Bradycardia - Heart Block

First-Degree Heart Block: in this the PR segment on the ECG is more than 200ms and all P waves are followed by QRS complexes. The PR interval is similar across the cycles.

Second-Degree Heart Block: This is of 2 types:

• Type I (Mobitz I or Wenckebach) - In this the PR segment duration progressively increases with each successive cycle and subsequently the P wave is not followed by a QRS complex.
• Type II (Mobitz II) - In this the PR segment duration is prolonged & fixed and after a few cycles the P wave is not followed by the QRS complex. 

Third-Degree (Complete) Heart Block: In this the P wave and QRS complexes are asynchronous i.e. the P waves and QRS complexes occur without any relation to each other. In simpler words the atria and ventricles do not function synchronously. 

Most common reason is old age.

Drug induced like beta blockers, ditiazem, verapamil, occasionally digoxin and amiodarone.

Congenital complete heart block can occur in children in whom the conduction system is not well developed since birth.

• Most 1st degree and some 2nd degree heart block patients may be asymptomatic and are diagnosed incidentally on the ECG.
• Usually people with higher degree AV blocks can present with giddiness, syncope or falls.
• They may also complain of tiredness or shortness of breath and swelling over the feet.

ECG is the mainstay to diagnose bradycardia and heart blocks. If the ECG changes are intermittent, then holter monitoring i.e. prolonged heart rhythm monitoring may be needed to diagnose heart blocks.

Medical management in the form of withholding the offending drug.

Pacemaker Implantation - Different companies like Abbott, Medtronic, Biotronik etc. are making pacemakers with varied specifications.

Types:

• Single chamber - i.e. these pacemakers pace only the right ventricle. Usually deployed when patients also have underlying atrial fibrillation.
• Double chamber - i.e. these pacemakers pace the right atria and the ventricle. If the patient has a sinus rhythm, then these pacemakers should be inserted.

CRT - i.e. Cardiac Resynchronisation Therapy, these special type of pacemakers which are used in patients having reduced left ventricular ejection fraction. These pacemakers have an additional lead pacing the left ventricle to help improve synchrony and thus the ejection fraction i.e. the pumping mechanism of the heart.

ICD - Implantable Cardiac Defibrillator, these types of special pacemakers have in addition to the pacing capacity, can provide electric shock to the heart in times of ventricular tachycardia or fibrillation, for its reversal to reduce the chances of sudden cardiac death.

• Pacemaker Checks every yearly at the least.
• Medication Management and physician follow ups regularly.
• Patient Education: in the form of understanding device use, recognizing symptoms of malfunction and changes in lifestyle and physical activities post pacemaker deployment.