Marked PR interval variability in a patient with Brugada syndrome.

The authors present a clinical case of a 54-year-old woman without relevant medical history other than Brugada type 1 pattern in the electrocardiogram, without chronic medica-tion, who was referred for the cardiology outpatient clinic with palpitations. She had a strong family history of Brugada syndrome, but no history of sudden death, and she never had syncope. A transthoracic echocardiogram was performed, ruling out structural heart disease. Blood samples were analyzed, without thyroid function or electrolyte abnormalities. A 24-hour Holter examination was performed (digital Philips Zymed Holter, Model 1810 Plus Software, Philips Medical Systems) that revealed nocturnal periods of first-degree atrio-ventricular block (AVB) with a markedly variable PR interval and without nonconducted P waves; no other abnormalities were seen; the patient was asymptomatic. The P wave and QRS morphology were the same throughout the examination. The PR interval either increased or decreased, but it was always followed by a QRS complex. The number of P waves was the same as the QRS complexes. There was no relation between the PR interval variability and heart rate or circadian predomi-nance. The patient is kept under follow-up in the outpatient clinic, uneventful. No genetic test was performed. First-degree AVB is typically a benign situation 1 ; however, it is associated with increased incidence of atrial fibrillation, heart failure, and mortality during follow-up. 2 In some clinical settings, it can even be associated with markedly decreased survival. 3 Some data point out that first-degree AVB on a basal ECG is an independent predictor of malignant arrhythmic events in Brugada syndrome