Prolonged cardiac monitoring: it is not just atrial fibrillation!
Author: Dr Linxin Li
This week in the TIA clinic, we have got two patients with lone bilateral loss of vision.
Mr A is a 63-year old man, with known history of ischaemic heart disease, hypertension and hyperlipidaemia, for which he is currently treated with Aspirin, Bisoprolol, Spironolactone, Ramipril and high dose Atorvastatin. He presented with one episode of sudden total binocular loss of vision whilst driving. The episode lasted for seconds with full and rapid recovery. He did not have any focal weakness or any other pre-syncopal symptom. Blood pressure was not elevated on exam. ECG in clinic was normal sinus rhythm. MRI brain did not show any acute ischaemic changes and MR-angiogram revealed no vasculature abnormality, especially no stenosis of the posterior circulation.
Reassuring? Would you request any further investigation?
Mr B is a 50-year old taxi driver. He is a non-smoker but has known history of hypertension, hyperlipidaemia and obstructive sleep apnoea. Whilst driving his taxi early in the morning he had a sudden onset of vertigo with complete loss of vision. The vertigo and visual loss settled within 30 seconds and was not companied by nausea, hearing loss, tinnitus, sensation of fullness or any palpitation. He subsequently went on to have another 3 very similar episodes. On examination, his blood pressure was severely elevated at 188/115 mmHg. ECG showed sinus rhythm. MRI brain and MR-angiogram were completely normal.
Worrying? Would you request any further investigation?
Both Mr A and Mr B underwent a 5-day ECG event-recorder (R test). To our surprise, whilst neither patient had any tracing of paroxysmal atrial fibrillation, Mr A had runs of paroxysmal ventricular tachycardia and Mr B presented with multiple episodes of paroxysmal supraventricular tachycardia. So these brief episodes of bilateral loss of vision could well be explained by a hypo-perfusion phenomenon resulting from the arrhythmia detected on prolonged cardiac monitoring.
Dennis et al published the first case-series of lone transient bilateral blindness based on a complete sample of cases from a population-based study back in 1989.1 They reported the clinical characteristics and prognosis of 14 patients who presented to the Oxfordshire Community Stroke Project and compared them to that of the 184 patients who presented with classical transient ischaemic attack. They found that patients with transient bilateral blindness had similar high prevalence of vascular risk factors, with a 16 times excess risk of stroke during a mean follow-up of 2.4 years. Interestingly, 3 out of the 14 patients also died during follow-up, which was not explicable by stroke, suggesting that underlying cardiac cause might also be relevant the relatively high mortality in this patient group.
Whilst we perform prolonged cardiac monitoring to look for paroxysmal atrial fibrillation in the TIA clinic all the time, it is worth bearing in mind that, there is more than atrial fibrillation that can be the culprit!
Reference
- Dennis MS, Sandercock PAG, Bamford JM, Warlow CP. Lone bilateral blindness: a transient ischaemic attach. Lancet 1989; 333: 185-188
