ECG Strips

ECG 15-1

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 135 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Focal atrial tachycardia

Discussion:

ECG 15-1 shows an inverted P wave in lead II in a patient with obvious tachycardia. These findings are consistent with focal AT. Note that the QRS complex is of normal duration and that there is some slight ST segment depression. The ST-depression is consistent with the presence of a tachycardia, but clinical correlation should be obtained to assure that ischemia is not the underlying cause of the tachycardia. Remember, acute myocardial infarction can cause a focal AT to develop in an adult patient.

 

 

ECG 15-2

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 140 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Wide
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Focal atrial tachycardia

Discussion:

The P waves in ECG 15-2 are difficult to spot. If you notice, at the end of the T wave there is a sudden drop-off and a small inverted segment. This is an inverted P wave buried in the T wave. It is especially visible in some of the complexes—for example, the last one. The regularity of the rhythm and the consistency of the inverted notch are indicative of a focal AT. Comparison with a normal sinus strip in this patient confirmed the P-wave morphology change present in this strip.

 

 

ECG 15-3

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 190 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Focal atrial tachycardia

Discussion:

ECG 15-3 is a very fast tachycardia! The rate is so fast that the P waves are almost lost in the T waves once again. These P waves, however, are biphasic. (It is a good idea to use a magnifying glass to evaluate these complexes.) This rapid rate is rare to find in a focal AT because, as the rate speeds up, the AV node usually causes some block to develop. As we shall see in the next chapter, rapid atrial rates that are blocked at the AV node to give you slower ventricular rates are more the norm in rapid focal AT.

 

 

ECG 15-4

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 155 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Focal atrial tachycardia

Discussion:

In ECG 15-4 the focal AT also shows a rapid rate at about 155 BPM. In this case, the P waves are inverted. The positive wave just prior to the P waves is a truncated T wave. As a side note, buried P waves become much more common as the rates of a tachycardia increase. An additional cause of buried P wave is the presence of a prolonged PR interval.

 

 

ECG 15-5

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 120 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Focal atrial tachycardia

Discussion:

ECG 15-5 shows a tachycardia with narrow-complex QRSs. There are no obvious P waves, but, on close examination, there is a small inverted notch at the end of the previous T waves. These are buried P waves. The PR intervals are normal.

 

 

ECG 15-6

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 115 BPM	PR intervals: Normal, consistent
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: Abnormal	Grouping: None
	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Focal atrial tachycardia

Discussion:

ECG 15-6 shows the onset of a focal AT. Note the P-wave morphology of the normal sinus beats at the start of the strip (green arrow). Then there is a PAC (pink arrow) that triggers off the tachycardia. Note that the ectopic P waves in the tachycardia (blue arrow) have the same morphology as the PAC. This is a common occurrence in focal AT that can help you to identify the rhythm, if you are lucky enough to capture the onset of the tachycardia on paper.