Abstract 10116: Non-invasive Measurement of Ascending Aorta Impedance Using Cardiac Magnetic Resonance and Applanation Tonometry as the Optimal Guide to Assess the Severity of Aortic Valve Stenosis

IntroductionThe left ventricle (LV) faces a dual afterload in patients with aortic valve stenosis (AS) – valvular load due to the AS, and arterial load consequent on arterial age. Simultaneous high-fidelity radial artery tonometry (AT) and cardiac magnetic resonance (CMR) provides a more comprehensive assessment of aortic flow velocity, pressure and vascular impedance (Z) than transthoracic echocardiogram (TTE) and/or cardiac catheterisation.HypothesisTo measure non-invasively ascending aortic pressure, flow and impedance (Z) in patients with AS.MethodsPatients with AS were enrolled to undergo a simultaneous AT/CMR protocol, TTE and cardiac catheterisation. CMR provided LV volume and aortic flow simultaneously with radial AT pressure acquisition. Radial AT pressure was used to derive ascending aortic pressure using an FDA approved method. Z was determined as the relationship of derived aortic pressure to CMR aortic flow velocity.ResultsTwenty patients (age 80±9 years; 12 males; BP 140/75±20mmHg) with AS on TTE (15 severe; average mean 45±16mmHg; peak velocity 418±67cm/sec; AVA 0.8±0.2cm; EF 63±9%; LVEDV 125±44ml) were enrolled. CMR aortic flow velocity data was recorded in the ascending aorta (average maximum flow 278.8±50.3mL/s; mean gradient 37±13mmHg[n=9]; AVA 0.9±0.2cm; EF 65±14%; LVEDV 121±40ml). Average AT/CMR derived SVR was 2167±682dyne.s.cm-5. Invasive aortic pressures wereaverage peak-to-peak gradient 51±24mmHg; mean pullback 37±17mmHg; SVR 1652±841dyne.s.cm-5[n=8]). The AT/CMR derived values corresponded well with those obtained invasively for aortic pressure and SVR (Figure 1).ConclusionsVascular impedance is oft forgotten and difficult to measure invasively in AS. Simultaneous AT/CMR can be used to better characterise the dual afterload affecting the LV in the setting of aortic valve stenosis.