Question 30
This is the ECG of a 73 year old man who was noticed to have a slow pulse rate. He has a past history of ischemic heart disease and is being treated with digoxin and beta- adrenergic blockers.
What is the rhythm? What is the conduction abnormality? Please justify your responses.
College Answer
The rhythm is Atrial Flutter with a high degree (but apparently consistent) AV block, and a ventricular rate of approximately 40/minute. There is an obvious saw-tooth pattern of atrial depolarisations (at a rate of approximately 250/min) seen in many leads. Association between the flutter and the ventricular depolarisations is based on the finding of a constant PR interval (with a fixed relationship between the P wave and the QRS complex), which excludes AF, and complete heart block.
The conduction abnormality is a tri-fascicular block as it includes:
• Second degree (Mobitz II) AV block (as evidenced by constant relationship between P waves and the QRS)
• Right bundle branch block (QRS > 0.12, RSR in V1, S in lead 1)
• Left anterior hemiblock implied by left axis deviation (slightly positive in 1, negative with small R waves in II and III)
Discussion
The accuracy and completeness of the college answer makes it difficult to discuss this question.
Certainly, I cannot improve on their response.
One can read further about these ECG abnormalities within the body of this site:
- Right bundle branch block
- Different varieties of heart block
- Left anterior fascicle block
- Bifascicular and trifascicular block
Or one could review the topic properly at LITFL.