FP690
APPARENT TREATMENT-RESISTANT HYPERTENSION IN THE HEMODIALYSIS POPULATION: AN AMBULATORY BP MONITORING (ABPM) BASED STUDY

INTRODUCTION: Hypertension notwithstanding the use of multiple antihypertensive drugs is an endemic problem in the hemodialysis (HD) population. However, to date there is no estimate of the prevalence of treatment-resistant hypertension based on ABPM in HD patients.

METHODS: We estimated the prevalence of apparent treatment-resistant hypertension (ATRH) in 527 HD patients in 7 nephrology units in Italy, Greece and Slovenia who underwent 48h ABPM recordings (the golden standard in this population). In a sub-group of 106 patients we tested the relationship between fluid overload (FO%, Fresenius Body Composition monitor BCM) measured pre and post HD and ATRH.

RESULTS: 307 out 507 (58%) patients were classified as hypertensive by 48hABPM criteria (>130/80 mmHg) and 83 of these (16% of the whole population and 27% of the hypertensive population) were on >3 drugs. The Odds for ATRH were higher in patients with relatively lower levels of hemoglobin [OR(1g/dl)=1.23, P=0.04] and pre-dialysis and post dialysis body weight [OR(1Kg)=1.02, P=0.01] suggesting that malnutrition may be a relevant factor underlying ATRH. No association between apparent treatment resistant hypertension and age, gender and other demographic and clinical parameters was found. Even though the proportion of overhydrated patients was higher among ATRH patients (14%) than among hypertensive patients who achieved normotension while on drug treatment (10%), the vast majority (86%) of HD patients with ATRH exhibited a normal hydration status. Overall, the excess risk for ATRH in post-dialysis overhydrated patients was 41% (OR=1.41, P=0.003) while pre HD over-hydration largely failed to predict ATRH (OR=1.05, P=0.58). Three hundred and eight patients (58%) had hypertension by routine predialysis BP measurements (>140/90 mmHg) and 230 (44%) by post-HD measurements. Post HD BP measurements had a higher sensitivity (76% vs 72%) and similar specificity (97% vs 98%) for the diagnosis of ATRH as compared to pre-HD BP measurements. However, the positive predictive value (both 95%) and negative predictive value (85% and 88%) of pre and post HD BP metrics were superimposable.

CONCLUSIONS: With the proviso that we did not measure adherence to drug prescription, this multicenter study based on state of art ABPM recordings further again confirms the pervasive nature of hypertension in the HD population and shows that ATRH occurs in about 1 in 4 hypertensive HD patients. Fluid overload is more common among patients with ATRH than in hypertensive patients who achieve normotension with drug treatment but overhydration per se only in small part explains ATRH in this population. These data represent a strong call for a closer surveillance to patients’ adherence to drug treatment and for new trials testing treatment strategies aimed at improving patients’ compliance.