In situations of very rapid atrial depolarization, the node will only conduct some fraction of the atrial depolarization events to the ventricles. However, the AV node is uniquely capable of mediating ‘decremental conduction’. If 300 atrial depolarization events per minute were conducted to the ventricles, the resulting heart rate would result in failure of the ventricles to fill with blood between beats with a potentially lethal fall in cardiac output. Usually in the region of 300 times per minute. The diagnosis of atrial flutter is confirmed by identification of atrial depolarization occurring at a rate between 200 and 400 times per minute. To make the diagnosis of atrial flutter we need to identify evidence on the ECG of atrial depolarization occurring at or near this rate (while remembering that there is a range of possible rates). In the majority of cases, the rate of atrial depolarization is in the region of 300 discharges per minute. The rate of atrial depolarization mediated by the re-entrant loop in this condition varies between cases from about 200 to 400 discharges per minute. Each cycle discharges a depolarization wave superiorly into the left atrium depolarizing the atria (blue arrow). In atrial flutter, a re-entrant loop of depolarization (blue circle) circulates (black arrows) in the wall of the right atrium.
The views expressed are not endorsed by any clinical body. Some of the terms in this article: ss: small squares, bpm: beats per minute, HR: heart rate, index ECG: the ECG featured in the case 'a challenging ECG diagnosis'.ĭisclaimer: this article is an opinion piece.
Understanding the mechanism generating tachycardia in atrial flutter and a knowledge of a few 'tricks of the trade' can help increase our chances of making the diagnosis of this arrhythmia.
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