Heart rhythm abnormalities, also known as arrhythmias, are disorders of the heart rate or rhythm — meaning the heart can beat, for example, too fast, too slow, or irregular. 
 
An overview: 
 
Normal Heart Rhythm 
The normal heartbeat originates in the sinoatrial (SA) node, the heart’s natural pacemaker. 
A normal resting heart rate is 60–100 beats per minute (bpm). 
This regular rhythm is called normal sinus rhythm. 
 
Types of Heart Rhythm Abnormalities (Arrhythmias): 
 
1. Tachyarrhythmias – Heart rate >100 bpm 
 
a. Supraventricular (origin above ventricles): 
Sinus tachycardia – normal response to exercise, fever, anxiety. 
Atrial fibrillation (AFib) – irregular, often rapid rhythm; no distinct P waves. 
Atrial flutter – regular “sawtooth” pattern (2:1 or 3:1 – P:QRS);  
Paroxysmal supraventricular tachycardia (pSVT) – sudden onset/offset, rapid regular rhythm, typically ~150 bpm. 
 
b. Ventricular (origin in ventricles): 
Ventricular tachycardia (VT) – fast, regular rhythm from ventricles; can be life-threatening or cause cardiac arrest – remember patients with VT can have a pulse. 
Ventricular fibrillation (VF) – chaotic, ineffective contraction; cardiac arrest if not treated immediately. 
 
2. Bradyarrhythmias – Heart rate <60 bpm: 
Sinus bradycardia – may be normal in athletes or during sleep. 
Sick sinus syndrome – malfunction of SA node; alternating fast/slow rhythms. 
Heart block (AV block): 
First-degree – prolonged PR interval. 
Second-degree – some dropped beats (not every P wave is followed by a QRS complex) 
Third-degree (complete) – no communication between atria and ventricles; dangerous. 
 
3. Premature Beats 
Premature atrial contractions (PACs) or premature ventricular contractions (PVCs) – early beats; may feel like a “skipped” heartbeat. 
 
 Symptoms 
Palpitations (feeling your heart race or skip) 
Dizziness or lightheadedness 
Shortness of breath 
Chest pain or discomfort 
Fatigue 
Syncope (fainting) 
 
Diagnosis 
ECG (Electrocardiogram) – main diagnostic tool 
Holter monitor – 24–48 hour continuous ECG monitoring 
Event recorder / implantable loop recorder 
Echocardiogram, blood tests, electrophysiological studies in cath lab 
 
Treatment Options – often acute arrhythmia requires urgent intervention: 
 
Depends on type of rhythm abnormality and cause: 

Electrolyte supplementation (in acute phase) – Potassium>4.5mmols/l; Magnesium>1.0mmols/l 

Medications: 
Beta-blockers, calcium channel blockers, anti-arrhythmics 

Electrical therapies: 
Cardioversion (for AF/flutter, VT) 
Defibrillation (for VF/pulseless VT) 
Pacemaker (for bradycardia/sympromatic heart blocks) 
Implantable cardioverter-defibrillator (ICD) (for life-threatening arrhythmias) 
Ablation therapy – destroys abnormal electrical pathways. 
Lifestyle modification (avoid caffeine, alcohol, stress) – chronic phase 
 
️Prognosis 
Benign in many cases (e.g., occasional PACs/PVCs) 
Potentially fatal in others (e.g., VF, sustained VT) 
Early diagnosis and management greatly improve outcomes.