Tetralogy of Fallot (TF) is a congenital malformation that consists of (1) ventricular septal defect (VSD), (2) obstruction to right ventricular outflow tract (pulmonary stenosis) (PS), (3) right ventricular hypertrophy, and (4) dextroposition of the aorta with septal override. The purpose of this paper was to evaluate and describe the findings from the history, cardiovascular examination and diagnostic tests in one dog diagnosed with TF.
A 17-month-old 9 kg, non - spayed female Border terrier with history of intermittent exercise intolerance and mild cyanosis during strong activity. The dog was taking at that time enalapril (0.25 mg/kg SID PO). The main findings on the clinical examination were subcyanotic membrane mucous and the auscultation revealed a pansystolic murmur degree 3/6, localized at the right side of the thorax over the tricuspid valve area. The X-rays (LL and DV views) revealed enlargement of the right ventricle (VHS: 11.2) with no evidence of pulmonary edema. The ECG showed jagged QRS complexes (leads III, aVL, aVF and V10), enlargement of the left atrium, (PII: 0.26 mV, 44 ms) and the right ventricle (SI, SII, SIII pattern, S wave in lead CV6LL and CV6UL greater than 0.8 mV). Echocardiographically (21.10.2005) presented VSD, dextroposition of the aorta (no more than 50%), infundibular PS with minimal flow, hypertrophy and flattening (D-shape) of the interventricular septum (IVS) and right ventricular hypertrophy (right ventricular wall thickness was same as thickness of IVS). Next control (27.1.2006) showed reduction of diastolic (1.5 vs. 1.02 mm) and systolic (1.63 vs. 1.37 mm) thickness of the IVS and extension of left ventricle posterior wall (diastolic 1.05 vs. 1.28 mm, systolic 1.2 vs. 1.77).
Due to financial reasons owners declined surgical correction and the patient was medicated with atenolol 0.5 mg/kg SID PO. During the following months (12 months), clinical condition of the patient has been stable but the echocardiographical values improved and patient's quality of life is satisfactory up to now.