We utilized previously described methods of BSPM data acquisition. Briefly, this included 117 torso and four limb electrodes of silver-silver chloride. The superior limb electrodes were placed over the acromio-clavicular joints and the inferior limb electrodes over the superior iliac spines; these placements were selected to reduce exercise motion artifact. All 120 leads were sampled simultaneously for 15-s epochs at 500 samples per second per channel and the data stored in digital form on magnetic tape using a PDP 11/24 computer. Wilsons central terminal was used as reference and each channel amplifier had a gain of 2,000. With 12 bit samples resolution was 2.5 p,V for the least significant bit in the dynamic range ±5 mV Maps were recorded at: pre-exercise rest; immediately upon cessation of exercise (which was utilized as the peak exercise-equivalent to minimize skeletal muscle motion artifact); and at 1 and 5 min post-exercise recovery. The peak exercise heart rate was defined as the average rate over 15 s of recorded data during the last minute of exercise.
The BSPM data were analyzed and displayed using a VAX 11/780 computer. The 15-s recordings at each lead were averaged using previously tested algorithms with the PR segment as baseline. In addition, editing of each analog-form averaged lead was performed; leads judged unacceptable because of noise or baseline drift were deleted and replaced by interpolated data from surrounding leads. flovent inhaler
Using superimposed Frank X, Y and Z leads to determine the time instants of QRS offset and peak of the T wave, the time integral of, or area under, the ST segment curve was computed at each electrode site. For this exercise study, the duration of the ST segment was defined as one half the time from QRS offset to the peak of the T wave (Fig l). The ST segment time integrals were expressed in mV*s.
Figure 1. Signal-averaged 12-lead electrocardiograms of a CAD patient (patient 5; Tables 1 and 2) at rest, at immediate cessation of exercise and at 5 min recovery. The shaded areas in each panel represent the ST integral, the area under the ST curve.
Category: Coronary Artery Disease
Tags: Angina, Coronary Artery Disease, Ischemia, Myocardial ischemia