Stunning research pinpoints a cause of sudden heart failure
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* Donalee Moulton

Troponin I (TnI), a small protein that helps the heart muscle to contract, has been found to trigger cardiac stunning, a form of heart failure that occurs after patients undergo open-heart surgery or are placed on a heart-lung machine (*Science* 2000;287:488-91). This study marks the first time that scientists have shown that a problem at molecular level can lead to any type of heart failure. FIGURE

![Figure1](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/162/8/1197.2/F1.medium.gif)

[Figure1](http://www.cmaj.ca/content/162/8/1197.2/F1)

Figure. 

"What is so remarkable about this study is that it shows this protein - and this protein alone - if it is 'clipped' is sufficient to cause stunning," says coauthor Dr. Jennifer Van Eyk, an assistant professor of physiology at Queen's University, Kingston. "We didn't know that before."

Earlier research had revealed that patients with weakened hearts had a shorter form of TnI than normal. To understand the connection between the shorter, or damaged, TnI and cardiac stunning, researchers in Canada and the US cloned the abnormal genes associated with the protein and injected them into mice. Approximately 20% of these mice then went on to develop the shortened form of TnI. They also developed enlarged hearts, a classic symptom of a heart muscle that has been weakened.

"What we've done is produce, artificially, what normally can happen in the heart muscle when the blood supply gets interrupted," notes Dr. Anne Murphy, a cardiologist at the Johns Hopkins Children's Center and team leader of the research project. "We believe this may have importance for garden variety heart failure. [Patients] may have some of this protein broken down. We don't know that for sure yet, but there are good reasons to suggest this possibility," she adds.