Introduction

The objective of this study was to calculate the shock index (SI) in dogs with myxomatous mitral valve disease (MMVD) and to evaluate its utility to predict presence of congestive heart failure (CHF).

Methods

Medical records of dogs presenting for further evaluation of cough, respiratory distress or murmur evaluation to a small animal teaching hospital between 1st January 2020 and 31st December 2020 with diagnosed MMVD were retrospectively analysed. Dogs were included if they had a documented heart rate (HR), systolic blood pressure (SBP) and audible left apical systolic murmur at presentation. Disease severity was categorised based on current ACVIM consensus guidelines by a board-certified cardiologist following echocardiogram. Healthy control dogs were also included. Heart rate and SBP were used to calculate SI for all dogs and compared. Diagnostic performance of SI, HR and SBP were compared with receiver operating characteristics (ROC) curves.

Results

Sixty-nine dogs with MMVD and 12 control dogs were included. Median (range) HR and SI for MMVD dogs were 120 bpm (72–250 bpm) and 0.8 (0.52–2.29); for control dogs 94 bpm (73–137 bpm) and 0.69 (0.55–0.94), respectively (p<0.001 and p=0.016). Mean SBP (±standard deviation) for MMVD dogs and control dogs was 149 mm Hg (±20.6 mm Hg) and 140 mm Hg (±13.7 mm Hg), respectively (p=0.17). The number of dogs in each stage of MMVD were 27 B1, 26 B2, 15 C, 1 D. Shock index and HR for MMVD stage C and D dogs were higher compared to stage B1, B2 and control dogs (p<0.001); no other significant differences were identified. Shock index (area under curve [AUC] 0.98 [95% confidence interval {CI} 0.96–1.0]) and HR (AUC 0.96 [95%CI 0.92–1.0]) were excellent indicators for the presence of CHF. To predict CHF presence, an optimal SI cut-off value=1.0 had 93% sensitivity and 95% specificity and an optimal HR cut-off=147 bpm had 87% sensitivity and 91% specificity. Systolic blood pressure had fair ability to predict the presence of CHF (AUC 0.72 [95% CI 0.6–0.84], optimal cut-off=138 mm Hg 71% sensitivity, 69% specificity).

Conclusions

Shock index values greater than 1.0 may suggest presence of CHF in dogs with MMVD when there are compatible clinical signs.

Disclosures

No disclosures to report.