Echocardiography overestimates left ventricular mass in hemodialysis patients relative to magnetic resonance imaging

Background. Left ventricular hypertrophy (LVH) is a common finding and a strong adverse prognostic factor in patients with chronic renal failure. An accurate method of measuring left ventricular mass (LV mass) is therefore a prerequisite in the management of these patients. Recent evidence has suggested that echocardiography overestimates LV mass in patients with essential hypertension, and this error increases with increasing LV mass. Methods. We studied 35 patients on maintenance hemodialysis within 24 hours of their last dialysis. LV mass was measured by both echocardiography and magnetic resonance imaging (MRI) performed less than three hours apart. Clinic and ambulatory blood pressure (ABPM), resting echocardiogram, and blood sampling were performed at the same visit. Results. Thirty-two patients had results from both methods. Clinic blood pressure, ABPM, and QT dispersion all correlated with LV mass, with a stronger correlation observed for MRI values. Intraobserver and interobserver variability were significantly greater for echocardiography (although similar to other published data). Comparing the two methods, the difference in LV mass values (echo minus magnetic resonance) increased in a linear fashion with an increasing mean mass and chamber diameter. Conclusions. Echocardiography significantly overestimates LV mass relative to MRI in the presence of LVH and dilation. This overestimation is the result of assumptions made in the calculation of mass from echocardiography M-mode images, which are invalid when LV geometry is abnormal. This error is therefore amplified in dialysis patients, the majority of whom have LVH and in whom intravascular volume is constantly changing.