Researchers in Norway have demonstrated that patients who carry a HCM gene show reduced cardiac volume when compared to healthy individuals.  Patients with overt HCM show even further reduction to their cardiac volume than those who merely carry the gene.

Although the gene positive individuals lacked the characteristic left ventricular wall thickening of HCM, diastolic and systolic volumes were reduced when compared to healthy individuals. Hence, the researchers concluded that a person who is gene positive for the disease may show reduced volume before developing hypertrophy.

The study included 180 patients with left ventricular hypertrophy, 100 patients who carried the HCM gene but did not show signs of left ventricular hypertrophy, and 80 healthy individuals.

The researchers theorize that early changes in HCM result from the gradual stiffening of the left ventricle, which contributes to filling changes before anatomical thickening is apparent. These changes will likely worsen as the disease progresses.

The researchers suggest future long term studies of gene positive individuals with small cardiac volume who show signs of diastolic and systolic dysfunction. These patients, they suggest, are the most likely to go on to develop HCM.