The term premature atrial contraction refers to an atrial contraction that occurs as the result of any atrial pacemaker site other than the Sino-Atrial (SA) node. Premature Atrial Contractions (PACs) are the most common cause of Sinus Arrythmia. Although little is known about the exact aetiology of the condition, it is known that a Prematuer Atrial Contraction occurs whenever any area within the atria depolarizes before the SA node has a chance to fire. In generaly, PACs are common and occur in otherwise healthy patients.
Premature atrial contractions my occure as single events or sets of multiple PACs. Sets of two PACs with the QRS complexes following coupled together is called atrial bigeminy, while atrial trigeminy or quadrigeminy refers to three or four PACs.
Pramature Atrial Contractions ECG
Heart Rate: normal (usually between 60-100 per minutes).
Rhythm: irregular when PACs are present.
Pacemaker Site: an ectopic atrial pacemaker.
P-waves: occure earlier than the normal expected P wave.
QRS complex: Normal.
PR Interval: Normal – 0.12-0.20 seconds in duration, but may vary between depending on when the PACs depolarize.
Premature Atrial Contractions Signs and Symptoms
People who have premature atrial contractions usually are asymptomatic. If the condition is particularly exacerbated (by excess caffeine intake or stimulants) the patient may feel minor palpitations.