Section 3. Heart and Blood Vessel Disorders

Chapter 27. Abnormal Heart Rhythms

Topics: Introduction | Atrial Premature Beats | Atrial Fibrillation and Atrial Flutter | Paroxysmal Supraventricular Tachycardia | Wolff-Parkinson-White Syndrome | Ventricular Premature Beats | Ventricular Tachycardia | Ventricular Fibrillation | Pacemaker Dysfunction | Heart Block | Bundle Branch Block

Paroxysmal Supraventricular Tachycardia

Paroxysmal supraventricular (atrial) tachycardia is a regular, fast (160 to 200 beats per minute) heart rate that begins and ends suddenly and originates in heart tissue other than that in the ventricles.

Paroxysmal supraventricular tachycardia is most common among young people and is more unpleasant than dangerous. It may occur during vigorous exercise.

Paroxysmal supraventricular tachycardia may be triggered by a premature heartbeat that repeatedly activates the heart at a fast rate. This repeated, rapid activation may be caused by several abnormalities. There may be two electrical pathways in the atrioventricular node (an arrhythmia called atrioventricular nodal reentrant supraventricular tachycardia). There may be an abnormal electrical pathway between the atria and the ventricles (an arrhythmia called atrioventricular reciprocating supraventricular tachycardia). Much less commonly, the atria may generate abnormal rapid or circling impulses (an arrhythmia called true paroxysmal atrial tachycardia).

The fast heart rate tends to begin and end suddenly and may last from a few minutes to many hours. It is almost always experienced as an uncomfortable palpitation. It is often associated with other symptoms, such as weakness, light-headedness, shortness of breath, and chest pain. Usually, the heart is otherwise normal.

Treatment

Episodes of paroxysmal supraventricular tachycardia often can be stopped by one of several maneuvers that stimulate the vagus nerve and thus decrease the heart rate. These maneuvers are usually conducted or supervised by a doctor, but people who repeatedly experience the arrhythmia often learn to perform the maneuvers themselves. Maneuvers include straining as if having a difficult bowel movement, rubbing the neck just below the angle of the jaw (which stimulates a sensitive area on the carotid artery called the carotid sinus), and plunging the face into a bowl of ice-cold water. These maneuvers are most effective when they are used shortly after the arrhythmia starts.

If these maneuvers are not effective, if the arrhythmia produces severe symptoms, or if the episode lasts more than 20 minutes, people are advised to seek medical intervention to stop the episode. Doctors can usually stop an episode promptly by giving an intravenous injection of a drug, usually adenosine or verapamil. Rarely, drugs are ineffective, and cardioversion (delivery of an electrical shock to the heart) may be necessary.

Prevention is more difficult than treatment, but almost any antiarrhythmic drug may be effective. Drugs commonly used include beta-blockers, digoxin, diltiazem, verapamil, propafenone, and flecainide. Increasingly, radiofrequency ablation (delivery of energy of a specific frequency through an electrode catheter inserted in the heart) is being used to destroy the tissue in which paroxysmal supraventricular tachycardia originates.