Prosthetic valve thrombosis: When prevention is better than treatment
To the Editor:
We have recently read with great interest the study reported by Özkan et al,1 included in the 2015 second issue of your Journal. In this work, they accurately demonstrate how an ultraslow (25 hours) infusion of low-dose (25 mg) plasminogen activator represents a safer thrombolytic treatment in patients with prosthetic valve thrombosis (PVT), showing moderately low nonfa-tal complications and mornonfa-tality.
Prosthetic valve thrombosis is a rare but life-threatening process originating from the formation of a fibrous cloth, which can evolve to a definitive obstructing thrombus. The literature usually identified an obstructive and nonobstructive PVT type according with Doppler echocardiographic measurements. The obstructive form is the less frequent, including approximately 0.3% to 1.3% of patient-year and often requiring prosthesis replacement. On the contrary, the nonobstructive PVT represents a more common type, with a reported incidence as high as 10% in some transesophageal echocardiography (TEE) studies.2
As previously showed from the same group,3 TEE provides a useful guide to assess imaging of the thrombus, including the size, mobility, and location. In this way, it can help clinicians in treatment decisions, allowing to differentiate thrombi from pannus formation or strands. We have already shown that multidetector computed tomography can be used for the accurate imaging of thrombi on prosthetic aortic valves.4
Nevertheless, these techniques usually simply confirm an advanced PVT form, typically when critical symptoms have already appeared. Mortality and fatal complications, although reduced in recent years, can occur as a consequence of the subsequent treatment, which include reoperation or recently developed thrombolytic proto-cols (as previously described). Therefore, an early detection of thrombotic formations appears decisive for patient's prognosis.
For this purpose, we focused in an in vitro and in vivo ultrasound phonocardiographic analysis of the closing sound produced by several mechanical heart valves (MHVs),5,6 to assess an early detection of thrombotic apposition and consequent MHV dysfunc-tion.7Examining different simulated MHV thrombotic formations in a Sheffield pulse duplicator, we ac-quired closing sound in a specific frequency range related to power spectra, analyzing them with an artificial neural network (ANN).8 This allowed to classify the presence of thrombotic formations of different weight and shape, with an improvement in the efficiency related to the extension of the analysis to the ultrasound region.
Several studies have dealt with this topic in the recent years. An in vivo study based on a hand-held device (Thrombocheck) evaluated MHV closing sound on the time domain (furthermore deriving a frequency domain analysis), being able to recognize a large number of MHV failure, later confirmed on cinefluoroscopy.9Some other in vitro studies tested commercially available MHV closure sounds at different hemodynamic conditions, demonstrating that each particular valve has a typical “fingerprint” in spectral signal of frequencies produced by the closure of the valve at different conditions.9This concept brought to the application of ANNs to analyze power spectra of different types of valve. In addition, this method showed to be able to distinguish functional and dysfunctional prosthesis, differentiating obstructive from nonobstructive forms and identifying precocious apposi-tion of minimal cloths.
In the light of these findings, we think that ultrasound phonocardiography combined with ANNs can represent an innovative instrument for an early detection of mechanical PVT. In this way, a precocious diagnosis could be no longer a mirage, avoiding the complications of aggressive medical therapies, to prevent rather than treat.
Am Heart J 2016;174:e1–e2. 0002-8703
© 2016 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ahj.2015.12.016
Vincenzo Tarzia, MD, PhD Alvise Guariento, MD Lorenzo Bagozzi, MD Cardiac Surgery Unit Department of Thoracic
Cardiac and Vascular Sciences, University of Padua E-mail:[email protected]
Andrea Bagno, PhD
Department of Chemical Process Engineering University of Padua
Tomaso Bottio, MD, PhD Gino Gerosa, MD Cardiac Surgery Unit Department of Thoracic
Cardiac and Vascular Sciences, University of Padua
References
1.Özkan M, Gündüz S, Gürsoy OM, et al. Ultraslow thrombolytic therapy: a novel strategy in the management of PROsthetic MEchanical valve Thrombosis and the prEdictors of outcomE: the Ultra-slow PROMETEE trial. Am Heart J 2015;170(2):409-18. [e1].
2. Roudaut R, Serri K, Lafitte S. Thrombosis of prosthetic heart valves: diagnosis and therapeutic considerations. Heart 2007;93(1): 137-42.
3. Kalçık M, Gürsoy MO, Yesin M, et al. Transesophageal echocardiography is an indispensable guide during thrombolytic therapy for prosthetic valve thrombosis. Am Heart J 2015;169(5):e13-4.
4. Tarzia V, Bortolussi G, Rubino M, et al. Evaluation of prosthetic valve thrombosis by 64-row multi-detector computed tomography. J Heart Valve Dis 2015;24(2):210-3.
5. Bagno A, Anzil F, Buselli R, et al. Bileaflet mechanical heart valve closing sounds: in vitro classification by phonocardiographic analysis. J Artif Organs 2009;12(3):172-81.
6.Bagno A, Anzil F, Tarzia V, et al. Application of wavelet analysis to the phonocardiographic signal of mechanical heart valve closing sounds. Int J Artif Organs 2009;32(3):166-72.
7.Melan G, Bellato A, Susin FM, et al. Ultrasound phonocardiography for detecting thrombotic formations on bileaflet mechanical heart valves. J Heart Valve Dis 2013;22(6):828-36.
8.Susin FM, Tarzia V, Bottio T, et al. In-vitro detection of thrombotic formation on bileaflet mechanical heart valves. J Heart Valve Dis 2011;20(4):378-86.
9.Fritzsche D, Eitz T, Laczkovics A, et al. Early detection of mechanical valve dysfunction using a new home monitoring device. Ann Thorac Surg 2007;83(2):542-8.