Reliability and limitations of echocardiographic measurement of left ventricular mass for risk stratification and follow-up in single patients

OBJECTIVE: To investigate the clinical reliability of repeated measurements of left ventricular mass in a single patient. DESIGN: We used test-retest reliability analysis, within-class correlation and interval of agreement measures. METHODS: Two M-mode tracings (three consecutive cycles) were recorded in the same session and 3-10 days apart (5+/-2 days; mean +/- SD) in 261 participants (age 45+/-13 years, body mass index 24.7+/-3.6 kg/m2; 131 hypertensive and 130 normotensive; 50% of each group women) in 16 centres in Italy. The two tracings were read by two observers in each centre, after classification by a three-order quality score (1 = poor, 2 = sufficient, 3 = optimal). RESULTS: The average quality score was 2.11+/-0.71 (21% poor, 50% sufficient, 29% optimal). Left ventricular mass values ranged from 56 to 419 g (170+/-61 g). On the same day, within-observer 90% interval of agreement between tracing 1 and tracing 2 was -28 to +22 g (-17 to +11% of tracing 1). For day-to-day test-retest within-observer variability (average three cycles), the 90% interval of agreement was -30 to +35 g (-18 to +18%). This variability decreased to -13 to +12% at the 80% interval of agreement and -12 to +11% at the 75% interval of agreement. The 90% interval of agreement of test- retest between-observer variability was -26 to 30 g (-19 to +15%). A negligible regression toward the mean was identified. Categorical consistency of retest in the identification of hypertensive patients with left ventricular hypertrophy, classified in the first study, was 87% (k = 0.87). CONCLUSIONS: Measurement of left ventricular mass in single patients allows reliable risk stratification on the basis of the presence of left ventricular hypertrophy. The probability of a true change in left ventricular mass over time is maximized for a single-reader difference greater than 18% of the initial value, although differences of 10-13% might also have clinical relevance.