Intraventricular pressure gradients throughout the cardiac cycle: effects of ischaemia and modulation by afterload

New Findings • What is the central question of this study? The aim of the present study was to characterize the intraventricular pressure gradients (IVPGs) along the cardiac cycle, to correlate them with myocardial segmental asynchrony and to evaluate their response to regional myocardial ischaemia and ventricular afterload. • What is the main finding and its importance? We showed the existence of diastolic and systolic IVPGs in the left ventricle (LV) and demonstrated for the first time that normal gradient pattern is related to physiological asynchrony between basal and apical myocardial segments. Moreover, we showed that IVPG, a marker of normal left ventricular function, can be attenuated, lost entirely, or even reversed after regional acute ischaemia and afterload elevations. The aim of the present study was to characterize the intraventricular pressure gradients (IVPGs) througout the cardiac cycle, to correlate them with myocardial segmental asynchrony and to evaluate the effects of ischaemia and modulation by afterload. Open‐chest anaesthetized rabbits (n= 6) were instrumented with pressure‐tip micromanometers placed in the apex and outflow tract of the left ventricular (LV) cavity and with sonomicrometer crystals placed in the apex and base of the LV free wall to measure IVPGs and myocardial segment length changes during basal, afterloaded (aortic cross‐clamping) and ischaemic conditions (left anterior descending coronary artery ligation). During early diastole (rapid filling), we recorded an IVPG (4.6 ± 0.7 mmHg) from the cardiac base towards the apex followed by an apex‐to‐outflow pressure gradient (3.6 ± 0.2 mmHg). During systole, we recorded an IVPG (0.6 ± 0.1 mmHg) from apex to outflow during early rapid ejection, which inverted during late slow ejection. Interestingly, the maximal rate of LV pressure fall occurred earlier and relaxation rate was faster in the base than in the apex. While shortening of basal segments was complete at the end of ejection, apical segments always showed a significant amount of postsystolic shortening. The IVPGs were entirely lost during ischaemia and attenuated by afterload elevations. During ischaemia, systolic shortening of the apical segment decreased, while postsystolic shortening increased. The present study confirms the existence of diastolic and systolic IVPGs in the LV and demonstrates, for the first time, that this normal gradient pattern is related to physiological asynchrony between basal and apical m