- Email: [email protected]
Can Computational Simulation Quantitatively Determine Mitral Valve Abnormalities?
1112
JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 9, 2015
Letters to the Editor
SEPTEMBER 2015:1111–6
F I G U R E 1 A Patient With LM Following a Prior Anterior Myocardial Infarction
4. Pouliopoulos J, Chik WW, Kanthan A, et al. Intramyocardial adiposity after myocardial infarction: new implications of a substrate for ventricular tachycardia. Circulation 2013;128:2296–308.
Can Computational Simulation Quantitatively Determine Mitral Valve Abnormalities? Various pathologies of the mitral valve (MV) apparatus include excessive annular dilation, chordal elongation, chordal rupture, and leaflet tissue enlargement, which lead to mitral regurgitation (MR) (1). The recommended treatment for these MV pathologies accompanied by severe MR is MV reconstruction, which has been shown to improve event-free survival (2). Echocardiography is the primary imaging modality to provide MV pathological information and the proper timing for consideration of MV repair (3). In a recent issue, we demonstrated 4 cases of computational evaluation of MV function (4). Here Computed tomography (CT) coronary angiography revealed an area of hypointense signal
we extend our patient-specific computational MV
in the anterior wall typical of lipomatous metaplasia (LM) (A). Steady-state free precession
evaluation studies to quantitatively determine the
cine imaging showed a chemical shift artifact within the anterior wall (B). T2–short TI
biomechanical and physiological characteristics of
inversion recovery (STIR)þ imaging revealed a hypointense area similar to that seen by CT
MV function involving severe annular dilation.
(C) that was not apparent on T2-STIR imaging (D). Late gadolinium enhancement imaging confirmed an anterior myocardial infarct with no evidence of microvascular obstruction (E). LM was associated with adverse outcome (F).
Five patients with normal MV and 5 patients with severe annular dilation accompanied by MR were
recruited,
and
3-dimensional
(3D)
trans-
esophageal echocardiography (TEE) was performed. Ify Mordi, MBChB Aleksandra Radjenovic, MSc, PhD Tony Stanton, MBChB, PhD Roy S. Gardner, MD Allan McPhaden, FRCPath David Carrick, MBChB Colin Berry, MD, PhD Nikolaos Tzemos, MD* *Institute of Cardiovascular and Medical Sciences
Patient-specific 3D TEE data were converted into computational MV models followed by dynamic simulations to evaluate MV function (5). Stress and contact pressure distributions across the mitral leaflets were determined at peak systole. A ratio of the coapted leaflet area to the entire posterior leaflet area was calculated and compared between the normal and pathological MV groups. The normal MVs clearly showed 3D cyclic deforma-
British Heart Foundation Glasgow
tion
Cardiovascular Research Centre
across the cardiac cycle. The pathological MVs dis-
University of Glasgow
playing severe MR revealed larger annular sizes and
Glasgow
less elliptical annular morphology compared with the
United Kingdom G12 8TA
normal MVs. Representative stress distributions across
E-mail: [email protected] http://dx.doi.org/10.1016/j.jcmg.2014.07.024
of
the
saddle-shaped
annular
morphology
the mitral leaflets at peak systole are demonstrated in Figures 1A and 1B. Symmetrical stress distribution patterns were found over both anterior and posterior
Please note: Dr. Berry has received research funding from Siemens Healthcare. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
leaflets in the normal MVs. In contrast, the pathological MVs with severe annular dilation revealed markedly asymmetrical stress patterns with high stress values
REFERENCES
spread along the radial direction. The pathological
1. Baroldi G, Silver MD, De Maria R, et al. Lipomatous metaplasia in left ventricular scar. Can J Cardiol 1997;13:65–71.
MVs demonstrated higher average maximum stress
2. Goldfarb JW, Roth M, Han J. Myocardial fat deposition after left ventricular myocardial infarction: assessment by using MR water-fat separation imaging. Radiology 2009;253:65–73.
(0.8 0.2 MPa). These excessive stress concentrations
3. Ichikawa Y, Kitagawa K, Chino S, et al. Adipose tissue detected by multislice computed tomography in patients after myocardial infarction. J Am Coll Cardiol Img 2009;2:548–55.
values (1.3 0.2 MPa; p < 0.01) than the normal MVs were found in regions involving incomplete leaflet coaptation. From a biomechanical perspective, this finding implies that severe annular dilation with normal left ventricular function generates high stresses
JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 9, 2015
Letters to the Editor
SEPTEMBER 2015:1111–6
F I G U R E 1 Determination of Physiological Abnormalities in MV Function Using Computational Simulation With
3-Dimensional Echocardiography
(A) Stress distributions across the mitral valve (MV) leaflets at peak systole. (B) Regional stress distributions in 6 subregions of MV leaflets at peak systole. (C) Contact pressure distributions between the leaflets at peak systole and the corresponding color Doppler ultrasound images. (D) Leaflet contact ratios at peak systole. A ¼ anterior; Al ¼ anterolateral; P ¼ posterior; Pm ¼ posteromedial.
across the leaflet and chordae tissue, causes consider-
clinical observations. A larger number of studies will
able tissue remodeling in the leaflets and chordae
allow us to determine critical stress values for leaflet
under high stresses (i.e., leaflet enlargement and
and chordal tissue, quantitate the degree of 3D leaflet
chordal elongation), and may induce a lack of leaflet
coaptation, and quantitatively evaluate and predict
coaptation, ultimately leading to significant MR.
the degree of MR progression.
Figure 1C demonstrates representative images of
In conclusion, computational simulation using
contact pressure distributions between the anterior and
patient-specific 3D TEE data provides quantitative
posterior leaflets at peak systole and the corresponding
information pertaining to biomechanical and physi-
color Doppler ultrasound images. The normal MVs
ological abnormalities in MV function. Combining
showed complete coaptation with full leaflet contact.
these techniques offers a novel strategy for patient-
The pathological MVs with severe annular dilation
specific MV evaluation and improved pre-surgical
revealed a large lack of leaflet contact, indicating
planning.
incomplete leaflet closure and a considerable degree of MR. These findings corresponded to the color Doppler
reduced leaflet contact ratios (0.19 0.03; p < 0.001)
Yonghoon Rim, PhD Krishnan B. Chandran, DSc Susan T. Laing, MD Patrick Kee, MD David D. McPherson, MD Hyunggun Kim, PhD*
compared with the normal MVs (0.33 0.04)
*Division of Cardiovascular Medicine
(Figure 1D). These quantitative data indicate that severe
Department of Internal Medicine
annular dilation with normal left ventricular function
The University of Texas Health Science Center at Houston
affects the degree and extent of leaflet coaptation.
6431 Fannin Street, MSB 1.246
ultrasound data. Although there was no regurgitation found in the normal MVs, a severe regurgitant jet was detected in the pathological MVs. The pathological MVs with severe annular dilation revealed markedly
A limitation of this study is that patients with complicated pathologies such as severe calcification and chordal rupture were excluded. Our study design allowed us to focus on investigation of the valvular geometric effects on MV dynamics and corresponding
Houston, Texas 77030 E-mail: [email protected] http://dx.doi.org/10.1016/j.jcmg.2014.09.011 Please note: This work was supported in part by the National Institutes of Health (R01 HL109597).
1113
1114
JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 9, 2015
Letters to the Editor
SEPTEMBER 2015:1111–6
REFERENCES
Coronary angiography showed a chronic total occlu-
1. Filsoufi F, Carpentier A. Principles of reconstructive surgery in degenerative mitral valve disease. Semin Thorac Cardiovasc Surg 2007;19:103–10.
(LCX), which was filled by grade III collateral flow from
sion (CTO) of the mid-left circumflex coronary artery
2. Adams DH, Rosenhek R, Falk V. Degenerative mitral valve regurgitation: best practice revolution. Eur Heart J 2010;31:1958–66.
the right coronary artery (RCA), whereas the left
3. Martin RP. How do we use imaging to aid considerations for intervention in patients with severe mitral regurgitation? Ann Cardiothorac Surg 2013;2:779–86.
significant stenoses (SYNTAX score ¼ 9.5). Cardiac
4. Rim Y, Laing ST, Kee P, McPherson DD, Kim H. Evaluation of mitral valve dynamics. J Am Coll Cardiol Img 2013;6:263–8.
stress-induced ischemia in the posterolateral wall.
5. Rim Y, McPherson DD, Chandran KB, Kim H. The effect of patient-specific annular motion on dynamic simulation of mitral valve function. J Biomech 2013;46:1104–12.
(PCI) was undertaken. An attempt to cross the lesion
anterior descending artery and RCA showed no magnetic resonance demonstrated the presence of Therefore, a CTO–percutaneous coronary intervention antegradely with an Ultimate Bros 3 guidewire (Asahi Intecc, Aichi, Japan) was performed, leading to vessel
Fate of Coronary Chronic Total Occlusion
dissection and advancement of the guidewire in the
Recanalization via Subintimal Tracking
false lumen and re-entering the true lumen more
With Bioresorbable Vascular Scaffolds:
distally (Figure 1A). Optical coherence tomography
A Temporary Cage for a Permanent New Lumen?
(OCT) (Ilumien, St. Jude Medical, St. Paul, Minnesota) after pre-dilation revealed the entry point into the
A 62-year-old man was admitted as a result of stable angina Canadian Cardiovascular Society class III.
subintimal space and re-entering in the true lumen (Figure 1B). Excellent angiographic and OCT results were obtained with the implantation of 2 (3.0 18 mm and 3.5 28 mm) overlapping bioresorbable vascular
F I G U R E 1 Baseline, Post-Scaffolding, and 1-Year Follow-Up of BVS Implantation
scaffolds (BVS) (Absorb, Abbot Vascular, Santa Clara, California). Notably, subintimal scaffolding leading to true lumen collapse in a short segment (9.7 mm) was well demonstrated by OCT (Figure 1C). Followup angiography and OCT were performed 1 year after the
index
procedure,
showing
optimal
results
(Figure 1D). The scaffold was well apposed in the subintimal space, whereas the magnitude of neointimal hyperplasia was comparable between the scaffold located at the subintimal and intimal space. In the present case, OCT clearly elucidated the mechanism of subintimal wire tracking and scaffolding. A previous study has shown the possible negative impact of subintimal metallic drug-eluting stent implantation, including late stent malapposition and fracture (1). The current case did not demonstrate late scaffold malapposition or exacerbated neointimal hyperplasia in the subintimal space. Although the scaffold enlargement demonstrated in our case was mostly due to hematoma absorption (i.e., healing), scaffold enlargement has recently been demonstrated late after BVS implantation (2). This Representative pictures of baseline (A and B), post-scaffold implantation (C), and 1-year follow-up (D) of bioresorbable vascular scaffold (BVS) implantation are demonstrated. Baseline (A and B): the angiographic image (A) illustrates the injection of the left coronary artery after the progression of the guidewire in the false lumen (yellow arrow). The white
particular feature of BVS could reduce concerns regarding late malapposition in complex scenarios, such as CTO-PCI (3). Because long-term follow-up is
arrow shows a side branch. The blue arrows highlight the position of the guidewire in the
not available, we believe that BVS implantation in
true lumen of the distal marginal branch. The cross-sectional optical coherence tomog-
the subintimal space should be considered only in
raphy (OCT) image (B) illustrates the subintimal space (red asterisk), where the guidewire
cases with short subintimal wiring without large
and the OCT catheter are located, and the true lumen (white asterisk). Post-scaffold
side branch compromise, whereas in cases with long
implantation (C): in this OCT image, the BVS appears well expanded and apposed in the subintimal space, whereas hematoma is observed in the true lumen. Follow-up (D): OCT
subintimal wiring with important side branch loss
image of 1-year follow-up is demonstrated. The scaffold is well expanded, apposed, and
(i.e., subintimal tracking and re-entry technique), it
covered in the subintimal space.
would not be recommended because of the possible risk of reocclusion (4).
JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 9, 2015
Letters to the Editor
SEPTEMBER 2015:1111–6
F I G U R E 1 A Patient With LM Following a Prior Anterior Myocardial Infarction
4. Pouliopoulos J, Chik WW, Kanthan A, et al. Intramyocardial adiposity after myocardial infarction: new implications of a substrate for ventricular tachycardia. Circulation 2013;128:2296–308.
Can Computational Simulation Quantitatively Determine Mitral Valve Abnormalities? Various pathologies of the mitral valve (MV) apparatus include excessive annular dilation, chordal elongation, chordal rupture, and leaflet tissue enlargement, which lead to mitral regurgitation (MR) (1). The recommended treatment for these MV pathologies accompanied by severe MR is MV reconstruction, which has been shown to improve event-free survival (2). Echocardiography is the primary imaging modality to provide MV pathological information and the proper timing for consideration of MV repair (3). In a recent issue, we demonstrated 4 cases of computational evaluation of MV function (4). Here Computed tomography (CT) coronary angiography revealed an area of hypointense signal
we extend our patient-specific computational MV
in the anterior wall typical of lipomatous metaplasia (LM) (A). Steady-state free precession
evaluation studies to quantitatively determine the
cine imaging showed a chemical shift artifact within the anterior wall (B). T2–short TI
biomechanical and physiological characteristics of
inversion recovery (STIR)þ imaging revealed a hypointense area similar to that seen by CT
MV function involving severe annular dilation.
(C) that was not apparent on T2-STIR imaging (D). Late gadolinium enhancement imaging confirmed an anterior myocardial infarct with no evidence of microvascular obstruction (E). LM was associated with adverse outcome (F).
Five patients with normal MV and 5 patients with severe annular dilation accompanied by MR were
recruited,
and
3-dimensional
(3D)
trans-
esophageal echocardiography (TEE) was performed. Ify Mordi, MBChB Aleksandra Radjenovic, MSc, PhD Tony Stanton, MBChB, PhD Roy S. Gardner, MD Allan McPhaden, FRCPath David Carrick, MBChB Colin Berry, MD, PhD Nikolaos Tzemos, MD* *Institute of Cardiovascular and Medical Sciences
Patient-specific 3D TEE data were converted into computational MV models followed by dynamic simulations to evaluate MV function (5). Stress and contact pressure distributions across the mitral leaflets were determined at peak systole. A ratio of the coapted leaflet area to the entire posterior leaflet area was calculated and compared between the normal and pathological MV groups. The normal MVs clearly showed 3D cyclic deforma-
British Heart Foundation Glasgow
tion
Cardiovascular Research Centre
across the cardiac cycle. The pathological MVs dis-
University of Glasgow
playing severe MR revealed larger annular sizes and
Glasgow
less elliptical annular morphology compared with the
United Kingdom G12 8TA
normal MVs. Representative stress distributions across
E-mail: [email protected] http://dx.doi.org/10.1016/j.jcmg.2014.07.024
of
the
saddle-shaped
annular
morphology
the mitral leaflets at peak systole are demonstrated in Figures 1A and 1B. Symmetrical stress distribution patterns were found over both anterior and posterior
Please note: Dr. Berry has received research funding from Siemens Healthcare. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
leaflets in the normal MVs. In contrast, the pathological MVs with severe annular dilation revealed markedly asymmetrical stress patterns with high stress values
REFERENCES
spread along the radial direction. The pathological
1. Baroldi G, Silver MD, De Maria R, et al. Lipomatous metaplasia in left ventricular scar. Can J Cardiol 1997;13:65–71.
MVs demonstrated higher average maximum stress
2. Goldfarb JW, Roth M, Han J. Myocardial fat deposition after left ventricular myocardial infarction: assessment by using MR water-fat separation imaging. Radiology 2009;253:65–73.
(0.8 0.2 MPa). These excessive stress concentrations
3. Ichikawa Y, Kitagawa K, Chino S, et al. Adipose tissue detected by multislice computed tomography in patients after myocardial infarction. J Am Coll Cardiol Img 2009;2:548–55.
values (1.3 0.2 MPa; p < 0.01) than the normal MVs were found in regions involving incomplete leaflet coaptation. From a biomechanical perspective, this finding implies that severe annular dilation with normal left ventricular function generates high stresses
JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 9, 2015
Letters to the Editor
SEPTEMBER 2015:1111–6
F I G U R E 1 Determination of Physiological Abnormalities in MV Function Using Computational Simulation With
3-Dimensional Echocardiography
(A) Stress distributions across the mitral valve (MV) leaflets at peak systole. (B) Regional stress distributions in 6 subregions of MV leaflets at peak systole. (C) Contact pressure distributions between the leaflets at peak systole and the corresponding color Doppler ultrasound images. (D) Leaflet contact ratios at peak systole. A ¼ anterior; Al ¼ anterolateral; P ¼ posterior; Pm ¼ posteromedial.
across the leaflet and chordae tissue, causes consider-
clinical observations. A larger number of studies will
able tissue remodeling in the leaflets and chordae
allow us to determine critical stress values for leaflet
under high stresses (i.e., leaflet enlargement and
and chordal tissue, quantitate the degree of 3D leaflet
chordal elongation), and may induce a lack of leaflet
coaptation, and quantitatively evaluate and predict
coaptation, ultimately leading to significant MR.
the degree of MR progression.
Figure 1C demonstrates representative images of
In conclusion, computational simulation using
contact pressure distributions between the anterior and
patient-specific 3D TEE data provides quantitative
posterior leaflets at peak systole and the corresponding
information pertaining to biomechanical and physi-
color Doppler ultrasound images. The normal MVs
ological abnormalities in MV function. Combining
showed complete coaptation with full leaflet contact.
these techniques offers a novel strategy for patient-
The pathological MVs with severe annular dilation
specific MV evaluation and improved pre-surgical
revealed a large lack of leaflet contact, indicating
planning.
incomplete leaflet closure and a considerable degree of MR. These findings corresponded to the color Doppler
reduced leaflet contact ratios (0.19 0.03; p < 0.001)
Yonghoon Rim, PhD Krishnan B. Chandran, DSc Susan T. Laing, MD Patrick Kee, MD David D. McPherson, MD Hyunggun Kim, PhD*
compared with the normal MVs (0.33 0.04)
*Division of Cardiovascular Medicine
(Figure 1D). These quantitative data indicate that severe
Department of Internal Medicine
annular dilation with normal left ventricular function
The University of Texas Health Science Center at Houston
affects the degree and extent of leaflet coaptation.
6431 Fannin Street, MSB 1.246
ultrasound data. Although there was no regurgitation found in the normal MVs, a severe regurgitant jet was detected in the pathological MVs. The pathological MVs with severe annular dilation revealed markedly
A limitation of this study is that patients with complicated pathologies such as severe calcification and chordal rupture were excluded. Our study design allowed us to focus on investigation of the valvular geometric effects on MV dynamics and corresponding
Houston, Texas 77030 E-mail: [email protected] http://dx.doi.org/10.1016/j.jcmg.2014.09.011 Please note: This work was supported in part by the National Institutes of Health (R01 HL109597).
1113
1114
JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 9, 2015
Letters to the Editor
SEPTEMBER 2015:1111–6
REFERENCES
Coronary angiography showed a chronic total occlu-
1. Filsoufi F, Carpentier A. Principles of reconstructive surgery in degenerative mitral valve disease. Semin Thorac Cardiovasc Surg 2007;19:103–10.
(LCX), which was filled by grade III collateral flow from
sion (CTO) of the mid-left circumflex coronary artery
2. Adams DH, Rosenhek R, Falk V. Degenerative mitral valve regurgitation: best practice revolution. Eur Heart J 2010;31:1958–66.
the right coronary artery (RCA), whereas the left
3. Martin RP. How do we use imaging to aid considerations for intervention in patients with severe mitral regurgitation? Ann Cardiothorac Surg 2013;2:779–86.
significant stenoses (SYNTAX score ¼ 9.5). Cardiac
4. Rim Y, Laing ST, Kee P, McPherson DD, Kim H. Evaluation of mitral valve dynamics. J Am Coll Cardiol Img 2013;6:263–8.
stress-induced ischemia in the posterolateral wall.
5. Rim Y, McPherson DD, Chandran KB, Kim H. The effect of patient-specific annular motion on dynamic simulation of mitral valve function. J Biomech 2013;46:1104–12.
(PCI) was undertaken. An attempt to cross the lesion
anterior descending artery and RCA showed no magnetic resonance demonstrated the presence of Therefore, a CTO–percutaneous coronary intervention antegradely with an Ultimate Bros 3 guidewire (Asahi Intecc, Aichi, Japan) was performed, leading to vessel
Fate of Coronary Chronic Total Occlusion
dissection and advancement of the guidewire in the
Recanalization via Subintimal Tracking
false lumen and re-entering the true lumen more
With Bioresorbable Vascular Scaffolds:
distally (Figure 1A). Optical coherence tomography
A Temporary Cage for a Permanent New Lumen?
(OCT) (Ilumien, St. Jude Medical, St. Paul, Minnesota) after pre-dilation revealed the entry point into the
A 62-year-old man was admitted as a result of stable angina Canadian Cardiovascular Society class III.
subintimal space and re-entering in the true lumen (Figure 1B). Excellent angiographic and OCT results were obtained with the implantation of 2 (3.0 18 mm and 3.5 28 mm) overlapping bioresorbable vascular
F I G U R E 1 Baseline, Post-Scaffolding, and 1-Year Follow-Up of BVS Implantation
scaffolds (BVS) (Absorb, Abbot Vascular, Santa Clara, California). Notably, subintimal scaffolding leading to true lumen collapse in a short segment (9.7 mm) was well demonstrated by OCT (Figure 1C). Followup angiography and OCT were performed 1 year after the
index
procedure,
showing
optimal
results
(Figure 1D). The scaffold was well apposed in the subintimal space, whereas the magnitude of neointimal hyperplasia was comparable between the scaffold located at the subintimal and intimal space. In the present case, OCT clearly elucidated the mechanism of subintimal wire tracking and scaffolding. A previous study has shown the possible negative impact of subintimal metallic drug-eluting stent implantation, including late stent malapposition and fracture (1). The current case did not demonstrate late scaffold malapposition or exacerbated neointimal hyperplasia in the subintimal space. Although the scaffold enlargement demonstrated in our case was mostly due to hematoma absorption (i.e., healing), scaffold enlargement has recently been demonstrated late after BVS implantation (2). This Representative pictures of baseline (A and B), post-scaffold implantation (C), and 1-year follow-up (D) of bioresorbable vascular scaffold (BVS) implantation are demonstrated. Baseline (A and B): the angiographic image (A) illustrates the injection of the left coronary artery after the progression of the guidewire in the false lumen (yellow arrow). The white
particular feature of BVS could reduce concerns regarding late malapposition in complex scenarios, such as CTO-PCI (3). Because long-term follow-up is
arrow shows a side branch. The blue arrows highlight the position of the guidewire in the
not available, we believe that BVS implantation in
true lumen of the distal marginal branch. The cross-sectional optical coherence tomog-
the subintimal space should be considered only in
raphy (OCT) image (B) illustrates the subintimal space (red asterisk), where the guidewire
cases with short subintimal wiring without large
and the OCT catheter are located, and the true lumen (white asterisk). Post-scaffold
side branch compromise, whereas in cases with long
implantation (C): in this OCT image, the BVS appears well expanded and apposed in the subintimal space, whereas hematoma is observed in the true lumen. Follow-up (D): OCT
subintimal wiring with important side branch loss
image of 1-year follow-up is demonstrated. The scaffold is well expanded, apposed, and
(i.e., subintimal tracking and re-entry technique), it
covered in the subintimal space.
would not be recommended because of the possible risk of reocclusion (4).