Background:
Chronic renal hypoxia influences the progression of chronic kidney disease (CKD). Blood oxygen level dependent (BOLD) magnetic resonance (MR) is a noninvasive tool for assessment of renal tissue oxygenation. Beta blockers reduce cardiovascular mortality in patients with CKD and systolic heart failure, however the mechanisms of this benefit remain unclear. We sought to determine the association between beta blocker use, renal cortical and medullary oxygenation, and renal blood flow in hypertensive patients suspected of renal artery stenosis.
Hypothesis:
Chronic receipt of beta blockers will be associated with improved renal tissue oxygenation as assessed by BOLD MR.
Methods:
We measured renal cortical and medullary oxygenation using BOLD MR and renal artery blood flow using MR phase contrast techniques in 38 participants suspected of renal artery stenosis.
Results:
Chronic beta blocker therapy was associated with improved renal cortical (p=0.0007) and medullary (p=0.03) oxygenation (Figure). Receipt of angiotensin converting enzyme inhibitors or angiotensin receptor blockers was associated with reduced medullary oxygenation (p=0.01). In a multivariable model including gender, hemoglobin, diabetes, loop diuretic use, and mineralocorticoid use, chronic receipt of beta blockers was the only significant predictor of renal tissue oxygenation (β= 8.4, p=0.008).
Conclusions:
Beta blocker therapy was associated with improved renal oxygenation independent of renal blood flow suggesting may these findings may be related to reduced renal oxygen consumption. In addition to their known benefits to reduce cardiovascular mortality in patients with renal disease, beta blockers may reduce or prevent progression of renal dysfunction in patients with hypertension, diabetes, and renovascular disease. These observations may have important implications for treatment of patients with CKD.
Intermittent claudication and severe renal artery stenosis are independently associated in hypertensive patients referred for renal arteriography
