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    Predicting ION Risk After Cardiac Surgery

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    Ischemic optic neuropathy (ION) is a rare but serious complication of cardiac surgery. Now, building on previous investigations into conditions that predis­pose patients to develop ION, researchers at the University of Illinois at Chicago have developed the first preoperative calculator that clinicians can use to estimate a patient’s risk of perioperative ION.1

    While the model has obvious implications for cardiac surgery, it also has relevance for ophthalmologists, said Steven Roth, MD, whose lab conducted the studies.

    Creating a risk model. For this retrospective case-control study, the researchers considered hospital discharge records of more than 5 million patients in the National Inpatient Sample (NIS) who had undergone cardiac surgery. The researchers looked for procedure codes—including coronary artery bypass grafting, heart valve repair/replacement, and left ventricular assist device insertion—and found 771 cases of ION, for a rate of 1.4 per 10,000 patients.

    ION risk factors used in the model included carotid artery stenosis, cataract, diabetic retinopathy (DR), age-related macular degeneration (AMD), glaucoma, male sex, and prior stroke.

    The findings. Patients were more likely to devel­op ION if they had AMD (OR = 4.45); carotid artery stenosis (OR, 3.17); cataract (OR, 9.78); DR (OR, 5.38); glaucoma (OR, 3.17); peripheral vascular disease (OR, 1.75); and stroke (OR, 2.66). The ORs for male sex and uncomplicated type 2 diabetes were lower (.69 and .55, respectively).

    It’s not clear why several of the highest risk factors were eye diseases, although glaucoma indicates an already compromised optic nerve, and these patients may be more susceptible to injury, Dr. Roth said. He added that “AMD was a surprise.”

    How it works. The risk calculator assigns integer point values for each preexisting comorbidity, which, when added together, generate a risk score for ION. For example, if a male patient has carotid artery steno­sis and glaucoma, but no AMD or DR, his total score is 3, for an estimated .087% risk for ION. If a patient’s score is 7—which would be the case for someone with a history of stroke, AMD, and cataract—ION risk would then rise to 1%.

    Clinical implications. The researchers acknowledged that a risk prediction may not alter the patient’s choice to proceed with surgery. However, it is reasonable to discuss risks and benefits with patients who have scores of 6 or 7, they said. Even a lower score warrants discus­sion if a patient expresses concern.

    And although cardiologists are most likely to use the risk calculator, it could be beneficial for the patient to discuss their risk of developing ION with a specialist, such as a neuro-ophthalmologist, to better understand what’s at stake, Dr. Roth said.

    “ION after cardiac surgery is an underappreciated occurrence,” Dr. Roth said. “While we are not advocat­ing that the surgery be postponed, we are suggesting that the risk calculator [which appears in the published article] be used to provide informed consent to pa­tients at higher risk of ION.”

    —Miriam Karmel

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    1 Shah SH et al. J Cardiothorac Vasc Anesth. Published online Aug. 12, 2022.

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    Relevant financial disclosures: Dr. Roth—NIH: S.

    For full disclosures and the disclosure key, see below.

    Full Financial Disclosures

    Dr. Demirci Aura Bioscience: C; Castle Bioscience: C.

    Dr. Moghimi NEI/NIH: S.

    Dr. Roth NIH: S.

    Dr. Tam None.

    Disclosure Category

    Code

    Description
    Consultant/Advisor C Consultant fee, paid advisory boards, or fees for attending a meeting.
    Employee E Hired to work for compensation or received a W2 from a company.
    Employee, executive role EE Hired to work in an executive role for compensation or received a W2 from a company.
    Owner of company EO Ownership or controlling interest in a company, other than stock.
    Independent contractor I Contracted work, including contracted research.
    Lecture fees/Speakers bureau L Lecture fees or honoraria, travel fees or reimbursements when speaking at the invitation of a commercial company.
    Patents/Royalty P Beneficiary of patents and/or royalties for intellectual property.
    Equity/Stock/Stock options holder, private corporation PS Equity ownership, stock and/or stock options in privately owned firms, excluding mutual funds.
    Grant support S Grant support or other financial support from all sources, including research support from government agencies (e.g., NIH), foundations, device manufacturers, and\or pharmaceutical companies. Research funding should be disclosed by the principal or named investigator even if your institution receives the grant and manages the funds.
    Stock options, public or private corporation SO Stock options in a public or private company.
    Equity/Stock holder, public corporation US Equity ownership or stock in publicly traded firms, excluding mutual funds (listed on the stock exchange).

     

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