A large new study in European Heart Journal: Cardiovascular Imaging reveals that elevated resting myocardial blood flow (MBFrest) and reduced myocardial flow reserve (MFR) are powerful predictors of death and heart failure (HF) hospitalization, especially in patients with higher ejection fractions (EFs). The findings suggest that blood flow abnormalities can reveal the hidden cardiovascular danger even when heart pumping function appears normal.

Researchers analyzed data from 8,089 patients who underwent stress/rest myocardial perfusion imaging (MPI) using rubidium-82 PET scans between 2019 and 2024. Patients were followed for a median of 519 days. During that time, 466 deaths and 819 heart failure hospitalizations were recorded.

The study used advanced statistical models to evaluate how resting MBF and MFR affected outcomes while adjusting for traditional cardiovascular risk factors. Both high MBFrest and low MFR were independently associated with significantly enhanced risk of the primary outcome (a combined measure of death and HF hospitalization). Patients with high MBFrest had a 39% greater risk, and those with low MFR had a 70% greater risk.

The effect of these blood flow markers varied depending on EF. At an EF of 40%, the hazard ratio (HR) for high versus low MBFrest was 1.24. But at EF levels of 70%, the HR jumped to 2.46. Similarly, for MFR, the HRs for low versus high reserve increased from 1.57 to 3.13 across the same EF range. The study reported a higher death risk or risk of heart failure hospitalization with a higher MBFrest across the EF spectrum at constant MFRs.