Paroxysmal atrial tachycardia
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Paroxysmal atrial tachycardia is a period of very rapid and regular heart beats that begins and ends abruptly. The heart rate is usually between 160 and 200 beats per minute. This condition is also known as paroxysmal supraventricular tachycardia.
Etiology
Paroxysmal atrial tachycardia may be caused by several different things. The fast rate may be triggered by a premature atrial beat that sends an impulse along an abnormal electrical path to the ventricles. Other causes stem from anxiety, stimulants, overactive thyroid, and in some women, the onset of menstruation.
Symptoms
Paroxysmal atrial tachycardia produces annoying symptoms which can include:
Diagnosis
Diagnosis of paroxysmal atrial tachycardia is not always easy, because the event is usually over by the time the patient sees a doctor. A careful description of the episode will aid the doctor in his diagnosis.
If the rapid heart rate is still occurring, an electrocardiogram (ECG) will show the condition.
If the event is over, physicians often recommend a period of ambulatory electrocardiographic monitoring (called Holter monitoring) to confirm the diagnosis.
Electrocardiographic Findings:
- There are two mechanisms:
- Intraatrial reentrant tachycardia
- Automatic or ectopic atrial tachycardias
- PAT used to be thought of as a common cause of Paroxysmal Supraventricular Tachycardia (PSVT), but it is now realized that intranodal reentry is more common.
- PAT accounts for about 10% of PSVTs.
- There are abnormal P waves that are different form those in Normal Sinus Rhythm (NSR). These P waves are often small and hard to identify.
- The atrial rate is 100 to 180 Beats Per Minute (BPM). Rate is usually < 150 in the atrial reentrant form.
- The rhythm is regular
- A paroxysm has three or more beats in succession.
- There is a QRS after each P wave that resembles that of NSR, but aberrancy can occur.
- PR interval is within normal limits or prolonged.
- Secondary ST segment and T wave changes may occur.
- The rhythm may speed up after the first few beats.
- Not affected by vagal maneuvers.
- If some of the P waves are not followed by a QRS, then this is called PAT with block.
- Patients with PAT usually have organic heart disease.
Treatment
The doctor may suggest that during an episode of paroxysmal atrial tachycardia the following practice may help.
- Briefly hold the nose and mouth closed and breathe out, or by bearing down, as though straining at a bowel movement.
- The doctor may try to stop the episode by gently massaging an area in the neck called the carotid sinus.
- If these conservative measures do not work, an injection of the drug verapamil or adenosine should stop the episode quickly.
In rare cases, the drugs do not work and electrical shock (cardioversion) may be necessary, particularly if serious symptoms are also present with the tachycardia.
Prevention
Frequent episodes are usually cause for medication.
In drug resistant rare cases, the cardiologist may recommend a procedure called catheter ablation, which will remove (or ablate) the precise area of the heart responsible for triggering the fast heart rate.
In a catheter ablation procedure, the electrophysiologist will place a special catheter against the area of the heart responsible for the problem. Radio-frequency energy is then passed to the tip of the catheter, so that it heats up and destroys the target area.
Catheter ablation is considered a non-surgical technique.
Prognosis
Paroxysmal atrial tachycardia is not a disease, and is seldom life-threatening.
The episodes are usually more unpleasant than they are dangerous, and the prognosis is generally good.