Abstract
Exercise induced ST segment depression in ischemic heart disease has been accepted as a sign of myocardial ischemia. Although similar electrocardiographic ischemic changes are observed in some of the exercising patients with rheumatic valvular disease, its clinical importance has not been clearly identified.
The purpose of this study is to clarify the significance of exercise induced ST segment depression in patients with rheumatic valvular disease by means of multi-stage symptom-limiting exercise with upright ergometer, while monitoring hemodynamics, oxygen consumption and electrocardiogram.
The patients included in this study consisted of 27 males and females, all of whom had undergone various rheumatic valvular surgery. All patients were on digitalis compounds but none of them were on antiarrythmics nor β-blockers.
All patients were divided into two groups according to the degree of exercise induced ST segment changes; Group A: ST depression≥1mm, Group B: ST depression<1mm.
Results: i) Group A showed high mean pulmonary capillary wedge pressures at rest and they were further elevated with exercise. At the maximal exercise level, mean pulmonary capillary wedge pressures in group A were significantly higher than those in group B.
ii) Group A showed large stroke indices at rest but at the maximal exercise level they were smaller than those in group B.
iii) Different response to exercise was demonstrated on the left ventricular function curve, drawn from stroke indices and mean pulmonary capillary wedge pressures during exercise.
Group A moved to right side and shifted downward during exercise, while group B moved to right side and shifted upward.
Exercise induced ST segment depression in group A was probably indicating poor cardiac reserve capacity resulting from diminished augumentation of stroke volume with resultant compensatory increase in heart rate which caused shortening of diastole, and subsequently leading to the relative subendocardial ischemia due to diminished oxygen supply.
It was suggested that exercise induced ST segment depression (ST≥1mm) regardless of digitalis intake in post-operative rheumatic valvular patients should be considered as an manifestation of cardiac pump dysfunction and should be interpreted as over-loading when cardiac rehabilitation is carried out.
