The authors describe the case of a 49-year-old man who experienced an episode of palpitations and dizziness.The results of 24-hour Holter monitoring demonstrated an episode of wide QRS complex regular tachycardia. During the electrophysiological study, a wide QRS complex tachycardia with negative precordial concordance was induced. A diagnosis of orthodromic atrioventricular re-entrant tachycardia involving a left lateral accessory pathway with left bundle branch aberration was made. This case represents a rare exception to the rule that negative precordial QRS concordance is diagnostic of ventricular tachycardia.
A 49-year-old man was admitted to the cardiology department because of an episode of palpitations, dizziness, and epigastric discomfort. He had no history of heart disease, but he reported episodes of regular palpitations during the past year. His standard 12-lead electrocardiogram (ECG) on admission was unremarkable. Physical examination and routine laboratory examinations, including blood and urine tests, chest X-ray film, and transthoracic echocardiography, were normal. The results of 24-hour Holter monitoring revealed a short-lasting episode of regular tachycardia characterized by a wide QRS complex of 140ms and a cycle length of 300ms.
An electrophysiological study was performed. During pacing at the right ventricular apex with a basic cycle length of 500ms, two extra stimuli given at 305 and 210ms induced a wide QRS complex tachycardia with negative precordial concordance and a cycle length of 313ms (see Figure 1, panel A). Endocardial recordings during the tachycardia showed a 1:1 relationship between ventricular and atrial activity. An eccentric atrial activation sequence was demonstrated, with the earliest atrial activation recorded by the distal coronary sinus catheter, suggesting retrograde atrial activation through a left-sided accessory pathway (see Figure 1, panel B). The HV interval was 81ms and the VA interval was 165ms. A diagnosis of orthodromic atrioventricular re-entrant tachycardia involving a left lateral accessory pathway with left bundle branch aberration was made. Radiofrequency ablation of the accessory pathway was successfully accomplished.
Wide QRS complex tachycardia may result from supraventricular tachycardia with bundle branch block (pre-existing or tachycardia-related), supraventricular tachycardia with atrioventricular conduction over an accessory pathway, or ventricular tachycardia.
Evaluation with a 12-lead ECG can support the differential diagnosis of the underlying mechanism, and several ECG criteria have been proposed. Concordance of the predominant direction of wide precordial QRS complexes is a useful ECG clue in differentiating between a ventricular and a supraventricular tachycardia. When all of the ventricular complexes from leads V1 to V6 are positive (positive concordance), the diagnosis is most likely left posterior ventricular tachycardia or, rarely, supraventricular tachycardia with atrioventricular conduction over a left posterior accessory pathway.
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