To simplify the name "Multifocal Atrial Tachycardia", let's break it down.
- Multifocal; The multi-shaped P waves (3 or more), being generated from multiple focal-points
within the atria, where this irregular pacing is being generated from.
- Atria; represents the location where these multi-shaped P waves originate from.
- Tachycardia; Simply means a fast heart rate greater than 100.
With sinus rhythm, the heart is normally paced by the SA node. With MAT, a number of different sites
(cell clusters) originating within the atria, take control of the heart rate (multiple sites of competing
atrial activity). The automaticity rate of these multifocal-sites rise above the sinus rate and take over pacing,
causing this multifocal atrial rhythm to occur. On an EKG, it is identified by having at least three different
morphologically distinct P waves. These excitable cell clusters send electrical signals that compete
to be the one to pace the heart. With these sites being in different locations and
generating signals that clash and compete with each other, this causes a very irregular rhythm.
MAT has a heart rate above 100 bpm and is irregular. MAT can be a constant rhythm
or paroxysmal i.e. "a run of MAT". It is considered to be a transitional rhythm that leads from a sinus rhythm
with frequent PACs, into A flutter or A fib. Causes of MAT are mainly due to underlying illnesses. Most of the
time it is associated with chronic obstructive pulmonary disease (COPD). Multifocal atrial Tachycardia
(heart rate >100) and Wondering Atrial Pacemaker (heart rate < 100) are both multifocal atrial arrhythmias.
Definition:
- A rapid irregular rhythm originating from the Atria.
- At least three distinct P wave morphologies in the same lead.
- A heart rate greater than 100, usually ranging 100 to 150.
- The same characteristics as Wondering Atrial Pacemaker (WAP) except WAP's heart rate is below 100.
- P-waves can be aberrantly conducted, non-conducted or inverted.
- It has very little thromboembolism risk because the atrium contracts from the conducted signal, unlike A-fib/ A-flutter.
Causes:
- Decompensated chronic lung disease
- Coronary artery disease
- Heart failure
- Heart valve disease
- Diabetes mellitus
- Hypokalemia
- Hypomagnesemia
- Azotemia
- Postoperative state
- Pulmonary embolism
- Pneumonia
- Sepsis
- Methyl xanthine toxicity
Treatment:
Treatment involves treating the underlying condition or illness. The overall clinical picture and symptoms
improve when the underlying condition is addressed and MAT is controlled. MAT in of itself is seldom life
threatening. COPD is primarily the most common contributor of MAT. Therapy also may include the following:
- Calcium channel blockers: Used as the first line of treatment
- Magnesium sulfate (when used to correct hypokalemia, most patients convert to sinus rhythm)
- Beta-blockers
- Antiarrhythmics
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