Rate: Difference between revisions

Latest revision as of 19:51, 15 March 2011

Step 3:Conduction intervals (PQ, QRS, QT, QTc)»

The width of a square on the ECG represents time

The count method to determine the heart frequency. The second QRS complex is between 75 and 60 beat per minute. This heartbeat is between that, around 65 beats per minute.

What is the heart rate? To answer this question, determine the time between two QRS complexes. Previously, the ECG was printed on a paper strip transported through an ECG writer at the speed of 25 mm/second. Now, digital ECGs are common; however, the method for determining the frequency remains the same. The ECG 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 heart rate (HR)

The square counting method
The square counting method is ideal for regular heart rates. 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 thick line 150 etc. Stop the sequence at the next QRS complex. When the second QRS complex is between two lines, take the mean of the two numbers from the sequence or use the fine-tuning method listed below.

Use a calculator
Count the small (1mm) squares between two QRS complexes. The ECG paper runs at 25 mm/sec through the ECG printer; therefore: This method works well in case of tachycardia (>100 beats/minute)

The marker method
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.

**The 'square counting' method can be fine-tuned with the following sequence**
300	250	214	187	167	150	136	125	115	107	100	94	88	83	79	75	71	68	65	62	60

What changes the frequency of the heart?

A number of factors change the heart frequency, including:

the (para) sympathic nervous system.
- 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.
Cardiac filling increases the frequency.
arrhythmias influence heart rate.

@@ Line 1: / Line 1: @@
-{{ActiveDiscuss}}
+{{nav|
-==What is the cardiac frequency?==
+|previouspage=Rhythm
-[[Image:ECGpapier.png|thumb| The width of a square on the ECG represents time]]
+|previousname=Step 1: Rhythm
-[[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. ]]
+|nextpage=Conduction
+|nextname=Step 3:Conduction intervals (PQ, QRS, QT, QTc)
+}}
+[[Image:ECGpapier.png|thumb|300px| The width of a square on the ECG represents time]]
+[[Image:Ecgfreq.png|thumb|300px| The count method to determine the heart frequency. The second QRS complex is between ''75'' and ''60'' beat per minute. This heartbeat is between that, around 65 beats per minute.]]
+'''What is the heart rate?'''
+To answer this question, determine the time between two QRS complexes. Previously, the ECG was printed on a paper strip transported through an ECG writer at the speed of 25 mm/second. Now, digital ECGs are common; however, the method for determining the frequency remains the same. The ECG has a grid with thick lines 5 mm apart (= 0,20 second) and thin lines 1 mm (0,04 second).
-This is a easy question. To anwere this, determine the time between two QRS complexes.
+There are three simple methods to determine the heart rate (HR)
+{| class="wikitable"
+!The square counting method
+|-
+| The '''square counting''' method is ideal for regular heart rates. 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 thick line 150 etc. Stop the sequence at the next QRS complex. When the second QRS complex is between two lines, take the mean of the two numbers from the sequence or use the fine-tuning method listed below.
+|}
+{| class="wikitable"
+!Use a calculator
+|-
+| Count the small (1mm) squares between two QRS complexes. The ECG paper runs at 25 mm/sec through the ECG printer; therefore:[[Image:HFformule_en.png|none]]This method works well in case of tachycardia (>100 beats/minute)<br>
+|}
-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.
+{| class="wikitable"
+!The marker method
+|-
+|
+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.
+|}
-The ECG paper has a grid with thick lines 5 mm apart (= 0,20 second) and thin lines 1 mm (0,04 second).
+{| class="wikitable" font-size="90%" align="center"
+|+'''The 'square counting' method can be fine-tuned with the following sequence'''
+|-
-'''There are three simple methods to determine the hart frquency (HF):'''
+|'''300'''||250||214||187||167||'''150'''||136||125||115||107||'''100'''||94||88||83||79||'''75'''||71||68||65||62||'''60'''
-# 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]]<br>
+|-
+|}
-This method work fine in case of tacycardia (>100 beats/minute)
+{{clr}}
-# 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'''
+==What changes the frequency of the heart?==
-*'''150'''''-136-125-115-107-'''''100'''
+A number of factors change the heart frequency, including:
-*'''100'''''-94-88-83-79-'''''75'''
+* the (para) sympathic nervous system.
-*'''75'''''-71-68-65-62-'''''60'''
+** 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.
+* Cardiac filling increases the frequency.
-# Non regular ritmes are best determined with the "3 second marker method"
+*  [[arrhythmias]] influence heart rate.
-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}}
-==Wat beïnvloedt de hartfrequentie?==
+[[Category:ECG Course]]
-De hartfrequentie wordt door een groot aantal factoren bepaald.
-* Het autonome zenuwstelsel, de sympathicus en parasympathicus.
-** 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'')
-** 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.
-* De vulling van het hart. Bij ondervulling gaat de frequentie omhoog

Rate: Difference between revisions

Latest revision as of 19:51, 15 March 2011

What changes the frequency of the heart?

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