PQ segment depression in short QT syndrome: a novel diagnostic ECG marker

Abstract

Background: Although up to 30% of short QT syndrome (SQTS) patients suffer from atrial arrhythmias, less is known about atrial repolarization abnormalities. PQ segment depression (PQD) is a well defined ECG marker of acute pericarditis. PQD is related to atrial fibrillation and carries a poor prognosis in the setting of acute inferior myocardial infarction, and it has been rarely observed during ablation of the left upper pulmonary vein. Objective: The aim of this study was to evaluate the incidence of PQD in SQTS and to analyze the association between PQD and atrial arrhythmias. Methods: Digitalized resting 12-lead ECGs of SQTS patients were analyzed for PQD in all leads and for QT and Tpeak-Tend intervals in leads II and V5. PQD was defined as ≥ 0.05 mV (0.5 mm) depression from the isoelectric line. The QT and Tpeak-Tend intervals were measured by a standard tangential method in leads II and V5 and were corrected according to Bazett's formula. Results: 790 leads from 67 SQTS patients [mean age 36±18 years, 49 males (73%)] were analyzed (14 leads of three patients were missing). PQD was seen in 54 (80%) patients and in 276 (35%) leads and was more frequent in leads II, V3, V4, I, and aVF [n=45 (67%), n=31 (46%), n=26 (43%), n=26 (39%), n=28 (41%), respectively] and also more prominent in lead II. QTc (II), QTc (V5) and Tpeak-Tend (II), Tpeak-Tend (V5) intervals were not significanty different between patients with PQD in any lead and without PQD in any lead (321±34 ms, 324±29 ms, 70±11 ms, 70±14 ms; vs 323±25 ms, 320±28 ms, 64±11 ms, 66±12 ms; respectively, p=ns for all intervals). There was also no significant difference between patients with and without PQD in any inferior lead. Tpeak-Tend (II) intervals were significantly longer in patients with PQD in leads V1, V3, V4 and V5 (74±10 ms, 73±12 ms, 75±12 ms, 76±9 ms; vs 67±14 ms, 66±17 ms, 66±11 ms, 68±13 ms; respectively, p: <0,05 for all). Ten of 67 patients (15%) had atrial tachyarrhythmias and all 10 patients had PQD. Conclusions: 54 of 67 patients (80%) with SQTS reveal PQD. As this is not observed in healthy subjects, this ECG stigma constitutes a novel marker for SQTS in addition to a short QT interval.