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Sinus Arrhythmia example one



This rhythm is different from normal sinus rhythm in one way only: the
R-R intervals vary.  There is a P-wave before every QRS, and a QRS after
every P, all the P-waves are the same, and all the QRS complexes are the
same.  No interval or shape is abnormal.  However, the R-R intervals are,
starting from the left, 0.80 seconds, 0.72 seconds, 0.68 seconds, 0.76, 0.84,
0.86, 0.76, 0.68, 0.72, 0.80, 0.92, 0.84, and 0.70 seconds.  Almost none are
alike, but there is a definite pattern.  Notice how the intervals decrease
and then increase regularly.  This is caused by the respiratory pattern:
inspiration increases the heart rate and expiration lowers it.  This strip
shows a respiratory rate of about 18 per minute.  The respiratory periods
have been indicated under the uppermost strip.