The left ventricular end-systolic pressure-dimension relation in patients with thalassemia major. A new noninvasive method for assessing contractile state.

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Abstract
Transfusion-dependent patients with thalassemia major (TM) are at an extremely high risk for cardiomyopathy. Traditional tests of left ventricular (LV) systolic function performed in these patients do not distinguish derangements in loading conditions from abnormalities in contractile state. In this study, the LV end-systolic pressure dimension (PES-DES) relation, which is independent of preload, incorporates afterload and is highy sensitive to contractile state, was used to assess LV performance in 20 asymptomatic, chronically transfused patients, ages 7-25 yr, with TM. All patients had normal resting systolic time intervals and exercise duration on treadmill. Baseline resting percent fractional shortening (%.DELTA.D) on M-mode echocardiography (echo) was normal in 14 patients (group 1) and abnoral in 6 patients (group 2). Echo and carotid pulse recordings were made at rest and during i.v. infusion of methoxamine to alter LV afterload. DES was measured directly from echocardiography; PES was estimated from a calibrated carotid pulse tracing. The value for the slope of the PES-DES line was calculated for each patient. Values > 2 SD below the mean for 14 control subjects, ages 8-25 yr, were defined as abnormal. All group 2 patients and 4 of 14 group 1 patients had abnormal slopes. All patients < 13 yr of age had normal slopes, while all 7 patients .gtoreq. 15 yr had abnormal values. Three of 7 patients ages 13-15 yr had depressed slopes. On clinical follow-up (mean 12 .+-. 3 mo.), 2 of 10 patients with abnormal slopes developed overt signs of LV decompensation; all other patients remained asymptomatic. The noninvasive determination of the LV PES-DES relation in patients with TM appears to identify preclinical LV dysfunction not evident from resting or dynamic exercise studies. This test may be useful clinically for monitoring LV contractility in response to therapeutic interventions. Because of its insensitivity to loading conditions, it may have widespread clinical applicability for other patients at risk for cardiomyopathy, including those with chronic LV volume overload from valvular regurgitation.

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