Association of intradialytic hypertension with future cardiovascular events and mortality in hemodialysis patients: effects of ambulatory blood pressure

Introduction: Intradialytic-hypertension (IDHTN) is associated with increased risk of adverse outcomes. Patients with IDHTN have higher 44-hour blood pressure (BP) than patients without this condition. Whether the excess risk in these patients is due to the BP rise during dialysis per se or on elevated 44-h BP or other co-morbid conditions is uncertain. This study evaluated the association of IDHTN with cardiovascular events and mortality and the influence of ambulatory BP and other cardiovascular risk factors on these associations. Methods: 242 hemodialysis patients with valid 48-h ABPM (Mobil-O-Graph-NG) were followed for a median of 45.7 months. IDHTN was defined as: SBP rise >= 10mmHg from pre- to post-dialysis and post-dialysis SBP >= 150mmHg. The primary end-point was all-cause mortality; the secondary endpoint was a composite of cardiovascular death, non-fatal myocardial infarction, non-fatal stroke, resuscitation-after cardiac-arrest, heart-failure-hospitalization, coronary or peripheral revascularization. Results: Cumulative freedom from both the primary and secondary endpoint was significantly lower for IDHTN patients (logrank-p=0.048 and 0.022, respectively), corresponding to higher risks for all-cause-mortality (HR=1.566; 95%CI [1.001, 2.450]) and the composite cardiovascular outcome (HR=1.675; 95%CI [1.071, 2.620]) in these individuals. However, the observed associations lost statistical significance after adjustment for 44-h SBP (HR=1.529; 95%CI [0.952, 2.457] and HR=1.388; 95%CI [0.866, 2.225], respectively). In the final model after additional adjustment for 44-h SBP, interdialytic-weight-gain, age, history of coronary-artery-disease, heart-failure, diabetes and 44-h PWV, the association of IDHTN with the outcomes was also not significant and the respective HRs were 1.377 (95%CI [0.836, 2.268]) and 1.451 (95%CI [0.891, 2.364]).Conclusions: IDHTN patients had higher risk for mortality and cardiovascular outcomes but this risk is at least partly confounded by the elevated BP levels during the interdialytic period.