A balloon catheter includes a shaft, a balloon made of an expandable membrane, a flexible substrate, one or more electrodes, and one or more radiopaque flags. The shaft is configured for insertion into a heart of a patient. The balloon is fitted at a distal end of the shaft. The flexible substrate is disposed on the membrane. The one or more electrodes are disposed over the flexible substrate and have a fishbone configuration. The one or more radiopaque flags are coupled to the expandable membrane, wherein the one or more radiopaque flags include a serpentine pattern so that the radiopaque flags fold in conformance with flexible substrate as the expandable membrane is collapsed into a compressed or folded configuration.
