Ch. 39 Dysrhythmias PDF

Dysrhythmias  Abnormal heart rhythms, called dysrhythmias, can directly decrease CO by changing stroke volume and heart rate (HR). Your ability to recognize normal heart rhythms and dysrhythmias is an essential nursing skill!! Definitions Cardiac Anatomy 2 upper chambers o Right and le...

Dysrhythmias  Abnormal heart rhythms, called dysrhythmias, can directly decrease CO by changing stroke volume and heart rate (HR). Your ability to recognize normal heart rhythms and dysrhythmias is an essential nursing skill!! Definitions Cardiac Anatomy 2 upper chambers o Right and left atria 2 lower chambers o Right and left ventricle 2 Atrioventricular valves (Mitral & Tricuspid) o Open with ventricular diastole o Close with ventricular systole 2 Semilunar Valves (Aortic & Pulmonic) o Open with ventricular systole o Open with ventricular diastole The Cardiovascular System Pulmonary Circulation o Unoxygenated – right side of the heart Systemic Circulation o Oxygenated – left side of the heart 1) body –> inferior/superior vena cava –> 3) right atrium –> 4) tricuspid valve –> 5) right ventricle –> 6) pulmonary arteries –> 7) lungs –> 8) pulmonary veins –> 9) left atrium –> 10) mitral or bicuspid valve –> 11) left ventricle –> 12) aortic valve –> 13) aorta –> 14) body. Anatomy Coronary Arteries How the Heat Works (YouTube video) The Conduction System SA node->Internodal pathways->AV node-> Bundle of his->Left & Right bundle branches->Purkinje fibers  → The P wave represents depolarization of the atria. → The QRS complex indicates depolarization of the ventricles and atrial repolarization → The T wave represents repolarization of the ventricles. → The U wave, if present, may represent repolarization of the Purkinje fibers, or it may be associated with hypokalemia. → The PR, QRS, and QT intervals reflect the time it takes for the impulse to travel from one area of the heart to another. Lead Placement  Reading ECG Paper Time (rate) 1. Each small square represents 0.04 seconds. o Measured on the horizontal line 2. Each large square represents 0.2 seconds. Amplitude (voltage) 3. 5 large squares = 1 second. o Measured on the vertical line 4. 300 large squares = 1 minute. Interpreting ECG Rhythm Strips The Five Step Approach 1. Heart rate Count the number of electrical impulses as represented by PQRST complexes conducted through the myocardium in 60 seconds (1 minute) ▪ Atrial rate: Count the number of P waves ▪ Ventricular rate: Count the number of QRS complexes ▪ The 6 second method ▪ Denotes a 6 second interval on EKG strip ▪ Strip is marked by 3 or 6 second tick marks on the top or bottom of the graph paper ▪ Count the number of QRS complexes occurring within the 6 second interval, and then multiply that number by 10  2. Heart rhythm Rhythm A sequential beating of the heart as a result of the generation of electrical impulses Classified as: Regular pattern: Interval between the R waves is regular Irregular pattern: Interval between the R waves is not regular Measuring a Regular Rhythm Measure the intervals between R waves (measure from R to R) If the intervals vary by less than 0.06 seconds or 1.5 small boxes, the rhythm is considered to be regular Measuring an Irregular Rhythm If the intervals between the R waves (from R to R) are variable by greater than 0.06 seconds or 1.5 small boxes, the rhythm is considered to be irregular  3. P wave P wave: 5 questions to ask 1. Are P waves present? 2. Are P waves occurring Produced when the left and right atria depolarize regularly? First deviation from the isoelectric line 3. Is there one P wave present Should be rounded and upright for every QRS complex present? 4. Are the P waves smooth, P wave is the SA node pacing or firing at regular intervals rounded, and upright in Normal Duration (sec): 0.06–0.12 appearance, or are they inverted? Source of Possible Variation: Problem in conduction within atria 5. Do all P waves look similar?  4. PR interval Measured from beginning of P wave to beginning of QRS PR interval: 3 questions to ask complex. 1. Are the PR intervals greater Measures the time interval from the onset of atrial contraction than 0.20 seconds? to onset of ventricular contraction 2. Are the PR intervals less than Normal interval is 0.12–0.20 seconds (3-5 small squares) 0.12 seconds? 3. Are the PR intervals consistent across the EKG strip? Source of Possible Variation: Problem in conduction usually in AV node, bundle of His, or bundle branches but can be in atria as well  5. QRS complex Q wave: First negative (downward) deflection after the P wave, short and narrow, not present in several leads o Normal Duration (sec): 150 bpm) o Premature Atrial Complexes (PAC’s)  Atrial Fibrillation The electrical signal that circles uncoordinated through the muscles of the atria causing them to quiver (sometimes more than 400 times per minute) without contracting. The ventricles do not receive regular impulses and contract out of rhythm, and the heartbeat becomes uncontrolled and irregular. Note the chaotic fibrillatory (f) waves (arrows) between the RS complexes. NOTE: Recorded from lead V1. What is the rate? What is the rhythm Is there a P wave before each QRS? Are P waves upright and uniform? What is the length of the PR interval? Do all QRS complexes look alike? What is the length of the QRS complexes? Atrial Fibrillation Continued Atrial fibrillation results in a decrease in CO because of ineffective atrial contractions (loss of atrial kick) and/or a rapid ventricular response (RVR). Thrombi may form in the atria because of blood stasis. An embolized clot may move through arteries to the brain, causing a stroke. Atrial fibrillation accounts for as many as 20% of all strokes. Causes Signs and Symptoms CAD Heart palpitations valvular heart disease Irregular pulse which feels too rapid or too cardiomyopathy slow, racing, pounding or fluttering hypertensive heart disease Dizziness or light-headedness HF Fainting Confusion Pericarditis Fatigue It often develops acutely with thyrotoxicosis, alcohol Trouble breathing intoxication, caffeine use, electrolyte problems, stress, and Difficulty breathing when lying down heart surgery Sensation of tightness in the chest Treatment Rate control (slow ventricular rate to 80-100 beats/minute) o Digoxin o Beta-adrenergic blockers o Calcium channel blockers ▪ Example - Verapamil (give IV if needed for quick rate control) Antithrombotic therapy Correction of rhythm o Chemical or electrical cardioversion  Atrial Flutter Atrial flutter is a coordinated rapid beating of the atria. Identified by recurring, regular, sawtooth-shaped flutter waves. Atrial flutter is the second most common tachyarrhythmia. Atrial flutter with a 4:1 conduction (4 flutter [F] waves to each QRS complex) Causes Signs and Symptoms CAD Palpitations Hypertension SOB What is the rate? mitral valve disorders Anxiety pulmonary embolus Weakness What is the rhythm? chronic lung disease Angina Syncope cor pulmonale Is there a P wave before each QRS? cardiomyopathy Are P waves upright and uniform? hyperthyroidism Use of drugs What is the length of the PR interval? Treatment Cardioversion Do all QRS complexes look alike? Anti arrhymics such as procainamide What is the length of the QRS Slow the ventricular rate by using diltiazem, verapamil, digitalis, complexes? or beta blocker Heparin to reduce incidence of thrombus formation  Paroxysmal supraventricular tachycardia (PSVT) Paroxysmal supraventricular tachycardia (PSVT), also known as supraventricular tachycardia (SVT) or atrial tachycardia, is a dysrhythmia starting in an ectopic focus anywhere above the bifurcation of the bundle of His. Usually, a PAC triggers a run of repeated premature beats What is the rate? Causes Signs and overexertion Symptoms What is the rhythm? emotional stress hypotension, deep inspiration palpitations, Is there a P wave before each and stimulants, such as caffeine and dyspnea, and QRS? tobacco. PSVT is also associated with angina Are P waves upright and uniform? rheumatic heart disease, digitalis What is the length of the PR toxicity, CAD, and cor pulmonale. interval? Treatment Do all QRS complexes look alike? Stable patient’s (asymptomatic) Vagal maneuvers What is the length of the QRS Drug management: Adenosine, (drug of choice), diltiazem, complexes? verapamil Cardioversion if unstable Administration of adenosine rapid IV push. Note that SVT is followed by a brief period of asystole before the return to normal sinus rhythm. This is a common occurrence after adenosine.  Premature Atrial Contractions (PAC’s) A premature atrial contraction (PAC) is a contraction starting from an ectopic focus in the atrium (i.e., a location other than the SA node) sooner than the next expected sinus beat. The ectopic signal starts in the left or right atrium and travels across the atria by an abnormal pathway. This creates a distorted P wave. At the AV node, it may be stopped (nonconducted PAC), delayed (lengthened PR interval), or conducted normally. If the signal moves through the AV node, in most cases it is conducted normally through the ventricles. What is the rate? Causes Signs and Symptoms Stress Palpitations What is the rhythm? Stimulants Skipped beat Is there a P wave before each QRS? Hypertension Are P waves upright and uniform? Infectious diseases Hypoxia What is the length of the PR hyperthyroidism interval? Treatment Do all QRS complexes look alike? Treatment depends on the patient’s symptoms. Withdrawal of What is the length of the QRS sources of stimulation, such as caffeine or sympathomimetic drugs (e.g. epinephrine, dopamine), may be needed. β-Blockers complexes? may be used to decrease PACs. Junctional dysrhythmias Junctional dysrhythmias start in the area of the AV node to the bundle of His known as the AV junction. They result because the SA node does not fire or the signal is blocked. When this occurs, the AV node becomes the pacemaker of the heart. The impulse from the AV node usually moves in a retrograde (backward) fashion. This produces an abnormal P wave that occurs just before or after the QRS complex or is hidden in the QRS complex. What is the rate? Causes Signs and What is the rhythm? CAD, HF, cardiomyopathy, Symptoms electrolyte imbalances, inferior Lightheadedness Is there a P wave before each QRS? MI, and rheumatic heart Palpitations Are P waves upright and uniform? disease. Certain drugs (e.g., Chest heaviness digoxin, nicotine, SOB What is the length of the PR amphetamines, caffeine) interval? Do all QRS complexes look alike? Treatment What is the length of the QRS Treatment varies according to the type of junctional complexes? dysrhythmia.  First-Degree AV Block First-degree AV block is a type of AV block in which every impulse is conducted to the ventricles, but the time of AV conduction is prolonged. After the impulse moves through the AV node, the ventricles usually respond normally. First-degree AV block with a PR interval of 0.40 sec Causes Signs and associated with increasing age Symptoms MI Patients are What is the rate? CAD asymptomatic. rheumatic fever What is the rhythm? hyperthyroidism electrolyte imbalances (e.g., Is there a P wave before each QRS? hypokalemia) Are P waves upright and uniform? vagal stimulation drugs, such as digoxin, β-blockers, What is the length of the PR calcium channel blockers, and interval? flecainide. Do all QRS complexes look alike? Treatment What is the length of the QRS There is no treatment for first-degree AV block. complexes?  Second-degree AV block Type I (Mobitz I, Wenckebach heart block) Type I second-degree AV block (Mobitz I or Wenckebach heart block) includes a gradual lengthening of the PR interval. AV conduction time is increasingly prolonged until an atrial impulse is nonconducted and a QRS complex is blocked (missing). Type I AV block most often occurs in the AV node, but it can occur in the His-Purkinje system. Second-degree AV block, type I, with progressive lengthening of the PR interval until a QRS complex is blocked. What is the rate? Causes Signs and may result from drugs, such as Symptoms What is the rhythm? digoxin or β-blockers Fainting inferior MI Dizziness Is there a P wave before each QRS? Are P waves upright and uniform? Treatment A symptomatic patient may need atropine or a What is the length of the PR interval? temporary pacemaker to increase HR, especially if the patient has had an MI. transcutaneous Do all QRS complexes look alike? pacemaker on standby. Bradycardia is more likely to What is the length of the QRS become symptomatic when hypotension, HF, or complexes? shock is present. Think of the phrase, “longer, longer, longer, drop, now you have a Wenckebach.”  Type II (Mobitz II heart block) In type II second-degree AV block (Mobitz II heart block), a P wave is nonconducted without progressive PR lengthening. This usually occurs when a block in 1 of the bundle branches is present. On conducted beats, the PR interval is constant. Type II second-degree AV block is a more serious type of block because a certain number of impulses from the SA node are not conducted to the ventricles. This occurs in ratios of 2:1, 3:1, and so on (i.e., 2 P waves to one QRS complex, 3 P waves to 1 QRS complex). Second-degree AV block, type II, with constant PR intervals and variable blocked QRS complexes. What is the rate? Causes Signs and rheumatic heart disease Symptoms What is the rhythm? CAD Is there a P wave before each QRS? anterior MI Are P waves upright and uniform? drug toxicity. What is the length of the PR Treatment interval? Transcutaneous pacing or the insertion of a Do all QRS complexes look alike? temporary pacemaker may be needed before What is the length of the QRS inserting a permanent pacemaker if the patient complexes? becomes symptomatic (e.g., hypotension, angina). Atropine is not an effective treatment.  Third-degree AV block (complete heart block) Third-degree AV block, or complete heart block, is a form of AV dissociation in which no impulses from the atria are conducted to the ventricles. The atria are stimulated and contract independently of the ventricles. The ventricular rhythm is an escape rhythm. The ectopic pacemaker may be above or below the bifurcation of the bundle of His. Third-degree AV block. Note that there is no relationship between P waves and QRS complexes. What is the rate? Causes Signs and severe heart disease, including Symptoms What is the rhythm? CAD, MI, myocarditis, Syncope from third- cardiomyopathy, degree AV block Is there a P wave before each QRS? Drugs: such as digoxin, β- may result from Are P waves upright and uniform? severe bradycardia blockers, and calcium channel blockers. or even periods of What is the length of the PR asystole. interval? Treatment Do all QRS complexes look alike? Symptomatic patients need a transcutaneous pacemaker What is the length of the QRS until a temporary transvenous pacemaker can be complexes? inserted. The use of drugs such as dopamine and epinephrine is an interim measure to increase HR and support BP until temporary pacing is started. Patients need a permanent pacemaker as soon as possible. Atropine is not an effective treatment. Ventricular Rhythms When the sinoatrial (SA) node and the AV Junctional tissues fails to generate an impulse the ventricles will assume the role of pacing the heart There is an absence of P waves because there is no atrial activity or depolarization Ventricular rhythms will display QRS complexes that are wide (greater than or equal to 0.12 seconds) and bizarre in appearance These 8 rhythms are the lethal ones if left untreated: Idioventricular rhythm (ventricular escape rhythm; rate usually >20 – 40 bpm) Agonal rhythm (20 or less bpm) Ventricular tachycardia (>150 bpm) Ventricular fibrillation Torsades de Pointes Pulseless Electrical Activity (PEA) Asystole - Cardiac Standstill  Premature Ventricular Contractions A premature ventricular contraction (PVC) is a contraction coming from an ectopic focus in the ventricles. It is the premature (early) occurrence of a QRS complex. A PVC is wide and distorted in shape compared with a QRS complex coming down the normal conduction pathway PVCs that have the same shape are unifocal PVCs. PVCs that arise from different foci appear different in shape from each other. These are multifocal PVCs. When every other beat is a PVC, the rhythm is called ventricular bigeminy. When every third beat is a PVC, it is called ventricular trigeminy. We call 2 consecutive PVCs a couplet. PVCs are associated with stimulants, such as caffeine, alcohol, nicotine, aminophylline, epinephrine, and isoproterenol. They are also associated with electrolyte imbalances, hypoxia, fever, exercise, and emotional stress. Disease states associated with PVCs include MI, mitral valve prolapse, HF, cardiomyopathy, and CAD. PVCs are usually not harmful in a patient with a normal heart. PVCs in CAD or acute MI indicate ventricular irritability. Take the patient’s apical-radial pulse rate and determine the pulse deficit, since PVCs often do not generate a sufficient ventricular contraction to result in a peripheral pulse. Treatment Assessing the patient’s hemodynamic status is important to determine if treatment with drug therapy is needed. Drug therapy includes β-blockers, lidocaine, or amiodarone.  Accelerated Idioventricular Rhythm Accelerated idioventricular arrhythmia is last-ditch effort of the ventricles to try to prevent cardiac standstill. The SA node and AV node have failed Rate usually between 40 to 100 beats per minute (bpm) Cardiac output is compromised Causes Signs and Drugs- Digitalis Symptoms What is the rate? MI Pale Metabolic imbalances Cool with mottled skin What is the rhythm? Hyperkalemia Weakness Cardiomyopathy Dizziness Is there a P wave before each QRS? Hypotension Are P waves upright and uniform? Alterations in mental status What is the length of the PR Treatment interval? In the setting of acute MI, AIVR is usually self-limiting and Do all QRS complexes look alike? well-tolerated, and it needs no treatment. If the patient What is the length of the QRS becomes symptomatic (e.g., hypotensive, chest pain), complexes? atropine is an option. Temporary pacing may be needed. Drugs that suppress ventricular rhythms (e.g., amiodarone) should not be used since they can further reduce HR.  Ventricular Tachycardia A run of 3 or more PVCs defines ventricular tachycardia (VT). It occurs when an ectopic focus fire repeatedly and the ventricle takes control as the pacemaker. Different forms of VT exist, depending on QRS configuration. Monomorphic VT (A) has QRS complexes that are the same in shape, size, and direction. Polymorphic VT occurs when the QRS complexes gradually change back and forth from one shape, size, and direction to another over a series of beats. Torsades de pointes (French for “twisting of the points”) is polymorphic VT associated with a prolonged QT interval of the underlying rhythm (B). VT may be sustained (longer than 30 seconds) or nonsustained (less than 30 seconds). The development of VT is an ominous sign. It is a life-threatening dysrhythmia because of decreased CO and the possible development of VF, which is lethal. Torsades de pointes is associated with a prolonged QT interval. Torsades usually terminates spontaneously but frequently recur and may degenerate into ventricular fibrillation. The hallmark of this rhythm is the upward and downward deflection of the QRS complexes around the baseline. What is the rate? What is the rhythm? Is there a P wave before each QRS? Are P waves upright and uniform? What is the length of the PR interval? Do all QRS complexes look alike? What is the length of the QRS complexes? Causes Signs and Symptoms Usually occurs with underlying heart Chest discomfort (angina) disease Syncope Commonly occurs with myocardial Light-headedness or dizziness ischemia or infarction Palpitations Certain medications may prolong Shortness of breath the QT interval predisposing the Absent or rapid pulse patient to ventricular tachycardia Loss of consciousness Electrolyte imbalance Hypotension Digitalis toxicity Congestive heart failure Treatment If there is no pulse, begin CPR If there is a pulse and the patient is unstable - cardiovert and begin drug therapy ▪ Amiodarone ▪ Lidocaine ▪ With chronic or recurrent VT ▪ Give antiarrhythmics ▪ Long term may need ICD placed ▪ Ablation may be used for reentry  Ventricular Fibrillation Ventricular fibrillation (VF) is a severe derangement of the heart rhythm characterized on ECG by irregular waveforms of varying shapes and amplitude. This represents the firing of multiple ectopic foci in the ventricle. Mechanically, the ventricle is simply “quivering,” with no effective contraction, and so no CO occurs. VF is a lethal dysrhythmia. Causes Signs and Symptoms AMI Loss of consciousness What is the rate? Untreated VT Absent pulse Electrolyte imbalance What is the rhythm? Hypothermia Myocardial ischemia Is there a P wave before each QRS? Drug toxicity or overdose Are P waves upright and uniform? Trauma What is the length of the PR interval? Treatment Do all QRS complexes look alike? CPR with immediate defibrillation What is the length of the QRS complexes?  Asystole Asystole is the total absence of ventricular electrical activity. Occasionally, P waves are seen. No ventricular contraction occurs because depolarization does not occur. Patients are unresponsive, pulseless, and apneic. Asystole is a lethal dysrhythmia that needs immediate treatment. VF may masquerade as asystole. Always assess the rhythm in more than 1 lead. The prognosis of a patient with asystole is extremely poor. Clinical Associations o Asystole is usually a result of advanced heart disease, a severe cardiac conduction system problem, or end-stage HF. Clinical Significance o Generally, the patient with asystole has end-stage heart disease or has a prolonged arrest and cannot be resuscitated. Pulseless Electrical Activity (PEA) Pulseless electrical activity (PEA) is a situation in which organized electrical activity is seen on the ECG, but there is no mechanical heart activity and the patient has no pulse. It is the most common dysrhythmia seen after defibrillation. Prognosis is poor unless the underlying cause is quickly identified and treated. Common causes of PEA include hypovolemia, hypoxia, metabolic acidosis, hyperkalemia, hypokalemia, hypoglycemia, hypothermia, toxins (e.g., drug overdose), cardiac tamponade, thrombosis (e.g., MI, pulmonary embolus), tension pneumothorax, and trauma. Treatment begins with CPR, followed by drug therapy (e.g., epinephrine) and intubation. Correcting the underlying cause is critical to prognosis.