and exertional dyspnoea. Please examine his cardiovascular system.
Begin with a summary of
positive findings
Comment on the pulse rate and irregular rhythm, measured both radially by palpation and apically by auscultation. The pulse difference between the apical and radial rates is an indicator of the degree of rate control: the higher the difference between the two (termed the pulse deficit), the poorer the rate control.
Clinical examination may also help identify the aetiology of atrial fibrillation. Such findings may include:
•
A midline sternotomy scar and graft harvest scars which would indicate bypass grafting for underlying ischaemic heart disease, and previous cardiac surgery as a possible cause of AF•
Signs of thyrotoxicosis such thyroid eye disease, goitre, pretibial myxoedema•
Hypertension can be identified by asking for the patient’s blood pressure•
Findings consistent with mitral valve pathology, such as mitral facies, murmurs•
Inspect for a permanent pacemaker: ‘tachy- brady’ syndrome, requiring ‘pace and block’ treatment•
Peripheral stigmata of alcoholic liver diseaseFollow with a summary of
relevant negative findings
The important relevant negatives to comment on in cases of atrial fibrillation pertain to the complications of atrial fibrillation itself and to complications of anticoagulation:•
Complications of atrial fibrillation include:–
Embolic complications such as stroke. Approximately 20% of strokes result from atrial fibrillation, conferring significant importance on instigating appropriate anticoagulation strategies–
Haemodynamic compromise, e.g. in atrial fibrillation with fast ventricular response.Request the patient’s blood pressure to exclude this
–
Left ventricular dysfunction may be an associated finding, an aetiological factor, or indeed a consequence of long-standing uncontrolled ventricular rate (known as ‘tachycardiomyopathy’)•
An important complication ofanticoagulation is bleeding, the stigmata of which include bruising. Additionally, while signs of previous stroke in a patient with atrial fibrillation are most likely to be due to embolic phenomena, over-anticoagulation may also cause haemorrhagic strokes
State the most likely diagnosis
on the basis of these findings
‘This patient has rate-controlled atrial fibrillation, with possible aetiologies including hypertension and previous cardiothoracic surgery for ischaemic heart disease. He has signs of recent venipuncture, likely in order to check adequacy of anticoagulation. He does not have any features of embolic complications’.Offer relevant differential
diagnoses
The differential of an irregularly irregular pulse includes:
•
Atrial fibrillation•
Atrial flutter or atrial tachycardia with variable block•
Sinus rhythm with frequent atrial or ventricular extrasystoles. This can be ruled out on exercise which would abolish extrasystoles•
Sinus arrhythmia may also manifest as an irregularly irregular pulse.Demonstrate the importance
of clinical context – suggest
relevant questions that would be
taken in a patient history
Questions would relate both to any history of underlying causes and to current symptoms.
Case 15: The irregular pulse: atrial
Case 15 The irregular pulse: atrial fibrillation
37
Demonstrate an understanding of
the value of further investigation
The 12-lead ECG is the most important tool in diagnosing the cause of an irregular pulse. It is best to obtain a rhythm strip to accurately assess the cardiac rhythm.Other investigations would include:
•
Laboratory blood tests: thyroid function tests as a possible underlying aetiology, and clotting studies to assess the adequacy of anticoagulation. Cardiac biomarkers (e.g. troponin) may be elevated, but differentiation between arrhythmia or underlying ischaemia as the aetiology require further clinical evaluation.•
A 24-hour Holter monitor allows review of the AF burden in cases of paroxysmal AF and to assess for the adequacy of rate control in cases of permanent AF•
Echocardiography is used to rule out any structural cardiac lesion (e.g. mitral regurgitation) and to assess left atrial size and left ventricular function•
If ischaemic heart disease is a possibility, the relevant stress test should be consideredAlways offer a management plan
There are two separate, principle considerations in managing AF. The first is anticoagulation, which is the only demonstrable intervention that reduces cardiovascular mortality in AF. Anticoagulation should be instituted according to risk profile for embolic stroke (CHADS-VASc score for non- valvular AF) and weighed up against bleeding risk (HAS-BLED score). Neither the nature of the AF (paroxysmal, persistent or permanent) nor the AF burden in paroxysmal AF should influence the indication for anticoagulation: they should all be managed in the same way with respect to anticoagulation. A target INR of 2–3 is indicated when treated with warfarin.Novel strategies for thromboprophylaxis in AF • The novel oral anticoagulants (e.g.
Dabigatran) are effective alternatives to warfarin that can be considered, but their place in current practice is influenced by local policy. Whilst these agents do not require blood test monitoring, it should be remembered that they also do not have specific antidotes for reversal.
• Left atrial appendage occlusion devices (e.g. Watchman) are also recommended by NICE in specific circumstances of non-valvular AF in which anticoagulation is not tolerated.
The second consideration is whether to pursue a rate or rhythm control strategy. For the former strategy, there is no evidence that strict rate control is beneficial against lenient rate control. Medical therapy for rate control includes beta-blockers, rate-limiting calcium channel blockers and digoxin (the latter preferably used as an adjunctive agent rather than as a standalone medication). In cases whereby medical therapy fails to provide adequate rate control, AV node ablation with permanent pacemaker implantation can be considered.
With regard to rhythm control, many trials
have demonstrated that there is no evidence that mortality is improved by pursuing this strategy (the largest being the AFFIRM trial in 2002, consisting of 4,060 patients: this trial did not demonstrate any difference between rate- and rhythm-control groups for the primary end-point of all-cause mortality). In general, rhythm control should be considered particularly for young patients, individuals who are physically active, and patients who remain symptomatic despite adequate rate control. Rhythm control may be achieved by either medication or pulmonary vein isolation (so-called ‘AF ablation’). Both have side- effects and potential for complications, hence the guidance for opting for rhythm control in individuals in whom the symptomatic burden of AF outweighs these disadvantages of treatment. In the absence of structural heart disease, Flecainide (a class 1c anti-arrhythmic) can be used usually in combination with a beta-blocker. The latter agent is to avoid rapidly conducted atrial flutter which is a common by-product of Flecainide when used to treat AF. In cases of structural heart disease (e.g. adult congenital heart disease, LV impairment), Amiodarone is generally recommended.
The examiner will want to feel that they can trust you to safely run and manage their acute unselected medical take. AF is the commonest arrhythmia encountered in this setting, either as the primary diagnosis or as an incidental finding or co-morbidity. Therefore, an appropriate scheme should be adhered to in order to prioritise the key management aspects of AF in the acute medical patient:
•
Is the patient haemodynamicallycompromised? If so, arrange emergency DC cardioversion. Otherwise, decide how this can be managed medically.