2017 ACVIM Forum Research Abstract Program

The small number of cases and the large variability in the parameters measured limited our ability to identify differences between groups. Despite the negative findings in this small, retrospective study, further study of the relationship between DOCP administration and CHF seems warranted. The oculocardiac reflex is the heart's physiological response to digital compression of the eyeballs, producing negative chronotropic and inotropic responses in healthy subjects. In this study, we investigated the autonomic imbalance in dogs with CHF due to myxomatous mitral valve disease (MMVD) by means of their individual response to that vagal maneuver. Fifty-two client-owned MMVD dogs (stages B1/B2/C/D) and twelve healthy dogs admitted for regular cardiac evaluation were recruited for a prospective observational study. Every dog had an ECG recorded for 5 minutes, and during the last minute both globes were compressed into the orbits using digital pressure until the 5 minute-recording was over. Twenty RR intervals were used to calculate the mean RR interval, the standard deviation of RR intervals, the root mean square of the successive differences in RR intervals and the vasovagal tonus index before eyeball compression and at approximately twenty seconds after compression started. The percent change of every surrogate was calculated. Although a significant difference was only documented for VVTI (P = 0.0419), the other surrogates did behave differently in stages C and D dogs as compared to B1 and B2 animals ( Figure 1 ). An explanation for this might be the parasympathetic withdraw in CHF, in addition to a subtle sympathetic activation due to discomfort, which was likely suppressed in dogs with preserved vagal response. Also, the sustained increased sympathetic activation rather than transitional sympathetic activation might be involved with the distinct response to OCR in symptomatic dogs as compared to the asymptomatic ones. In people, QT prolongation and instability are known to relate to ventricular arrhythmias. Since dogs with myxomatous mitral valve disease are prone to developing ventricular arrhythmias, this study investigated whether indices derived from QT interval could be used to predict an increased likelihood of arrhythmias regardless of clinical signs. 167 client-owned MMVD dogs (stages B1/B2/C) admitted for cardiac evaluation were recruited for a prospective cross-sectional study. Every dog underwent an echocardiogram and ECG recording. Fifty consecutive QT intervals were measured for each dog. QTs were corrected for heart rate and used to calculate the average QT (QTa), QT variance (QTv), total instability (TI), short term (STI) and long term (LTI) instabilities. A significant difference between asymptomatic and symptomatic animals was documented for every parameter (P < 0.0001),with higher values found for stage C dogs. Significant difference between B1 and B2 also existed for QTa. An AUC >0.5 was found when QTa and STI were used to discriminate dogs with or without ventricular arrhythmias (Figure 1 ). Dogs with QTa >310 (sensitivity:56%/specificity:71%), and STI >11 (sensitivity:56%/ specificity:85%) were shown to be slightly (15%) and moderately (30-45%) more prone to developing ventricular arrhythmias, respectively. Also, an AUC > 0.5 was documented when every QT index was used to distinguish animals with remodeled (B2/C) and non-remodeled hearts (B1). QTa and QTv best discriminated B1 from B2/C dogs and B1/B2 from C dogs, res