Case Studies

These case studies contain detailed information on the diagnostic and treatment process for each individual animal.

Mickey

Case Background

Name: Mickey
Age: 14 years
Sex: Male
Breed: Feline, Domestic Medium Hair
Weight: 6.2 kg
Reason for visit: Murmur evaluation, heard by general veterinarian at wellness appointment.

Clinical History

Please review Mickey’ clinical history.

Attitude/demeanor: Calm, alert
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
Appetite: Normal appetite
Usual diet: Iams® Feline Senior
Vomiting: Rare vomiting, 1-2x monthly
Diarrhea: None noted
Syncope: None observed
Change in urinary habits: None observed
Change in drinking habits: None observed

Physical Exam - General

Please review the results of Mickey’s physical exam.

Body condition: Slightly over-conditioned, BCS 6/9
Attitude: Calm, alert
Mobility | gait: Not assessed
Posture: Normal
Hydration: Normal
Body temperature: 102.1 F
Arterial pulse – rate, regularity, intensity: 176 beats/min, regular, slightly hyperkinetic
Respiratory effort: Effort 32 breaths per minute, normal
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
Lymph nodes: Normal
Oral cavity: Mild gingivitis and plaque
Other abnormalities: Slightly rough, dry hair coat

Physical Exam - Auscultation

Let’s auscult Mickey’s heart & lungs. (Recommend listening with high-end headphones)


How do you interpret Mickey's cardiac auscultation (recorded at the left parasternal border)?
Direct HR: 180 bpm
Heart rhythm: Regular
Intensity of heart sound: Normal, partially obscured by holosystolic heart murmur, grade III/VI
Extra sounds – clicks or gallops: None
Precordial palpation: Normal

Physical Exam - Differential Diagnosis

The following are potential diagnoses for you to consider at this time. Based on the history and the physical examination, please indicate the likelihood of each as:
  • High (could explain most or all of the signs)
  • Possible (less likely to explain most of the signs)
  • Unlikely
Functional murmur
Hypertrophic cardiomyopathy
Degenerative mitral valve disease
Hyperthyroidism
Hypertensive heart disease
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.

Diagnostic Test Selection

BLOOD PRESSURE

Non-invasive blood pressure

CLINICAL LABORATORY

CBC with platelet count
Serum biochemical profile (includes electrolytes)
Urinalysis
Serum thyroxine (T4)
NT-ProBNP
Cardiac troponin-I
Thoracocentesis or abdominocentesis for diagnosis or therapy

Diagnostic imaging (some may require a referral)

Thoracic radiographs
Abdominal radiographs
Echocardiogram doppler studies
Abdominal ultrasound
ECG rhythm strip or 6 lead ECG
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.

Blood Pressure

Systolic blood pressure: 142 mmHg
Diastolic blood pressure: Not available for this case
Mean blood pressure: Not available for this case   Consensus Statements of the American College of Veterinary Internal Medicine (ACVIM) provides the veterinary community with up-to-date information on the pathophysiology, diagnosis, and treatment of clinically important animal diseases. In 2018, ACVIM published updated guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats in the Journal of Veterinary Internal Medicine.

Click here to view and download a PDF of the ACVIM Consensus Statement, guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats.

Radiography

Please review Mickey’s thoracic radiographs.

Click here for Mickey’s radiograph viewer (measure VHS here) View the ventral dorsal radiograph

View the lateral radiograph
What is the vertebral heart size (VHS)?
Is Mickey's heart enlarged?
Is there evidence of congestive heart failure present (pleural effusion or pulmonary edema)?

Clinical Labs

Serum chemistries
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
Heartworm: Not performed
Urinalysis
Urinalysis – USG: 1.018
Urinalysis – protein: Trace
Urinalysis – biochemical: No significant findings
Urinalysis – sediment evaluation: No significant findings
CBC
White blood cells: Not evaluated
Red blood cells: Normal PCV – 34%
Platelets: Not Evaluated
Total T4
Total T4 test results: 2.1 micrograms/dL
NT-proBNP
NT-proBNP test results: 497 pmol/L

Echocardiography

Your technician just returned with the results of Mickey’s echo.

Please view the video and interpretations that follow.
Click here to watch 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.

Referral

The echocardiogram shown in this case study was acquired at the cardiologist, following referral from Mickey’s general veterinarian. The blood work, blood pressure, and thoracic radiographs were all obtained by the general veterinarian prior to referral.

Diagnosis & Treatment

You’re ready to form a diagnosis and treatment plan for Mickey! Please select your answer to each question below.

What is your diagnosis for Mickey?
What treatment(s) would you recommend for Mickey?
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.ACTUAL TREATMENT:
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.

Follow-up Treatment

Follow-up treatment: Follow-up is recommended with Mickey’s general veterinarian in 7-10 days to evaluate the response to the atenolol. In general, the response to atenolol is evaluated by monitoring the cat’s heart rate and blood pressure while receiving the medication as well as an assessment for any clinical signs. An excess of beta-blockade would manifest as a lethargic and less active, or even syncopal, cat. On examination of such a cat on too much atenolol, the heart rate is below 140bpm even during stress and blood pressure may be low. Under-dosing of the atenolol is suspected based on an in-hospital heart rate of >170 bpm. In general, a cat on an optimal dose of atenolol will have no change in clinical history and a heart rate in the hospital (e.g. under stress) of 140 to 160bpm. Doses are adjusted to achieve this finding. Once on a stable and appropriate dose of atenolol, a recheck echocardiogram is advised in 3-4 months and then once to twice yearly thereafter to monitor for progressive cardiac enlargement.

    The CEG is funded through an educational grant from Boehringer Ingelheim Vetmedica, Inc., IDEXX Laboratories, Inc. and Nestle Purina PetCare.

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