The aim of this study is to try to evaluate the relationship between arterial hypertension and ischemic heart disease (IHD) in the light of the physiopathologic response pattern to the dipyridamole echocardiography test (DET) in hypertensive patients, in pharmacologic washout, without any electrocardiographic ST segment depression during exercise tests or at rest. Sixty patients affected by mild to moderate asymptomatic essential arterial hypertension were studied: the subjects had a sitting diastolic blood pressure > or = 95 < or = 114 mmHg; there were 38 men and 22 women with a mean age of 49.8 +/- 7.6 years (range twenty-nine to sixty-eight). All patients had undergone high-dose DET (0.84 mg/kg in ten minutes). No patients developed side effects or asynergy in cardiac contractility during the test. In the absence of any significant coronary artery obstruction assessed angiographically, 18 patients (30%) showed ST segment depression > 1.0 mV during DET, sometimes with the presence of ventricular and/or supraventricular extrasystoles. In this group of patients the left ventricular mass index (LVMI) and duration of hypertension (in months) were higher as compared with those of the other 42 patients (respectively: 160.2 +/- 5.1 vs 129.2 +/- 9.2 g/m2, P < 0.02; and 30 +/- 4.8 vs 9 +/- 5.4 months, P < 0.007). In conclusion it is reasonable to speculate from these data that the ischemic-like" dipyridamole-induced ST segment depression, like that shown by patients affected by Syndrome X, might involve a worse prognosis in hypertensive patients. This may be because of increased coronary resistance due to structural modification or anatomic background.