Interventions for Clients with Dysrhythmias

1. Interventions for Clients with Dysrhythmias

2. Cardiac dysrhythmias are disturbances of cardiac electrical impulse formation, conduction, or both

3. Review of Cardiac Electrophysiology • Automaticity (spontaneous depolarization) is the ability of cardiac cells to generate an electrical impulse spontaneously and repetitively. Normally, only primary pacemaker cells possess this property. Under certain conditions, such as myocardial ischemia (decreased blood flow) and infarction (cell death), any cardiac cell may exhibit this property, generating electrical impulses independently and creating dysrhythmias • Excitability is the ability of nonpacemaker cardiac cells to respond to an electrical impulse generated from pacemaker cells and to depolarize. Depolarization occurs when the normally negatively charged cells develop a positive charge • Conductivity is the ability to transmit an electrical stimulus from cell membrane to cell membrane. Consequently, ex­citable cells depolarize in rapid succession from cell to cell until all cells have depolarized. This wave of depolarization gives rise to the deflections of the electrocardiogram (ECG) waveforms that are recognized as the P wave and the QRS complex

4. Review of Cardiac Electrophysiology • Contractility is the ability of atrial and ventricular muscle cells to shorten their fiber length in response to electricalstimulation, generating sufficient pressure to propel blood forward. This is the mechanical activity of the heart • Action potential – The cardiac cell membrane (sarcolemma) exhibits selective permeability to ions. An ion is an electrically charged particle. This creates an electrical imbalance, known as an action po­tential, across the cell membrane. The cardiac cell at rest has an internal negative charge, whereas the charge outside the cell is positive. This state of electrical imbalance of the resting cell is called resting membrane potential

5. Cardiac Conduction System • Sinoatrial node • Electrical impulses at 60 to 100 beats/min • Atrioventricular junctional area • Bundle branch system

7. Electrocardiography • Electrocardiogram (ECG) - provides a graphic represen­tation, or picture, of cardiac activity • A lead provides one view of the heart's electrical activity. Multiple leads, or views, can be obtained. Electrode placement is the same for male and female clients. • Lead systems are made up of a positive pole and a negative pole. An imaginary line joining these two poles is called the lead axis. • The direction of electrical current flow in the heart is the cardiac axis. • The relationship between the cardiac axis and the lead axis is responsible for the deflections seen on the ECG pattern

8. Electrocardiography • Limb leads • Standard bipolar limb leads consist of three leads that each measure the electrical activity between two points, and a fourth lead (right leg) that acts solely as a ground electrode. Of the three measuring leads, the right arm is always negative, the left leg is always positive, and the left arm can be either positive or negative. • Bipolar leads can be obtained by using a monitor with either three or five electrode cables or a 12-lead ECG machine. • Leads I, II, and III are bipolar leads. • Unipolar limb leads consist of a positive electrode only. • These leads can be obtained only by using a monitor with four or five electrode cables or a 12-lead ECG machine. The unipolar limb leads are aVR, aVL, and aVF, with a meaning augmented. V is a designation for a unipolar lead. The third letter denotes the positive electrode placement: R for right arm, L for left arm, and F for foot (left leg). • The positive electrode is at one end of the lead axis. The other end is the center of the electrical field, at approximately the center of the heart

9. Electrocardiography • Chest leads • Chest (precordial) leads are also unipolar, or V, leads and therefore can be obtained only from a monitor with five electrode cables or a 12-lead ECG machine, which usually has 10 electrode cables. • There are six chest leads, determined by the placement of the chest electrode. • The four limb electrodes are placed on the extremities, as designated on each electrode (right arm, left arm, right leg, and left leg). • The fifth (chest) electrode on a monitor system is the positive, or exploring, electrode and is placed in one of six designated positions to obtain the desired chest lead. • With a 12-lead ECG, four leads are placed on the limbs and six are placed on the chest, eliminating the need to move any electrodes about the chest

10. Electrocardiography • Continuous electrocardiographic monitoring • For continuous electrocardiographic (ECG) monitoring, the electrodes are not placed on the limbs, because movement of the extremities causes "noise," or motion artifact, on the ECG signal. The nurse places the electrodes on the trunk, a more stable area, to minimize such artifacts and to obtain a clearer signal. The nurse places the electrodes as follows: • Right arm electrode just below the right clavicle • Left arm electrode just below the left clavicle • Right leg electrode on the lowest palpable rib, on the right midclavicular line • Left leg electrode on the lowest palpable rib, on the leftmidclavicular line • Fifth electrode placed to obtain one of the six chest leads • With this placement, the monitor lead select control may be changed to provide lead I, II, III, aVR, aVL, or aVF or one chest lead. The monitor automatically alters the polarity of the electrodes to provide the lead selected

11. Electrocardiography • Telemetry • ECG cables may be attached directly to a wall-mounted monitor (a hard-wired system) if the client's activity is restricted to bedrest and sitting in a chair, as in a critical care unit. • For an ambulatory client, the ECG cable is attached to a battery-operated transmitter (a telemetry system) held in a pouch worn by the client. • The ECG is transmitted via antennae located in strategic places, usually in the ceiling, to a remote monitor. This device allows freedom of movement within a certain radius without losing transmission of the ECG

15. Electrocardiographic Complexes, Segments, and Intervals • P wave • PR segment • PR interval - it normally measures from 0.12 to 0.20 second • QRS complex • QRS duration - it normally measures from 0.04 to 0.10 second • ST segment - it is normally not elevated more than 1 mm or depressed more than 0.5 mm from the isoelectric line. Its amplitude is measured at a point 1.5 to 2 mm after the J-point • T wave • U wave • QT interval

17. Electrocardiographic Rhythm Analysis

18. Normal Rhythms • Normal sinus rhythm - is the rhythm originating from the sinoatrial (SA) node (dominant pacemaker) that meets the following electrocardiographic (ECG) criteria: • Rhythm: Atrial and ventricular rhythms regular • Rate: Atrial and ventricular rates of 60 to 100 beats/min • P waves: Present, consistent configuration, one P wavebefore each QRS complex • PR interval: 0.12 to 0.20 second and constant • QRS duration: 0.04 to 0.10 second and constant

20. Normal Rhythms • Sinus arrhythmia • Sinus arrhythmia is a variant of NSR. It results from changes in intrathoracic pressure during breathing. • In this context the term arrhythmia does not denote an absence of rhythm, as the term suggests. • Instead, the heart rate increases slightly during inspiration and decreases slightly during exhalation

21. Dysrhythmias • Tachydysrhythmias - are heart rates greater than 100 beats/min • Bradydysrhythmias - are characterized by a heart rate less than 60 beats/min • Premature complexes - are early complexes. They occur when a cardiac cell or cell group, other than the sinoatrial (SA) node, becomes irritable and fires an impulse before the next sinus impulse is generated. This abnormal focus is called an ectopic focus and may be generated by atrial, junctional, or ventricular tissue

22. Dysrhythmias • Repetitive rhythms - premature complexes may occur repetitively in a rhythmic fashion • bigeminy exists when normal complexes and premature complexes occur alternately in a repetitive two-beat pattern, with a pause occurring after each premature complex so that complexes occur in pairs. • trigeminy is a repetitive three-beat pattern, usually occurring as two sequential normal complexes followed by premature complex and a pause, with the same pattern repeating itself in triplets. • quadrigeminy - is a repetitive four-beat pattern, usually occurring as three sequential normal complexes fol­lowed by a premature complex and a pause, with the same pattern repeating itself in a four-beat pattern • Escape complexes and rhythms - occur when the SA node fails to discharge or is blocked or when a sinus impulse fails to depolarize the ventricles because of an atrioventricular (AV) nodal block

23. Sinus tachycardia • When the rate of SA node discharge exceeds 100 beats/min • Clinical manifestations - the client may be asymptomatic except for the in­creased pulse rate. However, if the rhythm is not well tolerated, he or she may become symptomatic. The client is assessed for fatigue, weakness, shortness of breath, orthopnea, neck vein distention, decreased oxygen saturation, and decreased blood pressure. The nurse also assesses for restlessness and anxiety from decreased cerebral perfusion and for decreased urine output from decreased renal perfusion. The adult client may experience anginal pain. The electrocardiographic (ECG) pattern may show T-wave inversion or ST-segment elevation or depression in response to myocardial ischemia

24. Sinus tachycardia (heart rate, 110 beats/min; PR interval, 0.12 second; QRS complex, 0.08 second)

25. Sinus tachycardia • Interventions • The goal is to decrease the heart rate to normal levels by treating the underlying cause. • For example, if the client has angina, the nurse administers oxygen, helps the client to rest, and administers nitroglycerin or morphine as prescribed. • Diuretics and inotropic agentsmay be given for heart failure. The nurse initiates intravascular volume replacement for hypovolemia, administers antipyretics and antibiotics to the client with fever and infection, or provides comfort measures and administers analgesics or opioids to the client with noncardiac pain, as ordered. • The nurse collaborates with the respiratory therapist when indicated to oxygenate and suction the client with hypoxemia from excessive airway secretions. • Beta-adrenergic blocking agents may be prescribed for the client with inappropriate sympathetic nervous system stimulation. • Emotional support and relevant teaching are important for the client and family

26. Sinus Bradycardia • Rate of sinus node discharge < 60 beats/min • Clinical manifestations - the client may be asymptomatic, except for the decreased pulse rate. However, at times the rhythm may not be well tolerated. The nurse assesses the client for dizziness, weakness, syncope, confusion, hypotension, diaphoresis, shortness of breath, ventricular ectopy, and anginal pain

27. Sinus bradycardia (heart rate, 52 beats/min; PR interval, 0.18 sec­ond; QRS complex, 0.08 second)

28. Sinus Bradycardia • Interventions • If the client is symptomatic and the underlying cause cannot be determined, the treatment of choice is atropine administration, given as prescribed to increase the heart rate to approximately 60 beats/min. • Oxygen should be applied. If the heart rate does not increase sufficiently, the nurse may apply an external pacemaker to increase the heart rate and notify the physician. • However, if atropine administration succeeds in achieving an adequate heart rate but the client remains hypotensive, the nurse initiates intravascular volume replacement, as ordered, rather than administering another dose of atropine. Excessive atropine may induce tachycardia

29. Premature Atrial Complexes • Ectopic focus of atrial tissue fires an impulse before the next sinus impulse is due. • Clinical manifestations - the client is usually asymptomatic, except for possible heart palpitations, because PACs usually have no hemodynamic consequences • Interventions - no intervention is usually needed except to treat the cause, such as heart failure or valvular disease. The nurse administers prescribed type antidysrhythmics, such as quinidine and procainamide (Pronestyl), or other drugs such as digitalis and propranolol (Inderal, Apo-Propranolol). Measures to reduce stress are also initiated, and the client is taught to avoid substances known to increase atrial irritability

30. Normal sinus rhythm with a premature atrial complex (PAC) at arrow

31. Supraventricular Tachycardia • Rapid stimulation of atrial tissue occurs at a rate of 100 to 280 beat/min with a mean of 170 beats/min in adults. • Paroxysmal supraventricular tachycardia rhythm is intermittent and terminated suddenly with or without intervention.

32. Sustained supraventricular tachycardia in a client with Wolff-Parkinson-White syndrome. Heart rate is 200 beats/min

33. Supraventricular Tachycardia • Clinical manifestations - the clinical manifestations depend on the duration of the SVT and the rate of the ventricular response. In clients with a sustained rapid ventricular response, the nurse assesses for palpitations, weakness, fatigue, shortness of breath, nervousness, anxiety, hypotension, and syncope. Hemodynamic deterioration may occur in the client with cardiac disease, causing angina, heart failure, and shock. With a nonsustained or slower ventricular response, the client may be asymptomatic except for transient palpitations

34. Supraventricular Tachycardia • Interventions • If SVT occurs in a healthy person and terminates spontaneously, no intervention is necessary other than eliminating identified causative factors. • If it is recurrent, the client should be studied in the electrophysiology laboratory. The preferred treatment for recurrent SVT is radiofrequency catheter ablation. In sustained SVT with a rapid ventricular response, the goals of treatment are to decrease the ventricular response, convert the dysrhythmia to a sinus rhythm, and treat the cause. Vagal stimulation (e.g., carotid massage) may be successful, but often only transiently, and must be performed only by a physician. • The nurse administers oxygen and prescribed antidysrhythmic drugs, which slow the ventricular rate by increasing the AV block. • In the severely compromised client, the nurse may assist the physician in attempting atrial overdrive pacing or in delivering a synchronized electrical shock (cardioversion) to reestablish an organized rhythm and regain cardiac stability

35. Atrial Flutter • Rapid atrial depolarization occurring at a rate of 250 to 350 times per minute • Clinical manifestations - the clinical manifestations depend on the rate of ventricular response. The nurse assesses the client for palpitations, weakness, fatigue, shortness of breath, nervousness, anxiety, syncope, angina, and evidence of heart failure and shock. Carotid sinus massage transiently decreases the ventricular rate to facilitate rhythm interpretation but can be performed only by the physician. The client with a normal ventricular rate is usually asymptomatic

36. Atrial flutter (F) with 4:1 block. The atrial rate is 280 beats/min; the ventricular rate is 70 beats/min Atrial flutter with 4:1 conduction, then an 11-beat run with 2:1 conduction

37. Atrial Flutter • Interventions • The treatment goals are the same as those for supraventricular tachycardia (SVT). The nurse administers oxygen and prescribed drugs such as ibutilide (Covert), amiodarone (Cordarone), diltiazem (Cardizem), and verapamil (Calan, Isoptin) to slow the rapid ventricular response. • Quinidine or procainamide (Pronestyl) must not be administered unless one of the above agents has slowed the ventricular response. Both drugs slow the atrial rate and may increase AV conduction, which could cause a 1:1 conduction with an increase in ventricular rate and hemodynamic deterioration. • The nurse helps the physician to attempt rapid atrial overdrive pacing or to achieve cardioversion if the client is hemodynamically compromised. If he or she fails to respond to these therapies, radiofrequency catheter ablation may be necessary

38. Atrial Fibrillation • Multiple, rapid impulses from many atrial foci at a rate of 350 to 600 times per minute

39. Atrial Fibrillation • Clinical manifestations • The nurse assesses the client for the presence of a pulse deficit, fatigue, weakness, shortness of breath, distended neck veins, dizziness, decreased exercise tolerance, anxiety, syncope, palpitations, chest discomfort or pain, and hypotension. • The client is also at risk for pulmonary embolism. The nurse should assess for shortness of breath, chest pain, hemoptysis, and a feeling of impending doom. • The client is at risk for systemic emboli, particularly an embolic stroke. Changes in mentation, speech, sensory function, and motor function are particularly noted. • The nurse also assesses pulses, urine output, back pain, and complaints of gastrointestinal (GI) disturbances. • Any of these symptoms should be reported to the health care provider immediately.

40. Atrial Fibrillation • Interventions • Treatment is the same as for atrial flutter. In addition, the nurse may administer anticoagulants, such as heparin, enoxaparin (Lovenox), and sodium warfarin, as prescribed by the physician for clients considered to be at high risk for emboli. • Before elective cardioversion, the nurse must initiate anticoagulation therapy for 4 to 5 weeks as prescribed to prevent a thromboembolic event if the rhythm is successfully converted

41. Junctional Dysrhythmias • Atrioventricular cells generating electrical impulses at a rate of 40 to 60 beats/min • These rhythms are most commonly transient, and clients usually remain hemodynamically stable.

42. Idioventricular Rhythm • Also called ventricular escape rhythm: ventricular nodal cells pace the ventricles. P waves are independent of the QRS complex (AV dissociation). • Clinical manifestations - because idioventricular pacemakers are unstable, unreliable, and slow, the client is hypotensive and in shock or, most typically, is pulseless and therefore in cardiac arrest. The nurse assesses the client's airway, breathing, circulation, level of consciousness, and pupillary response • Interventions - usually, idioventricular rhythms require immediate resuscitation measures, unless there is a do-not-resuscitate (DNR) order. The nurse initiates cardiopulmonary resuscitation (CPR) and summons assistance. The team may initiate advanced cardiac life support (ACLS) measures, including epinephrine administration, intravascular volume replacement, and other measures. The physician may attempt pacemaker therapy or discontinue resuscitation efforts

43. Idioventricular rhythm with a rate of 35 beats/min

44. Premature Ventricular Complexes • A result of increased irritability of ventricular cells: early ventricular complexes followed by a pause

45. Ventricular dysrhythmias. A, Normal sinus rhythm with unifocal premature ventricular complexes (PVCs). B, Normal sinus rhythm with multifocal PVCs (one negative and the other positive). C, Normal sinus rhythm with three consecutive PVCs (nonsustained ventricular tachycardia) and another unifocal PVC

46. Premature Ventricular Complexes • Clinical manifestations • The client may be asymptomatic or may experience palpitations or chest discomfort caused by increased stroke volume of the normal beat after the pause. Peripheral pulses may be diminished or absent with the PVCs themselves because the decreased stroke volume of the premature beats may decrease peripheral perfusion. Since other rhythms also cause widened QRS complexes, it is essential that the nurse assess whether the premature complexes perfuse. This is done by palpating the carotid, brachial, or femoral arteries while observing the monitor for widened complexes, or auscultating for the apical heart sounds. With acute myocardial infarction, PVCs may be considered warning dysrhythmias, possibly heralding the onset of ventricular tachycardia (VT) or ventricular fibrillation (VF). For a client with chest discomfort or pain, the nurse reports to the physician whether PVCs increase in frequency, are multiform, are R-on-T phenomena, or occur in runs of VT

47. Premature Ventricular Complexes • Interventions • If there is no underlying heart disease, PVCs are not usually treated other than by eliminating any contributing cause (e.g., caffeine, stress). • With acute myocardial ischemia or infarction, the nurse treats significant PVCs by administering oxygen and lidocaine as prescribed. • The nurse may administer other drugs as ordered, including procainamide (Pronestyl), bretylium (Bretylol, Bretylate), magnesium sulfate, propranolol (Inderal, Apo-Propranolol), quinidine, and mexiletine (Mexitil). • Potassium is administered as ordered for replacement therapy if hypokalemia is the cause

48. Ventricular Tachycardia • Also called V tach: repetitive firing of an irritable ventricular ectopic focus, usually at a rate of 140 to 180 beats/min • Clinical manifestations • Slower rates are better tolerated. Clients may be hemodynamically compromised if the cardiac output decreases because of the shortened ventricular filling time and loss of the atrial kick. In some clients, VT causes cardiac arrest. The nurse assesses the client's airway, breathing, circulation, level of consciousness, and pupillary response

49. Ventricular dysrhythmias. Sustained ventricular tachycardia at a rate of 166 beats/min

50. Ventricular Tachycardia • Interventions • For the stable client with sustained VT, the nurse administers oxygen and confirms the rhythm via a 12-lead electrocardiogram (ECG). Amiodarone, procainamide, or magnesium sulfate may be given. • The physician may prescribe an oral antidysrhythmic agent, such as procainamide (Procan SR), mexiletine (Mexitil), or sotalol (Betapace, Sotacor). • For the client with unstable VT, the nurse assists the physician in attempting emergency cardioversion followed by oxygen and antidysrhythmic therapy. The nurse may instruct the client to perform cough cardiopulmonary resuscitation (CPR) if prescribed, telling him or her to inhale deeply and cough hard every 1 to 3 seconds. The physician may attempt rapid atrial or ventricular overdrive pacing if the VT is related to a significant bradydysrhythmia. • A precordial thump is sometimes successful in terminating VT, at least transiently. The physician or the nurse may administer a precordial thump to a client with unstable VT only if a defibrillator and pacemaker are immediately available.