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4.2. Quantification of left ventricular volumes and function using
disease.
Anna Pilgram, Michael Fehr, Stephan O. Hungerbühler
Small Animal Clinic
University of Veterinary Medicine Hannover, Foundation Bünteweg 9
D-30559 Hannover, Germany
Corresponding author: Anna Pilgram, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, D-30559 Hannover, Germany, E-mail: anna.pilgram@tiho-hannover.de
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Abstract
Background:
In order to measure left ventricular volumes (LVV) the biplane Simpson’s method of discs (SMOD) is recommended in human medicine. However until now it is unclear if in veterinary medicine biplane SMOD gives further information than monoplane SMOD about a progressing volume overload.
Methods:
88 dogs affected with DMVD (stages B1, B2, C) classified according to the ACVIM consensus statement were included. Enddiastolic volume (EDV), endsystolic volume (ESV) and ejection fraction (EF) were measured with monoplane SMOD, using the right-parasternal four-chamber view (SMOD-R4) and left-apical two- (SMOD-L2) and 4-chamber view (SMOD-L4) as well as biplane SMOD (SMOD-BP). LVV were indexed with body weight (EDVI, ESVI). McNemar’s test was applied to detect diagnostic discrepancies between the methods. For group-comparison single factor variance analyses as well as a paired T-test for multiple pairwise comparisons of the normal distributed data were performed. Bland-Altman analysis was used to estimate the limits of agreement (BLAND a. ALTMAN 1986). A p-value < 0.05 was considered significant. LV parameters were compared within the examination planes and within the different stages of disease.
Results:
McNemar’s test revealed no diagnostic advantage of the biplane method in staging the DMVD. There were no significant differences of EDVI between the SMOD-BP and the monoplane methods. By comparing the differences of EDVI within stages B1 (n = 50), B2 (n = 23) and C (n = 16) for all chamber views (SMOD-BP, SMOD-R4, SMOD-L4) there were significances in every comparison with p-values </≤ 0.001.
EDVI increased as the disease progresses. The comparison between the healthy group [unpublished data] and stage B1 group showed significant differences in case of EDVI for SMOD-L4 (p = 0.03) and SMOD-R4 (p = 0.03), but not for ESVI. The differences of ESVI between the planes are very varying. SMOD-BP and SMOD-L4
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showed significances in stages B1 (p = 0.02) and B2 (p = 0.006). By comparing the differences of ESVI within the stages, all chamber views showed significances between stages B2/C and B1/C.
Conclusion:
There seems to be no additional diagnostically important information using the SMOD-BP in the event DMVD even in case of LVV overload. However, the biplane SMOD is the better methodology to reflect the LV shape and volume.
Abbreviations
:
1D one-dimensional 2D two-dimensional
ACVIM American College of Veterinary Internal Medicine ASE American Society of Echocardiography
BSA body surface area BW body weight
DMVD degenerative mitral valve disease
ED enddiastole
EDV enddiastolic volume EF ejection fraction
ES endsystole
ESV endsystolic volume
LA/Ao left atrial-to-aortic root ratio la2Ch left-apical two-chamber la4Ch left-apical four-chamber LV left ventricular
LVV left ventricular volume
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rp4Ch right-parasternal four-chamber SMOD Simpson’s method of discs
SMOD-R4, SMOD-BP, SMOD-L4, SMOD-L2: Simpson’s method of discs derived from the right-parasternal chamber, the biplane, the monoplane, the left-apical 4-chamber and left-apical 2-4-chamber view
Background
Degenerative mitral valve disease (DMVD) represents the most diagnosed acquired heart disease in dogs though typically small breed dogs are affected more often. The natural development of the disease is slowly progressive (HØIER OLSEN et al.
2010). However, mitral valve regurgitation combined with enddiastolic left-ventricular and -atrial volume overload are common findings in progressed stages of DMVD (SERRES et al. 2008; LJUNGVALL et al. 2011). The increase of left ventricular volumes (LVV) including the enddiastolic (EDV) and endsystolic volume (ESV) could be quantified by using different one-dimensional (1D) and two-dimensional (2D) techniques.
In veterinary medicine, left ventricular (LV) enlargement is usually detected by M-Mode based 1D echocardiographic measurements of the LV diameter (HANTON a.
LODOLA 1998; CORNELL et al 2004) despite the fact that the heart enlarges in every direction (LJUNGVALL et al. 2011). Due to the application of only one single sectional plane through the heart this 1D method admits sources of inaccuracy by estimating a three-dimensional volume from a single linear measurement (SAHN et al. 1978; LANG et al. 2005).
The most reliable 2D method is the Simpson´s method of discs (SMOD) in which the calculation of LVV are based on the summation of multiple discs. These are composed of the measured LV height divided by the number of discs (usually 15-20) and one or two measured diameters resulting from the LV border detection, consequent in a round or even ellipsoid cross section (LANG et al. 2005). Thus the monoplane SMOD utilizes for example only the left-apical four-chamber (la4Ch) view, whereas the biplane method additionally considers the left-apical two-chamber (la2Ch) view. In human guidelines the biplane SMOD is suspected to be more exact than the monoplane SMOD, because of the additional plane (LANG et al. 2005). In
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case of the Doberman Pinschers SMOD showed to be more sensitive than the 1D diameter measurement in detecting an enlargement of the LVV in case of a dilated cardiomyopathy (WESS et al. 2010). This method used a modified biplane version of the formula. Generally in veterinary medicine monoplane and (modified) biplane methods were described in many former studies in context of LVV measurements in dogs (SERRES et al. 2008; GERLACH 2009; PENZL 2009; TIDHOLM et al. 2010;
WESS et al. 2010; MEYER et al. 2013; SUZUKI et al. 2013; SMETS et al. 2014;
SECKERDIECK et al. 2015; DICKSON et al. 2016). However, none of the studies compared monoplane with biplane SMOD in case of the progression of DMVD. Many studies refer to breed specific reference values in healthy dogs (WESS et al. 2010;
SMETS et al. 2014; SECKERDIECK et al. 2015; DICKSON et al. 2016) and not to wider range of different smaller and larger dogs. Moreover these studies normalized the volumetric data to body surface area (BSA) as it is described in the human guidelines as well although there are suggestions to index LVV in dogs with body weight (BW) (SMETS et al 2014). In healthy dogs a previous study suggested 2.98 ml/kg (95% CI) as the normal upper threshold for LV EDV measured by biplane SMOD (unpublished data).
The aim of the present study was to compare LV variables of affected dogs with DMVD in a larger range of breeds measured by monoplane and biplane SMOD and normalized to BW.
Methods
The Animal Model
Eighty-eight dogs with DMVD in various disease stages (groups B1, B2, C according to the ACVIM consensus (HUNT et al. 2001; ATKINS et al. 2009)) owned by private persons were included in the study. All dogs were presented at the Small Animal Clinic, University of Veterinary Medicine Hannover, Germany for evaluation of heart disease. Dogs with a wide range of body weight were included. All dogs underwent a general physical, electrocardiographic as well as complete echocardiographic examination and Doppler-derived echocardiographic measurements. Diagnostic latero-lateral thoracic x-ray was only performed when indicated. DMVD was
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diagnosed based on the following criteria: thickened mitral valve leaflets and mitral regurgitation detected on color Doppler examination. Dogs with DMVD were classified according to the ACVIM consensus statement (stages B1, B2, C) (HUNT et al. 2001; ATKINS et al. 2009). In stage B patients showed no clinical signs caused by left-sided heart failure. Stage B1 dogs were defined as asymptomatic with no echocardiographic signs of cardiac remodeling, defined as left-atrial-to-aortic root ratio (LA/Ao) < 1.6 and normal LV dimensions (Index according to Cornell: EDDI <
1.85, ESDI < 1.26) (HANSSON et al. 2002; CORNELL et al. 2004). Stage B2 dogs were defined as asymptomatic, but with echocardiographic evidence of cardiac enlargement, defined as left atrial or ventricular dimensions above the cut-off values.
Stage C dogs were defined as clinical symptomatic; having a radiographically proven or a historical documented pulmonary edema. Any congenital or acquired heart diseases as well as haemodynamically relevant extracardiac diseases were exclusion criteria. For the comparison of stage B1 (according to the ACVIM consensus (HUNT et al. 2001; ATKINS et al. 2009)) and a healthy group, data of an unpublished study were used.
Echocardiography
Echocardiographic examinations of the unsedated dogs were performed using an ultrasound unit (a) equipped with M5S- (2.0-4.5 MHz, large breeds) and 6S- (4.0-8.0 MHz, small breeds) phased-array transducers in harmonic mode while simultaneous ECG monitoring in right and left recumbancy. Examinations were performed by one experienced person (S.O.H.), who optimized image quality consistently. Special attention was paid to ensure LV maximum length and to avoid the illustration of papillary muscles. All images and loops were stored and transmitted to a workstation, equipped with commercially available software (b). Off-line evaluation of the echocardiographic data was made by one person (A.P). LV internal dimensions of three digitally stored consecutive cardiac cycles were measured in enddiastole (ED) as well as endsystole (ES). Ejection fraction (EF) was calculated as follows:
𝐸𝐹 = [(𝐸𝐷𝑉 − 𝐸𝑆𝑉) ÷ 𝐸𝐷𝑉] × 100. Mean values were determined for further statistical analysis.
M-Mode echocardiography image acquisition
M-Mode echocardiographic imaging and measurements were performed according to the Guidelines of the American Society of Echocardio
2005), received from the long
was defined as the beginning of the QRS approximation of septum and LV free wall 1980). Leading-edge-to-leading
diameters (SAHN et al. 1978)
Figure 1 Representative left ventricular internal diameter measurement in enddiastole and endsystole of M
2DE Image acquisition and SMOD measurement For the 2D image acquisition and
of the la4Ch and la2Ch view as well as rp4Ch view the corresponding guidelines of 2D echocardiography in dogs as well
taken into account (THOMAS et al. 1993; LANG et al. 2005).
frame at the beginning of the QRS
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Mode echocardiography image acquisition
Mode echocardiographic imaging and measurements were performed according to merican Society of Echocardiography (ASE
, received from the long-axis right-parasternal four-chamber (
was defined as the beginning of the QRS-complex and ES as the point of maximal approximation of septum and LV free wall (SAHN et al. 1978; CRAWF
leading-edge method was utilized to measure LV internal (SAHN et al. 1978).
Representative left ventricular internal diameter measurement in enddiastole and endsystole of M-Mode images in a dog.
2DE Image acquisition and SMOD measurement
For the 2D image acquisition and volume acquisition using the SMOD measurement of the la4Ch and la2Ch view as well as rp4Ch view the corresponding guidelines of 2D echocardiography in dogs as well as the chamber quantification of the ASE were (THOMAS et al. 1993; LANG et al. 2005). ED was defined as the frame at the beginning of the QRS-complex immediately after mitral valve closure Mode echocardiographic imaging and measurements were performed according to SE) (LANG et al.
chamber (rp4Ch) view. ED complex and ES as the point of maximal (SAHN et al. 1978; CRAWFORD et al.
edge method was utilized to measure LV internal
Representative left ventricular internal diameter measurement in
SMOD measurement of the la4Ch and la2Ch view as well as rp4Ch view the corresponding guidelines of as the chamber quantification of the ASE were ED was defined as the complex immediately after mitral valve closure
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valve opening. SMOD measurement was performed by manually tracing the endocardial border of these selected frames in ED and ES. As recommended previously, papillary muscles and trabeculae were included in the internal volume (LANG et al. 2005). ED and ES maximum LV lengths were measured by an automated but manual adjustable line starting from the middle of the mitral valve annulus to the LV apex. LVV were calculated by specific software using the SMOD.
This formula is based on the summation of multiple (usually 15) discs. The heights of the discs are depending on the measured maximum length in ED and ES, whereas the diameters of the discs are derived by the LV border detection. The monoplane SMOD using only the right-parasternal chamber view (SMOD-R4), left-apical 4-chamber (SMOD-L4) or 2-4-chamber view (SMOD-L2) is resulting in a circular cross sectional area of the discs. Whereas the biplane SMOD (SMOD-BP), utilizing the longer of the 2 measured lengths, is considering both of the diameters for calculating an ellipsoid cross-sectional area. EDV and ESV indices (EDVI, ESVI) were calculated by dividing them by the body weight in kg (KW).
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Figure 2 Representative 2DE images of the left ventricle with Simpson’s method of discs (SMOD) measurements in a dog with degenerative mitral valve disease in stage B2
A SMOD using the left-apical 4-chamber view in enddiastole B SMOD using the left-apical 4-chamber view in endsystole C SMOD using the left-apical 2-chamber view in enddiastole D SMOD using the left-apical 2-chamber view in endsystole Measurement of the left atrial-to-aortic root ratio
The LA/Ao was obtained by the 2D rp4Ch view in order to detect an atrial enlargement thus to stage the disease. When LA/Ao was ≥ 1.6, the left atrium was considered enlarged. Measurements were performed as described in a former study (HANSSON et al. 2002).
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Statistical analysis
Statistical analyses were performed by commercially available computer software (c, d). A descriptive statistical analysis was used for age, body weight and sex. LVV normalized to BW (LVV Vol in ml/BW; LVVI) as well as EF was expressed as mean ± standard deviation (SD).
Besides the ACVIM classification, patients were classified having a normal or enlarged LV based on EDVI derived by SMOD measurements (BP, SMOD-L4, SMOD-R4, SMOD-L2). Patients who have larger values in ED measured by SMOD (control group is presented by previously published Cut-offs (95% CI)) or for EDDI ≥ 1.85 (M-Mode) were marked. In addition to the ACVIM consensus statement (stages B1, B2, C) (HUNT et al. 2001; ATKINS et al. 2009) patients were also classified as “correctly abnormal” in case of the SMOD measurements, if M-Mode derived EDD indices or LA/Ao ratios are over the thresholds mentioned previously. In case of the fact that the indexed EDV SMOD values (EDVI) were over the cut-off but the M-Mode derived EDD indices and LA/Ao ratio are not, there was done a follow-up of the M-Mode parameters respectively. If M-Mode parameters exceeded the cut-offs within one year, the SMOD values were judged as “correctly abnormal” as well.
Classification agreement of the biplane and monoplane (SMOD-L4, SMOD-R4) SMOD measurements was then evaluated applying the McNemar’s test for stages B1, B2 and C.
For group-comparison single factor variance analyses as well as a paired T-test for multiple pairwise comparisons of the normal distributed data were performed. Bland-Altman analysis was used to estimate the limits of agreement (BLAND a. ALTMAN 1986). A p-value of less than 0.05 was considered significant.
Results
Eighty-eight dogs weighting between 2.6–29.1 kg (mean: 12.7 kg; SD: 6.9; median:
10.3 kg) were included in the study. Ages ranged from 3.7 to 18.1 years (mean: 11.1 years; SD: 2.7; median: 11.2 years). A total of 72 pedigree dogs including 25 different breeds and 16 mixed breed dogs were represented. 36 dogs (41%) were female and
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52 dogs (59%) were male. All dogs were affected with DMVD and staged according to the ACVIM consensus statement (HUNT et al. 2001; ATKINS et al. 2009): 50 dogs were classified in stage B1, 21 dogs in stage B2 and 16 dogs in stage C. The details to age and weight are listed in Table 1.
Table 1 Distribution of age and weight of the study population with degenerative mitral valve disease staged in B1, B2 and C.
Age in years Bodyweight in kilogram
B1 B2 C B1 B2 C
Minimum 3.7 5.8 8.9 2.6 4.2 5.3
Maximum 15.3 18.1 16.3 29.1 29.0 23.5
Mean ±SD 10.5 (±2.7) 11.8 (±2.9) 11.7 (±2.0) 14.2 (±7.4) 10.1 (±5.7) 11.6 (±5.6)
Median 10.7 11.2 11.4 12.1 8.7 10.6
SD: Standard deviation
Classification agreement
Within the study group of B1 according to the ACVIM consensus statement (n = 50;
Index according to Cornell: EDDI < 1.85; LA/Ao < 1.6) there were patients who were over the cut-offs for SMOD (SMOD-BP, n = 6; SMOD-L4, n = 7; SMOD-L2, n = 5;
SMOD-R4, n = 11). After a follow-up examination most of them could be verified as
“correctly abnormal”: SMOD-BP, n = 5/6; SMOD-L4, n =6/7; SMOD-L2, n = 4/5;
SMOD-R4, n = 6/11). In stage B2 (n = 23; Index according to Cornell: EDDI ≥ 1.85 or LA/Ao ≥ 1.6) there were also patients with normal SMOD values even though these patients could be classified to be stage B2. Patients who could be classified to be
“correctly abnormal” were for SMOD-BP, n = 19; SMOD-L4, n = 20; SMOD-R4, n = 21 and for SMOD-L2, n = 14. In stage C all EDVI (SMOD) were over the cut-offs (n = 16). The McNemar’s test comparing the classification agreement between the comparison between SMOD-BP and monoplane SMOD-L4 (B1: p = 1.0; B2: p = 1.0) as well as SMOD-R4 (B1: p = 0.37; B2: p = 0.48) revealed exclusively non-significant differences.
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Table 2 Left ventricular SMOD parameters in stages B1, B2 and C
B1 B2 C
EDVI Mean ±SD Mean ±SD Mean ±SD
BP 2.52 0.45 3.49 0.61 5.05 0.97
L4 2.54 0.41 3.59 0.57 4.81 0.93
R4 2.49 0.40 3.60 0.62 4.97 1.07
L2 2.37 0.49 3.24 0.68 4.94 1.03
B1 B2 C
ESVI Mean ±SD Mean ±SD Mean ±SD
BP 1.13 0.24 1.22 0.22 1.79 0.52
L4 1.17 0.23 1.28 0.25 1.70 0.46
R4 1.09 0.23 1.17 0.27 1.54 0.39
L2 1.03 0.27 1.08 0.21 1.77 0.60
B1 B2 C
EF Mean ±SD Mean ±SD Mean ±SD
BP 55.21 5.53 64.56 6.15 64.31 4.26
L4 53.83 6.28 63.45 6.83 64.92 5.64
R4 56.00 7.33 67.16 6.15 69.03 3.20
L2 56.55 6.43 65.82 6.25 64.66 5.94
Mean and standard deviation (SD) in ml/kg of left ventricular enddiastolic (EDVI) and endsystolic (ESVI) volume indexed to body weight, as well as ejection fraction (EF) in % of dogs with mitral valve disease in stages B1, B2 and C measured with Simpson’s method of discs (SMOD) using the right-parasternal chamber view (SMOD-R4), the left-apical 4-chamber (SMOD-L4) and 2-4-chamber (SMOD-L2) view and both of them (SMOD-BP).
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EDVI
Comparison of different examination planes
There were no significant differences of EDVI (Table 3) the SMOD-BP and the monoplane methods like SMOD-L4 (B1: p = 0.33; B2: p = 0.08; C: p = 0.09) and SMOD-R4 (B1: p = 0.44; B2: p = 0.11; C: p = 0.60) in any of the stages. When comparing SMOD-L4 to SMOD-R4 there were no significant differences as well (B1:
p = 0.08; B2: p = 0.88; C: p = 0.42). SMOD-L4 and SMOD-L2 showed significant differences in stages B1 (p = 0.0005) and B2 (p = 0.001), but not for stage C (p = 0.54). Bland-Altman plots for EDVI and ESVI show good agreement (Figure 3, Figure 4).
Comparison of different stages of DMVD
By comparing the differences of EDVI within stages B1, B2 and C for all chamber views (Table 4) there were significances in every comparison with p-values </≤
0.001. EDVI increased as the disease progresses. The comparison between the healthy group [unpublished data] and stage B1 showed significant differences for SMOD-L4 (p = 0.03) and SMOD-R4 (p = 0.03).
ESVI
Comparison of different examination planes
There were significant differences of ESVI (Table 3) between BP and SMOD-L4 for stages B1 (p = 0.02) and B2 (p = 0.006), but not for stage C (p = 0.23). The comparison of SMOD-BP and SMOD-R4 revealed only significances for stage C (p = 0.002), but not for B1 (p = 0.16) and B2 (p = 0.20). There were significant differences between SMOD-L4 and SMOD-R4 for all stages (B1: p = 0.002; B2: p = 0.02; C: p = 0.05). SMOD-L4 and SMOD-L2 showed significant differences for stages B1 and B2 (p < 0.0001), but not for stage C (p = 0.56). Bland-Altman plots for EDVI and ESVI show good agreement Bland-Altman plots for EDVI and ESVI show good agreement (Figure 4).
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Comparison of different stages of DMVD
By comparing the differences of ESVI within the stages B1, B2 and C all chamber views (Table 4) showed significant differences between stages B2/C and B1/C, but not between the stages B1/B2: SMOD-BP (B1/B2: p = 0.19; B2/C: p = 0.0003; B1/C:
p = 0.0008); L4 (B1/B2: p = 0.29; B2/C: p = 0.005; B1/C: p = 0.005); SMOD-R4 (B1/B2: p = 0.31; B2/C: p = 0.003; B1/C: p = 0.002); SMOD-L2 (B1/B2: p = 0.37;
B2/C: p = 0.0002; B1/C: p = 0.0004). The comparison between the healthy group (former published/unpublished data) and stage B1 showed no significant differences for all chamber views.
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Figure 3 Bland-Altman scattergrams comparing the enddiastolic volume indices (EDVI) results of the left-apical (L4) and right-parasternal (R4) four-chamber views in comparison to biplane (BP) Simpson’s method of discs as reference method in CHIEF stages B1, B2 and C.
SD: Standard deviation; EDVI: enddiastolic volume index; ESVI: endsystolic volume index;
the line in central position represents the mean difference between the methods; the dotted horizontal lines represent the limits of agreement (mean ± 1.96 SD)
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Figure 4 Bland-Altman scattergrams comparing the endsystolic volume indices (ESVI) results of the left-apical (L4) and right-parasternal (R4) four-chamber views in comparison to biplane (BP) Simpson’s method of discs as reference method in CHIEF stages B1, B2 and C.
SD: Standard deviation; EDVI: enddiastolic volume index; ESVI: endsystolic volume index;
the line in central position represents the mean difference between the methods; the dotted horizontal lines represent the limits of agreement (mean ± 1.96 SD)
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EF
Comparison of different examination planes
There were significant differences of EF (Table 3) between SMOD-BP and SMOD-L4 for stage B1 (p = 0.02), but not for stages B2 (p = 0.07) and C (p = 0.53). SMOD-BP showed higher values. Significant differences were also seen when comparing SMOD-BP with SMOD-R4 for stages B2 and C (B1: p = 0.27; B2: p = 0.03; C: p =
<0.0001). EF was highest using SMOD-R4 and lowest using SMOD-L4 (Table 2).
There were exclusively significant differences between SMOD-L4 and SMOD-R4 (B1: p = 0.007; B2: p = 0.01; C: p = 0.002). The EF measured by SMOD-L4 and SMOD-L2 showed significant differences for B1 (p = 0.006) and B2 (p = 0.03), but not for stage C (p = 0.88).
Comparison of different stages of DMVD
On comparing the differences of EF within the stages all chamber views (Table 4) showed significant differences between B1/B2 (SMOD-BP, SMOD-L4, SMOD-R4, SMOD-L2: p = <0.0001; SMOD-L4: p = <0.0001; SMOD-R4: p = <0.0001; SMOD-L2:
p = <0.0001) and B1/C (SMOD-BP, SMOD-R4: p = <0.0001; SMOD-L4: p = 0.0002;
SMOD-L2: p = 0.0003). For B2/C the differences were exclusively non-significant (SMOD-BP: p = 0.96; SMOD-L4: p = 0.45; SMOD-R4: p = 0.20; SMOD-L2: p = 0.65).
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Table 3 Comparison of the left ventricular volumetric measurements considering different examination planes
B1 B2 C
EDVI MD ±SD MD ±SD MD ±SD
L4/R4 0.05 0.20 -0.01 0.30 -0.16 0.75
R4/BP -0.02 0.20 0.10 0.29 -0.08 0.59
L4/BP 0.03 0.20 0.09 0.24 -0.23 0.52
L2/L4 -0.18 * 0.34 -0.35 * 0.43 0.12 0.79
B1 B2 C
ESVI MD ±SD MD ±SD MD ±SD
L4/R4 0.08 * 0.17 0.11 * 0.21 0.15 * 0.28
R4/BP -0.04 0.17 -0.05 0.17 -0.24 * 0.26
L4/BP 0.04 * 0.13 -0.06 * 0.09 -0.09 0.28
L2/L4 -0.14 * 0.22 -0.19 * 0.16 0.07 0.48
B1 B2 C
EF MD ±SD MD ±SD MD ±SD
L4/R4 -2.17 * 5.42 -3.71 * 6.17 -4.10 * 4.26
R4/BP 0.79 5.03 2.61 * 5.05 4.71 * 3.40
L4/BP -1.38 * 3.99 -1.11 2.69 -0.61 3.75
L2/L4 2.72 * 6.65 2.37 * 4.73 -0.27 7.11
*significant difference (P-value < 0.05)
Statistical significance (p-value < 0.05) and mean difference (MD) with standard deviation (±SD) in ml/kg of the comparison of the examination planes between the enddiastolic (EDVI) and endsystolic (ESVI) volumes indexed to body weight and ejection fraction (EF) measured with Simpson`s method of discs using the right-parasternal 4-chamber view (R4), the left-apical 4-chamber (L4) and 2-chamber (L2) view and biplane (BP) of healthy dogs with mitral valve disease in stages B1 (n = 50), B2 (n = 22) and C (n = 16).
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Table 4 Comparison of the left ventricular volumetric measurements considering the different CHIEF stages
Table 4 Comparison of the left ventricular volumetric measurements considering the different CHIEF stages