Late gadolinium enhancement gray zone in patients with hypertrophic cardiomyopathy. Comparison of different gray zone definitions.

To quantify heterogeneous tissue at the periphery of areas of fibrosis (gray zone) in patients with hypertrophic cardiomyopathy (HCM) with the use of two different techniques. Cardiac magnetic resonance with late gadolinium enhancement analysis was performed in 33 patients with HCM. Gray zone was evaluated with the use of two different techniques previously described in patients after myocardial infarction. LGE was present in 25 (78%) patients. There was no significant difference in total LGE mass at two different cut-off values [53.8 g (interquartile range, IQR 43.5-77.8 g) vs. 53.8 g (IQR 37.8-64.5 g), respectively, P = 0.49]. Significant difference in gray zone mass assessed with the use of two techniques was demonstrated (19.1 +/- 7.3 g vs. 50.8 +/- 47.8 g; P = 0.003). There was a strong correlation between total LGE and gray zone mass (r = 0.789, P = 0.0001 for first method and r = 0.951, P < 0.0001 for the second one, respectively). However, significant variability of gray zone mass (and extent expressed as % of left ventricular mass) in patients with similar LGE size/extent was observed. Moreover, LGE mass varied greatly in patients with similar gray zone size. Neither left ventricular mass, nor with maximal wall thickness correlated with extent of gray zone assessed with both methods. The studied techniques provided similar results with regard to total LGE but significant differences were observed in gray zone mass. Two patients may have similar extent (or absolute mass) of LGE, but strikingly discrepant gray zone size.