put tips of your two
fingers index and middle together into wrist then count the numbers of beats or hits on tips of your fingers for 15 second then
multiply it by 4 ; the result is your pulse
rate per minute. Example:
If the number of beats is 19 in 15 seconds and
multiply 19 by 4 EQUAL 76 beats / minute. Normal heart rate is 60 to 100 beats/minute.
This is the commonest and easy method for counting Heart rate or we called it Pulse
or
Another method like
one complete contraction of whole heart takes 0.8 second. At the end of
contraction the pumped blood hits the tip of two fingers as one hit take 0.8
second in normal heart or healthy heart. Thus hit equal beat so one hit is one
beat in 0.8 second so every beat takes 0.8 second. If you multiply 0.8 by numbers
of beats, you will find the total seconds. Example: if 75 beats or hits and
multiply it by 0.8 result is 60 seconds. So per minute 75 beats in normal heart,
or 60 seconds /0.8 Equal 75 beats per minute, if 15 seconds, this is 15 / 0.8 equal
18.75 beats per 15 seconds. So try it and know your heart rate.
Now we are going to the deep. There are many ways to calculate
the Pulse like from ECG; To understand this method you need to know the anatomy
of the heart, functions of it and ECG Strips. Anatomy: The heart has two atrium
and two ventricles as four chambers; Left and right atrium and the right and left
ventricles. at first the atrium receive the blood from superior vena cava then push
the blood into ventricles through atrium contractions due to electrolytes in and
out from heart muscles. Electrolytes produce the action potential of heart muscle
that contract the atrium muscles as a result blood is pumped into ventricles. Same
thing occurs in the ventricles few m second later and pump the blood into systemic
circulation as in our whole body.
the question is how do the electrolytes enter into cardiac muscles
and what are the electrolytes? Electrolytes are Sodium, Potassium and calcium enters
into muscle through Sodium channels, Potassium channels and calcium channels. Thus
channels are responsible for the electrolytes entry and action potential that is
really needs to contract the heart and pump the blood into ventricles then to the
systemic circulation. The main aim is to record the action potential of heart into
a Graph paper through ECG machine. From ECG machine the Graph paper come out with
speed of 25 mm per second. This paper contains large square boxes, each of large
square box contain 5 small squares boxes. we did not finish anatomy yet; there is
a specific area on right atrium is called the SA Node. And between atrium and ventricle
is called Atrio-ventricular node as AV node. And also this kind of area extends
into ventricles named left anterior fascicular node and right anterior
facicular nodes. These area contain all these channels. Electrolytes are available
in the blood circulation. remember when positive
charged Sodium enter into negative charged muscle specially in the specific area
is called Depolarization of the muscles as a result muscles contractions thus blood
is pumped into systemic circulation. Decreasing negative charge of muscle until
positive 10 maximum due to positive charge entry into muscle like neutralization
and little over neutralization. Then negative charge enters into new positive charged
muscle until equal as zero is called Repolarization. Now we can consider the Depolarization
is responsible to produce the Action potential as electric current that contract
the heart muscles. This action potential is recorded on ECG Strip through ECG machine
placed over chest.
During atrial contraction Graph Paper show the wave is called
the "P" wave and during ventricular contraction Graph paper show Waves
are called the 'QRS' waves. During relaxation of heart show the waves are called
T and U waves, these waves are recorded on Graph paper called ECG.
From this ECG,
We can calculate the Heart Rate. Let’s start to calculate the
pulse from patient ECG of regular beats and irregular beats or waves due to waves
on Graph paper. Example: P, QRS and T (not needed to calculate). P wave for atrial
contraction and QRS for ventricular contraction. To calculate the heart rate,
we just need QRS complexes; due to only in the ventricular contraction, pumped blood
hit the tips of fingers and shows this action on ECG as QRS complexes. R wave takes
0.2 second to pass the one big square box, so duration of RR interval is measured
by calculating numbers of big squares between RR intervals then multiplies by
0.2 second. if 4 big boxes between RR interval; 4*0.2 =0.8 second thus 60/ 0.8 = 75 bpm. Heart rate = 60/ duration of RR interval bpm or
beats per desired 60 seconds in regular rhythm.
for the irregular rhythm,
numbers of QRS complexes in 6 seconds then multiply this number by 10; if
7 QRS complexes in 6 seconds so 7 multiply by 10 = 70 bpm. Also by the 1500/ number
of small squares between RR interval or 300/ number of big square between RR interval;
1500/n =? And 300/N =?
abnormal ECG or abnormal waves of action potential indicate the
heart abnormalities e.g. diseases; conduction defect either SA Node or AV Node,
or left and right fascicular conductions due to electrolytes disturbance, or drug
toxicity, or cardiac muscle damaged, or ischemia, or AMI, or hypertrophy of ventricles, or, raised atrial pressure, or hypertension.
We can classify the etiology into atrial causes and Ventricular causes; Bradycardia
or Tachycardia, or flutter, or fibrillation could be atrial or ventricular. Or may
be conduction block; either AV block, or SA block or BBB. All these etiology show
different changes on waves of ECG. Each cause has their own specific ECG changes
recorded in ECG strip. ECGs can be recorded on 12 leads, lead |, lead || and |||
limbs lead also V1 to V6 chest leads and also aVR, aVF, and aVL. All these leads
record the impulses on ECG paper. Conduction transmits from SA node to AV node to
fascicular nodes. Thus contraction of atrium first then ventricles. SA Node has
name is called Pacemaker. In the normal ECG, first upward deflection is called P
wave, then small downward deflection is called Q, then upward deflection is called R, then downward deflection is called S, then upward is called T, then u like wave is called U ; so waves are P QRS T
and U. This is enough to understand the ECG.
Now is the memorization part; every specific heart disease has specific waves
changed. Let start memorization with little understand.
If there is a AV
node conduction block; no transmit ion to the Ventricles, thus no QRS complexes
only P wave on ECG. if some transmit ion to ventricles but slow speed ; thus some
QRS complexes with widening means take long time. Some time Always P waves on ECG
due to no impulse to ventricles means no QRS complexes are recorded. but any how
some impulse transmit to ventricles ; thus always QRS complexes are recorded with
some changed wave, otherwise
heart is death ; ventricles are unable to pump the blood, here ECG show the Flat waves on ECG.
Abnormalities of the heart are
1. Sinus tachycardia; heart beats more than 100 caused by SA
Node, 2. Supraventricular Tachycardia; caused by AV node, 3. Ventricular Tachycardia;
caused by AV node and Fascicular node. Beats less than 60 per minute is called Bradycardia.
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