In health, the SAN regulates the heart, resulting in a regular rhythm and coordinated muscle contraction. Acutely unwell patients are at risk of developing rhythm problems, so assessment, recognition and timely escalation by the nurse is essential for safe, effective care. Arrhythmias are abnormalities of heart rate or rhythm, caused by:

• Pacemaker problems: when the SAN, the heart’s natural pacemaker, fails to generate an electrical impulse, or is overcome by the generation of impulses from non-pacemaker cells (i.e. myocardial cells).
  
• Conduction problems: the path of an electrical impulse may be blocked, or the electrical signal circles back to stimulate a second impulse, instead of naturally ending (re-entry circuit).

Common disorders that may lead to arrhythmias include: MI, cardiomyopathy, heart failure, congenital heart disease, cardiac surgery, electrolyte and acid-base imbalance, drugs (e.g. digoxin, beta blockers) and hypoxaemia.

Tachyarrhythmias