Inclusion Criteria:

• 1. Age 18 or above, or above legal age and willing and capable of giving informed consent specific to national law
• 2. Scheduled for standard of care catheter-based endocardial mapping for atrial or ventricular tachyarrhythmias using a commercial Rhythmia Mapping System.

Exclusion Criteria:

• 1. Prothrombotic or bleeding tendency due to coagulopathy or blood dyscrasia
• 2. Inability to tolerate heparin therapy (e.g. heparin induced thrombocytopenia, allergy, etc.)
• 3. Prosthetic or stenotic valves in the chamber where the intended mapping will occur, or in the path of the catheter access route
• 4. Active systemic infection or sepsis
• 5. Hemodynamic instability or shock at baseline precluding ablation in the assessment of the investigator.
• 6. Presence of intracardiac thrombus, tumor, or other abnormality which precludes catheter introduction
• 7. Women who are pregnant or lactating
• 8. Cardiac surgery within the past 90 days
• 9. Acute myocardial infarction within 3 months
• 10. Stable/unstable angina or ongoing myocardial ischemia
• 11. Subjects with an active heart failure decompensation
• 12. Long QT Syndrome, Brugada Syndrome, or Torsade de Pointes
• 13. Congenital heart disease with or without corrective surgery that would complicate a mapping procedure
• 14. Subjects having untreatable allergy to contrast media
• 15. Vascular pathology or tortuosity precluding standard vascular access techniques
• 16. Subjects who are currently enrolled in another investigational study or registry that would directly interfere with the current study, except when the patient is participating in a mandatory governmental registry, or a purely observational registry with no associated treatments. Each instance should be brought to the attention of the sponsor to determine eligibility.