An Unusual Cause of Tachycardia‐Induced Myopathy

Incessant Non‐Reentrant Supraventricular Tachycardia Interrupted By Apparent Simultaneous Wenckebach Sequences along Both Nodal Pathways

“…For such a mechanism to be possible, several electrophysiological conditions should be simultaneously met. First, the conduction time in each pathway should be long enough to exceed the refractory period of the lower common pathway and/or His bundle‐Purkinje tissue 1–4 . Second, retrograde conduction should be poor to absent in both the fast and slow pathways, 1–6 allowing successive uninterrupted anterograde conductions along both pathways and thus the perpetuation of the arrhythmia.…”

“…First, the conduction time in each pathway should be long enough to exceed the refractory period of the lower common pathway and/or His bundle‐Purkinje tissue 1–4 . Second, retrograde conduction should be poor to absent in both the fast and slow pathways, 1–6 allowing successive uninterrupted anterograde conductions along both pathways and thus the perpetuation of the arrhythmia. If double responses can occasionally induce isolated slow‐fast nodal echoes 1 or AV node reentrant tachycardia, 7 non‐reentrant supraventricular tachycardia usually occur in an incessant fashion and are only exceptionally associated with reentrant tachycardia 2,3,6,8 because of the second mandatory condition.…”

“…Second, retrograde conduction should be poor to absent in both the fast and slow pathways, 1–6 allowing successive uninterrupted anterograde conductions along both pathways and thus the perpetuation of the arrhythmia. If double responses can occasionally induce isolated slow‐fast nodal echoes 1 or AV node reentrant tachycardia, 7 non‐reentrant supraventricular tachycardia usually occur in an incessant fashion and are only exceptionally associated with reentrant tachycardia 2,3,6,8 because of the second mandatory condition. The only exceptions have been linked to the existence of more than two pathways, 3 or to the fact that block of retrograde conduction was not fixed 2,3 or resolved under isoproterenol 6,8 .…”

An Unusual Cause of Irregularly Irregular Supraventricular Tachycardia

“…This uncommon conduction pattern has been termed nonreentrant AV nodal tachycardia or two‐for‐one AV nodal response, and has previously been reported to be an ECG mimic of AF 2,3 . Because this nonreentrant tachycardia can be incessant, it can lead to a reversible tachycardia‐induced cardiomyopathy 4 …”

Incessant “ventricular tachycardia” in a patient with non-ischemic cardiomyopathy. What is the tachycardia mechanism?

“…It is both under-and misdiagnosed in clinical practice and can lead to apparent tachycardia due to 1:2 AV conduction. This may cause disabling symptoms and can potentially lead to reversible tachycardia induced cardiomyopathy [3,4]. Surface EKG may be confusing and can be mistaken for atrial tachycardia/premature beats, ventricular tachycardia, or more commonly atrial fibrillation.…”