ECG Review: A Tachy Rhythm
ECG Review
A Tachy Rhythm
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.
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| Figure. 12-lead ECG and lead II rhythm strip obtained from a hospitalized, older adult with the sudden onset of palpitations and a heart rate of 210/minute. The patient was hemodynamically stable. |
Clinical Scenario: The ECG in the Figure was obtained from a hospitalized, older adult with the sudden onset of palpitations. No chest pain. Heart rate was 210/minute, and blood pressure was 150/90 at the time this tracing was obtained. What is your differential diagnosis? What might help you to be more sure of the diagnosis?
Interpretation/Answer: The rhythm is regular at a rate of 210/minute. The QRS complex appears to be widened. Although a low amplitude, upright deflection is seen just before the QRS complex in lead II, it is difficult to know at this rapid a rate if this upright deflection represents a P wave, T wave, or both. Thus, the rhythm is a regular WCT (wide-complex tachycardia), in which one is uncertain about the presence and nature of atrial activity.
Clinically, the first thing to do when confronted with any patient in a tachyarrhythmia is to assess hemodynamic stability. This is because immediate synchronized cardioversion would be indicated if the patient was hemodynamically unstable because of the rapid rate, regardless of the etiology of the arrhythmia. In the case of a regular WCT, the most common cause (by far) is ventricular tachycardia. This is true regardless of the patient's hemodynamic status. At times, selected patients may remain alert and hemodynamically stable for hours (if not days) despite remaining in persistent VT (ventricular tachycardia).
Less commonly, a regular WCT may be due to a SVT (supraventricular tachycardia), in which there is either preexisting bundle branch block or aberrant conduction. Because VT is so much more common than SVT as the cause of a regular WCT, and because VT is a potentially life-threatening arrhythmia, this diagnosis should always be assumed until proven otherwise.
As noted above, despite the tachycardia the patient in this case was hemodynamically stable. As a result, immediate cardioversion was not needed. Search of this patient's hospital chart revealed a prior baseline ECG at the time of admission to the hospital that showed sinus rhythm with QRS widening of identical morphology during sinus rhythm to that seen during the tachycardia. This strongly suggested a supraventricular etiology for the patient's tachycardia, and justified a trial of adenosine which successfully converted the rhythm. Had no prior ECG been available, one would have had to assume VT as the diagnosis. Since the patient was hemodynamically stable, IV amiodarone would have become the treatment of choice.
12-lead ECG and lead II rhythm strip obtained from a hospitalized, older adult with the sudden onset of palpitations and a heart rate of 210/minute.Subscribe Now for Access
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