European Journal of Cardiovascular Medicine

Complete Pulmonary thromboendarterectomy (PTE) is the definitive treatment of Chronic thromboembolic pulmonary hypertension (CTEPH)[1], and deep hypothermic circulatory arrest(DHCA) has been the most commonly employed technique to deal with bronchial back bleed, and obtain a bloodless field. However, prolonged DHCA has many adverse effects including neurologic deficits [2,3], renal dysfunction [4,5] and coagulopathy[6]. To avoid these complications, here we present our experience and outcome of intermittent circulatory arrest for brief period of time in 3 patients with CTEPH.

Study Design

No ethical clearance was needed as this was a retrospective case series. Data from 3 patients who underwent PTE  for CTEPH between July 2021 and September 2023 in department of CTVS, IPGMER & SSKM Hospital are collected and analysed. Patients were followed up clinically and with 2D echocardiography (2D Echo) and computed tomography pulmonary angiogram (CTPA).

Inclusion criteria were patients with: 1) New york heart Association (NYHA) functional class III and IV symptoms; 2) thrombus in main, lobar or segmental pulmonary arteries(PA) as revealed in CTPA; 3) 2D Echo evidence of right ventricular (RV) dysfunction consequent to pulmonary artery hypertension (PAH).

Exclusion criteria included 1) patients with acute pulmonary embolism; patients without PAH or RV dysfunction; not fit to undergo cardiopulmonary bypass(CPB); and 2) cases of emergency pulmonary embolectomy.

Variables included demographic variables, pulmonary artery pressure (PAP)(Systolic,  diastolic and mean), Central venous pressure(CVP), Oxygen saturation (Spo2), RV dysfunction by tricuspid annular plane systolic excursion (TAPSE), CPB time, location of thrombus by Jamieson’s classification, postoperative course and complications.

Pre and postoperative echocardiogram gave pulmonary artery systolic pressure (PASP) and TAPSE. Intraoperative direct needle manometry of main pulmonary artery (MPA) before and after PTE gave respective PAP values. CVP and spo2 before and after PTE were also measured.

Patient details

Patient 1, a 23 year old lady with Primary Anti phospholipid antibody syndrome (APLA) presented to IPGMER with shortness of breath (SOB) and bipedal edema. Her CTPA showed complete occlusion of left PA (LPA) and subacute occlusion of posterobasal segmental branches of right lower lobe PA. She had consequent severe PAH, severe TR, RV failure and managed conservatively (Tablet Warfarin, Inj Enoxaparine, Tab Tadalafil). In January 2021, she developed RV failure induced hepatic dysfunction and Jaundice, room air saturation dipped to 57%. She underwent PTE in April, 2021.

Patient 2, a 38 year old obese lady attended IPGMER in January 2023 with SOB since the last 21 days. 2D Echo revealed high mean PAP (48 mm Hg). CTPA revealed subacute thrombosis in RPA extending into right lower lobar segmental branches. Treatment with Tab. Riociguat, Tab. Mecitentan and Inj. Heparin followed by Tab. Rivaroxaban provided no significant improvement with room air saturation dipping to 60%. The patient was put up for PTE in May 2023.

Fig 1: CTPA of patient 1 and 2

Patient 3, a 28 year old lady had recurrent deep venous thrombosis (DVT) and SOB since October 2022. On evaluation found to have APLA syndrome (March 2023). CTPA revealed near complete obstruction of RPA and branches. 2D Echo revealed severe PAH with mean PAP 54 mmHg and subsequent RV dysfunction. As room air saturation dipped to 54%, she was put up for PTE in August 2023.

Anesthetic Management

Along with General anaesthesia, inhaled nitric oxide was utilised to lower PAP. Monitoring was done by a radial and a femoral arterial line, central venous line, pulmonary arterial catheter, electrocardiography, nasopharyngeal temperature probe and transesophageal echocardiography (TEE).

CPB Pump Setup

We utilised a standard CPB circuit with Del nido cardioplegia, aortic and bicaval cannulation. Three pump suction lines, with one as a vent sucker for right upper pulmonary vein (RUPV) and other 2 free suckers were used. A hemoconcentrator for ultrafiltration was utilised. Core temperature was lowered to 24-28 °C (deep hypothermia) and flows were maintained at 2-2.4 l/min/m² with intermittent short term (3-5 minutes) circulatory arrest.

Surgical Technique

Median sternotomy, pericardiotomy, pericardial stay sutures were followed by direct pressure manometry by puncturing MPA. Aorta was dissected off MPA and RPA, and SVC is then looped and mobilized almost upto innominate vein confluence. By retracting both aorta and SVC away with vessel loops, intrapericardial mobilization of RPA and LPA was done upto the lower braches without opening the pleura.

CPB is entered via standard cannulation of ascending aorta and both vena cavae after heparinization. Root cardioplegia needle is inserted. Heart is stopped with Delnido cardioplegia, temperature lowered to 28 °C, and held there. A bullet cardiotomy suction is then used to vent RUPV.

In case of RPA THROMBUS, RPA is exposed between SVC and Aorta by mobilization using vessel loops and an arteriotomy is done. Since the RPA is filled with lumen shaped thrombus at this stage, there is not much back bleeding. Any fresh clot is removed to see the chronic thrombus. Next and most important step is the creation of correct plane of dissection, which appears as a smooth pearly white structure which can be peeled with controlled dissection by an olive tipped endarterectomy dissector. With the gradual development of this plane, the incision of RPA is extended upto the lower lobar branches, and this is aided by the movement and traction of aorta and SVC to right and left using vessel loops. Whole of RPA now lay open. The chronic thrombus is still in place, and temperature is held at 28 °C. Now the thrombus is gradually taken out, and openings of the branch PA starts being visualized. Back bleed also started, and to clear the field, temperature is lowered to 24 °C, and flow lowered to 1-1.2 l/min/m², at which, field can be cleared with 2 cardiotomy suctions. Circulatory arrest was only needed for a brief period of 3-4 minutes to clear the sublobar branches. While doing so, traction and dissection of thrombus evert the media, and may cause PA perforation. Gentle extraction of the thrombus ensures en masse removal (Fig 2).

Afterwards, gentle positive pressure ventilation is needed to check for leaks in PA wall, which appear as air bubbles in the operating field. Brisk bright red back bleed indicates complete clearance. Pulmonary arteriotomy repair started at distalmost angle, and after taking few sutures, flow was re-established. Rest of RPA was then closed in two layers with running 5-0 polypropelene sutures (Fig 2).

In case of LPA THROMBUS, an incision is made in the MPA and extended into the LPA beyond the origin of the upper lobe artery. Rest of the steps are same as discussed above for RPA.

Temperature was raised and patient weaned off CPB gradually, direct PA pressure manometry was done, and chest was closed after hemostasis.

Fig 2: RPA clearance and repair, with endarterectomy specimen of all 3 patients (First One LPA, rest 2 RPA)

Total 3 patients were operated for CTEPH from April 2021 to August 2023. All 3 patients were extubated the next day with median ventilation time being 24.5 hours. There was no mortality. In follow ups ranging between 1 and 30 months, all 3 patients reported significant improvement in quality of life, and returned to New York Heart Association (NYHA) Class I. There were no neurologic complications.

Table 1 summarises the results with all different data and values.

Table 1: Perioperative details of patients undergoing PTE

PREOPERATIVE FINDINGS:

1) Demography:

2) 2D Echo:

3) Preoperative CTPA

INTRAOPERATIVE FINDINGS:

SpO2 (%)

CVP

ABP (systolic/diastolic/Mean in mmHg)

PAP (Systolic/diastolic/Mean in mmHg)

POSTOPERATIVE FINDINGS

• ICU Parameters:

2) 2D Echo:

3) Postoperative CTPA:

4) Follow up (months)

PTE is the definitive treatment of CTEPH [1]. Good outcome in PTE depends largely on the complete clearance of organised thrombus [8].

Literature has extensive description of the use of long term DHCA in the conduct of PTE and the side effects thereof [2-6]. Different strategies to limit the use of DHCA and its side effects have also been described.

In our simple modification, temperature is lowered to and held at 28 °C during dissection of chronic thrombus, which itself prevents back bleed. After completion of dissection, temperature is lowered furthur as the thrombus is being pulled out. The flow is kept at 1-1.2 l/min/m², and managed by cardiotomy suctions. During subsegmental bronchi thrombus dissection, circulatory arrest for 3-4 minutes has to be done at 24 °C to complete the remaining endarterectomy.

Division of the great vessels was avoided, thus minimizing vascular trauma [9]. Due to the minimal time in circulatory arrest, the need of complex cannulation of the aortic arch vessels for selective antegrade cerebral perfusion (ACP) is negated [1-10].

These modifications allowed us to minimise the adverse effects of long term DHCA, while maintaining a relatively bloodless field, allowing complete clearance of the PAs.

LIMITATIONS:

The following limitations remain:

• The sample size is too small to obtain statistically significant results.
• The retrospective nature of the study itself is a limitation and a hindrance to obtain extensive set of data despite best efforts.

With advances in operative and perfusion strategies, PTE does not need longer total circulatory arrest and profound hypothermia (18 °C) and the related side effects of these can be avoided. However, the present study contains too few cases to establish the advantages of our technique. Our future endeavors in this line will continue with that goal in mind.

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