Supraventricular tachycardia differential diagnosis
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Supraventricular tachycardia Microchapters |
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Differentiating Among the Different Types of Supraventricular Tachycardia |
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Differentiating Supraventricular Tachycardia from Ventricular Tachycardia |
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Diagnosis |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Differentiating Among the Different Types of Supraventricular Tachycardia
The individual subtypes of SVT can be distinguished from each other by certain physiological and electrical characteristics, many of which present in the patient's EKG.
Supraventricular tachycardias must be differentiated from each other because the management strategies may vary:
Atrial Fibrillation
- Rate: 110 to 180 bpm
- Rhythm: Irregularly irregular
- P waves: Absent, fibrillatory waves
- PR interval: Absent
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology in the absence of aberrant conduction
- Response to Maneuvers: Does not break with adenosine or vagal maneuvers
- Epidemiology and Demographics: More common in the elderly, following bypass surgery, in mitral valve disease, hyperthyroidism
Atrial Flutter
- Rate: 75 (4:1 block), 100 (3:1 block) and 150 (2:1 block) bpm, but 150 is more common
- Rhythm: Regular
- P waves: Sawtooth pattern of P waves at 250 to 350 beats per minute
- PR interval: Varies depending upon the magnitude of the block, but is short
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
- Response to Maneuvers: Conduction may vary in response to drugs and maneuvers dropping the rate from 150 to 100 or to 75 bpm
- Epidemiology and Demographics: More common in the elderly, after alcohol
AV Nodal Reentry Tachycardia (AVNRT)
- Rate: In adults the range is 140-250 bpm, but in children the rate can exceed 250 bpm.
- Rhythm: Regular
- P waves: The P wave is usually superimposed on or buried within the QRS complex
- PR interval: The PR interval cannot be calculated as the P wave is generally obscured by the QRS complex. In uncommon AVNRT, the P wave can appear after the QRS complex and before the T wave, and in atypical AVNRT, the P wave can appear just before the QRS complex.
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology in the absence of aberrant conduction, QRS alternans may be present
- Response to Maneuvers: May break with adenosine or vagal maneuvers
- Epidemiology and Demographics: Accounts for 60%-70% of all SVTs. 80% to 90% of cases are due to antegrade conduction down a slow pathway and retrograde up a fast pathway.
AV Reciprocating Tachycardia (AVRT)
- Rate: More rapid than AVNRT
- Rhythm: Regular
- P waves: Due to retrograde conduction a retrograde P wave is seen either at the end of the QRS complex or at the beginning of the ST segment.
- PR interval: Less than 0.12 seconds
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
- Response to Maneuvers: May break with adenosine or vagal maneuvers
- Epidemiology and Demographics: More common in males, whereas AVNRT is more common in females, occurs at a younger age.
- Pathophysiology:Atrioventricular reentrant tachycardia (AVRT) also results from a reentry circuit, although one physically much larger than AVNRT. One portion of the circuit is usually the AV node, and the other, an abnormal accessory pathway from the atria to the ventricle. Wolff-Parkinson-White syndrome is a relatively common abnormality with an accessory pathway, the Bundle of Kent crossing the A-V valvular ring.
- In orthodromic AVRT, atrial impulses are conducted down through the AV node and retrogradely re-enter the atrium via the accessory pathway. A distinguishing characteristic of orthodromic AVRT can therefore be a P wave that follows each of its regular, narrow QRS complexes, due to retrograde conduction.
- In antidromic AVRT, atrial impulses are conducted down through the accessory pathway and re-enter the atrium retrogradely via the AV node. Because the accessory pathway initiates conduction in the ventricles outside of the bundle of His, the QRS complex in antidromic AVRT is often wider than usual, with a delta wave.
Inappropriate Sinus Tachycardia
- Rate: A resting sinus tachycardia is usually (but not always) present. The mean heart rate during 24 hrs of monitoring is > 95 beats per minute. A nocturnal reduction in heart rate is present. There is an inappropriate heart rate response on exertion.
- Rhythm: Regular
- P waves: Normal morphology and precede the QRS complex
- PR interval: Normal and < 0.20 seconds
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
- Response to Maneuvers: Does not break with adenosine or vagal maneuvers
- Epidemiology and Demographics: The disorder is uncommon. Most patients are in their late 20s to early 30s. More common in women.
- Pathophysiology: These patients have no apparent heart disease or other causes of sinus tachycardia. It is thought to be due to abnormal autonomic control.
Junctional Tachycardia
- Rate: > 60 beats per minute
- Rhythm: Regular
- P waves: Usually inverted, may be burried in the QRS complex
- PR interval: The P wave is usually buried in the QRS complex
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
- Response to Maneuvers: Does not break with adenosine or vagal maneuvers
- Epidemiology and Demographics: Common after heart surgery, digitalis toxicity, as an escape rhythm in AV block
Multifocal Atrial Tachycardia (MAT)
- Rate: Atrial rate is > 100 beats per minute (bpm)
- Rhythm: Irregular
- P waves: P waves of varying morphology from at least three different foci, absence of one dominant atrial pacemaker, can be mistaken for atrial fibrillation if the P waves are of low amplitude
- PR interval: Variable PR intervals, RR intervals, and PP intervals
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
- Response to Maneuvers: Does not terminate with adenosine or vagal maneuvers
- Epidemiology and Demographics: High incidence in the elderly and in those with COPD
Sinus Node Reentry Tachycardia
- Rate: 100 to 150 bpm
- Rhythm: Regular
- P waves: Upright P waves precede each regular, narrow QRS complex
- PR interval: Short PR interval
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
- Response to Maneuvers: Although it cannot be distinguished on the surface 12 lead EKG from sinus tachycardia, SA node reentry tachycardia does often terminate with vagal maneuvers unlike sinus tachycardia.
- Pathophysiology: Sinoatrial node reentrant tachycardia (SANRT) is caused by a reentry circuit localized to the SA node, resulting in a normal-morphology P wave that falls before a regular, narrow QRS complex.
Sinus Tachycardia
- Rate: Greater than 100
- Rhythm: Regular
- P waves: Upright, consistent, and normal in morphology (if no atrial disease)
- PR interval: Between 0.12–0.20 seconds and shortens with increasing heart rate
- QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
- Pathophysiology: Sinus tachycardia is considered "appropriate" when a reasonable stimulus such as fever, anemia, fright, stress, or physical activity, provokes the tachycardia. This is in distinction to "inappropriate" sinus tachycardia where no such stimulus exists.
Wolff-Parkinson-White syndrome
- Rate: Atrial rate is nearly 300 bpm and ventricular rate is at 150 bpm.
- Rhythm: Regular
- P waves: In WPW with orthodromic conduction due to a bypass tract, the P wave generally follows the QRS complex, whereas in AVNRT, the P wave is generally buried in the QRS complex.
- PR interval: Less than 0.12 seconds
- QRS complex: In WPW there is a delta wave and evidence of ventricular pre-excitation if there is conduction to the ventricle via ante-grade conduction down an accessory pathway. It should be noted, however, that in some patients with WPW, a delta wave and pre-excitation may not be present because bypass tracts do not conduct ante-grade.
- Response to Maneuvers: May break in response to procainamide, adenosine, vagal maneuvers
- Epidemiology and Demographics: Estimated prevalence of WPW syndrome is 100 - 300 per 100,000 in the entire world.
- Pathophysiology: Anatomically and functionally, the fast and slow pathways of AVNRT should not be confused with the accessory pathways that give rise to Wolff-Parkinson-White syndrome (WPW) syndrome or atrioventricular re-entrant tachycardia (AVRT). In AVNRT, the fast and slow pathways are located within the right atrium in close proximity to or within the AV node and exhibit electrophysiologic properties similar to AV nodal tissue. Accessory pathways that give rise to WPW syndrome and AVRT are located in the atrioventricular valvular rings, they provide a direct connection between the atria and ventricles, and have electrophysiologic properties similar to ventricular myocardium.