Flecainide increased mortality from

Class IC antiarrhythmic drugs such as flecainide or propafenone block the Na+ channel (open state propafenone open and inactivated state) with a very long dissociation time constant so that they alter normal action potential propagation. Flecainide increased mortality of patients recovering from myocardial infarction due to its proarrhythmic effects (CAST study). Action potential is shortened in Purkinje fibres but is prolonged in the ventricles. 

The effects of flecainide (Tambocor) therapy are thought to be attributable to the drug s very long Xrecovery from Na+ channel block, flecainide increased mortality in patients... 

Flecainide produces few subjective complaints in most patients dose-related blurred vision is the most common noncardiac adverse effect. It can exacerbate CHF in patients with depressed left-ventricular performance. The most serious adverse effects are provocation or exacerbation of potentially lethal arrhythmias. These include acceleration of ventricular rate in patients with atrial flutter, increased frequency of episodes of reentrant ventricular tachycardia, and increased mortality in patients convalescing from myocardial infarction. 

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