How to Read rhythm and pattern of ECG
1. Rhythm and pattern of ECG
1.1 ECG rhythm Rhythm refers to the origin that controls the electrical activity of the heart. The electrical activity of a normal heart rhythm (heart rhythm) originates in the sinus node and is called sinus rhythm. The normal frequency of the sinus node is 60 to 100 beats per minute (bpm). Above this frequency is called sinus tachycardia, and below this frequency is called sinus bradycardia. Except for the sinoatrial node, the atrium, atrioventricular node, and ventricle all have self-beat rhythms and locations with different frequencies, and these self-beat rhythm points are called ectopic rhythm points.
1.2 The ECG pattern and the naming of each wave The anatomical heart is divided into 4 chambers, the left and right atrium and the left and right ventricle. Since both atria contract at the same time, both ventricles also contract at the same time. Therefore, from the perspective of electrical activity, the heart can be seen as two chambers: the atrial chamber and the ventricular chamber.
The atrial muscle is small in texture and thin in wall, and the potential changes during depolarization are small. The ventricular muscle texture is large and the wall is thick, the potential changes generated when the ventricle is depolarized, and the high potential amplitude recorded by the electrocardiogram is called QRS wave. The process of returning the ventricular muscle to a resting state after depolarization is called repolarization, forming the T wave of the ECG.
In the early days of ECG research, Einthoven expressed the various waves of the ECG with English letters: P represents atrial depolarization wave, and Q, R, and S all represent ventricular depolarization waves, which are collectively referred to as QRS complexes. The Q wave is the first negative wave in the QRS complex, the R wave is a positive (upright) wave, and the negative wave after the R wave is called the S wave. The front part of the QRS wave can have a Q wave or no Q wave. The part between the S and T waves is called the ST segment. The U wave is a low and wide waveform 0.20~0.40s after the T wave, and the formation mechanism is unclear.