Comparative cardiac macroscopic and microscopic study in cats with hyperthyroidism vs. cats with hypertrophic cardiomyopathy

Figures & data

Figure 1. The methods of gross pathological and histological morphometrical analysis. (A) The methodology of the gross measurements of the studied hearts that were conducted on the transverse section of the ventricular wall at the level of the upper third of the ventricle (below the valvular ring). (B) The methodology of the histological morphometric measurements of intramyocardial coronary arteries as proposed by Falk et al. (2006); picro sirius red stain, 200× magnification. AA: arterial area; aid: measured arterial internal diameter; AID: calculated arterial internal diameter; awt: measured arterial wall thickness; AWT: calculated arterial wall thickness; DWTR: arterial diameter-to-wall thickness ratio; HS: heart surface; IVS: interventricular septum; LAR: arterial lumen-to-area ratio; LVID: left ventricular internal diameter; LVLS: left ventricular lumen surface; LVS: left ventricular surface; LVW: left ventricular wall; LVWS: left ventricular wall surface; RVID: right ventricular internal diameter; RVLS: right ventricular lumen surface; RVW: right ventricular wall.

Table 1. The method of semi-quantitative histological evaluation of cardiomyocyte degeneration, myocardial inflammatory infiltration and myocardial disarray in the ventricular specimens of the examined animals based on Janus et al. (2016) and Biasato et al. (2015).

Score/feature	0	1	2	3
Cardiomyocyte degeneration	Normal myocardium	Subtle cardiomyocyte changes: loss of cross-striation	Moderate cardiomyocyte changes: cardiomyocyte swelling and cytoplasmic degeneration	Severe cardiomyocyte changes: hyperchromatosis and loss of cell structure
Myocardial inflammatory infiltration	No inflammatory cells	Single inflammatory cells dispersed in the myocardium	Multiple inflammatory cells dispersed in the myocardium	Multiple groups of inflammatory cells in the myocardium
Myocardial disarray (only left ventricular wall)	Absent	1–2 areas of disarray in the specimen	3–5 areas of disarray in the specimen	>5 areas of disarray in the specimen

The number of areas of disarray within the left ventricular wall specimen were successively counted and transformed into a semi-quantitative scale as presented in the Table.

Table 2. The age, sex, body weight and breed of the studied animals.

Group / parameter		Control group n = 10	FHT group n = 17	HCM group n = 13	p-values
Age [years] median (min–max)		1.5 (1–17)	14 (4–20.5)	5 (1–15)	^1p > 0.05 ^2p > 0.05 ^3p = 0.01
Sex (%M:%F)		60%:40%	58.8%:41.2%	53.8%:46.3%	p > 0.05
Body weight [kg] median (min–max)		4.65 (3–8)	4.5 (4–8)	4.7 (3.5–7.5)	p > 0.05
Breed (n)	DSH	6	14	5
	DLH	–	1	–
	BSH	2	–	2
	MCo	1	1	4
	Ragdoll	1	–	–
	Norwegian Forest	–	1	–
	Sphynx	–	–	1
	Scottish Fold	–	–	1

Values presented as median and range for age and body weight (non-parametric data) and ratio of male (M) and female (F) cats for sex; single p-value >0.05 presented in parameters without significant differences between the groups; particular p-values presented for the comparison of: control and FHT group (¹), control and HCM group (²) and FHT and HCM group (³) in parameters with significant differences between the groups. The significance level set at p ≤ 0.05. The significant p-values marked bold.

BSH: British Shorthair; DLH: domestic longhair; DSH: domestic shorthair; MCo: Maine Coon.

Table 3. The results of the pathomorphological examination of the studied hearts.

Group / parameter	Control n = 10	FHT n = 17	HCM n = 13	p-values
Heart weight [g] median (min–max)	15 (13–15)	22.5 (18–24)	34.5 (15–45)	^1p > 0.05 ^2p = 0.04 ^3p > 0.05
Heart height [mm] median (min–max)	38.2 (30.3–41.2)	41.3 (36.6–53.6)	50.2 (34.2–63.5)	^1p > 0.05 ^2p < 0.001 ^3p > 0.05
Heart width [mm] mean ± SD	25.8 ± 3.7	32.6 ± 3.3	34.2 ± 5.1	^1p = 0.003 ^2p < 0.001 ^3p > 0.05
Left atrial appendage height [mm] median (min–max)	10.9 (8.2–13.2)	16.0 (10–29.8)	25.4 (15.3–38)	^1p > 0.05 ^2p < 0.001 ^3p > 0.05
Left atrial appendage width [mm] median (min–max)	10.4 (8.4–11.8)	15.3 (12.5–16.9)	19.9 (12.6–34.2)	^1p = 0.03 ^2p < 0.001 ^3p > 0.05
Right atrial appendage height [mm] mean ± SD	10.8 ± 1.7	12.9 ± 3.7	15.3 ± 2.9	^1p > 0.05 ^2p = 0.004 ^3p > 0.05
Right atrial appendage width [mm] mean ± SD	9.5 ± 1.2	12.4 ± 3.1	13.7 ± 5.1	p > 0.05
LVW [mm] mean ± SD	6.6 ± 0.7	6.9 ± 1.7	10.1 ± 1.6	^1p > 0.05 ^2p < 0.001 ^3p < 0.001
LVID [mm] median (min–max)	6 (4.9–7.3)	7.3 (4.9–13.2)	9.4 (2.3–13.3)	p > 0.05
IVS [mm] mean ± SD	5.7 ± 0.7	6.0 ± 1.5	8.4 ± 1.0	^1p > 0.05 ^2p < 0.001 ^3p < 0.001
RVID [mm] mean ± SD	7.0 ± 1.7	6.1 ± 3.2	5.5 ± 2.7	p > 0.05
RVW [mm] mean ± SD	2.1 ± 0.5	2.9 ± 1.1	4.1 ± 1.4	^1p > 0.05 ^2<0.001 ^3p = 0.03
Heart surface [mm^2] median (min–max)	572.9 (478.8–745.2)	586.0 (380.0–1069.1)	852.6 (508.5–1326.4)	^1p > 0.05 ^2p = 0.01 ^3p = 0.01
Left ventricle surface [mm^2] median (min–max)	373.6 (358.9–471.9)	391.7 (284.8–680.9)	611.9 (392.7–1043.2)	^1p > 0.05 ^2p = 0.001 ^3p = 0.003
Left ventricular lumen surface [mm^2] median (min–max)	40.6 (17.1–46.7)	38.0 (11.5–203.4)	42.1 (7.0–166.9)	p > 0.05
Left ventricular wall surface [mm^2] median (min–max)	328.7 (314.9–436.0)	357.8 (236.6–477.5)	582.4 (380.3–986.0)	^1p > 0.05 ^2p = 0.002 ^3p < 0.001
Right ventricular lumen surface [mm^2] median (min–max)	69.7 (63.3–98.2)	74.6 (9.4–159.1)	46.1 (20.7–261.2)	p > 0.05

IVS: interventricular septum diameter; LVID: left ventricular internal diameter; LVW: left ventricular wall diameter; RVID: right ventricular internal diameter; RVW: right ventricular wall diameter; parametric data presented as mean ± SD; non-parametric data presented as median (min–max); single p-value >0.05 presented in parameters without significant differences between the groups; particular p-values presented for the comparison of: control and FHT group (¹), control and HCM group (²) and FHT and HCM group (³) in parameters with significant differences between the groups; the significance level set at p ≤ 0.05; the significant p-values marked bold.

Figure 2. The cross section of the ventricular walls in the control (A), FHT (B) and HCM (C) groups. The patient’s heart weight and their respective body weight: 15 g and 4.3 kg (A), 23 g and 5 kg (B), 39 g and 4 kg (C).

Figure 3. The results of the pathomorphological examination of the studied hearts. The results are presented as mean ± 95% confidence intervals. Values presenting significant differences are marked with asterisk (* or **). IVS: interventricular septum diameter; LAA: left atrial appendage; LV: left ventricle; LVW: left ventricular wall diameter; LVWs: left ventricular walls; RVW: right ventricular wall diameter.

Table 4. The results of the semi-quantitative histopathological analysis of the studied hearts.

Group / parameter		Control n = 10	FHT n = 17	HCM n = 13	p-values
LVW cardiomyocyte degeneration	median (min–max)	1 (0–1)	3 (1–3)	3 (1–3)	^1p < 0.001 ^2p = 0.001 ^3p > 0.05
	score 0	4	–	–
	score 1	6	2	1
	score 2	–	2	5
	score 3	–	13	7
IVS cardiomyocyte degeneration	median (min–max)	1 (0–1)	3 (1–3)	3 (1–3)	^1p < 0.001 ^2p < 0.001 ^3p > 0.05
	score 0	4	–	–
	score 1	6	2	1
	score 2	–	3	4
	score 3	–	12	8
RVW cardiomyocyte degeneration	median (min–max)	1 (0–1)	3 (0–3)	2 (1–3)	^1p < 0.001 ^2p = 0.02 ^3p > 0.05
	score 0	4	1	–
	score 1	6	0	3
	score 2	–	4	7
	score 3	–	12	3
LVW myocardial inflammatory infiltration	median (min–max)	0 (0–0)	0 (0–2)	0 (0–1)	p > 0.05
	score 0	10	15	11
	score 1	–	1	2
	score 2	–	1	–
	score 3	–	–	–
IVS myocardial inflammatory infiltration	median (min–max)	0 (0–0)	0 (0–2)	0 (0–0)	p > 0.05
	score 0	10	15	13
	score 1	–	1	–
	score 2	–	1	–
	score 3	–	–	–
RVW myocardial inflammatory infiltration	median (min–max)	0 (0–0)	0 (0–2)	0 (0–1)	p > 0.05
	score 0	10	14	11
	score 1	–	2	2
	score 2	–	1	–
	score 3	–	–	–
LVW myocardial disarray	median (min–max)	0 (0–0)	0 (0–3)	1 (0–3)	^1p > 0.05 ^2p = 0.003 ^3p = 0.01
	score 0	10	14	2
	score 1	–	–	6
	score 2	–	2	3
	score 3	–	1	2

IVS: interventricular septum; LVW: left ventricular wall; RVW: right ventricular wall; all data are non-parametric and presented as median (min–max); the number of animals showing score 0–3 are presented in the table; single p-value >0.05 presented in parameters without significant differences between the groups; particular p-values presented for the comparison of: control and FHT group (¹), control and HCM group (²) and FHT and HCM group (³) in parameters with significant differences between the groups; the significance level set at p ≤ 0.05; the significant p-values marked bold.

Table 5. The results of quantitative histopathological examination in the studied groups.

Group / parameter	Control n = 10	FHT n = 17	HCM n = 13	p-values
LVW cardiomyocyte diameter mean ± SD	13.6 ± 3.5	16.0 ± 2.9	19.9 ± 5.4	^1p > 0.05 ^2p = 0.002 ^3p = 0.03
IVS cardiomyocyte diameter mean ± SD	12.4 ± 1.1	17.2 ± 2.7	16.4 ± 1.9	^1p < 0.001 ^2p < 0.001 ^3p > 0.05
RVW cardiomyocyte diameter mean ± SD	10.7 ± 1.8	16.8 ± 3.5	14.9 ± 2.6	^1p < 0.001 ^2p = 0.004 ^3p > 0.05
LVW fibrosis [%] median (min–max)	6.0 (5.3–7.6)	6.6 (2.5–14.6)	7.1 (2.5–16.9)	p > 0.05
IVS fibrosis [%] median (min–max)	4.0 (2.8–5.0)	5.6 (1.4–11.2)	5.6 (1.1–16.2)	p > 0.05
RVW fibrosis [%] mean ± SD	7.61 ± 1.8	6.10 ± 2.6	5.85 ± 3.7	p > 0.05
LVW arterial diameter-to-wall thickness ratio median (min–max)	4.97 (3.67–5.76)	2.71 (1.44–3.60)	2.70 (2.25–4.73)	^1p < 0.001 ^2p = 0.001 ^3p > 0.05
IVS arterial diameter-to-wall thickness ratio mean ± SD	4.20 ± 0.36	2.97 ± 0.6	3.39 ± 1.1	^1p = 0.001 ^2p > 0.05 ^3p > 0.05
RVW arterial diameter-to-wall thickness ratio mean ± SD	4.40 ± 0.45	3.37 ± 1.4	3.54 ± 1.2	p > 0.05
LVW arterial lumen-to-area ratio median (min–max)	0.39 (0.31–0.41)	0.22 (0.13–0.29)	0.25 (0.19–0.39)	^1p < 0.001 ^2p = 0.01 ^3p > 0.05
IVS arterial lumen-to-area ratio mean ± SD	0.34 ± 0.04	0.24 ± 0.06	0.28 ± 0.06	^1p < 0.001 ^2p = 0.03 ^3p > 0.05
RVW arterial lumen-to-area ratio mean ± SD	0.38 ± 0.04	0.30 ± 0.09	0.35 ± 0.09	^1p = 0.02 ^2p > 0.05 ^3p > 0.05

IVS: interventricular septum; LVW: left ventricular wall; RVW: right ventricular wall; parametric data presented as mean ± SD; non-parametric data presented as median (min–max); single p-value >0.05 presented in parameters without significant differences between the groups; particular p-values presented for the comparison of: control and FHT group (¹), control and HCM group (²) and FHT and HCM group (³) in parameters with significant differences between the groups; the significance level set at p ≤ 0.05; the significant p-values marked bold.

Figure 4. The histological image of the intramural arteries in the examined cats. Picro sirius red stain; 200× magnification. (A, D, G) Control group; (B, E, H) FHT group; (C, F, I) HCM group; (A–C) left ventricular free wall; (D–F) interventricular septum; (G–I) right ventricular free wall. IVS: interventricular septum; LVW: left ventricular free wall; RVW: right ventricular free wall.

Figure 5. The results of the measurements of coronary arteries in the studied hearts. The results are presented as mean ± 95% confidence intervals. Values presenting significant differences are marked with asterisk (* or **). DWTR: arterial diameter-to-wall thickness ratio; IVS: interventricular septum; LAR: arterial lumen-to-area ratio; LVW: left ventricular wall; RVW: right ventricular wall.

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Data availability statement

The research data are available at the main author after reasonable request