Estimation of Total Cardiac Output Using Non-Invasive Parameters in HeartMate 3 Patients

Abstract

<h3>Purpose</h3> In patients on left ventricle assist device (LVAD) support, total cardiac output (CO) results from the summation of LVAD flow and native flow through the aortic valve. Our study aims to: 1) quantify discrepancies between LVAD flow and total CO, and 2) test a novel approach to estimate total CO using non-invasive parameters in patients implanted with a HeartMate 3 (HM3), a centrifugal pump that features intrinsic pulse technology to prevent stasis within the pump. <h3>Methods</h3> Patients implanted with a HM3 between 11/2014 and 12/2017 were retrospectively studied. CO by thermodilution (TD) was measured in triplicate and the average was used for subsequent analyses. A total of 17 concurrently acquired variables were considered as potential predictors of CO: age, gender, weight, BMI, BSA, hemoglobin (Hb), hematocrit, LVEF, LVEDd, SBP, DBP, MAP, HR, LVAD flow, speed, PI and power. A multiple linear regression model was fit with the above predictor variables and CO by TD as the dependent variable to derive the <i>HM3 CO Formula</i>. To assess validity of the <i>HM3 CO Formula</i> against CO by TD, Pearson's correlation coefficients (r), mean absolute difference (MAD) and mean observed difference (MOD) were calculated<i>.</i> <h3>Results</h3> 69 HM3 patients (age 60±11y, 84% male, ischemic 43%, BMI 29±5.4 kg/m²) were studied. LVAD flow had good correlation but poor agreement with total CO by TD (r= 0.455, p<0.0001; MAD±SE 1.33±0.13 l/min, MOD±SE 1.15±0.15 l/min, <b>Fig A</b>). The <i>HM3 CO formula</i> incorporating SBP, Hb, LVAD Power, and weight (CO = 1.197 + 0.028 x SBP -0.372 x Hb + 0.734 x power + 0.021 x weight) had better correlation and agreement with CO by TD (r= 0.714, p <0 .0001; MAD±SE 0.79±0.09 l/min, MOD±SE -0.05 ± 0.13 l/min, <b>Fig B</b>). <h3>Conclusion</h3> In HM3 patients, LVAD flow does not provide good estimate of total CO. The <i>HM3 CO Formula</i> offers an alternative method to estimate total CO using non-invasive parameters. Validation studies are warranted to confirm these preliminary findings.