The Little Known Fatal Rhythm

A 60-year-old male comes in complaining of cough, increasing severe shortness of breath and palpitations for 3 days. He has a mild chest pressure as well. His heart rate is 120 beats per minute, blood pressure 140/90 mm Hg and oxygen 86% on room air. Here is his ECG:


This ECG makes you initially think of atrial fibrillation, as the rhythm is very irregular. It is actually what we call “irregularly irregular” — which compares to the “regularly irregular” rhythms of second-degree atrioventricular, or AV, block type I (Wenkebach) or sinus rhythm with premature ventricular contractions, or PVCs, in a pattern of bigeminy or trigeminy. 

You are thinking “Wait ... I see P waves on this ECG though, and atrial fibrillation does not have any P waves, so it can’t be atrial fibrillation.”

What do you notice about the P waves here? There are many different morphologies, or shapes. When you see three or more P-wave morphologies on an ECG that is tachycardic, the diagnosis is multifocal atrial tachycardia, or MAT. If the heart rate is less than 100 bpm with three or more P-wave morphologies, we call it wandering atrial pacemaker, or WAP.

The image below shows what a P wave looks like when it is not coming from the sinus node, known as “ectopic.”

So, what is causing this patient’s symptoms? Certainly, the rhythm itself would not likely cause severe shortness of breath at a heart rate of 120 bpm. MAT is most frequently seen in the setting of severe chronic obstructive pulmonary disease, or COPD. 

No treatment is needed other than direct therapy at the COPD itself; hopefully, the MAT will resolve. Cardioversion, either electrically or chemically, is not recommended. If the fast heart rate is indeed causing a problem — like worsening congestive heart failure symptoms or angina in a patient with severe coronary artery disease —verapamil or diltiazem have historically been used, as beta-blockers can induce wheezing at times in patients with a reactive airway component to their COPD.

Can MAT really cause any major problem then? Sounds like just an annoying rhythm to have to deal with, but with no serious consequences. Well, one scary thing about MAT is that it is a marker for severe lung disease. One report showed a 60% in-hospital mortality rate —not from the arrhythmia, of course, but from the severity of the underlying lung disease. The mean survival of patients with MAT is just more than 1 year. Thus, in many ways you can consider MAT a fatal arrhythmia in a majority of cases.

– by Steven Lome, DO, RVT