Zenalpha Heart Dysfunction

Hello Summarians!

A sedative developed to be easier on the heart still causes measurable cardiac depression in dogs. If you echocardiograph a dog sedated with Zenalpha, the numbers may look like systolic dysfunction. They may not be.

Also this week: serial serum amyloid A measurements in sick foals don't improve diagnosis. And a simple patellar height measurement on X-ray triples the odds of finding a meniscal tear.

Three studies. Two of them change how you read a result.

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Zenalpha Cardiovascular Effects In Dogs

This prospective study evaluated the cardiovascular effects of the sedative combination medetomidine-vatinoxan (Zenalpha; MVZ) in 21 healthy adult dogs undergoing echocardiographic screening. Although MVZ was developed to reduce the cardiovascular depression associated with traditional α2-adrenergic agonists, the investigators found that it still produced clinically important changes in cardiac function. Each dog underwent echocardiography, Doppler blood pressure measurement, and one hour of Holter monitoring before and after intramuscular administration of MVZ, allowing each animal to serve as its own control.  

Sedation with MVZ significantly reduced multiple measures of left ventricular systolic function. Ejection fraction, fractional shortening, stroke volume index, fractional area change, and other indices all declined following sedation. Overall, 71% of dogs had at least two systolic function measurements fall below established reference ranges after receiving the drug. Importantly, chamber size measurements, including the left atrium-to-aortic root ratio and normalized left ventricular end-diastolic diameter, remained unchanged, suggesting that the observed reductions reflected impaired contractility rather than changes in cardiac filling.  

MVZ also produced significant hemodynamic and electrocardiographic effects. Mean systolic blood pressure decreased from approximately 139 mm Hg to 109 mm Hg, while heart rate fell by about one-third. PR and absolute QT intervals became significantly prolonged, and 62% of dogs developed new or worsened atrioventricular conduction abnormalities, primarily first- or second-degree atrioventricular block. However, clinically important ventricular or supraventricular arrhythmias remained uncommon, with only two dogs showing increased ectopic activity and no significant increase in overall arrhythmia burden.  

The authors concluded that although MVZ may have fewer cardiovascular effects than some traditional α2 agonists, it still substantially alters echocardiographic measurements and cardiac physiology. These changes may mimic systolic dysfunction and therefore complicate interpretation of echocardiograms. Clinicians should carefully consider these effects when using MVZ in dogs being screened for heart disease or in patients with known or suspected cardiovascular disorders. 

Forsyth, K. K., Hogan, D. F., Dos Santos, L. F. N., & Weng, H. (2026). Medetomidine-vatinoxan (Zenalpha) results in reduction of systolic function, blood pressure, and heart rate with prolongation of electrocardiographic intervals in healthy dogs. Journal of the American Veterinary Medical Association https://doi.org/10.2460/javma.26.03.0210 

Bottom line — May have fewer issues but still significantly affects heart.

Diagnosis Of Sepsis In Foals

This prospective cohort study evaluated whether serial measurements of serum amyloid A (SAA), an inflammatory biomarker, could improve the diagnosis of sepsis or predict survival in critically ill neonatal foals. Researchers enrolled 127 foals younger than 14 days of age and measured SAA concentrations at hospital admission and again 48 hours later using a point-of-care assay. They compared SAA values with several definitions of sepsis, including positive blood cultures, neutropenia, systemic inflammatory response syndrome (SIRS), and combinations of these criteria, while also examining associations with survival.  

Foals with sepsis generally had higher SAA concentrations at admission than non-septic foals. An admission SAA cutoff of approximately 419 μg/mL provided moderate diagnostic accuracy, with about 80% sensitivity and 81% specificity for identifying foals with neutropenia and positive blood culture combined. Although SAA was significantly associated with blood culture positivity and neutropenia, its ability to accurately confirm or exclude sepsis remained limited. The biomarker performed less well when used to identify SIRS alone, and previously published SAA cutoff values did not perform consistently in this study population.  

Importantly, repeating SAA measurements after 48 hours did not improve the prediction of sepsis or survival. Changes in SAA concentration between admission and day 2 were not associated with blood culture results, neutropenia, SIRS, or death. Likewise, SAA concentrations at either time point were not significantly associated with overall mortality. The authors suggested that physiological increases in SAA during the first days of life, variations in disease progression, antimicrobial treatment, and the limited sensitivity of blood cultures may reduce the usefulness of serial SAA testing in neonatal foals.  

The authors concluded that SAA can serve as a helpful adjunctive screening biomarker when evaluating critically ill neonatal foals, but it should never be used alone to diagnose sepsis or guide antimicrobial therapy. Clinical examination, laboratory findings, and other diagnostic tests remain essential for decision-making. Serial SAA measurements during the first 48 hours of hospitalization provided no meaningful improvement in diagnostic or prognostic accuracy, emphasizing that SAA is best interpreted as one component of a comprehensive clinical assessment rather than a standalone test. 

Eva de Bruijn, Mathilde Laetitia Pas, Donatienne Castelain, Alexander Dufourni, Ellen Paulussen, Bart Pardon, Evaluation of sequential serum amyloid A measurements for the prediction of sepsis and survival in critically ill neonatal foals, Journal of Veterinary Internal Medicine, Volume 40, Issue 4, July-August 2026, aalag155, https://doi.org/10.1093/jvimsj/aalag155 

Bottom line — No meaningful improvement in diagnostic accuracy in the first 48 hours.

Diagnosing Cruciate Tears In Dogs

Cranial cruciate ligament tears (CCLTs) are the most common orthopedic injury in dogs and frequently lead to secondary tears of the medial meniscus, which increase pain, lameness, and the progression of osteoarthritis. Identifying meniscal injury before surgery can improve surgical planning and client communication, but advanced imaging such as MRI and CT is expensive and not always available. This study investigated whether a simple radiographic measurement, the modified Insall-Salvati (IS) index, which assesses patellar height, could help predict the presence of medial meniscal tears in dogs with CCLT.  

The authors retrospectively reviewed 229 stifles from dogs that underwent tibial plateau leveling osteotomy (TPLO) between December 2023 and December 2024. Patellar height was measured on preoperative lateral radiographs using the modified IS index, and the presence of medial meniscal tears was confirmed during surgery by craniomedial mini-arthrotomy. Statistical analyses evaluated whether abnormal IS index values were associated with meniscal injury while accounting for factors such as body size, sex, reproductive status, and whether the cranial cruciate ligament tear was partial or complete.  

Of the 229 stifles, 27% had a medial meniscal tear, while only 12.6% had an abnormal modified IS index. However, 44.8% of dogs with an abnormal IS index had a meniscal tear compared with only 24.5% of dogs with a normal index. After adjusting for potential confounding factors, dogs with an abnormal modified IS index had approximately three times greater odds of having a medial meniscal tear. Although the modified IS index demonstrated high specificity (90.4%), its sensitivity was low (21%), meaning that many dogs with meniscal tears still had normal IS index values.  

The authors concluded that an abnormal modified IS index is a useful, inexpensive radiographic indicator of increased risk for medial meniscal injury in dogs with CCLT. While it should not replace direct surgical assessment or advanced imaging, it may improve preoperative risk assessment, surgical planning, and discussions with owners regarding prognosis. Because the study was retrospective and performed at a single referral center, larger prospective studies are needed to validate these findings and determine the underlying biomechanical relationship between abnormal patellar height and meniscal injury. 

Zayas, J. P., Steurer, J. A., Dixon, B. C., & Newman, R. J. (2026). Abnormal modified Insall-Salvati index values are associated with increased odds of medial meniscal tears in dogs with cranial cruciate ligament tears. Journal of the American Veterinary Medical Association (published online ahead of print 2026). https://doi.org/10.2460/javma.26.03.0166 

Bottom line — Potentially useful tool for a common dog injury.

Just putting things in perspective …