Descriptions: Large regular P-waves (sinus rate of 250~350BPM). Ventricular response varies.

Atrial flutter (AFL) is an abnormal heart rhythm that occurs in the atria of the heart.^[1] When it first occurs, it is usually associated with a fast heart rate or tachycardia (beats over 100 per minute),^[2] 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 (AF). However, it does rarely persist for months to years.

Signs and symptoms

While atrial flutter can sometimes go unnoticed, its onset is often marked by characteristic sensations of regular palpitations. Such sensations usually last until the episode resolves, or until the heart rate is controlled.

Atrial flutter is usually well tolerated initially (a high heart rate is for most people just a normal response to exercise), however, people with other underlying heart disease or poor exercise tolerance may rapidly develop symptoms, which can include shortness of breath, chest pains, lightheadedness or dizziness, nausea and, in some patients, nervousness and feelings of impending doom.

Prolonged fast flutter may lead to decompensation with loss of normal heart function (heart failure). This may manifest as effort intolerance (exertional breathlessness), nocturnal breathlessness, or swelling of the legs or abdomen.

Atrial flutter is recognized on an electrocardiogram by presence of characteristic flutter waves at a regular rate of 240 to 440 beats per minute. Individual flutter waves may be symmetrical, resembling p-waves, or may be asymmetrical with a "sawtooth" shape, rising gradually and falling abruptly or vice versa. If atrial flutter is suspected clinically but is not clearly evident on ECG, acquiring a Lewis lead ECG may be helpful in revealing flutter waves.

Pathophysiology

Atrial flutter is caused by a reentrant rhythm in either the right or left atrium. Typically initiated by a premature electrical impulse arising in the atria, atrial flutter is propagated due to differences in refractory periods of atrial tissue. This creates electrical activity that moves in a localized self-perpetuating loop. For each cycle around the loop, there results an electric impulse that propagates through the atria.

The impact and symptoms of atrial flutter depend on the heart rate of the patient. Heart rate is a measure of the ventricular rather than atrial activity. Impulses from the atria are conducted to the ventricles through the atrio-ventricular node. Due primarily to its longer refractory period, the AV node exerts a protective effect on heart rate by blocking atrial impulses in excess of about 180 beats/minute, for the example of a resting heart rate. (This block is dependent on the age of the patient, and can be calculated roughly by subtracting patient age from 220). If the flutter rate is 300/minute only half of these impulses will be conducted, giving a ventricular rate of 150/minute, or a 2:1 heart block. The addition of rate-controlling drugs or conduction system disease can increase this block substantially (see image below).

Reference: https://en.wikipedia.org/wiki/Atrial_flutter

Post by: Harvey Chen , 帕金森氏症的抗病心路歷程