Individuals who have undergone limb amputations, whether due to trauma, disease, or other medical reasons, face an increased risk of cardiovascular complications and mortality. A recent study used a detailed computer simulation model to investigate the intrinsic biomechanical changes in the arterial system following different levels of limb amputation, and how these changes can impact arterial stiffness, blood pressure, and blood flow patterns. The findings provide valuable insights into the potential mechanisms behind the heightened cardiovascular risk observed in this patient population. Cardiovascular disease is a leading cause of death worldwide, and understanding how alterations in the arterial network can contribute to this risk is crucial for developing effective preventive and management strategies.
The Impact of Limb Amputation on the Arterial System
Subjects with amputations of the lower limbs are known to have a higher risk of cardiovascular mortality and morbidity compared to the general population. However, the underlying mechanisms behind this increased risk have not been fully understood. While factors like physical inactivity, metabolic disorders, and psychological stress can play a role, the direct biomechanical changes in the arterial system resulting from limb loss may also contribute significantly to the heightened cardiovascular risk.
To investigate this, the researchers used a sophisticated computer simulation model that represented the detailed anatomy and function of the human arterial tree. They simulated different scenarios, including a healthy control, unilateral (single) lower limb amputation, bilateral (double) lower limb amputation, trilateral (triple) limb amputation, and quadrilateral (all four limbs) amputation.
Increased Arterial Stiffness and Blood Pressure
The study found that as the severity of amputation increased, there was a corresponding increase in the pulse wave velocity (PWV) – a measure of arterial stiffness – in the medium and smaller-sized arteries. This was the case even though the aortic stiffness (the largest artery) did not change significantly.
The researchers also observed that despite a decrease in cardiac output (the volume of blood pumped by the heart), the systolic and diastolic blood pressures increased across all arterial sites. This led to a rise in both central (aortic) and peripheral (brachial) pulse pressures, but with a reduction in the normal amplification of pulse pressure from the aorta to the periphery.
Altered Blood Flow and Wave Reflections
The study further revealed that the most significant increases in peak systolic pressure and decreases in peak systolic blood flow occurred in the abdominal aorta. Wave separation analysis showed no changes in the shape of the forward and backward pressure wave components, but wave intensity analysis indicated an increase in the peak forward wave intensity and a rise in the inverse peak of the backward wave intensity with more extensive amputations.
These findings suggest that the biomechanical alterations in the arterial network geometry due to limb amputations can lead to changes in the hemodynamic load on the heart, which may interact with other biological risk factors to increase the overall cardiovascular risk in this patient population.
Potential Mechanisms and Implications
The increase in arterial stiffness, particularly in the medium and smaller arteries, is likely due to the pressure- and area-dependent nature of arterial compliance. As blood pressure rises in response to limb loss, the arteries become stiffer, leading to further increases in blood pressure and pulse pressure. This, in turn, can contribute to the heightened risk of hypertension, atherosclerosis, and other cardiovascular complications observed in individuals with limb amputations.
The more pronounced changes in the abdominal aorta, including the increase in systolic pressure and decrease in blood flow, may also help explain the increased risk of Click Here
