The assessment of QT intervals in acute carbon monoxide poisoning

Carbon monoxide (CO) poisoning is known to cause myocardial toxicity and life threatening arrhythmias. QT interval measured from electrocardiogram is an indirect measure of the heterogeneity of ventricular repolarization, which may contribute to ventricular arrhythmias. The purpose of the study was to investigate whether the carboxyhemoglobin (COHb) level may be related to the changes of QT, corrected QT (QTc), QT dispersion (QTd), corrected Qtd (QTdc) and cardiac enzymes during carbon monoxide poisoning.

We conducted an observational study; 104 patients who had been diagnosed with CO intoxication were included in the study. Measurement of QT, QTc, QTd and QTdc intervals were performed form electrocardiogram on admission, 24 and 48 hours after admission. Cardiac enzymes were measured at each time-point. The myocardial perfusion scan was determined in all patients 1 week after admission.

The QT interval level in 24 h was significantly higher than admission level (p<0.001), additionally QTc interval levels in 24 h and 48 h were significantly lower than admission levels (p<0.001 and p<0.001, respectively). Carboxyhemoglobin level only significantly correlated with QT intervals (r=-0.288 ; p=0.019), troponin T (r=-0.297; p=0.007), and creatine kinase MB levels (r=0.262; p=0.020). As a result of ROC analysis the QT interval level was significantly powerful parameter to predict COHb (p=0.022).

Our data indicate COHb level correlated with QT intervals and cardiac enzymes. Clinicians should possibly avoid QT prolonging drugs and carefully monitor the QT, QTc, QTdc intervals in patients at high risk of cardiac disability due to high levels of COHb after CO poisoning.