From March 2017 to March 2019, we prospectively enrolled all patients with clinically suspected prosthetic paravalvular dysfunction. (e.g., suspected prosthetic heart valve obstruction, endocarditis or paravalvular leak referred to the echocardiography laboratory. A total of eighty patients with suspected prosthetic valve dysfunction were enrolled. Twenty-six patients with prosthetic significant paravalvular leakage were included in the study, whereas fifty-four patients were excluded as mentioned in Figure (1).
- Patients who refused to participate in the study and refused to sign consent.
- The usual contraindications to multidetector CT angiography including pregnancy and contrast allergy.
- Patients whom labs revealed renal impairment. (Renal impairment defined as Estimated GFR < 45 ml/min/1.73 m2, or serum creatinine > 1.3 mg/dl)
- Patients presented with hemodynamic instability or requiring emergency surgery.
- Patients with prosthetic heart valves (PHVs) known to have beam hardening artefacts (containing cobalt-chrome alloy rings e.g., Björk-Shiley and pyrolytic carbon tilting-disk PHVs) that prevent diagnostic assessment.
Study population characteristics
All patients were subjected to the following work up on initial presentation.
Clinical history including age, gender, comorbidities, previous heart valve surgeries, time since last valve surgery , symptoms suggestive of congestive heart failure, symptoms suggestive of infective endocarditis (i.e. fever, sepsis, previous antibiotic treatment before clinical presentation).
Physical examination including blood pressure, heart rate, temperature, auscultations for prosthetic valve sounds (mitral, aortic or both), murmurs of regurgitant lesions across prosthetic or native valves.
Laboratory work up included complete blood count, C reactive protein (CRP), serology for Brucella, Bartonella, Coxiella, Aspergillus, blood culture and sensitivity, kidney function tests including blood urea nitrogen and serum creatinine.
Complete Transthoracic and Transesophageal echocardiography
All echocardiographic studies were conducted with a Philips iE33 ultrasound system and X7-2t transesophageal transducer (Philips Medical Systems, Andover, MA, USA). Standard views for combined TTE and TEE were acquired by experienced non-invasive cardiologists. Cardiac chambers quantification was done according to the American Society of Echocardiography for assessment of cardiac chambers including calculation of left ventricle end diastolic and end systolic volume and diameter, septal and posterior wall thickness, right sided chamber volume and dimensions, aortic and left atrium diameter . Assessment of prosthetic cardiac valves was done according to the American Society of Echocardiography for assessment of prosthetic cardiac valves .
Transesophageal echocardiography was done for better assessment of prosthetic cardiac valves specifically looking for:
- Paravalvular leak: Location, number, size of defect, severity of regurgitant jets depending on criteria for assessment prosthetic cardiac valves in American Society of Echocardiography .
- Other abnormalities of prosthetic cardiac valves including .
- Abscess: defined as irregularly shaped, inhomogeneous paravalvular masses within peri annular region, myocardium, or pericardium
- Pseudo-aneurysm: defined as a space filled with contrast medium with a communication with the cardiac chambers or the aortic root.
- Vegetation: defined as irregularly oscillating masses, adherent to and distinct from the endocardium.
- Fistula: defined as a continuation between the chambers of the left and right heart.
- Prosthesis dehiscence: defined as a rocking motion of a prosthetic valve with an excursion > 15° in any 1 plane.
CT Acquisition and Image reconstruction
All the cardiac computed tomographic angiography studies were done with the Aquilion 64 machine, (Toshiba Medical Systems, Nasu, Japan) which provides a 64- sections for optimal imaging. Our 64-section multidetector CT protocol was based on retrospectively ECG gated CT aortography protocols.
Raw data were reconstructed into 10 equally spaced datasets within the R-R interval of the cardiac cycle and were loaded simultaneously into the dedicated cardiac analysis software (vitreous vital image). The imaging planes were aligned parallel with and perpendicular to the valve leaflets as well as in plane with the valve in three perpendicular imaging planes.
For contrast material– enhanced imaging, we planned the acquisition from 2 cm above the carina (including the ascending aorta) to the bottom of the heart to achieve complete imaging of the heart. When desired, the scanning range was reduced in the craniocaudal direction to reduce radiation exposure.
For anatomic assessment, the best systolic and diastolic reconstruction phases were selected. For dynamic evaluation, cine images in the plane perpendicular to the valve leaflets were recorded after appropriate alignment and windowing.
All CT analyses were performed by 2 experienced radiologists who were blinded to the results of TTE and TEE. CT image quality was assessed and those patients who had bad image quality (presence of severe artifacts and non-diagnostic for appropriate evaluation of the prosthetic valves) were excluded.
The proposed report included several items:
- Type: Mechanical or biological
- Position: Mitral or aortic and/or both.
- Anatomical PHV assessment.
- Paravalvular regurgitation presence and location. We also measured the para-prosthetic anatomical regurgitant orifice area to determine the accuracy and reproducibility of Cardiac CT in assessment of prosthetic paravalvular regurgitation. The size of the PVL was assessed by measuring the perimeter on long-axis views and area on the short-axis view. When CT image quality was suboptimal and not assessable for PVL evaluation, PVL was considered absent for the purpose of data analysis [16,17].
- Other prosthetic valves abnormalities: Vegetations, abscess, Pseudoaneurysm, thrombus.
- Dynamic PHV assessment.
- Normal opening and closing angle: Frame-by-frame analysis of a single cardiac cycle were the basics for defining opening and closing valve angles by CT. For single-leaflet valves, a valve was defined as stuck when motion of one valve leaflet was absent. For bileaflet valves, opening and closing angles were measured between the two leaflets in the fully open and closed positions. Prosthetic valve obstruction was diagnosed when motion of a leaflet or leaflets was persistently restricted, with a calculated opening angle of more (for bileaflet valve) or less (for disk valves) than the values for a normal valve, as specified by the manufacturer .
Twenty-six patients with significant prosthetic PVL underwent cardiac surgery. For patients who underwent redo-surgery, the presence of a PVL orifice was confirmed by inspection on the surgical view. All the patients had intraoperative TEE for identification of prosthetic PVL and other abnormalities of the cardiac valves.
The surgical data that were reported by the surgeon during the open-heart surgery were considered the gold standard for comparing the diagnostic accuracy of transesophageal echocardiography and cardiac computed tomographic angiography.
Surgical data included all the following:
- Paravalvular regurgitation: presence, location, and severity.
- PHV Function: Opening and closure of the prosthetic valve during cardiopulmonary bypass surgery.
- Other abnormalities: Vegetations, abscess, Pseudoaneurysm, thrombus.
Data were coded and entered using the statistical package SPSS (Statistical Package for the Social Science; SPSS Inc, Chicago, IL, USA) version 22. Data were described using the mean, standard deviation in continuous variables and using frequency (count) and relative frequency (percentage) for categorical data. Categorical variables are presented in numbers (percentages).
The agreements on the presence and location of PVL between CT and surgical findings and between TEE and surgical findings were analyzed using Cohen’s kappa statistics. The correlation between the size of prosthetic PVL on CT (area and perimeter) and the severity on TTE or TEE was analyzed using Spearman’s correlation coefficient. Probability values < 0.05 were considered statistically significant. The diagnostic performance of CT and echocardiography for diagnosing prosthetic PVL was assessed using surgical findings as the standard reference.