Computer processing of transaortic valve blood pressures in the horse using the first derivative of the left ventricular pressure trace.

The research describes a new technique to analyze heart pressures in horses using computer processing. This method focuses on the pressures within the heart’s left ventricle to determine the start and end of each heart cycle, and evaluate aspects such as contraction time and pulse interval.

Methodology

• The researchers proposed a new way to process transaortic valve pressures in horses, focusing on the first derivative of the left ventricular pressure to signify the start and end of each systolic complex (the phase of the heartbeat when the heart muscle contracts).
• Three different left ventricular end-diastolic pressure (LVEDP) definitions were evaluated to determine the start of each systolic cycle, based on a 100, 150, or 200 mmHg/sec rate of left ventricular diastolic pressure rise.
• The effectiveness of these definitions to determine isovolumic contraction time (the brief period during early systole where the heart contracts with no corresponding volume change) and pulse interval were also evaluated.

Results

• Among the three definitions, LVEDP 150 was determined to be the best. It was defined as the last point in diastole (the phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood) before a sustained rate of rise of left ventricular pressure (LVdP/dt) equal to or exceeding 150 mmHg/sec over 44 milliseconds.
• The end of left ventricular ejection (the phase of the heartbeat when blood is pumped out of the ventricles and into the aorta and pulmonary arteries) was estimated from the left ventricular pressure trace as the point at which negative LVdP/dtmax occurred.
• There was strong agreement between the values of left ventricular ejection time (LVET) measured to the incisura (notch or recess) of the aortic pressure trace and LVET calculated to the time of negative LVdP/dtmax, with a correlation coefficient of 0.991 suggesting a nearly perfect positive linear relationship between the two measurements.

Conclusion

• The study emphasizes the importance of visually inspecting the heart pressure waveforms before subjecting them to automatic processing. This is crucial for validating the output of the computerized method and ensuring that it accurately reflects the observed physiological phenomena.