20-year-old asymptomatic young female presented significant bradycardia and ectopiс atrial activity including locked SVEs. Pharmacological test with atropine was assessed as positive due to marked increase HR (sinus P) from 45 to 90 bpm. However, at the same time it was to induce worsening AV conduction (from the first to third degree AV block). What is your opinion about these ECGs (surface and transesophageal)?
Dear Tatiyana,
Thank yoy very much for interesting and difficult question! I may be wrong but I see on the first strip significant bradycardia and 1st degree AV-block (PR interval varies 0.24-0.28') with no dropped QRS complexes. Heart rate is appr. 40-47 bpm. It seems the positive P wave presents in II lead.
After administration of atropine we can see increase in HR (up to 60-83 bpm) on the second picture. There are increase in as SA pace activity according to shortening PP interval (0.8", 0.6", 0.6", 0,68", 0,72', etc. corresponding to atrial rate 60-75-83-88-100 per minute) and as ventricular rhythm (60-83 per minute) with atrioventricular dissociation (apparently seen in middle strips (V2) where are distinct P and QRS compexes which are not interrelated each other).
The most intriguing question: how atropine as vagolytic drug could exacerbate the AV conduction abnormality? It is known the atropine possesses various and paradoxal effects on conduction system. It was reported several cases when atropine caused paradoxically high-degree AV block in patients after cardiac transplantation (Brunner-La Rocca HP, 1997); unusual case of atrioventricular block occurring after administration of low-dose atropine during general anaesthesia (Chin KJ, 2005), etc. Variable effects of atropine in patients with AV blocks are attributable to different sites of pre-existing block. If atropine inhibits vagal tone thereby accelerating AV nodal conduction, then it has little effect on the infranodal conduction system encroaching on the refractory period and exacerbating the conduction delay. Chin et al. suggest that peripheral vagolytic effect of atropine would predominate at the SA node and increase atrial rate, and its central vagotonic effect at the AVN, resulting in conduction block.
The attached articles concern the matter.
http://www.ahjonline.com/article/0002-8703(80)90122-2/abstract
she has dual physiology, echo beats so needs slow pathway ablation
Dear Tatiyana Vaikhanskaya ,
I am not sure that this is high degree AV-block or just Weckenbach.
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