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SUPRAVENTRICULAR ARRHYTHMIAS AND TACHYCARDIAS

Supraventricular arrhythmias, including tachycardia, flutter, and fibrillation, originate above the ventricles [SUPRA- + VENTRICULAR.]

 

Atrial Tachycardia (AT)—150-250 bpm

ATRIAL (ECTOPIC) TACHYCARDIA is a supraventricular tachycardia (tachycardia originating above the ventricles) in which the rapidity of autonomic ectopic pacemaker(s) overrides the depolarizations of the AV node and below. A rapid atrial rate that overrides the SA node becomes the dominant pacemaker. As such, it does not require the atrioventricular (AV) junction, accessory pathways, or ventricular tissue for its initiation and maintenance.

The heart rate in AT is typically between 150-250 beats per minute and is often characterized by narrow-complex QRS in a regular rhythm; the P waves often indistinguishable.

A "REGULAR" rate that is high with P-wave abnormalities is most likely to be an atrial tachycardia (flutter or reentrant). (A-fib is irregularly irregular, and the rate is too fast--150-250--for sinus tach or v-tach.) Notched P waves are a big clue if you see this on the test. "Notched" P waves are "bifid," and indicate left-vs-right atrial differences in anatomy (dilatation or hypertrophy). 

CHARACTERISTICS

  • Rate: 150 - 250 bpm.
  • Rhythm: Regular.
  • P Waves: Upright and Uniform; differ in shape from sinus P waves.
  • PR Interval: May be short in rapid rates < 0.12.
  • QRS: 0.06 - 0.10 (can be aberrant).

 

Multifocal Atrial Tachycardia (MAT)— > 100 bpm

MULTIFOCAL ATRIAL TACHYCARDIA is a supraventricular atrial arrhythmia caused by multiple ectopic sites of competing atrial activity, characterized by an irregular atrial rate greater than 100 beats per minute; multiple (at least three) different morphologies of P waves in the same lead, with narrow-complex QRS.

MAT is commonly seen in patients with COPD.

CHARACTERISTICS

  • Rate: greater than 100 bpm.
  • Rhythm: Irregular.
  • P Waves: At least 3 different forms, determined by the foci in the atria.
  • PR Interval: Varies, determined by focus.
  • QRS: 0.06 - 0.10.

 

Reentrant Tachycardia—150-250 bpm

REENTRANT TACHYCARDIA is a supraventricular tachycardia (tachycardia originating above the ventricles) that utilizes the atrioventricular (AV) node, AV junction, and accessory pathways for maintenance after activation by the SA or AV node. The electrical impulse “re-enters” the circuit instead of terminating after ventricular depolarization.

Rate is typically between 150-250 beats per minute and can be narrow-complex (usually) or wide-complex QRS; regular rhythm. P-waves often are indistinguishable.

CHARACTERISTICS

  • Rate: 150 - 250 bpm.
  • Rhythm: Regular.
  • P Waves: P waves are frequently buried in the preceding T waves and difficult to see.
  • PR Interval: Usually impossible to measure.
  • QRS: 0.06 - 0.10.

 

Atrial Flutter—300 bpm (atrial); variable bpm (ventricular)

ATRIAL FLUTTER is a supraventricular cardiac arrhythmia that is regular in rhythm with a distinguishable saw-tooth organization of rapid P waves representing electrical activity (depolarization and repolarization) of the atria at a characteristic rate of approximately 300 beats/min with a regular ventricular rate of about 150 beats/min with normal narrow-complex QRS, known as 2:1 A-V conduction.

The diagnosis of atrial flutter is almost always secured by the observation of a characteristic pattern on the electrocardiogram, which includes the presence of continuous, regular atrial electrical activity (depolarization and repolarization) at a characteristic rate of approximately 300 beats/min and a regular ventricular rate of about 150 beats/min in patients not taking atrioventricular (AV) nodal blockers.

CHARACTERISTICS

  • Rate: Atrial rate will be 250-350 bpm; ventricle rate will vary.
  • Rhythm: Atrial rate regular; ventricle rhythm will vary.
  • P Waves: Flutter waves have a sawtooth pattern; some may be buried in the QRS and not visible.
  • PR Interval: Variable.
  • QRS: 0.06 - 0.10 (may appear widened if the flutter waves are buried in the QRS).

 

Atrial Fibrillation— 350 bpm (atrial); variable (ventricular)

ATRIAL FIBRILLATION is a supraventricular cardiac arrhythmia that is irregularly irregular with standard, narrow QRS complexes and inverted (or no recognizable) P-waves present on the ECG. Atrial fibrillation is caused by the chaotic generation of electrical impulse in the atria or other triggers; rate often exceeds 350 beats per minute.

Rapid, erratic electrical discharge that comes from multiple atrial ectopic foci. No organized rhythm is detectable. Signs and symptoms will depend on the ventricular rate.

CHARACTERISTICS

  • Rate: Atrial rate will be greater than or equal to 350 bpm; ventricular rate will vary.
  • Rhythm: Irregular irregular (RR intervals have no repetitive pattern).
  • P Waves: No true P-waves; atrial activity is chaotic.
  • PR Interval: None.
  • QRS: 0.06 - 0.10.
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