Signs and symptoms
Signs and symptoms can arise suddenly and may resolve without treatment. Stress, exercise, and emotion can all result in a normal or physiological increase in heart rate, but they can precipitate SVT in rare cases. Episodes can last from a few minutes to one or two days. They sometimes persist until treated. The rapid heart rate, if fast enough, reduces the opportunity for the "pump" to fill between beats decreasing cardiac output and consequently blood pressure. The following symptoms are typical with a rate of 150–270 or more beats per minute:
Pounding heart
Rapid heart beat
Shortness of breath
Chest pain
Rapid breathing
Dizziness
Sweating
Loss of consciousnessSymptoms of heart arrhythmias, such as SVT, are more difficult to assess in infants and toddlers because of their limited ability to communicate. Caregivers should watch for lack of interest in feeding, shallow breathing, and lethargy. These symptoms may be subtle and may be accompanied by vomiting and/or a decrease in responsiveness. Pathophysiology
The main pumping chamber, the ventricle, is protected (to a certain extent) against excessively high rates arising from the supraventricular areas by a "gating mechanism" at the atrioventricular node, which allows only a proportion of the fast impulses to pass through to the ventricles. An accessory "bypass tract" can avoid the AV node and its protection so that the fast rate may be directly transmitted to the ventricles. This situation has characteristic findings on ECG. A congenital heart lesion, Ebsteins anomaly, is most commonly associated with supraventricular tachycardia. Diagnosis
Subtypes of SVT can often be distinguished by their electrocardiogram (ECG) characteristics.
Aschers syndrome, is a rare disorder first described in 1920. It is characterized by repeated episodes of lip and eyelid edema and occasionally euthyroid goiter. The syndrome generally occurs within the first 20 years of life. About 100 cases had been described by 1998. Signs and Symptoms
Blepharochalasis : Recurrent episodes of swelling cause stretching and atrophy of the upper eyelid skin. This results in the relaxation of the tarsal fold allowing tissue to slack over the palpebral fissure. In severe cases, the lower eyelid is also involved. Double Upper Lip : Swelling causes duplication between the inner and outer parts of the upper lip. Occasionally the lower lip is involved. Euthyroid Goiter : Occurs in 10% of cases. It is not usually associated with toxic symptoms. Goiter usually presents several years after initial eyelid and lip edema. Diagnosis
Treatment
Cosmetic surgery is generally the treatment of choice. References


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