Letter by Jin-shan and Xue-bin Regarding Article, “Tachycardia-Induced Cardiomyopathy in a 43-Year-Old Man”
To the Editor:
We read with great interest the wonderful case presented by Zhao et al1 about dual atrioventricular nodal nonreentrant tachycardia. However, we have several questions. We notice that, aside from the abnormal rhythm, the QRS morphologies in precordial leads are also distorted. The slow and fast pathways conduct the impulse to the ventricle separately, generating 2 different QRS: the former is relatively narrow, the latter wide. However, they are rS or QS in V1 and V2, monomorphic Rs in V5 and V6. This finding indicates a left bundle branch block. Because the left bundle branch refractory period is shorter than the right bundle branch refractory period, it is easier to coincide with the right bundle branch refractory period. This patient’s QRS conducted by the slow pathway are all left bundle branch block morphology instead of right bundle branch block, so maybe something is wrong with the left bundle branch. This theory is also proved by the morphology of the QRS conducted by the fast pathway, which are narrow, but present rS in V1 and V2, Rs in V5 and V6. Not all supravenrticular tachycardias cause dilated cardiomyopathy. What is special for this patient? What is the burden of the arrhythmia? Is the left bundle branch block playing a role in this process? Will this patient progress to complete left bundle branch block in the future? I hope long-term follow-up for this patient can answer these questions.
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- © 2017 American Heart Association, Inc.