EFFECTS OF ANTIHYPERTENSIVE THERAPY ON LEFT ATRIAL FUNCTION

Objectives: To investigate left atrial (LA) function as a reservoir, a s a conduit and as a booster pump in essential hypertension (EH). LA v olumes were echocardiographically measured in 28 untreated hypertensiv e patients and in 20 control subjects. Background: LA makes a large co ntribution in left ventricular filling, especially in patients with im paired diastolic function. LA function is fundamental in left ventricu lar filling in hypertensive patients as hypertension results in left v entricular diastolic dysfunction. Methods: Diagnosis of EH (blood pres sure >140/90 mm Hg) was based on three repeated readings of blood pres sure (BP). Patients with myocardial infarction, cardiomyopathy, valvul ar or congenital heart disease were excluded. Doppler diastolic early (E) and late (A) velocity of mitral inflow were measured. The followin g indexes were calculated: left ventricular mass index (LVMI) using th e Penn convention; left ventricular stroke volume (LVSV); LA reservoir volume (LARV=LA maximal volume at mitral valve opening minus minimal volume); LA conduit volume (LACV=LVSV-LARV). Atrial systolic function was assessed by calculating the active emptying fraction (volume at on set of atrial systole minus minimal volume/volume at onset of atrial s ystole, the E/A ratio and the LA ejection force (0.5 rho A(2) MOA, whe re rho=the density of blood, MOA=mitral orifice area from the paraster nal short axis view). Measurements were obtained in all hypertensive p atients before and after 16 weeks administration of either enalapril ( 10 or 20 mg) or enalapril +/- chlorthalidone (20/25 mg) once a day. Re sults: After 16 weeks of treatment, BP was reduced significantly (from 172/110 to 137/86 mm Hg, P<0.001). LVMI decreased significantly as we ll (from 141 to 123 g/m(2)) although it was higher compared to control s (94 g/m(2), P<0.001). LARV decreased significantly (from 35.4 to 29. 3 cm(3), P<0.05) while LACV increased significantly (from 43.8 to 51.3 cm(3), P<0.05). LA active emptying fraction and E/A ratio did not cha nge. LA ejection force decreased significantly (from 20.9 to 18.1 kdyn es, P<0.05) but it was greater than controls (16.7 kdynes, P<0.01). Th ere was a positive relationship of LVMI to LARV (P<0.01) in controls ( r=0.77) which held true in hypertensive patients, before (r=0.72) and after treatment (r=0.69). There was a negative relationship of LVMI to LACV (P<0.01) in controls (r=-0.65), and in hypertensive patients unt reated (r=-0.74) and after treatment (r=-0.72). Conclusions: Our resul ts showed that in hypertensive patients, LA reservoir function increas es and LA conduit function decreases, while LA ejection force increase s. Antihypertensive treatment with enalapril and/or thiazide, induces normalisation of the LA function in parallel to left ventricular hyper trophy regression.