IMS Atrial Dysrhythmias

Atrial Dysrhythmias

• Includes PAC (Premature Atrial Contraction or Premature Atrial Complex): Occurs when an ectopic focus in the atria fires earlier than the next expected sinus node impulse. This can be caused by stress, caffeine, tobacco, or electrolyte imbalances.

• PAT (Paroxysmal Atrial Tachycardia) and SVT (Supraventricular Tachycardia) are often used interchangeably due to similar fast heart rates. Both involve rapid heart rates originating above the ventricles.

• Clinical settings often use the term SVT more frequently, encompassing various tachycardias originating above the ventricles.

Clinical Scenario

• Patient on the fifth floor experienced SVT for six minutes, indicating a sustained episode of rapid heart rate.

• Administered adenosine IV push, converting the rhythm to rapid A-Fib, suggesting that the SVT might have been related to or triggered atrial fibrillation.

• Followed by amiodarone drip to maintain rhythm control and prevent recurrence of atrial fibrillation.

• Later converted to sinus rhythm with a heart rate in the high 90s, showing successful management of the dysrhythmia.

Atrial Fibrillation and Atrial Flutter

• Increased automaticity in the atrium, leading to rapid and disorganized atrial activity.

• Affects P waves; the normal P waves are altered or absent.

• In A-Fib, P waves are absent due to the chaotic electrical activity.

• In A-Flutter, flutter waves (F waves) or sawtooth patterns are observed instead of P waves, indicating a more organized but still abnormal atrial activity.

Potential Causes of Atrial Dysrhythmias

• Dig toxicity: Digoxin can cause various atrial and ventricular dysrhythmias, including A-Fib and A-Flutter.

• Electrolyte imbalance: Imbalances in potassium, magnesium, and calcium can disrupt normal electrical activity in the heart.

• Pericarditis: Inflammation of the pericardium can irritate the atria and lead to dysrhythmias.

• Atrial injury: Trauma or surgery to the atria can cause abnormal electrical activity.

Premature Atrial Contractions (PACs)

• PACs don't occur with every beat; they are isolated premature beats.

• In a six-second strip (30 big boxes), the underlying rhythm is usually sinus, indicating that the basic rhythm is normal except for the PACs.

• R-to-R interval is typically regular except where the PAC occurs, disrupting the regularity momentarily.

• P waves are present, but they appear early; PR interval and QRS complex are generally normal.

• PAC defined: A single contraction occurs earlier than expected due to an ectopic focus in the atria.

• Irritated focus in the SA node fires prematurely, or another atrial site takes over temporarily.

• The P wave occurs close to the T wave and may be difficult to distinguish if the heart rate is fast.

• Distance after the premature P wave (QRST) is wider, creating a compensatory pause.

• The rhythm resumes as normal unless another PAC happens, indicating that the underlying sinus rhythm is usually maintained.

• Interpretation: "Sinus rhythm with [number] PACs," providing a complete description of the rhythm.

Causes and Treatment of PACs

• Check for electrolyte imbalances such as hypokalemia and hypomagnesemia.

• Treat the underlying cause, such as reducing caffeine intake or managing stress.

Identifying PACs in a Rhythm Strip

• The P wave appears prematurely and is often close to the T wave, making it essential to examine the T wave carefully.

• The subsequent pause after the PAC is typically longer, allowing the heart to reset before the next normal beat.

Management of PACs

• Treatment is based on symptoms; if asymptomatic, no treatment may be needed.

• Report frequent PACs, as they can affect cardiac output and potentially lead to more serious dysrhythmias.

Additional Notes on PAC Identification

• Assess the placement of the T and P waves to differentiate PACs from other arrhythmias.

• PACs can cause the T wave to appear taller when the P wave is hidden within it, affecting the T wave's morphology.

Frequent PACs

• Can decrease cardiac output and lead to more serious dysrhythmias like atrial fibrillation.

• Treatment may involve addressing the underlying cause, such as electrolyte imbalances, or beta-blockers to reduce heart rate and ectopic beats.

• Continuous monitoring is necessary to assess the frequency and impact of PACs.

Nonconducted PACs

• P wave is present but hidden in the T wave; the QRST complex is missing or dropped because the atria contract prematurely, but the ventricles don't respond.

• The premature P wave contracts so rapidly that the impulse to the ventricle is lost, resulting in a dropped QRST.

• It's essential not to mistake it for a sinus block or arrest, where the entire PQRST complex would be absent; in nonconducted PACs, the P wave is still present.

Wandering Atrial Pacemaker (WAP)

• The pacemaker site shifts from the SA node to other latent pacemaker sites in the atria/AV junction, then back to the SA node, causing variability in P wave shapes and PR intervals.

• Different sites of impulse origin lead to varying P wave shapes. If there are more than two different P wave shapes, it's considered WAP.

• Cannot be called sinus rhythm because the impulse doesn't consistently originate from the SA node.

• May occur in normal hearts due to fluctuations in vagal tone or in patients with cardiac illnesses or COPD, where atrial stretching and irritation can occur.

Paroxysmal Supraventricular Tachycardia (PSVT)

• Paroxysmal means sudden onset and abrupt termination, indicating that the rapid heart rate starts and stops suddenly.

• In PSVT, the impulse is rerouted over and over again at a fast rate in the AV node, creating a re-entry circuit.

• Causes include alcohol, anxiety, hypoxemia, and caffeine, which can all trigger rapid heart rates.

• Can result in decreased cardiac output, leading to lightheadedness, palpitations, and hypotension. Rapid heart rate reduces ventricular filling time and cardiac output.

• Underlying pathophysiology may be related to CAD, which can cause ischemia and irritability in the heart tissue.

• Heart rate ranges from 150 to 250 bpm, which is significantly faster than normal sinus rhythm.

• If PSVT becomes sustained, treatment is necessary to prevent progression to VTach, a more life-threatening arrhythmia.

Identifying PSVT

• PSVT is characterized by a regular rhythm but fast rate, often with the P and T waves occurring so close together that they are hard to distinguish due to the rapid heart rate.

• PR interval measurement may be difficult due to the rapid rate, making it challenging to assess AV node conduction.

Management of SVT

• Vitals, oxygen, and head of the bed down for hypotension to improve blood flow to the brain.

• Assess for chest pain, which may indicate myocardial ischemia due to the rapid heart rate.

• Vagal maneuvers may be used if the heart rate is above 160 bpm; avoid if below 160 bpm to prevent bradycardia; carotid massage, Valsalva maneuver, and ice to the face can stimulate the vagus nerve.

• Medications, such as adenosine, may be administered to stop the heart briefly to interrupt the re-entry circuit.

• Adenosine dose: 6 mg rapid IV push followed by a 20 mL normal saline flush. Repeat with 12 mg if no conversion within two minutes. Administer close to the heart due to short half-life.

• Synchronized cardioversion may be needed if medications are ineffective and the patient is unstable.

• Pacemaker for symptomatic bradycardia if medication ineffective and the patient becomes bradycardic after cardioversion or adenosine.

• Post-conversion, medications like amiodarone, beta-blockers (metoprolol), or calcium channel blockers (diltiazem) may be given to maintain sinus rhythm.

• Cardioversion energy: 50-100 joules, starting with lower energy and increasing as needed.

• Synchronize on the R wave, not the T wave, to avoid dangerous dysrhythmias like R-on-T phenomenon, which can induce ventricular fibrillation.

Synchronized Cardioversion vs. Defibrillation

• Synchronized cardioversion is used for ventricular tachycardia WITH a pulse or supraventricular tachycardias to convert the rhythm to normal.

• Defibrillation is used for pulseless VTach or V Fib when there is no cardiac output.

• Synchronized cardioversion involves sedating the patient before the procedure to minimize discomfort.

• TEE (Transesophageal Echocardiogram) may be performed to check for clots before cardioversion, especially in A-Fib or A-Flutter, to reduce the risk of stroke.

• If the patient loses pulse during synchronized cardioversion, switch to defibrillation mode immediately.

• Important: Always turn the knob to "sync" mode for synchronized cardioversion to ensure the shock is delivered on the R wave.

Atrial Fibrillation (A-Fib)

• Quivering of the atrial muscle with no uniform wave of depolarization, leading to absent P waves and ineffective atrial contraction.

• Rapid, erratic electrical discharge from multiple areas in the atrium, causing disorganized atrial activity.

• Instead of P waves, fibrillatory waves are present, which are small, erratic waves.

• Hallmark: No P waves and an irregularly irregular rhythm, making it easy to identify on an ECG.

Types of A-Fib

• Paroxysmal A-Fib: Occurs suddenly and returns to normal rhythm abruptly, often self-terminating.

• Persistent A-Fib: Continuous throughout, lasting longer than seven days and requiring intervention to terminate.

• Controlled A-Fib: Heart rate less than or equal to 100 bpm with medication management.

• Uncontrolled A-Fib (A-Fib with RVR - Rapid Ventricular Rate): Heart rate greater than 101 bpm, increasing the risk of complications.

• Ventricular rate is the concern, not the atrial rate, as it affects cardiac output and hemodynamic stability.

Management of A-Fib

• Patients at risk for clots are typically on blood thinners, such as warfarin or direct oral anticoagulants (DOACs), to prevent stroke.

• Continuous monitoring may be necessary, depending on stability, to assess heart rate and rhythm changes.

• Medications may be needed to control the heart rate, such as beta-blockers, calcium channel blockers, or digoxin.

• Prevalence increases with age, making it more common in older adults.

• Often a complication of heart failure, increasing the risk of hospitalization and mortality.

• Increases the risk for embolic stroke due to the formation of blood clots in the atria.

Assessment and Treatment

• Assess for signs of decreased cardiac output, such as hypotension, dizziness, and shortness of breath.

• No identifiable P waves; therefore, no PR interval, making it a key diagnostic feature.

• QRS complex is typically normal, unless there is a co-existing ventricular conduction abnormality.

• IV access is important for medication administration, especially during acute episodes.

• Medications to control heart rate: Beta-blockers (e.g., metoprolol), Calcium Channel Blockers (CCB) (e.g., diltiazem), Amiodarone.

• Ablation (radiofrequency or cryoablation) may be performed to address the irritated focus and prevent future episodes.

• Cardioversion is also an option to restore normal sinus rhythm, especially in new-onset A-Fib.

Controlled vs. Uncontrolled A-Fib: Examples

• Controlled A-Fib: Fibrillatory waves, irregularly irregular rhythm, heart rate around 90 bpm, indicating effective rate control.

• Uncontrolled A-Fib (A-Fib with RVR): Rapid rate, fibrillatory waves, irregularly irregular rhythm, heart rate around 170 bpm, requiring immediate intervention.

Atrial Flutter (A-Flutter)

• Flutter waves (sawtooth pattern) are present instead of P waves, indicating organized atrial activity.

• A-Flutter can either have a regular or irregular rhythm based on AV node conduction ratio consistency, such as 2:1 or 4:1 block.

• Atrial rate is fast (250-350 bpm), but ventricular rate is more important for assessing hemodynamic stability.

Rhythm Regularity in A-Flutter

• Regular rhythm: Same AV conduction ratio for every QRS complex (e.g., 4:1, 3:1), making the ventricular response predictable.

• Irregular rhythm: Variable AV conduction ratios (e.g., 5:3:2), resulting in an irregular ventricular response.

• No P waves, therefore no PR interval; QRS complex is normal, unless there is an underlying ventricular abnormality.

• Causes are similar to A-Fib, including heart disease, hypertension, and pulmonary conditions.

Management of A-Flutter

• Check for symptoms; treatment is similar to A-Fib: medications, ablation, and cardioversion to restore normal rhythm and control heart rate.

Wolff-Parkinson-White (WPW) Syndrome

• An accessory conduction pathway present between the atria and ventricles, bypassing the AV node.

• Electrical impulses may be conducted rapidly to the ventricles, leading to pre-excitation.

• Slurring effect seen, called delta waves, on the upstroke of the QRS complex.

• Short PR interval, wide QRS complex, and delta wave are the key ECG features.

• Can cause a rapid heartbeat; treatment involves medication or ablation of the accessory pathway to prevent re-entrant tachycardia.