1. Care of Patients with Dysrhythmias
Chapter 36
Care of Patients with Dysrhythmias
Automated external defibrillator with electrodes.

2. Review of Cardiac Electrophysiology
Specialized myocardial cells
Automaticity
Excitability
Conductivity
Contractility

3. Cardiac Conduction System

4. Cardiac Conduction System (cont’d)
Sinoatrial node
Electrical impulses beats/min
P wave on ECG
Atrioventricular junction
PR segment on ECG
Contraction known as “atrial kick”
Bundle of His
Right bundle branch system
Left bundle branch system

5. Electrocardiographic Waveforms
ECG waveforms are measured in amplitude (voltage) and duration (time).

6. Electrocardiographic Waveforms (cont’d)
Each segment between the dark lines (above the monitor strip) represents 3 seconds when the monitor is set at a speed of 25 mm/sec. To estimate the ventricular rate, count the QRS complexes in a 6-second strip and then multiply that number by 10 to estimate the rate for 1 minute. In this example, there are 9 QRS complexes in 6 seconds. Therefore the heart rate can be estimated to be 90 beats/min.

7. ECG Complexes, Segments, & Intervals
P wave
PR segment
PR interval
QRS complex
QRS duration
ST segment
T wave
U wave
QT interval

8. Normal ECG
The components of a normal ECG.

9. Determining Heart Rate
In this example, the heart rate using the big block method is 300 ÷ 4 big blocks (between QRS complexes), or 75 beats/min. The memory method is also demonstrated with a heart rate of 75 beats/min.

10. ECG Rhythm Analysis Determine heart rate Determine heart rhythm
Analyze P waves
Measure PR interval
Measure QRS duration
Interpret rhythm

11. Normal Sinus Rhythm
Normal sinus rhythm. Both atrial and ventricular rhythms are essentially regular (a slight variation in rhythm is normal). Atrial and ventricular rates are both 83 beats/min. There is one P wave before each QRS complex, and all the P waves are of a consistent morphology, or shape. The PR interval measures 0.18 second and is constant; the QRS complex measures 0.06 second and is constant.

12. Normal Sinus Rhythm (cont’d)
Rate: beats/min
Rhythm: regular
P waves: Present, consistent configuration, one P wave before each QRS complex
PR interval : second and constant
QRS duration: second and constant

13. Sinus Rhythms
Sinus rhythms. A, Sinus tachycardia (heart rate, 110 beats/min; PR interval, 0.12 second; QRS complex, 0.08 second). B, Sinus bradycardia (heart rate, 52 beats/min; PR interval 0.18 second; QRS complex, 0.08 second).

14. Sinus Dysrhythmias Variant of NSR
Results from changes in intrathoracic pressure during breathing

15. Sinus Bradycardia
Sinus bradycardia; heart rate, 40 beats/min.

16. Sinus Arrhythmias Sinus tachycardia
Patient-centered collaborative care

17. Sinus Tachycardia
Sinus tachycardia; heart rate, 110 beats/min.

18. Dysrhythmias Tachydysrhythmias Bradydysrhythmias Premature complexes
Repetitive rhythm complexes
Bigeminy
Trigeminy
Quadrigeminy

19. Atrial Dysrhythmias
Atrial fibrillation. Note wavy baseline with atrial electrical activity and irregular ventricular rhythm.

20. Premature Atrial Complexes
Ectopic focus of atrial tissue fires an impulse before next sinus impulse is due

21. Supraventricular Tachycardia
Rapid stimulation of atrial tissue occurs at rate of beat/min with mean of 170 beats/min (adults)
Paroxysmal supraventricular tachycardia rhythm is intermittent, terminated suddenly with or without intervention

22. Atrial Fibrillation
Associated with atrial fibrosis and loss of muscle mass
Common in heart disease such as hypertension, heart failure, coronary artery disease
Cardiac output can decrease by as much as 20% to 30%

23. Atrial Fibrillation (cont’d)
Patient-centered collaborative care
Risk for PE, VTE
Antidysrhythmic drugs
Cardioversion
Percutaneous radiofrequency catheter ablation
Bi-ventricular pacing
Maze procedure

24. Ventricular Dysrhythmias
More life-threatening than atrial dysrhythmias
Left ventricle pumps oxygenated blood through the body to perfuse vital organs and other tissues

25. Ventricular Dysrhythmias (cont’d)
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).

26. Premature Ventricular Complexes
Result of increased irritability of ventricular cells—early ventricular complexes followed by a pause

27. Ventricular Tachycardia
Also called V tach—repetitive firing of irritable ventricular ectopic focus, usually at beats/min
Sustained ventricular tachycardia at a rate of 166 beats/min.

28. Ventricular Fibrillation
Also called V fib—result of electrical chaos in ventricles
Coarse ventricular fibrillation.

29. Ventricular Asystole
Also called ventricular standstill—complete absence of any ventricular rhythm
Ventricular asystole with one idioventricular complex.

30. Atrioventricular Blocks
Differentiated by their PR interval
First-degree—all sinus impulses eventually reach ventricles
Second-degree—some sinus impulses reach ventricles, others do not
Third-degree—no sinus impulses reach ventricles

31. Dysrhythmias: Nonsurgical Management
Antidysrhythmic agents
Other drugs
Drugs used during cardiac arrest
Vagal maneuvers—carotid sinus massage, vagal reflex

32. Pacemakers Temporary pacing—invasive and noninvasive
Permanent pacemakers
Placement of a pacemaker in chest and heart leads.

33. Management of Cardiac Arrest
CPR
Maintain patent airway
Ventilate with mouth-to-mask device
Start chest compressions
Advanced cardiac life support

34. Cardioversion Synchronized countershock
Used in emergencies for unstable ventricular/supraventricular tachydysrhythmias
Used electively for stable tachydysrhythmias resistant to medical therapies

35. Defibrillation
Asynchronous countershock that depolarizes critical mass of myocardium simultaneously to stop re-entry circuit and allow sinus node to regain control of heart

36. Other Therapies Automatic external defibrillation
Radiofrequency catheter ablation
Surgical procedures:
Permanent pacemaker
Coronary artery bypass grafting
Aneurysmectomy
Implantable cardioverter/defibrillator
Open-chest cardiac massage

37. Community-Based Care Home care management Teaching for self-management
Health care resources

38. A 28-year-old woman with a history of hypertension and tachycardia comes to the hospital clinic stating that she doesn’t feel well. You connect her to a cardiac monitor and observe that she is in SVT with a rate varying between She reports shortness of breath, palpitations, and weakness. She appears very nervous and anxious, and her BP is 88/56 mm Hg. What is your first priority intervention?
Oxygen should be administered at 2 L per nasal cannula.

39. (cont’d)
Ten minutes later, the patient is still in SVT and reports substernal chest pain and dizziness.
Which action will you expect the physician to take to treat the dysrhythmia?
Administer amiodarone (Cordarone) IV push.
Instruct the patient to take several deep breaths.
Perform carotid massage.
Order a 12-lead ECG.
ANS: C
The physician may perform vagal stimulation such as carotid massage, which may be successful in terminating the dysrhythmia; however, it may only be temporarily successful.

40. (cont’d)
The patient’s SVT returns after 30 minutes. What medication do you anticipate will be ordered for the patient?
Lidocaine (Xylocaine) 75 mg IVP
Mexiletine (Mexitil) 300 mg PO q8h
Magnesium sulfate 1 g IVP
Adenosine (Adenocard) 6 mg IVP
ANS: D
The appropriate medication to administer is adenosine (Adenocard), which is the drug used for SVT. The nurse should give the medication as ordered to include 6 mg IV over 1 to 3 seconds followed by 20 mL saline flush. It may be repeated in 1 to 2 minutes if necessary. The nurse should monitor the patient’s heart rate and rhythm carefully after administration of the medication. Be sure to have the crash cart available because a short period of asystole is common after administration. Bradycardia and hypotension may also occur.

41. (cont’d)
The SVT resolves immediately after IV adenosine (Adenocard) is administered. Because the patient has experienced repeated episodes of symptomatic SVT, a cardiologist has been consulted and treatment options discussed.
What is the preferred treatment for recurrent SVT?
Atrial overdrive pacing
Radiofrequency catheter ablation
Synchronized electrical shock
Daily administration of diltiazem (Cardizem)
ANS: B
If SVT is continuous, the patient should be studied in the electrophysiology laboratory. The preferred treatment is radiofrequency catheter ablation. Radiofrequency ablation is a procedure that can cure many types of fast heart rates. Using special wires or catheters that are threaded into the heart, radiofrequency energy (low-voltage, high-frequency electricity) is targeted toward the area(s) causing the abnormal heart rhythm, permanently damaging small areas of tissue with heat. The damaged tissue is no longer capable of generating or conducting electrical impulses. If the procedure is successful, this prevents the dysrhythmia from being generated, thereby curing the patient.

42. Audience Response System Questions
Chapter 36
Audience Response System Questions 42

43. Question 1
Patients with which type of dysrhythmia make up the largest group of those hospitalized with dysrhythmias?
Sinus tachycardia
Sinus bradycardia
Ventricular fibrillation
Atrial fibrillation
Answer: D
Rationale: Atrial fibrillation (AF) is the most common dysrhythmia seen in clinical practice. It is responsible for a third of hospitalizations for cardiac rhythm disturbances. Patients can live with this dysrhythmia, but most are treated with anticoagulation therapy to avoid possible blood clots.

44. Question 2
On a telemetry monitor, the nurse observes that a patient’s heart rhythm is sustained ventricular tachycardia (VT). The nurse checks the patient and finds him alert and oriented with no reports of chest pain, but feeling slightly short of breath. His blood pressure is 108/70. What is the nurse’s first action?
Administration of oxygen and observation of the heart rhythm
Administration of IV amiodarone (Cordarone) and dextrose
Synchronized cardioversion
CPR and immediate defibrillation
Answer: A
Rationale: Current advanced cardiac life support (ACLS) guidelines recommend administration of oxygen and observation of heart rhythm first, followed by administration of an IV antidysrhythmic agent such as amiodarone mixed with dextrose 5%. Synchronized cardioversion would be the next step. CPR and immediate defibrillation would be used only to treat unstable VT.

45. Question 3
When using a 5-electrode lead ECG monitoring system, which lead is most optimal for detecting dysrhythmias?
III V1 V5
aVR
Answer: B
Rationale: Five-electrode ECG monitoring systems use four electrode leads to provide six limb lead tracings (leads I, II, III, aVR, aVL, or aVF) and the fifth electrode lead is a chest electrode that can be placed in any of the standard V1 to V6 locations. But in general, V1 is selected because of its value in detecting dysrhythmias (e.g., arrhythmia monitoring).
(Source: Accessed August 2, 2011,