ECG Review

A Sensation in the Chest

By Ken Grauer, MD, Professor, Department of Community Health and Family Medicine, University of Florida Dr. Grauer is the sole proprietor of KG-EKG Press, and publisher of an ECG pocket brain book.

Figure. 12-lead ECG obtained from a 59-year-old man who was admitted to the hospital for chest discomfort.

Clinical Scenario: The ECG in the Figure was obtained from a 59-year old man with hypertension. He was admitted to the hospital to rule out acute infarction because of an "unpleasant sensation" in his chest. He was hemodynamically stable, and in no distress at the time this initial tracing was done. Comments?

Interpretation/Answer: There is a regular, narrow-complex tachycardia at a rate of approximately 150 beats/minute. Atrial activity seems to be present, although it is difficult to determine the nature of the atrial activity that is seen. No clear upright P wave is seen in lead II. This should make one suspect that the rhythm is not sinus tachycardia. After lead II, the next best lead to look at when assessing the nature of atrial activity is usually lead V1 (which anatomically lies just above the atria). Two little dots that we have drawn in this lead suggest that there is underlying atrial activity that occurs at a regular but very rapid rate.

It is helpful to keep in mind the differential diagnosis of a regular SVT (supraventricular tachycardia). Three entities make up over 90% of this differential: i) Sinus tachycardia; ii) Atrial flutter; and iii) PSVT (paroxysmal supraventricular tachycardia). Although other entities (such as junctional tachycardia) are possible, they occur much less often, especially when the heart rate exceeds 130/minute. In this particular case, sinus tachycardia is unlikely because no clear upright P wave is seen in lead II. Since the most common atrial rate of untreated flutter is 300/minute (250-350/minute range), atrial flutter with 2:1 AV conduction should always be suspected as a possible cause whenever a regular SVT is seen at a rate of close to 150/minute, especially in the absence of well defined P waves. In this case, application of a vagal maneuver slowed AV conduction enough to confirm the presence of underlying flutter activity at a rate of close to 300/minute. There is no ECG evidence on the tracing of acute infarction (and troponins were negative). The patient's chest pain resolved once he converted back to normal sinus rhythm.