I had to have a 7 day ECG recently ( following 2 fume events within 3 1/2 months) so I looked up everything I could on the internet and I came across a medical site that said exposure to organophosphates causes abnormalities in ECG readings. It said to look for " prolonged QTc interval, elevated ST segments and inverted T waves."
It was an American health site but can't remember exactly where I found it.... will try and find it again and let you know.