For the measurement of HRV, a three electrode electrocardiogram
(ECG) will be obtained using the Flexcomp
Infinity (Thought Technology Ltd, model SA7550, Montreal
West, Quebec, Canada). ECG will be analyzed to derive HRV
measures. The two active ECG electrodes will be placed
level in the fourth intercostal space, approximately 2 cm
lateral to the sternum. The reference electrode will be
placed on the left shoulder [34]. A three lead ECG is sufficient
to obtain the R-R measures required for HRV analysis
[35].