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Effects of a lack of aortic "Windkessel" properties on the left ventricle
Insights
Synthetic grafts excluding the aortic arch cause significant hemodynamic changes, leading to left ventricular hypertrophy and potential heart failure due to lost aortic compliance.
Area of Science:
- Cardiovascular Surgery
- Biomedical Engineering
- Hemodynamics
Background:
- Conventional synthetic vascular grafts used for long bypass between the ascending and abdominal aorta can exclude the aortic arch.
- This surgical approach may lead to significant alterations in cardiovascular function.
Observation:
- Post-surgery, patients exhibit systolic hypertension, decreased diastolic pressure, and widened pulse pressure.
- The phase difference between aortic flow and pressure waves approaches zero.
- These changes indicate a loss of the aortic root's natural compliance (Windkessel properties).
Findings:
- Elevated afterload and pulse pressure increase left ventricular external work and wall stress.
- Concentric left ventricular hypertrophy develops as a compensatory mechanism.
- Reduced diastolic pressure at the aortic root may compromise coronary blood flow, leading to ischemia.
Implications:
- The loss of aortic compliance is a critical factor in post-operative cardiovascular complications.
- This can result in left ventricular ischemia and potentially fatal heart failure.
- Alternative surgical strategies or graft materials may be needed to preserve aortic function.
Abstract:
After the long bypass grafting between ascending and abdominal aorta with exclusion of the aortic arch using conventional synthetic vascular graft, a considerably remarkable hemodynamic change and progressive hypertrophy of the left ventricle occurred until stabilized. In the clinical cases and animal experiments, systolic hypertension, diastolic pressure decrease and consequent pulse pressure widening were observed. Furthermore, the phase difference between flow and pressure waves approximated to zero. Elevation of the afterload due to systolic hypertension and widening of pulse pressure may result in energy loss in vascular pulsation, not maintaining forward flow but increasing the left ventricular external work. Furthermore, as the peak flow approximates the peak pressure and its point situated relatively early in systole, external work and wall stress of the left ventricle are markedly elevated. All those factors mentioned above lead concentric hypertrophy of the left ventricle to normalize the wall stress. Fall in the diastolic pressure at the aortic root may decrease coronary flow to lead ischemia of the hypertrophied left ventricle. This can occasionally lead to fatal heart failure after a long postoperative period. It may be concluded that these new findings are produced by a loss of compliance (Windkessel properties) in aortic root which occurred as consequence of using conventional synthetic vascular graft with exclusion of aortic arch.