Vet J. 2026 Oct 8:106915. doi: 10.1016/j.tvjl.2026.106915. Online ahead of print.
ABSTRACT
BACKGROUND: Hyperthyroidism induces a wide spectrum of cardiovascular changes in cats, yet the factors distinguishing subclinical cardiac involvement from congestive heart failure (CHF) remain poorly defined. Previous studies have focused primarily on structural changes, with limited evaluation of atrial function or right-sided involvement.
OBJECTIVES: To compare echocardiographic variables between hyperthyroid cats with subclinical cardiac disease and those presenting in CHF, with emphasis on left atrial remodelling, left atrial function, and left ventricular dimensional changes, and right-sided involvement assessed by right atrial diameter. The comparison of clinical and biochemical variables was a secondary objective.
METHODS: A retrospective case-control study was performed using medical records of 51 hyperthyroid cats with subclinical cardiac disease and 47 hyperthyroid cats presenting in CHF. All cats underwent standard echocardiography, serum biochemistry including total thyroxine (TT4). Type of congestion was determined by thoracic radiography or point-of-care ultrasound, and CHF cats were classified as having pulmonary oedema only or pleural/mixed effusion.
RESULTS: Cats with CHF had significantly larger atrial dimensions and increased left ventricular internal diameter compared with subclinical cats. Left atrial dysfunction was the most robust discriminator between groups. Pleural or mixed effusion was the predominant CHF phenotype and, compared with pulmonary oedema alone, was associated with greater right-sided and global volume overload. TT4 concentrations did not differ significantly between cats with and without CHF. Similarly, biochemical variables showed no significant differences between subclinical or CHF cats or between CHF subtypes.
CONCLUSIONS: Atrial remodelling - particularly impaired atrial function and biatrial enlargement - represents the clearest echocardiographic marker of decompensation in hyperthyroid cats. The predominance of pleural or mixed effusion highlights the importance of assessing right-sided cardiac measurements. Comprehensive echocardiographic evaluation is essential for early identification of cats at risk of CHF, whereas TT4 concentration alone does not predict cardiac status.
PMID:42849777 | DOI:10.1016/j.tvjl.2026.106915