonstrated a linear increase in orifice area. There was no resistance to leaflet opening and valve closure was rapid. The majority of stenotic valves demonstrated an increase in orifice area at low flow rates. No valve showed any increase in maximal area beyond flow rates of 3 l min-1. Increased leaflet resistance of these abnormal valves resulted in notably slower opening and closing rates. In patients with a high cardiac output and severe stenosis, overestimation of the anatomic orifice area derived by the Gorlin equation can result. This is not related to variability in maximal orifice area.

Dobutamine stress echocardiography for noninvasive assessment and risk stratification of patients with rheumatic mitral stenosis

“…Calculation of MVA by the continuity equation may represent an average of the instantaneous values throughout diastole and thus a better measurement at rest, but it was not used in the present study because of its limitations during tachycardia. In vitro models have suggested that peak MVA cannot be further increased, but the mean valve area can be enhanced simply by acceleration of the opening and closing phases (30). This may result in an increase of the calculated MVA due to an increase in the contraction coefficient, which is the ratio of effective to anatomic valve areas (31).…”

Simplified Pulse Reactor for Real-Time Long-Term In Vitro Testing of Biological Heart Valves

“…9) and showed similar characteristics like the EOA of human aortic valves. 14,22 The slightly asymmetric shape of the closing leaflets of the SJM Epic TM Supra Valve in Fig. 9 at t = 0.28 s might be caused by the sewing of the leaflets into the stent by the manufacturer.…”

Comparação dos valores de débito cardíaco obtidos por termodiluição e dopplerfluxometria transesofágica

“…O método de medida hemodinâmica mais utilizado é a TD, por apresentar maior precisão e estar incorporado na prática clínica por mais tempo 4,6,10 . Já o DTE, apresenta maior simplicidade, porém tem sido mais recentemente incorporado na prática clínica 5 .…”

“…

INTRODUÇÃOEntre os vários métodos disponíveis para a monitoração do débito cardíaco (DC) de pacientes submetidos a procedimentos cirúrgicos ou internados em unidades de terapia intensiva 1-2 , tem encontrado aceitação universal a termodiluição (TD), considerada gold standard na monitoração hemodinâmica [3][4] . Na última década, diversos estudos foram realizados com o objetivo de encontrar métodos simples e pouco invasivos, que permitam determinar com precisão o débito cardíaco 1,5-6 .

…”