Conditions that result in a heart murmur — aortic stenosis, aortic regurgitation, mitral regurgitation and hypertrophic cardiomyopathy are the most frequent and important — are often associated with turbulence in the bloodstream. When examined by various imaging techniques, this turbulence provides a semi-quantitative idea of the severity of the condition.
The research of Joseph L. Blackshear, M.D., involves the study of von Willebrand factor, a clotting protein that is progressively defunctionalized by turbulent blood flow.
In an ongoing study, Dr. Blackshear's research group has evaluated 67 patients with aortic stenosis, as well as 30 patients each with mitral regurgitation and hypertrophic cardiomyopathy. They've found a close correlation between the severity of the turbulence caused by the disease and the disruption of von Willebrand factor function.
However, von Willebrand factor testing was designed to distinguish a congenital condition from the normal state, not to identify progressive abnormalities of heart conditions. Therefore, new tests with performance characteristics sensitive to heart abnormalities are required, and Dr. Blackshear and his colleagues are investigating new approaches to testing.
The strength of the association of aortic stenosis mean gradient with von Willebrand factor abnormalities was published in three abstracts in 2011 (one to the American Heart Association and two to the American Society of Hematology), and a manuscript describing the findings has been submitted for publication.
In March 2011, the first paper describing the reversibility of clinical bleeding by surgery for hypertrophic cardiomyopathy was published in Mayo Clinic Proceedings, along with an accompanying editorial describing the importance of this type of investigation.
Significance to patient care
Classification of valvular heart disease may overlap moderate or severe designation in up to 40 percent of patients. Additionally, symptoms of valvular disease — shortness of breath, loss of consciousness and chest discomfort — may be present from the valvular condition, another condition or may be obscure if the patient is inactive.
Similar difficulties are present in defining symptoms in hypertrophic cardiomyopathy. A blood test that is a reliable measure of severity could improve surgical decision making and medical approaches to the prevention of disease progression.