Which antiarrhythmic medication is contraindicated in patients with heart failure due to its negative inotropic effects?

Flecainide is contraindicated in patients with heart failure primarily due to its negative inotropic effects. Negative inotropic agents reduce the force of myocardial contraction, which can exacerbate heart failure symptoms and lead to worsening cardiac function. In patients with heart failure, maintaining an effective cardiac output is critical, and the use of flecainide in this context poses additional risks, including the potential for increased mortality.

On the other hand, medications like amiodarone and dofetilide, despite their potential side effects, can be used cautiously in heart failure patients because they do not significantly reduce myocardial contractility and may even be beneficial in controlling arrhythmias. Dronedarone, while similar to amiodarone, has restrictions in patients with more severe heart failure but is not as contraindicated as flecainide. Thus, the introduction of flecainide in this patient population is not advisable due to its detrimental impact on heart muscle performance.