Evaluation of intrarenal hypoperfusion and renal congestion assessed by intrarenal Doppler ultrasonography in dogs with myxomatous mitral valve disease

Q: What are the key findings of this study?

Combined low renal perfusion and high venous congestion strongly predicted cardiorenal death in dogs with MMVD.

Q: What is the clinical evidence from this study?

Study design: Cohort. Population: Myxomatous mitral valve disease (MMVD) in dogs (n=142). Intervention: Low heart rate-corrected interlobar renal artery velocity time integral (VTIc 0.37) vs. Normal VTIc (≥ 8.3) and normal VII (≤ 0.37). Primary outcome: Composite of cardiac-related death and renal-related death (cardiorenal death) (HR 11.20, 95% CI 3.02-41.48, p=<0.001).

Q: What does this research mean for the field?

Combined low renal perfusion and high renal venous congestion, assessed by intrarenal Doppler ultrasonography, strongly predicts cardiorenal death in dogs with myxomatous mitral valve disease. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To evaluate whether intrarenal arterial velocity time integral and venous impedance index assess renal hypoperfusion and congestion to provide prognostic information in dogs with myxomatous mitral valve disease.

Yuki Iwai; Tomoya Morita; Hiroki Terukina; Masahiro Yamasaki

doi:10.1093/jvimsj/aalag273

November 1, 2026Journal of Veterinary Internal MedicineOpen Access

Evaluation of intrarenal hypoperfusion and renal congestion assessed by intrarenal Doppler ultrasonography in dogs with myxomatous mitral valve disease

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Key result

Combined low renal perfusion and venous congestion linked to ~11.2-fold higher cardiorenal death risk.

HR 11.20
95% CI 3.02-41.48
P<0.001
n=142

Figures

Why the study?

While the predictive value of venous impedance index for evaluating renal congestion in dogs with myxomatous mitral valve disease is reported, an ultrasonographic index of renal perfusion and its prognostic value alongside venous impedance index had not been evaluated.

Does assessment of renal perfusion via corrected interlobar renal artery velocity time integral (VTIc) alone or combined with venous impedance index (VII) predict cardiorenal death in dogs with myxomatous mitral valve disease?

Key Points

To evaluate whether intrarenal arterial velocity time integral and venous impedance index assess renal hypoperfusion and congestion to provide prognostic information in dogs with myxomatous mitral valve disease.
Prospective cohort study of 62 client-owned dogs without heart disease and 80 client-owned dogs with myxomatous mitral valve disease (MMVD) staged by ACVIM guidelines at a single veterinary teaching hospital between November 2019 and November 2024.
Intrarenal Doppler ultrasonography measured interlobar renal artery velocity time integral corrected for heart rate (VTIc) and venous impedance index (VII).
The primary endpoint was cardiorenal death (composite of cardiac-related and renal-related death), evaluated using Kaplan-Meier and multivariable Cox proportional hazards analyses adjusting for MINE score and plasma creatinine concentration.
Interlobar renal artery VTIc decreased with advancing ACVIM stage, from stage B1 (median, 11.75) to stage B2 (median, 8.35; P = .003) and stage C/D (median, 6.91; P < .001 vs stage B1, P = .003 vs stage B2).
Dogs with lower VTIc (< 8.3) had significantly shorter survival times (median, not reached; 95% CI, 98 days-not reached; P < .001) than those with normal VTIc (median, not reached; 95% CI, not reached).
In multivariable Cox analysis, VII remained significantly associated with outcome (HR, 1.24 per 0.1-unit increase; 95% CI, 1.07-1.42), and combining VII with VTIc identified 4 distinct survival subsets.

Study Design

Type

Cohort (n=142)

Blinding

Open-label

Multicenter

No

Structured PICO

Does assessment of renal perfusion via corrected interlobar renal artery velocity time integral (VTIc) alone or combined with venous impedance index (VII) predict cardiorenal death in dogs with myxomatous mitral valve disease?

P

Population

80 client-owned dogs with myxomatous mitral valve disease (mean age 11.4 years, free of advanced CKD or arrhythmias) and 62 healthy control dogs, followed for a median of 476 days.

E

Exposure

Intrarenal Doppler ultrasonography (IRD) measuring heart rate-corrected interlobar renal artery velocity time integral (VTIc, cut-off <8.3) to evaluate intrarenal perfusion, combined with intrarenal venous impedance index (VII, cut-off >0.37) to evaluate renal congestion.

C

Comparator

Normal VTIc (≥8.3) and/or normal VII (≤0.37), established from the 62 control dogs without heart disease, as well as comparisons across 4 combined VTIc and VII subsets.

O

Outcome

Composite of cardiac-related death and renal-related death (cardiorenal death) over a median follow-up period of 476 days (adjudicated by the unblinded investigator).composite

Main Result

Hazard Ratio: 11.2 (95% CI 3.02–41.48)

Absolute Event Rate: 80% vs 10%

p-value: p=<0.001

In dogs with myxomatous mitral valve disease, intrarenal arterial perfusion (VTIc) declines with advancing disease stage, and combining VTIc with venous congestion assessment (VII) on intrarenal Doppler ultrasonography provides exploratory prognostic stratification for cardiorenal death.

Limitations

Outcome assessment was not blinded to intrarenal Doppler ultrasonography findings, creating potential ascertainment bias
Reference interval for VTIc was established from a small cohort of 62 healthy dogs
Small number of primary endpoint events (n=23) and small sample sizes in certain subgroups (e.g., n=4 in subset 2 and n=10 in subset 4), risking model overfitting
Heart rate correction formula for VTIc was adapted from human pediatric medicine and not formally validated in dogs
Glomerular filtration rate was not directly measured
Heterogeneous disease severity and non-standardized medical treatments across the cohort
Systemic hypertension was not excluded
Outcome assessment was not blinded to the IRD findings as the same investigator performed the Doppler measurements and adjudicated outcomes, introducing potential ascertainment bias.
The reference interval for VTIc was established from only 62 dogs without heart disease, which does not meet standard recommendations for establishing reference intervals.
The number of dogs reaching the primary endpoint (n=23) and sample sizes in some subsets (subsets 2 and 4) were small, reducing statistical power and increasing the risk of model overfitting.
The heart rate correction formula used for VTIc was adapted from a human pediatric study and has not been formally validated in dogs with MMVD.
Glomerular filtration rate (e.g., inulin clearance) was not directly measured, and disease severity and medical treatments were heterogeneous and not standardized during follow-up.

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Implication

May aid MMVD prognosis via combined renal metrics; hypothesis-generating for cardiorenal stratification, requiring validation.

Abstract

BACKGROUND: While the predictive value of venous impedance index (VII) for evaluating renal congestion is reported in dogs with myxomatous mitral valve disease (MMVD), an ultrasonographic index of renal perfusion has not been reported. HYPOTHESIS/OBJECTIVES: Low renal perfusion assessed by interlobar renal artery velocity time integral (VTI) is associated with a worse prognosis in dogs with MMVD. Combining VTI and VII provides additional prognostic information. ANIMALS: Sixty-two client-owned dogs without heart disease evaluated for preanesthetic or general health assessment and 80 client-owned dogs with MMVD. METHODS: Prospective cohort study. The VTI was measured by manually tracing the spectral velocity envelope of interlobar arteries. The primary endpoint was defined as the composite of cardiac-related death and renal-related death. RESULTS: The VTI was corrected for the effect of heart rate (VTIc) because VTI and heart rate were negatively correlated in dogs without heart disease. In dogs with MMVD, the VTIc decreased with higher ACVIM stage. Dogs with lower VTIc (< 8.3) had significantly shorter survival times (median, not reached; 95% CI, 98 days-not reached; P < .001) than those with normal VTIc (median, not reached; 95% CI, not reached). In multivariable Cox analysis, VII remained significantly associated with outcome (HR, 1.24 per 0.1-unit increase; 95% CI, 1.07-1.42). Exploratory classification combining VII (<0.37 or ≥0.37) and VTIc (≥8.3 or < 8.3) identified 4 subsets with different survival outcomes. CONCLUSIONS AND CLINICAL IMPORTANCE: The VTIc might be associated with outcome in dogs with MMVD and combined assessment might provide additional exploratory prognostic information.

Discussion

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Cite This Study

Iwai et al. (2026) conducted a cohort in Myxomatous mitral valve disease (MMVD) in dogs (n=142). Low heart rate-corrected interlobar renal artery velocity time integral (VTIc < 8.3) and elevated venous impedance index (VII > 0.37) vs. Normal VTIc (≥ 8.3) and normal VII (≤ 0.37) was evaluated on Composite of cardiac-related death and renal-related death (cardiorenal death) (HR 11.20, 95% CI 3.02-41.48, p=<0.001). Combined low renal perfusion and high venous congestion strongly predicted cardiorenal death in dogs with MMVD.

synapsesocial.com/papers/6af88c530e4d8f4b089c1bf6 https://doi.org/10.1093/jvimsj/aalag273

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Evaluation of intrarenal hypoperfusion and renal congestion assessed by intrarenal Doppler ultrasonography in dogs with myxomatous mitral valve disease

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Evaluation of intrarenal hypoperfusion and renal congestion assessed by intrarenal Doppler ultrasonography in dogs with myxomatous mitral valve disease

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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