Secondary unstable angina

ECG 1: Atrial fibrillation; repolarization disorders with significant depression in V3-V4, negative or flat T-waves in leads I, aVL, II, III, aVF, V4-V6; absence of elevation or of Q-waves;

Comments: This patient presented changes in the electrocardiogram in conjunction with a change in atrial fibrillation. Biological work-up did not show any increase in cardiac enzymes. Coronary angiography performed the following day did not find any significant stenosis or progression of the thromboembolic disease compared to the examination performed 2 years earlier.

This type of clinical picture is relatively frequent and corresponds to a secondary unstable angina, i.e. an extrinsic factor responsible, in a coronary patient, for an increase in oxygen requirements in the absence of significant coronary stenosis. Several mechanisms can be incriminated and occur as standalone or in combination: functional reduction in coronary flow (hypotension on a background of shock), reduction in myocardial oxygen transport (anemia, hypoxemia), increased cardiac work (fever, AF, hyperthyroidism). The electrocardiogram frequently reveals a ST-segment depression with shallow negative T-waves. These abnormalities most often disappear at the same time as the triggering factor.
In this patient, a slowing of the heart rate by beta-blocker treatment enabled normalizing the pattern of the electrocardiogram.

Take-home message: A passage in atrial fibrillation or an anemia in a stable coronary patient is often associated with the finding of a ST-segment depression which is normalized upon correction of the triggering factor.