OPINION
¶ 1 After conferring with cardiologist, Dr. Rubin S. Valdez, the St. Luke’s Medical Center emergency room physician, Dr. Paul Johnson, treated Cynthia Diggs’ severe chest pain and released her. Three hours later, she died of a heart attack. Her husband, Vainus Diggs, Sr., her children, and her parents filed a medical malpractice suit against, among others, Dr. Vаldez, Arizona Cardiologists, Ltd., and Arizona Cardiology Group, P.C. (“the Valdez defendants”). The trial court granted summary judgment to the Valdez defendants reasoning that, without an express or implied physician-patient relationship, Dr. Valdez owed no duty of care to Mrs. Diggs.
¶ 2 The issue is whether Dr. Valdez’s brief discussion with Dr. Johnson, during which Dr. Valdez reviewed Mrs. Diggs’ clinical rеcords and rendered advice on the diagnosis and treatment of her medical condition, is sufficient to create a duty from Dr. Valdez to Mrs. Diggs. We hold that when Dr. Valdez undertook to give advice to Dr. Johnson regarding Mrs. Diggs’ care and treatment, knowing that Dr. Johnson would rely on this advice, Dr. Valdez owed a duty of reasonable care tо Mrs. Diggs. We also hold that an express physician-patient relationship is not a requisite for finding a duty of reasonable care under these circumstances. We therefore do not determine whether an express physician-patient relationship existed between Dr. Valdez and Mrs. Diggs. Because summary judgment was inapproрriate, we reverse and remand.
BACKGROUND
¶ 3 On the morning of July 17, 1996, Mrs. Diggs was stricken with severe chest pain. Paramedics took her to the St. Luke’s Medical Center Emergency Department where she was seen by Dr. Johnson. Dr. Johnson took her medical history, examined her, and ordered an electrocardiogram (“EKG”) and an echocardiogram. Although the EKG machine indicated that Mrs. Diggs was suffering from myocardial infarction, Dr. Johnson thought that her physical symptoms were indicative of pericarditis, inflammation of the sac around the heart.
¶ 4 Dr. Johnson had treated pericarditis in the past but before he could be certain that Mrs. Diggs was suffering from pericarditis he had to rule out myocardial infarction as a possible diagnosis. He was, however, untrained in the interpretation of echocardio-grams and thus was unable to use the results of this test to make a differential diagnosis. Furthermore, because the computer interpretation generated by the EKG machine *200 conflicted with Dr. Johnson’s interpretatiоn of the EKG, he needed confirmation from a cardiologist that the EKG demonstrated per-icarditis, rather than myocardial infarction.
¶ 5 Dr. Johnson saw Dr. Valdez visiting another patient in the Emergency Department. Although Dr. Valdez was not the on-call cardiologist at that time, Dr. Johnson and Dr. Valdez briefly discussed Mrs. Diggs’ case. Dr. Johnson presentеd Dr. Valdez with Mrs. Diggs’ clinical history and the results of his physical examination. Dr. Valdez also reviewed the EKG results.
¶ 6 Dr. Valdez agreed with Dr. Johnson that Mrs. Diggs should be discharged. They concluded that Mrs. Diggs’ pericarditis should be treated with Indocin, a nonsteroi-dal anti-inflammatory medication, and that she follow up with her family practice physician immediately. Dr. Valdez also offered to see Mrs. Diggs in ten days for follow-up care.
¶7 Dr. Johnson discharged Mrs. Diggs around 1 p.m. with the above instructions. She died about three hours later of cardiopulmonary arrest. After her death, another cardiologist at St. Luke’s reviewed Mrs. Diggs’ EKG and echocardiogram pursuant to the hospital’s practice tо have a cardiologist review all such tests for an “official” interpretation. The tests confirmed that Mrs. Diggs was suffering from an acute myocardial infarction while she was in the emergency department earlier in the day.
¶ 8 Plaintiffs filed this medical malpractice action against Dr. Johnson, the three corporate entities doing business as St. Luke’s, and the Valdez defendants, requesting damages for wrongful death. The Valdez defendants moved for summary judgment, arguing that Dr. Valdez only informally consulted with Dr. Johnson regarding Mrs. Diggs and owed her no duty of care. Plaintiffs filed a cross-motion for summary judgment on the issue, arguing that Dr. Valdez owed a duty of care to Mrs. Diggs because he: (a) formed а physician-patient relationship with Mrs. Diggs; (b) negligently performed voluntary undertakings according to Restatement (Second) of Torts (1965) (“Restatement”) sections 323, 324, and 324A; and (e) was contractually obligated to treat Mrs. Diggs under St. Luke’s Bylaws.
¶ 9 The trial court found no contractual physician-patient relationship between Dr. Valdez and Mrs. Diggs and rеlying on
Haf-ner v. Beck,
¶ 10 After the court granted summary judgment for the Valdez defendants, plaintiffs settled their claims against the remaining defendants. The court entered an order dismissing the claims against Dr. Johnson and the St. Luke’s entities and entered judgment in favor of the Valdez defendants. Plaintiffs timely filed this appeal оf the summary judgment in favor of the Valdez defendants.
DISCUSSION
¶ 11 Ordinarily, the existence of a duty is a question of law.
See Markowitz v. Arizona Parks Bd.,
¶ 12 We observe that cоurts have reached differing conclusions when considering whether a consulting physician owes a duty of care to the patient. The cases range from a doctor simply answering a colleague’s casual telephone inquiry about a course of treat
*201
ment to an on-call doctor examining and essentially directing the course of the patient’s treatment.
See Oja v. Kin,
¶ 13 But the employment contract rationale is unsatisfactory when, for example, diagnostic medical services are provided by a pathologist. No express physician-patient relationship exists yet many courts have concluded that the physician who provides consulting services to a treating doctor for the benefit of an unknown patient has an “implied” contract of employment that gives rise to a duty.
See, e.g., Dougherty v. Gifford,
¶ 14 In the instant case, we decline to apply this rationale. Although an express contractual physician-patient relationship clearly gives rise to a duty to the patient, the absence of such a relationship does not necessarily exclude a duty to the patient. Nor, in our view, is it necessary for the court to “imply” a contractual relationship between physician and patient in order to find a duty of reasonable care. Rather, we follow our supreme court’s traditional approach to duty and determine whether a sufficient relationship existed between Dr. Valdez and Mrs. Diggs such that, as a matter of policy, Dr. Valdez owed her a duty of reasonable care.
See Markowitz,
¶ 15 Because the trial court relied on
Haf-ner
for the proposition that a contractual physician-patient relationship must exist to establish a duty in a medical malpractice action, we first examine that case. There, а workers’ compensation claimant sued a psychologist who performed an independent medical examination for the insurance carrier.
¶ 16 We conclude that the trial court read
Hafner
too broadly when it relied on the statement that “[a] medical malpractice suit
such as this
will lie only when there was a doctor patient relationship creating a duty to act for the patient’s benefit.”
Id.
at 391,
¶ 17 Duty is, after all, merely “an expression of the sum total of those considerations of policy which lead the law to say that the particular plaintiff is entitled to protection.”
Ontiveros v. Borak,
*202
¶ 18 We find support for our analysis of
Hafner
in
Ornelas,
a case on which the
Hafner
court relied to support its holding.
¶ 19 In examining whether any legal theory exists here that would, in the words of
Ornelas,
“give rise to any legal duty,” we are guided by
Ontiveros.
There, our supreme court extended the duty a tavern keeper owes to his patrons to include the “obligation to help control the conduct of his patron in order to prevent that patron from injuring someone else.”
¶ 20 Returning to the facts in this case, we note that Dr. Valdez was in a unique position to prevent future harm to Mrs. Diggs. Dr. Johnson approached Dr. Valdez, the head of St. Luke’s cardiology department, for assistance in making certain determinations about Cynthia Diggs’ medical care that Dr. Johnson was not fully qualified to make on his own. As between Dr. Johnson and Dr. Valdez, only Dr. Valdez had the expertise to interpret the echocardiogram, rule out myocardial infarction on the basis of the EKG, and admit Cynthia Diggs to the hospital for further treatment. Dr. Valdez, with his superior knowledge and experience, was in the best position to correct any error in Dr. Johnson’s diagnosis.
¶ 21 Furthermore, thе Restatement section 324A, which we previously adopted in
Tollenaar v. Chino Valley School District,
One who undertakes, gratuitously or for consideration, to render services to another which he should recognize as necessary for the protection of a third person or his things, is subject to liability to the third person for physical harm resulting from his failure to exercisе reasonable care to protect his undertaking, if (a) his failure to exercise reasonable care increases the risk of such harm, or ... (c) the harm is suffered because of reliance of the other or third person upon the undertaking. 1
Thus, if an actor’s negligent undertaking “results in increasing the risk of harm to a third person, thе fact that he is acting under a ... gratuitous agreement with another will not prevent his liability to the third person.” Id. at cmt. c. Additionally, “[w]here the reliance of the other, or of the third person, has induced him to forgo other remedies or precautions against such risk, the harm results from the negligence as fully as if the actor had creаted the risk.” Id. at cmt. e.
¶22 Taking the undisputed facts and all inferences therefrom in a light most favorable to Mrs. Diggs, see
Valencia Energy Co. v. Arizona Department of Revenue,
¶23 Dr. Valdez admitted that his advice significantly affected Mrs. Diggs’ treatment. When asked what Dr. Johnson did to rule out myocardial infarction as a diagnosis, Dr. Valdez answered: “He relied on the clinical history. He relied on my curbside consult, and he thought that the clinical history and all the findings most favored pericarditis.” Dr. Valdez later conceded, however, that nothing about the EKG, the clinical history, or the physical examination ruled out myocardial infarction. We can reasonably infer from this testimony that the principal factor that led Dr. Johnson to rule out myocardial infarction was his reliance on Dr. Valdez’s “curbside” opinion that Mrs. Diggs suffered from pericarditis.
¶ 24 Dr. Valdez further testified that if he had considered Mrs. Diggs as his own patient, he would have ordered a cardiac enzyme test to rule out myocardial infarction. Mrs. Diggs was discharged, however, without the benefit of that additional test. Dr. Valdez’s advice and implicit opinion that it was safe to discharge Mrs. Diggs consequently increаsed the risk of harm to her.
¶ 25 Dr. Valdez argues that if we find that he had a duty to Mrs. Diggs under these circumstances, “informal” exchange of information between medical professionals will be chilled. We are not persuaded. We are not dealing with the informal exchange of medical information between two physicians, one of whom merely serves as a resource such as a treatise or textbook. In that case, where the treating physician exercises independent judgment in determining whether to accept or reject such advice, few policy considerations favor imposing a duty on the advising physician.
See Gilinsky v. Indelicato,
¶26 Here, Dr. Johnson was not free tо accept or reject Dr. Valdez’s advice. Dr. Johnson was not a cardiologist; he needed the specialized knowledge of someone such as Dr. Valdez to read the echocardiogram and to confirm his interpretation of Mrs. Diggs’ EKG. Furthermore, because Dr. Johnson did not have admitting privileges, only Dr. Valdez could аdmit Cynthia Diggs to St. Luke’s Medical Center.
¶27 The record and all reasonable inferences indicate that Dr. Johnson did not exercise independent judgment as to Cynthia Diggs’ diagnosis; rather he subordinated his professional judgment to that of the specialist in cardiology, Dr. Valdez. Paraphrasing the Restatement, section 324A, comment e, Dr. Johnson’s reliance on Dr. Valdez induced him to forgo other remedies or precautions against such risk. We conclude from this record that when Dr. Valdez rendered his opinions, he effectively became a provider of medical treatment to Mrs. Diggs. This relationship between Dr. Valdez and Mrs. Diggs gave rise to a duty of reasonable care from Dr. Valdez to Mrs. Diggs.
CONCLUSION
¶ 28 We conclude that even without a contractual relationship, Dr. Valdez owed Mrs. Diggs a duty of due care in rendering medical advice regarding her diagnosis and treatment. We reverse the grant of summary judgment to the Valdez defendants and remand this case for further proceedings consistent with this decision.
Notes
. When section 324A makes a person "subject to liability" for the described conduct, the existence of a duty is assumed.