Extracellular vesicular microRNAs as potential biomarker for early detection of doxorubicin-induced cardiotoxicity.

BACKGROUND: Long-term use of doxorubicin (DOX) is limited by cumulative dose-dependent cardiotoxicity. OBJECTIVES: Identify plasma extracellular vesicle (EV)-associated microRNAs (miRNAs) as a biomarker for cardiotoxicity in dogs by correlating changes with cardiac troponin I (cTnI) concentrations and, echocardiographic and histologic findings. ANIMALS: Prospective study of 9 client-owned dogs diagnosed with sarcoma and receiving DOX single-agent chemotherapy (total of 5 DOX treatments). Dogs with clinically relevant metastatic disease, preexisting heart disease, or breeds predisposed to cardiomyopathy were excluded. METHODS: Serum concentration of cTnI was monitored before each treatment and 1 month after the treatment completion. Echocardiography was performed before treatments 1, 3, 5, and 1 month after completion. The EV-miRNA was isolated and sequenced before treatments 1 and 3, and 1 month after completion. RESULTS: Linear mixed model analysis for repeated measurements was used to evaluate the effect of DOX. The miR-107 (P = .03) and miR-146a (P = .02) were significantly downregulated whereas miR-502 (P = .02) was upregulated. Changes in miR-502 were significant before administration of the third chemotherapeutic dose. When stratifying miRNA expression for change in left ventricular ejection fraction, upregulation of miR-181d was noted (P = .01). Serum concentration of cTnI changed significantly but only 1 month after treatment completion, and concentrations correlated with left ventricular ejection fraction and left ventricular internal dimension in diastole. CONCLUSION AND CLINICAL SIGNIFICANCE: Downregulation of miR-502 was detected before significant changes in cTnI concentrations or echocardiographic parameters. Further validation using a larger sample size will be required.

Clinical findings and survival time in dogs with advanced heart failure.

BACKGROUND: Dogs with advanced heart failure are a clinical challenge for veterinarians but there are no studies reporting clinical features and outcome of this population. HYPOTHESIS/OBJECTIVES: To describe clinical findings and outcome of dogs with advanced heart failure caused by degenerative mitral valve disease (DMVD). ANIMALS: Fifty-four dogs with advanced heart failure because of DMVD. METHODS: For study purposes, advanced heart failure was defined as recurrence of congestive heart failure signs despite receiving the initially prescribed dose of pimobendan, angiotensin-converting-enzyme inhibitor (ACEI), and furosemide >4 mg/kg/day. Data were collected for the time of diagnosis of Stage C heart failure and time of diagnosis of advanced heart failure. Date of death was recorded. RESULTS: At the diagnosis of advanced heart failure, doses of pimobendan (n = 30), furosemide (n = 28), ACEI (n = 13), and spironolactone (n = 4) were increased, with ≥1 new medications added in most dogs. After initial diagnosis of advanced heart failure, 38 (70%) dogs had additional medications adjustments (median = 2 [range, 0-27]), with the final total medication number ranging from 2-10 (median = 5). Median survival time after diagnosis of advanced heart failure was 281 days (range, 3-885 days). Dogs receiving a furosemide dose >6.70 mg/kg/day had significantly longer median survival times (402 days [range, 3-885 days] versus 129 days [range 9-853 days]; P = .017). CONCLUSIONS AND CLINICAL IMPORTANCE: Dogs with advanced heart failure can have relatively long survival times. Higher furosemide dose and non-hospitalization were associated with longer survival.