[Acute electrocardiographic effects of minoxidil in hypertensive subjects]

Unexplained ST-T segment (ST-TD) or T wave depressions (TWD) in the electrocardiogram (EKG) are seen during minoxidil therapy. To study the possible cause of this phenomenon 69 essential systemic hypertensive patients were evaluated. At the 5th day of a double therapy (DT) period consisting in the administration of atenolol 100 mg/day and chlorthalidone 50 mg/day systolic blood pressure (SBP), Sokoloff Index (SI) (EKG: Svl + Rv5-v6), EST-T (sum of ST-TD and TWD areas in 9 derivations of EKG) and potassium (K) serum levels were determined. Minoxidil (10 mg/day) was added and 3 to 6 days after, all parameters were repeated. Patients were classified in group A: (GA, n25 =) or B: (GB, n = 44) at the end of the study according to the absence or presence of ST-TD or TWD, respectively. During DT, SBP and SI were lower in GA (145.3 +/- 20.9 mm of Hg and 23.8 +/- 7.5 mm, respectively): (all values in X and S) than GB (173.5 +/- 24.4 and 34.0 +/- 8.3 respectively) (p less than 0.001 for both values) delta SBP (X and S of changes at the end of the study) diminished more in GB (-40.7 +/- 22.2 mm of Hg, p less than 0001) than in GA (-20.1 +/- 15.0, p less than 0.001) (GB-GA p less than 0.001). Correlation coefficient of SBP -delta SBP in both groups and delta SBP-delta EST-T in GB was 0.75 and 0.66 (p less than 0.001 for both values) respectively. delta K was not significant. Twenty five out of 27 patients of GB didn't have stenotic lesions by coronariography. Minoxidil induced ST-TD or TWD may be due to a fall in coronary perfusion pressure in patients with left ventricular hypertrophy and poor coronary circulatory reserve. This hipothesis implies that coronary autoregulation is lost in this stage of disease.