A.Fib with RBBB

A 35 year old man presented with new onset palpitations.

+ Figure 1 (R-0030A) is the initial 12 lead ECG. Describe the main findings in this tracing.

The ventricular rate is about 100 beats per minute, and the ventricular rhythm is irregular, although some R-R intervals are the same i.e. there is a suggestion of semi-regular irregularity rather than the irregular irregularity that is typical of atrial fibrillation.

Atrial activity: The inferior leads have negative saw tooth deflections that are similar to the "F" (flutter) waves that occur in atrial flutter. The amplitude and shape of these F waves is variable, unlike the regularity that is usually present in atrial flutter. In atrial flutter upright P waves are usually seen in Lead V1, typically at a rate of 300 beats per minute. This means a 'P-P' interval that is usually 5 mm [5 small squares] in atrial flutter. Lead V1 in this case shows tall "P" waves which have a amplitude of 5 mm, and are nearly as tall as the RsR1 ventricular complexes (indicated by a green asterix).

The P-P intervals in Lead V1 are slightly irregular at 3 - 4 mm, corresponding to a atrial rate between 375 beats per minute and 500 beats per minute (although the most frequent P-P interval is 3.5 mm, which corresponds to a atrial rate of about 429 beats per minute). The irregularity and rate of the atrial activity in Lead V1 favours atrial fibrillation rather than atrial flutter; the amplitude of the atrial activity means that coarse atrial fibrillation is present (coarse atrial fibrillation is defined as “f” [fibrillation] waves with an amplitude that is greater than 0.5 mm).

Right bundle branch block is present: the width of the QRS complexes is 0.12 seconds, there are S waves in Leads 1 and V6 and Lead V1 has a RsR1 configuration

The frontal plane axis is normal (at about 600)

Main points

  • Coarse atrial fibrillation with a ventricular rate of about 100 beats per minute
  • Right bundle branch block

+ Figure 2 (R-0030B) is a subsequent 12 lead ECG. Describe the main findings in this tracing

  • Sinus rhythm is present with a ventricular rate of about 83 beats per minute.
  • Right bundle branch block is present.
  • The frontal plane QRS axis is normal (about + 900)
  • P pulmonale is present (see Figure 3, which shows the P wave in Lead 2 and Lead V1)