Prognostic Significance of Noninvasive Simultaneous Renal and Cardiac Perfusion: Interrogating Mechanisms of Cardiovascular-Kidney Interactions

BACKGROUND: Physiologic interaction between the cardiovascular and renal systems is pivotal in the understanding of disease and as a target for therapeutic interventions, as highlighted in the cardiovascular-kidney-metabolic syndrome. This study explores the association of renal blood flow, derived noninvasively from cardiac positron emission tomography–computed tomography, with cardiovascular and renal outcomes. METHODS: We evaluated the association between renal blood flow and outcomes in a retrospective cohort of 295 consecutive patients who underwent 13 N-ammonia positron emission tomography–computed tomography myocardial perfusion imaging between September 1, 2019, and March 1, 2020 (Brigham and Women’s Hospital, Boston). Global myocardial blood flow, myocardial flow reserve, semiquantitative coronary artery calcium, and previously validated resting renal blood flow were obtained, along with clinical and laboratory data. Patients were followed for 4.0 (interquartile range, 1.7–4.1) years for a composite cardiovascular outcome of all-cause mortality, heart failure hospitalization, or acute coronary syndrome, and a composite renal outcome of 25% reduction in estimated glomerular filtration rate or end-stage renal disease. Survival analyses were adjusted for demographic and clinical characteristics and additionally for estimated glomerular filtration rate and myocardial flow reserve. RESULTS: The population had a mean age of 65.6 years, a body mass index of 29.2 kg/m 2 , and was 49% female. Overall, 36% had chronic kidney disease stage ≥3. Patients were stratified into 3 renal blood flow groups: ≥75%, 25 to 75th, and ≤25% percentile. Lower renal blood flow was significantly associated with a higher risk of cardiovascular events (adjusted hazard ratio, 5.21 [95% CI 1.53–17.75]; P =0.008; lowest versus highest quartile), and with an elevated risk of adverse renal outcomes ( P =0.026), independent of estimated glomerular filtration rate and myocardial flow reserve. CONCLUSIONS: Impaired renal blood flow is associated with cardiac and kidney events, independent of the highly prognostic estimated glomerular filtration rate and myocardial flow reserve. Simultaneous quantification of cardiac and renal perfusion by noninvasive 13 N-ammonia positron emission tomography–computed tomography may provide a valuable tool to interrogate pathophysiology and prognosis in the cardiovascular-kidney-metabolic syndrome.