Abstract 106: Paradoxical Increase in Office-Based Blood Pressure Measurement After a Brief Patient Rest Period

Abstract

BACKGROUND: Office-based blood pressure (BP) measurement is a snapshot of a patient’s ambulatory BP, and is subject to variations which may influence management. OBJECTIVE: To assess the effect of a brief rest period on repeat BP measurement. METHODS: Patient charts reviewed in University-based cardiology clinic identified 170 encounters which contained BP re-measurement data due to elevated initial BP of > 130/80 mmHg. BP was measured initially by a nurse, with the patient in a sitting position and the arm resting at the level of the heart. If BP was > 130/80 mmHg, it was repeated by physician after resting the patient for 15 minutes. Mean age was 64 ± 12 years. Results: Among encounters with BP re-measurement, initial systolic BP (SBP) was 153 ± 27 mmHg, and diastolic BP was 87 ± 16 mmHg. Upon re-measurement, 106 of 170 patients (62%) had lower SBP of 143 ± 23 mmHg compared with initial SBP of 162 ± 28 mmHg; a mean drop of 18 mmHg. However, 53 of 170 patients (31%) had higher SBP of 149 ± 17 mmHg compared with initial SBP of 138 ± 14 mmHg; a mean increase of 10 mmHg. Eleven patients (7%) had no BP change. In 50% (85/170) of encounters, BP re-measurement necessitated hypertensive medication changes. Compared with the remaining patients, those with paradoxical increase in BP were younger (60 ± 9 years versus 66 ± 13 years; p < 0.01), more females (57% versus 47%), and with lower initial SBP (134 ± 14 versus 160 ± 28, p < 0.01). DISCUSSION: Hypertension is a challenging public health problem. JNC 7 guidelines recommend that prior to BP measurement, persons should be seated quietly for at least 5 minutes in a chair, with feet on the floor, and arm supported at heart level; this may decrease initially elevated BP. However, 30% of our patients exhibited a paradoxical response, with elevation of the SBP after a 15 minute period of rest. The cause of this paradox is not clear, but may have resulted from white-coat hypertension during the rest period, which may be more common in younger patients, especially females, as noted in our study. This underscores the importance of ambulatory BP monitoring, especially in subsets of patients prone to having labile or white coat hypertension, to avoid the cost and side effects of BP overtreatment.