A cryoablation catheter assembly comprising: a catheter having a distal portion, a proximal portion, and a longitudinal length, the catheter configured and arranged for insertion into patient vasculature, the catheter comprising a body and defining at least one coolant outtake region extending along at least a portion of the catheter; a guide tube at least partially disposed in the catheter; a coolant transfer tube at least partially disposed in the catheter, wherein the coolant transfer tube is configured and arranged to receive and transfer coolant from a coolant source to a distal end of the coolant transfer tube; an expansion element coupled to the distal portion of the body of the catheter, the expansion element comprising an outer layer disposed over an inner layer such that the expansion element defines an inter-expansion-element space between the inner layer and the outer layer and an intra-expansion-element space within the inner layer, the intra-expansion-element space in fluid communication with the at least one coolant outtake region and the distal end of the coolant transfer tube; wherein the inter-expansion-element space is in fluid communication with a fluid pathway, the fluid pathway configured and arranged to transfer fluids from the inter-expansion-element space to a fluid-drawing source; and characterised by a pressure regulation system disposed along the fluid pathway, the pressure regulation system configured and arranged to passively regulate the pressure in the inter-expansion-element space using two or more check valves, wherein the pressure regulation system defines a first region and a second region fluidly separated from one another by a first check valve, and wherein a second check valve fluidly separates the first region from a region external to the catheter; wherein the first region includes the inter-expansion-element space and the second region includes the fluid-drawing source. a catheter having a distal portion, a proximal portion, and a longitudinal length, the catheter configured and arranged for insertion into patient vasculature, the catheter comprising a body and defining at least one coolant outtake region extending along at least a portion of the catheter; a guide tube at least partially disposed in the catheter; a coolant transfer tube at least partially disposed in the catheter, wherein the coolant transfer tube is configured and arranged to receive and transfer coolant from a coolant source to a distal end of the coolant transfer tube; an expansion element coupled to the distal portion of the body of the catheter, the expansion element comprising an outer layer disposed over an inner layer such that the expansion element defines an inter-expansion-element space between the inner layer and the outer layer and an intra-expansion-element space within the inner layer, the intra-expansion-element space in fluid communication with the at least one coolant outtake region and the distal end of the coolant transfer tube; wherein the inter-expansion-element space is in fluid communication with a fluid pathway, the fluid pathway configured and arranged to transfer fluids from the inter-expansion-element space to a fluid-drawing source; and characterised by a pressure regulation system disposed along the fluid pathway, the pressure regulation system configured and arranged to passively regulate the pressure in the inter-expansion-element space using two or more check valves, wherein the pressure regulation system defines a first region and a second region fluidly separated from one another by a first check valve, and wherein a second check valve fluidly separates the first region from a region external to the catheter; wherein the first region includes the inter-expansion-element space and the second region includes the fluid-drawing source.