- Diagnosis of Group 1 or Group 4 PAH based on PAPm > 25 mmHg, PAWP <15 mmHg, PVR >3 WU and consistent clinical history. Note: for logistical reasons, patients at high suspicion for Group 1 or Group 4 PAH will sign informed consent to have the NICOM device applied during right heart catheterization before the procedure; if it is found that the patient does not meet the definition of Group 1 or Group 4 PAH during right heart catheterization, he/she will be excluded.