this invention discusses a device for treating of diseased , blocked , occluded or stenotic lumens in the body , typically blood vessels including both arteries and veins , and more typically coronary and peripheral arteries . this device dilates occluded vessels while causing minimal trauma to the lesion thus minimizing the risk of dissections , total occlusion , abrupt closure and restenosis , and promotes faster healing . a constraining structure ( cs ) is placed over a balloon catheter where upon inflation both the balloon and the cs increase in diameter and during deflation the cs returns to its original dimensions . the cs can have multiple designs intended to expand to a diameter smaller than the maximal inflated diameter of the balloon . the cs can be connected to the balloon either on the distal side or the proximal side or both . it can also float over the balloon without firm attachment using simple covers since the cs can be designed to maintain its length during expansion and therefore there is no relative axial movement between the cs and the balloon . it can be made from various materials , processes and designs . it can be made from metal , preferable a very elastic metal such as nitinol and it can be made from variety of polymers ( e . g . nylon ). it can be constructed from wires or laser cut from a tube , sheath or other forms of materials . in a preferred embodiment of this invention the cs is over the balloon . during inflation the cs expands allowing the balloon to expand under it . the maximum cs diameter is smaller than that of the inflated balloon , thus the balloon protrudes and expands through the cs creating a topography of hills and valleys . the cs structure creates a combination of a designed topography and controlled , slower inflation promoting a process of plaque remodeling . the plaque in the diseased area of the vessel is able to flow through the valleys in the designed topography , and re - distribute in the vessel allowing a gradual inflation without the need to apply added pressure . referring to fig4 a to 4c , in a conventional balloon during inflation , due to balloon compliance , the balloon will expand toward areas of less resistance ( healthy areas or areas with less plaque buildup — see fig4 b ). in order to successfully dilate the lesion additional pressure should be applied until the lesion areas with more severe blockage yields and the balloon can inflate entirely ( see fig4 c ). this process is abrupt and aggressive exposing vessel wall ( healthy or diseased areas ) to severe trauma and may result in dissection , restenosis and a slower healing process . the topography created by the cs allows for the plaque to gradually re - disperse and flow through the cs valleys ( see fig2 a and 2b ) while the catheter expands and the inflation is gradual and controlled . the design of the cs allows for plaque remodeling creating less trauma and promotes faster healing . in one embodiment of this invention , the cs is attached to both ends of the balloon and is capable of maintaining a constant length during inflation and deflation processes . during inflation the cs structure expands to a pre - designed diameter that is smaller than the balloon inflated diameter . the balloon continues to expand beyond the cs but is restricted in length by the cs structure . referring to fig2 b , the balloon inflates through the cs structure and is restricted in length by the cs design , thus allowing the device to be inflated without balloon lengthening ( common in conventional balloons ) thus reducing or eliminating axial forces applied on vessel wall and minimizing trauma to vessel . furthermore this allows more predictability in inflation process . this is especially effective in long balloons ( commonly used in peripheral arteries ). in one embodiment of this invention the cs is constructed of radial rings connecting by axial wires . upon inflation the cs expands radially without any axial lengthening . this structure allows a compartmental inflation process where the rings create separate inflation zones within the vessel . therefore the pressure to the vessel wall is controlled and is applied in the radial direction without any strain in the axial direction reducing trauma and possible dissections . the present invention can be utilized to deliver various agents or active substances particularly ( but not limited to ) those suitable for treating vascular and other luminal conditions such as antiproliferative and antimitotic agents ( such as paclitaxel and sirolimus ) other substances can include antibiotics , antiplatelet agents hormones and more . the active substance can be placed in various designs or techniques such as directly coated on the balloon surface , the cs or both . it can be embedded in a matrix / carrier placed on the balloon or the cs or both . the combination of low trauma dilatation with release of active agent can be superior to drug eluting stents for some portions of the population by minimizing the need for a permanent implant yet providing good long term results . in one embodiment the balloon surface is coated with drug . upon balloon inflation , the ‘ pillows ’/ hills formed in the balloon external surface coated with drug engage the vessel wall and compress the drug into the wall to facilitate efficient drug delivery to the treated site . drug delivery can be facilitated using many different design methods including but not limited to coating the balloon , coating the cs structure or both . coating with a drug directly or using a carrier in a form of a matrix or microcapsules .
a constraining structure for use with a balloon catheter includes multiple longitudinal struts and multiple expandable radial rings . the constraining structure can expand radially but may not expand substantially in the longitudinal direction . the constraining structure can have multiple compartments configured to expand independently of one another . inflating the balloon catheter within the constraining structure can allow for dilation of the blood vessel in a predetermined topography .