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Quantification of cardiovascular flow and motion: aspects of regional myocardial function and flow patterns in the aortic root and the aorta
Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Department of Medicine and Care, Center for Medical Image Science and Visualization. Linköping University, Faculty of Health Sciences.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Quantification of cardiovascular flow and motion is essential in the diagnosis, treatment and follow-up of cardiovascular disease. The accuracy and quantification of many imaging methods used in this field have important shortfalls, however, that result from limitations in spatial and temporal dimensions. Improvement in application of these methods requires an in-depth understanding of the technical and perceptual aspects that contribute to errors in their use.

Visual assessment of echocardiographic images for asynchrony in regional myocardial motion during systolic contraction is an example of the need for better definition of limitations. The discernible delay in wall motion improved from 89 ms to 71 ms by allowing side-by-side comparison to normal motion. Clinically important delays are almost certainly missed with current "eyeballing" methods. Different and more quantitative approaches to this problem have been developed. Anatomic M-mode (AMM) assesses motion along an arbitrary line within a two-dimensional (2D) image, and was demonstrably robust in the clinical setting when used with second harmonic imaging at a depth less than 20 cm and with angle correction ofless than 60°. Doppler myocardial (DMI) imaging and strain rate imaging (SRI) were also shown to reliably demonstrate the effects of inotropic stimulation, total and severe ischemia on asynchrony in a closed chest pig model. Quantification of the changes induced by inotropy and total ischemia was possible with both methods, but the effects of stunning were not. Regional myocardial function and cardiovascular flow can also be assessed with time-resolved, three-directional, three-dimensional (3D) velocity data acquired using phase contrast magnetic resonance imaging (PC-MRI). This multidimensional data demonstrated longitudinal velocity gradients along all four walls of the left ventricle, with miuirnal apical longitudinal motion. The 3D velocity vector from single points in the ventricular wall shows that the motion over the cardiac cycle is complex in all dimensions. The flow patterns in the aortic root were also studied using time-resolved 3D PC-MRI in normal volunteers and patients who had undergone aortic-valve sparing surgery using straight Dacron grafts. In normals, vortices appeared in the sinuses of Valsalva in late systole, increased in size with the deceleration of aortic outflow and moved together as the valve closed in early diastole. These normal flow structures have never before been demonstrated in three dimensions in man. In the postoperative patients, lacking both sinuses and sinotubular junction, vortices were not observed.

Many imaging methods can be improved by a critical definition of the limits oftheir reliability. This can prompt the modifications and new methods which allow us to move beyond the original shortcomings and contribute new knowledge regarding the pathophysiology of cardiovascular disease.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2004. , 63 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 832
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-24209Local ID: 3803ISBN: 91-7373-804-2 (print)OAI: oai:DiVA.org:liu-24209DiVA: diva2:244526
Public defence
2004-02-20, Elsa Brändströmssalen, Universitetssjukhuset, Linköping, 13:00 (Swedish)
Opponent
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-10-29Bibliographically approved
List of papers
1. How accurate is visual assessment of synchronicity in myocardial motion? An in vitro study with computer-simulated regional delay in myocardial motion: clinical implications for rest and stress echocardiography studies
Open this publication in new window or tab >>How accurate is visual assessment of synchronicity in myocardial motion? An in vitro study with computer-simulated regional delay in myocardial motion: clinical implications for rest and stress echocardiography studies
1999 (English)In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 12, no 9, 698-705 p.Article in journal (Refereed) Published
Abstract [en]

Asynchronicity in echocardiographic images is normally assessed visually. No prior quantitative studies have determined the limitations of this approach. To quantify visual recognition of myocardial asynchronicity in echocardiographic images, computer-simulated delay phantom loops were generated from a 3.3 MHz digital image data from a normal left ventricular short-axis heart cycle acquired at 55 frames per second. Six expert observers visually assessed 30 abnormal and 3 normal loops with differing computer-induced delay patterns on 3 occasions and in this optimally simulated environment could recognize only single delays of 89 ms or more. This was improved to 71 ms or more by use of side-by-side (normal versus abnormal) comparative review. Thus visual assessment of clinically important regional delay in rest or stress echo images is limited.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26982 (URN)10.1016/S0894-7317(99)70019-2 (DOI)11617 (Local ID)11617 (Archive number)11617 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13
2. Anatomic M-mode echocardiography: a new approach to assess regional myocardial function - A comparative in vivo and in vitro study of both fundamental and second harmonic imaging modes
Open this publication in new window or tab >>Anatomic M-mode echocardiography: a new approach to assess regional myocardial function - A comparative in vivo and in vitro study of both fundamental and second harmonic imaging modes
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1999 (English)In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 12, no 5, 300-307 p.Article in journal (Refereed) Published
Abstract [en]

Objective: To evaluate the accuracy of anatomic M-mode echocardiography (AMM).

Methods: Eight phantoms were rotated on a device at different insonation depths (IDs) in a water beaker. They were insonated with different transducer frequencies in fundamental imaging (FI) and second harmonic imaging (SHI), and the diameters were assessed with conventional M-mode echocardiography (CMM) and AMM with the applied angle correction (AC) after rotation. In addition, left ventricular wall dimensions were measured with CMM and AMM in FI and SHI in 10 volunteers.

Results: AC had the greatest effect on the measurement error in AMM followed by ID (AC: R2 = 0.295, ID: R2 = 0.268; P < .0001). SHI improved the accuracy, and a difference no longer existed between CMM and AMM with an AC up to 60 degrees. In vivo the limit of agreement between AMM and CMM was -1.7 to +1.8 mm in SHI.

Conclusion: Within its limitations (AC < 60 degrees; ID < 20 cm), AMM could be a robust tool in clinical practice.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26981 (URN)10.1016/S0894-7317(99)70050-7 (DOI)11616 (Local ID)11616 (Archive number)11616 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13
3. Regional asynchrony in acute ischemia and stunning: an experimental myocardial velocity and strain rate imaging study
Open this publication in new window or tab >>Regional asynchrony in acute ischemia and stunning: an experimental myocardial velocity and strain rate imaging study
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Objective: To quantify motion and deformation asynchrony using Doppler myocardial imaging (DMI) during acute total ischemia, and stunning of the posterior left ventricular wall (PW) in comparison with the interventricular septum (IVS).

Methods: Ischemia of the PW was induced in closed-chest pigs using an angioplasty balloon positioned in the circumflex coronary artery. Animals were divided into three groups: normal controls (Group I - n = 6), total ischemia (Group II - n = 8), and stunning (Group III - n = 6) induced by coronary occlusion with distal coronary perfusion maintained via a perfusion catheter coupled to a roller pump (Group III). In addition, a 2-step dobutamine challenge (5 and 10 µg.kg-1 .min-1) was performed in groups I and III. Doppler myocardial velocity and strain rate cineloops were acquired from a parasternal short axis view.

Results: The pre-ejection time (T1) and the duration of regional mechanical systole (SYS) became shorter with inotropic stimulation. During total ischemia T1 was prolonged and SYS shortened significantly compared to baseline values [62 ± 14 vs. 55 ± 13 ms (P < 0.05)], [164 ± 13 vs. 240 ± 27 ms (P < 0.001)], respectively. The fraction T1/SYS was accordingly higher. No changes were observed for the contra lateral non-ischemic wall. In group III, the post-ischemic myocardium had a similar response as non-ischemic myocardium to the dobutamine challenge.

Conclusion: Consistent changes in local pre-ejection time and regional mechanical systole are induced by intropic stimulation and by total ischemia. However, the response to intropic stimulation did not differ between normal and stunned myocardium.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-84958 (URN)
Available from: 2012-10-29 Created: 2012-10-29 Last updated: 2012-10-29
4. Three-directional myocardial motion assessed using 3D phase contrast MRI
Open this publication in new window or tab >>Three-directional myocardial motion assessed using 3D phase contrast MRI
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2004 (English)In: Journal of Cardiovascular Magnetic Resonance, ISSN 1097-6647, E-ISSN 1532-429X, Vol. 6, no 3, 627-636 p.Article in journal (Refereed) Published
Abstract [en]

Regional myocardial function is a complex entity consisting of motion in three dimensions (3D). Besides magnetic resonance imaging (MRI), no other noninvasive technique can give a true 3D description of cardiac motion. Using a time‐resolved 3D phase contrast technique, three‐dimensional image volumes containing myocardial velocity data in six normal volunteers were acquired. Coordinates and velocity information were extracted from nine points placed in different myocardial segments in the left ventricle (LV), and decomposed into longitudinal (VL), radial (VR), and circumferential (VC) velocity components. Our findings confirm a longitudinal apex‐to‐base gradient for the LV, with only a small motion of the apex. The mean velocity for VL for all the basal segments was higher compared to the midsegments during systole [3.5 ± 1.2 vs. 2.5 ± 1.7 cm/s (p < 0.01)], early filling [− 6.9 ± 1.8 vs. − 4.9 ± 1.8 cm/s (p < 0.001)], and during atrial contraction [− 2.2 ± 1.4 vs. − 1.6 ± 1.3 cm/s (p < 0.05)]. A similar pattern was observed when comparing velocities from the midsegments to the apex. Radial velocity was higher during early filling in the midportion of the lateral [− 4.9 ± 2.7 vs. − 3.2 ± 1.6 cm/s (p < 0.05)] wall compared to the basal segments, no difference was observed for the septal [− 2.0 ± 1.5 vs. − 0.3 ± 2.5 cm/s (p = 0.15)], anterior [− 5.8 ± 3.3 vs. − 4.0 ± 1.7 cm/s (p = 0.17)], and posterior [− 2.3 ± 2.1 vs. − 2.5 ± 1.0 cm/s (p = 0.78)] walls. When observing the myocardial velocity in a single point and visualizing the movement of the main direction of the velocities in this point as vectors in velocity vector plots like planes, it is clear that myocardial movement is by no means one dimensional. In conclusion, our time‐resolved 3D, phase contrast MRI technique makes it feasible to extract myocardial velocities from anywhere in the myocardium, including all three velocity components without the need for positioning any slices at the time of acquisition.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-24306 (URN)10.1081/JCMR-120038692 (DOI)3929 (Local ID)3929 (Archive number)3929 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
5. Flow patterns in the aortic root and the aorta studied with time-resolved, 3-dimensional, phase-contrast magnetic resonance imaging: implications for aortic valve–sparing surgery
Open this publication in new window or tab >>Flow patterns in the aortic root and the aorta studied with time-resolved, 3-dimensional, phase-contrast magnetic resonance imaging: implications for aortic valve–sparing surgery
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2004 (English)In: Journal of Thoracic and Cardiovascular Surgery, ISSN 0022-5223, E-ISSN 1097-685X, Vol. 127, no 6, 1602-1607 p.Article in journal (Refereed) Published
Abstract [en]

Objective

Sparing the aortic valve has become a surgical option for patients who require repair of aortic root ectasia and have normal valve leaflets. Surgical approaches to valve sparing differ with regard to preservation of the native sinuses of Valsalva. The role of the sinuses and the importance of maintaining them remain controversial.

Methods

By using a time-resolved, 3-dimensional, phase-contrast magnetic resonance imaging technique, aortic root and aortic blood velocity data were acquired from 2 patients with Marfan syndrome 6 months after aortic valve–sparing surgery with straight Dacron grafts and contrasted with data from 6 normal volunteers.

Results

In normal aortas vortical blood flow became apparent in the individual sinuses after peak systole. The vortices filled the available space behind the valve leaflets and persisted until diastole, expanding and moving inward during aortic valve closure. In contrast, no vortices were observed in the postoperative patients with Marfan syndrome with negligible sinuses.

Conclusions

Changes in supravalvular flow accompany loss of sinus architecture. Whether the presence, size, and velocity of supravalvular vortices affects the function or durability of the preserved aortic valve remains to be studied.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-24305 (URN)10.1016/j.jtcvs.2003.10.042 (DOI)3927 (Local ID)3927 (Archive number)3927 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13

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Escobar Kvitting, John-Peder

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