Prevalence and circadian variations of ST-segment depression and its concomitant blood pressure changes in asymptomatic systemic hypertension

Abstract

Coronary artery disease is a major complication of hypertension; one of its manifestations is silent ischemia. The aim of this study was to assess the prevalence and circadian distribution of ST-segment depression together with concomitant blood pressure (BP) and heart rate variations. One hundred patients (male:female ratio 1:1) with a mean age (±SD) of 51 ± 8 years underwent ambulatory monitoring using the combined AMP 5600 monitor which simultaneously records a continuous Holler electrocardiogram and intermittent noninvasive BP measurements at 15-minute intervals, with extra measurements triggered by detection of a horizontal or downsloping ST depression (>1 mm and >60 seconds). Cardiovascular risk factors were fully evaluated in all patients; accurate and reliable echocardiogram enabled left ventricular mass index to be calculated in 52 patients. Twenty-three patients (15 men and 8 women) experienced a total of 72 episodes of ST depression. Duration of such episodes (mean ± SD) was 132 ± 65 seconds and amplitude was 1.51 ± 0.55 mm. Circadian distribution showed 2 peaks: on awakening and in the late afternoon periods. The mean ambulatory BP load was greater in the patients with than without ST-segment depression for both systolic and diastolic BP (135 ± 14 vs 129 ± 15 and 84 ± 8 vs 79 ± 10 mm Hg, respectively; p < 0.01). Plasma glucose (5.83 ± 0.70 vs 5.46 ± 0.71 mmol/L; p = 0.04) and self-rated work-related stress levels (22% vs 13%; p = 0.03) were also higher in patients with ST-segment depression. There were no significant differences between groups for clinical parameters, left ventricular mass index, and other cardiovascular risk factors. During ST depression episodes, systolic BP increased by 9 ± 15 mm Hg, diastolic BP by 7 ± 11 mm Hg, and heart rate by 5 ± 17 beats/min. Thus, 24-hour Hoher electrocardiographic monitoring showed ST depression episodes in 23 of 100 hypertensive patients (23%); ambulatory BP load was greater in these patients. BP variations, and mainly its elevation, may trigger such episodes of ST-segment depression.