O87 CONCORDANCE BETWEEN NOCTURNAL CARDIAC OUTPUT ESTIMATED WITH A NOVEL NON-INVASIVE METHOD USING BRACHIAL OSCILLOMETRIC BLOOD PRESSURE MEASUREMENTS AND ECHOCARDIOGRAPHY

Background and Objective: Nocturnal hypertension, characterized by elevated blood pressure (BP) levels during sleep as measured by 24-hour ambulatory blood pressure monitoring (24-h ABPM), has garnered increasing interest. However, understanding the explanatory mechanisms and non-invasive demonstration of these alterations poses challenges. We developed a non-invasive method to estimate cardiac output (CO) using brachial oscillometric BP measurements based on total arterial compliance (Ct). Yet, the agreement between estimated nocturnal CO and echocardiography-measured CO, considered the gold standard at rest, remains uncertain. This study aims to evaluate the concordance between the two methods. Methods: A cross-sectional study was conducted involving 216 adult patients who underwent Doppler echocardiograms and 24-h ABPM, regardless of valvular or cardiac pathology, or medication use, provided they had normal aortic valvular anatomy. Stroke volume was calculated as the product of the cross-sectional area of the aortic annulus and the average velocity of the left ventricular outflow tract. Using nocturnal BP and heart rate measurements from the 24-hour ABPM, along with weight, height, age, and sex, Ct and CO were estimated. Values were compared to determine validity. Results: Of the participants, 50.0% were men, with an average age of 54.0±14.0 years. Among them, three had a history of myocardial infarction, nineteen were diabetic, and one hundred thirty-six were hypertensive. CO measured by echocardiography averaged 4.9±1.0 L/min, ranging from 2.8 to 8.1 L/min. The agreement of CO between the new method and Doppler echocardiography was good, with an intraclass correlation coefficient of 0.421 (95%CI 0.305 to 0.525). The mean difference was 0.027±0.977 L/min (95%CI -0.104 to -0.157). Bland-Altman plots demonstrated that the differences between the methods were randomly distributed along the mean difference line (Figure). Conclusions: The novel method for estimating nocturnal CO based on Ct using brachial oscillometric BP measurements demonstrate validity across various clinical conditions. Its adoption in clinical settings could simplify the assessment of nocturnal hypertension with 24-h ABPM.