Researchers evaluated the records of 187 total dogs that had been diagnoses with myxomatous mitral valve disease (MMVD.) Of those 94 dogs were Cavalier King Charles spaniels (CKCS) .

Results showed that worsening of MMVD was the predominant determinant of pulmonary hypertension. Pulmonary hypertension was also associated with greater likelihood of chronic heart failure and death. Cavalier King Charles spaniels were more likely to experience cardiac death than other breeds.

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The prevalence of pulmonary hypertension in Cavalier King Charles spaniels compared with other breeds with myxomatous mitral valve disease.