however , it is unclear whether to perform reoperation in asymptomatic patients with low transprosthetic gradient . especially , in patients with depressed left ventricular function , it is important to clarify which the main cause of left ventricular dysfunction is structural valve deterioration or other factors such as cardiomyopathy . this case is a 78-year - old male who underwent aortic valve replacement with a 23 mm carpentier - edwards perimount pericardial bioprosthesis ( edwards lifesciences , irvine , ca , usa ) for aortic valve stenosis 7 years ago at another hospital . pulmonary sarcoidosis was diagnosed in his 50s , and cardiac sarcoidosis was diagnosed by a myocardial biopsy at the time of the previous cardiac surgery . he had a past history of thyroid cancer , and his thyroids and parathyroids were resected at the age of 45 , and then after that , he had been prescribed with levothyroxine and alfacalcidol . the echocardiography 6 years after the previous operation showed a normal opening of his prosthesis with an effective orifice area index of 0.62 cm / m , a mean pressure gradient of 15 mmhg , and mildly reduced left ventricular function with an ejection fraction of 43% . although he was asymptomatic , his transthoracic echocardiography 1 year later revealed the restricted motion of the prosthetic valve leaflets , with an effective orifice area index of 0.28 cm / m and a mean pressure gradient of 28 mmhg . it also revealed depressed left ventricular function with an ejection fraction of 37% , moderate mitral insufficiency , and severe tricuspid insufficiency . considering comparably early deterioration of his bioprosthesis valve and left ventricular function , we decided to perform a dobutamine stress echocardiography to differentiate structural valve deterioration from pseudo - aortic stenosis due to cardiac sarcoidosis . at the baseline , the aortic valve peak velocity and the stroke volume index were 3.8 m / s and 31 ml / m . at a dose of 10 g / kg / min of dobutamine infusion , they increased to 4.4 m / s and 41 ml / m , respectively , and the mean pressure gradient across the bioprosthesis increased to 47 mmhg , as the effective orifice area index remained small at 0.29 cm / m . therefore , he was diagnosed as having structural valve deterioration of bioprosthesis at aortic position . he underwent redo aortic valve replacement with a 20 mm ats standard mechanical valve ( ats medical , minneapolis , minnesota , usa ) , mitral annuloplasty with a 26 mm carpentier - edwards physio ii annuloplasty ring ( edwards lifesciences , irvine , ca , usa ) , and tricuspid annuloplasty with a 28 mm edwards mc3 tricuspid annuloplasty ring ( edwards lifesciences , irvine , ca , usa ) . a transthoracic echocardiography at 6 months after the reoperation showed a recovery of left ventricular function with ejection fraction of 49% . pathologic examination of the explanted prosthesis showed calcified deposit and desmoplasia in all the leaflets without an evidence of infiltration of monocyte [ figure 1 ] . we reported a rare case of low transprosthetic gradient structural valve deterioration at aortic position in a patient with cardiac sarcoidosis . the principal manifestations of cardiac sarcoidosis are conduction abnormalities , ventricular arrhythmias , and heart failure . considering early bioprosthetic deterioration in a patient with cardiac sarcoidosis , there were three challenging points to be discussed in this case . first , it was difficult to diagnose which the main cause of depressed left ventricular function was structural valve deterioration or cardiac sarcoidosis . third , the optimal strategy for this case including the type of surgery and prosthesis was worth debating . this case was low - gradient aortic stenosis , which was defined as an aortic valve area < 1.0 cm and a mean transvalvular gradient < 40 mmhg . one of the diagnostic challenges in low - gradient aortic stenosis with depressed left ventricular function is to differentiate true severe aortic stenosis from pseudo - aortic stenosis . in this case , if the cause of depressed left ventricular function was structural valve deterioration , redo aortic valve replacement would be strongly recommended . on the other hand , if his depressed left ventricular function was the clinical manifestation of the cardiac sarcoidosis , the benefit of reoperation on the ventricular reverse remodeling was uncertain . a dobutamine stress echocardiography is useful to differentiate true severe aortic stenosis from pseudo - aortic stenosis in case of native aortic valve . it remains unclear whether it is also useful in case of bioprosthetic valve deterioration , but it could lead us to the diagnosis of true structural valve deterioration . only 7 years had passed until the reoperation for structural valve deterioration in this case . reported several risk factors of early bioprosthetic deterioration , but this case did not have any of these factors . skolnick et al . reported the association between osteoporosis and decreased progression of aortic stenosis , and speculated inhibition of valvular calcification might be due to alterations in levels of vitamin d and parathyroid hormone . on the other hand , it is reported chronic secondary hyperparathyroidism in renal failure is associated with aortic calcification . in patients with sarcoidosis , therefore , the possible cause of early bioprosthesis deterioration in this case might be alfacalcidol , an analog of vitamin d or parathyroid hormone - related protein due to sarcoidosis . the patient was asymptomatic , but it was reasonable to perform reoperation because the structural valve deterioration caused the left ventricular dysfunction . in this case , we decided to perform surgical aortic valve replacement with mechanical valve considering his early bioprosthetic valve deterioration and the possibility of the need for another redo aortic valve replacement . however , it might be another option to perform surgical aortic valve replacement with bioprosthetic valve and transcatheter valve - in - valve procedure if necessary in the future . future studies are warranted to determine what strategies about the optimal type of surgery and valve selection are reasonable .