Arrhythmia Recognition: The Art of Interpretation

A rhythm strip from lead 2 shows sharp peaks of the QRS complexes between the subtle dips of the P and T waves. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 75 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
P waves: Present Morphology: Inverted Axis: Abnormal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Ectopic atrial rhythm

Discussion:

ECG 14-1 is a typical example of ectopic atrial rhythm. First, let’s look at the rate. In this case it is about 75 BPM. Next, look at the P-wave morphology. In this case, it is easy to see that the P waves are inverted in lead II, which is grossly abnormal. The inverted P waves rule out the possibility of a normal sinus rhythm. Since inverted P waves can be seen in both junctional rhythms and ectopic atrial rhythms, we have a decision to make. To help us with this decision, we look at the PR interval. In this case, the PR interval is within the normal range, making the diagnosis of ectopic atrial rhythm likely.

ECG 14-2

A rhythm strip from lead 2 shows a curved dip of the P wave, a sharp peak of the QRS complex, and a wide peak of the T wave. The complexes occur at regular intervals. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 80 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
P waves: Present Morphology: Inverted Axis: Abnormal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Ectopic atrial rhythm

Discussion:

ECG 14-2 is also a good example of an ectopic atrial rhythm. Following the same logic as above, the inverted P waves and the normal PR intervals clinch the diagnosis. Should you get a regular 12-lead ECG on this patient? Yes, you should because of the presence of a rhythm abnormality and the ST-segment elevation. Remember, it is better to be safe than sorry!

ECG 14-3

A rhythm strip from lead 2 shows a subtle and curved dip of the P wave, a tall, sharp peak of the QRS complex, and a wide, curved peak of the T wave. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 50 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
P waves: Present Morphology: Inverted Axis: Abnormal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Ectopic atrial rhythm

Discussion:

ECG 14-3 poses more problems than the previous ones. Why? Because the rate is so slow. It is about 50–55 BPM. This rate could very easily fit with a junctional rhythm, which is usually about this range. Once again, our saving grace is the presence of a normal PR interval. The normal PR interval makes the diagnosis of ectopic atrial rhythm more likely. Medications can often cause a significant bradycardia, and you should evaluate this and other possibilities as well for your patient.

ECG 14-4

A rhythm strip from lead 2 shows a subtle and curved dip of the P wave, a sharp peak of the R wave, a sharp dip of the S wave, and a subtle, wide, and curved dip of the T wave. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 75 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
P waves: Present Morphology: Inverted Axis: Abnormal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Ectopic atrial rhythm

Discussion:

The inverted P waves and the normal PR interval make the diagnosis in ECG 14-4. By now, you should be feeling a bit more comfortable with the possibility of an ectopic atrial rhythm. Remember, however, to always try to obtain an old ECG to verify your suspicions and confirm your diagnosis.

ECG 14-5

A rhythm strip from lead 2 shows a curved dip of the P wave and a sharp peak of the QRS complex, followed by mild fluctuations. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 85 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
P waves: Present Morphology: Inverted Axis: Abnormal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Ectopic atrial rhythm

Discussion:

ECG 14-5 is a bit troubling because the QRS complexes appear to be wider. But are they? Using your calipers and some careful measuring, you will note that the QRS complexes are not wider than 0.12 seconds. Therefore, the inverted P waves, normal PR interval, and normal QRS complexes make the diagnosis of ectopic atrial rhythm the correct diagnosis. Comparison to an old ECG or rhythm strip would be, as always, very helpful in confirming your suspicions.

Now, suppose that the QRS complexes were wider than 0.12 seconds. What should you do differently if that were the case? The first thing to check is whether the patient had a bundle branch block of some sort in the past. The next possibility would be aberrancy in the conduction of the impulse to or through the ventricles. The aberrancy could be rate related, and a long rhythm strip may show the aberrancy coming and going as the patient’s heart rate changes. The aberrancy can also be caused by ischemia or a diseased portion of the conduction system, which causes longer refractory periods in that area. Electrolyte imbalances can often cause aberrancy or rhythm abnormalities to develop. After you have exhausted these possibilities, there could be some other rhythms that can cause a similar picture, but that is for later on in the book.