Cardiac conduction defect seen with Tricyclic antidepressants are due to ?

Ans. is 'd' i.e., Both NE uptake inhibition and antimuscarinic action on hea The commonest cardiovascular effect of tricyclic antidepressant overdose is sinus tachycardia. Due to inhibition of norepincphrine reuptake and the anticholinergic action. However, the most impoant toxic effect of tricyclics is the slowing of depolarisation of the cardiac action potential by inhibition of the sodium current and this delays propagation of depolarisation through both myocardium and conducting tissue. This results in prolongation of the QRS complex and the PR/QT intervals with a predisposition to cardiac arrhythmias. This inhibition of sodium flux into myocardial cells can occur to such an extent that depressed contractility can result and this, coupled with the reduction in peripheral resistance, contributes to hypotension.