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Noninvasive evaluation of left ventricular afterload: part 1: pressure and flow measurements and basic principles of
Julio A Chirinos1, Patrick Segers
1Department of Medicine, Philadelphia Veterans' Affairs Medical Center-University of Pennsylvania, Philadelphia, Pa, USA. julio.chirinos@uphs.upenn.edu
Insights
Left ventricular afterload is best understood through pressure-flow relations, not just pressure alone. Noninvasive techniques and biomechanical models offer insights into cardiovascular function and disease.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
Background:
- Left ventricular afterload significantly impacts cardiovascular function, both normal and abnormal.
- Afterload is a complex, dynamic process influenced by pressure and flow, not a single metric.
- Understanding afterload is crucial for diagnosing cardiovascular diseases and evaluating treatments.
Purpose of the Study:
- To review noninvasive methods for measuring central pressure and flow.
- To explain the concepts of wave conduction and reflection in central pressure-flow relations.
- To guide researchers and clinicians in applying and interpreting afterload analyses.
Main Methods:
- Utilizing high-fidelity arterial applanation tonometry for noninvasive central pressure measurement.
- Employing Doppler echocardiography and phase-contrast MRI for accurate aortic flow assessment.
- Applying simplified biomechanical models to analyze central pressure and flow data.
Main Results:
- Central pressure and flow data can be analyzed using biomechanical models to characterize afterload components.
- Noninvasive techniques provide accurate assessments of pressure and flow dynamics.
- These methods offer mechanistic insights into hemodynamics and cardiovascular disease.
Conclusions:
- Left ventricular afterload is best characterized by pressure-flow relationships.
- Noninvasive measurements combined with biomechanical modeling enhance understanding of cardiovascular hemodynamics.
- This approach aids in clinical and epidemiological settings for cardiovascular disease research.
Abstract:
The mechanical load imposed by the systemic circulation to the left ventricle is an important determinant of normal and abnormal cardiovascular function. Left ventricular afterload is determined by complex time-varying phenomena, which affect pressure and flow patterns generated by the pumping ventricle and cannot be expressed as a single numeric measure or described in terms of pressure alone. Left ventricular afterload is best described in terms of pressure-flow relations. High-fidelity arterial applanation tonometry can be used to record time-resolved central pressure noninvasively, whereas contemporary noninvasive imaging techniques, such as Doppler echocardiography and phase-contrast MRI, allow for accurate assessments of aortic flow. Central pressure and flow can be analyzed using simplified biomechanical models to characterize various components of afterload, with great potential for mechanistic understanding of the role of central hemodynamics in cardiovascular disease and the effects of therapeutic interventions. In the first part of this tutorial, we review noninvasive techniques for central pressure and flow measurements and basic concepts of wave conduction and reflection as they relate to the interpretation of central pressure-flow relations. Conceptual descriptions of various models and methods are emphasized over mathematical ones. Our review is aimed at helping researchers and clinicians apply and interpret results obtained from analyses of left ventricular afterload in clinical and epidemiological settings.
