While recording ECG of dogs directly by applying leads and keeping them restrained, I would like to know if there is any requirement of the minimum duration/cardiac cycles/beats for which the ECG needs to be recorded? It would be great, if anybody can share relevant references.
Interesting question. The longer the better. It must cover a complete breathing cycle. After placement of the electrodes for each dog, the time for the occurrence of the respiratory arrhythmia is different. The problem is that in some dogs it is poorly expressed. In addition, respiratory arrhythmia disappear in heart failure. This makes this landmark not very reliable. I will follow your question.
As a former safety pharmacologist in the drug development industry, the correct answer is a minimum of 24 hrs continuous radiotelemetry to determine potential ECG effects. I have seen effects manifest from within minutes of a dose to one situation where TdP didnt happen until 22 hrs post dose (ECG was relatively normal for 20 hrs). While I have done many tox studies using external leads as you describe and have tried to predict at what point to measure them (Cmax/Tmax, 1/2 Tmax, 2x Tmax) it is almost a useless exercise to measure external lead ECGs. Since you only get a dog to sit in restraint for a few minutes to get this type of data, unless you train them for long term sling restraint but still difficult to get good data and then you only get 2-4 hrs postdose. For a simple external lead collection, typical duration is 30-60 sec of clean recording (that covers ~ 10 resp cycles in a calm dog). If you're lucky you might see an effect but the odds of capturing the signal at the right time postdose and collecting without the dog's sympathetic drive masking a signal (depends on the mechanistic change the drug is inducing) are quite small.
Hi Michael, thanks for the detailed answer, completely agree with your reply. My question came because of the reason that I was looking for an exact reference which mentions something on the duration of recording required. What I found, out was that literature mentions no standard duration, and people do it for durations ranging from 10 to may be 60 sec.
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