Prognostic value of myocardial flow reserve vs corrected myocardial flow reserve in patients without obstructive coronary artery disease

Daniel M Huck; Brittany N Weber; Jenifer M Brown; Diana Lopez; Jon Hainer; Ron Blankstein; Sharmila Dorbala; Sanjay Divakaran; Marcelo F Di Carli

doi:10.1016/j.nuclcard.2024.101854

Prognostic value of myocardial flow reserve vs corrected myocardial flow reserve in patients without obstructive coronary artery disease

J Nucl Cardiol. 2024 Apr 7:101854. doi: 10.1016/j.nuclcard.2024.101854. Online ahead of print.

Authors

Daniel M Huck¹, Brittany N Weber², Jenifer M Brown³, Diana Lopez⁴, Jon Hainer⁵, Ron Blankstein⁶, Sharmila Dorbala⁵, Sanjay Divakaran⁷, Marcelo F Di Carli⁸

Affiliations

¹ From the Cardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United states. Electronic address: dhuck@bwh.harvard.edu.
² From the Cardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United states. Electronic address: https://twitter.com/@bweber04.
³ From the Cardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United states. Electronic address: https://twitter.com/@JeniferBrown.
⁴ From the Cardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United states. Electronic address: https://twitter.com/@BWHCVImaging.
⁵ From the Cardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United states.
⁶ From the Cardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United states. Electronic address: https://twitter.com/@RonBlankstein.
⁷ From the Cardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United states. Electronic address: https://twitter.com/@SanjayDivakaran.
⁸ From the Cardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United states. Electronic address: https://twitter.com/@mdicarli.

PMID: 38606610
DOI: 10.1016/j.nuclcard.2024.101854

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 (MFR_corrected) 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 to 2020. Patients with abnormal perfusion (summed stress score >3) or prior coronary artery bypass grafting (CABG) were excluded. MFR_corrected 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 MFR_corrected with MACE were assessed using unadjusted and adjusted Cox regression.

Results: 3276 patients were followed for a median of 7 (IQR 3-12) years. 1685 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 an MFR_corrected ≥2.0 compared with those with MFR_corrected <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.

Keywords: Coronary microvascular disease; Myocardial flow reserve.