Narrow-complex tachycardias can be very confusing to students of basic-level ECG. There are very many rhythms that fall into the broad category of narrow-complex tachycardia. We usually further divide them into sinus tachycardia and other "supraventricular tachycardias". The basic student will want to make this distinction, as well as be able to differentiate atrial fib and atrial flutter from the other SVTs. The more advanced student will want to go into more detail about which mechanism for supraventricular tachycardia is present.
Paroxysmal supraventricular tachycardia
This ECG is from a man in his 60's who is experiencing chest discomfort and palpitations. The onset of the rapid heart rate and the symptoms was sudden, while he was at rest. The rate did not slow when he was placed on oxygen, given IV fluids, and rested further
This series of ECG rhythm strips shows a paroxysmal supraventricular tachycardia successfully treated with adenosine. The patient was complaining of a rapid heart rate and palpitations, but was hemodynamically stable. It is not known whether any parasympathetic stimulation, such as a Valsalva maneuver or carotid sinus massage, was used initially.
This ECG shows AV nodal reentrant tachycardia in an elderly man. Clinical information is not available. AVNRT is the rhythm most often associated with the term, "supraventricular tachycardia".
This two-lead rhythm strip clearly shows the transition from normal sinus rhythm to a paroxysmal supraventricular rhythm. In this case, the arrhythmia is AV nodal reentrant tachycardia, AVNRT. The rate of the first rhythm, NSR, is around 75 per minute. The fourth beat on the strip is a PAC which initiates the paroxysm of tachycardia lasting 12 beats. The arrhythmia terminates spontaneously at that point. The tachycardia rate is about 150/min.
Today, you get THREE strips for your basic classes! The first shows a PSVT - paroxysmal supraventricular tachycardia at a rate of about 220/minute. The QRS complexes are narrow, and the rhythm is regular. In the second strip, we see the moment of conversion after a dose of 6 mg. of adenosine was administered by rapid I.V. infusion. The re-entry cycle is broken, and the patient experiences many PVCs, including groups of two, three, and even four in a row. Soon, however, the rhythm settles into sinus rhythm with PACs, and later, just sinus rhythm (not shown).
This strip is from a patient who experienced a sudden onset of palpitations and rapid pulse while at rest. It shows a narrow-complex tachycardia, specifically a paroxysmal supraventricular tachycardia. The subject of supraventricular tachycardias is a fascinating one, and is covered extensively throughout this website. The mechanisms of SVT are many, and can be complex for the beginning student to understand. Search the search terms on the left side of the page for entries from ASK the EXPERT and JASON's BLOG for more advanced information about SVT.
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