Washington Food Specialties, Inc. (WFS) appeals an order of the Workmen’s Compensation Appeal Board (the Board) which affirmed a referee’s decision awarding disability and death benefits to Mary Britko, claimant and widow of Edward Britko (Britko). WFS contends that the referee and the Board erred as a matter of law in concluding that both heart attacks suffered by Britko were causally connected to work related stress. WFS also urges us to adopt a causal requirement of abnormal working conditions in stress related heart attack cases. We reject both arguments and affirm.
The facts of this case as found by the referee are as follows. WFS is owned by the Britko family and was incorporated in 1980. Britko was employed as president of WFS on February 22, 1984 when he suffered a heart attack which totally disabled him until September 30,1984. Britko returned to work for WFS on that date in a limited role and suffered a fatal heart attack on July 22,1985. Dr. Fagioletti, Britko’s treating physician, testified that Britko suffered from work related stress which was a factor in causing both the 1984 and the 1985 heart attacks. (Fagioletti Deposition [F.D.], at pp. 15-17, 50-51). Dr. Fagioletti also testified that the fatal 1985 heart attack was related to a progression of the disease process from the prior 1984 attack. (F.D., at p. 50). Dr. Hurwitz, testifying on behalf of WFS, stated that the 1985 heart attack was a direct result of the 1984 attack; further that the stress Britko suffered was in no way causally connected to either attack. (Hurwitz Deposition, at pp. 17,19). The referee made specific findings as to the cause of each heart attack: work related stress caused the February 22, 1984 attack; the second, fatal, heart attack was caused by the first heart attack and was not causally connected to stress from Britko’s return to work for WFS. This finding on causation is crucial because two separate insurance carriers insured WFS at the time of each heart attack. The referee’s finding makes the carrier at the *229time of the 1984 heart attack liable for both the disability and death benefits.
Our standard of review in this case is clear. We will examine the record to determine whether constitutional rights have been violated, an error of law has been committed, or necessary findings of fact are supported by substantial evidence. Monaci v. Workmen’s Compensation Appeal Board (Ward Trucking), 116 Pa.Commonwealth Ct. 172, 174, 541 A.2d 60, 62 (1988). The referee may accept or reject the testimony of any witness, in whole or in part. Walzer v. Workmen’s Compensation Appeal Board (Globe Security, Inc.), 69 Pa.Commonwealth Ct. 468, 473, 451 A.2d 799, 802 (1982).
WFS attacks the referee’s finding that the fatal heart attack was work related on three fronts. Initially, WFS asserts that the evidence indicates that the stress Britko suffered from was entrepreneurial and family related rather than work related. As noted above, Dr. Fagioletti testified that Britko suffered from work related stress in 1984 which was a major factor in causing the first heart attack. Dr. Fagioletti admitted that the work related stress Britko suffered from also impacted him in his capacity as head of the family, especially because the business was family owned. (F.D. at 17). WFS concludes that this testimony dictates a finding that the stress Britko suffered from was not work related within the meaning of Section 301(c) of The Pennsylvania Workmen’s Compensation Act. Act of June 2, 1915, P.L. 736, as amended, 77 P.S. § 411(1). We disagree.
WFS relies upon Klein v. Workmen’s Compensation Appeal Board (Plaza Home Center, Inc.), 91 Pa.Commonwealth Ct. 247, 496 A.2d 1346 (1985) and McCoy v. Workmen’s Compensation Appeal Board (McCoy Catering Services, Inc.), 102 Pa.Commonwealth Ct. 436, 518 A.2d 883 (1986), petition for allowance of appeal denied, 517 Pa. 595, 535 A.2d 84 (1987), as establishing that all stress suffered by the owner-employee of a family owned corporation is entrepreneurial and family related, not work related *230and thus, cannot cause a work related, compensable injury. We find those cases distinguishable. Both Klein and McCoy deal with stress caused mental injuries and are in the so-called psychic cause/psychic injury or mental cause/mental injury category of claims. Klein, 91 Pa.Commonwealth Ct. at 249, 496 A.2d at 1347; McCoy at 441, 518 A.2d at 885. Here we are presented with a stress induced heart attack, a psychic cause/physical injury claim. Once a causal connection between a heart attack and employment duties is established, compensation follows. Krawchuk v. Philadelphia Electric Co., 497 Pa. 115, 121-24, 439 A.2d 627, 630-32 (1981). We will not extend application of the Klein and McCoy reasoning concerning psychic cause/psychic injury or mental cause/mental injury to the facts of this case.1
WFS also argues that Dr. Fagioletti’s testimony is equivocal. The equivocality of a medical opinion is a question of law, fully reviewable by this Court. Bethlehem Steel Corp. v. Workmen’s Compensation Appeal Board (Tompkins), 66 Pa.Commonwealth Ct. 579, 581, 445 A.2d 843, 845 (1985). WFS asserts that Dr. Fagioletti’s admission that Britko did not discuss all the sources of his stress renders the Doctor’s opinion equivocal. Dr. Fagioletti did testify that Britko had a family problem which he did not specifically identify. (F.D. at 16). Dr. Fagioletti went on to state that, although not specifically identified, this problem was involved in the operation of the family business. (F.D. at 17). That Britko did not specify all the sources of this stress to Dr. Fagioletti does not render the doctor’s opinion *231that work related stress caused the first heart attack equivocal.
WFS’s final attack on the referee’s findings asserts that substantial evidence does not support the chain of causation accepted by the referee for the second fatal heart attack. Again we disagree. The referee found that work related stress caused the first heart attack and that the second, fatal heart attack was a direct result of the first attack. The referee also expressly excluded work related stress as a cause of the second heart attack. The testimony outlined above supports this finding. Dr. Fagioletti testified that work related stress was a major contributing cause to both heart attacks and that the first heart attack was a contributing factor to the second. Dr. Hurwitz stated that the second heart attack was a direct result of the first. There was also testimony that Britko returned to work in only a limited role following the first heart attack. The referee was free to accept Dr. Fagioletti’s testimony that work related stress caused the first heart attack and Dr. Hurwitz’s testimony that the first heart attack caused the second attack. Walzer, 69 Pa.Commonwealth Ct. at 473, 451 A.2d at 802. WFS noting that the referee credited Dr. Hurwitz’s testimony only where consistent with Dr. Fagioletti’s does not fatally flaw this analysis as both doctors stated that the 1984 heart attack was a contributing factor to the fatal 1985 heart attack. Thus, substantial evidence supports the referee’s finding regarding the cause of the July 22, 1985, fatal heart attack.
As a final issue, WFS urges us to require claimants to show that abnormal working conditions gave rise to the stress which causes a heart attack before compensation is allowed. WFS cites us to a number of heart attack cases where the claimants offered evidence of excessive stress which caused the heart attack. Unquestionably, a showing of overwhelming stress is an effective method of proving the necessary causal connection; it is not, however, a prerequisite to recovery. Abnormal working conditions are a requirement in psychic cause/psychic injury claims only. *232Just as we refuse to extend the reasoning of the Klein and McCoy cases to stress induced heart attack cases, we refuse to require a showing of abnormal working conditions before awarding compensation for these type of claims. Moreover, our Supreme Court has held that a claimant need only show a causal connection between work stress and a heart attack. Krawchuk, 497 Pa. at 125, 439 A.2d at 632 (victim’s normal work, as well as special projects, constituted stress, rendering stress induced heart attack compensable). As an intermediate appellate court, we are powerless to impose a more stringent requirement concerning abnormal working conditions in stress induced heart attack cases.
Affirmed.
ORDER
NOW, December 19, 1991, the order of the Workmen’s Compensation Appeal Board, dated, November 30, 1990, at No. A-97514, is affirmed.
. WFS also calls our attention to Kemp v. Workmen’s Compensation Appeal Board (Elkland Electric Co.), 121 Pa.Commonwealth Ct. 23, 549 A.2d 1365 (1988) petition for allowance of appeal denied, 523 Pa. 652, 567 A.2d 655 (1989). Kemp is also distinguishable as another psychic cause/psychic injury case. Further, the crux of the Kemp decision is the claimant’s failure to show abnormal working conditions. Id. 121 Pa.Commonwealth Ct. at 27, 549 A.2d at 1367. The Kemp Court’s discussion of the claimant’s physical symptoms being caused by anxiety over the future instead of work related stress is clearly dicta because the claim petition alleged psychic injury, not physical injury. Id., 121 Pa.Commonwealth Ct. at 24, 549 A.2d at 1366.