By Ken Grauer, MD
Professor Emeritus, Family Medicine, College of Medicine, University of Florida.
Dr. Grauer is the sole proprietor of KG-EKG Press, and publisher of an ECG pocket brain book.
The ECG in the figure below was obtained from a 55-year-old man who presented for emergency care with palpitations and fatigue. His blood pressure was 80/50 mmHg at the time this tracing was recorded. Is this ventricular tachycardia (VT)?
The rhythm is a regular wide complex tachycardia (WCT) at 180-190 beats per minute without a clear sign of atrial activity. Although QRS appearance resembles right bundle branch block (RBBB) with left posterior hemiblock (LPHB), QRS morphology is not completely typical for this conduction defect because:
- instead of a discrete rsR’ pattern in lead V1, there is a double notch to the initial deflection in this lead, and a clear s wave that descends below the baseline is not visible;
- the initial slender positive deflection (r wave) in lead I, followed by a predominant deep negative deflection, is consistent with LPHB, but lack of a predominant R wave in lead II is not.
As emphasized in the “ECG Review” that appeared in the April 15 issue of Internal Medicine Alert, statistically, > 80-90% of all regular WCT rhythms that lack sinus P waves will turn out to be VT. Thus, VT always should be assumed until proven otherwise. Given slightly atypical features for RBBB/LPHB (as described above), the likelihood that this rhythm represents fascicular VT would seem to be at least 90%. Given the presence of symptoms plus low blood pressure at the time this tracing was recorded, immediate cardioversion was indicated regardless of whether the etiology of this rhythm was VT or supraventricular tachycardia with either preexisting bundle branch block or aberrant conduction.
The patient received an electrical shock, which promptly converted the arrhythmia to sinus rhythm. Surprisingly, QRS morphology in sinus rhythm was virtually identical to that during the tachycardia. Thus, the patient demonstrated underlying bifascicular block (RBBB/LPHB), albeit with a slightly atypical appearance. This case highlights the fact that despite the clinical reality that most WCT rhythms without sinus P waves will turn out to be VT, on occasion the tachycardia may turn out to be supraventricular. One simply cannot always distinguish the two based on the initial ECG. That said, when the patient is hemodynamically unstable (as was the case here), immediate cardioversion is indicated regardless of whether the rhythm is VT or SVT.
For further discussion of this case, please visit: http://bit.ly/2oL9vqE.
The ECG in the figure in this story was obtained from a 55-year-old man who presented for emergency care with palpitations and fatigue. His blood pressure was 80/50 mmHg at the time the tracing was recorded. Is this a case of ventricular tachycardia?
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