Comparison between maximal left ventricular wall thickness and left ventricular mass in patients with hypertrophic cardiomyopathy

Background: Cardiovascular magnetic resonance enables accurate and reproducible assessment of left ventricular (LV) dimensions and function, free of geometric assumptions and limitations related to an inadequate acoustic window. In patients with hypertrophic cardiomyopathy (HCM), LV mass (LVM) and maximal LV wall thickness (MLVWT) have prognostic significance. Aim: To compare MLVWT and LVM in patients with HCM. Methods: The study population included 33 patients with HCM (17 males, mean age 48.5 +/- 16.5 years). Subjects after alcohol septal ablation or surgical myectomy were excluded from the study. The MLVWT and LVM were measured with the use of cardiac magnetic resonance. The MLVWT was determined with the use of the dedicated software in short axis slices after manual definition of endocardial and epicardial contours. The LVM was indexed for body surface area and expressed in g/m(2). Cut-off values for normal, mildly increased and markedly increased LVM were based on previously published studies. Results: Mean LVM in the whole study group was 107.4 +/- 30.9 g/m(2) (range 57.0-163.4 g/m(2)) and was higher in males than females (120.2 +/- 30.8 g/m(2) vs 93.8 +/- 25.3 g/m(2), respectively; p = 0.01). Mean MLVWT was 23.4 +/- 4.8 mm (range 16-36 mm). There was only a weak trend toward higher MLVWT in men when compared to women (24.8 +/- 5.4 mm vs 21.9 +/- 3.7 mm, respectively; p = 0.09). There was no correlation between LVM and MLVWT (r = 0.24; p = 0.17). A significant variability in LVM was observed in subjects with similar MLVWT; a greater than two-fold difference was noted in extreme cases. In three patients (9%; one female, two male) LVM was within the normal range and in another one female (3%) patient LVM was mildly increased. In the remaining patients (n = 29; 88%) markedly increased LVM was observed. Conclusions: The MLVWT does not reflect the degree of LV hypertrophy in patients with HCM. Patients with similar MLVWT may have substantial differences in LVM. A substantial group of patients with HCM is characterised by normal, or only mildly increased LVM, despite significant LV wall hypertrophy measured as MLVWT.