The self-insured employer appeals from the compensation judge’s determination that the employee suffered a personal injury on May 24, 2001, that was permanent and causally related to her work as a police officer.  We affirm.

Christine A. Hamren Rine, the employee, worked as a patrol officer for the City of Minnetonka, the self-insured employer, from 1987 to 2002.^[1]  A May 26, 1987, pre-employment physical indicated the employee had a normal exercise EKG and was suitable for work as a police officer with no restrictions.  The compensation judge found the employee had no physical problems performing her patrol officer duties prior to May 24, 2001.
On May 24, 2001, the employee was assisting a state patrol officer with a traffic stop in the back parking lot of the police department.  The driver took off running and the employee and the trooper chased him on foot for about 75 yards.  The trooper tackled the driver, and the employee helped subdue and handcuff the driver and put him in the back seat of the patrol car.  The employee testified she was winded and out of breath.  Afterwards, as the officers stood next to the car talking, the employee felt a kind of thumping or kicking sensation in her chest and noticed feeling weak, light-headed and shaky.  The employee sat in her squad car and tried to write a report but was unable to focus.  After about half an hour, the employee checked her pulse and it was very fast.  She went inside, talked to her supervisor, then went to the hospital to get checked out.

The employee was seen in the emergency room at Methodist Hospital about an hour after the incident.  The cardiac monitor registered a heart rate of 136 with atrial fibrillation flutter and an irregular pulse that converted to an atrial fibrillation rhythm.  The employee was given metoprolol to control the heart rate and admitted to the hospital.  The heart failed to return to a regular rhythm with medication, and the employee underwent electrical cardioversion the next morning which returned the heart to normal sinus rhythm.  The employee returned to work as a patrol officer the following day without restrictions.

On June 25, 2001, the employee was examined by Dr. Thomas Davis, a cardiologist at Park Nicollet Heart Center.  The doctor diagnosed one episode of atrial fibrillation and prescribed Atenol, as needed, to reduce the heart rate if it sped up.  In a letter report dated July 9, 2001, Dr. Davis noted the employee had no history of cardiac problems prior to May 24, 2001.^[2]  The doctor’s diagnosis was one episode of “atrial fibrillation - - an irregularly irregular fast heart rhythm.”  The doctor stated the employee’s baseline EKG and cardiac exam were normal and that her heart was probably structurally normal.  Dr. Davis opined the stress of the employee’s work that day precipitated the episode of atrial fibrillation and that this was an electrical problem related to “extreme stress.” (Ex. A, Ex. 1.)

On September 19, 2001, the employee was in training, working on self-defense tactics that involved running, kicking and punching.  The employee testified she experienced symptoms similar to those she experienced on May 24: a rapid heart beat and racing pulse, a fluttery feeling in the chest, and feeling light-headed and weak.  She stated she spoke to her supervisor who took her pulse and it was very fast.  The employee discontinued training and an ambulance was called.  The employee was not in atrial fibrillation when the ambulance arrived about half an hour later.  The employee then went home for the day.

In follow-up visits with Dr. Davis, on September 24 and 28, 2001, the employee expressed concerns about returning to work, stating she did not feel she would be able to defend herself or others if, in a stressful situation, her heart rate sped  up and she went into atrial fibrillation.  Dr. Davis’s assessment was one documented episode of atrial fibrillation, with recurrent episodes of faster heart beating inappropriate to the amount of exercise.  On September 28th, Dr. Davis provided a note stating the employee “had very fast/irregular heart beats under periods of extreme stress.  She should avoid stress at work.”  (Ex. A.)  The employee was unable to continue working as a patrol officer, and the employer had no long term light-duty positions available.  The employee’s last day with the employer was January 5, 2002.

In disability reports completed on October 18, 2001, January 20, 2003, and August 31, 2004, Dr. Davis diagnosed paroxysmal atrial fibrillation and subjective symptoms of fast irregular heart beating or fast heart rate triggered by stress.  The doctor opined the employee was disabled from returning to work as a police officer, and that her disability was the direct result of an injury or illness that arose out of an act of duty as a police officer.  Dr. Davis indicated that her disability had been ongoing since 2001 and would last her lifetime.

On July 28, 2003, Dr. David Berman, a cardiologist, reviewed the employee’s medical records at the request of the self-insured employer.  The doctor described the May 24, 2001 event, indicating the activity was not particularly strenuous.  He diagnosed a lone atrial fibrillation with a single episode in May 2001 successfully treated with cardioversion.  Dr. Berman agreed the stress involved with chasing and subduing the suspect on May 24, 2001, precipitated the episode of paroxysmal atrial fibrillation, and also agreed that atrial fibrillation is sometimes related to stress as well as abuse of alcohol.  However, the doctor opined the employee does not have a cardiac disability as a result of the May 24, 2001, atrial fibrillation and that the episode on September 19, 2001, was not cardiac and was not directly related to her employment.  Dr. Berman maintained the employee was not disabled from a cardiac standpoint and needed no restrictions on activity, stating lone atrial fibrillation occurs in a normal heart, has a good prognosis, and generally does not require treatment unless the episodes recur frequently.

The employee sought payment of medical expenses, a rehabilitation consultation, and temporary total disability benefits from January 5, 2002 through January 5, 2004.  The self-insured employer denied primary liability, asserting the employee’s atrial fibrillation was not causally related to her work or, in the alternative, that it was a temporary aggravation that had resolved.^[3]  Following a hearing, a compensation judge found the employee sustained a work-related injury in the nature of atrial fibrillation on May 24, 2001; that the employee experienced a second episode of rapid heart beating on September 19, 2001, and her symptoms on that date were related to the previously diagnosed atrial fibrillation condition; and that the employee’s work injury and restrictions precluding her return to work as a police officer were permanent.  The self-insured employer appeals.

The self-insured employer argues the opinion and conclusions of Dr. Davis, relied upon by the compensation judge, lack adequate foundation, and that substantial evidence does not support the compensation judge’s findings on causation.  We are not persuaded.

 The appellant first argues the facts assumed by Dr. Davis are not consistent with the evidence, and that the compensation judge improperly relied upon his opinions in finding causation.  We disagree.

Dr. Davis, the employer asserts, gives the impression the employee went into atrial fibrillation while chasing and subduing the suspect, when, in fact, the employee did not go into atrial fibrillation until well after the event.  Dr. Davis’s examination notes and July 9, 2001, letter describe the May 24, 2001, episode in very general terms, and it is clear he was aware the employee did not get to the hospital until at least an hour after the chase.  Some lack of clarity regarding the onset of an employee’s symptoms or a doctor’s failure to comment upon all details in a medical history may go to the persuasiveness or weight accorded a medical opinion, but do not render the opinion without foundation.  Drews v. Kohl’s, 55 W.C.D 33, 39 (W.C.C.A. 1996).

The employer further contends the employee’s activities on May 24, 2001, were not particularly strenuous and do not demonstrate “extreme stress.”  At the hearing, the employee testified the event on May 24, 2001, was very strenuous.  She stated that chasing and subduing a suspect was very physically trying, explaining,“you get a lot of adrenaline when you start running, you have to be able to chase them down, keep up with them, when you’re already out of breath and physically taxed, you need to have the strength left to subdue them and get them handcuffed.”  (T. 15.)  The compensation judge found the employee’s testimony credible, further noting the employer’s expert, Dr. Berman, agreed the stress involved in chasing and subduing the suspect precipitated the episode of atrial fibrillation on May 24, 2001.  Assessment of a witness’s credibility is the unique function of the trier of fact.  Tolzmann v. McCombs-Knutson Assocs., 447 N.W.2d 196, 42 W.C.D. 421 (Minn. 1989).  In this case, the compensation judge’s acceptance of the employee’s testimony was not unreasonable or manifestly contrary to the evidence.^[4]

The appellant additionally contends the only reason Dr. Davis restricted the employee from returning to work as a patrol officer was the employee’s fear she might have another episode of atrial fibrillation while performing patrol work some time in the future.  The employer argues Dr. Davis’s causation opinion is mere speculation and is not based on objective medical evidence.  It is not uncommon for a patient to discuss concerns related to a medical condition or injury with their doctor.  Here, in three separate disability reports in October 2001, January 2003, and August 2004, Dr. Davis diagnosed atrial fibrillation and fast and/or irregular heart beating precipitated by stress, opining the employee was disabled and that her condition rendered her unfit to perform the duties of a peace officer.  In his 2003 report, Dr. Davis specifically stated the employee had been disabled since 2001, and that the disability would last her “lifetime.”  (Ex. B.)  Dr. Davis is a cardiologist and has treated the employee since shortly after the May 24, 2001, episode.  The compensation judge could properly rely on his opinion.  See, e.g., Drews at 39; Lundberg v. Bemidji Ambulance Serv., slip op. (W.C.C.A. May 22, 1998).

The appellant also contends that a physical injury, as claimed by the employee, must manifest itself by objective medical evidence of tangible damage.  Specifically, the employer maintains, to establish a permanent injury, the employee had to demonstrate some structural abnormality in her heart.  Thus, the employer argues, because there is no dispute the employee’s atrial fibrillation did not result in any structural damage to her heart, Dr. Davis’s opinion lacks foundation and is legally erroneous.  We disagree.  Unlike Sweet by Sweet v. Tremendous! Entm’t, Inc., 65 W.C.D.113 (W.C.C.A. 2004) and Sether v. Wherley Motors, slip op. (W.C.C.A. July 27, 2005), cited by the employer, the precipitating cause of the employee’s atrial fibrillation was not underlying damage to the heart resulting from coronary artery disease, but, in the opinion of Dr. Davis, an electrical disorder triggered by out-of-the ordinary stress.  An cardiac electrical disorder is as real as coronary artery disease, and, based on the evidence in this particular case, is sufficient to provide a basis for a finding of a permanent work injury.

Finally, the employer argues the compensation judge’s finding that the employee sustained a permanent, work-related injury is not supported by substantial evidence in the record.  There is no dispute the employee experienced an episode of atrial fibrillation on May 24, 2001, nor that the employee experienced rapid heartbeat on September 19, 2001.  The employer points out, however, there was no confirmation of any atrial fibrillation on September 19, and the employee has not had a documented episode of atrial fibrillation since May 2001.  Since the employee had only one episode of atrial fibrillation which has not recurred in five years, the appellant argues, the only logical finding is that she sustained a temporary injury.  Moreover, the employer asserts, in this case the employee never had a pre-existing heart condition, thus there could not be any “aggravation” in this case, temporary or permanent.

The employee testified she did not have problems with shortness of breath, chest pains, arrythmia or anything like that prior to the May 24, 2001, episode, and that her symptoms on May 24 and September 19, 2001, were completely different from anything she had ever experienced.  There is no dispute the employee had no previous restrictions or limitations on her activities.  After these incidents, however, the employee was, in Dr. Davis’s opinion, physically unfit to perform the duties of a police officer as a result of atrial fibrillation and/or fast heart beating triggered by stress.  The employee’s permanent and ongoing “treatment” in this case, specifically noted by Dr. Davis in his disability reports, is removal from the stressful work of a patrol officer.

The compensation judge found, in an unappealed finding that the employee had no physical difficulties performing her work duties for the employer prior to May 24, 2001 (finding 2).  A compensation judge is permitted to use the fact that a condition did not preexist or was not symptomatic prior to a work injury to support a finding of causation.  Gustafson v. Mr. Carrot, Inc., slip op. (W.C.C.A. Nov. 28, 1994) (citing Laurent v. Sterling, slip op. (W.C.C.A. Mar. 9, 1994)); see, e.g., Simons v. Ridgeview Med. Ctr., slip op. (W.C.C.A. Dec. 1, 2006); Lundberg (slip op. May 22, 1998).  Additionally, as noted previously, Dr. Davis opined the employee’s condition was permanent and was the direct result of an injury or illness that arose out of the employee’s police officer duties.

A compensation judge’s findings must be affirmed “if, in the context of the record as a whole, they are supported by evidence that a reasonable mind might accept as adequate.”  This court must give due weight to the opportunity of the compensation judge to judge credibility, and “where the evidence is conflicting or more than one inference may reasonably be drawn from the evidence, the findings of the compensation judge are to be upheld.”  Redgate v. Sroga's Standard Serv., 421 N.W.2d 729, 40 W.C.D. 948 (Minn. 1988) (citing Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235 (Minn. 1984)).  Moreover, absent a clear foundational defect in the expert opinion relied upon, this court must affirm a compensation judge’s choice between conflicting medical opinions.  See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D.364 (Minn.1985). Whether we might have viewed the evidence differently is not the point, rather, the question is whether the findings of the compensation judge are supported by evidence that a reasonable mind might accept as adequate.  Redgate, id.  We conclude the findings of the compensation judge have adequate evidentiary support and, accordingly, affirm.