Marked First Degree Atrioventricular Block: an extremely prolonged PR interval associated with Atrioventricular Dissociation in a young Nigerian man with Pseudo-Pacemaker Syndrome: a case report

BACKGROUND: The diagnosis of Marked First Degree Atrioventricular Block is made with electrocardiogram when PR interval ≥0.30 s. A PR interval of up to 0.48 s had been reported in literature. Data is sparse on an extremely prolonged PR interval associated with Atrioventricular Dissociation and Pseudo-Pacemaker Syndrome. Electrocardiogram with this type of uncommon features poses diagnostic and management challenges in clinical practice. CASE PRESENTATION: We report a case of a 22 year old Nigerian male from Igbo ethnic group who presented himself for medical screening with a history of exercise intolerance, occasional palpitation and fainting spells. He has no history of cough, orthopnoea, paroxysmal nocturnal dyspnoea nor body swelling. A physical examination revealed that the patient has a pulse rate of 64 beats per minute, blood pressure of 110/70 mmHg and soft heart sounds. Standard 12-lead electrocardiogram showed an uncommon Marked First Degree Atrioventricular Block with an extremely prolonged PR interval of 0.56 s. Long rhythm strips of the electrocardiogram showed extremely prolonged PR interval associated with Atrioventricular Dissociation and variable degrees of Atrioventricular Block (Mobitz type I and II). CONCLUSIONS: An extremely prolonged PR interval may occur in First Degree Atrioventricular Block and it may be associated with Atrioventricular Dissociation and Pseudo-Pacemaker Syndrome which may pose diagnostic and management challenges. This suggests that not all cases of First Degree Atrioventricular Block are benign and so should be sub-classified based on degree of PR interval prolongation and associated electrical abnormalities.