Papillary muscles. Dark side of the heart: A simple approach for a forgotten structure

Transthoracic echocardiography (TTE) is currently the election method for initial screening of left ventricular papillary muscles (PM). However, diagnosis of borderline PM hypertrophy with TTE is not always feasible due to cumbersome interpretation of different PM diameters and the absence of precise normal ranges in the literature. The objective of this study was to obtain TTE normal cutoff values and to describe convenient indexes of PM dimensions.

Healthy volunteers with normal electrocardiogram were included for TTE assessment. Vertical (Vd) and horizontal (Hd) PM diameters were measured to obtain maximum diameter (Md) and areas of the anterolateral PM (APM) and posteromedial PM (PPM) to obtain PM total area (PMTA).

A total of 82 patients were screened, and 6 (7.3%) with bifid PM were excluded from analysis. APM and PPM had similar Vd (APM: 8.3 ± 1.2, PPM: 7.9 ± 1.1 mm² , P = NS) and Hd (APM: 8.2 ± 1.3, PPM: 8.3 ± 1.2 mm² , P = NS). Finally, Md (9 ± 1.2 mm; P95 = 11 mm) and PMTA (106.5 ± 24.2 mm² ; P95 = 150.8 mm² ) were obtained. Correlation between PMTA and Md was positive (P < .001), and out-of-range values for Md and PMTA were similar (2.6% vs 5.3%); there was excellent agreement between both indexes (K = 0.82).

Maximum diameter and PMTA are convenient indexes to describe PM dimensions. However, given the high equivalence between both indexes, we propose the use of Md due to its simplicity and ease of calculation. Our findings suggest that patients with any PM diameter ≥12 mm should be considered abnormal.