Focus on Cardiology

NEW INDICATION FOR PIMOBENDAN ESTABLISHED

Pimobendan is an inodilator with known survival benefit following onset of congestive heart failure (CHF). Until this study, pimobendan use in Doberman pinschers in the preclinical asymptomatic (occult) phase of dilated cardiomyopathy (DCM) had not been investigated.

• Client-owned Dobermans (N = 76) with occult DCM (echocardiographic evidence of increased left ventricular internal dimension in systole but no clinical signs) were randomly administered pimobendan or a placebo.
• The median time to onset of CHF or sudden death was significantly longer in the pimobendan group (718 days) compared to the placebo group (441 days); the median overall survival time was also significantly longer in the pimobendan group (623 days vs 466 days).
• It was concluded that the administration of pimobendan to Dobermans with occult DCM prolongs onset of clinical signs, improves survival, and can improve outcome overall.

The use of pimobendan specifically in Dobermans is now recommended following echocardiographic diagnosis of occult DCM. However, its use has not yet been investigated in other breeds, Dobermans with ventricular arrhythmias but no echocardiographic changes, or animals with other forms of cardiomyopathy.

Summerfield NJ, Boswood A, O’Grady MR, et al. Efficacy of pimobendan in the prevention of congestive heart failure or sudden death in Doberman pinschers with preclinical dilated cardiomyopathy (the PROTECT study). J Vet Intern Med 2012; available online, DOI: 10.1111/j.1939-1676.2012.01026.x.

PREDICTION OF HEART FAILURE & MORTALITY

Radiographic image of a dilated left atrium caused by chronic mitral valve degeneration. Arrows: Trachea

Degenerative mitral valve disease is very common, representing approximately 75% of clinical cases of acquired heart disease in dogs. This disease typically has a long preclinical phase and in many dogs, is benign and does not progress to CHF. However, these factors make prognosis difficult.

• This study investigated clinical characteristics that could be assessed during the preclinical phase to help predict which dogs would have progressive disease.
• Median follow-up period was 833 days (range, 1–1977).
• Presence of left atrial enlargement was the only predictor of cardiac-related death; increased echocardiographic mitral inflow velocities (E wave velocity > 1.2 m/s) and presence of cough predicted progressive disease.

These findings suggest that dogs with no evidence of left atrial enlargement, no history of coughing, and normal estimates of left atrial pressure are unlikely to experience CHF or cardiac-related death in the next 2 to 3 years. However, if dogs exhibiting these characteristics develop clinical signs of CHF, disease progression monitoring and treatment should be initiated.

Borgarelli M, Crosara S, Lamb K, et al. Survival characteristics and prognostic variables of dogs with preclinical chronic degenerative mitral valve disease attributable to myxomatous degeneration.
J Vet Intern Med 2012; 26:69-75.

DIAGNOSIS OF CARDIOVASCULAR DISEASE IN CATS

Early detection of feline occult hypertrophic cardiomyopathy (HCM) poses a diagnostic challenge, especially in primary care facilities. Standard clinical signs of heart disease, such as exercise intolerance, anorexia, weight loss, dyspnea, tachycardia, and presence of a murmur, are not reliable diagnostic criteria.

• Three groups of cats (N = 151) were prospectively examined: Those with normal hearts (n = 48), heart disease without CHF (n = 52), and CHF (n = 51).
• There was a high incidence of heart murmurs in the normal cats in this study (42%), but incidence of a murmur was significantly higher in cats with heart disease (86%) or CHF (64%).
• The presence of a gallop rhythm or another arrhythmia was a much better way to differentiate between the groups.
• The echocardiographic left atrial (LA) diameter obtained using basic echocardiographic imaging indicated that a LA diameter greater than 16.5 mm had 87% specificity for CHF.

This study provides information about clinical signs and echocardiographic measurements of LA diameter that can assist primary care clinicians in detecting feline occult HCM.

Smith S, Dukes-McEwan J. Clinical signs and left atrial size in cats with cardiovascular disease in general practice. J Small Anim Pract 2012; 53(1):27-33.

SUCCESSFUL MITRAL VALVE REPAIR REPORTED

Mitral valve repairs (MVR) consist of cardiopulmonary bypass, annuloplasty (decreases circumference of mitral annulus), and chordae tendineae repair/replacement. Previous attempts of surgical MVRs in dogs with mitral valve disease (MVD) have been largely unsuccessful until this report.

• Results of 48 surgical MVRs performed in small-breed dogs in Tokyo, Japan were reported.
• Surgical technique included:
  • Suturing expanded polytetrafluoroethylene strips (ePTFE) to the valve annulus
  • Reducing the size of the valve annulus to that of the aortic sinus of Valsalva.
  • Suturing artificial ePTFE chordae tendineae to the mitral valve
  • Excising papillary muscles and ruptured chordae.
• Of the 48 dogs, 45 were discharged within 12 days. Discharged dogs survived at least 5 months, with 12 surviving greater than 3 years.
• One month post surgery, clinical signs resolved, appetite improved, and radiographic vertebral heart size was reduced in patients.
• At 38 months, survival was 93.3% compared to medical management, which generally has an average survival of less than 1 year.

These successful MVRs were performed by a highly trained surgical team. As more teams become trained in cardiopulmonary bypass and its surgical techniques, MVR could become increasingly available, prolonging survival in dogs with MVD.

Uechi M, Mizukoshi T, Mizuno T. Mitral valve repair under cardiopulmonary bypass in small breed dogs: 48 cases (2006-2009). JAVMA 2012; 240(10):1194-1201.