One cat named Tabor appears to be smart, alert, responsive and well hydrated. Visual mucosal color and capillary refill time were normal. Chest auscultation revealed a grade 2/6 systolic heart murmur with the strongest point at the base of the left heart. Respiratory rate is normal. There were no obvious abnormalities on lung auscultation. Heart rate is 160-210 beats per minute. Weight 11 lbs. The rest of the physical examination was within normal limits. ​​​​​​

1. Evaluation of feline hypertrophic cardiomyopathy

The differential diagnosis of Tabor heart murmur includes benign flow-related heart murmurs, cardiomyopathy, and congenital heart disease.

2. Diagnostic plan for feline hypertrophic cardiomyopathy

Blood routine, full set of biochemistry and T4, and chest X-ray.

3. Laboratory examination of feline hypertrophic cardiomyopathy

The blood routine, biochemistry and T4 results were all within the normal range.

4. Chest X-rays of cats with hypertrophic cardiomyopathy

The chest X-ray showed suspicious global heart enlargement, but the pulmonary blood vessels and lung parenchyma images were within normal limits.

　5. Additional testing

Take plasma samples and send them to relevant laboratories to test NTproBNP concentration. A follow-up checkup was scheduled to measure blood pressure before Tabor did any other tests. An echocardiogram was also performed during that review.

5.1 Plasma NTproBNP concentration results

The result is 135 pmol/L. This indicator is elevated, consistent with the results of heart disease examinations. Therefore, Tabor's veterinarian believed that an echocardiogram was necessary to evaluate Tabor's heart disease. Several recent studies have shown that NTproBNP concentrations differ in healthy cat controls, asymptomatic cardiac disease, and congestive heart failure. Therefore, this test can be used clinically as an initial screening test for cats suspected of having heart disease. In addition, this test can help identify whether a cat's dyspnea is respiratory or cardiac in origin.

　5.2 Blood pressure

Tabor’s blood pressure was measured with a Doppler sphygmomanometer, and the result was within the normal range (150mmHg, calculated as the average of 5 measurements in a quiet room).

5.3 Cardiac ultrasound findings

Figure 1-3 shows left ventricular hypertrophy. (This is not a quantitativeThe best window for measurement, but wall thickness measured in short-axis view m-ultrasound is 6.5mm). There was evidence of asymmetric hypertrophy of the interventricular septum; dynamic left ventricular outflow tract obstruction (presence of systolic anterior mitral leaflet motion [SAM]) and associated mitral insufficiency was documented.

Figure 1 Two-dimensional long-axis section shows left ventricular free wall thickening (line) and asymmetric ventricular septal hypertrophy during diastole (arrow)

Figures 2 and 3 show a portion of the mitral valve causing dynamic obstruction of the left ventricular outflow tract.

This obstruction causes turbulence in the left ventricular outflow tract, forming a heart murmur. Displacement of the mitral valve leads to secondary insufficiency and ultimately mitral regurgitation. There was also left atrial enlargement.

Figure 2 Two-dimensional long axis section view shows a captured frame of systolic period

Part of the mitral valve is seen being sucked into the left ventricular outflow tract (arrow). This results in turbulence in the outflow tract. Displacement of the mitral valve can lead to secondary insufficiency. These changes are associated with hearing heart murmurs.

Figure 3 A two-dimensional long-axis section showing a captured frame of systole.

In this image, the color Doppler signal is shown. We see turbulence in the left ventricular outflow tract (characterized by a speckled color pattern). A signal of mitral regurgitation (MR) is also seen, most likely the result of mitral valve displacement.

6. Final diagnosis

This is a classic manifestation of feline obstructive hypertrophic cardiomyopathy (HCOM). A component of obstruction, identified by the presence of forward motion of the anterior mitral valve leaflet during systole, is also common in this disease (occurring in >60% of cases).

Heart murmurs are usually discovered incidentally during physical examination. In this case, elevated NTproNBP concentrations supported the presence of cardiac disease, which was confirmed by subsequent echocardiography.

7. Management recommendations for feline hypertrophic cardiomyopathy

The treatment of cats with asymptomatic cardiomyopathy is controversial, and to date, there is no consensus on management. Currently, there is no evidence to support that treatment delays disease progression or onset of clinical symptoms, or improves prognosis.

Some cardiologists will not recommend treatment, while others may advocate treatment. Due to the presence of dynamic left ventricular outflow tract obstruction, a beta-blocker such as atenolol can be used once or twice daily to achieve a resting heart rate between 160 and 180 beats per minute. Calcium channel blockers may be considered because of significant left ventricular hypertrophy. Angiotensin-converting enzyme (ACE1) inhibitors may be considered because of left atrial enlargement. The cardiologist may prescribe angiotensin-converting enzyme inhibitors and calcium blockers or β-Combination of receptor blockers.

The interval between reexaminations is subjective. If beta-blockers are given, it is reasonable to return the cat for review in 1-2 weeks to assess heart rate and adjust dosage accordingly. Many cardiologists will review the echocardiogram after 6 to 12 months. Chest x-rays are needed when cats have clinical signs of congestive heart failure (eg, rapid breathing, difficulty breathing, coughing, or syncope).

Currently, the value of measuring NTproBNP concentration is still under investigation. More research is needed to determine whether increasing NTproBNP concentrations are associated with disease progression or, alternatively, stable or decreasing NTproBNP concentrations occur in well-managed cases.

Although managing Tabor's heart condition has not been simple, Tabor's owners now realize he has heart disease. They may be instructed to monitor it more closely to watch for signs suggestive of congestive heart failure (eg, increased respiratory rate, dyspnea, cough, exercise intolerance, or lethargy). If clinical signs are detected, Tabor owners will know they should seek veterinary help immediately.