Abstract 13504: RV Cardiac Output Calculated From an Implantable Hemodynamic Device: A Correlative Approach Using CMR in PAH Patients
Introduction: The CardioMEMS™ HF System (CMHFS)(St. Jude) is used for wireless monitoring of pulmonary artery (PA) pressure. Pulmonary flow is difficult to model due to prominent reflected waves and McDonald et al have shown that the temporal differential of the initial positive pressure pulse effectively provides the flow driving force for cardiac output (CO), with mean pressure indicating resistance. However, the response of this model to stress conditions in vivo is unknown.
Hypothesis: We hypothesize that the temporal differentiation of pressure model of CO applied to the CMHRS data at baseline and during stress provides an accurate calculation of noninvasive CO in PAH.
Methods: 10 pts with PAH were implanted with the CMHFS to measure PA pressure, HR, and CO longitudinally. Cardiovascular Magnetic Resonance (CMR) was performed at baseline, and after 1) inhalation of nitric oxide (20 ppm), 2) dobutamine (20 μcg/kg/min), and 3) volumetric challenge (500ml NaCl). Flow through the MPA was measured using phase velocity mapping. The mean pressure and area of the temporal differential of the initial positive pressure pulse from the CMHFS device were measured (Fig 1A) to calculate CO. In each case the calibrating constant to relate to CMR CO was calculated at baseline and then applied during stress.
Results: The pressure derived CO correlated with CMR CO via a linear relationship for 32 comparison measures according to the following equation: Pressure CO = 1.1 CMR CO + 0.8Bland-Altman analysis has an offset bias of 0.2, a four standard deviation range of ±3.1 l/m and a correlation of 0.9. (Fig 1B).
Conclusions: The temporal differential of the initial positive pressure pulse forms the effective driving force for pulmonary blood supply. This formulation overcomes the difficulties in identifying reflected waves and is highly responsive to stress conditions and may advance current prototypes. This approach may provide additional value once validated for implantable PA manometers.
Author Disclosures: R.W. Biederman: Research Grant; Modest; NHLBI grant. M. Doyle: Research Grant; Modest; NHLBI grant. G. Rayarao: None. J. White: None. D. Thompson: None. J. Yamrozik: None. R. Williams: None. P. Correa-Jaque: None. R. Benza: None.
- © 2015 by American Heart Association, Inc.