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Non-Invasive Ultrasonographic Cardiac Output Measurement in Pulmonary Arterial Hypertension

Yuri Matusov

Natalie Achamallah

Jeffrey Sager


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Conference: 2018 PHA International PH Conference & Scientific Sessions

Release Date: 06.28.2018

Presentation Type: Abstracts

File Download: Conference 2018_1035

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2018 International PH Conference and Scientific SeAbstract presented at the 2018 International PH Conference and Scientific Sessions in Orlando, Fla., June 28-July 1, 2018.

Purpose

To determine whether cardiac index (CI) measured by the UltraSonic Cardiac Output Monitor (USCOM) system correlates with CI obtained using standard invasive hemodynamic measurement methods (thermodilution and the Fick method) during right heart catheteriz

Background

Pulmonary hypertension (PH) and pulmonary arterial hypertension (PAH) are defined by hemodynamic parameters according to the World Health Organization (WHO). Hemodynamic parameters help guide treatment decisions and risk stratify patients. Low CI is associated with poor survival; the lung allocation score uses low CI as an exception to prioritize patients on the lung transplant list. Right heart catheterization is the current gold standard to determine hemodynamic parameters. Data from RHC are used to determine CI using the Fick and thermodilution methods. No validated non-invasive method exists to our knowledge in this group of patients. The USCOM is a portable, continuous-wave ultrasound device. The probe is placed at the sternal notch and directed at the aortic valve. A velocity time interval is measured by enveloping the pulsed systolic flow profile through the valve and multiplying this by a standardized cross-sectional aortic valve area to derive cardiac index, stroke volume index, and heart rate. USCOM is clinically validated in critically ill adults, children, cardiac surgical (including transplant) and post-surgical patients, and has shown good correlation with thermodilution, echocardiography and pre-set artificial heart parameters.

Methods

Adult (> 18-year-old) patients admitted to our facility for a RHC who were suspected of having WHO Group 1 or 4 PAH were enrolled. USCOM measurements of CI were taken within 30 minutes of RHC. CI obtained by USCOM was compared to CI derived from Fick and thermodilution methods. All measurements were taken by two trained physician investigators. Patients were excluded if they did not meet criteria for Group 1 or 4 PAH based on RHC data. Correlation between methods determined using the Pearson correlation method, with statistical significance determined by t-test. Bland-Altman plots were used to analyze the agreement between the USCOM, Fick, and thermodilution methods.

Results

In this preliminary data set, a total of 17 patients were enrolled and underwent RHC. Three did not meet criteria for WHO Group I or IV PAH. Average age of the remaining 14 patients was 52 years, and 13 (93%) were female. CI determined by USCOM and the Fick method had a Pearson correlation of 0.61 (p = 0.018), and CI by USCOM and thermodilution had an agreement of 0.74 (p = 0.0026); the Fick and thermodilution agreement was 0.76; p = 0.00162 (Fig 1). Bland-Altman plots demonstrated that all but one value were within the limits of agreement for USCOM with both Fick and thermodilution (Fig 2).

Conclusions

Measurement of CI is vital in making decisions regarding treatment and prognosis in PAH. The USCOM system may provide a useful non-invasive tool for monitoring of cardiac function in this population. This preliminary data set demonstrates that, in WHO Group I and IV PAH patients, the non-invasive USCOM CI correlated with hemodynamics determined by invasive RHC. Notably, the USCOM and thermodilution CI had an agreement that was very similar to each other. Further studies are necessary to determine the utility of USCOM in PAH patients, and its potential role in the diagnosis and monitoring of treatment response in the outpatient setting.

 

Figure 1: Pearson correlates of USCOM vs Fick and thermodilution agreement

Figure 2: Bland-Altman plots of USCOM vs Fick and thermodilution (limits of agreement in hashed lines)