ECG Strips

ECG 26-1

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

Rate: About 180 BPM	PR intervals: None
Regularity: Regular	QRS width: Normal
P waves: Present Morphology: Inverted Axis: None	Grouping: None
	Dropped beats: Absent
P:QRS ratio: 1:1	Rhythm: AV reentry tachycardia

Discussion:

ECG 26-1 shows a classic example of orthodromic AVRT. Note the narrow-complex tachycardia with an inverted P wave buried in the middle of the depressed ST segment. For your reference, an example of the inverted P waves is labeled with a blue arrow. The baseline of the rhythm strip is a bit wavy, adding to a variation in the QRS morphology, which is artifactual in beats 9 through 11.

 

 

ECG 26-2

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

Rate: About 150 BPM	PR intervals: None
Regularity: Regular	QRS width: Wide
P waves: None Morphology: None Axis: None	Grouping: None
	Dropped beats: Absent
P:QRS ratio: None	Rhythm: AV reentry tachycardia

Discussion:

ECG 26-2 is not so obvious for an antidromic AVRT. All we know is that this is a wide-complex tachycardia. As such, it should be treated primarily as a ventricular tachycardia. Luckily, this patient was stable enough to obtain a full 12-lead ECG, which clearly demonstrated inverted P waves with a prolonged RP interval consistent with an antidromic AVRT. After breaking the tachycardia, the patient demonstrated a WPW pattern on the ECG, confirming our initial suspicion that we were dealing with an antidromic AVRT.

 

 

ECG 26-3

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

Rate: About 230 BPM	PR intervals: None
Regularity: Regular	QRS width: Normal
P waves: None Morphology: None Axis: None	Grouping: None
	Dropped beats: Absent
P:QRS ratio: None	Rhythm: AV reentry tachycardia

Discussion:

ECG 26-3 is a very rapid narrow-complex tachycardia. The differential diagnosis includes AVNRT and AVRT. It is almost impossible on this rhythm strip to determine the correct diagnosis. The only thing that makes AVRT more likely is the very rapid rate, which is slightly more consistent with this diagnosis. The patient was treated and responded to therapy appropriately. An ECG obtained in normal sinus rhythm demonstrated a WPW pattern, confirming the diagnosis of an orthodromic AVRT.

 

 

ECG 26-4

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

Rate: About 235 BPM	PR intervals: None
Regularity: Regular	QRS width: Wide
P waves: See discussion below Morphology: See discussion below Axis: See discussion below	Grouping: None
	Dropped beats: Absent
P:QRS ratio: See discussion below	Rhythm: AV reentry tachycardia

Discussion:

In ECG 26-4, this wide-complex tachycardia is very rapid and very regular. There was a consistent notching noted on the upstroke of the ST segment, which was suggestive of an inverted P wave. The very rapid rate, wide complexes, and possibly the inverted P waves all led to the diagnosis of antidromic AVRT. Ventricular tachycardias are usually not this rapid, but can occur. Luckily, the patient had a history of WPW syndrome and antidromic conduction, facilitating the diagnosis. Always remember to interpret a rhythm abnormality based on the company it keeps and the full clinical scenario.

 

 

ECG 26-5

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

Rate: About 215 BPM	PR intervals: None
Regularity: Regular	QRS width: Normal
P waves: None Morphology: None Axis: None	Grouping: None
	Dropped beats: None
P:QRS ratio: None	Rhythm: AV reentry tachycardia

Discussion:

ECG 26-5 is a really great example of a wide-complex tachycardia. Your first thought should be ventricular tachycardia. The patient should be treated as ventricular tachycardia first and foremost. Electrical cardioversion would be indicated if the patient were hemodynamically unstable. A couple of things should make you take a second look at the strip, the most important of which is the rate. This strip has an underlying rate at 215 BPM, which is rapid for a ventricular tachycardia. After breaking the tachycardia, the patient was found to have a WPW pattern on the ECG. This is an example of antidromic AVRT.

Additional Information

Differential Diagnosis of AVRT

The exact diagnosis is not always clear when first approaching any tachycardia, either narrow-complex or wide-complex. For that reason, we have included separate chapters on the differential diagnoses of each of these two complex subjects. We strongly suggest that you review these chapters thoroughly before completing this text.

As far as AVRT is concerned, it is not essential for you to remember the terms antidromic and orthodromic. It is, however, vitally important that you are able to recognize the rhythm or at least to raise the possibility of these rhythms in your mind. In AVRT, thinking about the possibility is critical because of the consequences of pharmacologic therapy. This is one rhythm abnormality that could quickly deteriorate to a worse one because of the choice of an inappropriate agent.