Canadian Neighbor Pharmacy: Discussion of Exercise-induced ST-segment Depression and Elevation In the Same Patient
Previous reports of ST-segment elevation and depression in the same patient have included ST depression during exercise followed by ST elevation in the post-exercise period, ST elevation during spontaneous episodes of chest pain at rest with ST depression during exercise, and variable ST-segment elevation and depression during arm exercise with ST-segment depression during treadmill exercise. We are aware of no other report of ST-segment elevation and depression in the same patient under similar treadmill testing conditions.
Several mechanisms for ST-segment elevation during exercise have been proposed. It is not uncommon in patients with previous myocardial infarction. DeFeyter et al reported exercise-induced ST elevation in 52 percent of such patients, which they attributed to mechanical dysfunction of the left ventricle in the region of the previous infarct. ST-segment elevation with exercise has also been attributed to severe transmural ischemia due to significant coronary artery disease. Dunn et al performed cardiac catheterization in 46 patients with exercise-induced ST elevation in leads Vx and/ or aVL without anterior Q waves and found significant left anterior descending artery disease in 38 (83 percent). Exercise-induced ST-segment elevation due to severe transmural ischemia has been ascribed to predominant coronary spasm. Chaitman et al cite an incidence of ST elevation during exercise in patients with variant angina of 10-30 percent. It has also been suggested that transient thrombosis in a patient with coronary artery disease might cause transient ST elevation. However, in our patient, the clinical history, angiographic findings and variable ST segment response cannot be accounted for by any one of these explanations alone.
Although myocardial ischemia is generally felt to result from fixed supply with increased demand in classic Heber-dens angina and a dynamic decrease in supply with and without increased demand in Prinzmetal’s angina, there has recently been an interest in mixed angina in which superimposed fixed and dynamic obstruction play a role. It is possible that the ST-segment elevation noted during this patients repeat exercise test represented more severe ischemia due to spasm superimposed on a significant area of vessel obstruction. Although beta blockers have well established benefits in classic angina pectoris, it has been suggested that they may exacerbate angina due to spasm by unmasking unopposed alpha-adrenergic vasoconstriction. It is conceivable that the institution of beta blocker therapy may have precipitated superimposed spasm resulting in ST-segment elevation during exercise. Do you like to become the expert in medicine? You should check out Canadian Neighbor Pharmacy website to find necessary for reading.
Exercise-induced ST-segment elevation is an uncommon but well described response during exercise testing. This patient with significant coronary artery disease without previous infarction exhibited ST-segment depression and elevation under similar testing conditions which was not seen after coronary artery bypass surgery. Of the currently described explanations for exercise-induced ST-segment elevation, this presentation seems most consistent with mixed angina due to spasm superimposed on significant obstructive disease, perhaps precipitated by initiation of beta blocker therapy.