What does “marked sinus arrythmia” on an EKG mean?
While the other respondent’s math derived suppositions of the definition of “sinus” is colorful as it is creative, it bears no relationship to the medically accepted meaning of “sinus rhythm.” A sinus beat describes a cardiac electrical origin arising from a specific anatomical point, the collection of specialized pacemaker cells better known as the Sinus node (aka “sino-atrial” node). Further, the EKG only records electrical activity and is unable to detect mechanical phenomena (ie valve opening or closing, et cetera) of the heart. Sinus arrhythmia is simply a change in heart rate that is coincidental to the respiratory pattern. That is, when you inhale the heart rate speeds up a little and when you exhale it slows back down. This is caused by stimulation of the nervous system with pulmonary movement. It is considered an absolutely normal finding in children and young adults, and usually (but not always) disappears with age. It is considered medically normal and nothing needs to be do
