Background: For patients with chronic thromboembolic pulmonary hypertension (CTEPIII) and tricuspid regurgitation (TR) undergoing pulmonary thromboendarterectomy (PTE), whether concomitant tricuspid annuloplasty should be carried out is still controversial. Methods: The study population consisted of 45 consecutive patients with CTEPH who were scheduled to undergo PTE. All PTE surgeries were conducted with a median sternotomy and deep hypothermia circulatory arrest (DHCA). We collected and analyzed the demographics, surgical details, echocardiographic parameters, and right heart catheterization (RHC) results of these patients. Results: Moderate to severe TR was documented in 48.9% (22/45) of the patients pre-operatively and 4.4% (2/45) of the patients post-operatively. In patients with grade 4 TR, severity decreased to grade 2 in 8 and to grade 1 in 1. In patients with grade 3 TR, severity decreased to grade 2 in 9, to grade 1 in 3, and 1 remained unchanged. In patients with grade 2 TR, severity decreased to grade 1 in 8, and 15 remained unchanged. The post-operative TR velocity was decreased significantly (431.9 +/- 53.4 vs. 196.5 +/- 154.0, P<0.001). Pulmonary artery systolic pressure was 84 +/- 17 mmHg pre-operatively and decreased to 38 +/- 14 mmHg post-operatively (P<0.001). The pre and post-operative pulmonary diastolic pressure was 29 +/- 9 and 17 +/- 7 mmllg, respectively (P<0.001). The pre and post-operative mean pulmonary pressure was 48 +/- 10 and 24 +/- 9 mmHg, respectively (P<0.001). The pulmonary vascular resistance (PVR) (1,025.4 +/- 465.0 vs. 476.6 +/- 181.2 dynes.sec.cm(-5) , P<0.001) and pulmonary artery wedge pressure (PAWP) (9 +/- 4 vs. 5 +/- 2 mmHg, P<0.001) decreased significantly after operation. The cardiac index (CI) increased significantly (1.9 +/- 0.5 vs. 2.3 +/- 0.4, P=0.003) after operation. Conclusions: In conclusion, functional TR could be alleviated after PTE even in patients with high PVR. However, the long-term results need to be further investigated.