This cross-sectional, descriptive-analytical study was conducted on 750 patients, including 328 with a history of COVID-19 and 422 without. The participants were referred by cardiologists to the nuclear medicine center at Kowsar Hospital in Sanandaj, the main healthcare facility in Kurdistan Province, northwest Iran, for MPI. The study period spanned from April 6, 2020, to March 21, 2021. Medical records, including demographic details, clinical data, and MPI results, were reviewed for all participants.

The study protocol was reviewed and approved by the Ethics Committee of Kurdistan University of Medical Sciences (Ethics Code: IR.MUK.REC.1399.331). Written informed consent was obtained from all patients at the time of their admission for MPI. Ethical standards regarding patient confidentiality and research integrity were strictly adhered to throughout the study.

Baseline demographic information and cardiovascular risk factors were extracted from hospital documentation. This included data on age, gender, hypertension, diabetes mellitus, hyperlipidemia, obesity, smoking status, cancer history, diagnosed CAD, and family history of CAD. Diabetes mellitus was defined by the use of insulin or oral hypoglycemic agents, while obesity was classified as a BMI ≥ 30. Hypertension was identified as blood pressure ≥ 140/90 mmHg or the use of antihypertensive medications, and hyperlipidemia was defined as total cholesterol ≥ 6.2 mmol/L or the use of lipid-lowering medications. A family history of CAD was considered positive if a first-degree relative was diagnosed before the age of 55. Smoking status included both past and current tobacco use. Patients were classified as having CAD based on documented evidence such as prior myocardial infarction, chest pain, abnormal ECG, positive cardiac biomarkers, or a history of percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG). The lung-to-heart ratio (LHR) was calculated as the ratio of average counts from regions of interest in the left lung and heart, while time-intensity dynamics (TID) described temporal changes in signal intensity during imaging.

MPI was performed using a standard two-day stress-rest protocol. Patients refrained from beta blockers, calcium channel blockers, methylxanthines, dipyridamole, and caffeine-containing products for 24 h prior to the stress imaging. Pharmacological stress was induced with a 0.56 mg/kg dipyridamole infusion over three minutes, followed by a 11 MBq/kg Tc-99 m MIBI bolus injection. In cases of adverse reactions, the procedure was halted, and aminophylline was administered. For resting images, the Tc-99 m MIBI injection was administered the following day. Patients consumed high-fat foods (e.g., milk or cream) before imaging, which was performed 75–90 min post-injection.

Gated MPI was conducted using a SIEMENS SYMBIA EVO EXCEL gamma camera, acquiring 64 projection images at 3° intervals in a 180° anterior orbit. Image reconstruction was performed using “Myovation Evolution” software (OSEM with 12 iterations and 10 subsets), with corrections applied using filtered back projection and a Butterworth filter. MPI findings were analyzed by an experienced nuclear medicine specialist using QGS/QPS (Cedars-Sinai Medical Center) and 4DM software. A 20-segment myocardial model with a 5-point scoring system was employed to evaluate perfusion: 0 (normal), 1 (mildly reduced), 2 (moderately reduced), 3 (severely reduced), and 4 (no uptake). The summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) were calculated, with an SSS < 3 considered normal. Both quantitative metrics and qualitative expert observations were used to assess abnormalities.

Data normality was assessed using histograms and Shapiro-Wilks tests. Continuous variables were presented as mean ± standard deviation, while categorical data were expressed as percentages. Comparisons of continuous and categorical variables were conducted using Student’s t-tests and chi-square tests, respectively. A p-value < 0.05 was considered statistically significant. Statistical analyses were performed using IBM SPSS Statistics for Windows, version 24 (IBM Corp., Armonk, NY, USA).