Why do Anti-Muscarinic agents QT prolongation and Torsas..???

[drayu]

I am a bit .... Ok to be true very confused .....why do anti-muscarinic agents cause prolongation of the QT interval and how does this increase in QT interval lead to ventricular tachycardia (Torsas de pointes).....????

Does anyone know why...???

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[loveoforganic2]

I'll let someone else answer the antimuscarinic question, but my understanding for QT prolongation leading to Torsades => VTach is that the prolonged QT interval allows additional opportunity for an independent ventricular depolarization and establishment of a re-entrant loop. Arrhythmias confuse me though, so someone may be able to explain better

 

[Zzmed]

Is it even an important concept tested on step 1?