Electrophysiological studies with the atrial extrastimulus technique suggested the presence of dual atrio vascular (AV) nodal pathways in a patient with hypothyroidism, as evidenced by a sudden increase of H1 H2 intervals at critical A1 A2 coupling intervals. Following the atrial extrastimulus (A2), a third impulse (A3) occurred spontaneously. During slow pathway conduction of A2, an A3 appearing at a critically timed interval allowed fast pathway conduction, resulting in an earlier than expected QRS (a form of supernormal conduction). This demonstration of fast pathway conduction during slow pathway conduction adds strong evidence for the existence of dual AV nodal pathways.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)