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12 Atrial Dysrhythmias Fast & Easy ECGs, 2nd E – A SelfPaced Learning Program Fast & Easy ECGs, 2E 1 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Atrial Dysrhythmias • Originate in the atrial tissue or in the internodal pathways • Are among the most common types of dysrhythmias, particularly in persons older than 60 years of age Q I Fast & Easy ECGs, 2E 2 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Atrial Dysrhythmias • Believed to be caused by three mechanisms: – Enhanced automaticity – Circus reentry – Afterdepolarization I Fast & Easy ECGs, 2E 3 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Atrial Dysrhythmias • Can diminish the strength of the atrial contraction and affect ventricular filling time – This can lead to decreased cardiac output and ultimately decreased tissue perfusion I Fast & Easy ECGs, 2E 4 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Atrial Dysrhythmias • Key characteristics include: – P’ waves (if present) that differ in appearance from normal sinus P waves – Abnormal, shortened, or prolonged P’R intervals – QRS complexes that appear narrow and normal I Fast & Easy ECGs, 2E 5 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Premature Atrial Complexes (PACs) • Early beats that originate outside the SA node before it has a chance to depolarize Fast & Easy ECGs, 2E 6 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Premature Atrial Complexes (PACs) • Produce an irregularity in the rhythm – P’-P and R’-R intervals are shorter than the P-P and R-R intervals of underlying rhythm • Have P’ waves that are upright (in lead II) preceding each QRS complex but have a different morphology (appearance) than the P waves of underlying rhythm • Followed by a noncompensatory pause Fast & Easy ECGs, 2E 7 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Noncompensatory Pause • Is a pause where there are less than two full R-R intervals between the R wave of the normal beat which precedes the PAC and the R wave of the first normal beat which follows it I Fast & Easy ECGs, 2E 8 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Causes of PACs • Most common cause of PACs is enhanced automaticity • Other causes include: I Fast & Easy ECGs, 2E 9 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Effect of PACs • Isolated PACs seen in patients with healthy hearts are considered insignificant • Asymptomatic patients usually only require observation I Fast & Easy ECGs, 2E 10 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Effect of PACs • May predispose patient with heart disease to more serious atrial dysrhythmias: – atrial tachycardia – atrial flutter – atrial fibrillation • Can serve as an early indicator of an electrolyte imbalance or congestive heart failure in patients experiencing an acute myocardial infarction Fast & Easy ECGs, 2E 11 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Grouping of PACs • PACs can be described by how they are intermingled among normal beats Bigeminal Every other beat is a PAC Trigeminal Every 3rd beat is a PAC Quadrigeminal Every 4th beat is a PAC Fast & Easy ECGs, 2E Q 12 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Aberrantly Conducted PAC • Occurs when a PAC travels through the ventricular conduction pathway abnormally resulting in an abnormal looking QRS complex – For this reason they can be confused with PVCs I Fast & Easy ECGs, 2E 13 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Blocked PAC • Occurs when an atrial impulse arrives too early, before the AV node has a chance to repolarize • As a result, the P’ wave fails to conduct to the ventricles • Identified by a premature P’ wave that is not followed by a QRS complex Fast & Easy ECGs, 2E 14 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of PACs • Generally do not require treatment • PACs caused by the use of caffeine, tobacco, or alcohol or by anxiety, fatigue, or fever can be controlled by eliminating the underlying cause • Frequent PACs may be treated with drugs that increase the atrial refractory time – This includes beta-adrenergic blockers and calcium channel blockers Fast & Easy ECGs, 2E 15 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Wandering Atrial Pacemaker • Pacemaker site shifts between SA node, atria and/or AV junction – This produces its most characteristic feature – P’ waves that change in appearance I Fast & Easy ECGs, 2E 16 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Causes of Wandering Atrial Pacemaker • Generally caused by inhibitory vagal effect of respiration on SA node and AV junction • Other causes include the following: Fast & Easy ECGs, 2E 17 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Effects of Wandering Atrial Pacemaker • Wandering atrial pacemaker is rarely serious, having no effect on cardiac output • Normal finding in children, older adults, and well-conditioned athletes Fast & Easy ECGs, 2E 18 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Wandering Atrial Pacemaker • No treatment is necessary for patients experiencing wandering atrial pacemaker – However, chronic dysrhythmias are a sign of heart disease and should be monitored Fast & Easy ECGs, 2E 19 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Atrial Tachycardia • Rapid dysrhythmia (rate of 150 to 250 BPM) that arises from the atria • Rate is so fast it overrides the SA node I Fast & Easy ECGs, 2E 20 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Causes of Atrial Tachycardia • Digitalis toxicity is the most common cause of atrial tachycardia • Also, sudden onset atrial tachycardia is common in patients who have Wolff-ParkinsonWhite syndrome • Other causes include: Fast & Easy ECGs, 2E 21 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Effects of Atrial Tachycardia • Symptoms can develop abruptly and may go away without treatment • Short bursts are well-tolerated in otherwise normally healthy people • Alternatively, they may last a few minutes or as long as one to two days, sometimes continuing until treatment is delivered • With the rapid heartbeat seen with atrial tachycardia, there is less time for the ventricles to fill. – This can reduce stroke volume and lead to decreased cardiac output Fast & Easy ECGs, 2E 22 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Effects of Atrial Tachycardia • Can significantly compromise cardiac output in patients with underlying heart disease • Fast heart rates increase oxygen requirements – May increase myocardial ischemia and potentially lead to myocardial infarction I Fast & Easy ECGs, 2E 23 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Atrial Tachycardia with Block • Due to the rapid atrial rates seen with atrial tachycardia, the AV junction is sometimes unable to carry all the impulses – This is called atrial tachycardia with block • This then results in more than one P’ wave preceding each QRS complex • Most commonly, only one of every two beats (a 2 to 1 block) is conducted to the ventricles Fast & Easy ECGs, 2E I 24 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Atrial Tachycardia • Treatment is dependent on the type of tachycardia and symptom severity – Directed at eliminating the cause and decreasing ventricular rate. – Patients who are symptomatic (e.g., chest pain, hypotension) should receive oxygen, an IV infusion of normal saline administered at a keep-open rate, and prompt delivery of synchronized cardioversion, use of vagal maneuvers or medication administration. Fast & Easy ECGs, 2E 25 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Atrial Tachycardia • Synchronized cardioversion is indicated if the patient is symptomatic – In the conscious patient, consider sedation before cardioversion • However, do not delay cardioversion – If this fails to convert the rhythm, the energy level may be increased I Fast & Easy ECGs, 2E 26 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Atrial Tachycardia • If the patient is stable, vagal maneuvers and drug therapy (adenosine) may be used • If these treatments fail to resolve the tachycardia, calcium channel blockers (verapamil, diltiazem) and beta-adrenergic blockers (if no contraindications exist) may be considered I Fast & Easy ECGs, 2E 27 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Atrial Tachycardia • Atrial overdrive pacing may be employed to stop this dysrhythmia • If the dysrhythmia is related to WPW syndrome, catheter ablation may be indicated • Procainamide, amiodarone, or sotalol may be considered in wide complex tachycardias Fast & Easy ECGs, 2E 28 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Multifocal Atrial Tachycardia (MAT) • Pathological condition that presents with changing P wave morphology and heart rates of 120 to 150 BPM I Fast & Easy ECGs, 2E 29 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Appearance of Multifocal Atrial Tachycardia (MAT) • MAT is often misdiagnosed as atrial fibrillation with rapid ventricular response but can be identified by looking closely for clearly visible but changing P’ waves – P’ waves change in morphology as often as from beat to beat resulting in three or more differentlooking P waves • Varying PR intervals and narrow QRS complexes also seen Fast & Easy ECGs, 2E 30 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Causes of Multifocal Atrial Tachycardia (MAT) • Is more common in the elderly • It is usually precipitated by acute exacerbation (with resultant hypoxia) of COPD, elevated atrial pressures, or heart failure • Other causes include: Fast & Easy ECGs, 2E 31 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Effects of Multifocal Atrial Tachycardia (MAT) • Patient may complain of palpitations • Signs and symptoms of decreased cardiac output, such as hypotension, syncope, and blurred vision, may be seen Fast & Easy ECGs, 2E 32 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Multifocal Atrial Tachycardia (MAT) • Appropriate therapy is treatment of the underlying condition • In symptomatic patients treatment may include administering calcium channel blockers (verapamil, diltiazem) – Beta-adrenergic blockers are typically contraindicated because of the presence of severe underlying pulmonary disease Fast & Easy ECGs, 2E 33 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Supraventricular Tachycardia (SVT) • Arises from above the ventricles but cannot be definitively identified as atrial or junctional tachycardia because the P’ waves cannot be sufficiently seen Fast & Easy ECGs, 2E 34 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Supraventricular Tachycardia (SVT) • This group of tachycardias includes paroxysmal SVT (PSVT), nonparoxysmal atrial tachycardia, MAT, AV nodal reentrant tachycardia (AVNRT), atrioventricular reentrant tachycardia, and junctional tachycardia Fast & Easy ECGs, 2E 35 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Supraventricular Tachycardia (SVT) • Sometimes wide QRS complexes are seen – Due to an intraventricular conduction defect or other condition such as aberrant conduction – Makes assessment of SVT difficult as it appears to be ventricular tachycardia • Called wide complex tachycardia of unknown origin Fast & Easy ECGs, 2E 36 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Atrial Flutter • Results from circus reentry – Impulse from SA node circles back through atria, returning to the SA node region and repeatedly restimulating the AV node over and over at a rate of 250 to 350 BPM Fast & Easy ECGs, 2E 37 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Appearance of Atrial Flutter • On the ECG, the P waves lose their distinction due to the rapid atrial rate • Waves blend together in a saw-tooth or picket fence pattern called flutter waves, or F waves – Produces atrial waveforms that have a characteristic saw-tooth appearance called flutter waves (F waves) Fast & Easy ECGs, 2E 38 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Causes of Atrial Flutter • Usually caused by conditions that elevate atrial pressures and enlarge the atria • Another cause is increased automaticity • Other causes include: Fast & Easy ECGs, 2E 39 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Effects of Atrial Flutter • Often well-tolerated • The number of impulses conducted through the AV node determines the ventricular rate (i.e. 3:1 conduction ratio) – Slower ventricular rates (< 40 BPM) or faster ventricular rates (> 150 BPM) can seriously compromise cardiac output I Fast & Easy ECGs, 2E 40 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Atrial Flutter • Vagal maneuvers may make flutter waves more visible by transiently increasing the degree of the block • In patients experiencing an associated rapid ventricular rate who are symptomatic but stable, treatment is directed at controlling the rate or converting the rhythm to sinus rhythm Fast & Easy ECGs, 2E 41 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Atrial Flutter • Symptomatic patients (e.g., hypotension, signs of shock, or heart failure) should receive oxygen, an IV infusion of normal saline administered at a keep-open (TKO) rate, and prompt treatment • Synchronized cardioversion should be considered in unstable patients – If necessary, the energy may be increased with subsequent shocks Fast & Easy ECGs, 2E 42 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Atrial Fibrillation • Results for chaotic, asynchronous firing of multiple areas within the atria I Fast & Easy ECGs, 2E 43 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Appearance of Atrial Fibrillation • Totally irregular rhythm with no discernible P waves – Instead there is a chaotic baseline of fibrillatory waves (f waves) representing atrial activity Fast & Easy ECGs, 2E 44 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Causes of Atrial Fibrillation • Atrial fibrillation is more common than atrial tachycardia or atrial flutter • It can occur in healthy persons after excessive caffeine, alcohol, or tobacco ingestion or because of fatigue and acute stress • Other causes include: Fast & Easy ECGs, 2E 45 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Effects of Atrial Fibrillation • Leads to loss of atrial kick decreasing cardiac output by up to 25% • Patients may develop intra-atrial emboli as the atria are not contracting and blood stagnates in the atrial chambers forming a thrombus (clot) – Predisposes patient to systemic emboli (stroke) Fast & Easy ECGs, 2E 46 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Atrial Fibrillation • If the rate of ventricular response is normal, the dysrhythmia is usually well tolerated and requires no immediate intervention • Patients experiencing atrial fibrillation and an associated rapid ventricular rate who are symptomatic but stable, treatment is directed at controlling the rate or converting the rhythm to sinus rhythm Fast & Easy ECGs, 2E 47 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Treatment of Atrial Fibrillation • Symptomatic patients (e.g., hypotension, signs of shock, or heart failure) should receive oxygen, an IV infusion of normal saline administered at a TKO rate, and prompt synchronized cardioversion – If necessary, the energy level may be increased with subsequent shocks Fast & Easy ECGs, 2E 48 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 49 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 50 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 51 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 52 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 53 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 54 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 55 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 56 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 57 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect • Determine the type of dysrhythmia I Fast & Easy ECGs, 2E 58 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary • Atrial dysrhythmias originate outside the SA node in the atrial tissue or in the internodal pathways • Three mechanisms responsible for atrial dysrhythmias are increased automaticity, triggered activity and reentry • Key characteristics for atrial dysrhythmias: – P’ waves (if present) that differ from sinus P waves – Abnormal, shortened, or prolonged P’R intervals – QRS complexes that appear narrow and normal (unless there is an intraventricular conduction defect, aberrancy or preexcitation) Fast & Easy ECGs, 2E 59 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary • With wandering atrial pacemaker the pacemaker site shifts between the SA node, atria and/or AV junction – Produces its most characteristic feature, P’ waves that change in appearance • Premature atrial complexes (PACs) are early ectopic beats that originate outside the SA node – Produce an irregularity in the rhythm – P’ waves should be an upright (in lead II) preceding the QRS complex but has a different morphology than the P waves in the underlying rhythm Fast & Easy ECGs, 2E 60 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary • Atrial tachycardia is a rapid dysrhythmia (rate of 150 to 250 beats per minute) that arises from the atria • Multifocal atrial tachycardia (MAT) is a pathological condition that presents with the same characteristics as wandering atrial pacemaker but has heart rates of 120 to 150 beats per minute • Supraventricular tachycardia arises from above the ventricles but cannot be definitively identified as atrial or junctional because the P’ waves cannot be seen with any real degree of certainty Fast & Easy ECGs, 2E 61 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary • Atrial flutter is a rapid depolarization of a single focus in the atria at a rate of 250 to 350 beats per minute – Produces atrial waveforms that have a characteristic saw-tooth or picket fence appearance • Atrial fibrillation occurs when there is chaotic, asynchronous firing of multiple areas within atria at a rate greater than 350 beats per minute – Produces a totally irregular rhythm with no discernible P waves Fast & Easy ECGs, 2E 62 © 2013 The McGraw-Hill Companies, Inc. All rights reserved.