Heart injury due to carbon monoxide poisoning increases long-term risk of death

Of patients who were hospitalized and treated for moderate to severe carbon monoxide poisoning, those who sustained heart muscle injury due to their exposure had an increased risk of death during a mid-point follow-up period of 7.6 years compared to those without injury to the heart, according to an article in the January 25 issue of JAMA.

Despite a decline in the annual death rate from carbon monoxide (CO) poisoning, CO remains the most common type of accidental poisoning in the United Sates, contributing to 40,000 emergency department visits each year, according to background information. The Centers for Disease Control and Prevention reported that from 1968 through 1998 CO poisoning contributed to an average of 1,091 unintentional deaths and 2,385 suicidal deaths in the U.S. annually. Symptoms of CO poisoning include weakness, nausea, dizziness, lethargy, confusion and headache. In addition to neurological effects, heart damage has also often been reported in CO poisoning cases.

Christopher R. Henry, B.S., of the Minneapolis Heart Institute Foundation, and colleagues studied 230 patients treated for moderate to severe CO poisoning to evaluate the association between the patients' heart damage following CO poisoning and long-term risk of death. Patients admitted to the Hennepin County Medical Center between January 1, 1994, and January 1, 2002, were included in the study, with follow-up conducted through November 11, 2005. Heart muscle damage was characterized by elevated levels of cardiac troponin I (type of protein) or creatine kinase-MB (type of enzyme), and/or changes in diagnostic electrocardiogram (ECG).

Heart muscle injury occurred in 85 (37 percent) of the 230 patients with CO poisoning. At a mid-point follow-up of 7.6 years (ranging up to 11.8 years), 54 deaths had occurred (24 percent), with 12 (five percent) of those deaths taking place in the hospital. Of the 85 patients with heart damage, 32 (38 percent) died during follow-up compared with 22 (15 percent) of 145 patients without damage to the heart. Of those patients with a heart injury who died, 44 percent (14) died of presumed cardiovascular causes (i.e., cardiac arrest, heart attack).

"Patients with suspected exposure to CO should be screened for myocardial injury, and further cardiovascular risk stratification should be considered in all patients with confirmed myocardial injury," the researchers report. "Our data indicate these patients have poor long-term outcome, a topic that deserves further study."

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(JAMA. 2006; 295: 398 – 402. Available pre-embargo to media at www.jamamedia.org.)

Editor's Note: This study was supported by an unrestricted educational grant from the Minneapolis Heart Institute Foundation.


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