VALIDATION OF A BRACHIAL OSCILLOMETRY AND MODEL-BASED ESTIMATE OF STROKE VOLUME AGAINST MAGNETIC RESONANCE IMAGING

Abstract

Objective: Technological progress recently facilitated 24 hour measurement of central blood pressure and pulsatile hemodynamics, using brachial blood pressure cuffs and dedicated software. A complementary estimate of cardiac function is desirable. Design and method: Our proposed method mathematically describes left ventricular outflow during systole according to a given pressure wave. The model combines a modified 3-element like Windkessel system and transmission line theory, and provides an estimate of stroke volume (SV). For this study, pulse waves, recorded with a brachial cuff at the level of diastolic blood pressure, are utilized. In 97 patients with reperfused acute myocardial infarction and in 2 healthy controls, cardiac magnetic resonance imaging (CMRI; 1.5 Tesla Magnetom, Siemens, Germany) was performed, and SV was measured with standard protocols from short axis cine images (11 slices). Images were acquired using breath hold, retrospective ECG triggered TrueFISP bright blood sequences, and evaluated with standard software (ARGUS, Siemens, Erlangen, Germany). SV from both methods were compared with Pearson[Combining Acute Accent]s correlation coefficients and Bland Altman Plots. Results: Mean age of participants was 56.8 years, 21 were women, 56 smokers, mean nt-proBNP was 1350 pg/ml, mean EF 54% (range 28–76). MRI-derived SV was 76 ml (range 28.5–122), oscillometric device-derived SV was 67 ml (range 35–113). Both SVs was moderately correlated (r = 0.54 (CI 0.39–0.67), p < 0.001). Using the method of Bland-Altman, mean difference between both methods was 8.7 ml (1.96 limits of agreement were 36.7 and −19.3 ml), with no systematic bias - Figure. Both MRI-based and oscillometric method-based SV were inversely related to nt-proBNP levels (r = −0.31, p = 0.002 and r = −0.25, p = 0.01, respectively). Conclusions: Brachial oscillometry and mathematical modeling provide a reasonable estimate of stroke volume, which may be a useful addition to 24 hour measurements of blood pressure and pulsatile hemodynamics.