Q&A ON PERI-OP ATRIAL FIBRILLATION (PAOF)

These are Q&A notes that I had prepared while teaching Final FRCA Students at Mersey School of Anaesthesia, Liverpool UK. Hope Trainees across the globe find these useful.

What is the incidence and prevalence of AF. What morbidities are associated with AF? Atrial fibrillation (AF) is a supraventricular arrhythmia characterized by uncoordinated

atrial activation and consequent deterioration of mechanical function, loss of atrial kick (systole) accounts for 20-30% of atrial emptying.

AF is associated with a high risk of stroke as well as increased mortality

INCIDENCE

?????? General population: ～1% per year

–????? Age <40 years: ～0.1% per year

–????? Age >80 years: ～2% per year

?????? Postoperatively:

–????? Noncardiac surgery: Up to 8%

–????? Thoracic surgery: Up to 30%

–????? Cardiac surgery: Up to 46%

PREVALENCE

In the west, 4.5 million in the European Union and about 2.2 million patients in the US have either persistent or paroxysmal AF

MORBIDITY AND MORTALITY ASSOCIATED WITH AF

?????? Stroke

?????? cerebral thromboembolic complications

?????? myocardial ischemia

?????? Congestive heart failure (CHF)

?????? Hypotension

?????? Ischemic stroke: 5% per year (2–7 times more frequently than those without AF)

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MORTALITY

?????? Doubled compared to age-matched controls in NSR

?????? Related to the severity of underlying heart disease

?????? CHF is a strong predictor of mortality

?????? Only a minority of patients die of thromboembolic complications

What are the aetiological factors that can lead to AF?

?????? Cardiovascular: HTN, CAD, CHF, valvular (mitral stenosis), and pericardial heart disease

?????? Non-cardiovascular: DM, hyperthyroidism, alcohol abuse, COPD, increasing age

?????? Iatrogenic:

–????? Surgery, medications (beta-agonists, cold medications, antihistamines, local anaesthetics)

–????? Familial: Na+ and K+ channel mutations

–????? Perioperative: Atrial injury or ischemic inflammation, increased adrenergic tone, atrial

–????? stretch from volume overload, and electrolyte disturbances

What is the pathophysiology of AF?

?????? Re-entry is the main electrophysiologic mechanism of AF, and is secondary to structural or electrical remodelling.

?????? Atrial dilation and inflammation can result in interstitial fibrosis and is the most common substrate predisposing to AF.

?????? Channelopathies involving both K+ and Na+ channels are responsible for most familial forms of AF.

?????? Triggers include alcohol, sleep deprivation, emotional stress, caffeine, and exercise.

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How do you classify AF?

?????? New Onset AF is the first presentation of AF for which the actual onset is not known.

?????? Paroxysmal and persistent AFs are both recurrent, but the former is self-terminating within 7 days, while the latter requires cardioversion to restore sinus rhythm.

?????? Persistent AF describes unsuccessful or abandoned attempts to convert to sinus rhythm.

?????? Etiologically, AF can be valvular or non-valvular. Patients with mitral valve disease are at an increased risk for stroke.

What are the Anaesthesia goals in a patient with AF?

?????? Maintain rate control in patients presenting with AF; maintain NSR in patients with recurrent or paroxysmal AF.

?????? Perioperative anticoagulation strategy should balance the risk of bleeding related to the type of surgery and the individual patient’s risk of thrombosis.

?????? Optimization of comorbidities

?????? Implement preventative strategies in surgical patients who are at a high risk for the development of AF (e.g., thoracic and cardiac procedures).

What are the things that you look for in the pre-op assessment in patients who have AF?

HISTORY

?????? Duration and type of AF

?????? Assess CHADS2 score

?????? Palpitations and shortness of breath

?????? Neurologic symptoms

SIGNS/PHYSICAL EXAM

? HR: Irregularly irregular

? Signs of CHF: orthopnoea, heart murmurs and gallop, rales and crackles

? Consider common comorbidities: COPD, hyperthyroidism, DM, valvular disease

TREATMENT HISTORY

?????? Length of treatment

?????? Antiarrhythmics: Class, efficacy, side effects

?????? Previous electrical cardioversion

?????? Electrophysiological ablation

?????? Percutaneous closure of the left atrial appendix

?????? Anticoagulation regimen; INR if on warfarin

MEDICATION HISTORY

?????? For rhythm control: Class III antiarrhythmics (Amiodarone, Sotalol) are preferred due to their low toxicity, however they should be used with caution in patients with long QT ( LQT).

?????? For rate control: Beta-blockers, Calcium channel blockers, and rarely Digoxin are used.

?????? Amiodarone is effective for both rate control and pharmacological cardioversion (up to 90% success if bolus of 300mg is followed by infusion 900mg over 23 hrs). It is considered safe in patients with LV dysfunction, unlike class IC drugs. Acute side effects: Hypotension, bradycardia.

How is thromboembolism risk assessed and managed in AF patients?

?????? CHADS2 provides an objective score for estimating the risk of stroke in non-valvular AF.

?????? Points for individual stroke risk factors are assigned as follows:

?????? 1 point each is assigned for CHF, HTN (>140/90), age >75, or DM (CHAD)

?????? 2 points are assigned for a history of Stroke/TIA/Thromboembolism

?????? A CHADS2 score of 0 denotes low risk, 1–2 intermediate risk, and 3–6 high risk of stroke

?????? Anticoagulation regimens are based upon the risk of stroke (CHADS2 or other scores) and are balanced against the risk of bleeding.

–????? Aspirin if CHADS2 score ≤1

–????? Warfarin if CHADS2 score ≥2

–????? Dabigatran is a direct selective thrombin inhibitor. Stroke prevention is equal to that of warfarin and fewer bleeding complications are seen with low doses. It is dosed twice per day, orally. For a CHADS2 score = 1, the dose is 110 mg PO and for a CHADS2 score ≥2, the dose is 150 mg PO.

?????? The CHADS2 score has not been validated in valvular AF where there is a high risk of stroke; thus, anticoagulation is always required.

?????? Statins: Statins may be protective: Risk of postoperative AF is inversely related to the duration of preoperative statin prophylaxis. Additionally, statins improve outcomes in the surgical ablation of AF.

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What are the diagnostic tests that should be conducted in patients with AF and how do you interpret them?

?????? Palpation or auscultation: Irregular heart rate

?????? ECG: Uneven R-R interval with occasional f waves

?????? CXR: Pulmonary vasculature congestion and cardiomegaly

?????? Echocardiogram and stress testing may be considered to rule out underlying structural or ischemic myocardial disease, left atrial enlargement, thrombus, RV strain if PE is suspected.

?????? Holter monitor in suspected paroxysmal AF or if evaluating the efficacy of rate control treatment

?????? Pacemaker may be in place.

?????? Labs/Studies:

?????? INR if on warfarin, or aPTT ?if on heparin; there is no valid point-of-care test for direct thrombin inhibitors.

?????? Electrolytes, including magnesium

?????? Digoxin levels

?????? Thyroid function tests if on amiodarone

?????? EP studies, if available

?????? Concomitant organ dysfunction: Evaluate cardiopulmonary, neurologic, and endocrine systems for known associated comorbidities

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When or in what circumstances will you delay surgery in patients with AF?

?????? Poor rate control

?????? Signs and symptoms of CHF

?????? New-onset AF of unknown aetiology (rule out ischemic or structural heart disease)

?????? Delay DC cardioversion until therapeutic INR or TEE evidence of atrial thrombus

What are the Pre-op concerns and how do you prepare patients with AF?

PREMEDICATION:

?????? Anxiolysis as needed

?????? Caution with possible triggering agents (Glycopyrrolate, Beta Agonist Inhalers)

?????? Heart rate of 50-100 bpm are reasonable in patients with AF.

?????? Consider optimizing existing antiarrhythmic therapy.

?????? In cardiac surgery, corticosteroids should be considered; they have been shown to reduce the incidence of AF postoperatively

?????? Statins, given 7 days preoperatively, reduce the incidence of postoperative AF in thoracic and cardiac surgery, and should be considered

SPECIAL CONCERNS FOR INFORMED CONSENT

?????? Increased risk of thromboembolic or blood transfusion, if on anticoagulant

?????? Increased risk of ventricular arrhythmias, CHF

?????? Possible need for intraoperative DC cardioversion in recurrent AF

?????? Possible TEE to rule out atrial clots in a patient who is not anticoagulated

What are the intraoperative goals and management?

CHOICE OF ANAESTHESIA

?????? Regional or neuraxial anaesthesia may be contraindicated due to anticoagulants. If warfarin has been held for surgery, PT/PTT/INR should be checked prior to placement. In patients with thrombin inhibitors (Dabigatran) most anaesthesia society guidelines recommend against the use of neuraxial anaesthesia.

?????? For MAC cases, consider dexmedetomidine or remifentanil (with Propofol) to maintain rate control.

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MONITORING

?????? Noninvasive BP measurement is adequate for most routine cases. Highly irregular pulses may result in the NIBP cuff reading taking more time to cycle and may give unreliable measurements.

?????? Arterial line is not necessary in stable haemodynamics and routine cases. However, a lower threshold should exist for placing an arterial line when hemodynamic instability is anticipated.

?????? Central venous catheters, pulmonary artery catheters, and TEE may be indicated based on the type of surgery and comorbidities. TEE is a superior monitor of preload and contractility, particularly in the absence of atrial contraction. TEE may be beneficial in guiding fluid administration and vasopressor therapy in critical patients with AF.

?????? Oesophageal Doppler and arterial pressure based cardiac output monitors do not work well in AF.

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INDUCTION/AIRWAY MANAGEMENT

?????? Avoid excessive sympathetic stimulation prior to airway management by ensuring adequate:

?????? Depth of anesthesia with induction agents, volatile agents, opioids, and lidocaine

o?? Oxygenation and ventilation

o?? Time for full onset of muscle relaxants when intubating

o?? Have rate control drugs ready and available

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MAINTENANCE

?????? MAC/sedation: Caution with, or avoidance of, epinephrine in local anaesthesia

?????? General anaesthesia may be provided with either a balanced inhalational or intravenous technique.

?????? Rate control: Adequate depth of anaesthesia, cautious use of positive chronotropes (e.g., ephedrine, beta-2 agonist inhalers and drugs, vagolytic agents like glycopyrrolate/Atropine, etc.)

?????? Rapid ventricular rate (RVR) with instability warrants immediate DC cardioversion.

?????? For RVR with hemodynamic stability, rate control may begin with Diltiazem or Beta-blockers. Reserve Amiodarone for patients with poor LV function. Caution: Amiodarone may convert into NSR and “eject” a clot into the systemic circulation.

?????? New-onset AF: Pharmacological conversion if stable, DC cardioversion if unstable. ??Caution: Successful DC cardioversion may still require anticoagulation due to atrial stunning.

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EXTUBATION/EMERGENCE

?????? Avoid excessive sympathetic stimulation (see “Induction”)

?????? Slow titration of reversal agents

?????? Consider deep extubation, if appropriate, to avoid coughing and bucking

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What are the goals and instructions for post-op care in patients with AF?

?????? Routine postoperative care is usually appropriate in stable patients.

?????? Postoperatively, heart rates as high as 120 bpm are reasonable given the stressors of pain or hypovolemia, as long as these increased heart rates do not cause hemodynamic instability or myocardial ischemia.

?????? Telemetry or level-2 or 3 care may be warranted in poorly controlled AF and haemodynamic instability.

MEDICATIONS/LAB STUDIES/ CONSULTS

?????? Reinstitute rate control, antiarrhythmic, and/or anticoagulants as soon as appropriate

?????? Labs: Electrolytes, glucose in DM, INR/PTT

?????? Troponins if underlying cause for AF is Coronary Artery disease

List the complication that can arise due to post-op AF?

?????? RVR with hypotension, CHF

?????? Ventricular arrhythmias

?????? Myocardial ischemia

?????? Bleeding versus stroke and other thrombotic complications

?????? Postoperative cognitive dysfunction