3 Tachycardia-bradycardia (“tachy-brady”) syndrome Some important examples of arrhythmias include tachycardia-bradycardia syndrome, sinus bradycardia and sinus arrest, sinoatrial exit block and slow atrial fibrillation. transitional cells).Īrrhythmias seen may change over time and are often intermittent. Several different arrhythmias may arise according to the specific dysfunction of the SAN (e.g. For example, there may be a degree of age-related fibrosis of the SA node which is exacerbated by infarction of the SA node after an inferior myocardial infarct, or by the addition of medications such as beta-blockers.

The exact cause is often difficult to identify and there may be multifactorial precipitants. ‘Hypers’: hyperkalaemia, hyperthyroidism.‘Hypos’: hypothermia, hypothyroidism, hypoxia.Drugs: digoxin, beta-blockers, calcium channel blockers, anti-arrhythmics.Iatrogenic: for example, damage to the SA node during open-heart surgery.sarcoidosis, amyloidosis, haemochromatosis) Idiopathic fibrosis: age-related degeneration of the SAN is the most common cause of sinus node dysfunction.The causes of sick sinus syndrome can be divided into intrinsic and extrinsic causes. The electrical conduction system of the heart.

In sick sinus syndrome, dysfunction of the SAN leads to an atrial rate that is inappropriate for normal requirements. 3įor more information on the cardiac conduction system, see the Geeky Medics article here. Transitional cells facilitate the propagation of the impulse across the atria (Figure 1). Pacemaker cells have intrinsic pacemaker activity and initiate action potentials at regular intervals. The SAN contains two types of specialised cells. You might also be interested in our medical flashcard collection which contains over 2000 flashcards that cover key medical topics.

Liftl junctional escape rhythm