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.

Aims: 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 the LV size and the TID ratio (TIDr) amongst females with normal SPECT MPI.

Methods and results: Retrospective single-centre study of female patients with normal dipyridamole stress MPI, defined as the 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 the 20th percentile of the study cohort. TIDr was derived using the quantitative perfusion SPECT software. 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, 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 the resting EDV and the TIDr (r = -0.34, P < 0.001), which remained significant after controlling for age, body mass index, resting left ventricular ejection fraction, 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.