By Ken Grauer, MD
Professor Emeritus in 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.

ECG

The 12-lead ECG and accompanying long lead II rhythm strip in the Figure was obtained from a 70-year-old woman with chest pain. She was hemodynamically stable at the time this ECG was recorded. What is the rhythm? How certain are you of your rhythm diagnosis? Is there any clue to the etiology of her chest pain?

Interpretation: This is a challenging tracing. Fortunately, the patient was hemodynamically stable, which provided a moment of time for analysis.

  • The predominant rhythm is a regular WCT (wide complex tachycardia) without normal P waves. Statistically, the odds that a regular WCT rhythm without sinus P waves in an older adult with chest pain will turn out to be VT (ventricular tachycardia) approach 90%, even before one looks at the ECG.
  • Assessment of Axis and QRS morphology during the tachycardia often provide additional clues that the rhythm is VT rather than supraventricular tachycardia with either aberrant conduction or pre-existing bundle branch block. For example, the extreme axis deviation seen here (i.e., all negative QRS complex in lead I) virtually proves this is VT. Support for this conclusion is enhanced by the fact that this all negative QRS waveform in lead I does not resemble any type of conduction defect.
  • Definitive proof that the rhythm is VT is forthcoming from the long lead II rhythm strip. Note intermittent occurrence of narrow QRS complexes (i.e., beats #2,10,19,23) that interrupt the underlying WCT rhythm. These narrow (seemingly normal) conducted complexes are “capture” beats. They are each preceded by a sinus P wave (red arrow preceding beat #19 showing one such P wave). In addition, there is at least one “fusion” beat, as the QRS complex of beat #11 is intermediate in size and shape compared to the beat that precedes it (#10) and the beat that follows (#12). The presence of fusion and capture beats provides definitive proof that the rhythm is VT. 

Note: Further discussion of this tracing is available on an ECG video and blog post found at this site: http://tinyurl.com/KG-Blog-102.