Atrial Dysrhythmias

12 Atrial Dysrhythmias Fast & Easy ECGs, 2nd E – A Self-Paced Learning Program

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

Atrial Dysrhythmias • Believed to be caused by three mechanisms: • Enhanced automaticity • Circus reentry • Afterdepolarization I

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

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

Premature Atrial Complexes (PACs) • Early beats that originate outside the SA node before it has a chance to depolarize

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

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

Causes of PACs • Most common cause of PACs is enhanced automaticity • Other causes include: I

Effect of PACs • Isolated PACs seen in patients with healthy hearts are considered insignificant • Asymptomatic patients usually only require observation I

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

Grouping of PACs Bigeminal • PACs can be described by how they are intermingled among normal beats Every other beat is a PAC Trigeminal Every 3rd beat is a PAC Quadrigeminal Every 4th beat is a PAC Q

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

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

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

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

Causes of Wandering Atrial Pacemaker • Generally caused by inhibitory vagal effect of respiration on SA node and AV junction • Other causes include the following:

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

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

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

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-Parkinson-White syndrome • Other causes include:

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

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

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 I

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.

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

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

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

Multifocal Atrial Tachycardia (MAT) • Pathological condition that presents with changing P wave morphology and heart rates of 120 to 150 BPM I

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 different-looking P waves • Varying PR intervals and narrow QRS complexes also seen

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:

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

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

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

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

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

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

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)

Causes of Atrial Flutter • Usually caused by conditions that elevate atrial pressures and enlarge the atria • Another cause is increased automaticity • Other causes include:

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

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

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

Atrial Fibrillation • Results for chaotic, asynchronous firing of multiple areas within the atria I

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

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:

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)

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

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

Practice Makes Perfect • Determine the type of dysrhythmia I

Atrial Dysrhythmias