If the ABI's on the right is 0.4 and the left is 0.5, with plethysmographic waveforms demonstrating normal amplitude and no dicrotic notch, what does this suggest?

The ankle-brachial index (ABI) values indicate the presence and severity of peripheral artery disease. An ABI of 0.4 and 0.5 suggests that there is significant arterial impairment, as normal ABI values typically range from 1.0 to 1.4. Values below 0.9 indicate varying degrees of arterial narrowing or obstruction.

In this scenario, the presence of normal amplitude in the plethysmographic waveforms alongside the lack of a dicrotic notch reinforces the understanding of collateral circulation development. In patients with significant arterial disease (as suggested by the low ABI values), the body may create collateral vessels to reroute blood flow, which can help maintain perfusion to distal tissues even when the primary artery is compromised. The absence of the dicrotic notch often indicates that the waveforms are being influenced by lower perfusion pressures typical in conditions of severe arterial obstruction.

Thus, the combination of low ABIs and plethysmographic findings indicates severe disease with collateral development, confirming that while there is significant compromise in arterial function, the body is adapting to maintain adequate blood flow through collateral pathways. This understanding of hemodynamics is crucial in assessing vascular health and guiding treatment options.