Abnormal left ventricular ejection fraction and heart rate reserve can predict both reduced non-corrected and corrected coronary flow reserve: a retrospective cohort study

Background: Recently, supra-normal left ventricular ejection fraction (snLVEF, LVEF higher than 65%) and blunted heart rate reserve (HRR, a surrogate marker for autonomic dysregulation) were found to correlate with reduced non-corrected coronary flow reserve (CFR). Their predictive value requires further verification.

Methods: Patients were categorized according to LVEF: snLVEF higher than or equal to 65%; nLVEF (normal LVEF) 55%-65%; and rLVEF (reduced LVEF) less than 55%. Additional subgroup comparison by HRR (HRR% less than 35% defined as abnormal) allowed further categorization according to LVEF/HRR status (LVEF-/HRR-, LVEF+HRR-/ LVEF-HRR+, LVEF+/HRR+). Quantitative flow parameters (including corrected CFR), cardiac function, and dipyridamole-induced chronotropic responses were compared among groups. Finally, logistic regression for reduce non-corrected and corrected CFR were done in total cohort and LVEF higher than 55% subgroup, with potential covariates including age, sex, body mass index, comorbidities, rest and stress rate-pressure product, small heart, coronary morphology abnormity, and LVEF/HRR status.

Results: A total of 210 patients (104 women, 106 men) underwent clinically indicated ¹³N-ammonia rest/dipyridamole stress ECG-gated myocardial perfusion imaging by positron emission tomography between 2015 and 2020. Both non-corrected and corrected CFR were significantly reduced in the snLVEF compared to the nLVEF. No difference of HRR% among the three groups was found. Abnormal HRR displayed significantly lower corrected rest flow, stress flow and non-corrected CFR. For subgroup analysis, quantitative flow parameters of abnormal HRR in snLVEF did not differ with normal HRR. For the three different LVEF/HRR analyses, the LVEF+/HRR+ group displayed significantly reduced corrected rest flow, stress flow and non-corrected CFR than the other two groups, and displayed significantly reduced corrected CFR versus the LVEF-/HRR- group. There was no significant difference between group LVEF-/HRR- and group LVEF+HRR-/LVEF-HRR+. Logistic regression analysis results suggested LVEF+/HRR+ was the only significant risk factor regardless of non-corrected or corrected reduced CFR, both in the total cohort and LVEF higher than or equal to 55% subgroup.

Conclusions: Abnormal LVEF and HRR can predict both reduced non-corrected and corrected CFR, which correlated with worse prognosis.