As part of a research study, investigators measured blood troponin levels in over 7500 consecutive patients just before they had elective angioplasty and stenting for clinically stable coronary artery disease (CAD). To the investigators' surprise, over 6% of these apparently stable patients had elevated levels of troponin, indicating cardiac muscle damage. And in addition, those with elevated troponin levels had twice the risk of heart attack or death over the next year.

Troponin is an enzyme that is released into the bloodstream when cardiac muscle cells are dying. Elevated troponin levels usually mean that blood clots are forming in the coronary arteries at the site of a plaque. Blood clots that form and then dissolve quickly usually produce unstable angina, whereas blood clots that form and do not dissolve cause myocardial infarctions, or heart attacks.

The findings of this new study, reported in the journal Circulation this week, strongly suggest that some patients with apparently stable CAD actually are quite unstable. That is, they have "vulnerable plaques" which are generating transient blood clots that are causing heart cell damage. Furthermore, those who have these vulnerable plaques are far more likely to have heart attacks or to die than patients whose CAD is actually stable.

The next step will be to conduct larger studies to confirm that this finding is true. If so, researchers will then look for methods to screen more routinely for patients who apparently have stable CAD but who actually have a much more dangerous condition. Read more about unstable CAD here.

_Sources:

Jeremias A, Kleiman NS, Nassif D. Prevalence and prognostic significance of preprocedural cardiac troponin elevation among patients with stable coronary artery disease undergoing percutaneous coronary intervention. Results from the evaluation of drug eluting stents and ischemic events registry. Circulation 2008; DOI: 10.1161/CIRCULATIONAHA.107.752428.

SOS enrolled more than 900 patients with mutivessel coronary artery disease, and randomized them to have either coronary artery bypass grafting (CABG) or stents. In this latest update of the results after six years of follow-up, CABG patients had a persistently better survival than stent patients (93.2% in CABG patients vs. 89.1% in stent patients).

Critics of the SoS trial point out many reasons cardiologists and their patients should not consider these results to be definitive, and they ask us to wait for several years, for more studies to be completed.

Waiting for several years for more data to become available is a nice idea, but it might not be an option for those who need to make decisions about their therapy today. For people in this position, here are some thoughts about how the SoS data might figure into your decision.