Utilizing dynamic myocardial perfusion scintigraphy for the evaluation of microvascular changes in hypertrophic cardiomyopathy

Background / Objective Myocardial perfusion scintigraphy (MPS) with SPECT has been playing a crucial role in non-invasive investigation of ischemic heart disease. Almost all technological aspects of this study have been improved. From the initially used two-dimensional scanning to ring-shaped solid state gamma cameras with CZT detectors and computed tomography (CT) attenuation correction. As expectations for diagnostic precision rise, conventional MPS sometimes fails to deliver an accurate assessment of potential ischemia. The goal of out study was to assess the feasibility of dynamic MPS using a ring-shaped solid-state SPECT/CT camera. Methods This is a continuous prospective study of patients with clinically proven hypertrophic cardiomyopathy (HCM). All patients underwent dynamic MPS using a ring-shaped solid-state SPECT/CT camera (Veriton-CT, Spectrum Dynamics) to evaluate possible microvascular changes. MPS was conducted using a one-day rest-stress protocol, with standard 99mTc-Sestamibi doses. Dynamic and static image registration with ECG synchronization and low dose chest CT for attenuation correction were performed. Images were assessed by an experienced nuclear medicine physician using the QGS/QPS software package. Dynamic images yielded information of stress and rest coronary blood flow (CBF) and coronary flow reserve (CFR). Results 22 patients were enrolled. 5 were omitted because of faulty bolus injection during dynamic imaging phase. For the remaining 17 patients, CBF and CFR data were obtained for all the coronary artery territories and a global score. Left ventricle was divided to 17 myocardial segments according to AHA for the regional analysis. Stress CBF was considered normal if it was >1.5g/ml/min per coronary artery territory, rest CBF >0.5g/ml/min. CFR was calculated by dividing stress CBF with rest CBF and was considered normal >2.0. 4 patients had decreased total CFR, 5 decreased CFR in LAD, 6 in LCX and 4 in RCA. Total stress CBF was decreased for 9 patients, 7 in LAD, 5 in LCX and 8 RCA. Total rest CBF was decreased for 9 patients, 9 in LAD, 9 in LCX and 10 RCA. Conclusions This is a small sample size prospective study with a very specific patient HCM population. Abnormal dynamic MPI findings occurred in around 47% of the patients. Discrepancy of abnormal regional perfusion findings and quantitative dynamic data in MPI need to be further evaluated, either by myocardial perfusion positron emission tomography or invasive testing.