Quantitation of Ventricular Morphology Provides Incremental Prognostic Utility in Patients Undergoing SPECT MPI

Background: Non-perfusion imaging variables have the potential to be a key component of risk stratification on single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). Shape index and eccentricity are quantitative markers of left ventricular morphology. However, their independent associations with major adverse cardiovascular events (MACE) are not well described.

Methods: Patients undergoing SPECT MPI between 2009 and 2014 from the REFINE-SPECT registry, with stress and rest gated supine acquisitions were studied. Shape index (ratio between the maximum LV diameter in short axis and ventricular length at end-diastole) and eccentricity (calculated from orthogonal diameters in short axis and length in end-diastole) were calculated at stress and rest. Deltas were calculated as stress minus rest. All quantitation of left ventricular morphology was performed automatically at the core laboratory and both shape index and eccentricity have previously been demonstrated to have excellent repeatability (r² >0.85).Multivariable Cox proportional hazards analysis was performed to assess independent associations with MACE (death, non-fatal MI, unstable angina, or late revascularization) after adjusting for demographics, co-morbidities, and imaging findings including left ventricular volume and function.

Results: In total, 14,016 patients, mean age 64.3 ± 12.2 and 8469 (60.4%) male, were included. MACE occurred in 2120 patients during a median follow-up of 4.3 years (interquartile range 3.4 - 5.7). Rest, stress, and delta shape indices and eccentricity were significantly associated with MACE in unadjusted analyses (all p<0.001). However, in multivariable models only delta shape index (adjusted HR 1.02, p<0.001) and delta eccentricity (adjusted HR 0.98, p=0.009) remained associated with MACE. Delta shape index and delta eccentricity had significantly improved classification of MACE in addition to a multivariable model including age, sex, medical history, stress parameters, perfusion, left ventricular volume, and left ventricular ejection fraction (continuous net reclassification 0.131 [0.074 - 0.181] and 0.122 [0.065 - 0.171], respectively).

Conclusions: Delta shape index and delta eccentricity were independently associated with MACE and improved risk estimation. Changes in ventricular morphology have important prognostic utility and should be included in patient risk estimation following SPECT MPI.

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