Pharmacology
Cardiovascular
A 64 year old man with a history of poorly controlled hypertension and ischaemic heart disease is presents to ED with a 2 hour history of sudden onset palpitations. ECG demonstrates atrial fibrillation and your consultant wishes to perform chemical cardioversion. Which of the following drugs would be most suitable for chemical cardioversion in this patient:
Answer:
For rhythm-control, chemical cardioversion may be appropriate. Class 1c antiarrhythmic drugs such as flecainide or propafenone may be used but are contraindicated in the presence of heart failure, left ventricular impairment, ischaemic heart disease or prolonged QT-interval. Amiodarone (300 mg intravenously over 20 - 60 mins followed by 900 mg over 24 h) may be used to attempt chemical cardioversion but is less often effective and takes longer to act. Electrical cardioversion remains an option in this setting and will restore sinus rhythm in more patients than chemical cardioversion.Management of Atrial Fibrillation
Pharmacology / Cardiovascular
Last Updated: 23rd May 2023
Treatment of patients with atrial fibrillation aims to reduce symptoms and prevent complications, especially stroke. Atrial fibrillation may be managed by either controlling the ventricular rate (rate control) or by attempting to restore and maintain sinus rhythm (rhythm control). All patients with atrial fibrillation should be assessed for their risk of stroke and thromboembolism.
Acute presentation
All patients with adverse features suggesting life-threatening haemodynamic instability (shock, syncope, heart failure, myocardial ischaemia) caused by new onset atrial fibrillation should undergo emergency electrical cardioversion with synchronised DC shock, without delaying to achieve anticoagulation.
In patients presenting acutely but without life-threatening haemodynamic instability, rate or rhythm control can be offered if the onset of arrhythmia is less than 48 hours; rate control is preferred if onset is more than 48 hours or is uncertain (the longer a person remains in AF, the greater is the likelihood of atrial thrombus developing).
If urgent rate control is required, a beta-blocker can be given intravenously; a rate-limiting calcium channel blocker such as verapamil hydrochloride (if left ventricular ejection fraction (LVEF) is ≥40%) may also be given. In patients with suspected concomitant acute decompensated heart failure, calcium-channel blockers should be avoided and senior specialist advice sought on the use of beta-blockers. The longer a person remains in AF, the greater is the likelihood of atrial thrombus developing; rate control is preferred if onset is more than 48 hours or is uncertain.
Consideration of pharmacological or electrical cardioversion should be based on clinical circumstances in patients with new-onset atrial fibrillation who are to be treated with a rhythm-control strategy. If pharmacological cardioversion has been agreed, flecainide acetate (if no structural or ischaemic heart disease present) or amiodarone hydrochloride can be used.
Cardioversion
Sinus rhythm can be restored by electrical cardioversion or by pharmacological cardioversion with an antiarrhythmic drug such as flecainide acetate or amiodarone hydrochloride. If atrial fibrillation has been present for more than 48 hours, electrical cardioversion is preferred to pharmacological cardioversion, but should be delayed until the patient has been fully anticoagulated for at least 3 weeks. If this is not possible, a left atrial thrombus should be ruled out and parenteral anticoagulation (heparin) commenced immediately before cardioversion; oral anticoagulation should be given after cardioversion and continued for at least 4 weeks. During the period prior to cardioversion, offer rate control as appropriate. Amiodarone hydrochloride started 4 weeks before and continued for up to 12 months after electrical cardioversion to maintain sinus rhythm, may also be considered.
Drug Treatment
Rate control is the preferred first-line treatment strategy for atrial fibrillation except in patients with new-onset atrial fibrillation, with atrial flutter suitable for an ablation strategy, with atrial fibrillation with a reversible cause, or with heart failure primarily caused by atrial fibrillation, or if rhythm control is more suitable based on clinical judgement. Ventricular rate can be controlled with a standard beta-blocker (not sotalol hydrochloride), or with a rate-limiting calcium channel blocker such as diltiazem hydrochloride [unlicensed indication] or verapamil hydrochloride as monotherapy. Choice of drug should be based on individual symptoms, heart rate, comorbidities, and patient preference; for guidance on the use of rate-control drugs in patients with concomitant heart failure, see Chronic heart failure.
Digoxin monotherapy should only be considered for initial rate control in patients with non-paroxysmal atrial fibrillation who are predominantly sedentary, or in those where other rate-limiting drugs are unsuitable.
When monotherapy fails to adequately control the ventricular rate, consider combination therapy with any 2 of the following drugs: a beta-blocker, digoxin, diltiazem hydrochloride. If symptoms are not controlled with a combination of 2 drugs, a rhythm-control strategy should be considered. If ventricular function is diminished (LVEF <40%), the combination of a beta-blocker (that is licensed for use in heart failure) and digoxin is preferred. Digoxin is also used when atrial fibrillation is accompanied by congestive heart failure.
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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 |
