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[[Image:Ecgfreq.png|thumb| De aftelmethode om de hartfrequentie te bepalen. Het tweede QRS-complex ligt tussen de ''75'' en de ''60'' slagen per minuut. Deze hartslag ligt daar dus tussenin, rond de 65 slagen per minuut. ]] | [[Image:Ecgfreq.png|thumb| De aftelmethode om de hartfrequentie te bepalen. Het tweede QRS-complex ligt tussen de ''75'' en de ''60'' slagen per minuut. Deze hartslag ligt daar dus tussenin, rond de 65 slagen per minuut. ]] | ||
To anwere this question, determine the time between two QRS complexes. Previously, the ECG was registered on a paperstrip transported through an ECG writer at the speed of 25 mm/second. Nowadays, digital ECG registration is common however, the method of determining the frequency remains the same. The ECG paper has a grid with thick lines 5 mm apart (= 0,20 second) and thin lines 1 mm (0,04 second). | |||
Previously, the ECG was registered on a paperstrip transported through an ECG writer at the speed of 25 mm/second. Nowadays, digital ECG registration is common however, the method of determining the frequency remains the same. | |||
The ECG paper has a grid with thick lines 5 mm apart (= 0,20 second) and thin lines 1 mm (0,04 second). | |||
'''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: [[Afbeelding:HFformule.png]] | # Count the small (1mm) lines between two QRS-complexes. Hens, the ECG paper runs with 25 mm/sec through the ECG writer, therefore: [[Afbeelding:HFformule.png]]This method work fine in case of tacycardia (>100 beats/minute)<br> | ||
This method work fine in case of tacycardia (>100 beats/minute) | |||
# To determine the frequency of a normal sinus ritme: | # 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. | 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: | You can finetune this method with the following more precise sequence: | ||
*'''300'''''-250-214-187-167-'''''150''' | *'''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. | |||
{{clr}} | {{clr}} | ||