The ratio of cardiopulmonary blood volume to stroke volume as an index of cardiac function in horses.

The research developed a technique for measuring the ratio between cardiopulmonary blood volume and stroke volume in horses, presenting it as a viable index for cardiac function. The procedure was tested on horses in different health conditions and training states, and found a significant increase in the subjects with heart disease.

Methodology

• The study developed a new method to measure cardiac function in horses. This was achieved by determining the ratio of cardiopulmonary blood volume to stroke volume.
• They used a radioisotope, 99 Tc (technetium 99m pertechnetate), which they injected into the horse’s jugular vein as a bolus. The radioisotope was then detected in the heart’s right and left ventricles using a scanning device comprising various components such as a Na I crystal, collimator, amplifier, and discriminator.
• While conducting the test, the radiocardiogram (RCG) and electrocardiogram (ECG) were simultaneously recorded using a two-channel writing device.

Experimental Groups

• The research involved five types of horses: Thoroughbreds in training, showjumpers in training, horses not in training, horses with cardiovascular disease, and horses with chronic lung disease.

Results

• Findings from the RCG and ECG were then used to determine the ratio of cardiopulmonary blood volume to stroke volume, referred to as the cardiopulmonary flow index (CPFI).
• The average CPFI was calculated for each category of horses. The mean values were 7.0 for Thoroughbreds in training, 7.3 for showjumpers in training, 6.7 for horses not in training, 9.8 for horses with cardiovascular disease, and 6.2 for horses with chronic lung disease.
• Notably, the CPFI was significantly higher in horses with heart disease compared to the other four categories, with a mean value of 9.8.

Conclusion

• The researchers concluded that the CPFI is a consistent physiological parameter in horses and an increase of this value indicates heart disease.
• Therefore, this newly developed method can be applied to measure cardiac function in horses and potentially identify heart disease. The results suggest that the CPFI could be a suitable and objective index for cardiac function.