In patients with pulmonary arterial hypertension (PAH), cardiac magnetic resonance imaging (MRI) metrics are capable of identifying individuals at low risk for 1-year mortality, making cardiac MRI an effective additive risk stratification tool in this population, according to study results published in the American Journal of Respiratory and Critical Care Medicine.
The ASPIRE (Assessing the Spectrum of Pulmonary Hypertension Identified at a Referral Centre) cardiac MRI database was used to identify consecutive patients with PAH (n=438) undergoing cardiac MRI between April 2012 and March 2017. After imaging, operators who were blinded to patient diagnoses and cardiac catheter results analyzed imaging. Investigators identified thresholds in a discovery cohort, which were then assessed in a test cohort.
Cardiac MRI parameters were evaluated in the discovery cohort for their associated risk for 1-year mortality. Both univariate and multivariate analyses of demographics, hemodynamics, and MRI parameters were performed among the whole cohort. To determine whether cardiac MRI could be an additional risk stratification tool, the researchers also calculated the REVEAL 2.0 Risk Score and number of low-risk criteria by the French Pulmonary Hypertension Registry in the incident population. Electronic data from the National Health Service Personal Demographics Service provided mortality data.
A total of 63% of patients were stratified as low risk (<5%) of 1-year mortality, using a right ventricular end systolic volume index percentage predicted threshold of 227%. A left ventricular end diastolic volume index of 58 mL/m2 was also capable of identifying 34% of patients at low risk for 1-year mortality. Several right ventricular ejection fraction (RVEF) thresholds were also established for identifying 1-year mortality risk.
An RVEF of >54% identified 21% of patients as low risk, an RVEF of 37% to 54% identified 43% of patients as intermediate risk, and an RVEF of <37% identified 36% of patients as high risk. The use of right ventricular end systolic volume index percent predicted improved risk stratification for 1-year mortality when used with the REVEAL 2.0 risk score calculator or a modified French Pulmonary Hypertension registry approach.
Limitations of the study included the relatively small sample size, as well as the lack of external validation of the MRI metrics for predicting 1-year mortality in patients with PAH.
The findings from this study provide clinical relevance for the care of the patients with PAH, the researchers wrote, as the “[i]dentification and maintenance of a low-risk status remains the goal of current treatment strategies.”
Lewis RA, Johns CS, Cogliano M, et al. Identification of cardiac MRI thresholds for risk stratification in pulmonary arterial hypertension [published online October 24, 2019]. Am J Respir Crit Care Med. doi:10.1164/rccm.201909-1771OC