Assessment of Right Atrial Size and Function by Cardiac CT

Introduction: Right atrial (RA) remodeling and failure is the final stage in the progression of heart failure (HF), after left ventricular (LV), left atrial (LA) and right ventricular (RV) failure. We aimed to evaluate the feasibility of measuring RA dynamics by cardiac CT and assess the effect of RA dysfunction on HF admissions and cardiac death.

Methods: 230 patients who underwent spiral CT and who had a recent echocardiogram were analysed and followed up for a mean of 3 years. Left and right atrial and ventricular volumes were automatically measured and functional parameters calculated. Specifically, RA total emptying fraction (RATEF)=(RA max volume–min volume)/max volume.

Results and discussion: Automatic RA segmentation was feasible in 85% of cases. Of the 200 remaining cases, 33% had a previous myocardial infarct and 38% had advanced diastolic dysfunction. Mean LV ejection fraction (EF) was 57±14% and mean RVEF was 48±8%. In 44 cases with normal echo, RA volumes were ~20% larger than corresponding LA volumes but RATEF was similar to LATEF (46+-8%). In all patients, RATEF was independently related to LATEF, RVEF and RV end-diastolic volume (p<0.01). RATEF correlated moderately with LATEF (r=0.44) and with RVEF (r=0.44). RA volumes correlated better with LA volumes (r=0.62-0.65). By univariate Cox analysis RATEF was inversely related to outcome (RR 0.97, [95%CI 0.94-0.995] per 1% increase) although RA early emptying fraction was a better predictor of outcome (RR 0.944, [95%CI 0.91-0.98] per 1% increase). In multivariate analysis RA function became non-significant alongside LATEF (RR 0.935 [95%CI 0.91-0.96] per 1% increase).

Conclusion: This pilot study demonstrates the feasibility of evaluating RA volume and function by cardiac CT. RATEF is related to both LA and RV function and is associated with a worse outcome. In the current population, RA function was not an independent predictor of outcome.