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Evaluation of a Laser Doppler System for Myocardial Perfusion Monitoring
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Coronary artery bypass graft (CABG) surgery is a common treatment for patients with coronary artery disease. A potential complication of CABG is myocardial ischemia or infarction. In this thesis, a method - based on laser Doppler flowmetry (LDF) - for detection of intra- and postoperative ischemia by myocardial perfusion monitoring is evaluated.

LDF is sensitive to motion artifacts. In previous studies, a method for reduction of motion artifacts when measuring on the beating heart has been developed. By using the ECG as a reference, the perfusion signal is measured in intervals during the cardiac cycle where the cardiac motion is at a minimum, thus minimizing the artifacts in the perfusion signal.

The aim of this thesis was to investigate the possibilities to use the ECG-triggered laser Doppler system for continuous monitoring of myocardial perfusion in humans during and after CABG surgery. Two studies were performed. In the first study, changes in myocardial perfusion during CABG surgery were investigated (n = 13), while the second study focused on postoperative measurements (n = 13). In addition, an ECG-triggering method was implemented and evaluated.

It was found that the large variations in myocardial perfusion during CABG surgery could be monitored with the ECG-triggered laser Doppler system. Furthermore, a perfusion signal of good quality could be registered postoperatively from the closed chest in ten out of thirteen patients. In eight out of ten patients, a proper signal was obtained also the following morning, i.e., about 20 hours after probe insertion. The results show that respiration and blood pressure can have an influence on the perfusion signal.

In conclusion, the results indicate that the method is able to detect fluctuations in myocardial perfusion under favourable circumstances. However, high heart rate, abnormal cardiac motion, improper probe attachment and limitations in the ECG-triggering method may result in variations in the perfusion signal that are not related to tissue perfusion.

Abstract [sv]

Varje år utförs omkring 4500 kranskärlsoperationer i Sverige. En allvarlig komplikation som kan uppstå efter operationen är otillräcklig blodförsörjning till hjärtmuskeln. Den här licentiatavhandlingen handlar om utveckling och utvärdering av en metod, baserad på laserdopplerteknik, för att kunna upptäcka nedsatt blodperfusion i hjärtmuskeln på ett tidigt stadium.

Laserdopplertekniken är känslig för rörelsestörningar. I tidigare studier har en metod för reducering av rörelsestörningar vid mätning på slående hjärta tagits fram. Med EKG:t som referens mäts blodperfusionen i de faser under hjärtcykeln då hjärtats rörelse är som minst, vilket minskar bidraget av rörelsestörningar i blodperfusionssignalen.

I den här avhandlingen undersöks om metoden kan användas för kontinuerlig övervakning av hjärtmuskelns blodperfusion på patienter under och efter hjärtoperationer. Två studier har genomförts: en där hjärtmuskelns perfusion mättes i olika faser under kranskärlsoperationer och en där mätproben lades in i hjärtmuskeln under operationen och mätningar gjordes under det första dygnet efter operationen.

Det visade sig vara möjligt att följa förändringar i hjärtmuskelns blodperfusion under operation. Det var även möjligt att registrera en perfusionssignal av god kvalitet efter operationen då bröstkorgen var stängd. Hos åtta av tio patienter erhölls en bra signal även morgonen efter operationen, dvs. ca 20 timmar efter att proben lades in. Resultaten visar också att andning och blodtryck kan ha en påverkan på blodperfusionssignalen.

Slutsatsen av arbetet är att det går att se variationer i hjärtmuskelns blodperfusion med EKG-triggad laserdoppler under vissa förutsättningar. Signalen är dock i många fall svårtolkad på grund av att t ex hög hjärtfrekvens, onormal hjärtväggsrörelse eller ändrad probposition sannolikt kan ge variationer i perfusionssignalen som inte är relaterade till blodflödesförändringar.

Place, publisher, year, edition, pages
Institutionen för medicinsk teknik , 2007. , 53 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1326
Keyword [en]
Laser Doppler perfusion monitoring, myocardial microcirculation, coronary artery bypass graft
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:liu:diva-9584ISBN: 978-91-85831-16-6 (print)OAI: oai:DiVA.org:liu-9584DiVA: diva2:24015
Presentation
2007-09-17, IMT1, Institutionen för medicinsk teknik, Universitetssjukhuset, Linköping, 13:15 (English)
Opponent
Supervisors
Note
Report code: LIU-TEK-LIC-2007:35.Available from: 2007-08-27 Created: 2007-08-27 Last updated: 2016-05-04
List of papers
1. Myocardial perfusion monitoring during coronary artery bypass using an electrocardiogram-triggered laser Doppler technique
Open this publication in new window or tab >>Myocardial perfusion monitoring during coronary artery bypass using an electrocardiogram-triggered laser Doppler technique
2005 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 43, no 5, 582-588 p.Article in journal (Refereed) Published
Abstract [en]

Electrocardiogram (ECG)—triggered laser Doppler perfusion monitoring (LDPM) was used to assess myocardial perfusion, with minimum myocardial tissue motion influence, during coronary artery bypass grafting (CABG). Thirteen subjects were investigated at six phases: pre- and post-CABG; post aorta cross-clamping; pre and post left internal mammary artery (LIMA) graft declamping; and post aorta declamping. The perfusion signal was calculated in late systole and late diastole, with expected minimum tissue motion, and compared with arrested heart measurements. Patient conditions or artifacts caused by surgical activity made it impossible to perform and analyse data in all six phases for some patients. No significant (n=5) difference between perfusion signals pre- and post-CABG was found. Diastolic perfusion signal levels were significantly (p<0.02) lower compared with systolic levels. After aorta cross-clamping, the signal level was almost zero. A distinct perfusion signal increase after LIMA and aorta declamping, compared with pre-LIMA declamping, was found in ten cases out of 13. A significantly (p<0.04) lower perfusion signal in the arrested heart compared with in the beating heart was registered. Influence from mechanical ventilation was observed in 14 measurements out of 17. In conclusion, ECG-triggered LDPM can be used to assess myocardial perfusion during CABG. Perfusion signals were lower in the arrested heart compared with in the beating heart and in late diastole compared with late systole. No significant difference between pre- and post-CABG was found.

Place, publisher, year, edition, pages
Springer, 2005
Keyword
Laser Doppler perfusion monitoring, Coronary artery bypass grafting, Beating heart, Myocardial microcirculation, Movement artifacts, Electrocardiography
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-14612 (URN)10.1007/BF02351031 (DOI)000234262300007 ()2-s2.0-29244438810 (Scopus ID)
Available from: 2007-08-27 Created: 2007-08-27 Last updated: 2017-02-21Bibliographically approved
2. Analysis of breathing-related variations in ECG-triggered laser Doppler perfusion signals measured on the beating heart during surgery
Open this publication in new window or tab >>Analysis of breathing-related variations in ECG-triggered laser Doppler perfusion signals measured on the beating heart during surgery
2006 (English)In: Computers in cardiology, ISSN 0276-6574, Vol. 33, 181-184 p.Article in journal (Refereed) Published
Abstract [en]

Laser Doppler perfusion monitoring (LDPM) is a

method to assess microvascular perfusion. A modified,

ECG-triggered LDPM system has been developed to

measure myocardial perfusion with minimum influence

from heart motion. With this method, one systolic (PLS)

and one diastolic (PLD) perfusion value is obtained.

The aim of this study was to analyse breathing-related

variations in PLS and PLD measured during open-heart

surgery. The phase delays between PLS, PLD, mean

arterial blood pressure (MAP), heart rate and, indirectly,

the respiration were determined.

MAP tended to be in phase with or precede the

variations in PLD, i.e., PLD was at a maximum at the end

of inspiration or at the beginning of expiration. No clear

relation between PLS and any of the other signals could

be found.

National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-14613 (URN)2-s2.0-50149103402 (Scopus ID)
Available from: 2007-08-27 Created: 2007-08-27 Last updated: 2017-02-16Bibliographically approved
3. Determination of appropriate times during the cardiac cycle for online laser Doppler measurements of myocardial perfusion
Open this publication in new window or tab >>Determination of appropriate times during the cardiac cycle for online laser Doppler measurements of myocardial perfusion
2007 (English)Article in journal (Refereed) Submitted
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14614 (URN)
Available from: 2007-08-27 Created: 2007-08-27 Last updated: 2017-02-16Bibliographically approved

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