met his son to go out to eat, when he got to the restaurant, he did not feel well at all and left to go home. Upon his arrival at home, he took another nitro tablet and rested. He did not feel any better and continued to get worse at which time he decided to go to the hospital. Claimant was asked why nothing was noted on his trip report for May 15, 16, 17, 18 and 19, 1987 regarding carrying phone books. He indicated that he could not remember that far back. I asked what his farm duties consist of. He said he works on a dairy farm, feeds cattle and milks cows. He did not do any farm work on May 19, 1987 and has done very little farm work since. Since his heart attack, he has not worked for the Post Office. * * *99 By letter dated March 16, 1989, appellant submitted his medical records pertaining to his hospitalization from May 19 to May 30, 1987. In a May 28, 1987 report, Dr. Warren W. Cline, a Board-certified cardiologist, reviewed the history of appellant's condition in relevant part as follows: "[Appellant] has a very interesting history, as follows: He was previously admitted on January 1, 1985 with an unheralded acute inferior myocardial infarction which occurred while doing barn work.. 99 "The patient subsequently made a good recovery from his infarct, although he did experience some mild angina at high levels of exertion. He was periodically observed by treadmill stress tests, most recently in March 1987 which did not show ST [stress test] depression. "During recent weeks he has been unduly fatigued on mild exertion but has not experienced increasing chest pain until the day of admission when he developed a severe persistent pain, not relieved by nitroglycerin.* Dr. Cline concluded his report in relevant part as follows: "This patient has now sustained two episodes of myocardial infarction but does not appear to have residual complete occlusion of any major vessel. He had well-documented thrombotic occlusion of his dominant right coronary artery in January 1985 with excellent result from streptokinase thrombolysis and virtually no residual stenosis at the site of a documented thrombus. His recent infarct was clinically nontransmural anterolateral. He shows a high grade narrowing of the major diagonal branch of the LAD [left anterior descending artery] which was presumably occluded at the time of his infarct and he has additional narrowing of the main LAD. ***" On or about June 8, 1989, an Office medical adviser reviewed the medical evidence of record and submitted his opinion as follows: "In my opinion, the event of [appellant's] myocardial infarction at 5:00 a.m., 12 hours after he finished work was not specifically related to the work-related activities of the day prior. I think it is pure conjecture to state otherwise as no one has any accurate answers for this gentleman to help sort out the key question-was this work related or simply the natural history of the heart attacks? I think it was a natural and random occurrence. If this opinion is insufficient to satisfy the powers to be, I would recommend this chart to a cardiologist." By compensation order dated July 17, 1989, the Office, following a review of appellant's claim on the merits, denied modification of its January 7, 1988 compensation order on the ground that Dr. Hawkins' opinion on causal relationship was speculative and therefore insufficient to warrant modification of the prior order. The Board finds that appellant has not met his burden of proof in establishing that his May 19, 1987 heart attack was causally related to factors of his federal employment and, therefore, his May 19, 1987 heart attack is found not to have been sustained in the performance of duty. An employee seeking benefits under the Federal Employees' Compensation Act2 has the burden of establishing the essential elements of his or her claim including the fact that the individual is an "employee of the United States" within the meaning of the Act, that the claim was timely filed within the applicable time limitation period of the Act, that an injury was sustained in the performance of duty as alleged and that any disability and/or specific condition for which compensation is claimed are causally related to the employment injury. These are the essential elements of each 3 25 U.S.C. §§ 8101 et seq. 'Elaine Pendleton, 40 ECAB 1143 (1989). and every compensation claim regardless of whether the claim is predicated upon a traumatic injury or an occupational disease." To establish that an injury was sustained in the performance of duty in an occupational disease claim, a claimant must submit the following: (1) medical evidence establishing the presence or existence of the disease or condition for which compensation is claimed; (2) a factual statement identifying employment factors alleged to have caused or contributed to the presence or occurrence of the disease or condition; and (3) medical evidence establishing that the employment factors identified by the claimant were the proximate cause of the condition for which compensation is claimed or, stated differently, medical evidence establishing that the diagnosed condition is causally related to the employment factors identified by the claimant. The medical evidence required to establish a causal relationship, generally, is rationalized medical opinion evidence. Rationalized medical opinion evidence is medical evidence which includes a physician's rationalized opinion on the issue of whether there is a causal relationship between the claimant's diagnosed condition and the implicated employment factors. The opinion of the physician must be based on a complete factual and medical background of the claimant, 10 must be one of reasonable medical certainty," and must be supported by medical rationale explaining the nature of the relationship between the diagnosed condition and the specific employment factors identified by the claimant. 12 In the instant case, appellant submitted medical evidence establishing that he sustained a heart attack on May 19, 1987 and that this heart attack caused him disability for employment. Appellant *Id. The Office's regulations clarify that a traumatic injury refers to injury caused by a specific event or incident or series of events or incidents occurring within a single workday or work shift whereas occupational disease refers to injury produced by employment factors which occur or are present over a period longer than a single workday or shift. See 20 C.F.R. § 10.5(a)(15), (16). "See Ronald K. White, 37 ECAB 176, 178 (1985). 'See Walter D. Morehead, 31 ECAB 188, 194 (1979). The Office, as part of its adjudicatory function, must make findings of fact and a determination as to whether the implicated working conditions constitute employment factors prior to submitting the case record to a medical expert. See John A. Snowberger, 34 ECAB 1262, 1271 (1983); Rocco Izzo, 5 ECAB 161, 164 (1952). 'For a disease or condition to be compensable under the Federal Employees' Compensation Act, the condition must be shown to be proximately caused by the employment. See Arthur C. Hamer, 1 ECAB 62, 64 (1947). "Proximate cause' as used in the [Act] is used in its normal legal sense: that which, in a natural and unbroken sequence produces the injury, and without which, the injury would not have occurred." Georgia R. Cameron, 4 ECAB 311, 312 (1951). 'See generally Lloyd C. Wiggs, 32 ECAB 1023, 1029 (1981). 'The Board has held that in certain cases, where the causal connection is so obvious, expert medical testimony may be dispensed. See Naomi Lilly, 10 ECAB 560, 572-73 (1959). The instant case, however, is not a case of obvious causal connection. 10 William Nimitz, Jr., 30 ECAB 567, 570 (1979). 11 See Morris Scanlon, 11 ECAB 384, 385 (1960). 12 See William E. Enright, 31 ECAB 426, 430 (1980). also submitted several statements identifying the factors of employment which he believed caused or contributed to his May 19, 1987 heart attack. Specifically, appellant alleged that his work load increased in May 1987 when he was required to deliver both the yellow and white pages of telephone books to residents on his mail route and that this increased work load precipitated his May 19, 1987 heart attack. Because the employing establishment disputed appellant's statements regarding his work load immediately prior to his heart attack, the Office, as part of its adjudicatory function, 13 further developed the evidence on this issue and determined that appellant delivered telephone books as alleged from May 12 to 14, 1987 but that he did not deliver these books on the four days immediately preceding the May 19, 1987 heart attack. Appellant has not, however, submitted rationalized medical opinion, as heretofore described, which establishes a causal relationship between his May 1987 heart attack and the employment factors which he identified as causing or contributing to his condition. The only medical evidence which appellant submitted supporting a causal relationship between his May 19, 1987 heart attack and his employment was the August 15, 1988 deposition testimony of Dr. Hawkins, a Board-certified internist. Although Dr. Hawkins states that "it is reasonable to assume that there could be a causal connection" between appellant's May 19, 1987 heart attack and his increased work load during May 1987, he does not state that it is, in fact, his medical opinion, based upon reasonable medical certainty, that there is a causal connection between appellant's May 19, 1987 infarction and his increased work load in May 1987. Additionally, although Dr. Hawkins discusses how physical exertion may increase angina in individuals with severe coronary artery disease to a critical point thereby precipitating a myocardial infarction, Dr. Hawkins does not explain, with reference to specific medical findings in appellant's case, that this is how appellant's May 1987 myocardial infarction occurred. To be of probative value to appellant's claim, Dr. Hawkins' rationale must address the specifics, both factual and medical, of appellant's case. 14 For the foregoing reasons, Dr. Hawkins' testimony lacks sufficient probative value to discharge appellant's burden of proof. An award of compensation may not be based on surmise, conjecture or speculation. Neither the fact that appellant's condition became apparent during a period of employment nor the belief that 13 See supra note 6. 14 See William E. Enright, supra note 12. his condition was caused, precipitated or aggravated by his employment is sufficient to establish causal relationship.15 Causal relationship must be established by rationalized medical opinion evidence. Appellant failed to submit such evidence and the Office therefore properly denied appellant's claim for compensation. The decision of the Office of Workers' Compensation Programs dated July 17, 1989 is hereby affirmed. 15 Id. In the Matter of JOHN J. CARLONE and U.S. POSTAL SERVICE POST OFFICE, Providence, R.I. Docket No. 89-1438; Submitted on the Record; Before MICHAEL J. Walsh, David S. Gerson, The issue is whether appellant met his burden of proof in establishing that he sustained a left knee injury in the performance of duty on September 14, 1988. On September 14, 1988 appellant, then a 65-year-old custodian, filed a notice of traumatic injury and a claim for continuation of pay/compensation (Form CA-1), alleging that on September 14, 1988 he sustained an injury to his left knee while "carrying a mailbox [up the stairs] to the second floor." Appellant did not stop work. The claim form contained a statement of witness Norman Dawson who noted that appellant related having left knee pain after carrying a mailbox to the second floor of the employing establishment. On the reverse side of the claim form, appellant's acting supervisor noted that the employing establishment did not controvert the claim. On October 7, 1988, the employing establishment issued a request for examination and/or treatment, Form CA-16 authorizing treatment by Dr. Lyle J. Micheli, Board certified orthopedic surgeon, to "furnish office and/or hospital treatment as medically necessary for the effects of this injury." On the form received by the Office of Workers' Compensation Programs on October 14, 1988, Dr. Micheli noted that there was no history or evidence of concurrent or preexisting injury, disease or impairment, that he believed the condition found was caused or aggravated by the employment activity de |