Novel imaging strategies for the detection of prosthetic heart valve obstruction and endocarditis

Abstract

Prosthetic heart valve (PHV) dysfunction remains difficult to recognise correctly by two-dimensional (2D) transthoracic and transoesophageal echocardiography (TTE/TEE). ECG-triggered multidetector-row computed tomography (MDCT), 18-fluorine-fluorodesoxyglucose positron emission tomography including low-dose CT (FDG-PET) and three-dimensional transoesophageal echocardiography (3D-TEE) may have additional value. This paper reviews the role of these novel imaging tools in the field of PHV obstruction and endocarditis.For acquired PHV obstruction, MDCT is of additional value in mechanical PHVs to differentiate pannus from thrombus as well as to dynamically study leaflet motion and opening/closing angles. For biological PHV obstruction, additional imaging is not beneficial as it does not change patient management. When performed on top of 2D-TTE/TEE, MDCT has additional value for the detection of both vegetations and pseudoaneurysms/abscesses in PHV endocarditis. FDG-PET has no complementary value for the detection of vegetations; however, it appears more sensitive in the early detection of pseudoaneurysms/abscesses. Furthermore, FDG-PET enables the detection of metastatic and primary extra-cardiac infections. Evidence for the additional value of 3D-TEE is scarce.As clinical implications are major, clinicians should have a low threshold to perform additional MDCT in acquired mechanical PHV obstruction. For suspected PHV endocarditis, both FDG-PET and MDCT have complementary value.

Radionuclide Imaging of Infective Endocarditis: State of Art and Future Perspective

“…Conversely to NVE, which is usually limited to the presence of a vegetation, PVE infection generally spread along the sewing ring and leads to peri-annular extension (pseudo-aneurysms, abscess) [16]. In a recent prospective study concerning 72 patients, Saby et al showed that adding abnormal 18 F-FDG uptake around a PV to the modified Duke criteria at admission increased the sensitivity for definite PVE from 70 to 97% (Table 2) [17••].…”

“…The best strategy to reduce false positive finding is correct patient preparation and selection. We want to underline, once more, how important is the optimal suppression of physiologic myocardial glucose utilization with (1) high fat, low carbohydrate diet for at least two meals with a fast of at least 4 h prior imaging [24, 30•]; (2) possible use of intravenous unfractionated heparin (50 IU/kg) approximately 15 min prior to 18 F-FDG injection [16,31]. In addition, we also recommend to withdraw of metformin which is associated with intense and diffuse [ 18 F]FDG uptake in the small and large bowels [32•]; (3) discontinuation/reduction to the lowest possible dose the use of steroid in the 24 h preceding the exam [32•]; (4) avoid the inclusion of patients <3 months of PV implantation [5].…”

Echocardiographic evaluation of heart valve prosthetic dysfunction

“…Therefore, this diameter is not the diameter of the opening area of an artificial valve, which is usually smaller. Dysfunction of the valve prosthesis is a specific pathology that requires a special knowledge regarding the functioning of prosthetic valves, methods of their examination and the causes of prosthetic function disorders (6). Thrombosis is the main cause of prosthetic heart valve dysfunction.…”

“…TTE examination in these patients reveals an elevated pressure gradient on the prosthesis and a reduced effective orifice area, and occluding clots should be detected using transesophageal examination (18). Prosthetic mitral insufficiency (regurgitation) is often difficult to diagnose during a transthoracic echocardiography because the ultrasound beams pass through a prosthetic metal structures and discs giving intensive artifacts.…”

FDG PET/CT in prosthetic heart valve endocarditis: There is no need to wait

“…1,2 Echocardiography is often the first imaging modality used to diagnose PVE, but has difficulty establishing the disease in as many as 30% of cases due to acoustic shadowing. 3,4 It is no wonder that other imaging techniques have garnered increasing interest in the setting of this disease, 5 with publications on 18 Ffluorodeoxyglucose (FDG) positron emission tomography with CT attenuation correction (PET/CT) in the setting of endocarditis steadily increasing in recent years: from none before the year 1995 to 46 in the year 2016 alone.…”