24hr Ambulatory Blood Pressure Monitoring (ABPM) Risk Stratifies Hypertensive Kidney Transplant Recipients (KTRs).

Abstract

Background and Methods: Systolic hypertension has been shown to be associated with adverse clinical outcomes after renal transplantation. In non-transplant patients, 24hr ambulatory blood pressure monitoring (ABPM) has been shown to be a superior predictor of clinical outcomes when compared to clinical blood pressure readings alone. In this study we have prospectively analysed129 kidney transplant recipients (KTR) diagnosed with hypertension based on the clinic blood pressure (CBP) of >130/80mm Hg. All these patients underwent ABPM and groups were stratified based on ABPM systolic (>/<130mm Hg) and diastolic blood pressure (</>80mm Hg) values (SBP & DBP). The primary outcome measure was a composite of graft loss, cardiovascular event or death over a 5year follow-up. Results: Of the 129 KTRs, only 64 had average 24hr SBP>130 mm Hg on ABPM. Overall, CBP significantly overestimated SBP even in the true hypertensive KTRs based on ABPM (CBP, 164± 16 mm Hg, ABPM, 143± 9 mm Hg, P<0.0001). Based on the ABPM readings, 33% of hypertensive KTRs required an increase in their anti-hypertensive therapy (P=0.01). Day time (P=0.002) and 24hr average SBP (P<0.001) were strongly associated with the composite end point in a univariate Kaplan Meier analysis. Whilst the 24hr average DBP (P=0.03) was significantly associated with poor event free survival, nocturnal dipper status was not significant. The influence of 24hr average SBP on event free survival was more significant in KTRs with diabetes (P=0.02), lower eGFR (P=0.001), proteinuria (P=0.007), who are younger (P=0.02) and female (P=0.01). Similar non-significant trends were seen with DBP as well. Despite a significant improvement in CBP in both the groups over 5 years, eGFR and proteinuria remained significantly worse in the true hypertensive group based on the assessment of ABPM during this period.Figure: No Caption available.Conclusions: To conclude, 24hr ABPM helps to risk stratify apparent hypertensive KTRs based on CBP. True hypertensives based on ABPM represent a significantly high risk population with adverse medium term outcomes despite appropriate therapy.