ECG waveforms and their meanings are important tools used in medicine to assess cardiac function and diagnose heart disease. The ECG reflects the physiological and pathological state of the heart by recording the graph of changes in cardiac electrical activity over time. The following are the main ECG waveforms and their meanings:
P wave: represents the depolarization process of the atrial muscle. The normal P wave is round, blunt and smooth, with a width of no more than 0.11 seconds. Abnormal P waves can reflect atrial problems, such as atrial hypertrophy, intra-atrial conduction block, etc. PR interval: represents the time from the beginning of atrial depolarization to the beginning of ventricular depolarization. The normal range is 0.12-0.20 seconds. The extension or shortening of the PR interval can indicate arrhythmias such as atrioventricular conduction block or preexcitation syndrome. QRS complex: represents the depolarization process of the ventricular muscle. The QRS complex time of a normal adult is 0.06-0.10 seconds. The morphology and duration of the QRS complex can reflect the functional state of the ventricles. Prolonged time is seen in ventricular hypertrophy and intraventricular conduction block.
ST segment: The line segment from the end of the QRS complex to the beginning of the T wave, representing a period of slow repolarization after the ventricular depolarization has just ended. The deviation of the ST segment can indicate heart diseases such as myocardial ischemia and myocardial infarction.
T wave: Represents the repolarization process of the ventricles. The morphology and direction of the T wave are closely related to the metabolic function of myocardial cells. Abnormal T waves can reflect diseases such as myocardial ischemia and myocarditis.
QT interval: The interval from the beginning of the QRS complex to the end of the T wave, representing the time required for the entire process of ventricular muscle depolarization and repolarization. The extension or shortening of the QT interval may be related to arrhythmia.
U wave: Represents the ventricular successor potential, which is a small wave that appears 0.02-0.04 seconds after the T wave, with the same direction as the T wave. Abnormal U waves may be related to myocardial ischemia or other heart diseases.