The Role of 4DCT in the Evaluation of Patients with Bio-Prosthetic Valve Thrombosis

Valvular heart disease affects >100 million patients worldwide out of which 200,000 cases of aortic valve replacements are performed annually and the numbers are predicted to rise further due to the aging population and a subsequent increase in degenerative valve disease. Based on an analysis of the Society of Thoracic Surgeons National Database; between 1997 and 2006, Bioprosthetic tissue valve replacement gained prominence causing a massive shift from mechanical to bioprosthetic valve replacements. The use of mechanical valves decreased to 20.5%, whereas the use of bioprosthetic valves increased to 78.4% [1, 2] The transition from mechanical to bioprosthetic valve was partially attributed to the fact that, younger individuals refuse long-term anticoagulation and elderly patients are at a higher bleeding risk [1].

Historically, it was regarded that chronic anti-coagulation and monitoring could be deferred in patients receiving bioprosthetic tissue valves. However, recent data shows bioprosthetic tissue valves could also develop thrombosis, particularly since the utilization of 4D CT angiography (4DCT) in practice. Most cases of valve thrombosis were diagnosed at a median of 6 months post-procedure, with patients presenting with Heart-Failure like symptoms i.e.; progressive dyspnea with exertion, low left ventricular ejection fractions, orthopnea, paroxysmal nocturnal dyspnea, and patients demonstrating an increased requirement of diuretics [3-6] Figure 1. Other likely predictors of valve thrombosis include paroxysmal atrial fibrillation, sub-therapeutic INR in patient who were anticoagulated with vitamin K antagonists, increased body mass index and lack of anti-coagulation [1,7]. Valve thrombosis may be associated with smaller valves <23 mm or valve in valve procedures [3,4].

Echocardiographic findings of significant increase in transvalvular gradient [5] in addition to leaflet thickening and abnormal cusp mobility serves as independent predictors of valve thrombosis. 4DCT, with its superior spatial resolution, is superior to echocardiography in analyzing surgical aortic valve replacement (SAVR)/Trans-catheter Aortic Valve Replacement (TAVR) leaflets’ morphology and excursion [3-6,7,8,9] (Figure 2A&2B).

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The latest generation CT scanners with their superior temporal and spatial resolution are now being increasingly utilized to further analyze valve replacements in an accurate manner. They are also able to identify degenerative disease of the bioprosthetic valve replacements by picking up leaflet calcification as well. 4DCT was thus is considered not only superior in terms of its imaging capabilities but it’s also considered a sensitive marker for early calcification suggestive of bioprosthesic stenosis in the making and hence has a lower threshold for identifying such cases [3,4,7,10- 13]. In our clinical practice we treat symptomatic patients with Warfarin when indicated and follow up and monitor them with echocardiography and 4DCT. Patients who receive prompt anticoagulation and monitoring are often resolved of further symptoms and see better outcomes.

4DCT with its advanced temporal and spatial imaging capability is an imaging modality that has helped shape clinical practice in patients with bioprosthetic valve thrombosis and is effective in clinical decision making for anti-coagulation therapy [3,4,7,10- 13]. An increased awareness of symptoms and echocardiographic parameters is necessary when managing such patients. We look forward to more studies in the future that will put light on this topic [14-18].

None.

No conflict of interest.

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