This case was provided by Mark Santamaria
Stem: This is the tracing of a middle aged man who presented with dyspnoea and palpitations. There was no preceding chest pain.
+ List the significant findings in the ECG and provide the most likely or important diagnosis.
- The ECG shows a bigeminal rhythm: a normal QRS complex is followed by a widened complex with abnormal morphology. The rhythm strip shows that each abnormal QRS complexes has the same shape i.e they have uniform morphology
- The ventricular rate is about 100 beats per minute
- Figure 2 compares the 12 lead morphology of the sinus beats with that of the abnormal beats
- A. Sinus beats: Normal axis; left ventricular hypertrophy; inverted T wave in Lead aVL
- B. **Bigeminal (abnormal) beats: Left bundle branch block pattern; right axis deviation**
- The intervals between the sinus beats and the abnormal beats are shown in Figure 3. The R-R' interval between the sinus complex and the abnormal complex - coupling interval - is constant (760 msec). The R'-R interval between the abnormal complex and the sinus beats is also constant (between 600-640 msec)
- A constant coupling interval favours a diagnosis of ventricular ectopic beats, but in Leads V1 and V2 a P wave is seen before the ectopic complex (marked as * in Figure 4).
- The most likely diagnosis is atrial bigeminy with aberrant conduction and a constant coupling interval