This is a good strip to demonstrate the change in the appearance of a T wave when a premature P wave occurs on the preceding T wave. The PACs found the atria ready to depolarize and produced a P wave that landed on top of the preceding T wave, making it appear taller than the others. The PACs also reset the sinus node, causing a slight delay before the next sinus discharge. The PACs occurred while the ventricles were still refractory, so no QRS complexes followed.
Dr. Jerry W. Jones, MD, FACEP, FAAEM has graciously shared with us his four-part article on the topic of “Delays & Blocks Involving the Bundle Branches”.
Dr. Jones is a talented instructor who makes difficult topics easy. Please feel free to post your comments and questions for Dr. Jones and our other ECG Gurus.
Click THIS LINK for a downloadable pdf of Part 1: Non-Specific Intraventricular Conduction Delays.
Click THIS LINK for a downloadable pdf of Part 2: Left Bundle Branch Block.
Click THIS LINK for a downloadable pdf of Part 3: Right Bundle Branch Block.
Click THIS LINK for a downloadable pdf of Part 4: The Fascicles of the Left Bundle Branch
This ECG is taken from an elderly man with heart failure.
The ECG The first feature that might capture your attention is the wider-than-normal QRS complex, which is 160 ms (.16 seconds). The rate is 58 bpm. We do not know the patient’s medications or baseline rate. There are P waves present, and so the rhythm is SINUS BRADYCARDIA. The P waves are broad , > 110 ms in Lead II (red lines in close up) and bifid, with greater than 40 ms between the two peaks in Lead II (blue lines). In V1, the P waves are biphasic, with the terminal negative portion greater than 40 ms duration (red lines). This meets the ECG criteria for LEFT ATRIAL ENLARGEMENT, or preferably, LEFT ATRIAL ABNORMALITY. (https://LITFL.com/left-atrial-enlargement-ecg-library/) ECG criteria are not highly accurate for detecting atrial enlargement, and abnormal findings should be confirmed by anatomic measurement. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2244611/).
The QRS complexes, as mentioned, are wide. Because there is sinus rhythm, we know the delay in conduction is due to interventricular conduction delay, and not to ventricular rhythm. This ECG meets the criteria for LEFT BUNDLE BRANCH BLOCK.
· Supraventricular rhythm
· Wide QRS (>.12 seconds)
Are you looking for a comprehensive ECG glossary that goes beyond simply defining words? Dr. Ken Grauer, who is the ECG Guru's Consulting Expert, has a Glossary available on his website that explains the terms. Instructors and students alike will benefit from having this glossary readily available. The glossary is exerpted from his e-Publication, "A 1st Book On ECGs - 2014", available on Amazon.
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