White coat hypertension is more risky than prehypertension: important role of arterial wave reflections

Abstract

Arterial aging may link cardiovascular risk to white coat hypertension (WCH). The aims of the present study were to investigate the role of arterial aging in the white coat effect, defined as the difference between office and 24-hour ambulatory systolic blood pressures, and to compare WCH with prehypertension (PH) with respect to target organ damage and long-term cardiovascular mortality. A total of 1257 never-been-treated volunteer subjects from a community-based survey were studied. WCH and PH were defined by office and 24-hour ambulatory blood pressures. Left ventricular mass index, carotid intima-media thickness, estimated glomerular filtration rate, carotid-femoral pulse wave velocity, carotid augmentation index, amplitude of the reflection pressure wave, and 15-year cardiovascular mortality were determined. Subjects with WCH were significantly older and had greater body mass index, blood pressure values, intima-media thickness, carotid-femoral pulse wave velocity, augmentation index, amplitude of the backward pressure wave, and a lower estimated glomerular filtration rate than PH. Amplitude of the backward pressure wave was the most important independent correlate of the white coat effect in multivariate analysis (model r(2)=0.451; partial r(2)/model r(2)=90.5%). WCH had significantly greater cardiovascular mortality than PH (hazard ratio, 2.94; 95% confidence interval, 1.09-7.91), after accounting for age, sex, body mass index, smoking, fasting plasma glucose, and total cholesterol/high-density lipoprotein-cholesterol ratio. Further adjustment of the model for amplitude of the backward pressure wave eliminated the statistical significance of the WCH effect. In conclusion, the white coat effect is mainly caused by arterial aging. WCH carries higher risk for cardiovascular mortality than PH, probably via enhanced wave reflections that accompany arterial aging.

Keywords: arterial aging; arterial wave reflections; cardiovascular mortality; prehypertension; white coat hypertension.

Figure 1

Selection of study population. ABPM = ambulatory blood pressure monitoring.

Figure 2

Means and standard errors of the age-adjusted target organ indices for normotension (NT), pre-hypertension (PH), white coat hypertension (WCH), and sustained hypertension (SH): (A) left ventricular mass index (LVMI); (B) carotid intima-media thickness (IMT); (C) estimated glomerular filtration rate (eGFR); (D) carotid-femoral pulse wave velocity (PWV); (E) carotid augmentation index (AIx); (F) amplitude of the backward pressure wave (Pb). a : P < 0.05 in comparison with NT; b: P < 0.05 in comparison with PH; c: P < 0.05 in comparison with WCH.

Figure 3

Regressions of white coat effect on (A) age and (B) amplitude of the backward pressure wave, Pb, in total population (solid dots and solid lines) and subjects with white coat hypertension (WCH, hollow dots and dash lines). Model r²=0.043 and 0.137 for total and WCH cohorts, respectively in Panel A, and 0.411 and 0.504 for total and WCH cohorts, respectively in Panel B, all P<0.001.

Figure 4

(A) Cardiovascular disease survival curves by blood pressure categories. *: Log Rank P < 0.05 for white coat hypertension (WCH) or sustained hypertension (SH) vs. normotension (NT); †: Log Rank P < 0.05 for WCH or SH vs. pre-hypertension (PH). (B) WCH was stratified by the amplitude of the carotid backward pressure (Pb, median value 17.7 mmHg). *: Log Rank P < 0.05 vs. PH.