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Digoxin and AF
AF is a common arrhythmia in which irregular electrical impulses are conducted through the heart. These irregular electrical impulses lead to uncoordinated and inefficient heart contractions. As a result, blood pools in the heart, increasing the likelihood of a blood clot, which may lead to serious consequences such as myocardial infarction or stroke. AF can be managed by utilizing either rate or rhythm control agents. Digoxin exhibits its benefit in AF by controlling the heart rate.
One multicenter, randomized, double-blind, crossover trial evaluated the benefit of digoxin versus placebo in 43 patients with paroxysmal AF. Patients were aged ≥18 years and had one or more symptomatic episodes of self-terminating AF per month. The study endpoint was time to occurrence of one or two AF episodes as documented by patient-activated monitors. The median time to two episodes was 13.5 days for placebo and 18.7 days for digoxin (P <.05). The median time to one episode was 3.5 days for placebo, compared with 5.4 days for digoxin (P <.05). Mean ventricular rates during an AF episode were 138 ± 32 beats per minute (bpm) and 125 ± 35 bpm on placebo and digoxin, respectively (P <.01). It was concluded that digoxin reduced the frequency of symptomatic AF episodes and that the effect, although small, may be due to a reduction in ventricular rate rather than an antiarrhythmic action.
A recent retrospective cohort study of 122,465 newly diagnosed AF patients (mean age 72 years) found a higher cumulative mortality rate in those treated with digoxin than in those who were untreated (P <.001). Digoxin treatment was an independent predictor of mortality despite confounders such as age, kidney function, drug adherence, and history of cardiovascular complications. The impact of digoxin on mortality in AF patients needs further investigation.
According to the ACCF/AHA guideline, clinical results with regard to symptoms are similar whether AF is managed by rate control or rhythm control. Although symptom relief is comparable with both methods, rhythm-control therapy confers increased exercise tolerance. Digoxin is one of the medications used to manage heart rate, which is considered controlled when the ventricular response is 60 to 80 bpm at rest and 90 to 115 bpm during moderate exercise. First-line therapies for rate control include diltiazem, verapamil, esmolol, and other beta-blockers. Compared with digoxin, these medications have stronger recommendations and better evidence. Digoxin is not considered first-line therapy, owing to its narrow therapeutic index (which requires monitoring) and numerous drug interactions. Patients at higher risk for digoxin toxicity (i.e., renal impairment, elderly, multiple drug interactions) should be monitored more frequently than healthy, young patients with no comorbidities or concomitant medications.
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