The Bottom Line: Paroxysmal atrioventricular block is poorly defined, and is characterized by quick and unanticipated change from 1:1 atrioventricular conduction to complete heart block This leads to syncope and potentially sudden cardiac death. Although this is a dangerous condition due to unreliable escape mechanism, proper diagnosis of is often missed and overlooked because of its unfamiliarity and unpredictability
Lee, Sinjin Paroxysmal atrioventricular block. Heart rhythm 2009 vol:6 iss:8 pg:1229 -1234
Table 2 Comparison of vagal versus paroxysmal AVB page 1233
The Bottom Line: Although tachyarrythmias are primarily emphasized as etiologies for sudden cardiac death (SCD) and syncope, sinus node dysfunction, and cardiac conduction abnormality still account for more than half of arrythmic syncope.
Lee S, Wellens HJ, Josephson MEParoxysmal AV Block (PAVB). Heart Rhythm 2009; 6:1229.
PAVB can result from sinus rate slowing (prolonged P-P), post-extrasystolic pauses (VPC, PAC, JPC), or tachycardia. Our case was post-PVC. It is crucial to differentiate PAVB from Vagal AVB, please refer to Table 2 in the article. The former is critical, while the latter is benign. PAVB is an infranodal disease (mostly within the Hiss-Purkinjee System (HPS), while Vagal AVB is a disease of the AVN.