Medical device and treatment method

A treatment method, the method comprising:

• expanding a through-hole formed in an atrial septum so as to allow a right atrium and a left atrium of a heart failure patient to communicate with each other;
• confirming hemodynamics of blood flow in a vicinity of the through-hole;
• and
• performing maintenance treatment for maintaining a size of the through-hole with a medical device comprising a shaft portion, an expandable and contractible expansion body disposed distal of the shaft portion, the expansion body including a plurality of linear expansion portions disposed at different positions in a circumferential direction of the shaft portion, each of the plurality of linear expansion portions including a concave portion recessed in a direction intersecting with an axial direction of the shaft portion, and a maintenance treatment element disposed in each of the linear expansion portions.

A treatment method, the method comprising:

• expanding a through-hole formed in an atrial septum in a first expansion process to allow a right atrium and a left atrium of a heart failure patient to communicate with each other;
• expanding the through-hole more than in the first expansion process in a second expansion process;
• and
• performing maintenance treatment for maintaining the through-hole with respect to the through-hole after the second expansion process with a medical device comprising a shaft portion, an expandable and contractible expansion body disposed distal of the shaft portion, the expansion body including a plurality of linear expansion portions disposed at different positions in a circumferential direction of the shaft portion, each of the plurality of linear expansion portions including a concave portion recessed in a direction intersecting with an axial direction of the shaft portion, and a maintenance treatment element disposed in each of the linear expansion portions.