Negative concordant T waves during paced ventricular rhythm: An honest enemy is better than a false friend.

The ECG diagnosis of myocardial infarction and ischemia in pacemaker patients is often challenging. The three criteria, proposed by Sgarbossa et al. in 1996, useful to suspect myocardial ischaemia in patient with left bundle branch block were demonstrated to be valid also in pacemaker patients. In the last years, concordant negative T waves in patients with ventricular paced rhythm were linked to various expressions of acute myocardial injury. If available, comparison with previous ECG is crucial. Partial persistence of cardiac memory during fusion beats created an anomalous concordance between negative T waves and QRS axis and could induce erroneous suspicions. AV delay modification could help to unmask this situation.