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'''There are three simple methods to determine the hart frquency (HF):'''
'''There are three simple methods to determine the hart frquency (HF):'''
# Count the small (1mm) lines between two QRS-complexes. Hens, the ECG paper runs with 25 mm/sec through the ECG writer, therefore:&nbsp;&nbsp;&nbsp;[[Afbeelding:HFformule.png]]This method work fine in case of tacycardia (>100 beats/minute)<br>
# Count the small (1mm) lines between two QRS-complexes. Hens, the ECG paper runs with 25 mm/sec through the ECG writer, therefore:&nbsp;&nbsp;&nbsp;[[Afbeelding:HFformule.png]]This method work fine in case of tacycardia (>100 beats/minute)<br>
# To determine the frequency of a normal sinus ritme: Use the sequence 300-150-100-75-60-50-43-37. Count from the first QRS complex, the first thick line is 300, the next line 150 etc. Stop the sequence at the next QRS complex. When the second QRS complex is in between two lines, take the mean of the two numbers from the sequence. You can finetune this method with the following more precise sequence: *'''300'''''-250-214-187-167-'''''150'''
# To determine the frequency of a normal sinus ritme: Use the sequence 300-150-100-75-60-50-43-37. Count from the first QRS complex, the first thick line is 300, the next line 150 etc. Stop the sequence at the next QRS complex. When the second QRS complex is in between two lines, take the mean of the two numbers from the sequence. You can finetune this method with the following more precise sequence:  
*'''300'''''-250-214-187-167-'''''150'''
*'''150'''''-136-125-115-107-'''''100'''
*'''150'''''-136-125-115-107-'''''100'''
*'''100'''''-94-88-83-79-'''''75'''
*'''100'''''-94-88-83-79-'''''75'''
*'''75'''''-71-68-65-62-'''''60'''  
*'''75'''''-71-68-65-62-'''''60'''  
# Non regular ritmes are best determined with the "3 second marker method" Count the number of QRS-complexes that fitt in 3 seconds (some ECG writers register this period on the ECG paper. Multiply this number by 20 and find the number of beats/minute.  
 
# Non regular ritmes are best determined with the "3 second marker method" Count the number of QRS-complexes that fitt in 3 seconds (some ECG writers register this period on the ECG paper). Multiply this number by 20 and find the number of beats/minute.  


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==Wat beïnvloedt de hartfrequentie?==
==What changes the frequency of the heart?==
De hartfrequentie wordt door een groot aantal factoren bepaald.
A number of factors change the heart frequency including:
* Het autonome zenuwstelsel, de sympathicus en parasympathicus.  
* the (para) sympathic nerve system.  
** Het '''sympathisch systeem''' o.i.v. epinephrine (=adrenaline) leidt bij activatie tot een toename in atrioventriculaire geleiding, prikkelbaarheid en contractiliteit. (in de oertijd goed voor: ''fight, fright, flight'')
** The '''sympathic system''' e.g. epinephrin (=adrenalin) increases the atrioventricular conduction and contractility. (the ''fight, fright, flight'' reaction)
** Het parasympathische systeem (nervus vagus) o.i.v. acetycholine leidt daarentegen bij activatie  tot een afname in frequentie van de SA-knoop, atrioventriculaore voortgeleiding en prikklebaarheid. In tegenstelling tot het sympathisch systeem werkt het parasympathicus voornamelijk op de atria.
** Het parasympathic system (nervus vagus) e.g. acetycholin decreases the frequency and atrioventricular conduction. The parasympathic system effects mainly the atria.
* De vulling van het hart. Bij ondervulling gaat de frequentie omhoog
* De filling of the heart. Cardiac filling increases the frequency.