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Non-regular rhythms are best determined with the "3 second marker method". Count the number of QRS complexes that fit into 3 seconds (some ECG writers | Non-regular rhythms are best determined with the "3 second marker method". Count the number of QRS complexes that fit into 3 seconds (some ECG writers print this period on the ECG paper). Multiply this number by 20 to find the number of beats/minute. | ||
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A number of factors change the heart frequency, including: | A number of factors change the heart frequency, including: | ||
* the (para) sympathic nervous system. | * the (para) sympathic nervous system. | ||
** The '''sympathic system''', e.g. epinephrine, (=adrenalin) increases atrioventricular conduction and contractility | ** The '''sympathic system''', e.g. epinephrine, (=adrenalin) increases atrioventricular conduction and contractility (the ''fight or flight'' reaction.) | ||
** The parasympathic system (nervus vagus,) e.g. acetycholine, decreases the frequency and atrioventricular conduction. The parasympathic system affects mainly the atria. | ** The parasympathic system (nervus vagus,) e.g. acetycholine, decreases the frequency and atrioventricular conduction. The parasympathic system affects mainly the atria. | ||
* Cardiac filling increases the frequency. | * Cardiac filling increases the frequency. | ||