Assessment of an ECG strip illustrates a person’s heart rate, heart rhythm, and the conduction pathways of the heart’s electrical currents, according to eMedicineHealth. Conduction of electricity in healthy heart tissue differs from conduction in the tissue of diseased hearts.
The paper that ECG machines print on records time horizontally in seconds. Heart rate are determined fairly accurately by counting the small boxes on the paper. A normal heart rate is 60 to 99 beats per minute, states Ambulance Technician Study, which would cover 15 to 25 small boxes.
The voltage of the heart’s electrical current is measured vertically in millivolts, demonstrating the magnitude of P-QRS-T waves. This basic sequence represents a complete cardiac cycle, beginning with depolarization of the atria, or P wave, and ending with ventricular repolarization, or T wave. The QRS complex in the middle of the cycle is evidence of the ventricles’ depolarization, points out Nurses Learning Network.
The sinoatrial and atrioventricular nodes, bundle of His, bundle branches and Purkinje network make up this conduction system, notes Nurses Learning Network. Through electrodes attached to the chest, the ECG machine can determine the amount of time it takes for an electrical impulse to travel through the heart’s conduction system. Interpretation of that interval of time helps a physician appraise a heart’s condition, including abnormal or harmful rhythms.