Trace 1.5: Atrial flutter and AV-conduction problems

Patient information

78-year-old man with arterial hypertension and fatigue

ECG

Question

Which answer(s) is(are) true regarding the diagnosis(es) on this ECG upon entry in the cardiology department?

Comments

ECG description

This tracing shows a bradycardia with a ventricular rate of 40 bpm; common atrial flutter pattern (sawtooth in inferior leads, positive atrial activity in V1 and negative in V6); incomplete right bundle branch block; the QRS complexes are slow and regular corresponding to an altered atrioventricular conduction (absence of fixed ratio between atrial and ventricular activities);

Explanation

–

Trace description

This patient underwent an ablation of the cavo-tricuspid isthmus; the next tracing was recorded after the ablation procedure.

Question

What do we see on the second ECG?

A. left bundle branch block

B. right bundle branch block + left anterior hemiblock

C. thirddegree AV-block

D. second degree AV block type Mobitz 2

E. second degree AV block type Mobitz 1

Correct answer: E. Atrial sinus activity and second-degree AV block with Wenckebach periodicity;

Commentaires

This patient presented an atrial flutter and a high-grade atrioventricular conduction disorder, which is characterized by a slow ventricular rate and a lack of direct relationship between atrial activities and ventricular activities. The highlighting of a second-degree AV block after return to sinus rhythm confirms the presence of this likely junctional conduction disorder (Wenckebach periods with a significant increment in PR interval suggesting a nodal block). This patient was not under any treatment aimed at slowing atrioventricular conduction. The electrical pattern evolved toward an escalation of the conduction disorder with 2:1 atrioventricular rhythm and symptomatic bradycardia of 30 beats/minute. The patient therefore underwent implantation of a dual-chamber pacemaker.

To remember

A second-degree AV block type 1 corresponds in the majority of instances to a conduction disorder located in the atrioventricular node and to an exaggeration of decremental conduction. This location explains the predominantly normal morphology of the QRS complexes. Electrophysiological study hence reveals a gradual prolongation of the AH interval, followed by a blocked atrial activity but not followed by a His potential (supra-Hisian block).

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