To investigate whether reduction in blood pressure has a beneficial effect on left atrial appendage (LAA) function, the authors evaluated 24 untreated systemic hypertensive patients with normal left ventricular systolic function in sinus rhythm at baseline and at 3 months after initiation of anti hypertensive therapy. They performed transthoracic and transesophageal echocardiographic examinations in hypertensive patients before and after treatment of hypertension. Three of the 24 patients had blood pressure that failed to respond to the regimen of antihypertensive therapy and were removed from the analysis. Of the remaining 21 patients, mean systolic and diastolic blood pressures at baseline were 170 +/- 18 and 104 +/-6 mm Hg, respectively, and fell significantly at 3 months to 141 +/- 10 and 90 +/-5 mm Hg, respectively, (p <0.001) after initiation of antihypertensive therapy. There was no significant change in heart rate with treatment (baseline 81 +/-8 and at 3 months 84 +/-9 beats/min). There was no significant change in left ventricular end-diastolic diameter, left ventricular ejection fraction, left ventricular wall thickness, or left atrial diameter from baseline (49 +/-4 mm, 58 +/-5%, 12 +/-1 mm, and 41 +/-4 mm, respectively) at 3 months (48 +/-5 mm, 59 +/-4%,12 +/-1 mm, and 40 +/-3 mm). The treatment caused a significant reduction in maximal LAA areas (6.3 +/- 13 cm(2) at baseline, 4.6 +/-0.7 cm(2) at 3 months, p <0.001), with a concomitant increase in LAA emptying velocity (44 +/-7 cm/sec at baseline, 60 +/-9 cm/sec at 3 months, p <0.001). In conclusion, these findings suggest that reduction in blood pressure with antihypertensive therapy could improve LAA function in hypertensive patients with normal left ventricular systolic function in sinus rhythm.