Myocardial ischemia during everyday life in patients with arterial hypertension: prevalence, risk factors, triggering mechanism and circadian variability.

INTRODUCTION

The objective of the present study was to investigate the prevalence, the risk factors, the hemodynamic triggering mechanisms, the circadian variability of ST segment depression (ST depression) and the effect of day and night fall in blood pressure on the prevalence of ST depression in hypertensive patients.

MATERIALS AND METHODS

In a multicentric study in Germany, 1,244 CardioTens registrations (combined 24-h ambulatory blood pressure measurement/electrocardiography with ST segment triggering; Meditech, Budapest, Hungary) from patients with arterial hypertension were consecutively monitored and evaluated centrally at the University of Bonn. Inclusion criterion was treated or untreated arterial hypertension. The ST segment was measured in accordance with the "1 : 1 : 1 rule" (horizontal or descending ST depression by 1 mm, 1 min duration, 1 min interval from the previous episode).

RESULTS

ST segment depression was observed in 250 (20.1%) patients; 90.3% of the transient ST-segment depression was silent (without angina pectoris). Ambulatory 24-h blood pressure measurement, but not office-based blood pressure measurement, was predictive for the occurrence of ST-segment depression. Risk factors for ST-segment depression were the Sokolow index > or =3.5 mV, smoking status, severity of coronary heart disease, use of diuretics, reduced left ventricular function, pulse pressure > or =60 mmHg and increase of double product (1,000 mmHg/min). A significant rise of the systolic/diastolic blood pressure (+8+ or -18/+7+ or -10 mmHg), of the heart rate (+12+ or -13/min) and of the double product (+2,471+ or -2,517 mmHg/min) was found during the transient ST depression as compared with the corresponding 24-h ambulatory blood pressure measurement mean values (P<0.0001 for all parameters specified). In most intermittent ST depressions, a rise of the double product was seen (n=789 episodes), and in the remaining 239 ST depressions, a fall of the double product was observed. ST depressions with fall of the double product showed a circadian distribution with a peak in the late evening. ST depression accompanied by a rise in double product showed two peaks (one in the early morning and one in the late evening). The prevalence of ST depression was significantly higher (28.6%) in extreme dippers than in dippers (18.2%), risers (21.8%) and non-dippers (19.6%).

CONCLUSIONS

ST depressions have a high prevalence of 20.1% in hypertensive patients. Clinical predictors for the occurrence of ST-segment depression were classical risk factors and cardiac target organ damage. Office-based blood pressure measurement was not a useful measuring tool for forecasting the likelihood of ST-segment depression. ST depressions were triggered inter alia by variations of blood pressure and the heart rate. The circadian variability of the ST depressions is crucially affected by the pressure double product characteristics on which the ST depression is based.