Postventricular Septal Defect Repair With Bradyarrhythmias and Sudden Death: Submitted by Berardo Sarubbi, MD, PhD

Case Synopsis

A.V., a 16-year-old male, was admitted to our cardiac tertiary center because of recurrent episodes of palpitations and recent episodes of “dizziness.”

At the age of 1 year, he underwent a surgical repair of a perimembranous ventricular septal defect with a Gore-Tex patch, which was complicated by transient (4 days) complete heart block. His preoperative ECG was completely normal, without conduction disturbances.

Two years later, sporadic asymptomatic episodes of type 1 and type 2 second-degree atrioventricular (AV) blocks were diagnosed ( Figs. 17.1 and 17.2 ).

At the age of 5 years, he was referred to our department for complete clinical and instrumental evaluation. A recent standard ECG showed asymptomatic episodes of 2:1 second-degree AV block associated with first-degree AV block (long PR interval 260 ms) and bifascicular block: complete right bundle branch block (QRS duration 160 ms) and left anterior hemi-block (frontal QRS axis—45 degrees) ( Fig. 17.3 ).

Physical examination revealed an asymptomatic young boy of average build who was in no apparent distress and had stable vital signs. Cardiac examination was not significant.

His echocardiogram showed no residual shunt, with normal left ventricular dimensions and function.

ECG Holter confirmed the presence of episodes of type 1 and type 2 second-degree AV blocks with a mean heart rate of 54 b/min (range 40 b/min to 82 b/min) and no pauses >2 s or significant ST/T abnormalities.

A treadmill stress test was stopped at the beginning of the second stage of the Bruce protocol owing to the lack of compliance by the patient.

An electrophysiological study was performed and showed normal sinus node function; normal supra-His conduction time (AH interval 76 ms); a considerable infra-His conduction delay (HV interval 170 ms), essentially located in the main His bundle fascicle, given that its potential preceded the right bundle one by a 150-ms interval and the right bundle deflection was anterogradely activated (20 ms) ( Fig. 17.4 ).

The validation of the His deflection was obtained both through atrial pacing and His bundle pacing. Spontaneous phases of infra-His type 1 second-degree AV block were found ( Fig. 17.5 ).

A prophylactic pacemaker was prescribed. Due to the absence of any symptoms, the parents refused the pacemaker implant and opted instead for strict follow-up.

Aged 14 years, the patient experienced frequent episodes of presyncope, without loss of consciousness. No pauses were documented on Holter monitoring.

Aged 15 years, he started to have recurrent episodes of palpitation and recurrent episodes of “dizziness.”

Aged 16 years, during hospitalization, telemetric electrocardiography monitoring showed repeated polymorphic ventricular tachycardia (VT) runs ( Fig. 17.6 ).