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Between the Probe and the Pump: An experimental study on cardiac performance analysis based on Echocardiography, tissue and laser Doppler
Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Cardiology UHL.
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: urn:nbn:se:liu:diva-61518ISBN: 978-91-7393-327-8 (print)OAI: oai:DiVA.org:liu-61518DiVA: diva2:370387
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
List of papers
1. Echocardiography and myocardial Doppler indices in the anesthetized calf: A closed and open chest study
Open this publication in new window or tab >>Echocardiography and myocardial Doppler indices in the anesthetized calf: A closed and open chest study
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Aim: the aim of this study was to provide baseline central hemodynamic and echocardiographic values in an anaesthetized calf model before and after sternotomy, and to include tissue Doppler imaging (TDI) modalities so that they may be applied to future anaesthetized calf models in cardiovascular research.

Method and results: twenty-one healthy anaesthetized calves were catheterized and invasively and echocardiographic monitored before and after sternotomy using a pulmonary artery catheter, left atrial and carotid artery catheters, and transthoracic or pericardial echocardiography. The following data were registered: heart rate, mean arterial pulmonary and systemic pressures, central venous pressure and saturation, cardiac output, left and right ventricular dimensions and their myocardial regional basal peak velocity and strain rate during systole, early diastolic and atrial filling and systolic peak strain and systolic displacement.

After sternotomy, the heart rate, systemic arterial pressure and left ventricular size increased, but other cardiovascular parameters, including echocardiographic myocardial velocities, strain and displacement did not change.

Conclusion: transthoracic and pericardial echocardiography including TDI, is feasible and applicable to the anaesthetized calf model. The normal ranges for baseline hemodynamic and echocardiographic variables derived from this study demonstrate that, as in humans, sternotomy influences basic hemodynamic variables such as heart rate, blood pressure and heart volumes but does not significantly affect TDI. The data collected may be useful in the future development of cardiovascular research using the anaesthetized calf model.

Keyword
Echocardiography; Animals; Echocardiography, Doppler; Heart; Haemodynamics
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-61457 (URN)
Available from: 2010-11-16 Created: 2010-11-16 Last updated: 2010-11-16
2. Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging
Open this publication in new window or tab >>Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging
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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
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-22150 (URN)10.1007/BF02345210 (DOI)000225543500006 ()2-s2.0-10244245509 (Scopus ID)1260 (Local ID)1260 (Archive number)1260 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-02-22Bibliographically approved
3. Axial flow pump treatment during myocardial depression in calves: an invasive hemodynamic and echocardiographic tissue Doppler study.
Open this publication in new window or tab >>Axial flow pump treatment during myocardial depression in calves: an invasive hemodynamic and echocardiographic tissue Doppler study.
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2008 (English)In: ASAIO journal (1992), ISSN 1058-2916, E-ISSN 1538-943X, Vol. 54, no 4, 367-371 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to investigate flow characteristics and myocardial function after implantation of an axial pump left ventricular assist device while varying afterload and during progressive myocardial depression. Ten calves were included, seven of which fulfilled the protocol. Invasive hemodynamic monitoring and echocardiography with color-coded systolic tissue Doppler velocity (TD velocity) were used during prepump conditions, at three different pump speeds, during modification of the systemic vascular resistance (SVR), and during increasing degrees of beta-blockade. The TD velocity decreased with the myocardial function whereas left ventricular size, fractional shortening, and pump speed did not correlate significantly with the TD velocity. The TD velocity correlated significantly with native stroke volume, heart rate, SVR and cardiac output but none of these alone could explain more than 20% of the changes in TD velocity. The axial flow pump studied is effective in unloading the severely depressed heart and has a high capacity for maintaining an adequate cardiac output, regardless of differing hemodynamic conditions, pump speed or decreasing LV function. Echocardiography with volumetric rendering and TD velocity imaging are valuable tools for monitoring and quantifying residual myocardial function during pump treatment.

Place, publisher, year, edition, pages
Philadelphia, PA USA: Lippincott Williams & Wilkins, 2008
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-44738 (URN)10.1097/MAT.0b013e31817fd8de (DOI)000257861700006 ()77509 (Local ID)77509 (Archive number)77509 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2014-01-21
4. Second Harmonic Echocardiography and Spontaneous Contrast during Implantation of a left Ventricular Assist Device
Open this publication in new window or tab >>Second Harmonic Echocardiography and Spontaneous Contrast during Implantation of a left Ventricular Assist Device
2010 (English)In: ASAIO journal (1992), ISSN 1058-2916, E-ISSN 1538-943X, Vol. 56, no 5, 417-421 p.Article in journal (Refereed) Published
Abstract [en]

Implantable mechanical left ventricular assist devices (LVADs) are used as a bridge or alternative to heart transplantation. Peroperative transesophageal echocardiography is commonly applied during implantation. Significant air embolism may occur as a result of air leakage at connections and anastomoses when LV filling becomes inadequate, and this must be prevented. Early suspicion and detection of air is mandatory to avoid negative circulatory effects. We hypothesized that monitoring of heart chamber size and occurrence of single air bubbles using second harmonic imaging (SHI) echocardiography may prevent risk for significant air embolism. After implantation of the LVAD in 10 calves, invasive hemodynamic monitoring and epicardial SHI were performed while increasing pump speed. Air bubbles in the ascending aorta were monitored and the left heart visualized for off-line dimensional analysis. Detection of air bubbles in the ascending aorta preceded their appearance in the left ventricle. They occurred exclusively but not always after a decrease in left atrial (LA) size. Decrease in LA pressure did not predict bubble detection or reduction in LA size. We conclude that SHI detects spontaneous ultrasound contrast during implantation of a LVAD and that a decrease in LA size is a warning that air embolism is imminent.

Place, publisher, year, edition, pages
Wolters Kluwer, 2010
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-61517 (URN)10.1097/MAT.0b013e3181e9261d (DOI)
Available from: 2010-11-16 Created: 2010-11-16 Last updated: 2014-01-13

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