ECG REVIEW

Is a portable device for continuously monitoring various electrical activity of the heart for at least 24 hrs often for 2 weeks at a time.

Is the process of recording electrical activity of the heart.

ECG is recorded on grid paper. The horizontal axis record time, with black marks at the top indicating 3sec. The vertical axis records amplitude (voltage). Small block = 0.1mV.

Every paper is marked by 5 large grid blocks. Each large grid block = 0.20sec. Within the large blocks there are 5 small blocks, each representing 0.04 sec. Speed 25mm/sec.

Represents atrial depolarization (the time necessary for an electrical impulse from the SA node to spread throughout the atrial musculature). Amplitude 2 to 2.5 mm, Duration 0.06 to 0.11 sec

Represents the time it takes an impulse to travel from the atria to AV node, bundle of His, bundle of branches to the Purkinje fibers. Goes from the beginning of P wave to the beginning of QRS. Duration 0.12 to 0.20 sec.

Represents ventricular depolarization, consists of 3 waves the Q wave, the R wave and the S wave. Q wave is not always present. R is a positive deflection and S is a negative deflection. Follows the P-R interval, amplitude varies with age and sex and the duration is 0.06 to 0.12 sec. (1.5 to 3 small blocks)

Represents the time necessary for ventricular depolarization and repolarization. Measure to the beginning of QRS complex to the end of T wave. duration varies according to age, sex and HR, 0.36 to 0.44sec (9-11 small blocks)

Indicates the repolarization of the ventricles, is an slightly asymmetrical and follows the QRS complex after a pause. Rare times U wave follows T wave. The U wave represents the repolarization of the Bundle of His and Purkinje fibers. Amplitude 5mm or less in standard leads I, II, III; 10mm or less in V1-V6. not measured.

Represents the end of ventricular depolarization and the beginning of repolarization. Extends from the end of the S wave to the beginning of the T wave. Not masured

Count the number of QRS complexes over a 6 second interval. Multiply by 10 to determine heart rate. This method works well for both regular and irregular rhythms. In the first image, we can count 7 QRS complexes, so the heart rate is 70.

Count the number of small boxes for a typical R-R interval. Divide this number into 1500 to determine heart rate. In the second image, the number of small boxes for the R-R interval is 22.5. The heart rate is 1500/21.5, which is 69.8. (70BPM)

V1 & v2 (Right Ventricle)V3 & V4 (septum/lateral left ventricleV5 & V6 (Anterior/Lateral Left Ventricle)

V1: Fourth intercostal space to the right of the sternum.
V2: Fourth intercostal space to the Left of the sternum.
V3: Directly between leads V2 and V4.
V4: Fifth intercostal space at midclavicular line.
V5: 5th ICS at left anterior axillary line.
V6: 5th ICS at left midaxillary line. (Directly under the midpoint of the armpit)