Answer: D
R00.1 is the appropriate code here when it is used to specify bradycardia that is unspecified. Here, the cause is not mentioned here, so it is the correct code.
Option A is not correct because R00.2 is used to specify palpitations but this is not the diagnosis here.
Option B is not correct because R00.8 is used to specify abnormalities of heartbeat other than bradycardia, tachycardia, and palpitations but here, bradycardia is the diagnosis.
Option C is not correct because R00.00 is used to specify tachycardia, unspecified. Here, the diagnosis is bradycardia.
