PQ segment depression in patients with short QT syndrome: a novel marker for diagnosing short QT syndrome?

BACKGROUND: Patients with short QT syndrome (SQTS) have an increased risk for atrial tachyarrhythmias, ventricular tachyarrhythmias, and/or sudden cardiac death. PQ segment depression (PQD) is related to atrial fibrillation and carries a poor prognosis in the setting of acute inferior myocardial infarction and is a well-defined electrocardiographic (ECG) marker of acute pericarditis. OBJECTIVE: To evaluate the prevalence of PQD in SQTS and to analyze the association with atrial arrhythmias. METHODS: Digitalized 12-lead ECGs of SQTS patients were evaluated for PQD in all leads and for QT intervals in leads II and V5. PQD was defined as ≥0.05 mV (0.5 mm) depression from the isoelectric line. RESULTS: A total of 760 leads from 64 SQTS patients (mean age 36 ± 18 years; 48 [75%] men) were analyzed. PQD was seen in 265 (35%) leads from 52 (81%) patients and was more frequent in leads II, V3, aVF, V4, and I (n = 43 [67%], n = 30 [47%], n = 27 [42%], n = 25 [39%], and n = 25 [39%], respectively). Nine of 64 (14%) patients presented with atrial tachyarrhythmias, and all of them had PQD. CONCLUSION: Fifty-two of 64 (81%) patients with SQTS reveal PQD. As PQD is rarely observed in healthy individuals, this ECG stigma may constitute a novel marker for SQTS in addition to a short QT interval.