12-LEAD ECG VENTRICULAR TACHYCARDIA MORPHOLOGY IN PATIENTS WITH REMOTE INFERIOR MYOCARDIAL INFARCTION
Introduction:The surface 12-lead electrocardiograph (ECG) has proven to be a robust and reproducible initial mapping tool that can provide useful information in localizing the origin of reentrant ischemicventricular tachycardia (VT). Furthermore, ECG criteria have been proposed to distinguish VT from supraventricular tachycardia with aberrant interventricular conduction.
The aim of this study was to describe the QRS morphology of VT in patients with old inferior myocardial infarction.
Methods: The QRS morphology of 18 VTs was analyzed. All VTs were ischemic, in patients with remote inferior myocardial infarction. In each patient sustained ventricular tachycardia had occurred and required pharmacological therapy or DC cardioversion for termination.
Results: Remote myocardial infarction was present in all 18 cases and 2 had inferior wall left ventricular aneurysm at echocardiography.Ten VTs had a right bundle branch block (RBBB) morphology and 8 a left bundle branch block (LBBB) morphology. All but one VT with a RBBB pattern had superior axis and all but one VT with a LBBB pattern had also superior axis. Positive QRS concordance was present in 3 VTs and negative concordance in 1 VT. QRS configuration in V1 was monophasic R (9/10) or Rs (1/10) in case of RBBB-pattern; and rs (3/8), rS(2/8) or QS (3/8) in case of LBBB-pattern. Lead V6 in RBBB-type showed R/S<1 in 4 cases (rS pattern), R/S>1 in 2 cases (Rs pattern), QS (3/10) or R pattern. Lead V6 in LBBB-type showed R(3/8), qr (2/8), RS, QS, or rS pattern.
Conclusions: Ventricular activation arising from specific regions of an infarcted inferior wall results in differentQRS morphologies. These QRS morphologies during VT generally does not resemble true LBB or RBBB and can be use to locate the exit point of the reentry circuit. These QRS features have also implications in the differential diagnosis of VT and supraventricular tachycardia with aberrant conduction.