Decision #86/10 - Type: Workers Compensation
Preamble
The worker is currently appealing a decision made by Review Office of the Workers Compensation Board which determined that the heart attack (referred to as well as "myocardial infarction" or "MI") he sustained on July 9, 2008 did not arise out of and in the course of his employment. The worker disagreed with the decision and an appeal was filed by the Worker Advisor Office to the Appeal Commission. A hearing was held on July 13, 2010 to consider the matter.Issue
Whether or not the claim is acceptable.Decision
That the claim is acceptable.Decision: Unanimous
Background
On July 17, 2008, the worker reported to the WCB that he suffered a heart attack at work on July 9, 2008 while operating a scoop tram when working underground in a mine.
When speaking with a WCB adjudicator on August 11, 2008, the worker indicated that he started to develop a burning sensation in his chest about a half hour into his shift on July 9, 2008. He was later taken to the hospital and was advised that he suffered a heart attack. The worker indicated that his regular job duties included drilling, blasting, operating a scoop tram, walking and climbing ladders. On the day of accident, the worker indicated that he did not do any drilling but was operating the scoop tram.
On October 1, 2008, a WCB internal medicine consultant reviewed the medical information on file and noted that the worker’s risk factors included positive family history, high cholesterol level and cigarette smoking. He indicated that the diagnosis was an acute MI. He indicated that the worker was not engaged in unusual activity on the day that he suffered the MI. He stated, “The angiogram did not reveal an acutely occluding lesion such as a thrombus or bleed. Moreover the ST elevation resolved without the use of thrombolytic agent. I therefore suspect spasm as the cause of acute interruption of the blood flow through severely narrowed LAD and second diagonal vessels. Spasm in the blood vessel could occur independent of physical activity.”
In a decision dated October 21, 2008, the worker was advised that the WCB was not accepting responsibility for his claim as it was determined that his work duties were not the cause of his heart attack. When making the decision, the adjudicator referred to the medical opinion outlined by the WCB’s internal medicine consultant on October 1, 2008. On November 11, 2008, the worker appealed the decision to Review Office.
On November 27, 2008, a WCB review officer spoke with the worker by phone as he indicated on his appeal form that there was a change in his job duties. The worker stated that he normally does drilling. Two days prior to his heart attack, he was assigned different duties consisting of rebarring and putting up rock bolting. He and others were at the bottom of the mine blasting and working to “blast and build” a lunch/open space area. During these two days, there were issues with poor air quality. There were a lot of exhaust fumes in the area. Two trucks and 1 to 2 scoop trams were running at all times, which added to the level of fumes to which he was exposed. It was also very hot. Because of safety regulations, fans were not allowed to run while they were blasting. He indicated that putting up the link fencing and netting where the rocks were bolted was very strenuous and was not part of his regular job duties. On the day of his heart attack, the worker was driving the scoop tram when he experienced chest pain. He said he did feel chest pain the day prior but it was not severe. The worker indicated that he was relating his heart attack to the noxious fumes he was exposed to and to the strenuous job duties he performed a couple days prior to the heart attack. Review Office advised the worker that it was referring his case back to primary adjudication to consider the new information he had just provided.
File records showed that primary adjudication contacted a site supervisor on February 13, 2009 who confirmed the worker’s regular job duties and the duties the worker performed on the day of his heart attack. He confirmed there was a change in the worker’s duties 2 days prior to the date of accident, as described by the worker. He stated that these duties would be no more strenuous than the worker’s regular duties of drilling. He confirmed that it was hot and somewhat smoky in the air but that it was no different than usual over these days. He was not aware of any ventilation problems at the time.
The WCB’s internal medicine consultant reviewed the new file information on April 8, 2009. He noted that if there were diesel motors running then there was a possibility of a carbon monoxide build up in the area. Air quality studies were needed to confirm this. He stated that exposure to carbon monoxide could cause hypoxemia and deprive the myocardium of oxygen. He noted that the worker had critical stenosis of the left anterior descending branch of the left coronary artery which supplied the antero-septal area of the myocardium. This was the area of infarction. He stated that the combination of critical narrowing and reduced available oxygen in the blood may have resulted in the infarction of the area. This scenario became more likely if the worker was performing an unusual task requiring more effort thus more oxygen.
Primary adjudication made contact with the accident employer and was unable to substantiate that there was a problem with the ventilation system around the date of accident.
On May 14, 2009, the WCB’s internal medicine consultant stated, in part:
“…I was looking for the chemical analysis of the air in the environment specifically the percentage of carbon-monoxide and oxygen. Lower than normal oxygen level together with carbon-monoxide in the environment will cause hypoexemia and infarction. I therefore suspect the scenario I outlined previously (HSR of February 17) is plausible and the injury is thus work related…”
On June 4, 2009, the worker advised a WCB case manager that at the time of the onset of symptoms, he was using a one yard scoop tram to backblade a drift round. It was a small 9' x 10' drift approximately 80 feet long. There was no other equipment in operation at his location, and the nearest crosscut was 80 feet back. He said the air in his location was provided through small vent tubing powered by an air fan. The air was drawn from an area that was fed by two larger vent tubes. There was other equipment operating in the other work areas, model 413 trucks and 3 yard scoop trams. He noted that there was significant heat from the rock at 6800 feet.
On June 23, 2009, the employer advised primary adjudication that the worker was working in a new heading and that the air flow was adequate for the equipment that was there. There were regular inspections by the mines inspector. All the machines had scrubbers on the exhaust. The employer indicated that they do measure the oxygen levels but do not record the readings if they are adequate. The procedure was to shutdown the heading if the oxygen level was below 19. There were not any shutdowns in the period in question. The lowest reading was 21, to his recollection.
On June 23, 2009, the worker was advised by primary adjudication that no change would be made to the previous decision based on the following points:
· information from the employer that fresh air was provided from surface through the ventilation shaft and was monitored on a regular basis to ensure sufficient air flow and oxygen content;
· the medical information which showed that the worker had cardiac risk factors that were not related to his employment, and therefore it could not be determined that the worker’s employment was the dominant cause of his underlying cardiac condition; and
· the worker reported that he started work at 7 p.m. on July 9, 2008 and the medical information indicated that his chest pain started at 6 p.m.
Based on the above factors, primary adjudication determined that since the worker’s symptoms occurred prior to starting work on July 9, 2008 and his underlying cardiac condition was not related to his employment, the claim could not be accepted.
On September 15, 2009, a worker advisor appealed the June 23, 2009 decision to Review Office. The worker advisor submitted that the evidence on file supported that the worker’s injury arose out of and in the course of his employment. He stated that while the WCB relied on personal risk factors to deny responsibility for the MI, the inadequate air quality combined with the worker’s efforts to work at a faster pace caused his heart to fail. It was suggested that the worker’s accident was consistent with the scenario provided by the WCB’s internal medicine consultant which provided additional credence to the appeal.
In a decision dated November 12, 2009, Review Office confirmed that the worker’s claim was not acceptable. Review Office outlined the opinion that the worker’s MI sustained on July 9, 2008 did not arise out of his employment but rather occurred as a result of his underlying ischaemic heart disease without any material contribution by work related factors. In making its decision, Review Office noted that the presence of high carbon monoxide levels in the workplace had not been proven, that the ventilation system in the area in question was operating correctly and that the worker had not been performing any strenuous activity on the date of the MI. On November 26, 2009, the worker advisor appealed Review Office’s decision to the Appeal Commission and a hearing was arranged.
In April and June 2010, the Worker Advisor Office submitted new information for the panel’s consideration. These included a statement from a co-worker who was present at the time of the worker’s MI on July 9, 2008, a report from an occupational health physician dated January 13, 2010 and literature pertaining to heart attack treatment.
Reasons
Applicable Legislation and Policy
The Appeal Commission and its panels are bound by The Workers Compensation Act (the “Act”), any supporting Regulations, and policies enacted by the WCB Board of Directors.
The worker's appeal deals with whether or not he has an acceptable claim with the WCB.
Subsections 1(1) and 4(1) of the Act set out the circumstances under which claims for injuries can be accepted by the Board, and state that the worker must have suffered an accident that arose out of and in the course of employment. Once such an accident has been established, the worker would then be entitled to the benefits provided under the Act.
WCB Policy 44.10.20.10, Pre-Existing Conditions clarifies that the WCB will accept responsibility for an accident that is caused in part by a compensable accident and in part by a pre-existing (non-compensable) medical condition.
The Worker's Position:
The worker was represented by a worker advisor. In response to questioning by his advocate and by the panel, the worker provided considerable detailed evidence as to his general job duties, the types of equipment he was using, and the layout and environment of the area of the mine in which he was working. He advised that he was working to open up a new area of the mine. It was the deepest point of the mine, some 6300 feet below the surface. In lay terms, the worker described the mining area as having the shape of an octopus. There was a central hub area approximately 150' in diameter, from which four drifts (tunnels) were being drilled. The drifts were still quite short, with the longest being 150' in length. The worker's job was in one of the drifts, which was about 80' in length. The drifts are quite small in dimensions, usually 8' wide x 8' high, or 8' x 10'.
The worker described the cycle of work activities involved in developing and extending a drift. The first job each day usually involved the cleaning up of areas that had been blasted at the end of the previous shift, using a mechanized vehicle called a scoop tram. The cycle continues with the miner carrying in and using equipment to drill new holes, either ahead of him or above him. This equipment is heavy and awkward to handle. The miner then packs the holes with blasting powder. The blast is done at the end of the shift because no work can be done in the area after a blast. The blasts result in a tremendous amount of dust and debris, and those areas were considered unsafe and not accessible for up to 3 to 5 hours after the blast.
The worker advised that the vehicles operated by him and the other miners operating in the new area are all diesel fuel operated, and that on July 9, 2009, the exhaust was so thick that headlights of other vehicles appeared orange in the smoky fog that filled the air. The worker also described the fresh air supply system involved nylon-type venting pipe that was attached to the existing air supply system. The worker noted that the ducting was in poor condition with many tears, and that there was almost no air pressure at the end of the pipe. The worker advisor indicated that a co-worker who provided an email statement to the WCB on March 28, 2010 corroborates the extremely poor air delivery system in that area of the mine, and in particular the concern that poor air was being recirculated in the air delivery system. Neither the worker nor his co-worker had any recollections of that area being monitored for air quality, and that in new areas monitoring was usually done after worker complaints were made.
The worker described in detail his job duties in the previous two days, at which time he was performing the cycle of duties noted above. He felt that these duties were in part responsible for his heart attack. The worker also believed that his 29 years of work in a mining environment were responsible for his cardiovascular disease. The panel notes however that the worker advisor did not pursue this line of argument.
On the morning of his heart attack, the worker had had spent an hour travelling down the mine to his work location, and had immediately started work on the scoop tram. Shortly into his shift, he began to have chest difficulties which were later diagnosed as a heart attack. The worker indicated that the air quality was extremely poor at that time. It was extremely hot, and there was a lot of dust in the air from the previous blast and from the debris being shoveled by the scoop tram. There were three scoop trams in operation in that general area, going in and out of the drifts to load the idling diesel-run trucks that would take turns hauling the debris out of the mine.
The worker advisor's position is that the work duties met the air quality scenarios outlined by the two doctors involved in the file, and that the worker's myocardial infarction was therefore work-related.
Analysis:
For the worker to succeed in his appeal, the panel would have to find that the worker's heart attack was caused at least in part by some hazard of his employment. The panel was able to make this finding, on a balance of probabilities, for the reasons that follow.
In the panel's review of the file, there appears to be a general medical consensus as to the nature and status of the worker's underlying cardiovascular system prior to July 9, 2008, the date when the worker suffered his heart attack. There is also a consensus as to exactly how the heart attack occurred. As noted by an occupational health physician in his report of January 13, 2010 and a WCB internal medicine consultant in his memos of February 17, 2009 and May 14, 2009, the worker had severe and long lasting cardiovascular disease which pre-existed the acute heart attack on July 9, 2008. One of its features was pre-existing narrowing or occlusion of the coronary arteries. As to what happened on the morning of July 9, 2008, there is consensus that the heart attack was caused by muscle spasm. These opinions are uncontroverted, and the panel therefore accepts these opinions and finds that the worker had a severe pre-existing cardiovascular disease with narrowing of the arteries, and that he suffered a muscle spasm on July 9, 2008 which caused his heart attack.
The question that remains is as to the cause of that muscle spasm, and in particular whether or not it was caused by some hazard of the worker's employment (such as the work environment or his job duties) or by some other cause. Two physicians on the file suggest possible causes for the muscle spasm. They comment in particular about what work conditions in a mine might lead to a myocardial infarction:
· A memo prepared by a WCB internal medicine consultant February 17, 2009 indicates,
"He developed chest pain while operating the scoop. I am not sure how much effort is required to operate the scoop. There were other machinery operating there and the air was smoky. If the there (sic) were diesel motors running then there is possibility of carbon-monoxide build up in the area. Thus we need air quality study to confirm this. Exposure to CO could cause hypoxemia and deprive the myocardium of oxygen. The claimant had critical stenosis of left anterior descending branch of the Left coronary artery which supplies the antero-septal area of the myocardium. This was the area of infarction. Thus a combination of critical narrowing and reduced available oxygen in the blood may have resulted in the infarction of the area…."
· A later memo by the consultant dated May 14, 2009 indicates that "lower levels of oxygen together with carbon monoxide in the environment will cause hypoxemia and infarction. I, therefore, suspect the scenario I outlined previously (HSR of Feb 17) is plausible and the injury is work related."
· A report by an occupational health physician dated January 13, 2010 notes that:
"Myocardial infarctions (MI) are caused by an imbalance between the supply of blood and oxygen to the heart and the demands of the heart. Your angiogram did not reveal acute blockage, but 90% stenosis, suggesting that spasm or a temporary vascular occlusion caused your event. You have some risk factors for cardiovascular disease including smoking, hypertension, hyperchloresterema. These risk factors are the most likely cause of the underlying narrowing in the arteries that was seen in your angiogram. Your work is generally physical, however, there did not appear to be any new tasks at the time of your heart attack that may have predisposed you to develop one. However, you did appear to work in an area which may have had poor quality air. The exact extent of the poor quality air is unknown.
Quality of air is influenced by a number of factors these include the levels of oxygen, carbon monoxide and particulates amongst others. You reported that the air was dusty. Air measurements, however, are not available from around the time of your heart attack. At other times in the mine it appears that oxygen levels were not low, however, there is no mention of carbon monoxide levels or particulates. Although the air quality in the mine may not have been worse than usual, this does not mean that it was good. I agree with [the WCB internal medical consultant]'s assessment, that low oxygen or a build up of carbon monoxide could have contributed to your development of a myocardial infarction, however, air pollution itself has been associated with increasing risk of cardiovascular disease…"
In our assessment of all the evidence on file and presented at the hearing, the panel accepts that the worker's MI was caused by a combination of pre-existing arterial narrowing and muscle spasm. Muscle spasm was contributed to by the following work factors:
· On the day of his heart attack the worker was working at the extreme bottom of the mine which has not yet been developed, 6300 feet below the surface. It was a very hot environment, between 95F and 115F, simply because of the depth of the mine, plus the heat generated by the vehicles used in a fairly small space.
· The worker was operating an older diesel-powered scoop tram in a very tight enclosed area. He was working to clear the end of an 80 foot drift, and travelling in and out of the drift which was 8 feet by 8 feet in width and height. The machine was leaking and burning oil and there was diesel exhaust continuously emitted in that small area. The diesel fumes generated by the worker's scoop tram were augmented by the two other scoop trams and an idling diesel-run truck that was being filled with debris in the hub, all in a new small area of the mine.
· There was very limited airflow in the area. Each tunnel was equipped with a 12" vent, and there were temporary air inflow and venting systems which, from the evidence presented, were not in good condition.
· Unlike other areas of the mine, this new area did not have an established ventilation system, nor was it regularly monitored for air quality. The panel notes that the mine operator was unable to provide air quality monitoring reports for this area, but it is our view that the absence of data does not mean that a problem did not exist in that area.
Overall, the panel finds that the prerequisites described by the WCB internal medicine specialist and the occupational health physician for a work-related myocardial infarction were met. The panel finds that poor air quality contributed to the worker having a muscle spasm due to lack of oxygen, high carbon monoxide, and high particulate. This muscle spasm was a compensable accident overlaid on a pre-existing cardiovascular disease, and thus meets the definition of an accident under the Act and WCB policy. Accordingly, the worker's appeal for the acceptance of his claim is successful.
Panel Members
L. Choy, Presiding OfficerA. Finkel, Commissioner
P. Walker, Commissioner
Recording Secretary, B. Kosc
L. Choy - Presiding Officer
Signed at Winnipeg this 9th day of September, 2010