Introduction: Left ventricular hypertrophy (LVH) in young patients may be due to several distinct diseases and the accurate diagnosis is needed for the appropri-ate treatment.

Methods: A 22 year-old man with a history of hyper-trophic cardiomyopathy and chronic treatment with diltiazem was admitted for severe progressive dyspnea and low grade fever. Physical examination revealed low blood pressure (85/50 mm Hg), tachycardia, systo-lic and diastolic murmurs in the aortic area and signs of congestive heart failure. There were left ventricular hypertrophy on the ECG and cardiomegaly with veno-us congestion on the chest X-Ray. The blood tests show-ed moderate anemia, increased WBC (14900/mm3, 80% neutrophils), and increased level of inflammatory markers. Transthoracic echocardiography revealed ec-centric left ventricular hypertrophy with severe systolic dysfunction (EF 30%) and infective endocarditis with vegetation on the markedly calcified tricuspid aortic valve with subsequent severe aortic regurgitation. Co-lor and conventional Doppler assessment identified se-vere LVOT obstruction (Gmax ≥50 mmHg), the shape of the Doppler envelope suggesting fixed obstruction, proximal to aortic valve. The careful transesophageal scrutiny of the LVOT morphology showed the presen-ce of an obstructive subaortic fibromuscular ridge wi-thout additional congenital heart disease. The “jet lesi-ons” makes the aortic valve susceptible to infective en-docarditis, which in this particular case was with group D streptococcus. Acute severe aortic regurgitation due to infective endocarditis, complicated with acute heart failure has a strong indication for urgent surgery. The patient underwent aortic valve replacement and LVOT reconstruction associated with a six weeks course of antibiotics. The postoperative recovery was uneventful with resumption of left ventricular function and good long-term outcome.

Results: The fibromuscular ridge is a rare, anatomic va-riant of the congenital subvalvular aortic stenosis, whi-ch also can encompass a thin discrete membrane (the most common form) or a diffuse fibromuscular tunnel-like narrowing of the LVOT. Associated left ventricular hypertrophy, particularly basal septal hypertrophy, can be taken for hypertrophic cardiomyopathy, and can also contribute to the LVOT obstruction. The particularity of this case was the presence of jet lesions, secondary to subaortic stenosis, that led to ac-celerated aortic valve remodeling, severe calcifications and increased risk for subacute infective endocarditis in a young patient.

Conclusions: The presented case emphasizes the im-portant role of comprehensive echocardiography for the diagnosis of congenital subaortic stenosis, the con-sequences on the left ventricle and the associated com-plications leading to the right therapeutic decisions.