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Sinus Arrhythmia example two



Each beat in this strip is a sinus beat with a few abnormalities.   Each P-wave is followed by a QRS complex, each QRS is preceded by a P-wave, and all of these P-waves are identical.  All the P-R intervals are likewise identical.  The QRS is slightly widened with no positive deflections in the V1 lead, indicating a left bundle branch block, and the doubly peaked shape of the P-waves, with an interval greater than 0.04 seconds between peaks, indicates left atrial enlargement.  The abnormality of rhythm is the irregular rate: no two R-R intervals are the same, and there is no regular pattern to this irregularity.   This is an example of sinus arrhythmia, but is a less common type, where there is no relationship between the irregularity of rate and the respiratory pattern.  Possible causes here may be sick sinus disease or digoxin toxicity.