11: Inherited: Case 1: Margaret
Margaret is a 65 year old lady with diabetes mellitus. She suffers from chronic urinary tract infections and her GP has prescribed trimethoprin. When Margaret collapsed at home, her daughter successfully performed cardiopulmonary resuscitation until paramedics arrived and re-established cardiac output. She was taken to the local Accident & Emergency Department, where ECG monitoring showed unsustained runs of polymorphic ventricular tachycardia (Torsades de Pointes) with prolonged QT intervals. On admission, Margaret's vital signs were: BP 93/72; HR 59bpm; and QTc514 on ECG.
Torsades de Pointes is a specific form of polymorphic ventricular tachycardia (PMVT), occurring in the context of QT prolongation and characterised by rapid QRS intervals. Prolongation of the QT interval can increase a person's risk of developing this abnormal rhythm. Torsades de Pointes is diagnosed when there is PMVT and QT prolongation together.