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Rationale, design and methodology for Intraventricular Pressure Gradients Study: a novel approach for ventricular
Miguel Guerra1, Mário J Amorim, João C Mota
1Faculty of Medicine of University of Oporto, Department of Physiology, Alameda Professor Hernâni Monteiro, Porto, Portugal.
Insights
Systolic and diastolic intraventricular pressure gradients, indicating normal heart function, may change with impaired cardiac conditions like ischemia or aortic stenosis. This study investigates these pressure gradients in animal and patient models.
Area of Science:
- Cardiovascular Physiology
- Cardiac Mechanics
- Hemodynamics
Background:
- Intraventricular pressure gradients (IVPGs) between the left ventricle base and apex are known during diastolic filling and improve with systolic/diastolic function.
- Systolic IVPGs have been observed, but their role in cardiac dysfunction remains unclear.
- Segmental dysfunction may alter physiological IVPGs, suggesting a link to myocardial asynchrony.
Purpose of the Study:
- To investigate the modulation of systolic and diastolic intraventricular pressure gradients during cardiac dysfunction.
- To test the hypothesis that IVPGs are related to physiological asynchrony and are altered by ischemia or aortic stenosis.
- To validate a method for measuring IVPGs in animal and patient studies.
Main Methods:
- Animal studies involved instrumenting rabbits to measure pressure gradients and myocardial segment lengthening under basal, afterloaded, and ischemic conditions.
- Ischemia was induced via left coronary artery ligation, and afterload was increased by aortic narrowing/occlusion.
- Patient studies included 12 adults (65-80 years) with severe aortic stenosis undergoing aortic valve replacement, measuring pressure gradients pre- and post-procedure using a pressure-volume catheter.
Main Results:
- The study aims to validate the measurement methodology for IVPGs in both animal and patient cohorts.
- Expected findings include demonstrating how IVPGs change with altered cardiac conditions.
- The research anticipates correlating IVPGs with ventricular relaxation, filling dynamics, and systolic function.
Conclusions:
- The study expects to validate a novel method for obtaining intraventricular pressure gradients.
- This methodology will enhance understanding of ventricular relaxation and filling.
- Findings will correlate pressure gradients with systolic function, offering insights into cardiac health and disease.
Background:
Intraventricular pressure gradients have been described between the base and the apex of the left ventricle during early diastolic ventricular filling, as well as, their increase after systolic and diastolic function improvement. Although, systolic gradients have also been observed, data are lacking on their magnitude and modulation during cardiac dysfunction. Furthermore, we know that segmental dysfunction interferes with the normal sequence of regional contraction and might be expected to alter the physiological intraventricular pressure gradients. The study hypothesis is that systolic and diastolic gradients, a marker of normal left ventricular function, may be related to physiological asynchrony between basal and apical myocardial segments and they can be attenuated, lost entirely, or even reversed when ventricular filling/emptying is impaired by regional acute ischemia or severe aortic stenosis.
Methods/Design:
Animal Studies: Six rabbits will be completely instrumented to measuring apex to outflow-tract pressure gradient and apical and basal myocardial segments lengthening changes at basal, afterloaded and ischemic conditions. Afterload increase will be performed by abruptly narrowing or occluding the ascending aorta during the diastole and myocardial ischemia will be induced by left coronary artery ligation, after the first diagonal branch.Patient Studies: Patients between 65-80 years old (n = 12), both genders, with severe aortic stenosis referred for aortic valve replacement will be selected as eligible subjects. A high-fidelity pressure-volume catheter will be positioned through the ascending aorta across the aortic valve to measure apical and outflow-tract pressure before and after aortic valve replacement with a bioprosthesis. Peak and average intraventricular pressure gradients will be recorded as apical minus outflow-tract pressure and calculated during all diastolic and systolic phases of cardiac cycle.
Discussion:
We expect to validate the application of our method to obtain intraventricular pressure gradients in animals and patients and to promote a methodology to better understand the ventricular relaxation and filling and their correlation with systolic function.
