Study discovers serious deficiencies in ’apparently normal’ heart valves

Mitral valve tissue undergoes dramatic changes during congestive heart failure

Surprising new findings in the Journal of the American College of Cardiology show that the basic biochemical composition of heart valves in patients with congestive heart failure are markedly different than those with healthy hearts, a finding that may explain the mixed success of surgery to repair valve dysfunction in these patients.

The valves of patients with congestive heart failure often fail to close properly, allowing blood to leak back through the valve when the heart contracts. The problem, known as mitral regurgitation, has typically been ascribed to enlargement of the heart and other pathological problems associated with heart disease, but the new study suggests that changes in the valves themselves may contribute to the problem. This work was hailed as a “paradigm shift” in an accompanying editorial in the same journal.

“The most common form of valve disease — a condition called myxomatous mitral valve disease – is marked by a severe thickening of the valve tissue that is very easy to spot, either in surgery or on an electrocardiogram,” said the study’s lead researcher K. Jane Grande-Allen, assistant professor of bioengineering at Rice. ” The changes we’ve documented are far more subtle. The valves look normal, both to the naked eye and on electrocardiogram, but at the cellular level, the tissue is quite different from that of healthy valves.”

Grande-Allen’s findings are based on a comparison of healthy heart valve tissue from cadavers with the mitral valve tissue from congestive heart failure patients who underwent heart transplantation. Heart valves are connective tissue, and like skin, tendons and other connective tissues, the strength of the tissue derives not from the cells they contain but rather from the extracellular matrix that the cells secrete.

Grande-Allen and her colleagues found that the mitral valves of patients with advanced heart disease contained far more cells and collagen, but were less hydrated than healthy tissue. “Our study shows that the mitral valve tissue in patients with congestive heart failure is significantly different from the tissue found in healthy valves,” said Grande-Allen, who is conducting a follow-up study of the differences in the biomechanical properties — like stiffness — of the two tissues. “Mitral regurgitation can seriously affect the health of heart failure patients. Even though the leaky mitral valve can be repaired, surgeons have reported that for many patients the mitral regurgitation returns. The changes that we found in the mitral valves could account for these mixed surgical outcomes.”

Grande-Allen’s co-authors include, Allen G. Borowski, Richard W. Troughton, Penny Houghtaling, Nicholas R. DiPaola, Christine S. Moravec, Ivan Vesely and Brian P. Griffin, all of The Cleveland Clinic’s Kaufman Center for Heart Failure. The research appeared in the Jan. 4 issue of the Journal of the American College of Cardiology.