Relationship between left ventricular cavity size and transient ischaemic dilation ratio on dipyridamole stress single-photon emission computerized tomography myocardial perfusion imaging in a female asian population

Objective Single-photon emission computerized tomography (SPECT) myocardial perfusion imaging (MPI) has reduced accuracy in patients with small left ventricular (LV) size. Although transient ischaemic dilation (TID) is a sign of extensive coronary artery disease when accompanied by perfusion defects, its significance with normal perfusion remains unclear. We aim to study the relationship between LV size and TIDr amongst females with normal SPECT MPI. Methods Retrospective single centre study of female patients with normal dipyridamole stress MPI, defined as summed stress score = 0 with both stress and rest LV ejection fraction ≥50% on gated images. Small LV was defined as a gated rest end diastolic volume (EDV) below 20th percentile of the study cohort. TIDr was derived using Quantitative Perfusion SPECT software. Results There were 107 female patients (mean age 70) included. The threshold for small LV size was determined to be an EDV of < 36.6 mL. Patients with or without small LV were similar in age, ethnicity, body mass index (BMI) and comorbidities. TIDr was significantly greater for patients with small LV (1.33 vs. 1.28, p=0.042). There was a significant negative correlation between resting EDV and TIDr (r=-0.34, p<0.001) which remained significant after controlling for age, BMI, resting LVEF, diabetes mellitus and hypertension (r = -0.35, p < 0.001). Conclusion In females with a normal dipyridamole stress SPECT MPI, TIDr is significantly higher in those with small LV. LV size should be considered when interpreting TID in females with otherwise normal MPI.