The Short QT Syndrome

Abstract

The short QT syndrome (SQTS) is a rare inherited ion channel disease associated with life-threatening arrhythmias and familiar sudden death (SD) in the absence of cardiac structural abnormalities. The diagnosis is based on the detection of constantly short QTc values at ECG (≤ 340 ms) and the presence of previous aborted CA (aCA) or syncope, a family history of SD or SQTS, or a positive genotype supporting the diagnosis in borderline cases. Mutations causing hyperfunction of genes encoding for potassium channels, but also reduced function of the calcium channel involved in the cardiac repolarization, have been associated with the disease (SQTS1-6), although the yield of the genetic test is scarce (less than 25%) and precise data on genotype-phenotype correlation are lacking due to the extreme rarity of the condition. Males are diagnosed more often than females, representing more than 75% of cases. The mean age at observation is below 25 years. SD or aCA is the first symptom in one-third of subjects, occurring mostly in the first year of life and between 20 and 40 years, both at rest and during exercise, without gender differences. A previous cardiac arrest is the only recognized risk factor for events at follow-up. An implantable cardiac defibrillator is the therapy of choice in high-risk patients but is burdened by high rates of complications, including inappropriate shocks. Prophylactic therapy with hydroquinidine proved to be effective in prolonging the QT interval and prevent the occurrence of arrhythmias in previously symptomatic and asymptomatic subjects.