Pulsus alternans in English cocker spaniels with dilated cardiomyopathy

To report the clinical findings associated with pulsus alternans in English cocker spaniels with dilated cardiomyopathy and to review the phenomenon of mechanical alternans, usually found in patients with severe left ventricular systolic dysfunction.

The case records of 10 English cocker spaniels with dilated cardiomyopathy and pulsus alternans were reviewed. All dogs had been referred in moderate to severe congestive heart failure. Pulsus alternans was clinically recognised by palpation of a regular alternation of femoral pulse amplitude and confirmed by echocardiography in all cases. Pulsus alternans was an intermittent finding in all 10 dogs.

Phonocardiographic recordings were obtained in three dogs to document variation in the intensity of the heart sounds, with one case exhibiting absence of the second heart sound in alternate beats. M-mode echocardiography performed in all dogs showed alternation of the pattern of mitral valve diastolic motion. Doppler echocardiography showed marked alternation in stroke volume in the aortic outflow in all cases. It also showed alternation in mitral regurgitation and in the velocity of early ventricular filling.

Pulsus alternans may be more prevalent in English cocker spaniels than in other breeds, and because of its intermittent nature, its incidence may be higher than that previously reported. It has diagnostic relevance as it usually indicates severe myocardial depression. Echocardiography allows non-invasive detection of mechanical alternans and provides further insights into its pathophysiology and clinical significance.