For most people, heart failure (also known as congestive heart failure or CHF), is a chronic condition in which the heart is not able to efficiently pump blood throughout the body.  This often results in the gradual accumulation of fluid (edema) in various parts of the body over time.  However, heart failure may be acute and potentially life-threatening when the failure of the heart to effectively pump blood results in a rapid accumulation of fluid in the lungs leading to difficulty breathing (dyspnea) and respiratory distress.

A study of patients experiencing acute heart failure, published in the May 15, 2008 issue of the New England Journal of Medicine, found that the level of cardiac troponin (an indicator of damage to heart muscle) in the blood identified patients at increased risk of dying during hospitalization for this condition. The study also found that patients with a positive troponin test were more likely to require intensive care and a longer hospital stay.

Troponin testing is primarily used as a tool in diagnosing heart attacks - where damage to the heart is caused by blocked blood flow to the heart.  Its role in providing information in cases of congestive heart failure is less clear.  This large, observational study shows that the troponin test may have a new use in predicting how well a patient with acute heart failure will do while hospitalized. The researchers suggest adding troponin to the initial diagnostic tests and incorporating the data into an early assessment of risk. Troponin test results “should be factored into decisions that are made with respect to triage and management,” they wrote. “Although we did not study differential management, in our opinion, patients with an increased risk of death should undergo more intensive cardiovascular monitoring; they may require admission to a critical care unit or cardiac telemetry,” they explained.

Study details
To reach its conclusions, the team of investigators led by researchers from Cleveland Clinic, analyzed data from the Acute Decompensated Heart Failure National Registry (ADHERE). They drew from the records of patients hospitalized at many different institutions.  They chose patients with a diagnosis of ADHF (acute decompensated heart failure) between October 2001 and January 2004 who had either troponin I or troponin T measured within 24 hours of their admission to the hospital. The researchers defined an elevated level as a cardiac troponin I level of 1.0 μg per liter or higher or a cardiac troponin T level of 0.1 μg per liter or higher. The researchers found 67,924 cases to study and 4240 cases (6.2 percent of the total) showing elevated troponin.

Study Findings
Patients with elevated troponin had a lower systolic blood pressure and a lower ejection fraction than the others at the time they were admitted. (Lower systolic blood pressure has been associated with a poorer chance of survival, and the ejection fraction, the percentage of blood pumped from the left ventricle during each heartbeat, also is used to help determine severity.) Eight percent of patients with elevated troponin died in the hospital compared to 2.7 percent of patients with low or normal levels of troponin.  (Data on deaths occurring after discharge from the hospital were not available from the registry.) Those testing positive for elevated troponin also were found to spend more time in the intensive care unit and have more cardiac procedures and longer hospitalizations than the patients with low or normal troponin.  The troponin test’s association with higher in-hospital mortality and other outcomes was independent of other well-validated risk factors and prognostic variables, such as medication use or the cause of the heart failure, the study found.

Limitations
Laboratories use various methods to measure troponin, and each type of test has a unique cut-off point for a positive result. A significant limitation of this study was that it included data on patients who had different types of troponin tests but did not take into account the different established cut-off points for positive results.  Instead, one uniform cut-off point was established regardless of method.  This could have affected interpretation of those results close to the cut-off point.

A Way to Stratify Risk, Plan Treatment
The authors noted that their findings add to existing risk-stratification data and urged future research to “examine therapies to mitigate these outcomes.” In a summary and comment in the May 14, 2008, issue of Journal Watch Cardiology, Harlan M. Krumholz, MD, SM, noted that the measurement “appears to have been adopted into current practice in advance of evidence about how we should use it.” MedPage Today, a physician news web site, advised doctors to tell interested patients that “the authors of this study suggested that the measurement of troponin levels could provide useful prognostic information.” Putting this information to use will await additional research in which treatments based upon troponin levels are studied in this patient population.

Sources
Heart failure (in-depth patient report). Reviewed 11 Apr 2007. Detroit: Henry Ford Hospital. Available on the Internet at http://www.henryfordhealth.org. Accessed 5 Jun 2008.

Krumholz, HM. 14 May 2008. Troponin levels and prognosis in patients with acute heart failure (summary). Journal Watch Cardiology.

Neale, T. 14 May 2008. Elevated troponin may predict short-term outcome in acute heart failure. MedPage Today. Available online at http://www.medpagetoday.com/Cardiology/CHF/9450. Accessed 27 May 2008.

Peacock WF IV,  De Marco T, Fonarow GC,  et al. 15 May 2008. Cardiac troponin and outcome in acute heart failure. New England Journal of Medicine 2008;358:2117-26.

(January 31, 2008 updated) UpToDate for Patients. Treatment of Acute decompensated Heart Failure.  Available online at http://www.uptodate.com/patients/content/topic.do?topicKey=hrt_fail/11440. Accessed July 2008.

Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds. (2005) Harrison's Principles of Internal Medicine, 16th Edition, McGraw Hill. Pg. 1369.