Cardiology
Question 74 of 180
A 67 year old woman presents to the Emergency Department with a 12 hour history of palpitations. She denies chest pain, shortness of breath or lightheadedness. She has a past medical history of COPD. On examination her observations are recorded as:
- Heart rate: 110 beats/minute
- Blood pressure: 87/45 mmHg
- Respiratory rate: 18 breaths/minute
What is the next management step for this patient?
Answer:
Carry out emergency electrical cardioversion, without delaying to achieve anticoagulation, in people with life‑threatening haemodynamic instability caused by new‑onset atrial fibrillation (as per ALS guidance).Atrial Fibrillation
Cardiology
Last Updated: 31st May 2022
Atrial fibrillation (AF) is a supraventricular tachyarrhythmia resulting from irregular, disorganised electrical activity and ineffective contraction of the atria.
AF is classified according to the pattern of episodes:
- Paroxysmal AF — episodes lasting longer than 30 seconds but less than 7 days (often less than 48 hours) that are self-terminating and recurrent.
- Persistent AF — episodes lasting longer than 7 days (spontaneous termination of the arrhythmia is unlikely to occur after this time) or less than seven days but requiring pharmacological or electrical cardioversion.
- Permanent AF — AF that fails to terminate using cardioversion, AF that is terminated but relapses within 24 hours, or longstanding AF (usually longer than 1 year) in which cardioversion has not been indicated or attempted (sometimes called accepted permanent AF).
Pathophysiology
AF is associated with electrophysical and/or structural abnormalities of the atria. The autonomic nervous system may also play a role in some cases. The 'triggers' for AF are rapidly firing foci, most commonly within the pulmonary vein. These triggers cause propagating wavelets, which may lead to re-entrant circuits in abnormal atrial myocardium. When the atrioventricular node receives more electrical impulses than it can conduct, an irregular ventricular rhythm results. The ventricular rate of untreated AF often averages between 160–180 beats per minute, although this is typically slower in older people. Sustained AF results from structural remodelling of atrial tissue (most notably fibrosis).
Causes
Atrial fibrillation (AF) is most commonly associated with hypertension, coronary artery disease, and myocardial infarction. Other aetiologies include:
- Cardiac or valve conditions, such as:
- Congestive heart failure
- Rheumatic valvular disease
- Atrial or ventricular dilation or hypertrophy
- Pre-excitation syndromes (such as Wolff–Parkinson–White syndrome)
- Sick sinus syndrome
- Congenital heart disease
- Inflammatory or infiltrative disease (such as pericarditis, amyloidosis, or myocarditis)
- Non-cardiac conditions, such as:
- Acute infection
- Autonomic neural dysfunction (such as vagally induced AF)
- Electrolyte depletion (such as hypokalemia and hyponatremia)
- Cancer (such as primary lung cancer involving the pleura and pericardium, and cancers such as breast cancer and malignant melanoma metastasising to the pericardium)
- Pulmonary embolism
- Thyrotoxicosis
- Diabetes mellitus
- Dietary and lifestyle factors, such as:
- Excessive caffeine intake
- Alcohol abuse
- Obesity
- Smoking
- Medication exposure (such as thyroxine or bronchodilators)
Complications
The risks from paroxysmal AF are thought to be similar to those from persistent or permanent AF.
- Stroke and thromboembolism are the main complications of atrial fibrillation (AF). Anticoagulation treatment reduces the risk of stroke by about two-thirds.
- Heart failure can occur because the disorganised electrical conduction in the atria results in ineffective ventricular filling. The cardiac output can be reduced by as much as 10–20%, pushing an already compromised ventricle into failure.
- Tachycardia-induced cardiomyopathy and critical cardiac ischaemia may result from the persistently elevated ventricular rate seen in uncontrolled AF.
- The mortality rate of people with AF appears to be correlated with the presence and severity of concomitant cardiovascular disease.
Diagnosis
Suspect atrial fibrillation (AF) in people with an irregular pulse, with or without any of the following:
- Breathlessness
- Palpitations
- Chest discomfort
- Syncope or dizziness
- Reduced exercise tolerance, malaise/listlessness, decrease in mentation, or polyuria
- A potential complication of AF, such as stroke, transient ischaemic attack, or heart failure
To confirm a diagnosis of AF, arrange an electrocardiogram (ECG):
- If AF is present, the ECG will have no P-waves, a chaotic baseline, and an irregular ventricular rate.
- The ventricular rate is often 160–180 beats per minute but can be lower, especially in people who are asymptomatic.
- The ventricular complexes look normal unless there is a ventricular conduction defect.
If paroxysmal AF is suspected and AF is not detected on standard electrocardiography, arrange ambulatory electrocardiography:
- A 24-hour ambulatory ECG monitor is normally used in people with suspected asymptomatic episodes of paroxysmal AF or symptomatic episodes that are less than 24 hours apart.
- An event recorder ECG is normally used in people who have symptomatic episodes more than 24 hours apart. In some centres, a 7-day Holter monitor is used as an alternative to an event recorder, especially when asymptomatic paroxysms of AF are suspected.
Differential diagnosis
The differential diagnoses of an irregular pulse include:
- Atrial flutter — characterised by a saw-tooth pattern of regular atrial activation on the ECG
- Atrial extrasystoles — common and may cause an irregular pulse
- Ventricular ectopic beats
- Sinus tachycardia — sinus rhythm with more than 100 beats per minute
- Supraventricular tachycardias, including atrial tachycardia, atrioventricular nodal re-entry tachycardia, and Wolff-Parkinson-White syndrome
- Multifocal atrial tachycardia — often seen in people with severe pulmonary disease
- Sinus rhythm with premature atrial or ventricular contractions
Management
For people presenting acutely with AF:
- Carry out emergency electrical cardioversion, without delaying to achieve anticoagulation, in people with life‑threatening haemodynamic instability caused by new‑onset atrial fibrillation.
- In people with atrial fibrillation presenting acutely without life‑threatening haemodynamic instability, offer rate or rhythm control if the onset of the arrhythmia is less than 48 hours, and start rate control if it is more than 48 hours or is uncertain.
- Consider either pharmacological or electrical cardioversion depending on clinical circumstances and resources in people with new‑onset atrial fibrillation who will be treated with a rhythm control strategy.
- If pharmacological cardioversion has been agreed on clinical and resource grounds for new‑onset atrial fibrillation, offer:
- A choice of flecainide or amiodarone to people with no evidence of structural or ischaemic heart disease or
- Amiodarone to people with evidence of structural heart disease.
For all people presenting with AF:
- Assess for signs and symptoms and arrange tests to confirm or rule out underlying causes of AF, including:
- Cardiac causes, such as hypertension, valvular heart disease, heart failure, and ischaemic heart disease — review of the electrocardiogram may identify an old myocardial infarction; arrange a transthoracic echocardiogram if there is a high risk or suspicion of underlying structural heart disease (such as a heart murmur) or functional heart disease (such as heart failure) that will influence subsequent management (for example choice of antiarrhythmic drug).
- Respiratory causes, such as chest infection or lung cancer — arrange a chest X-ray if lung pathology is suspected.
- Systemic causes, such as excessive alcohol intake, hyperthyroidism, electrolyte depletion, infection, or diabetes mellitus — use clinical judgement to determine the need for thyroid function tests, full blood count, and/or blood urea and electrolytes, calcium, magnesium, and glucose measurements.
- Anticoagulation:
- Assess the person's stroke risk using the CHA2DS2VASc assessment tool. Anticoagulant treatment is generally indicated by CHA2DS2VASc scores of two or more, and treatment should also be considered for males with a score of one or more (taking bleeding risk into account).
- Where anticoagulation is being considered, use the ORBIT bleeding risk score to assess the risk of a major bleed. (N.B. Use the ORBIT bleeding risk score because evidence shows that it has a higher accuracy in predicting absolute bleeding risk than other bleeding risk tools. Although ORBIT is the best tool for this purpose, other bleeding risk tools may need to be used until it is embedded in clinical pathways and electronic systems.) Offer monitoring and support to modify risk factors for bleeding including uncontrolled hypertension, harmful alcohol consumption, and concurrent use of medication including antiplatelets, selective serotonin reuptake inhibitors (SSRIs) and non‑steroidal anti‑inflammatory drugs (NSAIDs).
- Anticoagulation can be achieved with the drugs apixaban, dabigatran etexilate, rivaroxaban, or a vitamin K antagonist depending on the person's clinical features and preferences.
- Rate control:
- Offer rate control as the first‑line strategy to people with atrial fibrillation, except in people:
- Whose atrial fibrillation has a reversible cause
- Who have heart failure thought to be primarily caused by atrial fibrillation
- With new‑onset atrial fibrillation (< 48 hours of onset)
- For whom a rhythm control strategy would be more suitable based on clinical judgement
- A standard beta-blocker (that is, a beta‑blocker other than sotalol) e.g. metoprolol or a rate-limiting calcium-channel blocker e.g. diltiazem is recommended as first-line treatment for most people with AF. The choice of drug should be based on the person's symptoms, heart rate, comorbidities, and preferences. Digoxin is a possible alternative only in people with non‑paroxysmal atrial fibrillation who are sedentary (do no or very little physical exercise).
- Offer rate control as the first‑line strategy to people with atrial fibrillation, except in people:
- Rhythm control:
- Rhythm control (electrical or pharmacological) is appropriate for people:
- Whose AF has a reversible cause
- Who have heart failure thought to be primarily caused, or worsened, by AF
- For whom a rhythm control strategy would be more suitable based on clinical judgement
- Whose symptoms continue after heart rate has been controlled or for whom a rate‑control strategy has not been successful
- For people having cardioversion for atrial fibrillation that has persisted for longer than 48 hours, offer electrical (rather than pharmacological) cardioversion. Consider amiodarone therapy starting 4 weeks before and continuing for up to 12 months after electrical cardioversion to maintain sinus rhythm.
- If drug treatment for long‑term rhythm control is needed, consider a standard beta‑blocker (that is, a beta‑blocker other than sotalol) as first‑line treatment unless there are contraindications. If beta‑blockers are contraindicated or unsuccessful, assess the suitability of alternative drugs for rhythm control, taking comorbidities into account.
- In people with atrial fibrillation in whom the duration of the arrhythmia is greater than 48 hours or uncertain and considered for long‑term rhythm control, delay cardioversion until they have been maintained on therapeutic anticoagulation for a minimum of 3 weeks. During this period offer rate control as appropriate.
- Rhythm control (electrical or pharmacological) is appropriate for people:
- Ablation strategies:
- If drug treatment has failed to control symptoms of atrial fibrillation or is unsuitable:
- Offer left atrial catheter ablation to people with paroxysmal atrial fibrillation
- Consider left atrial catheter or surgical ablation for people with persistent atrial fibrillation
- Consider pacing and atrioventricular node ablation for people with permanent atrial fibrillation with symptoms or left ventricular dysfunction thought to be caused by high ventricular rates.
- If drug treatment has failed to control symptoms of atrial fibrillation or is unsuitable:
Scoring tools
CHA2DS2VASc score:
The CHA2DS2VASc score tool is used to assess a person's stroke risk. Adding together the points allocated to each risk factor gives a total CHA2DS2VASc score which guides the decision to offer antithrombotic treatment:
- Congestive heart failure/left ventricular dysfunction (heart failure with reduced ejection fraction, or people with recent decompensated heart failure requiring hospitalisation, irrespective of ejection fraction) = 1
- Hypertension (defined as a resting blood pressure greater than 140 mmHg systolic and/or greater than 90 mmHg diastolic on at least 2 occasions or current antihypertensive pharmacologic treatment) = 1
- Age older than or equal to 75 years = 2
- Diabetes mellitus (defined as fasting plasma glucose level of 7.0 mmol/L or more or treatment with oral hypoglycaemic drugs and/or insulin) = 1
- Stroke/TIA = 2
- Vascular disease (prior myocardial infarction, peripheral arterial disease, or aortic plaque) = 1
- Age 65–74 years = 1
- Sex category (female) = 1
ORBIT tool:
The ORBIT tool is used in adult patients with atrial fibrillation, to assess risk of major bleeding with anticoagulation. (N.B. Use the ORBIT bleeding risk score because evidence shows that it has a higher accuracy in predicting absolute bleeding risk than other bleeding risk tools. Although ORBIT is the best tool for this purpose, other bleeding risk tools may need to be used until it is embedded in clinical pathways and electronic systems.)
- Male: Haemoglobin <13 g/dL or haematocrit <40% (+2)
- Female: Haemoglobin <12 g/dL or haematocrit <36% (+2)
- Age >74 years (+1)
- Bleeding history (Any history of GI bleeding, intracranial bleeding, or hemorrhagic stroke) (+2)
- GFR <60 mL/min/1.73 m2 (+1)
- Treatment with antiplatelet agents (+1)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
