Syncope: Ockham s Razor

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Gilbert Dawson
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1 Syncope: Ockham s Razor Time/Place Wednesday, 25 th January am-12pm Room 210, Wallace Wurth Building Facilitators Michael Grimm & Tony Grabs Aims Illustrate multiple possible causes for a common presenting symptom. Illustrate the way tests can turn up pathology which may not be relevant to the symptomatology but nonetheless needs to be dealt with. Illustrate the frequent co-existence of multiple pathology especially in older patients. Abstract Mr Smith is a 73 year old male who presents to the Emergency Department following a collapse. Clinical assessment and several investigations reveal multiple abnormalities, some of which may explain his presenting problem. Readings Preparation Read the case thoroughly before the case method tutorial and come prepared to discuss your perceptions and reflections. Consider the following questions: 1. What features of this case did not add up to a simple diagnosis and why? How reliable is history from a relative? 2. Were all the investigations performed appropriate and necessary? 3. Mr Smith was admitted under the care of the Cardiology team. Why do you think this was done and would it have been more appropriate to admit under Neurology? 4. Coronary disease is very common. Syncope is also common. Why did you conclude that the two were unlikely to be causally related in Mr Smith? 5. What would your approach to Mr Smith have been had he not suffered the syncopal episode at all but came to see you in a preoperative clinic prior to admission for hernia repair, and you found the ECG and clinical findings outlined on his presentation above (trifascicular block; systolic aortic murmur)? Would you have ordered further tests and would you have recommended it was safe for him to go to surgery? 6. What tools are available for assessing severity of valvular heart disease and how do these differ from other cardiac investigations? 7. How will you assess the relevance of the tachycardia discovered on the ECG monitor in hospital? Page 1

2 8. Where should you go from here in terms of managing Mr Smith? 9. What is Ockham s razor and what is its relevance to medicine and in particular, the making of diagnoses? Page 2

3 OCKHAM S RAZOR Presenting Complaint Mr William Smith, aged 73, presented to the Emergency Department via ambulance on a Sunday afternoon when you are working a day shift as an intern (it s in fact your first weekend shift but luckily you were an excellent student so you feel reasonably confident! So far you have sutured a few lacerations but now it seems there is a patient with a more complex and challenging problem). On arrival, Mr Smith is confused and agitated and a little uncertain as to why he is there at all. Fortunately his wife accompanied him in the ambulance and you are able to talk to her. She tells you that he was just about to set off for a regular walk to the park when he put his hand to his chest, became a little pale and sweaty and looked quite unwell and collapsed to the floor in front of her, hitting his head on the wall on the way down but not doing any major injury. Initial Assessment in the Emergency Department Your initial assessment of Mr Smith reveals that he is haemodynamically stable with a blood pressure of 120/80 and a heart rate of 75 and while the ED nurse is doing an ECG, you take the opportunity of talking further to his wife. You ask her more about what happened today. She is adamant that he was in fact unconscious but only for seconds. She says he became quite pale but she did not think to check whether or not he had a pulse. After this fairly brief period he became awake again and reasonably lucid, although somewhat confused and agitated, and had no real recollection of what had happened. His state had remained much the same over the following thirty minutes or so, which was the time that it took for the ambulance to arrive and for him to reach the Emergency Department. Mrs Smith tells you that he has been generally fit and well but has complained occasionally of a tight feeling in the chest on his regular walks over the last year or two. He has also complained to her on a couple of occasions of rapid flutters in his chest lasting only a few seconds, which he has ignored. He has never lost consciousness before like this. He has a history of hypertension going back some twenty years or so she thinks, and for which he currently takes perindopril 4mg daily. He also takes aspirin daily (on his GP s advice). His wife does not know what his cholesterol is but believes that it has been normal and has not required treatment. Mr Smith smoked 20 cigarettes a day from the age of twenty to about the age of fifty when he gave them up with some difficulty but has not smoked since. He drinks one or two light beers a day and has never been a heavy drinker. He is a retired businessman who has no financial worries. Page 3

4 On examination The blood pressure and heart rate noted on admission have not changed significantly. You find no signs of cardiac failure but do notice on auscultation that he has relatively normal heart sounds but a moderately loud mid-systolic ejection murmur which fills most of systole and is audible all over the precordium and radiates into the carotid arteries. Neurological examination is completely normal and Mr Smith is now fully oriented to time and place but still has no recollection at all of his actual collapse. The remainder of his physical examination is unremarkable, apart from him being overweight. His ECG is provided (see figure 1). This shows a prolonged PR interval (first degree heart block), a right bundle branch block and marked left axis deviation due to left anterior hemi-block. This combination is commonly referred to as trifascicular block. As a conscientious intern, you form your own provisional diagnosis and suggest investigations and management, but then of course discuss these with your team members (registrar and consultant). Progress You discuss the case with the medical registrar and admit Mr Smith under what turns out to be the cardiology team that you are commencing work with the following day (Monday). The blood tests you carried out in the Emergency Department show no evidence of myocardial infarction (troponin was normal on both Sunday afternoon and Sunday evening); cholesterol is 5.8 mmol/l (normal < 5.5 mmol/l) and his urea, electrolytes and creatinine are all normal. He is HIV negative and his liver function and thyroid function are normal. A chest x-ray is normal except for some calcification in the area of the aortic valve. Subsequent investigations You are concerned about the possibility that Mr Smith may have suffered an episode of complete heart block related to his trifascicular block and so you monitor his ECG and organise for him to have a Holter monitor carried out in the next couple of days. This is 24 hour recording of the ECG, which is recorded and subsequently analysed by computer. The patient is able to press a button and make notes at the time of any symptoms or event such as chest pain or palpitations, so that the test can correlate changes in the ECG with clinical events. However, rhythm disturbances can be detected even in the absence of the patient highlighting an event. You are keen also to document whether or not your provisional clinical diagnosis of aortic stenosis is accurate and you arrange for him to have an echocardiogram. This Page 4

5 shows normal left ventricular function with borderline hypertrophy of the left ventricular wall. The aortic valve is thickened, disorganised and calcified and there is a peak gradient across the aortic valve of 60mmHg, (normally of course, there is no gradient across an open aortic valve). Cardiac catheterisation Both in order to confirm your diagnosis and also to check for possible co-existent coronary artery disease (a very important piece of information for a surgeon contemplating operating on this man s aortic valve), you suggest (and your team agrees) that he should have coronary angiography in the cardiac catheter laboratory. The cardiac catheter report is attached (figure 2). As you can see, it confirms moderate aortic stenosis and some co-existent coronary disease, which may well need to be dealt with at the time of any contemplated surgery. Assessment You are still a little uncertain as to the pathogenesis of the event that occurred on the previous weekend. You know from your reading around this case by now, that aortic stenosis can present with syncope due to an inappropriate haemodynamic response to a pressure overload. You also know that this is not terribly common as a first presentation and nor is it very common in moderate aortic stenosis which is what Mr Smith appears to be suffering from. You are also still drawn to your initial diagnosis, which was that of intermittent complete heart block associated with trifascicular block. You know that this can occur in association with or quite separate from aortic valve disease. Your training has warned you against unnecessarily multiplying diagnoses (Ockham s razor), and you are very keen to combine all or most of your findings into one or as few as diagnoses as possible. You know that aortic valve disease is commonly associated with abnormalities of the ventricular conduction system and this may well provide a link between several of Mr Smith s problems. Coronary artery disease is common but it seems unlikely to you from your experience and reading, that Mr Smith s coronary disease is the cause of his presentation, although this is not impossible. While contemplating all of this, you are called to the ward by the nursing staff who have noticed an intermittent tachyarrhythmia on Mr Smith s ECG, (figure 3). This long rhythm strip is from a single lead (V1), showing underlying sinus rhythm (you note that the PR interval is normal at this stage but are also conscious of the fact that PR intervals can vary). The patient is suffering from runs of a broad- complex, slightly irregular tachycardia, which you consider possibly to be ventricular tachycardia or alternately atrial fibrillation with aberrant intraventricular conduction due to the rapid rate. Page 5

6 You are interested in whether or not Mr Smith is symptomatic while this is happening and you find that he is completely unaware of his arrhythmia at present, although he does tell you that he has noticed occasional palpitations overnight, similar to those he had mentioned to his wife in the past. Summary and Issues Mr Smith is a 73 year old male who has presented following a collapse. You have identified several potential diagnoses (and corresponding potential treatments) for Mr Smith s presenting symptom. Page 6

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