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Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Östergötlands Läns Landsting, Heart Centre.
Östergötlands Läns Landsting, Heart Centre.
Östergötlands Läns Landsting, Heart Centre.
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2004 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 42, no 6, 770-776 p.Article in journal (Refereed) Published
Abstract [en]

Tissue motion of the beating heart generates large movement artifacts in the laser Doppler perfusion monitoring (LDPM) signal. The aim of the study was to use tissue Doppler imaging (TDI) to localise intervals during the cardiac cycle where the influence of movement artifacts on the LDPM signal is minimum. TDI velocities and LDPM signals were investigated on three calves, for normal heartbeat and during occlusion of the left anterior descending coronary artery. Intervals of low tissue velocity (TDIint<1 cm s−1) during the cardiac cycle were identified. During occlusion, these intervals were compared with low LDPM signal intervals (LDPMint<50% compared with baseline). Low-velocity intervals were found in late systole (normal and occlusion) and late diastole (normal). Systolic intervals were longer and less sensitive to heart rate variation compared with diastolic ones. The overlap between LDPMint and TDIint in relation to TDIint length was 84±27% (n=14). The LDPM signal was significantly (p<0.001, n=14) lower during occlusion if calculated during minimum tissue motion inside TDIint), compared with averaging over the entire cardiac cycle without taking tissue motion into consideration. In conclusion, movement artifacts are reduced if the LDPM signal is correlated to the ECG and investigated during minimum wall motion. The optimum interval depends on the application; late systole and late diastole can be used.

Place, publisher, year, edition, pages
Springer, 2004. Vol. 42, no 6, 770-776 p.
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:liu:diva-22150DOI: 10.1007/BF02345210ISI: 000225543500006Scopus ID: 2-s2.0-10244245509Local ID: 1260OAI: oai:DiVA.org:liu-22150DiVA: diva2:242463
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Between the Probe and the Pump: An experimental study on cardiac performance analysis based on Echocardiography, tissue and laser Doppler
Open this publication in new window or tab >>Between the Probe and the Pump: An experimental study on cardiac performance analysis based on Echocardiography, tissue and laser Doppler
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Echocardiography is an ultrasound-based bedside, non-invasive and easily available cardiac diagnostic technique visualising the heart’s morphology and function. Quantification of cardiac wall motion can be measured with the tissue Doppler Imaging (TDI) modality which provides in humans a high diagnostic capacity to differentiate healthy from diseased myocardium with reduced function. Heart failure, as a consequence of, for example, myocardial or ischaemic heart disease, demands both bedside and intraoperative diagnostic procedures for myocardial functional and perfusion assessment. In the late stages of heart failure cardiac left ventricular assist devices (LVAD) may be the treatment of choice. Such new technologies are commonly evaluated in large animals before application in humans is accepted.

With the aim of evaluating TDI´s applicability and feasibility in a large animal model 21 calves (aged 3 months and weight around 70 kg), were studied with colour TDI (Paper I). Analysis was performed either during coronary artery occlusion when the laser Doppler perfusion imaging technique (LDMP) was refined (Paper II), or after implantation of the LVAD, Heart Mate II® (Papers III, IV). All animals were haemodynamically monitored (pressures, flows, heart rate) and ECG was continuously recorded. Transthoracic and epicardial echocardiography (TTE) were performed before and after sternotomy and intraoperatively during experimental progressive heart failure. Heart chamber dimensions, native stroke volume, systolic and diastolic regional basal myocardial peak velocities (cm/s; systolic S´, early diastolic E´, and atrial A´, strain (%), strain rate (s-1) and displacement (mm) were determined. Second harmonic imaging (SHI) was applied in order to better visualise air bubbles (Paper IV).

In Paper I compiled baseline values were established before and after sternotomy for central haemodynamic and echocardiographic parameters, including the TDI myocardial motion variables velocity, strain rate, strain and displacement. Blood pressure and heart rate changed significantly after sternotomy, but the TDI derived data did not change significantly.

In Paper II we report that movement artifacts of the laser Doppler myocardial perfusion measurements can be reduced, both when myocardium is normally perfused and during coronary occlusion, by using the TDI velocity registrations showing wall motion to be minimal. The optimum interval depends on the application but late systole as well as late diastole is preferred.

After LVAD implantation in Paper III the flow characteristics and myocardial motion during variations in afterload TDI show that myocardial velocities decrease concomitantly with myocardial depression and are significantly correlated to native stroke volume, heart rate, systemic arterial resistance and cardiac output, but not with left ventricular size, fractional shortening or pump speed. Echocardiography together with TDI thereby offers additional means for monitoring and quantifying residual myocardial function during LVAD treatment.

SHI is superior in the early detection of single air-bubbles in the ascending aorta prior to significant air embolism during manipulation of the LVAD pump speed, as shown in Paper IV. A prompt decrease in size of the left atrium during speed adjustment may be a warning that massive air embolism is imminent whereas the commonly used left atrial pressure not provide the same warning.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 55 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 2101
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-61518 (URN)978-91-7393-327-8 (ISBN)
Public defence
2010-11-26, Aulan, Hälsans Hus, Campus US, Linköpings universitet, Linköping, 09:00 (Swedish)
Opponent
Supervisors
Note
The title of article II is in the list of publications "Correlation between laser Doppler perfusion monitoring and myocardial tissue Doppler echocardiography in the beating heart" and in the published article the title is "Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging".Available from: 2010-11-16 Created: 2010-11-16 Last updated: 2012-05-09Bibliographically approved
2. Movement artifact reduction in laser Doppler blood flowmetry: myocardial perfusion applications
Open this publication in new window or tab >>Movement artifact reduction in laser Doppler blood flowmetry: myocardial perfusion applications
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Laser Doppler perfusion monitoring (LDPM) and imaging (LDPI) enable assessment of tissue microvascular perfusion. The techniques are based on the Doppler broadening of the optical spectrum occurring when coherent laser light is scattered by moving red blood cells (RBC). However, if tissue motion not related to moving RBCs is present, artifacts arise in the derived perfusion estimate. The aim of this thesis was to develop and evaluate methods to reduce tissue motion influence on the perfusion estimate in general and for the specific purpose of enabling myocardial perfusion monitoring in the beating heart.

An LDPM system, based on digital signal processing, was developed for myocardial perfusion assessment. To achieve an accurate estimate of the local microvascular perfusion, the varying myocardial tissue motion during the cardiac cycle is taken into account. By means of ECG-triggering, periods of minimum myocardial tissue motion can be pinpointed. The system and proposed methods were successfully evaluated both in an animal model (3 calves) and during coronary artery bypass grafting (CABG) on 13 humans. Animal studies showed the importance of processing during minimum tissue motion, at late diastole and/or late systole, to reduce movement artifacts. The human evaluation confirmed earlier animal findings and revealed low flow situations in the intraoperative phase. Influence of mechanical ventilation on the myocardial blood flow was found. The results justify investigation postoperative of CABG, where myocardial perfusion monitoring may give a rapid response to potential ischemia.

The influence of tissue motion on LDPI was studied in model measurements and on the skin. A relatively large tissue velocity, compared to microvascular flow velocities, was needed to significantly influence the perfusion signal. Movement artifact magnitude depended on the movement direction and the surface structure. An LDPI system utilizing a polarization technique that blocks specularly reflected light is proposed. The method was evaluated in a flow model and on the skin of 12 subjects and was found to significantly reduce influence from tissue motion. Finally, a theoretical explanation of the origin of LDPI movement artifacts is proposed. Reduction of movement artifacts makes measurements more reliable and increases the potential of LDPI as a clinical tool.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2005. 84 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 935
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-28804 (URN)13992 (Local ID)91-85297-73-9 (ISBN)13992 (Archive number)13992 (OAI)
Public defence
2005-04-29, Linden, ingång 65, Campus US, Linköpings universitet, Linköping, 09:15 (English)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-11-30Bibliographically approved

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Karlsson, M G DanielHübbert, LailaJanerot-Sjöberg, BirgittaAhn, Henrik CasimirWårdell, Karin

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