Paroxysmal supraventricular tachycardia
Paroxysmal supraventricular tachycardia (PSVT) is a type of supraventricular tachycardia, named for its intermittent episodes of abrupt onset and termination. Often people have no symptoms. Otherwise symptoms may include palpitations, feeling lightheaded, sweating, shortness of breath, and chest pain. The cause is not known. Risk factors include alcohol, caffeine, nicotine, psychological stress, and Wolff-Parkinson-White syndrome, which often is inherited. The underlying mechanism typically involves an accessory pathway that results in re-entry. Diagnosis is typically by an electrocardiogram (ECG) which shows narrow QRS complexes and a fast heart rhythm typically between 150 and 240 beats per minute. Vagal maneuvers, such as the Valsalva maneuver, are often used as the initial treatment. If not effective and the person has a normal blood pressure the medication adenosine may be tried. If adenosine is not effective a calcium channel blocker or beta blocker may be used. Otherwise synchronized cardioversion is the treatment. Future episodes can be prevented by catheter ablation. About 2.3 per 1000 people have paroxysmal supraventricular tachycardia. Problems typically begin in those 12 to 45 years old. Women are more often affected than men. Outcomes are generally good in those who otherwise have a normal heart. An ultrasound of the heart may be done to rule out underlying heart problems. Symptoms may include palpitations, feeling faint, sweating, shortness of breath, and chest pain. Episodes start and end suddenly. AV nodal re-entrant tachycardia (AVNRT) makes up 56% of cases Atrioventricular reentrant tachycardia (AVRT) makes up 27% of cases Wolff-Parkinson-White syndrome Paroxysmal atrial tachycardia makes up 17% of cases AV nodal blocking can be achieved in at least three ways: A number of physical maneuvers increase the resistance of the AV node to transmit impulses (AV nodal block), principally through activation of the parasympathetic nervous system, conducted to the heart by the vagus nerve.
