Polymorphic ventricular tachycardia, ischaemic ventricular fibrillation, and torsade de pointes: importance of the QT and the coupling interval in the differential diagnosis

Abstract

Aims Distinctive types of polymorphic ventricular tachycardia (VT) respond differently to different forms of therapy. We therefore performed the present study to define the electrocardiographic characteristics of different forms of polymorphic VT. Methods and results We studied 190 patients for whom the onset of 305 polymorphic VT events was available. The study group included 87 patients with coronary artery disease who had spontaneous polymorphic VT triggered by short-coupled extrasystoles in the absence of myocardial ischaemia. This group included 32 patients who had a long QT interval but nevertheless had their polymorphic VT triggered by ectopic beats with short coupling interval, a subcategory termed ‘pseudo-torsade de pointes] (TdP). For comparison, we included 50 patients who had ventricular fibrillation (VF) during acute myocardial infarction (‘ischaemic VF’ group) and 53 patients with drug-induced TdP (‘true TdP’ group). The QT of patients with pseudo-TdP was (by definition) longer than that of patients with polymorphic VT and normal QT (QTc 491.4 ± 25.2 ms vs. 447.3 ± 55.6 ms, P < 0.001). However, their QT was significantly shorter than that of patients with true TdP (QTc 564.6 ± 75.6 ms, P < 0.001). Importantly, the coupling interval of the ectopic beat triggering the arrhythmia was just as short during pseudo-TdP as during polymorphic VT with normal QT (359.1 ± 38.1 ms vs. 356.6 ± 39.4 ms, P = 0.467) but was much shorter than during true TdP (581.2 ± 95.3 ms, P < 0.001). Conclusions The coupling interval helps discriminate between polymorphic VT that occurs despite a long QT interval (pseudo-TdP) and polymorphic arrhythmias striking because of a long QT (true TdP).

Premature atrial contractions with multiple patterns of aberrant conduction followed by torsade de pointes in a patient with polymyalgia rheumatica

“…In these TdP events, the main mechanism underlying QT interval prolongation was likely I Kr blockade. [ 21 ] Furthermore, the coupling interval, defined as the interval between the first beat of TdP and the preceding sinus beat, was over 500 millisecond, suggesting “true” TdP related to QT interval prolongation [ 22 ] ; however, there were two initiation patterns of TdP events (Fig. 4 ).…”

Polymorphic Ventricular Tachycardia: Terminology, Mechanism, Diagnosis, and Emergency Therapy

“…The ECG of ischemic VF, as described 3 decades ago, 101 demonstrates 2 important characteristics: (1) polymorphic VT starts during maximal ST-segment elevation; higher cumulative ST-segment elevation correlates with a higher risk of VF; 105 and (2) ischemic VF is triggered by short-coupled ventricular extrasystoles. 101 In a recent study comparing ischemic VF to other forms of polymorphic VT, 18 the coupling interval of the triggering beat was shortest for ischemic VF. In fact, the ultrashort coupling interval during initiation of ischemic VF (305±53 ms) is comparable only to that of idiopathic VF (320±52 ms).…”

SOP Präklinisches Management von Breitkammerkomplextachykardien

“…Auch VTs werden häufig konvertiert, problematisch ist die im Vergleich zu Amiodaron ausgeprägtere negative Inotropie bei struktureller Herzerkrankung. [8].…”

“…Pathophysiologisch liegt keine akute Ischämie vor, und die polymorphe VT ist nicht durch die verlängerte QTc bedingt. Dies zeigt, wie wichtig die adäquate Dokumentation, insbesondere des Beginns der Arrhythmien, und die frühzeitige Einbindung eines Experten bei rezidivierenden VTs im Sinne eines "electric storms" sind [8].…”