Answer to a Quiz: Electrocardiogram  on page 163 and case discussion

Mykhaylo S. Sorokivskyy, Ulyana P. Chernyaha-Royko

doi:10.24969/hvt.2019.162

QUIZ

Answer to a Quiz: Electrocardiogram on page 163 and case discussion

Article Summary

DOI: 10.24969/hvt.2019.162
Page(s): 169-170
Electrocardiography

Published: 16/10/2019
Received: 14/10/2019
Accepted: 15/10/2019

Views: 5241
Downloads: 4830

Keywords: quiz, electrocardiogram, advanced atrioventricular block

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Correct answer: E – Atrioventricular (AV) block II degree, advanced

The main characteristic of the first-degree AV block is that all P waves are conducted via AV node to ventricles, but with some delay and interval PQ is prolonged - more than 200 ms (Fig. 1).

Figure 1. AV block I degree

The second degree of AV block with Wenckebach phenomenon can be recognized with gradual prolongation of PQ interval and fallout of one QRS complex, which is blocked in AV node. PQ interval observed after the blocked QRS is shorter comparatively to next ones. Then PQ interval progressively increases (Fig 2). The rate of P waves and QRS complexes can be 6:5, 5:4, 4:3 etc.

Figure 2. AV block II degree with Wenckebach phenomenon

The main feature of the second degree of AV block Mobitz type is that drop of the QRS complex appears without segment PQ prolongation (Fig.3).

Figure 3. AV block II degree, Mobitz type

AV block II degree, 2:1 can be registered on ECG, when the rate of P waves and QRS complexes is 2:1, but there is no possibility to obtain how it appears. AV conduction with the Wenckebach phenomenon rate can gradually decrease to 2:1 rate or AV block 2:1 can occur according to the Mobitz type (Fig.4).

Figure 4. AV block II degree, 2:1

Complete AV block is characterized by complete absence of the P waves and the QRS complexes accordance. Any signs of atrioventricular conduction cannot be revealed on ECG. QRS complexes narrow or wide appear with own very often slow rhythm (Fig.5).

Figure 5. AV block III degree, complete

Advanced AV block II is shown on Figure 7 (Fig. 1 on page 163) and is recognized by rare episodic signs of the AV conduction. Only 5^th and 8^th QRS complexes (Fig.7) are conducted via AV node. There is no accordance between P waves and other QRS complexes on this ECG. AV conduction is severely disturbed in this case and only single conducted P waves suggest that AV block is not complete.