What is Intermittent ST Depression ?
Ans.
Several patients progress from variable ST-segment depression, often associated with respiration, to the classic ST-segment changes typical of ischaemia. The mechanism of this condition seems to be related to the fact that inspiration and expiration are associated with different rates of left ventricular filling. If the compliance of the left ventricle is slightly decreased the increased rates of the filling may produce an elevation in the end diastolic pressure and therefore, ST-segment depression for only a few beats. This is almost always seen near maximum stress levels, when compliance of the ventricle would be expected to be decreased the most and when the abdominal pump would be returning the blood to the heart at the greatest velocity.