Short QT Syndrome

Abstract

Background-A prolonged QT interval is associated with a risk for life-threatening events. However, little is known about prognostic implications of the reverse-a short QT interval. Several members of 2 different families were referred for syncope, palpitations, and resuscitated cardiac arrest in the presence of a positive family history for sudden cardiac death. Autopsy did not reveal any structural heart disease. All patients had a constantly and uniformly short QT interval at ECG. Methods and Results-Six patients from both families were submitted to extensive noninvasive and invasive work-up, including serial resting ECGs, echocardiogram, cardiac MRI, exercise testing, Holter ECG, and signal-averaged ECG. Four of 6 patients underwent electrophysiological evaluation including programmed ventricular stimulation. In all subjects, a structural heart disease was excluded. At baseline ECG, all patients exhibited a QT interval Յ280 ms (QTc Յ300 ms). During electrophysiological study, short atrial and ventricular refractory periods were documented in all and increased ventricular vulnerability to fibrillation in 3 of 4 patients. Conclusions-The short QT syndrome is characterized by familial sudden death, short refractory periods, and inducible ventricular fibrillation. It is important to recognize this ECG pattern because it is related to a high risk of sudden death in young, otherwise healthy subjects.

New echocardiographic insights in short QT syndrome: More than a channelopathy?

“…Short QT syndrome (SQTS) is a primary cardiac electrical disease caused by autosomal dominant gain-of-function mutations in genes encoding for potassium channels, resulting in a substantial shortening of QT interval, [1][2][3][4] which predisposes to life-threatening arrhythmias. Left ventricular (LV) function has been assumed to be normal in SQTS patients and echocardiography has traditionally been performed only to exclude an additional heart disease.…”

Cellular basis for arrhythmogenesis in an experimental model of the SQT1 form of the short QT syndrome

“…Polymorphic ventricular tachycardia (pVT) is readily inducible in a large fraction of affected individuals. 3,10 Due to the unavailability of I Kr , I Ks or I K1 agonists, the only previously developed models of short QT syndrome were ones in which the activator of the ATP-sensitive potassium current (I K-ATP ), pinacidil, was used to augment outward current in canine left ventricular wedge preparations 11 or Langendorff-perfused rabbit hearts. 12 The present study involves the development and characterization of a specific model of SQT1 made possible by the recent availability of a selective I Kr agonist, PD-118057.…”

Shortening of the Short Refractory Periods in Short QT Syndrome

“…Ventricular RP were short (145±13 ms) and prolonged after quinidine treatment to 220±22 ms 18. Ventricular RP had also been measured during standard electrophysiological study in 2 of these patients with SQTS and did not exceed 150 ms at any pacing site or pacing cycle length 7. More recently, in the European registry, 28 patients had undergone electrophysiological study, and ventricular RP varied between 140 and 200 ms (mean 166±21) and were correlated to HERG mutations (151±14 with versus 176±24 ms, P =0.01) but not to clinical events 5.…”

“…A diagnostic value of 300 ms,1, 7 then of 320 ms8 for the QT interval and of 340 ms for the corrected QT (QTc)9 had been initially proposed, although some symptomatic patients with SQTS may present with longer QTc interval 4, 10, 11, 12. A diagnostic score was proposed in 2011, including QTc value, and clinical and family history, demonstrating excellent sensitivity,4 although this score has not gained wide acceptance because of some limitations 13, 14.…”

“…Thus, a more reliable repolarization parameter, with less inter/intraobserver variability and less dependence on the heart rate—or showing different rate dependence—would be very useful for SQTS diagnosis. Earlier works had shown some shortening of ventricular and atrial refractory periods (RP) in patients with SQTS 7, 18. Even if short ventricular RP are common in SQTS, their additional shortening after short cycle lengths has not been evaluated.…”