Case Studies In Small Animal

Cardiovascular Medicine

Home Up Radiographs ECG 2D Echoes Color Flow Doppler Discharge


Case 37



bulletPresenting complaint: III/VI systolic murmur ausculted by referring DVM.
bulletPE: HR=160. Grade V/VI systolic murmur heard bilaterally but loudest at right basilar region (palpable thrill felt here). Grade I/VI diastolic murmur heard best at the left apex. Femoral pulses strong and synchronous.
bulletThoracic radiographs: The lateral projection suggests left heart enlargement as evidenced by the tall cardiac silhouette. A post-stenotic dilatation is also appreciated in the aortic region on the lateral projection. Pulmonary parenchyma and vasculature are unremarkable.
bulletECG: HR=180. Occasional VPCs originating from the left ventricle. Couplets are present with an instantaneous rate ~300 bpm. ST segment elevation suggestive of regional hypoxia/ischemia for which there was evidence on the echocardiogram.
bulletECHO: IVSd=1.7 cm, LVIDd=2.6 cm, LVPWd=1.1 cm, IVSs=2.0 cm, LVIDs=1.2 cm, LVPWs=1.6 cm, Ao root diameter=1.6 cm, LA dimension=1.9 cm, LA/Aorta=1.2, FS=54%. Velocity across the aortic valve = 4.6 m/s; aortic max PG = 86 mmHg. The primary diagnosis is severe subaortic stenosis (SAS); a turbulent jet begins at the subvalvular region, mild aortic insufficiencyis present and there is severe left ventricular hypertrophy with hyperechoic papillary muscles and subendocardium.There is slight mitral regurgitation. No left atrial enlargement is noted.
bulletConclusion: ECG, thoracic radiographs and the echocardiogram are consistent with severe subaortic stenosis. Physical exam findings (right-sided murmur, strong femoral pulses) are not the most common for SAS but are seen with severe SAS and consistent with the diagnosis. The presence of severe SAS with VPCs indicates increased risk of sudden death. Prognosis is poor given severity of stenosis in 9 week old patient. It is likely that the pressure gradient across the aortic valve will continue to increase until Howie is mature. Balloon valvuloplasty is recommended only as a salvage procedure due to increased risk of mitral regurgitation, worsening left atrial enlargement, congestive heart failure, and sudden death. Atenolol may decrease the risk of a malignant ventricular arrhythmia leading to sudden death. Patient may exhibit clinical signs (syncope, sudden death) within months to a few years. Rx: Atenolol 12.5 mg PO BID. This dose will need to be increased as Howie grows. Recommend recheck at 6 months and 1 year of age unless clinical signs worsen. Prophylactic antibiotics are recommended in bacteremic times in an attempt to decrease Howie's increased risk of aortic vegetative endocarditis.

Discharge Instructions

bulletThank you for bringing Howie to the VMTH. He is such a cutie!
bulletHowie presented to the VMTH on 11/3/04 because your referring veterinarian detected a murmur on physical exam.
bulletOn our physical exam, we detected a grade V/VI systolic murmur which was heard loudest over the right side but was also loud on the left side. We took chest x-rays which showed enlargement of the left side of his heart and a narrowed region below the aortic valve. An ultrasound of his heart showed that he has severe subaortic stenosis (SAS). SAS is a disease where the lumen of the aorta is very small, restricting the blood flow from the left side of the heart into the body, and causing a loud heart murmur. A secondary effect of SAS, which is present in Howie, is leakage from his aorta back into his left heart (called aortic insufficiency, which is mild). He also has mild leakage from his left ventricle into his left atrium (called mitral insufficiency).
bulletWe also did an ECG which showed some irregular beats, which also means his condition is more severe and may be an indication that he is at increased risk of his heart stopping suddenly (sudden death).
bulletSAS is a progressive disease in early life, and we expect the changes in his heart to worsen up until he is around 6 months of age. Possible complications of SAS include collapsing, sudden death, and infection of his aortic valve. There is no surgical treatment for SAS. Medical treatment is aimed at trying to prevent sudden death from an abnormal heart rhythm. Due to his increased risk of aortic valve infection, Howie should receive antibiotics anytime he has the possibility of getting bacteria in his blood stream (e.g., dental procedure)
bulletThe long-term prognosis without treatment is poor and with medical treatment is unknown but hopefully better.
bulletPlease give the following medication: atenolol 12.5 mg (1/2 tablet) by mouth twice daily. This medication is used to decrease the number and severity of abnormal beats and so may help prevent sudden death.
bulletWe would like to see Howie back in 6 months and at 1 year of age to recheck his heart. In the meantime, watch him closely for signs of collapse, exercise intolerance, or any other abnormality; and call us if any of these occur.
bulletThanks again for letting us see Howie.

Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.