Background: In recent years cardioversion of atrial fibrillation has become a routine procedure, enabling symptomatic functional improvement in most cases. However, some patients develop complications after cardioversion. Identifying these individuals is an important step toward improving patient outcome.

Objectives: To characterize those patients who may not benefit from cardioversion or who may develop complications following cardioversion.

Methods: We retrospectively analyzed 186 episodes of cardioversion in 163 patients with atrial fibrillation who were admitted to our cardiology department between 2008 and 2013 based on their clinical and echocardiographic data. Patients were divided into two groups: those with uncomplicated cardioversion, and those who developed complications after cardioversion.

Results: Of the 186 episodes, cardioversion was done in 112 men (60%) and 74 women (40%), P < 0.00001. Complications after cardioversion occurred in 25 patients (13%). These patients were generally older (72 vs. 65 years, P < 0.01), were more often diabetic (52% vs. 27%, P = 0.005), had undergone emergency cardioversion (64% vs. 40%, P = 0.01), had left ventricular hypertrophy (left ventricular mass 260 vs. 218 g, P = 0.01), had larger left atrium (left atrial volume 128 vs. 102 ml, P < 0.009), and more often died from complications of cardioversion (48% vs. 16%). They had significant mitral regurgitation (20% vs. 4%, P = 0.03) and higher pulmonary artery pressure (50 vs. 42 mm Hg, P < 0.02).

Conclusions: People with complications after cardioversion tend to be older, are more often diabetic and more often have severe mitral regurgitation. In these patients, the decision to perform cardioversion should consider the possibility of complications.