To determine the importance for clinical decision of recognizing the inter-arm differences in blood pressure (BP) in hypertensive patients (HT).
Design and Method:
Cross-sectional study including 2000 HT (52.1% women), followed in primary care units and medicated for hypertension (HT). The usual BP measuring arm for each patient was identified. The BP and heart rate (HR) were measured simultaneously in both arms, after a 10 minutes rest period. The BP taken from the usual measuring arm was considered referential (refBP)
The mean discrepancy (BP-refBP) for systolic and diastolic BP were respectively 4.40 ± 12.01 mmHg and 1.62 ± 7.10 mmHg (p < 0.001), and the inter-arm discrepancies regarding systolic BP classes were respectively 1.71 ± 2.00 mmHg, 2.05 ± 7.60 mmHg, 3.51 ± 09.70 mmHg, 6.40 ± 13.81 mmHg and 8.80 ± 18.70 mmHg, for normal BP, normal-high BP, grade 1, grade 2 and grade 3 HT (p < 0.001), with similar but less marked distribution for diastolic BP (p < 0.001). The Bland-Altman analysis revealed a steady increase in the inter-arm differences to increasing levels of BP. In patients with uncontrolled hypertension, 67.65% had inter-arm differences above 10 mmHg. The overall diagnostic concordance in BP classification was moderate (ICC = 0.58; CI:0.59–0 .60, p < 0.001), with 13% patients changing BP classification from controlled (refBP) to uncontrolled HT; of these patients, 42% had differences above 15 mmHg, 25% between 10–15 mmHg, 21% between 5 -10 mmHg and 12% below 5 mmHg. Considering patients with uncontrolled HT, 28% of them were sub-classified in lower grades of hypertension based on the refBP. These results were independent of gender, presence of co-morbidities (diabetes, dyslipidemia) or history of cardiovascular events. Logistic regression analysis identified a significant association between inter-arm differences and prior cardiovascular events
The simultaneous measurement of BP in both arms is crucial in a very significant percentage of patients for a proper clinical decision