|Breed||Feline, Domestic Medium Hair|
|Reason for Visit||Murmur evaluation, heard by general veterinarian at wellness appointment.|
Please review Mickey's clinical history.
|Coughing||No cough reported|
|Respirations||Eupneic, 32 breaths per minute|
|Exercise Tolerance||No change reported|
|Sleep Patterns||Sleeping well, most of the day|
|Weight Change (loss or gain)||No change in weight|
|Usual Diet||Iams® Feline Senior|
|Vomiting||Rare vomiting, 1-2x monthly|
|Change in urinary habits||None observed|
|Change in drinking habits||None observed|
Please review the results of Mickey's physical exam.
|Body Condition||Slightly over-conditioned, BCS 6/9|
|Mobility | Gait||Not assessed|
|Body Temperature||102.1 F|
|Arterial pulse - rate, regularity, intensity||176 beats/min, regular, slightly hyperkinetic|
|Respiratory Effort||32 breaths per minute, normal effort|
|Mucous Membranes - Color & CRT||Pink|
|Jugular Venous Pulse & Pressure||Slight distension, no pulsation|
|Abdominal Palpatation||Both kidneys have irregular contours on palpation; the rest of the abdominal palpation is non-tender and normal|
|Oral Cavity||Mild gingivitis and plaque|
|Other abnormalities||Slightly rough, dry hair coat|
Let's auscult Mickey's heart & lungs.
Direct HR: 180 bpm
Heart Rhythm: Regular
Intensity of Sounds: Normal, partially obscured by holosystolic heart murmur, grade III/VI
Extra Sounds - Clicks or Gallops: None
Precordial Palpation: Normal
The CEG considers the following differential diagnosis as most likely (and why):
In cats, systolic murmurs commonly arise from structural pathology (e.g. cardiomyopathy, with HCM being the most common) or from functional causes. The term "functional murmur" implies that the heart is structurally normal; these murmurs are seen most often with changes in hemodynamics related to stress/excitement or from alterations in blood viscosity (e.g. anemia). Cats also develop cardiac changes secondary to systemic disease and these may manifest as a heart murmur - systemic hypertension (hypertensive heart disease) and hyperthyroidism (thyrotoxic heart disease) are two common examples. As this cat is 14 years old, it is important to rule out hyperthyroidism even though the clinical picture and history do not fit a classic example of a hyperthyroid cat. It is also important to rule out systemic hypertension in this cat as renal disease is very common in the older cat, which is associated with high blood pressure and may cause secondary cardiac changes that result in a heart murmur. Myxomatous mitral valve disease (degeneration), as occurs in dogs, does not cause significant cardiac disease in the cat and is unlikely to manifest as a grade III/VI heart murmur.
The CEG considers the following diagnostic tests as the highest priority:
There are a few ways to proceed with a case such as this. It is first appropriate to evaluate this cat with a thorough physical examination for any underlying disease and then screen for common causes of functional murmurs; as such, a thyroid level and non-invasive assessment of systemic blood pressure are indicated. Given the age of the cat, routine blood tests for systemic disease such as a CBC, biochemical profile, and urinalysis are reasonable, but unlikely to provide a diagnosis to explain the heart murmur. If all the above are normal, determination of the cause of the murmur would require an echocardiogram. Thoracic radiographs or an electrocardiogram could be performed; however, neither are sensitive for a diagnosis of heart disease and if apparently normal do not rule out cardiomyopathy or other heart conditions. An NT-proBNP test would be reasonable to determine the likelihood that significant heart disease is present. If this test comes back <100 pmol/L, it is unlikely that clinically significant heart disease is present and this may provide useful information to the client debating referral for an echocardiogram. However, it would also be reasonable to forego the NT-proBNP and have an echocardiogram performed to obtain a definitive diagnosis. Indeed, if the NT-proBNP comes back elevated or in a gray zone, an echocardiogram is still the recommended test to determine the cause of this cat's heart murmur.
Please review Mickey's thoracic radiographs.
|BUN||34 mg/dL, Normal: 5 - 20 mg/dL|
|Creatinine||2.2 mg/dL, Normal: 0.9 - 2.1 mg/dL|
|Sodium||144 mEq/L, Normal:146 - 156 mEq/L|
|Potassium||3.8 mEq/L, Normal: 3.2 - 5.5 mEq/L|
|Chloride||118 mEq/L, Normal: 114 - 126 mEq/L|
|ALT||52 IU/L, Normal: 20 - 95 IU/L|
|ALP||80 IU/L, Normal: 15 - 65 IU/L|
|Heartworm Test Results||Not performed|
|Urinalysis - USG||1.018|
|Urinalysis - Protein||Trace|
|Urinalysis - Biochemical||No significant findings|
|Urinalysis - Sediment Evaluation||No significant findings|
|White Blood Cells||Not evaluated|
|Red Blood Cells||Normal PCV - 34%|
|Total T4 Test Results||2.1 micrograms/dL|
|NT-proBNP Test Results||497 pmol/L|
Your technician just returned with the results of Mickey's echo.
|Subjective - lesions of valves, myocardium, pericardial space||There is no pericardial effusion. The mitral valve is being pulled toward the interventricular septum during systole, which is apparent on the slowed long-axis images and supported by the turbulent flow noted on color Doppler in the left ventricular outflow tract.|
|LV chamber size and thickness||The left venticular walls show symmetrical concentric hypertrophy, measuring thicker than normal. Normal cats have walls that measure 3 to 5 mm in end-diastole with any measurement over 6 mm consistent with hypertrophy. Mickey's left ventricular freewall and septum measure from 6.5 to 8.5 mm in thickness. In addition, his papillary muscles, seen best in the short-axis images, are severely hypertrophied.|
|Left atrial size||Left atrial size appears mildly dilated, but measurements are required to confirm enlargement. His left atrium did measure slightly larger than normal at 17 mm at end-systole (normal cats have a left atrium that typically measures 11 to 16 mm in diameter).|
|LVIDd & LVIDs||Left ventricular internal dimensions appear normal to slightly reduced as a consequence of the concentric hypertrophy.|
|LV shortening fraction||Mickey’s fractional shortening is normal to hyperdynamic. Most cats have a fractional shortening of 35 to 55%; Mickey’s measured 57% likely related to the thick walls compromising his systolic dimension.|
|RA, RV and Pulmonary Artery||Images of the right heart are not fully shown, but were normal in this cat.|
|Effusions||There are no effusions apparent.|
|Doppler results||Color Doppler shows turbulence in the left ventricular outflow tract beginning at the site of mitral-septal contact. This is a consequence of altered left ventricular, papillary, and mitral valve geometry resulting in SAM – systolic anterior motion of the mitral valve.|
You're ready to form a diagnosis and treatment plan for Mickey! Please select your answer to each question below.
THE CEG RECOMMENDS:
Mickey has asymptomatic HCM. There are few studies evaluating therapy at this stage of heart disease in cats. In the absence of heart failure, diuretics (furosemide) are not indicated. The use of enalapril in asymptomatic HOCM cats is poorly defined. If the cat is in heart failure, ACE-inhibition is recommended to blunt the up-regulation of the renin-angiotensin-aldosterone system. In the cat with a normally-sized left atrium or slightly enlarged left atrium as in this case, most cardiologists would not initiate enalapril therapy. Additionally, ACE-inhibitors result in vasodilation; obstruction in a cat with HOCM may worsen in response to vasodilation and is therefore typically not recommended. Atenolol is typically recommended in the setting of HOCM by most cardiologists, although there is no scientific evidence in support of this therapy. Either atenolol or no therapy (particularly if the cat is very challenging to medicate) would be reasonable therapeutic recommendations at this time.
|Initial Therapy||Atenolol was initiated at 6.25 mg orally twice daily; selected for ease of dosing as a ¼ of a 25 mg tablet. A compounded liquid suspension could also have been chosen.|
|Diet||No change required at this time; there is no evidence for dietary intervention at this stage of heart disease.|
|Lifestyle Adjustments||None recommended at this time.|