Not just a Wenckebach, not yet a complete heart block

ECG manifestations of aortic valve Infective endocarditis are rare and typically consist of evidence of AV dysfunction - from 1st degree AV block to complete heart block. We present an interesting ECG in a gentleman with E faecalis bacteraemia, in the setting of aortic root abscess.

An 80-year-old male with a past medical history of a bioprosthetic valve and ascending aorta replacement presented to the hospital with generalized malaise, poor oral intake, febrile to 39 °C and dyspnoea. He grew Enterococcus faecalis in his blood cultures and imaging of his chest, abdomen and pelvis was unremarkable. His ECG demonstrated new onset Wenckebach physiology and subsequent transesophageal echocardiography revealed an aortic root abscess.

He was referred with an ECG of atrial bigeminy with 1st degree AV block, but upon closer review, there are several other key findings. Firstly, his ECG demonstrates Wenckebach physiology with a consistent PP interval of 560 ms. However, his ECG exhibits more than just Wenckebach in that the first QRS has a more aberrant appearance than the second one. We postulate this is due to Gap phenomenon where there are functional differences in conduction properties in proximal and distal components of the AV node and phase 4 conduction block where a period of nonconduction due to a blocked P wave results in a reduced responsiveness of Purkinje/bundle branch conducting tissues. Thus, the first QRS (130 ms) appears more aberrant than the second (100 ms). This case highlights the importance of identifying AV dysfunction in septic patients whilst demonstrating an interesting ECG and the importance of recognizing Wenckebach which may have a subtle appearance.