You are asked to see a patient with a pulse rate of 45 /mt . Is it sinus bradycardia or complete heart block ?
Only one condition , . . . you must conclude in the bed side !
- Heart rate may give a clue ( HR of 30-40 is common in CHB . Less common in sinus bradycardia.)
- Pulse volume is large in both (More so in CHB )
- JVP shows occasional cannon waves hitting the neck in CHB. Cannon wave can never occur in sinus rhythm
- S 1 intensity may vary in CHB (As Marching through of P waves occur in CHB , when it falls close to QRS , it results in a short PR interval and a loud S1 . Since marching through is a intermittent phenomenon S 1 intensity also varies.)
- A short systolic murmur may be heard intermittently due to trivial MR/TR in CHB ( Competitive AV valve movement )
- A simple bed side test . Ask the patient to exert for a minute -Sinus bradycardia raises the HR with a fair regularity to 80-90/mt or so. CHB doesn’t (Note : CHB with junctional rhythm can sometimes increase the HR significantly )
- Finally response to Atropine is prompt with sinus bradycardia.
Final message
Bed side skills in recognising cardiac arrhythmias are still relevant even in the current era of carto and 3d electro anatomic mapping .
After all , the 19th century clinical wizard Wenke back recognised the second degree AV block at the bed side well before the ECG machine was invented. He meticulously observed progressive prolongation of a-c interval and subsequent drop of c wave in the jugular vein !
Dr.S.Venkatesan MD 
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