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Atrial Flutter is an abnormal heart rhythm that occurs in the atria of the heart. When it first occurs, it is usually associated with a fast heart rate or tachycardia (beats over 100 per minute), and falls into the category of supra-ventricular tachycardias. While this rhythm occurs most often in individuals with cardiovascular disease (e.g. hypertension, coronary artery disease, and cardiomyopathy) and diabetes, it may occur spontaneously in people with otherwise normal hearts. It is typically not a stable rhythm, and frequently degenerates into atrial fibrillation. However, it does rarely persist for months to years.

A variety of other underlying conditions can predispose to the development of atrial flutter. These include:

  • Atrial flutter commonly occurs after initiation of an antiarrhythmic drug for the suppression of atrial fibrillation. It may occur in up to 15 percent of patients treated with flecainide or propafenone.
  • Any of the disorders that can cause atrial fibrillation, including thyrotoxicosis, obesity, obstructive sleep apnea, sick sinus syndrome, pericarditis, pulmonary disease, and pulmonary embolism.
  • Atrial flutter is a relatively uncommon complication of an acute myocardial infarction and is rarely, if ever, a manifestation of digitalis toxicity.
  • Atrial flutter can occur after cardiac surgery, both as a postoperative complication and as a late arrhythmia. The atrial flutter in these patients is re-entrant and may involve atypical isthmuses between natural barriers, atrial incisions, and scar, as well as the cavotricuspid isthmus, the site of involvement in typical atrial flutter
  • Some patients develop atypical left atrial flutter after atrial fibrillation ablation. These arrhythmias may be due to circuits created by scar from left atrial (LA) ablations, but are often amenable to ablation themselves. This issue is discussed in detail separately.

History and physical examination — Typical complaints include palpitations, fatigue, lightheadedness, and/or mild shortness of breath. Less common problems include significant dyspnea(shortness of breath), angina (chest pain mimicking heart attack), hypotension (low blood pressure), anxiety, presyncope  (lightheadedness), or infrequently, syncope (passing out). These symptoms are in large part attributable the rapid heart rate.

Electrocardiogram — For patients in atrial flutter at the time of the electrocardiogram (ECG), it generally shows an atrial rate of about 300 beats per minute (range 240 to 340). Typical P waves are absent, and the atrial activity is seen as a sawtooth pattern (also called F waves) in leads II, III, and aVF. There is typically 2:1 conduction across the atrioventricular (AV) node; as a result, the ventricular rate is usually one-half the flutter rate in the absence of AV node dysfunction. Even atrial to ventricular rate ratios (eg, 2:1 or 4:1 conduction) are much more common than odd ratios.

Echocardiogram — A transthoracic echocardiogram should be obtained in all patients with atrial flutter to evaluate the size of the right and left atria, the size and function of the right and left ventricles, and to detect possible pericardial or valvular heart disease or left ventricular hypertrophy.

DIAGNOSIS — 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. If there are sawtooth flutter waves in the leads II, III, and aVF, it is typical atrial flutter.

COMPLICATIONS — Serious complications of atrial flutter include myocardial ischemia, dizziness or syncope, heart failure (with either preserved or reduced left ventricular systolic function), or embolization of clot. Control of the ventricular rate or reversion to normal sinus rhythm will improve or prevent the first three; anticoagulation is frequently used to decrease the risk of embolization.

Classification-There are two types of atrial flutter, the common type I and rarer type II.[4] Most individuals with atrial flutter will manifest only one of these. Rarely someone may manifest both types; however, they can only manifest one type at a time.

Type I

  • Type I atrial flutter, counterclockwise rotation with 3:1 and 4:1 AV nodal block.
  • Type I atrial flutter, also known as common atrial flutter or typical atrial flutter, has an atrial rate of 240 to 340 beats/minute. However, this rate may be slowed by antiarrhythmic agents.
  • The reentrant loop circles the right atrium, passing through the cavo-tricuspid isthmus – a body of fibrous tissue in the lower atrium between the inferior vena cava, and the tricuspid valve. Type I flutter is further divided into two subtypes, known as counterclockwise atrial flutter and clockwise atrial flutter depending on the direction of current passing through the loop.
  • Counterclockwise atrial flutter (known as cephalad-directed atrial flutter) is more commonly seen. The flutter waves in this rhythm are inverted in ECG leads II, III, and aVF.
  • The re-entry loop cycles in the opposite direction in clockwise atrial flutter, thus the flutter waves are upright in II, III, and aVF.
  • Catheter ablation of the isthmus is a procedure usually available in the electrophysiology laboratory. Eliminating conduction through the isthmus prevents reentry, and if successful, prevents the recurrence of the atrial flutter.

 

Type II-

  • Type II flutter follows a significantly different re-entry pathway to type I flutter, and is typically faster, usually 340-440 beats/minute. Left atrial flutter is common after incomplete left atrial ablation procedures.

 

Management-In general, atrial flutter should be managed the same as atrial fibrillation. Because both rhythms can lead to the formation of thrombus in the atria, individuals with atrial flutter usually require some form of anticoagulation or anti-platelet agent. Both rhythms can be associated with dangerously fast heart rate and thus require medication for rate and or rhythm control. Additionally, there are some specific considerations particular to treatment of atrial flutter.

 

Cardioversion-Atrial flutter is considerably more sensitive to electrical direct-current cardioversion than atrial fibrillation, and usually requires a lower energy shock. 20-50J is commonly enough to revert to sinus rhythm. Conversely, it is relatively resistant to chemical cardioversion, and often deteriorates into atrial fibrillation prior to spontaneous return to sinus rhythm.

 

Ablation-Because of the reentrant nature of atrial flutter, it is often possible to ablate the circuit that causes atrial flutter. This is done in the electrophysiology lab by causing a ridge of scar tissue that crosses the path of the circuit that causes atrial flutter. Ablation of the isthmus, as discussed above, is a common treatment for typical atrial flutter.

 

References:

http://en.wikipedia.org/wiki/Atrial_flutter

http://www-uptodate-com.proxy.westernu.edu/contents/overview-of-atrial-flutter?source=search_result&search=atrial+flutter&selectedTitle=1~150

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