ELECTROCARDIOGRAM-NORMAL ELECTROCARDIOGRAM



ECG


Electrocardiogram consists of the waveforms P wave, QRS, T wave and U wave. Each wave has its duration and amplitude. Based upon the waveforms there are various segments and intervals are present in the ECG.Any changes from the normal amplitude or wavelength or waveform morphology are considered as abnormal during ECG interpretation.



The p wave is the initial deflection in the electrocardiogram.P wave is visible in the ECG due to the depolarization or contraction of the atria. The normal duration of the P wave is 0.08-0.12 sec and the amplitude of the P wave is 0.1-0.3 mV.QRS complex consists of three waves Q, R and s wave. It represents the ventricular depolarization. Normal duration is 0.08-0.12 sec and amplitude is around 0.7-4 mV. In which Q wave represents the contraction of the septum and it is a negative wave.R wave is occur due to the travelling of electrical potential to the apex of the ventricle.S wave is occurring due to the potential travelling to the base of the ventricle.T wave represents the ventricular repolarization. Its normal duration 0.27 sec and amplitude is 0.15-0.5 mV.U wave is the final wave in the ECG.U waves are thought to represent the repolarisation of the Purkinje fibres.U wave represent the last phase of ventricular repolarization.

Segments: PR, ST

PR segment denotes the time interval between the ending of the atrial depolarization and the beginning of the ventricular depolarization. ST-segment indicates the ending of the depolarization of the ventricle. The average duration is 0.05 sec.J point is the point at which S wave ends and ST-Segment begins.

Intervals:PR,QRS,QT,ST,PP,RR

PR interval is the interval between the beginning of the P wave to the beginning of the Q wave. It represents the atrial depolarization and conduction through Av node and Bundle of His. Its normal duration is 0.012-0.20 sec.QRS interval is measured from the beginning of Q wave to the J point. Normal duration is around 0.08-0.10 sec. Atrial repolarization occurs in this period.QT Interval is the interval between the beginning of the Q wave to the end of the T wave. Normal duration is 0.40-0.43 sec.QT interval varies with heart rate. When the heart rate increases QT interval decreases and heart rate decrease QT interval is increased that is QT interval is inversely proportional to the heart rate. Because of this problem, another set of indexes of the QT interval have been devised. These indexes are called rate corrected QT or QTc intervals. A widely used one is the square root method. Bazett formula: QTc=QT /root of RR interval.


You can also refer this topic in this following link:

https://www.youtube.com/channel/UCRrYRylZdS67_kbATQrLQqA

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