Background: Radioactive iodine (I-131) is an effective treatment option for hyperthyroid cats yielding a mean survival time (MST) of approximately 3 years. Prior to treatment, cats may be screened for comorbidities such as renal disease, hypertension, and/or occult cardiomyopathy. Cats with hyperthyroidism may develop secondary cardiac disease and NT-proBNP and vertebral heart score (VHS) measurements may be increased due to either primary cardiac disease or secondary to uncontrolled hyperthyroidism. Hypothesis/
Objectives: An elevated NT-proBNP and increased VHS prior to I-131 treatment is associated with a reduced survival time when compared to patients with normal NT-proBNP and VHS prior to treatment. Animals: 594 hyperthyroid cats from a tertiary referral practice population.
Methods: Retrospective record review from cats treated with I-131 between 2019 to 2023. Data recorded included patient signalment, pre-treatment thyroid levels, NT-proBNP, VHS, and survival time.
Results: Hyperthyroid patients with VHS and NT-proBNP within the reference range had a MST of 1317 days versus 926 for patients with an increased NT-proBNP and VHS. Patients with elevated NT-proBNP values and VHS at baseline have a hazard ratio of 1.99 (P-value < .0001) in comparison to patients with values in normal reference range. Elevated NT-proBNP before treatment have a hazard ratio of 1.07 for every 100pmol/L over normal values. Conclusions and Clinical Importance: Pre-treatment NT-proBNP and VHS is a prognostic indicator for patients who undergo I-131 treatment. This could indicate the need for further monitoring and investigation of causes for elevated NT-proBNP and VHS prior to treatment with I-131.
