Characteristics of syncope in patients with dilated cardiomyopathy

BACKGROUND: Syncope carries a poor prognosis among patients with dilated cardiomyopathy (DCM). OBJECTIVES: To assess the prevalence, describe the underlying mechanisms and to identify risk factors for syncope in patients with DCM. METHODS: One thousand six hundred and ten medical files of 897 patients with a diagnosis of DCM were reviewed. Patients with syncope were identified and their clinical and paraclinical profiles were compared to an equal number of age- and sex-matched patients with DCM without syncope. RESULTS: Thirty patients (27 males) with an average age of 62.5 years were identified, corresponding to a prevalence of syncope of 3.3%. A cardiac origin of syncope was identified in 56% of patients (n = 17): ventricular arrhythmias in 33% (n = 10), and conduction disorders in 23% (n = 7). Other mechanisms of syncope were neurally mediated in 7% (n = 2) and orthostatic hypotension in 7% (n = 2). In 30% of cases (n = 9), the etiology was unidentified. There were no significant differences regarding the etiology of DCM, ejection fraction (35.3% vs 35.3%, p = 1.0), NYHA class (mild or advanced, p = 0.79) and associated conditions (hypertension, p = 0.36; diabetes, p = 0.75; atrial fibrillation, p = 0.43; and dyslipidemia, p = 0.33) between the two groups. However, among patients with syncope, patients with a noncardiac cause were more likely to have hypertension (61.53% vs 23.52%, p = 0.08) and diabetes (46.15% vs 5.88%, p = 0.03). CONCLUSION: In patients with DCM, syncope is a relatively rare finding. Cardiac causes (arrhythmias and conduction disorders) are responsible for the majority of cases. Risk factors for syncope in these patients remain to be determined.