ABSTRACT
OBJECTIVE: Right ventricular function determines the prognosis of pulmonary hypertension (PAH). Measurement of stroke volume (SV) non-invasively could be a promising method to monitor disease progression. Cardiac magnetic resonance (CMR) imaging is recognized as an accurate and reproducible method to measure SV. Inert gas rebreathing (IGR) using acetylene is a validated but cumbersome method for pulmonary blood flow (PBF) measurement in PAH. A more convenient rebreathing technique using rapid photoacoustic analysis of nitrous oxide has been introduced and validated in left heart failure. We investigated the accuracy of CMR imaging and IGR using photoacoustic analysis to measure SV in patients under investigation for PAH. METHODS: Thirty-three patients (16â:17â) with suspected PAH following echocardiography had SV measured by CMR imaging (using pulmonary arterial{CMR PA} and aortic {CMR Ao} flow methods) and IGR. The results were compared with our reference standard: thermodilution (TD) measured during right heart catheterization (RHC). RESULTS: All methods showed similar correlation for SV. Bland-Altman analysis confirmed acceptable levels of agreement between the four techniques. TD versus CMR Ao flow had bias (limits of agreement) of -5.41 ml (-22.37 to 11.56 ml), TD versus CMR PA flow 0.12 ml (-20.13 to 20.37 ml) and TD versus IGR 6.25 ml (-16.01 to 28.51 ml). CONCLUSION: Cardiac magnetic resonance imaging and IGR using photoacoustic analysis in patients with suspected PAH provided non-invasive measurements of SV that agreed closely with those obtained from TD measured during RHC.
Subject(s)
Breath Tests , Hypertension, Pulmonary/diagnosis , Magnetic Resonance Imaging , Nitrous Oxide , Stroke Volume , Ventricular Function, Right , Administration, Inhalation , Adult , Aged , Blood Pressure , Cardiac Catheterization , Female , Humans , Hypertension, Pulmonary/physiopathology , Male , Middle Aged , Nitrous Oxide/administration & dosage , Predictive Value of Tests , Reproducibility of Results , Scotland , ThermodilutionABSTRACT
In patients with pulmonary arterial hypertension (PAH), right ventricular mass (RVM) correlates linearly with pulmonary artery pressure, and decreases with successful treatment. Accurate measurement of RVM currently requires cardiovascular magnetic resonance (CMR) imaging. We therefore tested the relationship between RVM and a simple, 12 lead ECG-derived value, the Butler-Leggett (BL) score. This has previously been validated in patients with RV hypertrophy (RVH) due to mitral stenosis. We also tested the diagnostic accuracy of the BL score in detecting RVH. The Scottish Pulmonary Vascular Unit database was reviewed retrospectively. Twenty-eight patients with PAH were identified, in whom CMR and ECG data had been recorded no more than 28 days apart. All had completed a comprehensive clinical assessment, including right heart catheterization. CMR-derived absolute RVM and RV mass index (RVMI=RV mass/LV mass) were correlated against BL score. The ability of this score to detect RVH was tested using 2 x 2 contingency tables. RVM and RVMI correlated with BL score (r=0.77, P<0.001 and r=0.78, P<0.001, respectively). A BL score >0.7 mV proved a highly specific but insensitive indicator of RVH, based on either absolute RVM (sensitivity 74%, specificity 100%) or a high RVMI (sensitivity 61%, specificity 100%). The BL score, which can be defined using a standard 12-lead ECG, correlates with RVM and RVMI in patients with PAH. A score >0.7 mV was a highly specific but insensitive indicator of RVH in these patients.
