Pickering BP PDF
Topic: Blood pressure measurement and detection of hypertension.
Measurement modalities: clinic (sphygmomanometer), self-recorded home BP, ambulatory BP monitoring.
Sphygmomanometer: A device used to measure blood pressure, typically consisting of an inflatable cuff and a manometer.
Key issues: discrepancies between clinic and non-clinic measurements; white-coat effect; reliability improved by more readings/visits and by reducing digit-preference.
White-coat effect: A phenomenon where a patient's blood pressure is elevated during a clinical visit due to anxiety, but is normal in other settings.
Quantitative points:
Correlation between clinic and ambulatory systolic BP in normotensives is higher with more clinic visits: r = 0.78 for a single visit vs r = 0.87 with three visits.
Self-monitoring pros/cons:
Pros: removes white-coat distortion; allows many readings over time.
Cons: limited diagnostic/prognostic data; potential observer error (mitigated by automatic devices, though accuracy concerns remain).
Ambulatory monitoring: tolerable devices, ~up to 100 readings over 24\text{ h}; accurate at rest but less during activity; provides data on level and variability.
Ambulatory BP monitoring: A method of measuring blood pressure at regular intervals over a 24-hour period using a portable device, providing readings during daily activities and sleep.
Overall implication: clinic BP remains central, but self-monitoring and ambulatory monitoring can improve assessment, especially when clinic readings are unclear or discordant with organ damage.
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Figure 1 (clinic vs home BP): in normotensives, little difference; in hypertensives, clinic pressure tends to be higher.
Self-monitoring: two fold potential advantages (white-coat distortion eliminated; multiple readings over time) and disadvantages (limited diagnostic/prognostic data; observer error risk).
Observation bias: hypertension diagnosed by clinic BP can overestimate true BP due to selection bias.
Ambulatory monitoring: provides 24-hour profile; more readings yield a better sense of BP level and variability; average ambulatory BP is often lower than clinic BP in hypertensives, and some patients show normal ambulatory BP (white-coat hypertension).
Risk prediction: ambulatory BP correlates more closely with target organ damage across >30 cross-sectional studies; some prospective data (e.g., Perloff et al.) suggest better morbidity risk prediction when ambulatory pressures are included alongside clinic pressures.
Target-organ damage: Damage to organs such as the heart, kidneys, brain, or eyes, caused by prolonged high blood pressure.
Bottom line: Ambulatory monitoring is increasingly accepted clinically, but cost and potential for overuse warrant consideration.
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Diurnal pattern: BP is activity-dependent; higher during work hours, lower at home; highest BP typically 0600–1200 h.
Diurnal pattern: The natural daily cycle of blood pressure fluctuations, typically higher during waking hours and lower during sleep.
Hypertensives show a reset of the diurnal profile to a higher level, but often preserve the normal pattern; absolute short-term variability is increased, but percent changes are similar to normotensives.
Short-term variability: Fluctuations in blood pressure that occur over short periods (e.g., within minutes or hours), often influenced by activity and emotional state.
Antihypertensive treatment tends to reset the set point toward normal with little effect on short-term variability.
Nocturnal pattern: some hypertensives lose the normal nocturnal fall (non-dippers); this occurs in various conditions and is linked to higher risk, though not all findings are ready for routine use.
Non-dippers: Patients whose nocturnal blood pressure does not fall by at least 10% from their daytime average, which is associated with higher cardiovascular risk.
Three potential contributors to adverse effects of hypertension: (a) average/true BP level; (b) diurnal variation; (c) short-term variability. Evidence strongest for the average level.
Non-dippers and some gender differences (e.g., non-dipping in women) may associate with higher future risk, but these findings are not universally adopted in practice.
Normal ambulatory BP: defining a universal upper limit is challenging; risk-based thresholds are preferred.
Most experts recommend treatment above a daytime ambulatory level of 140/90\text{ mm Hg}; a smaller number recommend treating above 135/85\text{ mm Hg}.
White-coat hypertension: about \approx 0.2 (20%) of patients with mild hypertension show elevated clinic BP but normal daytime ambulatory BP; more common with age >60.
Prognosis: white-coat hypertensives generally have less target-organ damage than sustained hypertension; some evidence suggests lower morbidity when ambulatory BP is low relative to clinic BP; drug treatment is often unnecessary.
Sustained hypertension: Consistently high blood pressure readings both in clinic and during out-of-clinic (home or ambulatory) measurements.
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Decision framework (Figure 3): evaluate hypertensive patients using clinic, home, and ambulatory measurements.
Persistently raised clinic BP with target-organ damage: typically continue treatment without further measurement uncertainty.
If clinic BP is raised but ambulatory/home readings are lower, white-coat hypertension is suspected; ambulatory monitoring clarifies risk.
If home readings are similar to clinic readings, treat as indicated; if home readings are much lower, work BP may still be elevated.
Ambulatory monitoring provides the best estimate of BP range in daily life.
Guidelines context:
British Hypertension Society recognizes ambulatory monitoring for evaluating white-coat hypertension in specialist centers.
JNCV (and related) accepts self-monitoring and lists white-coat hypertension as a situation where ambulatory monitoring may help.
American College of Physicians supports self-monitoring but discourages routine ambulatory monitoring.
Conclusions: BP measurement is central to hypertension management but should be augmented with home/ambulatory monitoring when discrepancies exist between clinic BP and organ damage, or when white-coat hypertension is suspected. Management may be less aggressive in white-coat cases if ambulatory BP is normal.
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References underpinning the concepts (e.g., white coat hypertension prevalence, ambulatory BP-validation studies, diurnal BP studies, and guideline reports).
Core takeaway: clinic BP will remain primary for the foreseeable future, but combining clinic with home/ambulatory measurements improves accuracy, risk stratification, and treatment decisions, particularly in suspected white-coat hypertension or discordant findings between organ damage and clinic BP.