Operation:
Our surgical approach was as previously described.1 We positioned the patient supine with a bump underneath the left shoulder blade to elevate the left hemithorax and extend the neck. Double lumen endotracheal intubation was used to achieve left lung isolation and a transesophageal echocardiography (TEE) probe was placed. A 5cm parasternal anterior thoracotomy was made in the third intercostal space (Image 2). Two inches of subcutaneous fat made visualization difficult. A mini-mitral retractor (Estech, AtriCure Corporate Headquarters 7555 Innovation Way Mason, OH 45040 USA) was used to facilitate exposure. The pericardium overlying the right ventricular outflow tract was identified and opened in parallel direction to the Right Ventricular Outflow Tract–Pulmonary Artery. Traction sutures were applied to the edges of the incised pericardium.
With this exposure, we realized that our incision was too inferior, in that the right ventricle was preferentially exposed rather than the body of PA (Image 3). In hindsight a second intercostal space incision would have been better for isolation of the main PA. In order to better facilitate exposure, we placed a simple retraction suture in the main PA to pull it inferior. We were also prepared to resect a portion of the second rib, but such was not required.
The right common femoral vein and artery were exposed in a standard fashion. The patient was fully heparinized and cannulation of the common femoral vein (wire-guided 25-French Medtronic venous cannula extending into the right atrium verified by transesophageal echocardiography) and artery (wire-guided 18-French Femoral-Flex cannula ) was accomplished. Due to the deep layer of subcutaneous fat encountered, we decided to tunnel the cannuli through separate stab incisions. This facilitated the insertion of needle and guide wire into target vessels followed by dilation of each vessel and proper TEE guided placement of wires and cannuli with minimal line kinking and enhanced ergonomics (Image 4).
Once the ACT (Activated Clotting Time) was confirmed to have reached above 400 seconds, cardiopulmonary bypass (CPB) was initiated. At that point, a one-inch incision was made in the main pulmonary artery in order to insert ring forceps and extract the clots. Although full cardiopulmonary bypass with approximately 5 L/min was ongoing, bleeding from the PA incision was significant making visualization difficult thus requiring simultaneous suctioning through the limited surgical incision in order to identify the clots. Nevertheless, with vigorous suctioning employed to clear the main PA, we were able to identify two large clots, grasp each with endoscopic-type ring forceps and extract the target clots each measuring about 8 inches (Image 5), from the right and left pulmonary trunks.
Further investigation and review of the intraoperative TEE images revealed that the venous cannula had slipped back toward the right atrial (RA)-IVC junction rather than being high up in the mid RA, thus leaving volume undrained and the right ventricle relatively full. Furthermore, we suspected that the flow of 5 L/min was not adequate to empty the heart in this large patient with BMI of 44 who had evidence of fluid overload based on preoperative echocardiography and CT scan. With this in mind, we should have deployed dual venous cannulas (placed via the common femoral vein into the RA and a second percutaneously placed superior vena cave (SVC) cannula inserted under TEE guidance via the right internal jugular vein). We believe dual percutaneous cannulation and confirmation of accurate position by TEE is advisable in large patients and would prevent this undue hardship of exposure and clot retrieval.
Once the two large clots were extracted, the pulmonary arteriotomy was closed with multiple pledgetted 3-0 prolene stitches, instead of the usual running two-layer closure. This technique facilitated repair of the pulmonary artery while applying suction to clear the bleeding from the surgical site, given inadequate venous drainage.
The patient was then weaned off cardiopulmonary bypass without difficulty. Cardiac function was assessed via TEE and the right ventricle remained dilated however function had improved to only mildly depressed systolic function (compared with severely depressed systolic function pre-operatively). Hemostasis was ensured and two chest tubes were placed through separate entry points into the fourth intercostal space. The anterior thoracotomy was closed in standard fashion and decannulation followed by repair of femoral vessels with resultant excellent distal pulses in the femoral artery.
In a follow-up case, and after learning from the aforementioned experience, we modified our technical approach by making the anterior thoracotomy incision in the second intercostal space, inserting a second percutaneous cannula in the SVC, and placing a 2 cm purse-string suture about the pulmonary arteriotomy prior to incision which was sufficient to seal the pulmonary artery entry point at the end of the procedure.
Post-operative course :
Aerosolized Epoprostenol Sodium (Flolan) was initiated in the operating room prior to transport to the ICU to support right ventricular function. The patient required inotropic and ventilatory support until post-operative day (POD) 3 at which point he was extubated. Flolan was weaned based on a combination of central venous gas oxygen saturation, central venous pressure and echocardiographic assessment of RV function given absence of a PA catheter to assess right heart function. Notably, the patient had a known left femoral DVT pre-operatively, and an IVC filter was placed on POD 3 as a safeguard for further pulmonary embolism. His hospital course was further complicated by thrombocytopenia and non-oliguric acute kidney injury with coinciding hyperkalemia, requiring one session of hemodialysis. Given exposure to heparin, a heparin-induced thrombocytopenia (HIT) immunoglobulin and serotonin release assay were sent and both were positive. Heparin was discontinued, Argatroban was initiated and ultimately transitioned to coumadin. Extensive post-operative mobilization and physical therapy were required for convalescence due to extended ICU stay, patient size, and a recurrence of severe gout that immobilized him for several days. Ultimately, the patient discharged on POD 19 not requiring dialysis or supplemental oxygen, ambulating and tolerating a diet.
Our most recent patient who underwent MIPE for massive saddle PE, and the fifth patient in our series total, underwent the procedure, was extubated on POD 0, transferred to the general care floor on POD 1 and discharged home on POD 3.