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. 2017 May 8;33(6):562–567. doi: 10.1016/j.joa.2017.03.008

Fig. 4.

Fig. 4.

Continuous tracing shows an episode of paroxysmal AV block of uncertain mechanism in a patient with normal heart and normal ECG. In this patient, AV block occurred without P-P cycle changes, but PR interval was prolonged before block from 0.20 s to 0.28 s in the beat immediately preceding the asystolic pause; furthermore, the asystolic pause was followed by 2:1 AV block with prolonged PR interval up to 0.36 s in the conducted beats. PR prolongation is suggestive of vagal AV block (EI-AVB). Nevertheless, in this patient, AV block occurred without P-P cycle changes, which is suggestive of idiopathic AVB; the low adenosine value of 0.10 μmol/L (normal value: 0.40–0.80 μmol/L) observed in this patient supports this mechanism. AV=atrioventricular; ECG=electrocardiography.