Characteristics of syncope in patients with dilated cardiomyopathy

Syncope carries a poor prognosis among patients with dilated cardiomyopathy (DCM).

To assess the prevalence, describe the underlying mechanisms and to identify risk factors for syncope in patients with DCM.

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.

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).

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.