Paul S Pagel1, Andrew R Schroeder2, Derek J De Vry2, Judith A Hudetz2. 1. Anesthesia Service, the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI. Electronic address: pspagel@mcw.edu. 2. Anesthesia Service, the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI.
Abstract
OBJECTIVE: Standard methods of quantifying aortic valve stenosis (AS), which focus entirely on the valve itself, do not adequately characterize the magnitude, predict the onset, progression, and severity of symptoms, or identify the incidence of subsequent adverse events. Valvuloarterial impedance (Z(va)) is an index of global left ventricular (LV) afterload that incorporates valvular and arterial loads. The authors tested the hypothesis that aortic valve replacement (AVR) reduces Z(va) but does not affect the arterial component of LV afterload in elderly patients with degenerative calcific trileaflet AS. DESIGN: Observational study. SETTING: Veterans affairs medical center. PARTICIPANTS: Eight elderly (age, 79 ± 4 years) men with moderate-to-severe AS and normal preoperative LV function (ejection fraction, 61% ± 9%) scheduled for AVR with or without coronary artery bypass graft surgery were studied after institutional review board approval. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A comprehensive TEE examination was performed during isoflurane-fentanyl-rocuronium anesthesia. Doppler echocardiography was used to measure pressure gradients across the aortic valve, stroke volume (continuity equation), and aortic valve area using standard techniques. Z(va) was determined as (systolic arterial pressure+mean gradient)/stroke volume index. Energy loss index was calculated as (aortic area × aortic valve area)/([aortic area--aortic valve area]× body surface area). The stroke work loss was obtained as (mean gradient × 100/[systolic arterial pressure+mean gradient]). The ratio of stroke volume index to pulse pressure was used to measure systemic arterial compliance. Z(va), energy loss index, stroke work loss, and systemic arterial compliance were assessed before and 15 minutes after cardiopulmonary bypass. Systemic and pulmonary hemodynamics (invasive catheters) were similar after versus before AVR. Aortic valve area increased significantly (p<0.05) with AVR (0.92 ± 0.26 cm(2) to 1.94 ± 0.35 cm(2)), concomitant with decreases in peak and mean gradients (60 ± 17 mmHg to 15 ± 8 mmHg and 38 ± 11 mmHg to 8 ± 5 mmHg, respectively) and peak blood flow velocity (3.9 ± 0.5 m · s(-1) to 1.9 ± 0.5 m · s(-1)). AVR reduced Z(va) (4.6 ± 1.0 mmHg · mL(-1) · m(-2) to 3.5 ± 0.3 mmHg · mL(-1) · m(-2)) and improved energy loss index (0.55 ± 0.16 cm(2) · m(-2) to 1.58 ± 0.48 cm(2) · m(-2)) concomitant with a decline in stroke work loss (25% ± 6% to 7% ± 4%), but systemic arterial compliance remained unchanged (0.63 ± 0.13 compared with 0.70 ± 0.12 mL · mmHg(-1)· m(-2)). CONCLUSION: The current results showed that AVR acutely reduced Zva, improved energy loss index, and decreased stroke work loss, but did not affect systemic arterial compliance in elderly men with degenerative calcific trileaflet AS. Published by Elsevier Inc.
OBJECTIVE: Standard methods of quantifying aortic valve stenosis (AS), which focus entirely on the valve itself, do not adequately characterize the magnitude, predict the onset, progression, and severity of symptoms, or identify the incidence of subsequent adverse events. Valvuloarterial impedance (Z(va)) is an index of global left ventricular (LV) afterload that incorporates valvular and arterial loads. The authors tested the hypothesis that aortic valve replacement (AVR) reduces Z(va) but does not affect the arterial component of LV afterload in elderly patients with degenerative calcific trileaflet AS. DESIGN: Observational study. SETTING: Veterans affairs medical center. PARTICIPANTS: Eight elderly (age, 79 ± 4 years) men with moderate-to-severe AS and normal preoperative LV function (ejection fraction, 61% ± 9%) scheduled for AVR with or without coronary artery bypass graft surgery were studied after institutional review board approval. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A comprehensive TEE examination was performed during isoflurane-fentanyl-rocuronium anesthesia. Doppler echocardiography was used to measure pressure gradients across the aortic valve, stroke volume (continuity equation), and aortic valve area using standard techniques. Z(va) was determined as (systolic arterial pressure+mean gradient)/stroke volume index. Energy loss index was calculated as (aortic area × aortic valve area)/([aortic area--aortic valve area]× body surface area). The stroke work loss was obtained as (mean gradient × 100/[systolic arterial pressure+mean gradient]). The ratio of stroke volume index to pulse pressure was used to measure systemic arterial compliance. Z(va), energy loss index, stroke work loss, and systemic arterial compliance were assessed before and 15 minutes after cardiopulmonary bypass. Systemic and pulmonary hemodynamics (invasive catheters) were similar after versus before AVR. Aortic valve area increased significantly (p<0.05) with AVR (0.92 ± 0.26 cm(2) to 1.94 ± 0.35 cm(2)), concomitant with decreases in peak and mean gradients (60 ± 17 mmHg to 15 ± 8 mmHg and 38 ± 11 mmHg to 8 ± 5 mmHg, respectively) and peak blood flow velocity (3.9 ± 0.5 m · s(-1) to 1.9 ± 0.5 m · s(-1)). AVR reduced Z(va) (4.6 ± 1.0 mmHg · mL(-1) · m(-2) to 3.5 ± 0.3 mmHg · mL(-1) · m(-2)) and improved energy loss index (0.55 ± 0.16 cm(2) · m(-2) to 1.58 ± 0.48 cm(2) · m(-2)) concomitant with a decline in stroke work loss (25% ± 6% to 7% ± 4%), but systemic arterial compliance remained unchanged (0.63 ± 0.13 compared with 0.70 ± 0.12 mL · mmHg(-1)· m(-2)). CONCLUSION: The current results showed that AVR acutely reduced Zva, improved energy loss index, and decreased stroke work loss, but did not affect systemic arterial compliance in elderly men with degenerative calcific trileaflet AS. Published by Elsevier Inc.
Entities:
Keywords:
aortic valve stenosis; energy loss index; hemodynamics; left ventricular afterload; systemic arterial compliance; valvuloarterial impedance