The opinion of the court was delivered by
This is an appeal from an award of benefits by the Workers Compensation Board (Board)..Mary Sue Mudd was a nurse at the Neosho Memorial Regional Medical Center (Neosho) who died after suffering a rupture of a cerebral aneurysm (stroke) at work. An administrative law judge (ALJ) denied the claim for benefits filed by her surviving spouse and dependent children. The Board reversed, and Neosho appealed. We granted the motion to transfer from the Court of Appeals under K.S.A. 20-3017.
The parties present three issues on appeal. First, does the record contain substantial competent evidence to support the Board’s finding that Mudd’s stroke met the “unusual exertion” requirement of the heart amendment of the Workers Compensation Act: K.S.A. 44-501(e)P Second, does “stress” qualify as an external factor which makes the heart amendment irrelevant to Mudd’s claim? Third, is the heart amendment unconstitutional?
We hold there is not substantial competent evidence to support the unusual exertion finding, that stress does not qualify as an external factor, and that the heart amendment is constitutional. We therefore reverse.
FACTS
Mudd was a 47-year-old registered nurse employed for more than 10 years by Neosho. She worked in the intensive care unit and the emergency room. While at Neosho, Mudd was called upon *189 to respond to “code blues,” which required her to stop what she was doing and run to help resuscitate a dying patient.
During the 6 months prior to September 13,1999,19 code blues had occurred at Neosho. Mudd was involved in responding to seven of them. Her husband, Wayne, testified that she was required to run to code blues and afterward she would be upset, stressed, and unable to sleep, sometimes for days after the event.
On September 13, 1999, Mudd became ill while responding to a code blue and passed out. She was initially treated at Neosho by Dr. Gehrt who performed a spinal tap and found blood in her spinal fluid. Mudd was transferred to Via Christi Regional Medical Center in Wichita. There, Dr. Schwertfeger concluded that she had suffered a cerebrovascular stroke. She died on September 23, 1999.
Dr. Schwertfeger testified that Mudd’s stroke was likely the result of a preexisting aneurysm, which is a weakening of a blood vessel wall. According to him, the weak area develops a bulge and eventually ruptures, typically following some sort of exertion or stress which causes an elevation in blood pressure. He stated that running to respond to a code blue would potentially cause an increase in blood pressure and that responding to a code blue was within the normal scope of the duties of an ICU nurse. Dr. Schwertfeger testified regarding his conclusions as follows:
"Q. Do you have an opinion within a reasonable degree of medical certainty, which means more likely than not, whether her activity and stress of running to respond to a code blue precipitated her stroke?
“A. It would be conditions that would be conducive to a subarachnoid hemorrhage in a patient predisposed to that.
“Q. So you would say that it is more likely than not that the exertion of this lady running to respond to a code blue was a factor in precipitating her stroke?
“A. It would be a factor I believe, yes.”
Mudd’s surviving spouse and dependent children sought survivors’ benefits under the Workers Compensation Act. The ALJ denied their claim, finding that they had not met their burden of proving an unusual exertion caused her aneuiysm to fail. He therefore concluded “[t]hat the claimant was acting within the course *190 of her ‘usual work’ and her ‘regular employment’ when she suffered her cerebrovascular stroke.”
After the claimants appealed, the Board reversed and entered an award for them. It found that the exertion from running to respond to a code blue was something that occurred on average only once a month while Mudd was on duty. In addition, the Board found that running was an unusual activity for Mudd and that the running constituted unusual exertion within the meaning of K.S.A. 44-501(e). It further found that she suffered “heightened stress when responding to a code blue,” and that “[t]his unusual stress . . . contributed to the unusual level of exertion and, in addition, constituted an external force within the meaning of the heart amendment.” Finally, the Board found that the stress, combined with the running, elevated decedent’s blood pressure and, more likely than not, precipitated the rupture of the aneurysm while Mudd was responding to the code blue. Neosho and its insurance carrier appealed.
DISCUSSION
Issue 1: Does the record contain substantial competent evidence to support the Board’s finding that Mudd’s stroke met the “unusual exertion” requirement of the heart amendment?
The Board found that the claim based upon Mudd’s stroke was compensable under K.S.A. 44-501. Specifically, the Board found claimants met the requirements of subsection (e), the so-called heart amendment, which states:
“Compensation shall not be paid in case of coronary or coronary artery disease or cerebrovascular injury unless it is shown that the exertion of the work necessary to precipitate the disability was more than the employee’s usual work in the course of the employee’s regular employment.”
The legislature passed this amendment in 1967. L. 1967, ch. 280, sec. 1. Its general purpose was to limit compensability for heart and stroke cases and reverse a long line of Supreme Court decisions in which compensation was awarded even though preexisting heart or vascular conditions may have been a predisposing factor. See
Dial v. C.V. Dome Co.,
Accordingly, claimants since 1967 have borne the burden of proof to demonstrate injuries in this category arose out of something more than the exertion required of their usual work in the course of their regular employment.
In the case at hand, the Board found that the exertion from running to respond to a code blue was something that occurred on average only once a month while Mudd was on duty. In addition, the Board found that running was an unusual activity for Mudd and that the running constituted unusual exertion. Finally, it found that Mudd suffered “heightened stress when responding to a code blue,” and that “[tjhis unusual stress . . . contributed to the unusual level of exertion.” These determinations are questions of fact. See
Suhm v. Volks Homes, Inc.,
Our review of questions of fact is limited to determining whether they are supported by substantial competent evidence.
Despite this deferential standard of review, we hold as a matter of law that the record does not contain substantial competent evidence to support several of the Board’s key findings: that running was an unusual activity for Mudd, that the running constituted unusual exertion, that Mudd suffered “heightened” stress when responding to a code blue, and that this “unusual stress” contributed to the unusual level of exertion. As mentioned, the law requires the claimant to show “ ‘that the exertion of the work necessary to precipitate the disability was
more than the [employee’s] usual work
in the course of [the employee’s] regular employment.’ ” (Emphasis added.)
The record is devoid of any evidence, however, of Nurse Mudd’s work history which would demonstrate her usual work or the level of exertion required to perform these usual duties. The record simply reveals that on the day in question, for the seventh time in 6 months she ran an unknown distance to a code blue, that she had previously found this activity stressful, and that the running and stress contributed to her stroke. Without a baseline of what is usual for her, there can be no determination of what is unusual for her, particularly when “[u]nusualness may be a matter of degree and may appear in the duration, strenuousness, distance or other circumstances involved in the work.”
Claimants simply failed to meet their burden of proof as defined in K.S.A. 44-508(g): “to persuade the trier of facts by a preponderance of the credible evidence that such party’s position on an issue is more probably true than not true on the basis of the whole record.” Likewise, in
Calvert v. Darby Corporation,
Additionally, even if claimants had established through Mudd’s work history the requisite baseline for her work and exertion, we question whether they would have been able to meet their burden of proof to establish that the code blue and its accompanying stress on September 13,1999, sufficiently exceeded this baseline to qualify as unusual. For example, Mudd’s own physician, Dr. Schwertfeger, testified that responding to a code blue was within the normal scope of the duties of an ICU nurse, i.e., part of Mudd’s usual job. Moreover, since K.S.A. 44-501(e) does not require a certain task to be done daily for it to fit the definition of “usual work,” Mudd’s husband’s testimony that she was required to run to code blues, coupled with the stipulation that she had responded to seven code blues during the 6 months before her stroke, strongly suggests this activity was not unusual.
Issue 2: Does “stress” qualify as an external factor which makes the heart amendment irrelevant to claimants’ claim?
Six years after the legislature’s passage of the heart amendment, we held it did not apply unless the exertion of the work was the precipitating cause of the disability.
Dial v.
C.V.
Dome Co.,
Whether an external force or agency produced a worker’s disability is a question of fact.
Suhm,
We begin our analysis by identifying the required elements for external force described in
Makalous v. Kansas State Highway Commission,
“To support a finding that claimant’s cardiac or vascular injury is the product of some extreme external force, [1] the presence of a substantial external force in the working environment must be established and [2] there must be expert medical testimony that the external force was a substantial causative factor in producing the injury and resulting disability.”
In the case at hand, Dr. Schwertfeger’s testimony establishes the element of causation: “[H]er activity and stress of running to respond to a code blue . . . would be conditions that would be conducive to a subarachnoid hemorrhage.” His testimony, though contradicted by defendants’ physician, Dr. Pfuetze, was found more persuasive by the Board and is therefore binding on this court since we do not reweigh evidence or determine credibility of witnesses.
Griffin,
For the Board’s determination of tire other element, the presence of an external force, it relied upon two cases. It first observed, “[i]n dicta, the Kansas Supreme Court in
Dial v. C.V. Dome Co.,
In addition to our examining
Suhm’s
implications and
Dial’s
acknowledged dicta, however, we must also look to other Kansas law for guidance. The bedrock of our examination is our oft-stated
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acknowledgment of the legislative purpose of the 1967 heart amendment: to limit compensability for heart and stroke cases and reverse a long line of decisions in which compensation was awarded even though preexisting heart or vascular conditions may have been a predisposing factor. See
Makalous v. Kansas State Highway Com
mission.,
Our examination continues with a recognition of similarly limiting legislative action taken in 1987: the addition of subsection “g” to K.S.A. 44-501. L. 1987, ch. 187, sec. 1. It states in relevant part: “The provisions of the workers compensation act shall be applied impartially to both employers and employees in cases arising hereunder.” The addition changed the course of case law which had required courts to tilt somewhat in favor of the employee: to “liberally construe the workers compensation statutes to award compensation to the worker where it was reasonably possible to do so.”
Nguyen v. IBP, Inc.,
Our continuing review reveals not only the acknowledged dicta in
Dial
relied upon by the Board, but also our additional statements made there, e.g., an external force is “wholly independent of the workman’s exertion.”
Consistent with these prior conclusions and reaffirmations, to date we have decided that only “oppressive heat” and “freezing cold and windy weather” qualify as external forces,
i.e.,
external to the claimant’s work exertion. See
Dial; Makalous.
Moreover, the example cited by the
Dial
court is similarly external to the workers’ exertion: After a worker is confronted by an armed assailant bent on robbery, he suffers a heart attack because of the natural fear and anxiety.
In the case at hand, Mudd’s own physician testified that the stress was not external to her exertion, but actually combined with it. We therefore hold that stress cannot, as a matter of law, be an external factor under these facts. Any suggestion or implication to the contrary in our prior decisions is overruled. To hold otherwise would be to eviscerate the heart amendment. For example, a stroke or heart attack claimant who has unsuccessfully tried to prove the statutory requirement of unusual exertion could nevertheless prevail by instead showing the cause of the injuiy was merely the usual (though “substantial” per Makalous) stress of her work at the time.
While stress does not qualify under these circumstances as an external factor, claimants are not totally without recourse. They may still demonstrate that the stress was caused by factors external to Mudd’s exertion, e.g., the armed assailant or the falling beam in Dial’s examples. In addition, they may still show unusual work or unusual exertion which was a causative factor of the unusual stress. Similarly, although not emphasized by the parties as a separate basis for compensation, the Board found that Mudd suffered heightened/unusual stress while responding to the code blue and that it contributed to her unusual level of exertion. We hold, however, that this Board finding of “unusual stress” is not supported by substantial competent evidence. As mentioned earlier regarding *197 the absence of a baseline to establish unusual work/exertion, the record is also devoid of any baseline to establish that the stress on the day of the stroke was “unusual,” i.e., more than what Mudd experienced at other times. For this additional reason, the claim should be denied.
Issue 3: Is the heart amendment unconstitutional?
Finally, claimants argue the heart amendment violates the Equal Protection Clause of the United States Constitution. Although this issue was not decided below, the parties agree it was properly preserved and that the rational basis test is the appropriate standard.
As the party asserting a statute’s unconstitutionality, claimants’ burden is a “weighty one.”
Barrett v. U.S.D. No. 259,
“ ‘A statute is presumed constitutional, and all doubts must be resolved in favor of its validity. If there is any reasonable way to construe a statute as constitutionally valid, the court must do so. A statute must clearly violate the constitution before it maybe struck down. [Citations omitted.]. “This court not only has the authority, but also the duty, to construe a statute in such a manner that it is constitutional if the same can be done within the apparent intent of the legislature in passing the statute.” State v. Durrant,244 Kan. 522 , 534,769 P.2d 1174 , cert. denied492 U.S. 923 (1989).’ [Citation omitted.]” Injured Workers of Kansas v. Franklin,262 Kan. 840 , 844,942 P.2d 591 (1997).
Claimants argue the heart amendment violates the Equal Protection Clause because it discriminates between workers. According to claimants, a worker who suffers a heart attack or stroke caused by the exertion of a particular task which that worker regularly performs will be denied any medical or disability compensation, while another worker who suffers an identical heart attack or stroke caused by the same level of exertion performing the exact same task will be awarded full compensation merely because the other worker rarely performed the particular task.
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We affirm that the concept of equal protection of the law is one which “ ‘emphasizes disparity in treatment by a State between classes of individuals whose situations are arguably indistinguishable.’ ”
Barrett,
For a statute to pass constitutional muster under the rational basis standard, it therefore must meet a two-part test: (1) It must implicate legitimate goals, and (2) the means chosen by the legislature must bear a rational relationship to those goals.
Barrett v. U.S.D. 259,
“ ‘[t]he “reasonable basis” test is violated only if the statutory classification rests on grounds wholly irrelevant to the achievement of the State’s legitimate objective. The state legislature is presumed to have acted within its constitutional power even if the statute results in some inequality. Under the reasonable basis test, a statutory discrimination will not be set aside if any state of facts reasonably may be conceived to justify it.’ ” Injured Workers of Kansas,262 Kan. at 847 .
Accordingly, “[a] [party] asserting the unconstitutionality of a statute under the rational basis standard has the burden to negate every conceivable basis which might support the classification.”
Peden v. Kansas Dept. of Revenue,
As we apply the two parts of the rational basis test, we first recognize drat in 1911 the Kansas Legislature abolished the employees’ common-law right to sue employers for injuries and provided the employees with an adequate substitute remedy for the right abolished — the Workers Compensation Act.
To further advance this clear goal the legislature, in enacting the heart amendment, has chosen to distinguish cases of “coronary or coronary artery disease or cerebrovascular injury” from other cases of “personal injury by accident arising out of and in the course of employment.” K.S.A. 44-501(a) and (e). For the last 35 years, compensability has been based on whether the injured worker s exertion which precipitates the disability is more than the exertion of the injured worker’s usual work. In
Nichols
we acknowledged that the legislature had passed the heart amendment because it was concerned that workers compensation awards were allowed where disability or death were merely the result of the natural progress of disease, rather than arising out of employment. Indeed, the legislature created the heart amendment after we noted in
McIver v. State Highway Commission,
Claimants’ challenge to the legislative goal of the heart amendment appears to be based primarily upon our decision in
Stephenson v. Sugar Creek Packing,
The goal of the heart amendment, by contrast, is legitimate. It is not to deny compensation to claimants who suffer injury on the
*200
job, but rather to avoid requiring the employer to act as an absolute insurer of claimants whose death or disability was merely the result of the natural progress of disease and which coincidentally occurred at the workplace. This specific goal was generally affirmed by the legislature’s later addition of subsection “g” to K.S.A. 44-501 to end the compensation tilt in favor of the employee by now requiring impartial application of the Workers Compensation Act to employees and employers alike. While the legislature’s demarcation based on “unusual exertion” is not scientifically exact, the rational basis test does not require such precision.
Injured Workers of Kansas,
While not dispositive of the issue, we are additionally persuaded by tire recognition that one third of other jurisdictions also require unusual exertions. Moreover, several of them have found similar statutes constitutional,
e.g.,
not violative of equal protection under the rational basis test.
DeSchaaf v. Indus. Com’n of Ariz.,
We reverse the Board and affirm the decision of the administrative law judge denying the claim for benefits.
