Question

What physiological event is represented by the &#x27;sawtooth&#x27; baseline pattern observed in atrial flutter?

Accepted Answer

The sawtooth baseline pattern, often called flutter waves, is caused by a macro-reentrant circuit within the right atrium of the heart. In a normal heartbeat, an electrical signal travels from the top of the heart to the bottom in a single path. In atrial flutter, an electrical impulse gets trapped in a continuous, circular loop around the tricuspid valve annulus. Because this circuit moves at a rapid, constant rate, the heart&#x27;s upper chambers, or atria, depolarize—meaning they undergo an electrical charge shift—in a rhythmic, repeating fashion. This circular electrical activity does not pause, which prevents the heart from having a flat baseline between beats on an electrocardiogram. Instead, the continuous electrical flow creates the characteristic undulating, jagged, or sawtooth appearance. Because the electrical circuit is locked in this consistent loop, the atria contract at a fixed high rate, typically around 300 beats per minute, while the lower chambers, or ventricles, usually receive signals at a slower rate due to the heart&#x27;s natural gatekeeper, the atrioventricular node, which blocks some of these impulses from passing through.

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What physiological event is represented by the 'sawtooth' baseline pattern observed in atrial flutter?