Early morning surge and dipping status of blood pressure: are these of predictive value for silent myocardial ischemia?

Abstract

To investigate the predictive value of morning surge (MS) and dipping status of blood pressure (BP) for ST-segment depression (ST depression) in hypertensive persons, the combined 24-hour ambulatory BP measurement and Holter electrocardiographic recordings of 344 patients (132 women and 212 men, 60+/-12 years) were analyzed. The morning BP surge was calculated as mean systolic BP during the 2 hours after awaking minus the mean systolic BP during the 1 hour that included the lowest sleep BP. Depending on the percentage decrease in systolic BP at night, patients were subdivided into extreme dippers, dippers, nondippers, and risers. ST depression was defined as horizontal or descending ST depression of 1 mm of 1 minute duration and a 1-minute interval after the previous episode or 24-hour mean ST-segment value <-0.1 mV. ST depression was observed in 76 (22.1%) of 344 patients. The mean MS in patients with ST depression was with 25+/-15 mm Hg and not significantly different when compared with patients without ST depression (26+/-15 mm Hg). The prevalence of ST depression was not significantly different in dippers, extreme dippers, nondippers, and risers (20%, 23.5%, 23%, and 25.5%, respectively). Systolic and diastolic BP values during ST depression were significantly higher in the morning as compared with ST depression in the evening (149/84 mm Hg vs 138/78 mm Hg, P<.05). In the present study, MS and dipping status of BP were not associated with ST depression. ST depression was, however, characterized by significantly higher BP peaks in the early morning hours.

Figure 1

Circadian distribution of intermittent ST‐segment depressions.

Figure 2

Comparison of blood pressure (BP) parameters at the onset of ST depression between 6 am and 9 am (black bars) vs 6 pm and 9 pm (white bars). *t test: P<.05.

Figure 3

Comparison of pressure‐frequency product before, during, and after ST depression: dippers vs nondippers. Student t test: Pressure‐frequency product before, during, and after ST depression as compared with the corresponding 24‐hour mean value.