A guide catheter shaft is formed from an inner tube structure and a multilayer sheath around the inner tube structure. The multilayer sheath includes an intermediate sheath and a shrink tube layer. The intermediate sheath is disposed around the inner tube and realized from a melt-processible first polyether-block amide material. The shrink tube layer is disposed around the intermediate sheath and realized from a different second polyether-block amide (e.g. a cross-linked polyether-block amide material) having a shrink temperature range greater than a melt temperature range of the first polyether-block amide material. The resulting structure is heated at a temperature within the shrink temperature range such that the outer shrink tube layer shrinks and the intermediate layer melts to thereby bond the multilayer sheath to the inner tube.