New Study Finds Blood Tests May Rival Ultrasound for Feline Heart Failure Diagnosis

Diagnosis of congestive heart failure by combining echocardiography and blood biomarkers in cats with cardiomyopathy

T. Shimoda, T. Osuga, K. Nakamura

Background
Cardiomyopathy is the most prevalent cardiac disease in cats, with severity ranging from asymptomatic to fatal congestive heart failure (CHF). Echocardiography, particularly the left atrial-to-aortic root ratio (LA/Ao), is a key diagnostic measure, but results can vary by examiner skill. Blood biomarkers such as atrial natriuretic peptide (ANP), cardiac troponin I (cTnI), and N-terminal pro-B-type natriuretic peptide (NTproBNP) are potential adjunct tools. However, their added diagnostic value alongside LA/Ao in feline CHF diagnosis remains unclear.

Methods
This retrospective multicentre study evaluated 26 cats with cardiomyopathy, classified into CHF and non-CHF groups based on radiographic findings and treatment response. Echocardiography measured LA/Ao, and blood samples were analyzed for ANP, cTnI, and NTproBNP. Receiver operating characteristic (ROC) curves assessed the discriminative ability of each marker, both individually and in combination, for differentiating CHF.

Results
LA/Ao was the strongest single predictor of CHF (AUC 0.952), followed by ANP (AUC 0.915), cTnI (AUC 0.861), and NTproBNP (AUC 0.830). Combining NTproBNP or ANP with LA/Ao did not improve accuracy. The combination of LA/Ao and cTnI achieved the highest AUC (0.982), but without significant improvement over LA/Ao alone. Among biomarker-only combinations, ANP and cTnI together provided the highest discriminative ability.

Limitations
The study was limited by small sample size, heterogeneous cardiomyopathy types, potential medication effects on biomarker levels, inability to analyze NTproBNP values >1500 pmol/L, reliance on a single LA/Ao measurement method, and mild disease severity in the non-CHF group.

Conclusions
When accurate echocardiography is available, cardiac biomarkers add little to CHF diagnostic accuracy in cats with cardiomyopathy. However, the ANP and cTnI combination offers diagnostic potential comparable to echocardiography when imaging is not feasible, highlighting its clinical utility in resource-limited or skill-limited settings.

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