Introduction To Bradycardia

Bradycardia is defined as heart rate of less than 60 beats per minute.

Clinical Presentation

• Often patients do not have any symptoms and it is detected as an incidental finding on routine physical examination.
• Some patients may present with faints or blackouts, drop attacks, dizziness, breathlessness or lack of energy.
• Findings on examination are slow pulse rate; normal or low BP with or without an evedence of secondary heart failure.
• Sometimes there may be symptoms and signs of any associated disease that may help in diagnosing the cause of bradycardia.

InvestigationsA patient presenting with bradycardia with or without any associated symptoms should have following basic investigations done:

ECG: Ambulatory ECG may help with diagnosis of intermittent bradycardia as in sick sinus syndrome.
Blood tests: Thyroid function tests, Complete blood count, ESR, Urea, creatinine, LFTs, and digoxin levels (if pt taking digoxin).

Types Of Bradycardia

1. Sinus Bradycardia
There is a constant bradycardia and ECG shows normal P waves and P-R interval is <0.2 sec. 

Causes of sinus bradycardia are:

• Physiological e.g atheletes
• Vasovagal attack
• Drugs e.g b -blockers, digoxin
• Inferior wall MI
• Sick sinus syndrome
• Hypothyroidism
• Hypothermia
• Increased intracranial pressure
• Jaundice

If patient is symptomatic management is hospital admission and cardiology referral.

2. AV node block (Heart block)Causes are

• Ischemic heart disease
• Drugs e.g digoxin, verapamil
• Myocarditis
• Cardiomyopathy
• Fibrosis
• Lyme’s disease

Types of heart block

1. 1st degree heart block: Fixed P-R interval >200ms on ECG.
2. 2nd degree block: It has two types :
3. Mobitz type I: There is progressive lengthening of P-R interval followed by a dropped beat.
4. Mobitz type II: constant P-R interval with regular dropped beats.
5. 3rd degree block: it is a complete block in which P-P intervals are constant and R-R intervals are constant but not related to each other.

Patients with heart block should be referred to a cardiologist even if asymptomatic.

3. Stokes-Adams attack
It is defined as cardiac arrest due to AV block. Patients present with sudden loss of consciousness due to cerebral anoxia. The patient becomes pale and pulseless but respiration continues. attacks usually lasts apprx. 30 sec though occasionally are fatal. On recovery the patient becomes flushed. patients should be referred to cardiologist if suspected.

4. Sick sinus syndromeDue to sinus node dysfunction causing bradycardia with or without asystole, sino-atrial block, atrial fibrillation or supraventricular tachycardia. It is common among elderly patients. If symptomatic patients will need a pace maker.