• View in gallery
    Figure 1

    CT scans of the mitral valve annulus in a normal dog presented in a soft tissue window. A—Representative oblique dorsal planar reformed image of the mitral valve annulus; cranial is to the top of the image, and the patient’s right side is on the left of the image. Sagittal plane reformed image (B) and transverse plane image (C) used to adjust the reformatting plane as depicted in (A). The oblique red lines represent the reformatting plane used in (A). D, E—Mitral valve annulus measurements acquired in all subjects. The black dots represent the locations of each trigone. CCD = Commissure-to-commissure distance. RC = Remainder of the circumference of the mitral valve annulus. SLD = Septal leaflet-to-lateral leaflet distance. TTD = Trigone-to-trigone distance.

  • View in gallery
    Figure 2

    Total annular circumference for all dogs by weight. The y-axis is the total annular circumference measured in millimeters and the x-axis is the weight of the dogs in increasing increments.

  • 1.

    Uechi M, Mizukoshi T, Mizuno T, et al. Mitral valve repair under cardiopulmonary bypass in small-breed dogs: 48 cases (2006–2009). J Am Vet Med Assoc. 2012;240(10):11941201. doi:10.2460/javma.240.10.1194

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2.

    Orton EC, Hackett TB, Mama K, Boon J. Technique and outcome of mitral valve replacement in dogs. J Am Vet Med Assoc. 2005;226(9):15081511. doi:10.2460/javma.2005.226.1508

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3.

    Fedak PWM, McCarthy PM, Bonow RO. Evolving concepts and technologies in mitral valve repair. Circulation. 2008;117(7):963974. doi:10.1161/CIRCULATIONAHA.107.702035

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4.

    Bothe W, Miller DC, Doenst T, Surgery C. Sizing for mitral annuloplasty: where does science stop and voodoo begin? Ann Thorac Surg. 2013;95(4):14751483. doi:10.1016/j.athoracsur.2012.10.023

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5.

    Vo AT, Nguyen NTH, Le KM, et al. Mitral prosthetic size predictor in minimally invasive mitral valve replacement. J Cardiothorac Surg. 2020;15(1):17. doi:10.1186/s13019-020-01197-w

    • Search Google Scholar
    • Export Citation
  • 6.

    Alkadhi H, Desboilles L, Stolzmann P, et al. Mitral annular shape, size, and motion in normals and in patients with cardiomyopathy. Invest Radiol. 2009;44(4):218225. doi:10.1097/RLI.0b013e3181994a73

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7.

    Banks T, Razeghi O, Ntalas I, et al. Automated quantification of mitral valve geometry on multi-slice computed tomography in patients with dilated cardiomyopathy: implications for transcatheter mitral valve replacement. J Cardiovasc Comput Tomogr. 2021;12(4):329337. doi:10.1016/j.jcct.2018.04.003

    • Search Google Scholar
    • Export Citation
  • 8.

    Wang H, Hanna JM, Ganapathi A, et al. Comparison of aortic annulus size by transesophageal echocardiography and computed tomography angiography with direct surgical measurement. Am J Cardiol. 2015;115(11):15681573. doi:10.1016/j.amjcard.2015.02.060

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9.

    Su SH. Computed tomography for planning and postoperative imaging of transvenous mitral annuloplasty: first experience in an animal model. Int J Cardiovasc Imaging. 2015;31(1):135142. doi:10.1007/s10554-014-0516-7

    • Search Google Scholar
    • Export Citation
  • 10.

    Blanke P, Dvir D, Cheung A, et al. A simplified D-shaped model of the mitral annulus to facilitate CT-based sizing before transcatheter mitral valve implantation. J Cardiovasc Comput Tomogr. 2021;8(6):459467. doi:10.1016/j.jcct.2014.09.009

    • Search Google Scholar
    • Export Citation
  • 11.

    Suh YJ, Lee S, Im DJ, et al. Added value of cardiac computed tomography for evaluation of mechanical aortic valve: emphasis on evaluation of pannus with surgical findings as standard reference. Int J Cardiol. 2016;214:454460. doi:10.1016/j.ijcard.2016.04.011

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12.

    Blanke P, Dvir D, Cheung A, Levine RA, Thompson C. Mitral annular evaluation with CT in the context of transcatheter mitral valve replacement. JACC Cardiovasc Imaging. 2015;8(5):612615. doi:10.1016/j.jcmg.2014.07.028

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13.

    Naoum, C, Leipsic J, Cheung A, et al. Mitral annular dimensions and geometry in patients with functional mitral regurgitation and mitral valve prolapse. Cardiovasc Imaging. 2016;9(3):269280. doi:10.1016/j.jcmg.2015.08.022

    • Search Google Scholar
    • Export Citation
  • 14.

    Packer RMA, Hendricks A, Volk HA, Shihab NK, Burn CC. How long and low can you go? Effect of conformation on the risk of thoracolumbar intervertebral disc extrusion in domestic dogs. PLoS One. 2013;8(7): e69650. https://doi.org/10.1371/journal.pone.0069650

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15.

    Truszkiewicz K, Poręba R, Gać P. Radiological cardiothoracic ratio in evidence-based medicine. J Clin Med. 2021;10(9):2016. doi:10.3390/jcm10092016.

  • 16.

    Camacho P, Fan H, Liu Z, He J. Large mammalian animal models of heart disease. J Cardiovasc Dev Dis. 2016;3(4):30. doi:10.3390/jcdd3040030

  • 17.

    Rizvi A, Marcus RP, Guo Y, et al. Dynamic computed tomographic assessment of the mitral annulus in patients with and without mitral prolapse. J Cardiovasc Comput Tomogr. 2020;14(6):502509. doi.org/10.1016/j.jcct.2020.02.005

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18.

    Sugirthabai H, Rajendran R, Seshayyan S, Victor A, Murugesan N, Sundaramurthi I. The study of mitral valve annular dimension in relation to the body surface area in the Indian population. Eur J Cardiothorac Surg. 2011;39(5):653656. doi:10.1016/j.ejcts.2010.08.052

    • Search Google Scholar
    • Export Citation

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Canine mitral valve size as measured by computed tomography

Wanda J. Gordon-EvansVeterinary Clinical Sciences Department, Veterinary Medical Center, University of Minnesota, St. Paul, MN

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K. Helena MontinVeterinary Clinical Sciences Department, Veterinary Medical Center, University of Minnesota, St. Paul, MN

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Christopher P. OberIdexx Telemedicine Consultants, Westbrook, ME

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Jessi L. CoryellBluePearl Pet Hospital, Eden Prairie, MN

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Andrea E. CastillaUC Davis Veterinary Medical Teaching Hospital, Davis, CA

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Abstract

OBJECTIVE

To measure the mitral annulus in dogs. Our hypothesis was that mitral measurement would be possible and consistent among observers using CT.

SAMPLE

Thoracic CT scans of dogs without known heart disease.

PROCEDURES

Five trained investigators measured 4 aspects of the mitral valve and the fourth thoracic vertebrae (T4) length using multiplanar reformatting tools. Ten randomly chosen animals were measured by all investigators to determine interobserver reliability.

RESULTS

There were 233 CT scans eligible for inclusion. Dogs weighed 2 to 96 kg (mean, 28.1 kg), with a variety of breeds represented. Golden Retrievers (n = 28) and Labrador Retrievers (n = 37) were overrepresented. The intraclass correlations were all greater than 0.9, showing excellent agreement between observers. The means and SDs of each measurement were as follows: trigone-to-trigone distance, 17.2 ± 4.7 mm; the remaining circumference, 79.0 ± 17.5 mm; commissure-to-commissure distance, 30.8 ± 6.5 mm; septal leaflet-to-lateral leaflet distance, 26.3 ± 6.0 mm; T4 length, 16.9 ± 3.1 mm; and the total circumference normalized by T4, 5.7 ± 0.7 mm.

CLINICAL RELEVANCE

This study provides information that may help in the development of future treatment for mitral valve dysfunction and subsequent annular enlargement.

Abstract

OBJECTIVE

To measure the mitral annulus in dogs. Our hypothesis was that mitral measurement would be possible and consistent among observers using CT.

SAMPLE

Thoracic CT scans of dogs without known heart disease.

PROCEDURES

Five trained investigators measured 4 aspects of the mitral valve and the fourth thoracic vertebrae (T4) length using multiplanar reformatting tools. Ten randomly chosen animals were measured by all investigators to determine interobserver reliability.

RESULTS

There were 233 CT scans eligible for inclusion. Dogs weighed 2 to 96 kg (mean, 28.1 kg), with a variety of breeds represented. Golden Retrievers (n = 28) and Labrador Retrievers (n = 37) were overrepresented. The intraclass correlations were all greater than 0.9, showing excellent agreement between observers. The means and SDs of each measurement were as follows: trigone-to-trigone distance, 17.2 ± 4.7 mm; the remaining circumference, 79.0 ± 17.5 mm; commissure-to-commissure distance, 30.8 ± 6.5 mm; septal leaflet-to-lateral leaflet distance, 26.3 ± 6.0 mm; T4 length, 16.9 ± 3.1 mm; and the total circumference normalized by T4, 5.7 ± 0.7 mm.

CLINICAL RELEVANCE

This study provides information that may help in the development of future treatment for mitral valve dysfunction and subsequent annular enlargement.

One current treatment option for severe mitral valve insufficiency is mitral valve repair.1 It is performed under cardiopulmonary bypass, similar to human repair for the same condition. Humans have a 90% success rate compared to variable rates in veterinary medicine.13 One difference between human and canine repair is that annuloplasty rings are usually implanted in humans to reduce the size of the annulus and oppose the mitral leaflets.1,3,4 In veterinary medicine, the surgeon may create an annuloplasty ring freehand with visual estimation and/or partially suture the commissures closed.1 Although annuloplasty rings help standardize the surgical procedure and prevent stenosis of the mitral valve in humans, they are not easily adapted to veterinary medicine as a result of size and inconsistency among manufacturers.4 In veterinary medicine, there are no established guidelines for size of the ring or the end resulting diameter needed for mitral valve repair.

We feel that the first step in developing an annuloplasty device for dogs is to measure the mitral annulus in normal dogs across breeds. CT has been used to measure valve sizes and to predict valve replacement and annulus size in humans using both ECG gated and nongated techniques.511

The purpose of this study was to measure the mitral annulus and report the trigone-to-trigone distance (TTD), remaining annular circumference, commissure-to-commissure distance (CCD), and septal leaflet-to-lateral leaflet distance (SLD) in dogs of varying size and breed, and evaluate 2 methods of normalization for dog size. In addition, interrater variability was measured.

Materials and Methods

Retrospectively, the postcontrast venous phase thoracic CT scans of dogs with noncardiac clinical disease, acquired using a Toshiba Aquilon 64 CFX 64-detector row CT scanner (Toshiba Medical Systems), were included in the study regardless of diagnostic indication. Scans were excluded if heart disease was diagnosed or suspected based on the presence of a murmur, clinical signs of overload (ie, progressive respiratory rate increases or respiratory distress), CT imaging abnormalities of the heart or great vessels, or if masses caused displacement of the heart. All CT examinations were performed with the patient under general anesthesia with IV fluid support and positioned in sternal or dorsal recumbency.

Additional standard parameters used for CT scans at our institution include a rotation time of 0.5 seconds, a pitch factor of 0.828, 120 kVp, and variable milliamps (20 to 200 mA, calculated by the scanner software [Sure Exposure 3D Version V3.35ER006; Toshiba Medical Systems]). After a noncontrast scan, patients were given 770 mg iodine/kg contrast medium (Optiray 350; Mallinckrodt Inc) followed by a 5-mL saline (0.9% saline) solution, and 3-phase angiography was performed. Arterial phase scans were initiated when the CT density of the aorta at the level of the diaphragm reached 180 HU. Venous and delayed phase images were acquired 15 and 90 seconds after the initiation of the arterial scan, respectively. Postcontrast images in the venous phase with a 0.5- to 1-mm slice thickness were used for reconstruction and measurements (VuePACS version 12.1.6; Carestream Health).

There were 5 investigators trained under the direction of a board-certified radiologist who measured the mitral annulus using multiplanar reformation tools based on previously published techniques.10,12,13 Ten randomly chosen dogs were measured by all 5 observers to determine whether systematic differences exist and to report the interrater variability, and the remaining dogs were allocated randomly to the observer.

Using multiplanar reformation tools, the image was manipulated to show the short-axis view of the mitral valve and the geometric D-shape of the annulus. Measurements were taken, including the TTD, the remaining circumference of the mitral annulus, the CCD, and the SLD (Figure 1). The length of the fourth thoracic vertebra (T4) was measured by manipulating the image to get a midsagittal view of the thoracic spine to allow measurement of the length of the T4 vertebral body.

Figure 1
Figure 1

CT scans of the mitral valve annulus in a normal dog presented in a soft tissue window. A—Representative oblique dorsal planar reformed image of the mitral valve annulus; cranial is to the top of the image, and the patient’s right side is on the left of the image. Sagittal plane reformed image (B) and transverse plane image (C) used to adjust the reformatting plane as depicted in (A). The oblique red lines represent the reformatting plane used in (A). D, E—Mitral valve annulus measurements acquired in all subjects. The black dots represent the locations of each trigone. CCD = Commissure-to-commissure distance. RC = Remainder of the circumference of the mitral valve annulus. SLD = Septal leaflet-to-lateral leaflet distance. TTD = Trigone-to-trigone distance.

Citation: American Journal of Veterinary Research 83, 12; 10.2460/ajvr.22.05.0085

Statistical analysis

The means and SDs were calculated for the sample population and all measurements. In addition, the total circumference was calculated by adding the TTD to the remaining circumference. The interrater reliability was evaluated using intraclass coefficients for all observers. The total circumference was divided by the T4 length and weight to determine whether standardization was possible, and a regression analysis was performed to provide correlation coefficients for these 2 methods of normalizing to body size. The total circumference was also graphed in 5-kg increments for visualization of the data. In addition, data are reported by breed if > 10 dogs of the breed were available.

Results

There were 233 CT scans eligible for inclusion. Dogs weighed between 2 and 96 kg (mean, 28.1 kg; median, 28.5 kg). Although a variety of breeds were represented, Golden Retrievers (n = 28) and Labrador Retrievers (n = 37) were over represented. Chondrodystrophic breeds based on Packer et al14 included Dachshund (n = 7), Basset Hound (n = 3), Beagle (n = 4), Bichon Frise (n = 1), Cavalier King Charles Spaniel (n = 2), Corgi (n = 1), English Bulldog (n = 2), Cocker Spaniel (n = 4), Jack Russel Terrier (n = 2), Maltese (n = 2), Miniature Poodle (n = 3), Pug (n = 2), and Shih Tzu (n = 1). There were 99 females (6 intact) and 134 males (11 intact). There was no difference in any measurement by sex. The intraclass correlations for all observers’ measurements were > 0.9, showing excellent agreement among observers (TTD, 0.91; remaining circumference, 0.96; CCD, 0.98; SLD, 0.95; and T4, 0.97).

The means and SDs of each measurement are presented in Table 1 for all dogs, Golden Retrievers, Labrador Retrievers, chondrodystrophic dogs, and small dogs by weight. The mean ± SD of the total circumference was 96.2 ± 2 mm. The total circumference normalized by the length of T4 was 5.7 ± 0.7 with an r2 value of 0.6. The total circumference normalized by weight was 4.4 ± 2.2 mm/kg with an r2 value of 0.5. The data normalized to T4 were normal, whereas the data normalized to weight were skewed. The total annular measurement is presented in 5-kg increments in Figure 2 for all dogs. The distribution and pattern were similar for all measurements when grouped by weight.

Table 1

Mean and SD for mitral annular measurements by category.

Variable n TTD (mm) RC (mm) CCD (mm) SLD (mm) T4 length (mm) Normalized to T4 lengtha
All dogs 233 17.2 ± 4.7 79.0 ± 17.5 30.8 ± 6.5 26.3 ± 6.0 16.9 ± 3.1 5.7 ± 0.7
Chondrodystrophic breeds 34 13.2 ± 4.1 60.6 ± 13.9 24.1 ± 15.3 19.8 ± 4.7 13.0 ± 1.9 5.7 ± 0.8
Labrador Retriever 37 19.7 ± 3.5 87.4 ± 11.0 35.2 ± 4.0 28.9 ± 4.2 17.8 ± 1.3 6.0 ± 0.6
Golden Retriever 28 17.9 ± 3.5 86.0 ± 13.6 33.0 ± 3.9 28.8 ± 4.6 18.2 ± 0.8 5.7 ± 0.8
Dogs < 5 kg 5 8.72 ± 4.0 46.7 ± 10.1 18.4 ± 3.7 15.2 ± 3.7 9.9 ± 1.4 5.6 ± 0.7
Dogs 5–9 kg 26 11.2 ± 2.6 54.4 ± 8.4 21.2 ± 3.5 17.6 ± 2.7 11.9 ± 1.3 5.5 ± 0.8
Dogs 10–14 kg 15 14.3 ± 3.6 62.0 ± 8.7 24.8 ± 3.0 20.3 ± 2.8 13.2 ± 1.1 5.8 ± 0.6

CCD = Commissure-to-commissure distance. RC = Remainder of the circumference of the mitral valve annulus. SLD = Septal leaflet-to-lateral leaflet distance. T4 = thoracic vertebrae 4. TTD = Trigone-to-trigone distance.

a

Total annular circumference divided by the length of T4.

Figure 2
Figure 2

Total annular circumference for all dogs by weight. The y-axis is the total annular circumference measured in millimeters and the x-axis is the weight of the dogs in increasing increments.

Citation: American Journal of Veterinary Research 83, 12; 10.2460/ajvr.22.05.0085

Discussion

This study reports the measurements of the mitral valve in a population of dogs using CT multiplanar reformation tools. Because the mitral valve is 3-D and saddle shaped, it may be argued that using a 2-D measurement technique may be an oversimplification of the anatomy. Although this may be true, multiple human studies have shown this measurement technique to be adequate for mitral annular sizing.6,7,12,13 The ideal study would have included a postmortem measurement of the annulus to determine the accuracy of our measurements.

The variation in annular size likely has many contributing factors, including interobserver variability, normal anatomic variation, subclinical heart disease, and measurement error resulting from motion and reconstruction artifacts. It is unlikely that those performing the measurements added much to the variation. All observers were trained as a group to optimize the view of the mitral annulus, limiting interobserver variation and maximizing agreement. Although this is a subjective process and can be difficult, agreement was excellent using this strategy. Others6 have reported excellent agreement in CT annular measurements as well.

Anatomic variation includes different breeds and sizes of dogs. It is reasonable to expect a 2-kg Chihuahua to have a different-size heart overall than a 96-kg Mastiff. The variation decreases considerably when normalized to size using the length of T4. This is depicted by the difference in measurements in Labrador Retrievers and chondrodystrophic breeds that washes out when the length of T4 is used to standardize it (Table 1). However, this is not an ideal standardization method, because only 60% of the variation in mitral circumference can be attributed to size as it relates to the length of T4. Weight was less advantageous, with only 50% of the variation attributable to variation in weight. If all dogs were at ideal body condition, it is possible that correlation would be better. In humans, body surface area is used to standardize valve sizes, but in this study, the information to calculate body surface area was not available.

In addition, it is unknown whether other factors affect mitral valve size and shape, such as athletic breeds or those with different conformations. Chest width is used to index heart size in humans. Actual width may not be appropriate to standardize different dog confirmations, but a similar measurement such as thoracic inlet diameter may prove to be a better standardizing measurement in future studies.15

Dogs have been used as models for human cardiovascular research because of similar-size hearts.16 The commissural distance in humans has been reported to be 33.4 ± 2.3 mm, which is similar to our study. Another study17 reported annular circumference in diastole as 123 ± 9 mm and systole as 109 ± 10 mm. This is similar to the Retrievers in our study in both measurement and variation. It is possible that studies presenting measurements with very low variation are examining homogeneous populations. There is evidence that variation may be greater when people are studied across world populations.18

In our study, dogs were excluded if a heart murmur was auscultated, heart disease was diagnosed previously, or the CT scan showed evidence of a heart abnormality. This includes routine evaluation of great vessels for evidence of fluid overload or deficiency. All of these are screening techniques and subjective. The gold standard for determining normal dogs is ECG evaluation. Therefore, some dogs with heart disease or disease contributing to significant blood volume changes may be contributing to the variation seen in this population.

The CT and associated software used in this study are designed to limit motion artifacts, but this does not negate the fact that the scans were not ECG gated. The mitral valve changes in size and shape from diastole to systole and some variation may be dependent on the phase when measured, which may be averaged by the software.6,17 It is possible that if heart motion had been eliminated as a factor, measurements would have been more accurate and possibly less variable. In humans, mitral valves have been imaged with more advanced equipment that is ECG gated and measured with software that allows 3-D mapping in all phases of contraction.6,7,13,17 In our study, this technology was not available and the methods were designed for the equipment that is available. Although more precise information is always preferred, full annuloplasty rings do not allow changes in annular size during diastole or systole, so it is possible that more precise measurement is not necessary for creating an annular ring, especially if D shaped.10,12,13

This study describes normal values for multiple mitral valve measurements using CT reconstruction. Our results provide valuable information for developing surgical and catheter-based treatments for mitral disease in the future.

Acknowledgments

No external funding was used in this study.

The authors declare that there were no conflicts of interest.

References

  • 1.

    Uechi M, Mizukoshi T, Mizuno T, et al. Mitral valve repair under cardiopulmonary bypass in small-breed dogs: 48 cases (2006–2009). J Am Vet Med Assoc. 2012;240(10):11941201. doi:10.2460/javma.240.10.1194

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2.

    Orton EC, Hackett TB, Mama K, Boon J. Technique and outcome of mitral valve replacement in dogs. J Am Vet Med Assoc. 2005;226(9):15081511. doi:10.2460/javma.2005.226.1508

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3.

    Fedak PWM, McCarthy PM, Bonow RO. Evolving concepts and technologies in mitral valve repair. Circulation. 2008;117(7):963974. doi:10.1161/CIRCULATIONAHA.107.702035

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4.

    Bothe W, Miller DC, Doenst T, Surgery C. Sizing for mitral annuloplasty: where does science stop and voodoo begin? Ann Thorac Surg. 2013;95(4):14751483. doi:10.1016/j.athoracsur.2012.10.023

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5.

    Vo AT, Nguyen NTH, Le KM, et al. Mitral prosthetic size predictor in minimally invasive mitral valve replacement. J Cardiothorac Surg. 2020;15(1):17. doi:10.1186/s13019-020-01197-w

    • Search Google Scholar
    • Export Citation
  • 6.

    Alkadhi H, Desboilles L, Stolzmann P, et al. Mitral annular shape, size, and motion in normals and in patients with cardiomyopathy. Invest Radiol. 2009;44(4):218225. doi:10.1097/RLI.0b013e3181994a73

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7.

    Banks T, Razeghi O, Ntalas I, et al. Automated quantification of mitral valve geometry on multi-slice computed tomography in patients with dilated cardiomyopathy: implications for transcatheter mitral valve replacement. J Cardiovasc Comput Tomogr. 2021;12(4):329337. doi:10.1016/j.jcct.2018.04.003

    • Search Google Scholar
    • Export Citation
  • 8.

    Wang H, Hanna JM, Ganapathi A, et al. Comparison of aortic annulus size by transesophageal echocardiography and computed tomography angiography with direct surgical measurement. Am J Cardiol. 2015;115(11):15681573. doi:10.1016/j.amjcard.2015.02.060

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9.

    Su SH. Computed tomography for planning and postoperative imaging of transvenous mitral annuloplasty: first experience in an animal model. Int J Cardiovasc Imaging. 2015;31(1):135142. doi:10.1007/s10554-014-0516-7

    • Search Google Scholar
    • Export Citation
  • 10.

    Blanke P, Dvir D, Cheung A, et al. A simplified D-shaped model of the mitral annulus to facilitate CT-based sizing before transcatheter mitral valve implantation. J Cardiovasc Comput Tomogr. 2021;8(6):459467. doi:10.1016/j.jcct.2014.09.009

    • Search Google Scholar
    • Export Citation
  • 11.

    Suh YJ, Lee S, Im DJ, et al. Added value of cardiac computed tomography for evaluation of mechanical aortic valve: emphasis on evaluation of pannus with surgical findings as standard reference. Int J Cardiol. 2016;214:454460. doi:10.1016/j.ijcard.2016.04.011

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12.

    Blanke P, Dvir D, Cheung A, Levine RA, Thompson C. Mitral annular evaluation with CT in the context of transcatheter mitral valve replacement. JACC Cardiovasc Imaging. 2015;8(5):612615. doi:10.1016/j.jcmg.2014.07.028

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13.

    Naoum, C, Leipsic J, Cheung A, et al. Mitral annular dimensions and geometry in patients with functional mitral regurgitation and mitral valve prolapse. Cardiovasc Imaging. 2016;9(3):269280. doi:10.1016/j.jcmg.2015.08.022

    • Search Google Scholar
    • Export Citation
  • 14.

    Packer RMA, Hendricks A, Volk HA, Shihab NK, Burn CC. How long and low can you go? Effect of conformation on the risk of thoracolumbar intervertebral disc extrusion in domestic dogs. PLoS One. 2013;8(7): e69650. https://doi.org/10.1371/journal.pone.0069650

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15.

    Truszkiewicz K, Poręba R, Gać P. Radiological cardiothoracic ratio in evidence-based medicine. J Clin Med. 2021;10(9):2016. doi:10.3390/jcm10092016.

  • 16.

    Camacho P, Fan H, Liu Z, He J. Large mammalian animal models of heart disease. J Cardiovasc Dev Dis. 2016;3(4):30. doi:10.3390/jcdd3040030

  • 17.

    Rizvi A, Marcus RP, Guo Y, et al. Dynamic computed tomographic assessment of the mitral annulus in patients with and without mitral prolapse. J Cardiovasc Comput Tomogr. 2020;14(6):502509. doi.org/10.1016/j.jcct.2020.02.005

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18.

    Sugirthabai H, Rajendran R, Seshayyan S, Victor A, Murugesan N, Sundaramurthi I. The study of mitral valve annular dimension in relation to the body surface area in the Indian population. Eur J Cardiothorac Surg. 2011;39(5):653656. doi:10.1016/j.ejcts.2010.08.052

    • Search Google Scholar
    • Export Citation

Contributor Notes

Corresponding author: Dr. Gordon-Evans (wgordone@umn.edu)