Differences in ultrasound-derived arterial wall stiffness parameters and noninvasive blood pressure between Friesian horses and Warmblood horses

Spectral Doppler of aortic and carotid blood flow in horses with aortic valve regurgitation

OBJECTIVES

This study aimed to compare two-dimensional, M-mode, color, pulsed-wave Doppler (PWD) and continuous-wave Doppler (CWD) echocardiography, and PWD ultrasonography of the caudal common carotid artery (CCA) in horses with aortic regurgitation (AR).

ANIMALS

Warmblood horses without (n = 20) and with mild, moderate, and severe AR (n = 60) were included in the study.

MATERIALS AND METHODS

A retrospective descriptive study focused on cardiac dimensions, aortic and CCA Doppler flow. Non-invasive blood pressure and presence of ventricular arrhythmia were recorded. Groups were compared using analysis of variance, chi-square, Spearman's rho, and Kruskal-Wallis tests.

RESULTS

Maximal aortic antegrade flow velocity was higher in horses with moderate and severe AR than in normal horses and higher in those with severe AR than in those with mild AR (P<0.001). Mean (standard deviation) antegrade CCA flow velocities were 0.9 m/s (0.3 m/s) in normal horses and 1.0 m/s (0.2 m/s), 1.2 m/s (0.3 m/s), and 1.5 m/s (0.4 m/s) in horses with mild, moderate, and severe AR, respectively. Retrograde mid-to-end diastolic PWD ultrasonography of the common carotid artery (PWD-CCA) flow occurred in horses with moderate (6/20) and severe (13/20) AR. The presence of pathologic retrograde PWD-CCA flow was associated with presence of increased left ventricular dimensions and pulse pressures >60 mmHg. The CWD regurgitant jet pressure half-time failed to differentiate between AR severity grades.

STUDY LIMITATIONS

The limitations of this study included retrospective design with missing values, AR classification system not validated by longitudinal follow-up, and CCA retrograde velocities <10 cm/s not measured.

CONCLUSIONS

Pulsed-wave Doppler ultrasonography of the common carotid artery identifies moderate and severe AR in horses with hemodynamic overload. Presence of retrograde PWD-CCA flow was associated with moderate and severe AR and with left ventricular dilation. Quantification of CWD pressure half-time appeared unreliable for AR severity assessment.

Effect of physiological and pharmacological stress on heart rate, blood pressure, and echocardiographic measurements in healthy Warmblood horses

BACKGROUND

Echocardiographic measurements are important prognostic indicators but might be influenced by heart rate and blood pressure. This is particularly important when comparing repeated examinations.

HYPOTHESIS

To determine the effect of physiological stress at mildly increased heart rates and pharmacological challenge using IV administration of N-butylscopolammonium bromide and metamizol sodium on heart rate, blood pressure, and echocardiographic measurements.

ANIMALS

Twenty healthy Warmblood horses.

METHODS

Randomized crossover study. Horses were examined echocardiographically by 2-dimensional, M-mode, pulsed wave (PW) Doppler, and PW tissue Doppler imaging with simultaneous ECG recording and noninvasive blood pressure measurements during rest, physiological stress, and pharmacological challenge. Cardiac dimensions and functions were measured by a blinded observer. Data were analyzed using repeated-measures analysis of variance.

RESULTS

Mean heart rate and arterial blood pressure were significantly higher during physiological stress (46 ± 2 bpm, 93 ± 16 mm Hg) and pharmacological challenge (62 ± 13 bpm, 107 ± 17 mm Hg) compared with rest (34 ± 3 bpm, 86 ± 12 mm Hg; P < .05). Compared with rest, physiological stress resulted in increased left atrial fractional area change (34.3 ± 7.5 vs 27.3 ± 5.1%; P = .01) and left ventricular late diastolic radial wall motion velocity (13 ± 3 vs 10 ± 2 cm/s; P = .01) but had no significant effect on most other echocardiographic variables. Compared with rest, pharmacological challenge led to significantly decreased left atrial and diastolic ventricular dimensions (left ventricular internal diameter: 10.3 ± 0.9 vs 10.7 ± 0.8 cm; P = .01), increased aortic and pulmonary diameters, and ventricular wall thickness.

CONCLUSIONS AND CLINICAL IMPORTANCE

Physiological stress at mildly increased heart rates significantly enhanced atrial pump function. Larger heart rate and blood pressure increases during pharmacological challenge resulted in altered cardiac dimensions. This should be taken into account when evaluating echocardiographic measurements at increased heart rates.

A structural approach to 3D-printing arterial phantoms with physiologically comparable mechanical characteristics: Preliminary observations

Pulse wave behavior is important in cardiovascular pathophysiology and arterial phantoms are valuable for studying arterial function. The ability of phantoms to replicate complex arterial elasticity and anatomy is limited by available materials and techniques. The feasibility of improving phantom performance using functional structure designs producible with practical 3D printing technologies was investigated. A novel corrugated wall approach to separate phantom function from material properties was investigated with a series of designs printed from polyester-polyurethane using a low-cost open-source fused filament fabrication 3D printer. Nonpulsatile pressure-diameter data was collected, and a mock circulatory system was used to observe phantom pulse wave behavior and obtain pulse wave velocities. The measured range of nonpulsatile Peterson elastic strain modulus was 5.6–19 to 12.4–33.0 kPa over pressures of 5–35 mmHg for the most to least compliant designs respectively. Pulse wave velocities of 1.5–5 m s⁻¹ over mean pressures of 7–55 mmHg were observed, comparing favorably to reported in vivo pulmonary artery measurements of 1–4 m s⁻¹ across mammals. Phantoms stiffened with increasing pressure in a manner consistent with arteries, and phantom wall elasticity appeared to vary between designs. Using a functional structure approach, practical low-cost 3D-printed production of simple arterial phantoms with mechanical properties that closely match the pulmonary artery is possible. Further functional structure design development to expand the pressure range and physiologic utility of dir"ectly 3D-printed phantoms appears warranted.

Reference values for 2-dimensional and M-mode echocardiography in Friesian and Warmblood horses

BACKGROUND

Echocardiographic reference intervals for Friesian horses are poorly described.

OBJECTIVES

To obtain reference intervals for echocardiographic measurements in Friesians and compare these with Warmbloods.

ANIMALS

One hundred healthy adult Friesians and 100 healthy adult Warmblood horses.

METHODS

Cross-sectional study. Two-dimensional and M-mode echocardiographic images were obtained. Echocardiographic measurements, including size, area, and volumetric measurements of left atrium, left and right ventricle, aorta, and pulmonary artery, were performed. Measurements were compared between the 2 breeds using an independent samples t test with Bonferroni correction for multiple comparisons.

RESULTS

Reference ranges for standard echocardiographic measurements in Friesians were obtained. Several left ventricular measurements were significantly smaller in Friesians compared to Warmbloods, such as the left ventricular end-diastolic volume using the 4-chamber modified Simpsons' method (99.85% confidence interval for the difference [CI] = -245 to -63). Also the right ventricular end-diastolic and peak-systolic internal diameter were smaller in Friesians (99.85% CI = -1.33 to -0.6 and 99.85% CI = -1.54 to -0.76, respectively). Fractional shortening (99.85% CI = 0.61-6) and ejection fraction (99.85% CI = 0.21-4.6) were significantly larger. No structural effects of systemic hypertension, such as concentric hypertrophy, were detected.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our study provides reference intervals for echocardiographic measurements in Friesians useful in a clinical setting. In general, the left ventricular dimensions in Friesians were significantly smaller compared to Warmbloods, emphasizing the need for breed-specific reference intervals.

Neonatal glucocorticoid overexposure alters cardiovascular function in young adult horses in a sex-linked manner

Prenatal glucocorticoid overexposure has been shown to programme adult cardiovascular function in a range of species, but much less is known about the long-term effects of neonatal glucocorticoid overexposure. In horses, prenatal maturation of the hypothalamus-pituitary-adrenal axis and the normal prepartum surge in fetal cortisol occur late in gestation compared to other precocious species. Cortisol levels continue to rise in the hours after birth of full-term foals and increase further in the subsequent days in premature, dysmature and maladapted foals. Thus, this study examined the adult cardiovascular consequences of neonatal cortisol overexposure induced by adrenocorticotropic hormone administration to full-term male and female pony foals. After catheterisation at 2-3 years of age, basal arterial blood pressures (BP) and heart rate were measured together with the responses to phenylephrine (PE) and sodium nitroprusside (SNP). These data were used to assess cardiac baroreflex sensitivity. Neonatal cortisol overexposure reduced both the pressor and bradycardic responses to PE in the young adult males, but not females. It also enhanced the initial hypotensive response to SNP, slowed recovery of BP after infusion and reduced the gain of the cardiac baroreflex in the females, but not males. Basal diastolic pressure and cardiac baroreflex sensitivity also differed with sex, irrespective of neonatal treatment. The results show that there is a window of susceptibility for glucocorticoid programming during the immediate neonatal period that alters cardiovascular function in young adult horses in a sex-linked manner.

Age-related differences in blood pressure, ultrasound-derived arterial diameters and arterial wall stiffness parameters in horses

BACKGROUND

Arterial rupture mainly affects older horses. The reason why older horses are more prone to arterial rupture and which underlying vascular changes predispose older horses to aortic rupture is still unclear.

OBJECTIVES

To investigate the effect of ageing on the equine arterial wall and blood pressure.

STUDY DESIGN

Cohort study.

METHODS

Non-invasive blood pressure measurement using a tail cuff and vascular ultrasound from aorta, common carotid artery and external iliac artery was performed in 50 healthy young (3-7 years) and 50 healthy old Warmblood horses (>18 years). Arterial diameters and cross-sectional areas, and arterial wall thickness were measured offline. Regional arterial wall stiffness of the aorta and common carotid artery were assessed using pulse wave velocity, while lumen area/diameter change, strain, compliance and distensibility were calculated to assess local arterial wall stiffness.

RESULTS

No difference in blood pressure was found between old and young horses. All arterial dimensions and intima-media thickness of the common carotid artery were significantly larger in old horses. A significantly higher local arterial wall stiffness was found for the aorta and the caudal common carotid artery in older horses. For the external iliac artery, no significant differences in arterial wall stiffness were found. Both aortic and carotid pulse wave velocities were higher in older horses compared with younger horses.

MAIN LIMITATIONS

Blood pressure was measured non-invasively.

CONCLUSIONS

In horses, arteries stiffen with age, in combination with luminal enlargement and arterial wall thickening. This might, at least partially, explain the increased incidence of arterial rupture in older horses.

Differences in ultrasound-derived arterial wall stiffness parameters and noninvasive blood pressure between Friesian horses and Warmblood horses

Background

Aortic rupture is more common in Friesians compared to Warmbloods, which might be related to differences in arterial wall composition and, as such, arterial wall stiffness (AWS). Currently, nothing is known about differences in AWS between these breeds.

Objectives

Comparison of AWS parameters and noninvasive blood pressure between Friesians and Warmbloods.

Animals

One hundred one healthy Friesians and 101 age‐matched healthy Warmbloods.

Methods

Two‐dimensional and pulsed‐wave Doppler ultrasound examination was performed of the aorta, common carotid artery, and external iliac artery to define local and regional AWS parameters. Regional aortic AWS was estimated using aortic‐to‐external iliac artery pulse wave velocity (PWV_a‐e) and carotid‐to‐external iliac artery pulse wave velocity (PWV_c‐e). Noninvasive blood pressure and heart rate were recorded simultaneously.

Results

Systolic, diastolic, and mean arterial blood pressure and pulse pressure were significantly higher in Friesians compared to Warmbloods. No significant difference in heart rate was found. Most local AWS parameters (diameter change, compliance coefficient, distensibility coefficient) were significantly lower in Friesians compared to Warmbloods, indicating a stiffer aorta in Friesians. This difference could be confirmed by the regional stiffness parameters. A higher PWV_a‐e and PWV_c‐e was found in Friesians. For the cranial and caudal common carotid artery and external iliac artery, most local AWS parameters were not significantly different.

Conclusions and clinical importance

Results indicate that aortic AWS differs between Friesian and Warmblood horses. Friesians seem to have a stiffer aorta, which might be related to the higher incidence of aortic rupture in Friesians.