J Nucl Cardiol. 2024 Mar 29:101854. doi: 10.1016/j.nuclcard.2024.101854. Online ahead of print.
ABSTRACT
BACKGROUND: Myocardial flow reserve (MFR) by positron emission tomography (PET) is a validated measure of cardiovascular risk. Elevated resting rate pressure product (RPP = heart rate x systolic blood pressure) can cause high resting myocardial blood flow (MBF), resulting in reduced MFR despite normal/near-normal peak stress MBF. When resting MBF is high, it is not known if RPP-corrected MFR (MFRcorrected) helps reclassify CV risk. We aimed to study this question in patients without obstructive coronary artery disease (CAD).
METHODS: We retrospectively studied patients referred for rest/stress cardiac PET at our center from 2006-2020. Patients with abnormal perfusion (summed stress score > 3) or prior coronary artery bypass grafting (CABG) were excluded. MFRcorrected was defined as stress MBF/corrected rest MBF where corrected rest MBF = rest MBF x 10,000/RPP. The primary outcome was major cardiovascular events (MACE): cardiovascular death or myocardial infarction. Associations of MFR and MFRcorrected with MACE were assessed using unadjusted and adjusted Cox regression.
RESULTS: 3,276 patients were followed for a median of 7 (IQR 3-12) years. 1,685 patients (51%) had MFR < 2.0, and of those 366 (22%) had an MFR ≥ 2.0 after RPP correction. MFR < 2.0 was associated with an increased absolute risk of MACE (HR 2.24 [1.79-2.81], p<0.0001). Among patients with MFR < 2.0, the risk of MACE was not statistically different between patients with a MFRcorrected ≥ 2.0 compared with those with MFRcorrected < 2.0 (1.9% vs 2.3% MACE/year, HR 0.84 [0.63-1.13], p=0.26) even after adjustment for confounders (p=0.66).
CONCLUSIONS: In patients without overt obstructive CAD and MFR< 2.0, there was no significant difference in cardiovascular risk between patients with discordant (≥2.0) and concordant (<2) MFR following RPP correction. This suggests that RPP-corrected MFR may not consistently provide accurate risk stratification in patients with normal perfusion and MFR < 2.0. Stress MBF and uncorrected MFR should be reported to more reliably convey cardiovascular risk beyond perfusion results.
PMID:38606610 | DOI:10.1016/j.nuclcard.2024.101854
