Production of arrhythmias by elevated carboxyhemoglobin in patients with coronary artery disease

Disease of the coronary arteries, the major blood vessels supplying the heart, frequently results in sudden death. Ventricular arrhythmias, or abnormal heart rhythms arising in the ventricles, are a common cause of sudden death, and may be the only symptom of coronary artery disease. Exposure to carbon monoxide, a common environmental pollutant, may cause ventricular arrhythmias and, thereby, contribute to the occurrence of sudden death in patients with coronary artery disease. Exposure to carbon monoxide leads to elevated blood levels of carboxyhemoglobin, the product of the interaction between carbon monoxide and hemoglobin, the oxygen-carrying pigment of the blood. Whether or not carbon monoxide-induced elevations in carboxyhemoglobin cause ventricular arrhythmias was assessed in 41 patients with coronary artery disease. Patients were exposed to room air, and to carbon monoxide levels which produced four and six percent carboxyhemoglobin. They were then required to perform exercise on a bicycle. The heart ventricles were X-rayed during exercise, and the electrical activity of the heart was recorded throughout the procedure to detect the occurrence of ventricular arrhythmias. During the exercise period, the frequency of single or multiple ventricular arrhythmias was greater after the patients were exposed to carbon monoxide producing six percent carboxyhemoglobin. This result did not occur at levels of four percent carboxyhemoglobin. The results also revealed that the patients who developed more frequent ventricular arrhythmias were older. In addition, patients who developed multiple or complex ventricular arrhythmias exercised longer and under greater workloads. These findings demonstrate that, during exercise, the number and complexity of ventricular arrhythmias increase in patients with coronary artery disease who achieve six percent carboxyhemoglobin after carbon monoxide exposure. (Consumer Summary produced by Reliance Medical Information, Inc.)