...cardiac cells and the relationship between membrane...
...levels. 2. Describe the cardiac conduction system,...
...cardiac conduction system, the normal electrocardiogram (ECG)...
...nursing responsibilities for the patient who requires...
...dysrhythmias arising from the sinoatrial (SA) node...
...9. Distinguish among the four conduction abnormalities,...
...nursing implications for the patient receiving these...
...A. Resting cardiac cell 1. Cardiac function...
...dependent on myocardial cell permeability and is...
...electrolytes. 2. During the resting state, the...
...the resting state, the inside of the...
...the inside of the cell is more...
...inside of the cell is more electrically...
...negative relative to the outside of the...
...the outside of the cell due to...
...outside of the cell due to the...
...cell due to the differences in ion...
...B. Active cardiac cell—action potential 1. Depolarization...
...and repolarization a) The transmission of electrical...
...produces changes in the myocardial cell membrane’s...
...in the myocardial cell membrane’s electrical charge,...
...electrical charge, stimulating the cardiac cells extending...
...cells extending across the myocardial muscle to...
...relaxation. b) As the cardiac cell receives...
...As the cardiac cell receives an electrical...
...and repolarization of the cardiac muscle. 2....
...a) Depolarization (Phase 0)—the cell is almost...
...Depolarization (Phase 0)—the cell is almost impermeable...
...b) Repolarization (Phases 1–3)—the process of repolarization...
...potential (Phase 4)—during the resting membrane potential...
...repolarization is completed, the original electrochemical gradient...
...in place, and the cell is ready...
...place, and the cell is ready to...
...a) Absolute refractory period—the cell cannot respond...
...Absolute refractory period—the cell cannot respond to...
...stimulus regardless of the strength of the...
...the strength of the stimulus. b) Relative...
...b) Relative refractory period—the cell is relatively...
...Relative refractory period—the cell is relatively (but...
...Dependent on myocardial cell permeability. Cellular permeability...
...2. Resting Cardiac Cell Negatively charged or...
...is greater inside the cell. Sodium concentration...
...greater inside the cell. Sodium concentration is...
...is greater outside the cell. Calcium concentration...
...greater outside the cell. Calcium concentration is...
...is greater outside the cell. Produces intracellular...
...greater outside the cell. Produces intracellular electrical...
...change in myocardial cell polarity. Five-phase cycle...
...of a Cardiac Cell Produces changes in...
...Produces changes in the cell’s membrane electrical...
...changes in the cell’s membrane electrical charge....
...Cardiac Conduction and the Electrocardiogram 1. The...
...the Electrocardiogram 1. The cardiac cycle is...
...electrical circuit in the myocardium, where specialized...
...myocardial cells influence the electrical conduction pathway....
...Electrical conduction of the heart 1. The...
...the heart 1. The primary pacemaker of...
...primary pacemaker of the heart is the...
...the heart is the sinoatrial (SA) node,...
...node, which controls the heart rate normally...
...per minute (bpm). The impulse from the...
...The impulse from the SA node is...
...transmitted: a) From the atria b) To...
...atria b) To the ventricles c) Along...
...conduction pathway 2. The normal conduction pathway...
...conduction pathway a) The impulse from the...
...The impulse from the SA node is...
...transmitted: (1) From the atria (2) To...
...atria (2) To the ventricles (3) Along...
...b) Starting at the SA node, the...
...the SA node, the conduction pathways continues:...
...continues: (1) To the atrial-ventricular (AV) node...
...node (2) To the bundle of His...
...(3) Proceeding along the left and right...
...(4) Terminating at the Purkinje fibers (5)...
...muscle cells B. The electrocardiogram 1. The...
...The electrocardiogram 1. The Normal ECG Pattern....
...is verified by the nurse at the...
...the nurse at the beginning of each...
...Electrical Conduction of the Heart Intrinsic electrical...
...Conduction Pathway 4. The Electrocardiogram (ECG) Represents...
...Interpretation Guidelines 1. The ECG is printed...
...small block of the graph paper being...
...0.04 seconds on the horizontal axis. The...
...the horizontal axis. The horizontal axis also...
...also represents time. The vertical axis of...
...vertical axis of the graph paper represents...
...(0.1 mV) on the vertical axis. For...
...interpretation, time is the most important factor...
...R–R interval, examine the P wave, measure...
...P wave, measure the PR interval, determine...
...examine and measure the QRS complex, examine...
...examine and measure the QT interval, and...
...interval, and diagnose/interpret the rhythm. A. ECG...
...paper B. Measure the heart rate C....
...rate C. Examine the R–R intervals D....
...intervals D. Examine the P waves E....
...waves E. Measure the PR interval F....
...Examine and measure the QRS complex H....
...complex H. Measure the QT interval I....
...interval I. Diagnose the rhythm J. Clinical...
...potentials 3. Increases cell excitability D. Altered...
...are Prone to the Development of Dysrhythmias....
...it originates in the SA node. It...
...medication that blocks the parasympathetic innervations to...
...parasympathetic innervations to the SA node. B....
...produce angina if the cardiac output decreases...
...output decreases to the point of reducing...
...aimed at relieving the cause of increased...
...ectopic impulses within the atria. They may...
...may develop when the SA node is...
...foci) develops in the atria. A. Premature...
...pacemakers located in the atria B. Supraventricular...
...150 and 250. The rhythm is regular;...
...is regular; however, the P waves are...
...are buried in the preceding T wave....
...complex indicates that the ectopic pacemaker is...
...is located above the ventricles. 2. Treatment...
...Valsalva’s maneuver to the use of calcium...
...than 250 bpm. The ventricular rate depends...
...rate depends on the number of impulses...
...that pass through the AV node. D....
...condition in which the atria are contracting...
...waves Described by the number of atrial...
...dysrhythmias occur because the SA node fails...
...to fire, so the AV node initiates...
...AV node initiates the impulses. The junctional...
...initiates the impulses. The junctional area is...
...is located around the AV node. 2....
...Pacemaker cells around the AV node have...
...bpm. 3. Once the pacemaker cell discharges,...
...Once the pacemaker cell discharges, the impulse...
...pacemaker cell discharges, the impulse spreads upward...
...upward to depolarize the atria and downward...
...downward to depolarize the ventricles. 4. The...
...the ventricles. 4. The QRS complex appears...
...complex appears normal, the atria are depolarized...
...abnormal manner; therefore, the P wave might...
...might be inverted. The timing of the...
...The timing of the P wave is...
...abnormal; it precedes the QRS complex, and...
...QRS complex, and the PR interval is...
...than 0.12 seconds. The P wave also...
...be buried in the QRS complex, and...
...or might follow the QRS complex. 5....
...100 bpm. If the rate is between...
...drug therapy and/or the insertion of a...
...that originate in the ventricle and can...
...from loss of the atrial kick from...
...that originate in the ventricle and discharge...
...and discharge before the next normal sinus...
...During ECG interpretation, the nurse assesses and...
...assesses and describes the patient’s underlying cardiac...
...cardiac rhythm and the type of PVCs...
...major responsibility of the nurse is to...
...is to assess the patient for factors...
...that contribute to the development of PVCs...
...of PVCs and the presence of specific...
...fatal rhythm, is the most common cause...
...2. Defibrillation is the treatment of choice...
...or vasopressin. If the patient remains pulseless,...
...of electrical impulses. The patient is unconscious...
...is imperative that the nurse check that...
...nurse check that the rhythm is verified...
...5. Ventricular Fibrillation The most common cause...
...arrest. Defibrillation is the treatment of choice...
...inhibited anywhere along the conduction pathway. Factors...
...activity. 2. When the delay occurs at...
...delay occurs at the antrioventricular (AV) node...
...are based on the relationship of the...
...the relationship of the P wave to...
...P wave to the QRS complex. A....
...in conduction through the AV node; the...
...the AV node; the remainder of the...
...the remainder of the ECG is normal....
...asymptomatic; however, in the presence of acute...
...is present, but the PR interval is...
...constant before dropping the QRS complex. Nursing...
...management depends on the degree of block...
...are exhibited by the patient. c) Management...
...emergency treatment, because the atria and ventricles...
...inadequate filling of the ventricles. No impulses...
...are conducted through the AV node. The...
...the AV node. The atria and ventricles...
...regular, as is the R–R wave interval,...
...wave interval, but the PR intervals vary....
...no relationship between the P wave and...
...P wave and the QRS complex, because...
...QRS complex, because the atria and the...
...the atria and the ventricles are paced...
...a separate pacemaker. The QRS complex is...
...wide because of the ventricular origin of...
...ventricular origin of the stimulus. In rare...
...In rare cases, the ventricular rate is...
...heart block is the same as for...
...in conduction through the bundle of His...
...blocked. Occurs in the AV nodal area....
...not conducted through the AV node. Atria...
...No relationship between the P wave and...
...in conduction through the bundle of His...
...travels slowly through the blocked side. 12-lead...
...their effects during the slow and fast...
...are summarized in the box called “Related...
...impulse conduction through the atria, ventricles, and...
...atria, ventricles, and the bundle of His....
...automaticity and prolonging the refractory period of...
...refractory period of the heart. They are...
...are indicated in the treatment of supraventricular...
...used chiefly in the treatment of ventricular...
...II agents block the effects of catecholamines...
...(1) Most of the class II agents...
...II drugs decrease the heart rate, the...
...the heart rate, the heart rate might...
...repolarization and prolonging the refractory period. They...
...period. They increase the fibrillation threshold (making...
...fibrillation threshold (making the cell more resistant)...
...threshold (making the cell more resistant) and...
...are indicated in the treatment of atrial...
...These drugs block the entry of calcium...
...of calcium through the cell membranes, thereby...
...calcium through the cell membranes, thereby decreasing...
...depolarization. Automaticity in the SA node is...
...not fit within the four major classes....
...any antiarrhythmic agent, the nurse assesses the...
...the nurse assesses the following baseline data:...
...ECG interpretation using the seven-step process b)...
...Physical assessment of the cardiac, respiratory, and...
...is synchronized with the patient’s heart rhythm....
...In preparation for the procedure, the nurse...
...for the procedure, the nurse obtains informed...
...consent and educates the patient as to...
...patient as to the purpose of the...
...the purpose of the cardioversion and what...
...again depending on the type of defibrillator...
...II Agents Block the effects of catecholamines....
...electrical stimulus to the heart when the...
...the heart when the heart fails to...
...cardiac output. a) The pulse generator is...
...electrical stimulus to the heart when necessary....
...exists: failure of the conduction system, failure...
...electric impulses to the myocardium transthoracically through...
...and posteriorly on the chest. b) This...
...painful experience for the patient, who should...
...medicated accordingly. c) The presence of an...
...placed directly on the surface of the...
...the surface of the heart. b) Affixed...
...b) Affixed to the epicardium, the pacing...
...to the epicardium, the pacing wires are...
...are brought through the skin (below the...
...the skin (below the sternum) for access....
...electrical stimulation of the right ventricular or...
...direct insertion of the pacing wire or...
...port c) When the procedure is complete,...
...proper placement of the lead wire in...
...addition to assuring the patient did not...
...experience complications from the central line placement...
...d) Caring for the transvenous pacing wire...
...tissue pocket (above the muscles and ribs,...
...and ribs, below the clavicle) in the...
...the clavicle) in the chest wall. b)...
...chest wall. b) The leads are passed...
...passed transvenously into the heart and rest...
...and rest on the endocardium. c) The...
...the endocardium. c) The generator is a...
...programmed according to the needs of the...
...the needs of the patient (Fig. 8-38)....
...Ventricle— Pacemakers have the ability to pace...
...ability to pace the atrium, the ventricle,...
...pace the atrium, the ventricle, or both...
...sequential”) chamber. 2. Atrium—The atria can also...
...be noted on the ECG rhythm strip...
...appears just before the wave. This method...
...of pacing, both the atria and the...
...the atria and the ventricles are paced...
...Spikes appear before the wave and the...
...the wave and the QRS complex on...
...QRS complex on the ECG. C. Pacemaker...
...1. Pacemakers have the capability of sensing...
...be set into the device. Pacemakers have...
...electrical events in the heart. There are...
...Pacing problems 1. The number of times...
...number of times the pacemaker fires is...
...is determined by the sensitivity setting of...
...sensitivity setting of the pacemaker. If the...
...the pacemaker. If the sensitivity is too...
...is too low, the pacemaker may not...
...may not sense the patient’s own cardiac...
...more frequently. If the sensitivity is too...
...is too high, the pacemaker is better...
...able to sense the patient’s own cardiac...
...to describe how the device functions according...
...according to where the pacing leads are...
...leads are and the mode of pacing....
...of cardiomyopathy. b) The device is a...
...Patients must understand the difference between heart...
...cardiac arrest. e) The ICD does not...
...Patient education a) The patient is taught...
...is taught that the ICD can “reorganize”...
...well as stimulate the heart. (Pacemaker action...
...care, including preparing the patient for insertion...
...electrical stimulus to the heart Used when...
...electrical stimulus to the myocardial cells Used...
...different areas of the heart. Most common...
...Classroom Activities Have the students practice identifying...
...ventricular contractions using the seven steps in...
...predisposing factors for the development of premature...
...Clinical Activities Have the students obtain ECG...
...predisposing factors for the development of ventricular...