Atrial Flutter

Abstract

Atrial flutter is not uncommon in cardiac patients. Electrocardiogram is helpful in differentiating it from other causes of narrow QRS tachycardia and other causes of irregular rhythm. Electrocardiogram also helps in differentiating various types of atrial flutter. This helps the electrophysiologists in planning intervention. This chapter discusses various diagnostic and therapeutic implications of electrocardiogram in a case of atrial flutter with the help of representative electrocardiograms. Summary and MCQs at the end of the chapter are useful for quick revision and self-assessment.

Appendices

Summary

• Atrial flutter is a macro-reentry tachycardia. Reentry circuit is mostly in the right atrium but rarely atrial flutter can arise in the left atrium.

• Atrial flutter waves appear as sawtooth waves best seen in lead II and/or lead V₁ without an isoelectric line. Usual rate of atrial flutter waves is between 250 and 350/min. Prominent flutter waves in lead I can suggest an origin in the left atrium. “Counterclockwise loop” of reentry produces negative flutter waves in lead II (typical atrial flutter). “Clockwise loop” (atypical atrial flutter) produces positive flutter waves in lead II.

• If the sawtooth appearance shows irregularity and/or rate is more than 400/min, it is labeled as atrial flutter-fibrillation and should be treated as atrial fibrillation.

• Usual atrioventricular conduction ratio is 2:1 with a ventricular rate around 150/min. At this ventricular rate, electrocardiographic diagnosis may be difficult because one flutter wave falls in the T wave and next flutter wave occurs with the QRS complex. Slowing atrioventricular conduction by carotid massage or drugs unmasks the atrial flutter waves.

• Carotid massage decreases the ventricular rate in stepwise fashion unlike the gradual reduction seen in sinus tachycardia or atrial fibrillation. Atrioventricular nodal reentrant tachycardia either remains unchanged or is terminated by carotid massage.

• The presence of accessory pathway with short refractory period can result in 1:1 atrioventricular conduction of the atrial flutter waves with precipitation of ventricular flutter/fibrillation.

• Irregular atrioventricular conduction of atrial flutter waves results in irregular ventricular rhythm. QRS with shorter RR interval may show aberrant ventricular conduction.

• Slow ventricular rate with changing relation between the flutter waves and the QRS complexes should suggest complete atrioventricular block.

• Electrical alternans (changing amplitude of QRS in alternating beats) can appear at fast ventricular rate.

• Prominent flutter waves can deform any part of the electrocardiogram.

• Adequate long-term control of ventricular rate with drugs is very difficult.

MCQs

Q1. Atrial flutter with 2:1 atrioventricular conduction can be differentiated from sinus tachycardia by:

• (a) Sawtooth-like appearance of the atrial flutter waves

• (b) Absence of any isoelectric interval

• (c) Apparent prolongation of “PR” interval

• (d) None of above

Q2. Regular tachycardia at a rate of 150/min without clear P waves could be:

• (a) Atrial tachycardia with 2:1 atrioventricular conduction

• (b) Atrial flutter with 2:1 atrioventricular conduction

• (c) Sinus tachycardia

• (d) Atrial fibrillation

Q3. Discrete P waves at a rate of 210/min and a ventricular rate of 70/min with isoelectric line between P waves suggest:

• (a) Sinus tachycardia

• (b) Atrial tachycardia with 3:1 atrioventricular conduction

• (c) Atrial flutter with 3:1 atrioventricular conduction

• (d) Atrial fibrillation

Q4. Sawtooth morphology of the “P” waves in lead II and V₁ suggests:

• (a) Atrial tachycardia

• (b) Atrial flutter

• (c) Multifocal atrial tachycardia

• (d) Left atrial rhythm

Q5. Which drugs can reduce the atrial rate in atrial flutter?

• (a) Quinidine

• (b) Procainamide

• (c) Amiodarone

• (d) Digitalis

Q6. Which drug decreases the refractory period of the atrial myocardial cell?

• (a) Quinidine

• (b) Procainamide

• (c) Digitalis

• (d) Amiodarone

Q7. In atrial flutter, ventricular rhythm can be:

• (a) Regular

• (b) Regularly irregular

• (c) Irregularly irregular

• (d) Any of above

Q8. In a case of atrial flutter with regular ventricular rhythm of 180/min, development of an irregular ventricular rhythm at a rate of around 120/min could be due to:

• (a) Change of atrial flutter to atrial fibrillation

• (b) Development of changing atrioventricular block

• (c) New appearance of multiple ectopics

• (d) Development of accelerated junctional rhythm

Q9. In a case of atrial flutter, ventricular rate can be:

• (a) 250/min

• (b) 200/min

• (c) 150/min

• (d) 100/min

Q10. In a case of tachycardia, carotid massage suddenly reduces ventricular rate from 180/min to 120/min. On stopping carotid massage, ventricular rate suddenly jumps back to 180/min. This response suggests:

• (a) Suppression of the sinus node

• (b) Termination of AVNRT to sinus rhythm

• (c) Conversion of atrial flutter to atrial fibrillation

• (d) Changing of atrioventricular block in atrial flutter

Q11. In a case of regular tachycardia, carotid massage produces gradual decrease in heart rate, and stopping carotid massage results in a gradual return to initial heart rate. This response suggests:

• (a) Sinus tachycardia

• (b) Antidromic AVRT

• (c) Sinus node reentry tachycardia

• (d) Changing atrioventricular block in atrial fibrillation

Q12. The upper limit of the number of atrial impulses that can be transmitted per minute through a normal atrioventricular node is:

• (a) 300/min

• (b) 250/min

• (c) 200/min

• (d) 150/min

Q13. What can increase the number of impulses that can be transmitted across a normal atrioventricular node?

• (a) Exercise

• (b) Sympathetic stimulation

• (c) Parasympathetic stimulation

• (d) None of above

Q14. Regularly irregular ventricular rhythm in a case of atrial flutter suggests:

• (a) Changing rate of atrial flutter

• (b) Changing atrioventricular conduction

• (c) Two levels of atrioventricular block

• (d) All

Q15. In atrial flutter, flutter waves are best seen in:

• (a) Lead I

• (b) Lead aVL

• (c) Leads II, III, and aVF

• (d) Leads V₁ and V₂

Q16. In atrial flutter, atrial rate is:

• (a) 100–150/min

• (b) 150–250/min

• (c) 250–350/min

• (d) 350–450/min

Q17. In atrial flutter, baseline:

• (a) Is straight

• (b) Shows regular coarse undulations

• (c) Shows coarse irregular undulation

• (d) Shows fine vibrations

Q18. Negative sawtooth flutter waves in leads II, III, and aVF suggest:

• (a) Typical atrial flutter

• (b) Reverse typical atrial flutter

• (c) Left atrial flutter

• (d) Double wave reentry atrial flutter

Q19. Atrial flutter is often initiated by:

• (a) An atrial ectopic

• (b) A junctional ectopic

• (c) A ventricular ectopic

• (d) Atrial fibrillation

Q20. Achieving adequate long-term control of ventricular rate in atrial flutter by drugs is:

• (a) Very easy

• (b) Easy

• (c) Difficult

• (d) Very difficult

Answers

• (1) a, b, c; (2) b; (3) b; (4) b; (5) a, b, c; (6) c; (7) d; (8) a, b; (9) c, d; (10) d; (11) a; (12) d; (13) a, b; (14) b, c; (15) c, d; (16) c; (17) b; (18) a; (19) a, d; (20) d