Abstract
3384
Introduction: Evaluation and treatment assessed only by morphological description are still challenging for patients with intermediate coronary stenosis. Myocardial blood flow quantification (MBFQ) using technetium labeled myocardial perfusion tracers and dedicated SPECT cameras has become clinically feasible. Myocardial flow reserve (MFR) quantified by dynamic SPECT (DySPECT), as a functional index, has proven to be associated with the anatomic extent and severity of coronary artery disease (CAD) but its prognostic value of intermediate coronary stenosis is still lacking.
Methods: Patients with suspected or known coronary artery disease who were scheduled for SPECT MPI were consented to receive an adjunct dynamic SPECT scan (Symbia T16, Siemens, USA) for MBFQ under the same rest and stress test. Subjects with intermediate coronary stenosis defined as a coronary lesion with a visually estimated percentage diameter stenosis ranging from 50% to 80% were included. Patients with prior revascularization or prior myocardial infarction (MI) were excluded. Image processing of MBFQ employed full physical corrections for reconstruction of DySPECT images, 1-tissue compartment for kinetic modeling, and corrections for 99mTc-Sestamibi extraction and rest rate-pressure-product to quantify stress global MBF, rest global MBF and global MFR using a dedicated SPECT MBFQ software (MyoFlowQ, Taiwan). Flow values in myocardium were further converted to corresponded flow statuses defined by the Gould’s flow diagram with slight modification. The primary end point of our study was defined as major adverse cardiac event (MACE), including all-cause death, stroke, acute coronary syndrome (ACS). Due to the low MACE incidence of patients with intermediate coronary stenosis, we used a secondary end point which defined as target vessel revascularization (TVR). In order to evaluate the prognostic association of global MFR as continuous values, univariable and multivariable Cox proportional hazard regression models were used and p< 0.05 was considered statistically significant.
Results: A total of 127 consecutive patients were prospectively enrolled from November 2016 to May 2019, excluded 5 missing patients, 7 patients with prior revascularization and 3 patients with prior MI, 112 patients (mean age 60.0 ± 7.7 years, M/F: 73/39) were finally analyzed. Among them, 54 patients had impaired global MFR (defined as global MFR< 2) whereas 58 patients had normal global MFR (defined as global MFR≥ 2). During a median follow-up of 45 months [IQR 37-49], 7 (6.3%) patients experienced MACE (0 all-cause death, 0 stroke, 7 ACS) and 16 (14.3%) patients occurred TVR. All MACE occurred in the patient group with a global MFR< 2. In the multivariable Cox regression analysis, global MFR was an independent predictor for MACE (adjusted HR 0.031, 95% CI 0.03-0.288, p = 0.002) and TVR (adjusted HR 0.291, 95% CI 0.119-0.715, p = 0.007), respectively (adjusted by age, sex, dyslipidemia, hypertension, diabetes, drinking history or family history of CAD). Kaplan-Meier analysis (Figure 1) showed significant reduced event-free survival (%) in global MFR< 2 group compared to global MFR≥ 2 group (log-rank: p=0.004).
Conclusions: In our cohort of patients with intermediate coronary stenosis, global MFR assessed by DySPECT could be an independent prognosis factor of MACE and TVR and further help clinical decision-making management.