Berliner und Munchener tierarztliche Wochenschrift2008; 121(3-4); 137-144;

[Influence of subclinical pulmonary findings on cardiac parameters in Icelandic horses].

Gehlen, H
·
Haubold, A
·
Rohn, K
·
Stadler, P

Abstract: In the present study we examined, if in Icelandic horses an increase in heart and/ or breathing rate is physiological and breed dependend or a sign of a pulmonary or cardiac disease. Therefore we examined 37 Icelandic horses with the prereport of being healthy. During clinical lung examination four horses showed symptoms of a pulmonary disease like increased breathing rate and enforced breathing at rest. These horses were excluded from the study. The other 33 horses were clinically normal. 17 of these horses were unridden (untrained) and 16 horses were regularly worked (trained). After clinical examination in all horses analysis of arterial blood gas, endoscopy with tracheo- bronchial secret analysis and radiographic examination of the lung were carried out. Additionally electro- and echocardiographic examinations and standardised exercise tests with determination of heart and breathing rate as well as plasma lactate values were performed in all horses. During electro- and echocardiographic examination no pathological findings were observed. In total 22 of the 33 horses showed abnormal lung findings. Seven horses had mild signs of RAO and 15 horses had mild signs of interstitial bronchitis. Three horses had additional pulmonary haemorrhage. Eleven out of the 33 horses showed no abnormal lung findings. The breathing rate at rest differed not significantly between horses with (21 +/- 1/min) or without (23 +/- 2/min) pulmonary findings. The heart rate also did not differ significantly between horses with (39 +/- 1/min) or without (42 +/- 1/min) pulmonary findings. In contrast to this the trained Icelandic horses with abnormal pulmonary findings had significantly higher heart rates (p = 0.01) and significantly lower breathing rates (p = 0.009) compared to those without abnormal pulmonary findings. During echocardiography Icelandic horses with abnormal pulmonary findings had significantly larger left atrial diameter (without abnormal pulmonary findings: 82 +/- 7 mm, with abnormal pulmonary findings: 90 +/- 8 mm, p = 0.02). Compared to the untrained Icelandic horses (5.4 +/- 2 mmol/l) the trained horses showed significantly lower plasma lactate values (3.1 +/- 2 mmol/l, p = 0.001) immediately after exercise. After exercise the icelandic horses with abnormal pulmonary findings had significantly higher breathing rates (p < 0.05) and longer recovery periods (30 minutes) than horses without abnormal respiratory findings (15 minutes). Recovery of heart rate after exercise showed no differences between groups.

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Publication Date: 2008-04-17 PubMed ID: 18412031

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Summary

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This research study investigates whether the increase in heart or breathing rate in Icelandic horses is a result of breed physiology or symptoms of lung or heart diseases. The study involves clinical examinations, blood gas analysis, radiographic lung examination, electrocardiography, echocardiography, and exercise tests on a group of 37 horses, resulting in findings that show abnormal lung conditions in many of the horses.

Objective of the Research

The aim of this study was to establish if an increase in heart and/or breathing rate observed in Icelandic horses is inherent to the breed or indicative of underlying pulmonary or cardiac diseases.

Methodology

Initially, 37 Icelandic horses suspected to be healthy were examined. However, four horses showed symptoms of pulmonary disease during the initial clinical lung examination and were consequently excluded from the study.
Among the remaining 33 horses, 17 were unridden (untrained), and 16 were regularly worked (trained).
All the horses underwent an in-depth series of tests including a clinical examination, arterial blood gas analysis, endoscopy with tracheo-bronchial secret analysis, radiographic lung examination, electrocardiography, echocardiography, and standardized exercise tests.

Findings

During electrocardiography and echocardiography, no pathological findings were observed.
However, out of the 33 horses, 22 showed abnormal lung findings. Mild signs of Recurrent Airway Obstruction (RAO) were found in seven horses, and mild signs of interstitial bronchitis in 15 horses. Pulmonary haemorrhage was detected in three horses.
The heart and breathing rates at rest of horses with and without pulmonary findings did not significantly differ.
However, trained Icelandic horses with abnormal pulmonary findings had significantly higher heart rates and lower breathing rates compared to horses without abnormal pulmonary findings.
The study also displayed that Icelandic horses with abnormal pulmonary findings had significantly larger left atrial diameter compared to horses without abnormal pulmonary findings.
Trained horses had significantly lower plasma lactate values immediately after exercise compared to untrained horses indicating better endurance and fitness.
Horses with abnormal pulmonary findings showed higher breathing rates and longer recovery periods post-exercise than horses without respiratory abnormalities. There was no significant difference in the recovery time of heart rates between the two groups.

Conclusions

The study suggests that increased heart and breathing rates in Icelandic horses might not solely be a breed characteristic but could potentially hint towards underlying pulmonary conditions.
This could lead to further research into pulmonary diseases in Icelandic horses and development of preventive measures.

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APA

Gehlen H, Haubold A, Rohn K, Stadler P. (2008). [Influence of subclinical pulmonary findings on cardiac parameters in Icelandic horses]. Berl Munch Tierarztl Wochenschr, 121(3-4), 137-144.