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Increased pulmonary vascular resistance (PVR) can occur due to several mechanisms, but one of the most significant contributors is hypoxia-induced vasoconstriction. This refers to the physiological response of pulmonary arteries to low oxygen levels, where the blood vessels constrict in order to redirect blood flow away from poorly ventilated areas of the lung. This mechanism helps to optimize ventilation-perfusion matching but leads to an overall increase in PVR when widespread hypoxia is present, as is often seen in conditions such as chronic obstructive pulmonary disease (COPD) or high altitude exposure.

Other pathologies like left to right shunts and congenital heart disease typically decrease pulmonary vascular resistance in the short term by increasing pulmonary blood flow. In these conditions, blood that would normally circulate systemic pathways is redirected into the pulmonary circulation, often resulting in lower resistance due to sheer volume and the resultant alterations in vascular dynamics.

Liver cirrhosis, while affecting hemodynamics, primarily impacts systemic vascular resistance and portal circulation rather than directly influencing PVR in a significant manner. Hence, hypoxia-induced vasoconstriction stands out as a clear association with increased PVR due to the direct physiological response of pulmonary vasculature to low oxygen levels.