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116 DETECTION OF PRECLINICAL LEFT VENTRICULAR DYSFUNCTION USING METHOXAMINE AFTERLOAD CHALLENGE IN PATIENTS WITH THALASSEMIA MAJOR

Cardiomyopathy is the major cause of death in patients(pt) with Thalassemia Major(TM). Standard tests of left ventricular(LV) function have not dependably identified pts with TM and cardiac dysfunction. Methoxamine afterload challenge with assessment of end systolic pressure(ESP)-dimension(ESD) relationships has been used to identify subclinical cardiac dysfunction in pts with structural heart disease. In an effort to detect early abnormalities in LV contractile reserve, 8 pts with TM, ages 6-18 years, underwent echocardiography(echo) during Methoxamine infusion. ESD was measured using standard methods. ESP was estimated from the dicrotic notch of a calibrated carotid pulse recording. All pts were asymptomatic with normal resting systolic time intervals, LV percent fractional shortening by echo and treadmill exercise capacity. ESP-D values were determined for each pt at various levels of afterload. The slope of the ESP-D curve was abnormal in 3/8 pts as defined by values > 2SD below the mean for 17 control pts. These 3 pts were the oldest subjects in the TM group. The use of Methoxamine to increase afterload in combination with readily available noninvasive techniques, offers a sensitive method of unmasking LV dysfunction not evident on standard resting or dynamic exercise tests. Serial studies using this technique may identify pts at risk for the development of cardiomyopathy.