Cardiology Teaching Package
A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias
Symptom Control
Patients who arrive in A & E with Atrial Fibrillation often have symptoms of: chest pain; shortness of breath and palpitations. As with other conditions, the immediate symptoms are treated first. This patient will have:
- Oxygen therapy to increase the circulating oxygen level.
- GTN , a vasodilator commonly used for angina pain as it helps to open up the coronary arteries to increase the blood and oxygen supply to the heart muscle.
- Adenosine/Digoxin to slow down the heart and allow the ventricles to work more efficiently. (optimum rate 70-90 and symptom free)
- Warfarin/Heparin anti-coagulation is to reduce the risk of clot formation.
Please note. A Supra-ventricular Tachycardia (SVT) such as Atrial Fibrillation or Atrial Flutter is often treated with Adenosine or Digoxin to slow it down. Electrical cardioversion is an alternative treatment to re-assert sinus rhythm.
- Adenosine has a very brief half-life (1-6 seconds) and causes blockage of the AV node. This means that, in AF where 100s of impulses are being generated, fewer impulses will be conducted through the AV node and, consequently, the rate of ventricular contraction will decrease making it easier to identify the arrhythmia.
- Digoxin increases the force of myocardial contraction and slows down from both the SA and AV nodes. In other words, it slows down and strengthens the heart beat. It is not a cardioverting drug but the act of slowing the heart down often helps the heart re-assert it's normal rhythm.
- Electrical (DC) Cardioversion is the delivery of a shock to the myocardium using a defibrillator. Normal defibrillation is the delivery of a large shock to the heart ASAP. Electrical Cardioversion is the delivery of a synchronised electric shock at the point in the conduction cycle where the atria is repolarising. The effect is to literally stop and restart the heart. It is hoped that when the heart restarts, the SA node restarts with normal function.
