412 Heart Murmur, Incidental Finding (asymptomatic) mitral valve regurgitation. Technician Tips Count Respirations and Monitor Respiratory Relevant inclusion criteria for the trial that Teaching owners to keep a log of their pet’s Effort) demonstrated this effect were a vertebral resting respiratory rates can allow early detection heart sum > 10.5, an echocardiographic left of HF decompensation so that medications can SUGGESTED READING atrial–aortic ratio > 1.6, and left ventricular be adjusted and hopefully hospitalization for Atkins C, et al: ACVIM consensus statement. enlargement. acute HF can be avoided. Guidelines for the diagnosis and treatment of • ACE inhibition may have a positive effect on canine chronic valvular heart disease. J Vet Intern the time to development of stage C HF in Client Education Med 23:1142-1150, 2009. canine patients with left atrial enlargement Management of the veterinary patient with AUTHOR: Jonathan A. Abbott, DVM, DACVIM due to mitral valve regurgitation. chronic HF requires careful monitoring and EDITOR: Meg M. Sleeper, VMD, DACVIM • Evidence that medical therapy slows the relatively frequent adjustment of medical progression of HCM is lacking. therapy (see client education sheet: How to Client Education Heart Murmur, Incidental Finding Sheet Initial Database BASIC INFORMATION rate or body posture), short (midsystolic), single (unaccompanied by other abnormal • Thoracic radiographs may be considered Definition sounds), and small (not widely radiating). as the initial diagnostic test in small- to A heart murmur that is detected in the process medium-breed dogs with systolic murmurs of an examination that was not initially directed Etiology and Pathophysiology that are loudest over the mitral valve at the cardiovascular system • A heart murmur is caused by turbulent blood region. flow in the heart (p. 414). • An echocardiogram should be considered Synonym • Identifying the timing, location, and intensity for any adult animal with one or more of Asymptomatic heart murmur of the murmur may be straightforward or the following: uncertain or unusual murmur Epidemiology challenging; uncertainty favors pursuing characteristics, murmur characteristics sug- diagnostic testing. gesting a form of heart disease that requires SPECIES, AGE, SEX • The presence of a heart murmur does not initiation of treatment, large-breed dog (aus- Any species, all ages, both sexes warrant treatment. Rather, determining its cultation and thoracic radiographs have low cause (definitively or presumptively) can lead to specificity for individual cardiac disorders), GENETICS, BREED PREDISPOSITION an assessment of whether treatment is indicated. impending cardiovascular stress (e.g., plane Predispositions mirror those of the causative travel, general anesthesia), breeding prospects, cardiac diseases (pp. 263, 505, 657, 658, 764, DIAGNOSIS or owner who wishes to have confirmation 844, and 948). of the cause of the murmur. Diagnostic Overview • An echocardiogram should be considered RISK FACTORS First, an incidentally detected heart murmur for puppies and kittens with a murmur that • Structural heart disease is pursued through careful characterization is grade 3/6 or louder, that is diastolic or • Anemia of the murmur’s timing, grade, and point of continuous, that obscures the second (or • Youth maximal intensity. Second, these characteristics, both) heart sounds, that radiates to the Clinical Presentation combined with the patient’s signalment, may carotid region or is loudest over the left provide a strong suspicion of a likely underlying apex or right hemithorax, or that is a direct HISTORY, CHIEF COMPLAINT cause. If so and the veterinarian’s tentative diag- relative of an animal with congenital heart • By definition: identified in patients that are nosis is of a benign process, the client is satisfied disease. presented for noncardiovascular concerns, with this opinion without confirmation, and • NT-pro-BNP testing in cats can raise or lower such as annual wellness exams, noncardiac the animal is not to be used for breeding nor the likelihood of structural heart disease medical concerns, or preanesthetic evaluation. subjected to cardiovascular stress, diagnostic (notably cardiomyopathy) as the cause of • Although no historical signs are associated testing is not essential. Otherwise, diagnostic the murmur. with the murmur, misleading or overlapping testing should be pursued. signs are common, including cough, exercise TREATMENT intolerance, and others, which can be caused Differential Diagnosis by unrelated comorbidities. Murmurs may be nonpathologic (the heart is Treatment Overview structurally normal) or pathologic (caused by Because a murmur is a physical finding alone, PHYSICAL EXAM FINDINGS a structural heart lesion): no treatment is warranted. • Heart murmur (by definition), which is • Nonpathologic (benign) murmurs are further described according to timing, grade, and described as functional if a plausible physi- Acute and Chronic Treatment point of maximal intensity (p. 414) ologic cause is detectable (e.g., anemia) or as Initiation of treatment in the absence of a • Auscultatory features of murmurs that are innocent if no cardiac or extracardiac cause diagnosis is not appropriate. It can lead to nonpathologic (see Differential Diagnosis for the murmur can be identified. administration of medications a patient does below) classically meet the six S criteria, which • Pathologic murmurs can be caused by any not need (or that are contraindicated), cause are typically systolic, soft (grade 1-2/6), sensi- cardiac disorder of any degree and do not unnecessary expense, and cause adverse treat- tive (prone to change in intensity with heart automatically indicate a severe condition. ment effects. www.ExpertConsult.com Heart Failure, Chronic 412.e1 ADDITIONAL SUGGESTED RELATED CLIENT EDUCATION READINGS SHEETS Boswood A, et al: Effect of pimobendan in dogs with preclinical myxomatous mitral valve disease Consent to Perform Echocardiography Disorders and cardiomegaly: the EPIC study—a randomized Dilated Cardiomyopathy Diseases and clinical trial. J Vet Intern Med 30(6):1765-1779, Heart Failure 2016. How to Count Respirations and Monitor Chetboul V, et al: Comparative adverse cardiac effects Respiratory Effort of pimobendan and benazepril monotherapy in Mitral/Tricuspid Regurgitation Due to Myxo- dogs with mild degenerative mitral valve disease: matous Heart Valve Disease a prospective, controlled, blinded, and randomized study. J Vet Intern Med 21(4):742-753, 2007. Chetboul V, et al: Effect of benazepril on survival and cardiac events in dogs with asymptomatic mitral valve disease: a retrospective study of 141 cases. J Vet Intern Med 22:905-914, 2008. Ettinger SJ, et al: Effects of enalapril maleate on survival of dogs with naturally acquired heart failure. The Long-Term Investigation of Veterinary Enalapril (LIVE) study group. J Am Vet Med Assoc 213(11):1573-1577, 1998. Häggström J, et al: Effect of pimobendan or bena- zepril hydrochloride on survival times in dogs with congestive heart failure caused by naturally occurring myxomatous mitral valve disease: the QUEST study. J Vet Intern Med 22:1124-1135, 2008. Häggström J, et al: An update on treatment and prognostic indicators in canine myxomatous mitral valve disease. J Small Anim Pract 50(suppl 1):25-33, 2009. Jeunesse E, et al: Effect of spironolactone on diuresis and urine sodium and potassium excretion in healthy dogs. J Vet Cardiol 9(2):63-68, 2007. Keene BW, et al: Management of heart failure in dogs. In Bonagura JD, et al, editors: Kirk’s Current veterinary therapy XIV, St. Louis, 2009, Saunders, pp 769-780. Luis Fuentes V: Management of feline myocardial disease. In Bonagura JD, et al, editors: Kirk’s Current veterinary therapy XIV, St. Louis, 2009, Saunders, pp 809-815. MacDonald KA, et al: Effect of spironolactone on diastolic function and left ventricular mass in Maine coon cats with familial hypertrophic cardiomyopa- thy. J Vet Intern Med 22(2):335-341, 2008. Ouellet M, et al: Effect of pimobendan on echocar- diographic values in dogs with asymptomatic mitral valve disease. J Vet Intern Med 23(2):258-263, 2009. Sisson D, et al: Management of heart failure: principles of treatment, therapeutic strategies, and pharmacology. In Fox PR, et al, editors: Textbook of canine and feline cardiology, ed 2, Philadelphia, 1999, Saunders, pp 216-250. The BENCH (BENazepril in Canine Heart disease) Study Group: Long-term tolerability of benazepril in dogs with congestive heart failure. J Vet Cardiol 6(1):7-13, 2004. www.ExpertConsult.com Heart Murmur, Physiologic 413 Possible Complications PEARLS & CONSIDERATIONS the murmur’s cause (pathologic or nonpatho- Overinterpretation or underinterpretation of logic) without an echocardiogram. incidentally detected heart murmurs can lead Comments to failure to provide an accurate treatment plan • 25%-69% of cats with heart murmurs have SUGGESTED READING and prognosis. no detectable heart disease. Disorders Côté E, et al: Management of incidentally-detected Diseases and • Treatment of a heart murmur is never heart murmurs in dogs and cats. J Am Vet Med Assoc 246:1076, 2015. PROGNOSIS & OUTCOME indicated. The murmur is a clue, and the cause to which the clue is pointing may or AUTHOR: Etienne Côté, DVM, DACVIM Because incidentally detected murmurs occur may not benefit from treatment. EDITOR: Meg M. Sleeper, VMD, DACVIM in animals without associated clinical signs, the prognosis is often fair to good. Many Technician Tips disorders are