In order for the heart to contract, like any muscle, it gets stimulated by an electrical conduction system that runs a tiny electrical current just like a wire.
In the arms and legs, this electrical signal is supplied by nerves that come from the brain. In the heart, however, there is a conduction system made out of specialized cells that are part of the heart.
The flow of electrical signal is detectable by electrocardiogram (ECG). If you examine that word, you'll see that it means ';electrical picture of the heart.'; In the simplest system, electrical leads are placed at the shoulders and low on the body, on the left side. As the waves of electrical impulse pass through the heart muscle, a tiny electrical current is created between the wires, and this is amplified and graphed on paper. The up and down tracings of the current is what we read.
The most important thing about ECG reading is to understand that dead or injured heart muscle fails to conduct electricity readily like the living and normally functioning conduction system.
Because of the 3 dimensional arrangement of the leads around the heart, we can learn about the conduction of electricity in various directions, all at the same time. We can actually detect when there is a change in conduction in a specific direction.
When we look at the tracings on paper, we see several defined portions of the wave pattern and you've mentioned the ';P wave';. Following the P wave, there's a ';QRS complex'; and then a ';T wave';. The P wave is a small hump in the graph. The QRS complex is a big spike that follows the P, and then after the QRS, there's a moderate sized hump that is the T wave.
The P wave represents the electrical activity which causes the initiating portion of the heart contraction. After the P wave the ';atria'; (singular: ';atrium';), which are small chambers on the upper portion of the heart, do their contractions. The QRS complex represents the electrical activity that initiates the main contraction of the heart. After the QRS complex, the ';ventricles'; contract, pumping the blood out to the lungs and to the body. The T wave represents the electrical activity of the heart resetting itself for the next beat.
Specific known heart problems are associated with characteristic abnormalities on ECG. Much of the reading of ECG's, therefore, is based on recognizing known patterns of change to the normal waves. When there has been, or there is currently a heart attack in progress, the portion of the heart muscle involved can be 3 dimensionally localized by way of the pattern.
The ';reading'; of ECG's requires a lot of practice and a lot of experience. Fortunately for us doctors who don't do a lot of it, there are specific things to look for that help tell the difference between emergency situations and non-emergency.
Additionally, the computer that prints out the result actually has some basic ECG reading capability itself! There are some diagnoses that print out right on top of the page!!
Ok... I've got a talented 5 year old... what can I say. ;)
I hope that helps.Can someone explain how the Electrocardiogram works? P wave etc. What is it and what can you learn from this?
the P wave is the ECG picking up the contraction/electrial pulse of the atria,
the QRT waves are basically the ventricals contracting/electrical pulse
and the S wave shows the ventricals relaxing, hyperpolarising.
The reason why you cant see the atria hyperpolarising is because the ventricals are contacting at the same time (approximately!!)
The QRT wave consists of 3 waves due to the way the electrical impulse travels around the ventricals... first down the middle (Q) then the right side (R) and then the left side (T)... this is just the way the ECG picks it up...
The reason why the S wave is in the same direction as the as the P waves even though one is depolarisation and the other is hyperpolerisation is due to the action potential properties of the particular cardiac cells... its a hard point to understand but basically its due to different refactory periods (of action potentials) of the cardiac cells...
I hope this help you understand!!!
We have cells in the heart which conduct electrical impulses. ECG measures that. P wave indicates conduction of electrical impulse from one specific part of the heart to another. There are q, r, s, t and u waves too, which measures the electrical conduction in other specific areas of the heart. We can look at these waves to tell whether there is a heart disease or not, and also the exact location of the defect. We can detect almost any heart diseases with ECG. The most common use for ECG is to detect the presence of irregular heart beat(in young) and heart attack(in old).
Wow-- a whole textbook in one paragraph. Why not ask '; describe the Universe and give 3 examples';?
Here is a reference to get you started. Google EKG or ECG. There is a LOT to know, and I don't know it all. The Cardiologists are the experts in EKG, just as a Neurologist reads an EEG.
http://en.wikipedia.org/wiki/Electrocard鈥?/a>
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