ECG Review: The Same Tachycardia?
By Ken Grauer, MD, Professor, Assistant Director, Family Practice Residency Program, University of Florida, Associate Editor, Internal Medicine Alert.
Figure. 12-lead ECG recorded from a 69-year-old woman with a history of prior inferior infarcion and known RBBB.
Clinical Scenario: The 12-lead ECG in the Figure was obtained from a 69-year-old woman with a history of a previous large myocardial infarction. She was aware of an "extra beating" of her heart, but was otherwise asymptomatic at the time this tracing was recorded. How would you interpret this tracing in view of this presentation, her prior history, and the knowledge that the patient was known to have complete RBBB (right bundle branch block) on prior ECG?
Interpretation/Answer: The 12-lead ECG in the Figure shows a regular WCT (wide-complex tachycardia) at a rate of about 160/minute. One might certainly interpret the ECG as showing SVT (supraventricular tachycardia) with QRS widening consistent with previous myocardial infarction (large inferior and lateral Q waves) and complete RBBB (rSR’ in lead V1, wide S waves in leads I and V6). However, despite her minimally symptomatic state, we are much more suspicious of VT (ventricular tachycardia) as the cause of her WCT for the following reasons:
i) Regardless of a patient’s level of consciousness or lack of symptoms, the overwhelming majority of new-onset WCT rhythms in which normal atrial activity is absent are VT.
ii) QRS morphology in the lateral precordial leads during the tachycardia strongly favors VT as the diagnosis. It is highly unusual for supraventricular rhythms to be all negative in these leads. Careful lead-to-lead comparison with this patient’s previous ECG showed a definite difference from these negative complexes in leads V4 through V6, strongly supporting our contention that VT must be assumed until proven otherwise.
The 12-lead ECG in the Figure was obtained from a 69-year-old woman with a history of a previous large myocardial infarction. She was aware of an extra beating of her heart, but was otherwise asymptomatic at the time this tracing was recorded. How would you interpret this tracing in view of this presentation, her prior history, and the knowledge that the patient was known to have complete right bundle branch block on prior ECG?
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