The impulses continue to the cardiac muscle cells by terminal fibers called Purkinje fibers. These bundles are located within the right and left ventricles. From the AV node, the impulses travel to the bundle of His and onward to the right and left bundle branches. Electrical impulses travel through a conduction system beginning with the sinoatrial (SA) node and moving to the atrioventricular (AV) node via internodal pathways. The electrocardiogram (ECG), a noninvasive study, measures the electrical currents or impulses that the heart generates during a cardiac cycle (see figure of a normal ECG at end of monograph). The monitoring of pulse and blood pressure evaluates only the mechanical activity of the heart. Therefore, the heart will maintain a predetermined heart rate unless other stimuli are received. All muscle cells have a characteristic rate of contraction called depolarization. The systolic phase of the cardiac cycle reflects the contraction of the myocardium, whereas the diastolic phase takes place when the heart relaxes to allow blood to rush in. The cardiac muscle consists of three layers of cells: the inner layer called the endocardium, the middle layer called the myocardium, and the outer layer called the epicardium. See His bundle electrocardiography, Signal-averaged electrocardiography, Sleep electrocardiography.
#CARDIAC MONITOR THAT CONTIUSLY MONITY ST ELEVATION PORTABLE#
electrocardiogram ECG, EKG Cardiology A non-invasive test of the electrical activity of heart's conduction system, which is transformed into recordings on graph paper–an electrocardiograph in an EKG, electrodes–leads are placed on 12 specific sites of the body: standard limb leads–I, II, III, augmented limb leads–aV r, aV l, and aV f, and precordial or chest leads–V 1 to V 6 EKG tracings consist of 3 major components: the P wave, which indicates atrial depolarization, the QRS complex–ventricular depolarization, and the T wave–ventricular repolarization the Holter monitor is a portable EKG recording device worn by an individual for continuous monitoring the EKG is used to detect cardiac damage by evaluating alterations in the electrical conduction the heart, and can be performed at rest or during excercise–eg thallium stress test the Holter monitor is a portable device worn by a Pt for continuous cardiac monitoring the EKG is used to detect the presence and location of myocardial ischemia or infarction, cardiac hypertrophy, arrhythmias, conduction defects. The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company.
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