No living human being can materially transcend the space-time manifold of even this universe to access other physical dimensions transcending length, width, height, and time that may be part of the fabric of this universe which are postulated to be infinitesimal curled up dimensions in any event and offer no access to multiverse dimensionality even one could. Dead end.
And even if a physical multiverse exists (which is presently esoteric mathematical theory sans-scientific evidence), no living human being can materially transcend the space time manifold of this universe to access other physical universes and even if they could (which they cannot), no person has the power to manipulate other physical universes to cause their own healing through physical or mental processes.
That said, because a person possesses a spiritual component and reality exists in the form of spiritual dimensions beyond this physical universe, this opens up two possibilities. The first is good and the second is evil.
First the good. Through prayer we can cross the space-time manifold of the cosmos and converse with God in His extradimensional realm(s). Because prayer is extra-dimensional in its reach, it must be considered the most powerful capacity God has made available to us in our current dimensional context.
This allows us to initiate communication with God who can heal us, if He so chooses to, because God exists outside of this universe and it's material limitations and laws yet has the power to interact with us and manipulate matter on a micro level.
For genuine Christians, those of us who invite God's Spirit to live in the core of our spiritual being and to express Christ through us-body, soul, and spirit; we become linked forever with God. We experience a change as dramatic as birth, and it is called a spiritual birth.
God's character and capacities become available to us as never before, despite the necessary limits of our physical context. God can actually endow genuine Christians with the "gift" of healing in this manner (though it is God Himself who actually heals through the person he has endowed with the gift of healing). For more information, read the Holy Bible.
Now for the evil second possibility which is the world of the occult in which spiritual beings (e.g. demons/fallen angels) who rebelled against God led by the most powerful called Lucifer, or Satan (among other designations) exercise limited power and a penchant for deceiving people to reject or distort God's authority and purposes and draw attention away from God and the historic Christian gospel and God's kingdom.
One tactic is through occultic psychic healing which results in demonic oppression and depression that impacts lives for years after it occurs ending only with a genuine commitment to Jesus Christ. The world of the occult is strictly prohibited in scripture and leads only to spiritual bondage and deception. For more information, read 'The Kingdom of the Occult' by Dr. Walter Martin.