Atrial Fibrillation Viva

Long Case Viva Defence

Candidate's opening statement (model answer)

"Mr Thompson is a 74-year-old retired accountant who presents with a 3-month history of progressive exertional dyspnoea, palpitations, and fatigue. Ambulatory ECG monitoring confirmed persistent atrial fibrillation with rates up to 130 bpm. [1]

His past history includes:

• Ischaemic heart disease — NSTEMI 5 years ago, DES to the circumflex
• Hypertension — longstanding
• Type 2 diabetes — HbA1c 64 mmol/mol
• Stage 3B CKD — eGFR 38
• Obesity — BMI 34 [1]

His current medications are metformin 1g BD, gliclazide 80mg, perindopril 5mg, atorvastatin 40mg, aspirin 100mg, and amlodipine 10mg. His ECG shows AF at a ventricular rate of 102. His echo shows LVEF 50%, mild-moderate LA dilatation (LAA velocity 0.3 m/s), no significant valvular disease, and RVSP 32 mmHg. [1]

His main problems are:

1. Persistent atrial fibrillation, symptomatic, recently diagnosed
2. High thromboembolic risk — CHA₂DS₂-VASc needs formal calculation
3. Suboptimal rate control (HR 102 despite no rate-control agent)
4. Type 2 diabetes with poor glycaemic control
5. CKD stage 3B — constrains drug choices and DOAC dosing
6. Hypertension — above target
7. Obesity and likely sleep apnoea — modifiable AF risk factors [1]

My immediate priorities are: initiate rate control, start appropriate anticoagulation, and address his comorbidities." [1]

Examiner probing questions and model answers

Q1: "What is his CHA₂DS₂-VASc score and what does that mean for anticoagulation?" [1]

"His CHA₂DS₂-VASc score is 5: age 65–74 (1), hypertension (1), diabetes (1), vascular disease from his prior MI (1), and heart failure borderline — he is at the lower limit of normal EF, so I would count that conservatively. As a male, the maximum non-sex score is relevant here. A score of 2 or more in men strongly warrants anticoagulation. He should be started on a DOAC. [1]

I would choose apixaban. ARISTOTLE (PMID 21875359) showed apixaban was superior to warfarin — 21% reduction in stroke, 31% less major bleeding, and 11% mortality reduction. For his dose: the reduction criteria are age 80+, weight 60 kg or under, or creatinine 133+ micromol/L. He is 74, weighs 85 kg, and has creatinine approximately 155 — that is one criterion (renal). So he stays on apixaban 5mg BID. I would monitor his renal function closely given eGFR 38, and reduce the dose if he crosses a second criterion. [1]

I would stop his aspirin. His stent is over 12 months old, so oral anticoagulation alone is recommended to reduce bleeding." [1]

Q2: "Would you pursue rhythm control?" [1]

"Yes, I would consider rhythm control in addition to rate control. He is symptomatic, his AF was diagnosed within the last year, and he has cardiovascular comorbidities — this is exactly the population EAST-AFNET 4 (PMID 32865375) studied. Early structured rhythm control reduced the composite of cardiovascular death, stroke, HF hospitalisation, and ACS by 21%. [1]

However, his antiarrhythmic options are constrained by his ischaemic heart disease. Flecainide is contraindicated because class IC drugs are pro-arrhythmic in the setting of prior MI. Sotalol or amiodarone are acceptable. If a trial of antiarrhythmic fails or is not tolerated, I would refer for catheter ablation — pulmonary vein isolation. The CABANA trial (PMID 30874715) showed ablation significantly reduced AF recurrence compared with drug therapy, though the primary composite endpoint was not met in the overall population. If he had HFrEF rather than his borderline EF, the heart failure subgroup data would make ablation even more compelling. [1]

I would start with rate control first — a beta-blocker for both AF rate and secondary prevention — and then discuss rhythm options with the patient, including the risks and benefits of ablation versus antiarrhythmic drugs." [1]

Q3: "He tells you his father had a major GI bleed on warfarin. Does that change your approach?" [1]

"I would calculate his HAS-BLED score to formally assess bleeding risk: uncontrolled hypertension (1), abnormal renal function with eGFR 38 (1), age over 65 (1), and concomitant aspirin currently (1) — approximately 3 to 4. A score of 3 or more indicates increased bleeding risk. [1]

A family history of bleeding is not a formal HAS-BLED criterion, but it would prompt me to look for modifiable bleeding factors. I would: control his blood pressure more tightly, stop the aspirin, check for and treat any source of GI bleeding (consider faecal occult blood or endoscopy if clinically indicated), and ensure he is not on NSAIDs. [1]

Crucially, high bleeding risk is not a contraindication to anticoagulation — it is a signal to correct modifiable factors. The net clinical benefit almost always favours anticoagulation in a patient with CHA₂DS₂-VASc 5. I would continue with a DOAC, as DOACs — particularly apixaban — carry lower major bleeding risk than warfarin. I would counsel him on bleeding warning signs and the availability of reversal agents." [1]

Q4: "His renal function declines to eGFR 30 over the next year. Does that affect his DOAC?" [1]

"Yes, declining renal function affects all DOACs because they are renally cleared to varying degrees. Apixaban is approximately 27% renally cleared — the lowest among DOACs — making it relatively safe in CKD. At eGFR 30, apixaban 5mg BID is still appropriate as long as he does not meet two dose-reduction criteria. Given his creatinine would likely now be over 133 micromol/L (the renal criterion) and he may now be approaching 75, he could soon meet two criteria and need dose reduction to 2.5mg BID. [1]

I would increase renal monitoring to every 3–6 months at eGFR 30. If eGFR drops below 25, I would involve a nephrologist and reassess. Dabigatran, at 80% renal clearance, would be much more affected and is generally avoided below CrCl 30." [1]

Q5: "He asks whether ablation will cure his AF so he can stop the blood thinner. What do you tell him?" [1]

"I would be honest and clear: ablation is a management strategy, not a guaranteed cure. While PVI has a 60–80% success rate for paroxysmal AF after one procedure, success is lower for persistent AF, and recurrences are common. More importantly, anticoagulation should continue based on his CHA₂DS₂-VASc score regardless of whether ablation is successful — the AFFIRM trial (PMID 12466506) showed that most strokes occurred when anticoagulation was stopped, even in patients in sinus rhythm. Silent AF episodes are common after apparently successful ablation. [1]

So I would advise him that ablation may improve his symptoms and quality of life, but it does not remove the need for lifelong anticoagulation at his risk level." [1]

Short Case Discussion

Scenario: "Examine this patient's cardiovascular system"

Candidate presentation (model): [1]

"I examined Mrs Chen's cardiovascular system. She is comfortable at rest at 45 degrees. There is no clubbing, pallor, cyanosis, or stigmata of endocarditis. [1]

The radial pulse is irregularly irregular, rate 84 beats per minute, with a pulse deficit of approximately 10 beats compared to the apical rate. The pulse volume is variable. Blood pressure is 132/78 in the right arm. [1]

The JVP is not elevated; there are no prominent waves and the waveform appears disorganised, consistent with absent organised atrial activity. [1]

The apex beat is not displaced, in the 5th intercostal space, mid-clavicular line, and is of normal character. There is no parasternal heave. On auscultation, the first heart sound varies in intensity from beat to beat. There are no murmurs. The second heart sound is normally split. [1]

Examination of the lungs is clear. There is no peripheral oedema. Abdominal examination is unremarkable. [1]

In summary, this patient has an irregularly irregular pulse with variable first heart sound intensity and no murmurs, consistent with atrial fibrillation in sinus of normal cardiac function." [1]

Examiner: "What is the significance of the varying first heart sound?" [1]

"In atrial fibrillation, the first heart sound varies in intensity because the interval between beats is constantly changing. When the R-R interval is short, the mitral and tricuspid valves are still widely open at the onset of ventricular systole, producing a loud S1. When the interval is long, the valves have had time to drift partially closed passively before systole, producing a softer S1. This variable S1 intensity is a classic auscultatory finding in AF and reflects the variable diastolic filling time." [1]

Examiner: "What is the pulse deficit and why does it occur?" [1]

"The pulse deficit is the difference between the apical (heart) rate and the radial (peripheral) rate. It occurs in AF because some ventricular contractions happen after a very short diastolic filling period, producing a very low stroke volume that is too weak to transmit a palpable pulse wave to the radial artery. The greater the pulse deficit, the faster and less controlled the ventricular rate. A pulse deficit of 10 or more suggests the rate is not well controlled." [1]

Examiner: "What are the causes of atrial fibrillation?" [1]

"I group them using the mnemonic for common reversible and chronic causes. The commonest associations are increasing age, hypertension, and ischaemic heart disease. Then I consider: [1]

• Cardiac: heart failure, valvular disease (especially mitral), hypertrophic cardiomyopathy, pericarditis, post-cardiac surgery
• Endocrine: hyperthyroidism (must check TSH in all new AF)
• Metabolic: alcohol excess — 'holiday heart', electrolyte disturbance (hypokalaemia, hypomagnesaemia)
• Respiratory: pulmonary embolism, pneumonia, COPD exacerbation, sleep apnoea
• Systemic: sepsis, post-operative state
• Idiopathic: lone AF in a young patient with no identifiable cause" [1]

Examiner: "She has a prosthetic mitral valve. Does that change your anticoagulation?" [1]

"Yes, significantly. If it is a mechanical prosthetic valve, warfarin is mandatory — DOACs are contraindicated. This is based on the RE-ALIGN trial showing harm with dabigatran in mechanical valve patients, and the exclusion of mechanical valve patients from all major DOAC trials. If it is a bioprosthetic mitral valve, a DOAC is acceptable per recent guideline updates and ARISTOTLE subgroup data. So I would need to clarify the valve type before deciding on anticoagulation." [1]