Case B8. Third Degree AV Block with Acute Myocardial Infaction. St Emlyn’s ECG Library

stemlyns, ECG Library, #FOAMed, St. Emlyn’s ECG Library. Third Degree AV BlockHistory

The ECG was recorded from a patient bought to the hospital Accident and Emergency department following the onset of cardiac pain at rest.


Rhythm: The ECG shows P waves at a rate of 80 per minute. QRS complexes occur at a rate of 40 per minute. There is no relationship between the QRS complexes and the P waves. Complete heart block is therefore present. The ventricular escape rhythm is narrow complex and therefore arises above the bifurcation of the bundle of His. The rhythm strip shows failure of the escape rhythm with ventricular standstill resulting. Morphology: The raised ST segments typical of acute myocardial infarction are seen in leads II, III and aVF. The T waves are inverted or biphasic in the leads III, aVF and V5 and V6. There are Q waves in leads III, and aVF but these are less than .04 seconds in duration and in this tracing do not
provide evidence of actual infarction. The ST segment and T wave changes are compatible with early myocardial infarction.


This ECG shows why complete heart block is such a serious condition. The rhythm strip at the bottom of the trace shows the abrupt failure of the escape rhythm resulting in ventricular standstill. There is no effective cardiac output with this rhythm but fortunately before the padent lost consciousness the ECG technician told him to cough, and the escape rhythm returned immediately. Intravenous atropine was used as immediate treatment (although it did not have much effect as is often the case) and he received a temporary pacing system very shortly after this trace was recorded.


Cite this article as: Simon Carley, "Case B8. Third Degree AV Block with Acute Myocardial Infaction. St Emlyn’s ECG Library," in St.Emlyn's, November 3, 2018,

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