ambulatory blood pressure monitoring (ABPM)

Indications

• assessment of 'white coat' hypertension
• borderline hypertension with target-organ damage
• abrupt changes in blood pressure, episodic hypertension
• hypotensive symptoms with treatment of chronic hypertension
• possible nocturnal rise in blood pressure
  • due to inadequate duration of antihypertensive therapy
• hypertension resistant to drug therapy
• possible autonomic dysfunction
  • heart rate patterns do not correlate with blood pressure
• reference standard for confirming a diagnosis of chronic hypertension

Contraindications

• not indicated for evaluation of prehypertension
• potentially offending medications (NSAID example)

Reference interval

• 24 hour average blood pressure < 115/75 mm Hg
• daytime average blood pressure < 120/80 mm Hg
• nighttime average blood pressure < 100/65 mm Hg

Clinical significance

• goals: daytime systolic BP < 135 mm Hg; night systolic BP < 125 mm Hg
  • systolic BP goals correspond with threshold for treatment with antihypertensive agent
  • systolic BP correlates more with all-cause & cardiovascular mortality than diastolic BP
• results correlate with left ventricular hypertrophy better than office-based measurements
• 24 hour ambulatory BP appears to have independent prognostic value, beyond that office measurements
  • better predictor of cardiovascular outcomes than office-based blood pressure measurements, including left ventricular hypertrophy & cardiac death
  • hypertension assessed by ambulatory blood pressure monitoring is associated with a higher risk of cardiovascular death than hypertension determined in the office or at home
  • 24 hour ambulatory systolic BP better predictor of all-cause & cardiovascular mortality than clinic systolic BP
  • nighttime systolic BP better predictor of all-cause & cardiovascular mortality than daytime systolic BP (24 hour ambulatory monitoring)
  • patients with masked hypertension at risk for excess all-cause mortality whereas patients with white-coat hypertension are not
• for each level of office BP, 24 hour systolic BPs of > 135 mm Hg have 2-3 fold increased risk of adverse cardiovascular events
• mean 24 hour BPs are generally lower than mean of office-based BPs, 21/9 mm Hg in one study
• ambulatory BP is, on average, 7/2 mm Hg higher than clinic BP
• 15-20% of ambulatory BP measurements elevated not a concern if average ambulatory BP ok
• nocturnal blood pressure should be ~15% lower than daytime blood pressure (example of 16%/12% lower nocturnal BP ok)
• nocturnal hypertension may be more predictive of mortality
• increased systolic BP during sleep is associated with higher risks for stroke & cardiovascular disease
• a graphene bioimpedance tattoo placed over the radial artery & ulnar artery, just above the wrist can monitor arterial blood pressure for > 300 minutes with high accuracy

Notes

• cost-effective in primary care
• home blood pressure monitoring may be an acceptable alternative
• Proof BP calculator suggested as a surrogate for ambulatory blood pressure monitor

More general terms

• clinical procedure