Heart rate variability analysis in acute poisoning by cholinesterase inhibitors

Heart rate variability (HRV) has been asso-ciated with a variety of clinical situations. However, few studies have examined the association between HRV and acute poi-soning. Organophosphate (OP) and car-bamate inhibit esterase enzymes, particu-larly acetylcholinesterase, resulting in an accumulation of acetylcholine and thereby promoting excessive activation of corre-sponding receptors. Because diagnosis and treatment of OP and carbamate poisoning greatly depend on the severity of choliner-gic symptoms, and because HRV reflects autonomic status, some HRV parameters may be of value in diagnosing OP and car-bamate poisoning among patients visiting the emergency department.

Patients who visited the emergency de-partment of the study hospital between September 2008 and May 2010 with the chief complaint of acute poisoning or over-dose were included. Cases that involved ingestion of OP or carbamate insecticides were classified as poisoning by cholinest-erase inhibitors and compared with other cases of poisoning or overdose. The time-domain analysis included descriptive sta-tistics of R-R intervals and instantaneous heart rates. The frequency-domain analy-sis used fast Fourier transformation. A Poincaré plot, which is a scatterplot of R-R intervals against the preceding R-R inter-val, was used for the nonlinear analysis. Very-low-frequency (VLF) power and the ratio of low-frequency-to-high-frequency power (LF/HF) were the most effective pa-rameters for distinguishing cholinesterase inhibitor poisoning among cases of acute poisoning, with areas under the receiver-operating characteristic curve of 0.76 and 0.87, respectively. Cholinesterase inhibitor poisoning was a significant factor deter-mining VLF power and the LF/HF ratio after adjusting for possible confounding variables, including age over 40, gender, and tracheal intubation.

Frequency-domain parameters of HRV, such as VLF power and the LF/HF ratio, might be considered as potential diagnos-tic methods to distinguish cholinesterase inhibitor poisoning from other cases of in-toxication in the early stages of emergency care.

electrocardiography, organo-phosphates, carbamates, poisoning

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