A 74 year old man with an old anterior wall infarction and 3-vessel coronary artery disease underwent an exercise test for evaluation of his general condition. A baseline electrocardiogram shows sinus rhythm with normal conduction intervals and an old anterior wall myocardial infarction (Fig. 1, rest). Patient developed shortness of the breath one minute before the end of the test. His ECG reveals an isorhythmic dissociation characterized by independent atrial and ventricular activation (Fig. 1, exercise); sinus and an accelerated junctional rhythm of approximately 100 bpm and complete AV-block. The rate of these two rhythms is nearly identical giving an illusion of a normal atrioventricular conduction sequence. The P wave moves closer to QRS complex and causes a relationship which is often called flirtatious. Occasionally, the P wave will move into, and be buried within the QRS complex. The junctional rhythm may become frankly faster and overtake the sinus node resulting in retrograde conduction to the atria, shown in Fig. 1, peak exercise when peak exercise was reached at the second minute of Bruce 2 protocol.
展开▼
