Emboli differentiation.literatur_neu

Differentiation of Emboli


Background:

The difficulty of distinguishing solid from air emboli using transcranial Doppler has limited its use in
situations where both types of emboli can occur, such as in mechanical heart valve patients.
Particulate microemboli are thought to be the most damaging.

Literature:

Analysis of index modulation in microembolic Doppler signals part I: radiation force as new
hypothesis-simulations.

(Girault, Kouamé, Ménigot, Souchon, u. a., 2011) Finally, by measuring FMI (calculated frequency modulation index) from simulated Doppler signals and by using a constant threshold of 1 KHz, it was possible to discriminate gaseous from solid microemboli with ease.
Analysis of index modulation of doppler microembolic signals part II: in vitro discrimination.

(Girault, Kouamé, Ménigot, Guidi, u. a., 2011) Finally, we showed by using FMI (calculated frequency modulation index) and PMI (position modulation index) that it is possible to discriminate gaseous from formed elements (<100 microns) despite the presence of the skull. The discrimination based on the FMI is an off-line technique allowing the analysis of standard TCD recordings. However, discrimination based on the PMI requires recordings obtained exclusively from a multi-gate system.
A method to distinguish between gaseous and solid cerebral emboli in patients with prosthetic
heart valves.

Since inhalation of 100% oxygen reduces the amount of air bubbles in mechanical heart valve patients, the ultrasonic features of the remaining emboli would be characteristic of solid particulates. Administration of 100% oxygen during transcranial Doppler examination in mechanical heart valve patients decreased the count of embolic signals compared with room air (p=0.006) A 16dB cut-off threshold achieved the best accuracy for differentiating non-gaseous from gaseous emboli (sensitivity: 60%; specificity: 82%; area: 0.721; p<0.0001) Embolic signals were detected during room air (n=141) and 100% oxygen (n=45) from 17 mechanical valve patients at two Doppler examinations (4h and 4 days after surgery)
Cerebral microemboli and brain injury during carotid artery endarterectomy and stenting.

(Skjelland, Krohg-Sørensen, u. a., 2009) Solid and gaseous microemboli were increased in patients with procedure-related ipsilateral ischemic strokes or new diffusion-weighted cerebral MRI lesions, which suggests that both solid and gaseous emboli may be harmful to the brain during CEA and carotid angioplasty with stenting. Eighty-five patients who were prospectively treated with CEA (61) or carotid angioplasty with stenting (30) for high-grade (>/=70%) internal carotid artery stenoses were monitored during the procedures using multifrequency transcranial Doppler with embolus detection and differentiation. Both, gaseous and solid emboli may be harmful
Introduction of an embolus detection system based on analysis of the transcranial Doppler
audio-signal.

Whether this algorithm can differentiate between gaseous and solid emboli has to be explored in future studies. suggests that it is capable of detecting discrete cerebral embolization in patients, and can discriminate between emboli and movement artefacts to a level which is similar to human experts. The results showed agreement in MES and artefact classification of > 93%. Data from patients in the post-operative phase of carotid surgery were used for the validation process System to distinguish between emboli and artefacts.
Solid and gaseous cerebral microembolization after biologic and mechanical aortic valve
replacement: investigation with multirange and multifrequency transcranial Doppler
ultrasound.

(Guerrieri Wolf, Choudhary, u. a., 2008) Solid microemboli accounted for 16% of the total microembolic load in group B (bilogical) compared with 31% in group M (mechanical, (P = .05)) at 3 months. Solid cerebral microemboli represent approximately one third of the total cerebral microembolic load after mechanical aortic valve replacement and are detectable in the majority of such patients both 5 days and 3 months after surgery (despite warfarin)
Gaseous and solid cerebral microembolization during proximal aortic anastomoses in off-
pump coronary surgery: the effect of an aortic side-biting clamp and two clampless devices.

Avoidance of aortic side clamping results in a significant reduction in the proportion of solid microemboli detected with transcranial Doppler. As solid microemboli are probably the most damaging, use of the Enclose and Heartstring devices may represent an important strategy for minimizing cerebral injury during proximal aortic anastomoses. Embo-Dop to avoid complications after aortic side clamping It is important to detect emboli to avoid complications.
Multifrequency transcranial Doppler for intraoperative automatic detection and
characterisation of cerebral microemboli during port-access mitral valve surgery.

In conclusion, brain embolism during port-access mitral valve procedures occurs predominantly at CPB start and during ascending aorta clamping and unclamping. Aortic arch navigation with catheters exposes to the risk of cerebral embolic events. 20 patients (6 male; age 56.5+/-6.4 years; BSA 1.6+/-0.1 m(2)) undergoing port-access mitral valve surgery, automated intraoperative transcranial Doppler was used to monitor absolute amount, side distribution, and type of embolic events during selected phases of the procedure to evaluate the impact of specific surgical manoeuvres on cerebral microembolism
Analysis of emboli during carotid stenting with distal protection device.

Microembolization frequently occurs during stenting even with deployment of the distal protection device. More solid emboli are seen during manipulations associated with lesion crossing. Although novel TCD methods yield a high frequency of embolic signals, further validation of this technique to determine the true nature, size, and number of emboli is needed. Patients undergoing carotid angiography and stenting Embo-Dop, DWL. Monitoring using the Filter Wire EX (Boston Scientific) and ACCUNET system (Guidant Corporation) was performed. Embo-Dop is useful to detect microembolisation, because they even occur during use of a protection device.
Can transcranial Doppler discriminate between solid and gaseous microemboli? Assessment
of a dual-frequency transducer system.

The Embo-Dop dual-frequency system allows better discrimination than a simple intensity threshold but it is not accurate enough for use in clinical or research studies. Further work is needed to develop reliable clinical systems for discrimination of emboli. 7 patients undergoing carotid surgery (= solid emboli) and 7 patients whom agitated saline was injected (= gaseous emboli). Embo-Dop has a good specifity but worse sensitivity.
Letter to the Editor
Embolus Detection and Differentiation Using Multifrequency Transcranial Doppler

Authors explain the limations of techniques, which were used by Markus and Punter and line out why they did not work. Publication of Markus et al. had limitations
Letter to the editor:
Embolus Differentiation Using Multifrequency Transcranial Doppler

The problem of distinguishing between signals from solid and gaseous emboli is clinically important, and the multifrequency technique an interesting approach. Unfortunately, its accuracy is limited by the impossibility of generating identical ultrasound beam shapes at different frequencies Emboli-differentiation is limited by technical reasons
Letters to the Editor
EmboDop: Insufficient Automatic Microemboli Identification

The authors agree with Markus and Punter. They line out some limitations.
Solid and gaseous cerebral microembolization during off-pump, on-pump, and open cardiac
surgery procedures.

The majority of microemboli occurring during cardiac surgery are gaseous, with a higher proportion of solid microemboli in the on-pump group, and may have a different significance for cerebral injury than solid microemboli. The ability to reliably discriminate gas and solid microemboli may have an important role in the implementation of neuroprotective strategies. Patients undergoing on-pump and off-pump cardiac surgery It is important to discriminate between gaseous and solid emboli
Automatic online embolus detection and artifact rejection with the first multifrequency
transcranial Doppler.

With multifrequency Doppler, 546 of these emboli (98.6%) and 791 of these artifacts (98.9%) were automatically detected and correctly classified as embolus or artifact (kappa=0.953, P<0.0001).
Online automatic discrimination between solid and gaseous cerebral microemboli with the first
multifrequency transcranial Doppler.

This study has shown that multifrequency transcranial Doppler can be used to automatically differentiate between solid and gaseous microemboli online. Patients undergoing cardiac valve or carotid surgery.
Summary:
The automatic differentiation between solid and gaseous emboli is limited because of its technical
limitations since it uses different frequencies like 2 and 2.5 MHz.
Varying of cut-off points like frequency threshold may leed to a higher accuracy as some authors
postulated recently.
Experts:

Markus
Brucher
Russell
Evans
Girault

Literature

Abu-Omar Y, Balacumaraswami L, Pigott DW, Matthews PM, Taggart DP. Solid and gaseous cerebral
microembolization during off-pump, on-pump, and open cardiac surgery procedures. J. Thorac.
Cardiovasc. Surg. 2004; 127: 1759-1765.[zitiert 2011 Nov 28]
Brucher R, Russell D. Automatic online embolus detection and artifact rejection with the first multifrequency transcranial Doppler. Stroke 2002; 33: 1969-1974.[zitiert 2011 Nov 28] Chen C-I, Iguchi Y, Garami Z, Malkoff MD, Smalling RW, Campbell MS, u. a. Analysis of emboli during carotid stenting with distal protection device. Cerebrovasc. Dis. 2006; 21: 223-228.[zitiert 2011 Nov 28] Evans DH. Embolus Differentiation Using Multifrequency Transcranial Doppler. Stroke 2006; 37: 1641.[zitiert 2011 Nov 28] Girault J-M, Kouamé D, Ménigot S, Guidi F, Souchon G, Remenieras J-P. Analysis of index modulation of doppler microembolic signals part II: in vitro discrimination. Ultrasound Med Biol 2011; 37: 102-111.[zitiert 2011 Dez 10] Girault J-M, Kouamé D, Ménigot S, Souchon G, Tranquart F. Analysis of index modulation in microembolic Doppler signals part I: radiation force as a new hypothesis-simulations. Ultrasound Med Biol 2011; 37: 87-101.[zitiert 2011 Dez 10] Guerrieri Wolf L, Abu-Omar Y, Choudhary BP, Pigott D, Taggart DP. Gaseous and solid cerebral microembolization during proximal aortic anastomoses in off-pump coronary surgery: the effect of an aortic side-biting clamp and two clampless devices. J. Thorac. Cardiovasc. Surg. 2007; 133: 485-493.[zitiert 2011 Nov 28] Guerrieri Wolf L, Choudhary BP, Abu-Omar Y, Taggart DP. Solid and gaseous cerebral microembolization after biologic and mechanical aortic valve replacement: investigation with multirange and multifrequency transcranial Doppler ultrasound. J. Thorac. Cardiovasc. Surg. 2008; 135: 512-520.[zitiert 2011 Nov 28] Keunen RWM, Hoogenboezem R, Wijnands R, Van den Hengel ACM, Ackerstaff RGA. Introduction of an embolus detection system based on analysis of the transcranial Doppler audio-signal. J Med Eng Technol 2008; 32: 296-304.[zitiert 2011 Dez 22] Markus HS, Punter M. Can transcranial Doppler discriminate between solid and gaseous microemboli? Assessment of a dual-frequency transducer system. Stroke 2005; 36: 1731-1734.[zitiert 2011 Nov 14] Maselli D, Pizio R, Musumeci F. Multifrequency transcranial Doppler for intraoperative automatic detection and characterisation of cerebral microemboli during port-access mitral valve surgery. Interact Cardiovasc Thorac Surg 2006; 5: 32-35.[zitiert 2011 Nov 28] Rodriguez RA, Nathan HJ, Ruel M, Rubens F, Dafoe D, Mesana T. A method to distinguish between gaseous and solid cerebral emboli in patients with prosthetic heart valves. Eur J Cardiothorac Surg 2009; 35: 89-95.[zitiert 2011 Nov 28] Russell D, Brucher R. Online automatic discrimination between solid and gaseous cerebral microemboli with the first multifrequency transcranial Doppler. Stroke 2002; 33: 1975-1980.[zitiert 2011 Nov 28] Russell D, Brucher R. Embolus Detection and Differentiation Using Multifrequency Transcranial Doppler. Stroke 2005; 36: 706.[zitiert 2011 Dez 25] Russell D, Brucher R. Embolus Detection and Differentiation Using Multifrequency Transcranial Doppler. Stroke 2006; 37: 340 -342.[zitiert 2011 Dez 25] Schoenburg M, Baer J, Schwarz N, Stolz E, Kaps M, Bachmann G, u. a. EmboDop: Insufficient Automatic Microemboli Identification. Stroke 2006; 37: 342 -343.[zitiert 2011 Dez 25] Skjelland M, Krohg-Sørensen K, Tennøe B, Bakke SJ, Brucher R, Russell D. Cerebral microemboli and brain injury during carotid artery endarterectomy and stenting. Stroke 2009; 40: 230-234.[zitiert 2011 Dez 23]

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