[The effect of respiratory activity on the QRS complex in the ECG in clinically healthy horses and horses with chronic lung diseases].

The research explores the influence of breathing activity on the QRS complex of electrocardiograms (ECG) in both healthy horses and those with chronic lung diseases. The study suggests that there are changes in the R-vector amplitudes during breathing, which can be crucial when assessing the health status, particularly in horses with respiratory diseases.

Overview of the Study

• The research investigates the interrelation between respiratory activity and changes in the QRS complex of an electrocardiogram in horses, particularly focusing on the amplitude of the R-vector and its components, Rx and Ry.
• The researchers observed that the amplitude of these waveforms decreases during the inhalation process and increases during exhalation.
• These fluctuations indicate that the R-waves in the leads from front to back (y, II, aVF) and right to left (I) decrease in size during inhalation and increase during exhalation.

Significance of the Research Findings

• These variations in the amplitudes are important, especially in horses experiencing respiratory issues. These alterations should, therefore, be considered when evaluating electrocardiograms of such horses.
• The research, however, notes that there is no need to draw respiratory curves in their study.
• In instances of differences in the R-amplitudes, it is recommended to examine the heart-cycle with the largest R-wave, typically occurring during exhalation.

Potential Cause of the Amplitude Variations

• The researchers suggest that the amount of pulmonary air content could be a possible reason for these amplitude changes, although this hypothesis would need further investigation to confirm.