The differential blood pressure sign in general practice: prevalence and prognostic value

Patients sometimes have differences of > or =20/10 mmHg in their blood pressure depending on which arm is measured. The prevalence and prognostic value of this finding in general practice are unknown. If these differences are due to peripheral vascular disease, these patients may be at increased risk of cardiovascular or cerebrovascular events.

Our aim was to establish the frequency and prognostic value of a blood pressure difference between arms in one rural general practice.

Paired blood pressure readings were collected from patients attending the surgery. The outcome measures of myocardial infarction, new diagnosis of angina, a cerebrovascular event or death were recorded prospectively.

A total of 280 patients were examined, and of these 13.6% had a systolic blood pressure difference (SBPD) of > or =20 mmHg, and 23.2% a diastolic blood pressure difference (DBPD) of > or =10 mmHg. Eighty-three patients were followed-up for 5.6 years. Patients with a DBPD of > or =10 mmHg showed a mean event-free survival of 3.3 years [95% confidence interval (CI) 2.2-4.4] compared with 5.0 years (95% CI 4.7-5.3) for those with a DBPD of <10 mmHg (P < 0.0001). Patients with an SBPD of > or =20 mmHg showed a mean event-free survival of 3.5 years (95% CI 2.3-4.7) compared with 4.9 years (95% CI 4.5-5.2) for an SBPD of <20 mmHg (P = 0.043).

During a single assessment of blood pressure, there will be a minority of patients with a difference of > or =20/10 mmHg between their right and left arms. Measurement of both arms is therefore necessary to diagnose and treat hypertension accurately. This study suggests an association between blood pressure difference and increased morbidity and mortality. Priority should be given to managing other risk factors aggressively in those patients with a reproducible blood pressure difference of > or =20/10 mmHg.