Tuesday, January 29, 2013

Heart rate of 230 beats per minute

What can you say about this ECG at a rate of 230 beats per minute?
Answer below

The QRS is very narrow (about 70 ms?), so it must be a pediatric ECG. 

Thus, the fact that the rate is 230 bpm does not necessarily mean that it is SVT because infants can have very fast sinus rhythm.  Thus, what appear to be p-waves are indeed p-waves (see leads II and V1).  This is from a febrile 3 month old infant.  The ECG was done because the heart rate was 230 and the differential included SVT vs. sinus tachycardia.  This ECG, and the fact that the heart rate was variable (not constant) confirmed sinus tach.  Note also how the PR interval is very short.  Again, this because all intervals in infants are short. 

Notice also that there is right ventricular hypertrophy.  There is an S-wave in lead I, tall R-waves in leads V1-V3, with late transition to S-waves in precordial leads, and T-wave inversion in right precordial leads.  This is typical of pediatric ECGs because the fetal circulation depends on the right ventricle.  So these are normal findings in the ECG of an infant.

With management of fever and dehydration, the heart rate normalized.

Never trust the computer read.  The computer read is usually very good at determining pacemakers and intervals, but it was way off in this case:  it said: "electronic ventricular pacemaker" and measured the QRS at 202 ms!


  1. " This ECG, and the fact that the heart rate was variable (not constant) confirmed sinus tach. " Why at SVT the rate is constant? Or usually increasable?

    1. because sinus tach is an automatic rhythm dependent on the balance of sympathetic and parasympathetic activity, which is constantly changing based on such factors as volume, stroke volume, cardiac output, oxygenation, etc, then sinus tach is variable. SVT is due to a re-entrant rhythm which goes around and around a loop which is barely affected by other factors.

    2. Great explanation! Thank you!

  2. I work for an cardiology equipment company (www.cardiologyforless.com) and sell ekgs every day. Your website is a great resource for learning more about the analysis and interpretation of ekg machines. I know a lot about the actual machines but I am lacking in the interpretation area. Thanks for a great site.


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