Clinical, Electrical, and Mechanical Parameters in Potassium Channel-Mediated Congenital Long QT Syndrome.

Congenital long QT syndrome (LQTS) is a rare cardiac disorder caused by repolarization abnormalities in the myocardium that predisposes to ventricular arrhythmias and sudden cardiac death. Potassium channel-mediated LQT1 and LQT2 are the most common types of channelopathy. Recently, LQTS has been acknowledged as an electromechanical disease. A total of 87 genotyped LQT1/LQT2 patients underwent cardiac evaluation. A comparison between LQT1 and LQT2 electrical and mechanical parameters was performed. LQT2 patients had worse electrical parameters at rest: a longer QTc interval ( = 0.007), a longer T in lead V2 ( = 0.028) and in lead V5 ( < 0.001), and a higher T/QT ratio in lead V2 ( = 0.011) and in lead V5 ( = 0.005). T and T/QT remained significantly higher in the LQT2 group after brisk standing. T was longer in LQT2 patients compared with LQT1 patients during peak exercise ( = 0.007) and almost all recovery periods in lead V2 during EST. The mid-cavity myocardium mean radial contraction duration (CD) was longer in LQT2 patients ( = 0.02). LQT2 patients had a longer mean radial CD in mid-septal ( = 0.015), mid-inferior ( = 0.034), and mid-posterior ( = 0.044) segments. Potassium channel-mediated LQTS has different effects on cardiac electromechanics with a more pronounced impact on LQT2 patients. T was more prominent in the LQT2 cohort, not only at rest and brisk standing but also during EST exercise and at recovery phases. The altered mean radial CD in the mid-cavity myocardium was also specific for LQT2 patients.