Moderate Correlation between Central Aortic Pressure and Non-Invasive BP Monitoring in Patients Supported with Left Ventricular Assist Device Therapy

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BackgroundThe present gold standard for non-invasive measurement of blood pressure in patients supported on continuous-flow left ventricular assist device (CF-LVAD) therapy is Doppler sphygmomanometry. However, the relationship with central aortic pressures is unknown.HypothesisNon-invasive blood pressure measurements will systematically underestimate central aortic pressures.MethodsWe evaluated patients on CF-LVAD therapy undergoing left heart catheterization at our institution between 2015 and 2018 for any indication. We correlated non-invasive mean blood pressure measurements (NIBP-MAP) with catheter-derived mean central aortic pressures (Ao-MAP), and attempted to stratify by putative variables.ResultsIn a cohort of 55 patients with available NIBP data, we found a NIBP-MAP of 81.1 ± 12.5 mmHg and an Ao-MAP of 81.3 ± 10.8 mmHg. There was a significant albeit moderate correlation between NIBP and AoP (R2 = 0.52, p < 0.0001) with a tendency of NIBP to underestimate Ao-MAP at high and low Ao-MAP values. This association did not vary by pump type (R2 = 0.55 for HM2 and R2 = 0.47 for HW, both with p<0.001). The mean absolute difference between NIBP-MAP and Ao-MAP was 7.4 ± 4.8 mmHg, and the range of differences between Ao-MAP and NIBP-MAP values was -20 mmHg to +18 mmHg. A narrower aortic pulse pressure weakened the correlation but narrower pulse pressure on NIBP did not affect the correlation. Disagreement between NIBP-MAP and Ao-MAP was not affected by age, gender, BMI, aortic valve opening, LVAD type, or speed (p=ns for all).ConclusionsCorrelations between NIBP measurements and AoP pressures are moderate but NIBP does not systematically over- or underestimate central pressures. Further work should seek to improve on current methods of measuring blood pressure and determine the role of invasive monitoring for longitudinal management. The present gold standard for non-invasive measurement of blood pressure in patients supported on continuous-flow left ventricular assist device (CF-LVAD) therapy is Doppler sphygmomanometry. However, the relationship with central aortic pressures is unknown. Non-invasive blood pressure measurements will systematically underestimate central aortic pressures. We evaluated patients on CF-LVAD therapy undergoing left heart catheterization at our institution between 2015 and 2018 for any indication. We correlated non-invasive mean blood pressure measurements (NIBP-MAP) with catheter-derived mean central aortic pressures (Ao-MAP), and attempted to stratify by putative variables. In a cohort of 55 patients with available NIBP data, we found a NIBP-MAP of 81.1 ± 12.5 mmHg and an Ao-MAP of 81.3 ± 10.8 mmHg. There was a significant albeit moderate correlation between NIBP and AoP (R2 = 0.52, p < 0.0001) with a tendency of NIBP to underestimate Ao-MAP at high and low Ao-MAP values. This association did not vary by pump type (R2 = 0.55 for HM2 and R2 = 0.47 for HW, both with p<0.001). The mean absolute difference between NIBP-MAP and Ao-MAP was 7.4 ± 4.8 mmHg, and the range of differences between Ao-MAP and NIBP-MAP values was -20 mmHg to +18 mmHg. A narrower aortic pulse pressure weakened the correlation but narrower pulse pressure on NIBP did not affect the correlation. Disagreement between NIBP-MAP and Ao-MAP was not affected by age, gender, BMI, aortic valve opening, LVAD type, or speed (p=ns for all). Correlations between NIBP measurements and AoP pressures are moderate but NIBP does not systematically over- or underestimate central pressures. Further work should seek to improve on current methods of measuring blood pressure and determine the role of invasive monitoring for longitudinal management.