Which of the following statements regarding flecainide as a treatment of AFib is true?
It may contribute to an increase in the digoxin level. Flecainide (amiodarone, propafenone [Rythmol], and verapamil) can increase digoxin level. Flecainide can regularize and slow the atrial rhythm in patients with AFib and can, therefore, lead to increased ventricular response because of improved conduction of the atrial impulses through the AV node. It is, therefore, important to use an AV nodal blocking agent in patients with AFib treated with flecainide. It is used for AFib as well as flutter; however, it needs to be used with caution in atrial flutter patients, as it may slow the cycle length of the flutter circuit and result in more rapid conduction to the ventricle. There are no definite data on its safety in patients with hypertrophic cardiomyopathy. It is effective for acute conversion as well as maintenance of NSR postconversion.
Which of the following mechanisms is responsible for AFib occurring in the immediate postoperative period after a maze procedure?
Change in the atrial refractory period as a result of the surgical manipulation. The occurrence of AFib post-cardiac surgery is believed to be related to shortening of the refractory period of atrial tissue as it recovers from surgical manipulation, cardioplegia, and, potentially, ischemia. This nonuniformity of recovery results in reentry as the mechanism of AFib.
The following tachycardia was induced during EP testing of a 36-year-old woman with recurrent palpitations (Fig. below).
Which of the following is the most likely diagnosis?
AVNRT (Atrioventricular nodal reentrant tachycardia). This tracing shows AVNRT. It is a narrow complex tachycardia using the slow pathway of the AV node in the antegrade direction (long AH) and the fast pathway of the AV node in the retrograde direction (short HA). It is unlikely to be orthodromic reentrant tachycardia in which the retrograde limb of the circuit is an accessory pathway, because the QRS-A time is very short (atrium and ventricle are activated almost spontaneously), not long enough to involve ventricular activation as part of the circuit. Because the QRS is narrow, VT is not a likely diagnosis. Idiopathic LV-VT can sometimes be narrow but has an RBBB morphology on the surface ECG.
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