Lewis v Workcover/Allianz Australia

3 The cause of death certified by the death certificate (TB 43) was "Myocardial infarction. Coronary Artery Atherosclerosis". The worker was 61 years of age at the time of his death.

4 The issue in this judicial determination is whether the worker died as a result of a compensable disability arising out of or in the course of his employment on 16 December 1996.

5 On the basis of the death certificate and the evidence of the two specialist cardiologists, Drs Zimmet and Sangster, I find that the worker suffered a disability consisting of the aggravation, acceleration, exacerbation, deterioration, or recurrence of a pre-existing coronary heart disease. I also find that the disability arose in the course of his employment. Accordingly in determining the applicant's claim s 31(5) of the Act is to be applied. Therefore the onus is on the respondent claims agent to prove, on the balance of probabilities, that the worker's employment did not contribute to his disability. If that onus is not met it will be presumed that the employment did contribute.

6 The evidence as to the worker's activities on 16 December 1996 prior to his collapse on the verandah of the administration building is crucial to this issue of causation. I make the following findings of fact based on the evidence of Mr M Ramm, a fellow draftsman who shared an office with the deceased, and Mr D McLean, who came to the worker's assistance on the verandah.

7 The worker arrived at his work desk at about 8.00 am which was his usual starting time. Mr Ramm observed the worker performing his normal duties seated at a flat topped desk from that time until 10.00 am, when the worker left the room. Mr Ramm assumed that at that point the worker went out for his usual morning tea break. Mr Ramm did not see the worker again after 10.00 am. He recalled that during the course of the morning "probably in the first hour or so of him arriving at work....." (tr 65) the worker told him that he was "feeling seedy" or was "not feeling well". (TB 44)

8 At approximately 10.30 am Mr McLean was attending a meeting in an office in the administration building. The office had a glass partition and a steel mesh door leading onto the verandah. Mr McLean had an unimpeded view of the verandah. Mr McLean observed the worker in a distressed state leaning against one of the verandah posts. Mr McLean excused himself from the meeting and went to the worker's aid together with several other employees. Upon finding that the worker was in distress he retrieved his car and took him directly to the Mannum hospital as stated in par 2 above.

9 Although Mr McLean's statement (TB 49 - 50) indicates that he saw the worker coming out of the toilet block (TB 49), this is not accurate. Mr McLean agreed with Mr Kernot, counsel for the applicant, that the toilet block is set back from the verandah and that if the deceased was "coming out of the toilet" he would not have been in Mr McLean's line of sight from the room where the meeting was being conducted. Mr McLean explained that he made an assumption that the worker was coming from the toilets at the time that he observed him on the verandah because when he went to the worker's aid he had told Mr McLean "he was crook in the toilet" or something to that effect (tr 29).

10 No evidence was called by either party as to the deceased worker's whereabouts during the period between 10.00 am when he was last seen by Mr Ramm, and 10.30 am when Mr McLean came to his aid. I infer that there was no direct evidence available on that topic.

11 However Mr Ramm and Mr McLean gave evidence as to certain activities in which the worker may have engaged in the course of his duties in that period of time. In this respect I refer to the following:

"Wherever an inquiry has to be made into the cause of the death of a person, and, there being no direct evidence, recourse must be had to circumstantial evidence, any evidence as to the habits and ordinary doings of the deceased which may contribute to the circumstances by throwing light upon the probable cause of death is admissible, even in the case of a prosecution for murder." (Joy v Phillips, Mills and Co Limited (1916) 1 KB 849 per Phillimore LJ at 854)

12 As a draftsman much of the worker's time was spent on computer design of a piece of machinery known as a scaribar. His duties required him, on occasions, to go to the Research and Development shed some 30 - 40 metres from his office (tr 68) where certain prototype work was being carried out, and to the Scaribar Production area housed in a shed some 150 metres from his office. Mr McLean had seen the worker in the Research and Development shed on previous occasions. On such occasions he had never seen the worker lift anything heavy (tr 32) however he could not disagree that on occasions the worker may have lifted or pushed parts of the prototype (tr 33). If that was so, then it was Mr McLean's evidence that the parts would be small, weighing no more than 5 kilograms (tr 33). Nevertheless, he could not exclude the possibility that, on occasions, the worker may have lifted or pushed something heavy in either area. However, he considered that to be highly unlikely given the scope of the worker's duties, the presence of other employees and the availability of lifting devices (tr 36).

13 Mr Ramm's evidence was similar. He said that sometimes the worker went to the Research and Development shed several times on one day, and sometimes not for several days (tr 68). As to his visits to the Scaribar Production area he said those were less frequent (tr 68); perhaps more than a week between visits but sometimes twice in one day. Sometimes they would go together and sometimes not (tr 72). In the Scaribar Production area the worker's main activities were looking at how components worked and measuring and observing the machine in operation (tr 73). He did not recall that the worker was involved in lifting and pushing although he would occasionally help turn something over. Sometimes these components would be heavy, but lifting equipment was provided. He said he could not exclude the possibility that on occasions the worker moved heavy items in the shed. (tr 75) He could not, however, say whether it was likely or not that the worker went to the shed on that particular day (tr 75).

14 The focus of the medical evidence was the physiological process which led to the myocardial infarction that day. As part of that evidence Drs Sangster and Zimmet were each asked to express an opinion as to the likely effect of physical exertion on the progress of the worker's condition, and in particular, each was asked to consider the effect of activities of the kind described by Mr McLean and Mr Ramm. Each was asked to assume that the worker engaged in walking and heavy lifting or pushing in either location between 10.00 am and 10.30 am on the date of death.

15 The doctors were in agreement that at the date of death the deceased worker was suffering from atherosclerosis. As part of that condition he had pre-existing atheromatous plaque adhering to the inner lining of his coronary arteries. The plaque may have been narrowing the vessel to a small degree but prior to the date of his death, was asymptomatic. (tr 82).

16 Relying on the evidence of Dr Sangster (tr 82), with which Dr Zimmet basically agreed, I find that the most likely pathological sequence of events on this day was that, at a particular point, a few hours preceding death, the plaque developed a fissure, also known as a rupture, on the inner wall of a coronary artery, creating a rough surface. A process of deposition of platelets, that is sticky particles of blood, then occurred at that site forming a thrombus which occluded the artery, preventing the flow of blood to an area of the heart, resulting in death of heart muscle, and death. Although in this instance the thrombosis progressed to complete occlusion of the vessel and resultant death of heart muscle, that event was not inevitable. It may have been that the natural unclotting agents in the blood might have caused the thrombus forming on the plaque to dissolve, or temporarily dissolve, in which case complete occlusion may not have occurred at that time. (tr 82)

17 Drs Sangster and Zimmet agreed that when the worker complained to Mr Ramm that he was feeling unwell within the first hour of work, that was probably a premonitory symptom of the plaque fissure occurring. Dr Sangster described that it could have signalled a temporary narrowing of the vessel but not a complete occlusion "which subsequently evolved over the next hour or so to be the complete occlusion and subsequent infarction" (tr 83).

18 This is the point at which the views of Drs Zimmet and Sangster diverge and at which the question of the worker's activities that morning become relevant. Dr Zimmet expressed the view that once a plaque ruptures, setting in motion the pathological processes which result in the obstruction of the artery, the person is symptomatic and from then on there can be supplementary triggers which influence the progress of the condition (tr 43). It was his view that the sooner one seeks medical advice after the onset of symptoms the better the prognosis, and that assuming that the complaint of illness by the worker between 8.00 am and 10.00 am heralded the plaque fissure "his best practice then would have been to have sought medical advice and rested" (tr 44). In Dr Zimmet's view "any activity which is causing the heart to be not rested such as walking, exercise, is going to exacerbate the condition" (tr 43).

19 Dr Zimmet expressed the view that, if the deceased worker continued in his normal work at his desk for some unspecified length of time until at least 10.00 am, that may have aggravated his condition. Moreover, if between 10.00 am and 10.30 am, he had undertaken walking or lifting or other activity that increased his blood pressure and pulse rate, then that too could have triggered the acute occlusion with symptoms of chest pain and distress at 10.30 am. "I think any walking or any exercise in the setting of a person have (sic) an evolving infarct was probably not in the patient's best interest" (tr 52). His view, summarised in his final answer in his examination in chief, was :-

"I think the temporal relationship of his ultimate death to the fact that he had been at work in the preceding couple of hours would certainly raise a possibility that something at work could have triggered or exacerbated his underlying coronary artery disease". (tr 46)

20 Dr Sangster, on the other hand, expressed the view that, if the process had begun with the fissuring of the plaque prior to 10.00 am, it was unlikely that there would be any relationship between an activity such as walking and the progression of the occlusion and infarction.

"I think that that progression was an inevitable event and once that cascade began it relied on a balance within the internal factors controlling clotting and unclotting within the vessel, and that process inexorably began at that alleged or that likely time between 8.00 am and 10.00. Unless it could be shown that he did something very unusual in that hour or that half an hour after 10 o'clock and did some very heavy physical work of some sort, I don't think the effort of walking 50 or 100 metres would really have any more effect than a fact that whether he was sitting at his desk or having a cup of coffee".

21 In that context he described "very heavy physical work" as:-

"... a sudden effort such as running up a hill, lifting a heavy weight, something that would normally cause a person to be out of breath, feel that they've actually done some physical exertion ... a sudden burst of activity where his cardiovascular system is suddenly asked to undertake considerably more work than it was doing while he was sitting in the resting position". (tr 86)

22 It was Dr Sangster's view that once the plaque fissure occurred its progress to occlusion or not was determined by physiological factors such as the clotting mechanism unless the deceased was engaged in "extraordinary or unusual physical exertion which then put the heart under additional stress when it was already having the coronary artery circulation being reduced because of the temporary or complete occlusion, partial or complete occlusion of the vessel" (tr 86). He supported this view by referring to the use of exercise-testing for people with suspected coronary heart diseases indicating that in 25,000 exercise tests undertaken by his practice over 20 or so years, only 7 cardiac arrests had been precipitated.

23 Furthermore, Dr Sangster stated that if the worker was actually experiencing the occlusion with symptoms of chest pain and a feeling of being considerably unwell, it is unlikely that he would have wanted to voluntarily walk any distance. He also pointed out that it is not uncommon for patients having a heart attack to feel nauseated (tr 91).

24 Dr Sangster agreed with Mr Kernot that if the deceased worker lifted 35 - 50 kilograms in the Research and Development shed, that would fit his description of very significant exertion. So, too, would walking briskly to that area and then undertaking such lifting. Dr Sangster disagreed with the proposition that just being at work doing his normal computer duties would contribute or accelerate it. The last question put to him was "We cannot exclude work as being a contributing factor if we do not know what he was doing during that period" to which his answer was "That stands to reason, any more than we can say it was a contributing factor because we don't know what he was doing" (tr 103).

25 As to the competing medical opinions, I prefer the view expressed by Dr Sangster that some unusual physical exertion was required to change the course of the cascade of events commenced by the fissuring of the plaque. And that just walking 30 to 40 metres or 150 metres would not have been enough to do so and that something like running up a hill or lifting a heavy weight would be the kind of burst of activity needed to influence the cardiovascular system in that context. I reject Dr Zimmet's evidence that just being at his desk at work was sufficient physical exertion to aggravate or accelerate the worker's possibly impeding occlusion.

26 The relevant factual context in which Dr Sangster's opinion is to be applied is as follows; The worker was felling unwell prior to 10.00 am. The worker left his desk at 10.00 am. At some point in time between 10.00 am and 10.30 am the worker went to the toilets because he was "feeling crook". The complete occlusion occurred just prior to 10.30 am. As to his other activities during that period I am left with conjecture.

"One does not pass from the realm of conjecture into the realm of inference until some fact is found which positively suggests, that is to say provides a reason, special to the particular case under consideration, for thinking it is likely that in that actual case a specific event happened or a specific state of affairs existed." (Jones v Dunkel (1958 - [1959] HCA 8; 1959) 101 CLR 298 at 305 per Kitto J).

28 It is not appropriate to choose between guesses as to the worker's activities between 10.00 am and 10.30 am on 16 December 1996. It is preferable to take a broader perspective. I have already concluded that the only way that the worker's employment could have contributed to the myocardial infarction was if he engaged in unusual physical exertion of the kind referred to by Dr Sangster in the period leading up to the infarction. I find on the basis of the evidence of Messrs McLean and Ramm that unusual physical exertion was not a common or usual aspect of the worker's employment as a draftsman. I therefore find that, at any given time in his employment, it was much more likely that he was not engaged in unusual physical exertion, than that he was so engaged, and on that basis I find that it is more probable that he was not engaged in unusual physical activity during the period between 10.00 am and 10.30 am on 16 December 1996, and therefore that his employment did not contribute to the onset of the myocardial infarction and hence his death.

29 The respondent has discharged its onus. I conclude that the employment did not contribute to the onset of the myocardial infarction, and I dismiss the claim for compensation.

Parties are advised that if a party wishes to appeal against any part of this decision which is appealable pursuant to s 86(1) of the Act such appeal must be filed with the Registrar in accordance with Form 11 within 14 days of the delivery of this decision and must be served on all parties.