What added value does ambulatory blood pressure monitoring brings to the management of post renal transplantation hypertension?

Objective: To evaluate BP control, white coat hypertension (WCH) and abnormal circadian variability in a significant outpatient sample of renal transplant (RTx) subjects, normotensive at the last regular visit.

Methods: ABPM (Spacelab 90217) was performed every 15 min between 07:00-23:00 h and every 30 min between 23:01-06.59 h. in all patients (N = 68, 39M, S-Cr. = 153 +/- 49 mumol/l) normotensive at their last regular office BP (O-BP) measurement and with available BP records for the 12 months preceding RTx and 6 months preceding ABPM.

Results: BP values were frequently abnormal in this RTx cohort considered to have a satisfactory BP control. O-BP (measured with a Hawksley random-0 sphygmomanometer on the day of ABPM) was 135.5/80.6 mmHg, 47.1% of the patients with abnormal BP values. By comparison, ABPM showed a lower prevalence of uncontrolled BP: 44.1% for 24 h.-BP and only 35.3% for the daytime awake period, with values of 134.5/80.4 and 135.3/81 mmHg respectively (P = NS from O-BP). The prevalence of WCH was 12%. 24-h SBP is related to O-SBP (r = 0.71, P < 0.01) and Bland-Altman analysis demonstrates that > 95.6% of all differences between systolic ABPM and O-BP values are within +/- 2SD of the identity line. However, although 24-h DBP is equally related to O-DBP (r = 0.64, P < 0.01), on Bland-Altman analysis, 8.8% of the differences between diastolic ABPM and O-BP values are outside +/- 2SD of the identity line. Thus, systolic but not diastolic O-BP correlates with, and can be substituted to ABPM derived values. Non-dipping was frequent, regardless of the definition of normal nocturnal BP fall (10 mmHg or 10% of the daytime SBP): 82.4%, 89.7%. Even if normality was strictly defined as a night/day ratio < 0.90 for SBP and < 0.92 for DBP, non-dipping prevalence was high 73.5%, with more than one-third of the RTx patients having nocturnal hypertension (ratio > 1).

Conclusions: BP control is not optimal in one-third of a typical RTx population. Furthermore, nocturnal hypertension is a frequent and underestimated phenomenon in this population. There is a good agreement between ABPM derived and casual systolic values. Office measurements, due to WCH, are under-evaluating the quality and efficacy of the antihypertensive regimens.