A catheter system to record and map electrical signals by cardiac tissues before, during, and/or after the treatment of cardiac arrhythmias in a group of patients. The system can include an elongated body; a distal electrode assembly comprising a proximal stem, a plurality of spines emanating from the stem; and a plurality of nonconductive spine covers, each surrounding a respective spine. Each spine can cover one or more tensile members of the respective spine cover. The system can be configured to achieve clinically improved performance and safety of catheter configurations as to accessibility into target areas of a beating heart.