Introduction
- Degenerative mitral valve disease (DMVD) is the most common acquired disease in dogs.
- DMVD causes mitral regurgitation, heart enlargement, and can lead to left-sided congestive heart failure (CHF).
- Cause : inherited predisposition in some breeds, ie Cavalier King Charles spaniel, is suspected.
- Signs : left apical systolic murmur.
- Diagnosis : presumptive: detection of the characteristic murmur in an adult small-breed dog: definitive: echocardiograph.
- Treatment : in dogs with CHF, diuretics, ACE-inhibitors, and pimobendan is instituted.
- Prognosis : variably progressive disease, progression often slow.
Diagnosis
Clinical signs
- Heart murmur of mitral regurgitation.
- In early stages of the disease, duration and grade of murmur and extent of radiation roughly correspond with severity of mitral regurgitation. Murmur can be very localized; grade 1/6 and early systolic in very mild lesions and progress to high grade, widely radiating pansystolic harsh, plateau-shaped murmurs in severe disease.
- In late disease, intensity of murmur may decrease due to decrease in left ventricular systolic pressure (reduced contractility) and raised left atrial pressure. These pressure changes reduce the pressure gradient between left atrium and ventricle thereby reducing the velocity of the regurgitant jet.
- Signs of cardiac output are good until late in the disease:
- Good mucous membrane color good with brisk capillary refill.
- Strong synchronous pulse.
- Strong precordial impulse.
- Loud heart sounds.
- Good peripheral perfusion.
Signs of left-sided failure
- Evidence of loss in body condition.
- Sinus arrhythmia abolished and increased heart rate (sinus tachycardia).
- Tachypnea.
- Adventitious respiratory sounds.
- Dysrhythmias
: single or paroxysms of premature beats (supraventricular or occasionally ventricular), atrial fibrillation , especially in large breeds. - Systolic clicks may also be associated with mitral valve prolapse.
Signs of myocardial failure
- Large breed dogs almost always have myocardial failure at the time of onset of CHF.
- Late in the course.
- Heart murmur less loud; softer heart sounds.
- Weak precordial impulse.
- Variable pulse.
Diagnosis
Differential diagnosis
- Other causes of cough :
- Chronic airway disease.
- Chronic bronchitis .
- Tracheal collapse .
- Bronchopneumonia .
- Other causes of CHF, eg DCM or endocarditis .
Sequelae
Prognosis
- Often slowly progressive disease, but may be static indefinitely or for long periods of time. May never progress to the point of causing CHF.
- Prognosis varies with severity of heart failure.
- Short-term prognosis for quality of life without CHF is good.
- Prognosis with CHF that is well controlled is fair (12-24 months).
- Prognosis in large breeds with CHF is poor (>12 months).
Expected response to treatment
- Same as congestive heart failure .
Sources
Publications
Refereed papers
- Recent references from PubMed.
- Boswood A (2008) Effect of pimobendan or benazepril on survival times in dogs with congestive heart failure caused by naturally occurring mitral valve disease: the QUEST study. JVIM 22 , 1124-1135.
- Orton E C, Hackett T B, Mama K & Boon J A (2005) Technique and outcome of mitral valve replacement in dogs. JAVMA 226 (9), 1508-1511 PubMed.
- Griffiths L E, Orton E C & Boon J A (2004) Evaluation of techniques and outcomes of mitral valve repair in dogs. JAVMA 224 (12) 1941-1945 PubMed.
- Olsen L H, Martinussen T and Pedersen H D (2003) Early echcardiographic predictors of myxomatous mitral valve disease in dachshunds. Vet Record 152, 293-297.
- Kvart C et al (2002) Efficacy of enalapril for prevention of congestive heart failure in dogs with myxomatous valve disease and asymptomatic mitral regurgitation. JVIM 16 (1), 80-88.
- Haggstrom J, Kvart C & Hansson K (1995) Heart sounds and murmurs - changes related to severity of chronic valvular disease in the Cavalier King Charles Spaniel. JVIM 9 , 75-85.
- Pedersen H D, Kristensen B O, Lorentzen K A et al (1995) Mitral valve prolapse in 3 year old healthy Cavalier King Charles spaniels. An echocardiographic study. Can J Vet Res 59 , 294-298.
- The COVE Study Group (1995) Controlled clinical evaluation of enalapril in 7 dogs with heart failure - results of the cooperative veterinary enalapril study group. JVIM 9 , 243-252.
- Kittleson M D, Eyster G E, Knowlen G G, Olivier N B & Anderson L K (1984) Myocardial function in small dogs with chronic mitral regurgitiaton and severe congestive heart failure. JAVMA 184 , 455-454.
- Kittleson M D, Eyster G E, Olivier N B & Anderson L K (1983) Oral hydralazine therapy for chronic mitral regurgitation in the dog. JAVMA 182, 1205-1209.
- Boswood A (1999) Rationale for the use of drugs in treatment of cardiovascular disease - positive ionotropes. In Practice5, 253-259.
- Packer M (1998) Neurohormonal interactions and adaptations in congestive heart failure. Circulation 77 , 721-730. (Excellent overview of neurohormonal activation.)
- The IMPROVE Study Group (1995) Acute and short-term hemodynamic, echocardiographic and clinical effects of enalapril maleate in dogs with naturally acquired heart failure - results of the Invasive, Multicenter, PROspective Veterinary evaluation of Enalapril study. JVIM 9 , 234-242. (Trial showing benefit of enalapril therapy in CHF in dogs.)
- Dahlstrom U & Karlsson, E (1995) Captopril and spironolactone therapy for refractory congestive heart failure. Am Journ Cardiol 71 , 29A-33A. (Human clinical trial illustrating aldosterone escape in severe CHF.)
- Pederson H D, Koch J, Poulson K, Jemsen A L & Flagstad A (1995) Activation of the renin-angiotensin system in dogs with mildly asymptomatic mitral valvular insufficiency. JVIM. 9 , 328-331.
- Francis G S & Chu C (1994) Compensatory and maladaptive responses to cardiac dysfunction. Current Opinion in Cardiology 9 , 280-288. (Review of the compensatory but maladaptive consequences of CHF including myocardial remodelling and peripheral vascular changes. Some drug trials also reported, illustrating benefits of ACE inhibitor therapy.)
- Roudebush P, Allen T A, Kuehn N F, Magerkurth J H & Bowers T L (1994) The effect of combined therapy with captopril, furosemide and a sodium-restricted diet on serum electrolyte concentrations and renal function in normal dogs and dogs with congestive heart failure. J Vet Intern Med 8 , 337-342. (Importance of monitoring electrolytes and renal function in patients in CHF.)
- Schlesinger D P & Rubin S I (1994) Potential adverse effects of angiotensin converting enzyme inhibitors in the treatment of congestive heart failure. Comp Cont Educ Pract Vet 16 , 275-283. (Importance of monitoring renal function in CHF.)
- Riegger G A J (1993) ACE inhibitors in early stages of heart failure. Circulation 87 (suppl IV), 117-119. (Suggests in human heart failure that early ACE inhibitor therapy delays progression of pump failure.)
- Zannad F (1993) Angiotensin-converting anzyme inhibitor and spironolactone combination therapy. New objectives in congestive heart failure management. Am Journ Cardiol 71 , 34A-39A. (Aldosterone escape can lead to worsening congestive failure signs in human patients on ACE inhibitor therapy - spironolactone prevents this.)
Other sources of information
- Smith P J, French A et al (2002) Long term efficacy and safety of pimobendan in slight-to-moderate heart failure caused by myxomatous mitral valve disease in dogs. VCS Proceedings, November 2002. Loughborough.
- Lombard C W et al (2000) Clinical experience with pimobendan. VCS Proceedings,Spring meeting. Birmingham.
- Kittleson M & Kienle R (1998) Myxomatous atrioventricular valve degeneration. In: Small Animal Cardiovascular Medicine. 1st edition. Eds: M Kittleson and R Kienle. Mosby, St Louis pp 297-318.
