Valvuloarterial impedance, but not aortic stenosis severity, predicts syncope in patients with aortic stenosis.

BACKGROUND: The presence of syncope in patients with aortic valve stenosis (AS) predicts a grave prognosis. However, the evaluation of AS severity has been limited to valve-specific factors such as aortic valve area and mean transaortic pressure gradient. Recently, valvuloarterial impedance (Zva) was proposed for the estimation of global left ventricular afterload. Therefore, because predictors of syncope in patients with AS have not been investigated in recent years, we assessed the effect of clinical characteristics and echocardiographic parameters, including Zva, on syncope in patients with AS.

METHODS AND RESULTS: We retrospectively studied 451 patients with moderate and severe AS without low left ventricular ejection fraction (<40%). Patients with syncope (n=79; 18%) had higher Zva (5.1±0.9 versus 4.4±0.9 mm Hg/mL per m(2); P<0.001) than those without (n=372; 82%). However, no significant differences existed in the mean transaortic pressure gradient (P=0.076) or the aortic valve area (P=0.160) between the 2 groups. In the multivariable analysis, only Zva was an independent predictor of syncope in patients with AS (odds ratio, 2.02; 95% confidence interval, 1.54-2.64; P<0.001). However, systolic blood pressure, relative wall thickness, the early transmitral flow velocity to peak early diastolic mitral annular velocity ratio, and mean transaortic pressure gradient were not identified as independent predictors. Receiver operating characteristic curve analysis identified Zva ≥4.7 mm Hg/mL per m(2) as the cutoff value associated with syncope in patients with AS.

CONCLUSIONS: Our study suggests that high Zva, but not conventional parameters of AS, identifies AS patients with an increased risk of syncope.