Please visit Jody Chinitz' great site for more precise definitions. Their test results are more equivocal. Subsequent ultrasounds show these cats still with perfectly normal hearts at the times of their last screens. Another breeder reports that one of her females showed enlarged papillary muscles at one year. The cat was spayed, but one year, her echocardiogram showed a normal heart.
Hearts are dynamic organs, subject to change and stress.
Change can happen very quickly, both for the better and for the worse. Hypertrophic Cardiomyopathy is a puzzling, frightening and frustrating disease. Education and rigorous, annual testing are the only things we can do at this time to ensure that our cats and their kittens are as healthy and long lived as possible. Eliminating HCM from our Maine Coons is of utmost importance. We are so lucky to have Dr. Kittleson working with Maine Coon breeders.