Associations of inter-arm blood pressure difference with treatment response in newly treated hypertension

Objective: Inter-arm differences (IAD) in systolic blood pressure (SBP) predict future cardiovascular mortality and morbidity. IAD varies between measures and gets smaller with repeated measures. The relationship of IAD to response to antihypertensive treatment is unknown. We set out to examine associations of IAD with BP treatment response over 18 weeks in treatment-naïve adults with moderate to severe hypertension. Design and method: We previously reported that nurse-led accelerated stepwise management of treatment-naïve grade II/III hypertension is feasible, safe and effective, achieving control of SBP to < 140 mmHg for 76% after 18 weeks. Using this cohort, univariable associations of IAD (mean of 8 simultaneous BP measurements) with vascular and clinical indices, and with BP change on treatment, were examined with mixed-effects linear regression models. Candidate univariable indices (p<0.2) entered multivariable modelling. Regression modelling of change in IAD was undertaken. All analyses adjusted for age, sex and entry SBP. Results: For 52 participants (mean age 59; 42% female), mean (standard deviation: SD) entry SBP was 171 (13.9) mmHg falling, after protocol-led treatment intensification, to 131 (10.7) mmHg at 18 weeks; mean systolic IAD was 4.5 (4.2) mmHg at entry and 3.9 (4.3) mmHg at 18 weeks (p = 0.28). In final adjusted models, IAD at entry was associated with handedness, height, body mass index, smoking and absence of pedal pulses. Greater reduction of SBP from entry to 18 weeks was associated with lower entry IAD, greater SD of daytime ambulatory BP, smoking history and handedness. Adjusted change in IAD over 18 weeks was correlated with falls in SBP (Adjusted R2 = 0.56). Conclusions: These data associate greater systolic IAD with reduced response to intensive BP lowering, and correlate reduction in IAD with change in BP. Slower BP target achievement can carry prognostic implications, suggesting one possible mechanism whereby IAD might predict future mortality.