Heart Sounds and Murmurs: Changes Related to Severity of Chronic Valvular Disease in the Cavalier King Charles Spaniel

Abstract

Auscultatory, phonocardiographic (PCG), radiographic, and echocardiographic evidence of chronic valvular disease (CVD) were studied in 79 Cavalier King Charles Spaniels with a mean age of 7.6 years (SD 2.6). Cardiac murmurs were present in 59 of the dogs and the intensity of the systolic cardiac murmur, assessed by auscultation (grade 1–6), was correlated (P < .001). The heart sounds and duration of electromechanical systole (Q‐S2) were investigated in all dogs using measurements obtained from PCG recordings. Normal regression equations describing the relation between heart rate and systolic intervals (Q‐S1, Q‐S2 and S1‐S2) were established based on observations in 11 normal control Cavalier King Charles Spaniels. The total electromechanical systole (Q‐S2), Q‐S1, and S1‐S2 intervals in the 59 dogs were related to the corresponding normal regression equation. A shortening of Q‐S2 and S1‐S2 intervals were found in dogs belonging to heart failure class I (Q‐S2; P < .01 and S1 ‐S2; P < .05), class II, and classes III and IV (both P < .001). The ratio of the amplitudes of the first (S1) and second heart sounds (S2) measured on the PCG recordings was found to be increased in dogs belonging to class I (P < .01), class II, and classes III and IV (both P < .001, R2= .63). The presence of a third heart sound (S3) was detected, using PCG, in 21 of the 68 dogs. The proportion of dogs exhibiting S3 increased with heart failure class (and increasing cardiac dimensions) (P < .01) were found in these dogs. None of these dogs showed an S3 in heart failure class I, but 7 of the 13 dogs developed an S3 in class II. © 1995 American College of Veterinary Internal Medicine