An Experience on Normothermic Beating Heart Pulmonary Thromboendarterectomy

Objective: To study the outcome of normothermic beating heart pulmonary thromboendarterectomy (PTE) performed in patients with chronic pulmonary thromboembolism. Methodology: A retrospective analysis of 15 patients who underwent PTE under normothermic beating heart cardiopulmonary bypass from July 2009 to September 2018 was done. The patients were followed up with clinical assessment, transthoracic echocardiography and computerized tomographicangiography (CTA) for 1 month to 82 months. Results: Data were analysed for 15 consecutive patients. Mean age of the patients was 35.28 years and 10 patients were male. Pre-operatively 6 (40%) patients presented with New York Heart Association (NYHA) class II dyspnoea on exertion symptomatology, 7 (47%) were in NHYA class III, and 2 (13%) were in NYHA class IV. The preoperative and postoperative mean pulmonary artery pressures (mPAP) (mmHg) were 36.50 ± 11.3 and 20.21 ± 7.19, the systolic PAPs (mmHg) were 73.35 ± 14.12 and 35.21 ± 7.89 and the diastolic PAPs (mmHg) were 19.28 ± 8.60 and 12.85 ± 7.26 respectively. 2 (13%) patients had Jamieson’s type I and 12 (87%) had Jamieson type II disease. One patient (7%) expired on 9 postoperative day. All the patients had improved pulmonary gas exchange and did not require oxygen supplementation from 5 postoperative day; symptoms improved to NYHA class I & II in 12 (80%) & 3 (20%) of patients respectively. There was no reperfusion pulmonary edema or any neurologic complications. Postoperative echocardiogram showed improved right ventricular function and Computerised Tomographic Angiogram showed completeness of the procedure. Conclusion: Pulmonary thromboendarterectomy under normothermic beating heart cardiopulmonary bypass has good immediate postoperative results with significant progressive improvement in hemodynamics and quality of life during the course of follow-up. The results were not only comparable to those of the procedure done How to cite this paper: Bisoi, A.K., Ramakrishnan, P., Chauhan, S., Sahu, M.K. and Chandrasekharan, N.C. (2019) An Experience on Normothermic Beating Heart Pulmonary Thromboendarterectomy. World Journal of Cardiovascular Surgery, 9, 1-13. https://doi.org/10.4236/wjcs.2019.91001 Received: December 18, 2018 Accepted: January 28, 2019 Published: January 31, 2019 Copyright © 2019 by author(s) and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access


Introduction
Chronic thromboembolic pulmonary hypertension (CTEPH) is a debilitating condition with an incidence rate of 3.8% of all cases of pulmonary embolism [1]. CTEPH is a sequelae of single or multiple episodes of acute pulmonary embolism leading to branch pulmonary artery obstruction with incomplete resolution, fibrosis, organization and endothelisation of the thrombus [2]. This process eventually leads to increased pulmonary vascular resistance (PVR), pulmonary hypertension (PHTN) and right heart failure. In general, symptoms develop late and dyspnoea on exertion is the most frequent presenting symptom. Less commonly, exercise intolerance, pleuritic chest pain, palpitations and hemoptysis can occur [3]. Chest x-ray and electrocardiogram (ECG) can suggest features of PHTN and right ventricular hypertrophy (RVH), but are not diagnostic. Transthoracic echocardiography (TTE) is the initial diagnostic modality and computerised tomographic angiogram (CTA) is the investigation of choice nowadays for diagnosing CTEPH [4]. Next investigation which deserves mention is right heart catheterisation, which can provide hemodynamic as well as anatomic details like RV pressures, PA pressures and pulmonary vascular resistance (PVR). But our strategy is to do right heart catheterisation only in situations where there is diagnostic dilemma or there is suspicion of coronary artery disease. Pulmonary thromboendarterectomy (PTE) under deep hypothermic circulatory arrest (DHCA) is the current standard treatment. This technique has the advantage of bloodless surgical field allowing a complete removal of the thrombus from the pulmonary vascular bed up to the sublobar levels. Even though DHCA gives the advantage of good surgical field, it is associated with dangers of potential neurological complications, as well as kidney, liver and spinal cord ischemia.
To avoid the above complications of DHCA, several attempts have been made by many groups worldwide. Masuda  Location of thrombus was described by Jamieson's classification.

Surgical Technique
Following midline sternotomy and pericardiotomy, pulmonary artery pressure (PAP) was measured by direct puncture and transducing the MPA. Aortic and bicaval cannulation were done, total CPB was established, after achieving target activated clotting time (ACT) > 480 seconds. Patient was not cooled, hence normothermia was maintained and heart was beating throughout the procedure.
After making the main and branch pulmonary arteries free, an incision was made in the MPA at the level of bifurcation and extended towards right pulmonary artery (RPA). The pulmonary arteries were approached intrapericardially, bilateral pleurae were kept intact. The arteriotomy in the RPA was extended (if needed) laterally towards the lobar branch level; sump sucker was placed inside the RPA to tackle the bleed from the bronchial arteries. Another sucker was used to suck out the blood from left pulmonary artery (LPA). If there was any fresh loose thrombus, it was removed first as it could occlude the view as well as may dislodge and embolise distally. The plane of thromboendarterectomy was developed cautiously with blunt dissection and was confirmed by the pearly white appearance and the ease of separation. The plane should not go too deep which can lead to perforation of the artery and should not be too superficial which can lead to inadequate clearance of thrombus leading to persistent pulmonary hypertension. By gentle dissection, traction and counter traction, the thrombus was mobilised in the RPA, then further mobilization was done into the lobar and segmental levels by the same method of traction and counter traction. It should be made sure that, the distal most thrombus was not cut free but it was "tailed off", so that there was nothrombus left behind to avoid the distal arteriopathy. In case of difficulty in exposure, superior vena cava (SVC) could be transected so that adequate exposure of whole RPA with good exposure till lobar branch level could be attained. SVC was re-anastomosed once PTE was done by 5 -0 polypropylene suture. Now the incision in MPA was extended to LPA and thrombus was removed in the same way as described for RPA above. Successful thromboendarterectomy was assured by the brisk bright red back bleed from the distal segments. Once thrombus was removed, the arteriotomy was closed after deairing the right heart and pulmonary arteries. Now the patient was weaned off CPB and then PAP was measured. Following this, protamine was administered and routine closure was done. Patients were shifted to the cardiac surgical ICU, hemodynamic parameters were monitored and mechanical ventilation done with

Results
Data of 15 patients were analysed.  (Figure 1(a)).    arteries with no residual thrombus and Figure 2 shows the resected specimen of the pulmonary thromboendarterectomy specimen of the right pulmonary artery involving lobar, segmental and subsegmental vessels. Note the tailed ending of the thrombus distally. The postoperative results were detailed in Table 4. The mean duration of ventilation was 34.14 hours. One patient (7%) had difficulty in weaning from mechanical ventilation so underwent tracheostomy. Vasoactive Inotropic score (VIS) was calculated in the first 24 hours, the mean score was 10.91

Discussion
Pulmonary thromboendarterectomy (PTE) remains the standard treatment for CTEPH since the time it was first published by University College of San Diego in the late 1980s [10]. PTE is considered safe and the technique has evolved since it has been first performed [11]. PTE under CPB & DHCA is considered the standard technique till now because it prevents the bronchial back bleeding (caused by chronic hypoxia induced bronchial arterial hyperplasia) and helps complete removal of the thrombus from the pulmonary vascular bed [12].
DHCA, although helps in complete removal of the thrombus, but not without the dangers of potential neurological complications. It is becoming clear from many studies involving human body organ functioning, that oxygen consumption is never near zero even if the core temperature is reduced to 0˚C. This suggests that, some metabolic activity still go on irrespective of the temperature of cell, so the time limit of circulatory arrest should be accurate. Usually at a temperature of 18˚C, a safe circulatory arrest time period of 30 minutes is possible without any structural or functional derangement of brain functions [13] [14].
The temperature of brain is indirectly monitored from tympanic or nasopharyngeal temperature probes, hence this may not be so accurate. The brain pro-

Conclusion
Pulmonary thromboendarterectomy under normothermic beating heart cardiopulmonary bypass has good immediate postoperative results with significant progressive improvement in hemodynamics and quality of life during the course of follow-up. The results were not only comparable to those of the procedure done under deep hypothermic circulatory arrest by other centres but also without its associated adverse events. This technique requires more expertise but gives equivalent good results in immediate and short-to mid-term follow-up with less morbidity than the standard procedure, but it requires long term follow-up to substantiate the evidence.

Limitations
The major limitation of the study is retrospective study with small number of patients and lack of long-term follow-up.

Funds
No fund was received from anybody. World Journal of Cardiovascular Surgery treatment for CTEPH.

What Does This Study Adds?
Normothermic beating heart pulmonary thromboendarterectomy is a good alternative to that done under DHCA and also avoids the potential adverse effects of DHCA.