Effect of cardiac arrhythmia on left ventricular and aortic blood pressure parameters in the horse.

The research examines the effects of cardiac arrhythmia on a horse’s left ventricular and aortic blood pressure parameters. It was observed that changes in left ventricular and aortic pulse contours correlated with varying pulse intervals. The study utilized a regression model for analyzing the relationships of various variables derived from these contours.

Study Details and Methodology

• The study was conducted on seven horses that displayed varying kinds of supraventricular arrhythmia.
• By using catheter mounted transducers, the researchers recorded transaortic blood pressures.
• An important part of the methodology was the analysis of the left ventricular (LV) and aortic (Ao) pulse contours in relation to pulse interval (PI).
• For determining the interconnectedness of different variables derived from these LV and Ao contours, the researchers employed stepwise linear regression.

Key Findings

• The research found changes in the LV and Ao pulse contours to be linked to PI variations.
• It was observed that when PI lengthened, there was a rise in LV end diastolic pressure (LVEDP) due to an extended filling time, while an extended PI resulted in reduced end diastolic Ao pressure (AoEDP) due to a prolonged arterial ‘run off’.
• Investigators found that the peak rate of pressure rise during the isovolumic contraction period was not consistently influenced by changes in PI.
• The research demonstrated a direct relation of Peak LV pressure (LVPp) with AoEDP in all the horses and with LVEDP in some horses. Ao systolic pulse pressure (SPP) was directly related to LVEDP and inversely related to AoEDP in some cases.
• Neither LVPp nor SPP showed a consistent relationship with LVdP/dt max. The peak positive gradient between LV and Ao pressures was inversely associated with AoEDP and directly associated with LVEDP and LVdP/dt max in some instances.
• AodP/dt max, the peak rate of rise of the Ao pressure contour during ejection, presented an inverse relationship with AoEDP in all horses and a direct relationship with LVEDP in some. However, its relationship with LVdP/dt max was mixed.
• The peak rate of fall of the LV pressure contour during relaxation was directly related to LVPp in most horses.