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An R wave follows as an upward deflection, and the S wave is any downward deflection after the R wave. The T wave follows the S wave, and in some cases, an additional U wave follows the T wave. To measure the QRS interval start at the end of the PR interval (or beginning of the Q wave) to the end of the
rS pattern (small r, deep S) in the inferior leads II, III, and aVF; Delayed intrinsicoid deflection in lead aVL (> 0.045 s) LAFB cannot be diagnosed when a prior inferior wall myocardial infarction (IMI) is evident on the ECG. IMI can also cause extreme left-axis deviation, but will manifest with Q-waves in the inferior leads II, III, and aVF.
The ECG will show a terminal R wave in lead V1 and a slurred S wave in lead I. Left bundle branch block widens the entire QRS, and in most cases shifts the heart's electrical axis to the left. The ECG will show a QS or rS complex in lead V1 and a monophasic R wave in lead I.
In a 12-lead ECG, all leads except the limb leads are assumed to be unipolar (aVR, aVL, aVF, V 1, V 2, V 3, V 4, V 5, and V 6). The measurement of a voltage requires two contacts and so, electrically, the unipolar leads are measured from the common lead (negative) and the unipolar lead (positive).
Different wave shapes generated by different parts of the heart's action potential The ECG complex. P=P wave, PR=PR interval, QRS=QRS complex, QT=QT interval, ST=ST segment, T=T wave Principle of ECG formation. The red lines represent the depolarization wave, not bloodflow. An electrocardiogram is a recording of the electrical activity of the ...
There must be a prolonged S wave in leads I and V 6 (sometimes referred to as a "slurred" S wave). The T wave should be deflected opposite the terminal deflection of the QRS complex. This is known as appropriate T wave discordance with bundle branch block. A concordant T wave may suggest ischemia or myocardial infarction. [citation needed]
In the lateral leads (I, aVL, V 5-V 6) the QRS complexes are usually predominantly positive with a slow upstroke last >60ms to the R-wave peak. [4] Notching may be seen in these leads but this is not universal. The small Q-waves that are usually seen in the lateral leads are absent in LBBB. [4]
The cycle also correlates to key electrocardiogram tracings: the T wave (which indicates ventricular diastole); the P wave (atrial systole); and the QRS 'spikes' complex (ventricular systole)—all shown as color purple-in-black segments. [1] [2] The Cardiac Cycle: Valve Positions, Blood Flow, and ECG The parts of a QRS complex and