Perioperative incidence of ECMO and IABP on 5901 mitral valve surgery procedures

A retrospective, observational study was undertaken of prospectively collected data in 5901 consecutive patients undergoing mitral valve surgery, of which 3389 underwent MIMVS through RT between January 2016 to November 2021 for a period of 6 years from 11 Cardiac Surgery Institutes of GVM Care & Research Italia. Two-five hundred twelve procedures were performed in sternotomy. The main reason for performing a sternotomy approach was the selection patient for the learning curve, and in case of very poor left ventricular ejection fraction, strong pleural adhesions, severe chronic obstructive pulmonary disease and active endocarditis with abscess involving the mitro-aortic continuity. All patients signed an informed consent form to allow clinical and administrative data storage and utilization for scientific purposes according to the General Data Protection Regulation. Because of the retrospective nature of this study, the local ethics committees waived the need for patient consent. The primary outcome of the study was the mortality and incidence of low cardiac output treated with intra-aortic balloon pump (IABP) with or without inotropic support and the incidence of Postcardiotomy Cardiogenic Shock (PCS) treated with Veno-arterial (VA) extracorporeal membrane oxygenation (ECMO) on patients undergoing mitral valve surgery (MVS) through right mini-thoracotomy (RT) vs conventional full sternotomy (FS).

Low cardiac output was defined as the need for postoperative inotropic support for more than 48 h in the intensive care unit and/or from an intra-aortic balloon pump.

The standardized surgical approach for MIMVS has been reported elsewhere. Briefly, MIMVS by a way of right anterior thoracotomy was performed through a 5–7 cm skin incision placed at 3th or 4th intercostal space. Two trocars are inserted in the thorax to allow positioning of a ventricular vent, CO₂ insufflator, camera device and pericardial stay sutures. Whereas at the beginning of our experience the approach involved retrograde arterial perfusion and balloon endoclamping, the procedure has evolved to a technique with ascending aorta cannulation, long femoral venous cannula drainage, and direct transthoracic aortic clamping. Specifically, direct aortic cannulation was performed using Easyflow (Sorin, Salluggia, Italy) or Straightshot (Edwards Lifesciences, Irvine, Calif) cannulas. Biomedicus single stage (Medtronic, Minneapolis, Minn) or RAP single 2 stage cannulas (Estech) were inserted through the femoral vein into the right atrium and the correct position was achieved with the Seldinger technique under transesophageal echocardiographic guidance. In case of mitral and tricuspid valve surgery, a single 2 stage cannula (RAP, Estech) was used as it allows to drain simultaneously the superior and inferior venae cavae. After vacuum-assisted cardiopulmonary bypass (− 40 to − 60 mmHg) was established, the patients were cooled to 34 °C. the ascending aorta was clamped with the Cygnet crossclamp (ovare surgical System, Cupertino, Calif) or with the aortic clamp (Cardiomedical GmbH, Langenhagen, Germany; distributed by sorin, Salluggia, Italy) and antegrade cold crystalloid or warm blood cardioplegia is delivered directly into the ascending aorta by a needle vent catheter. For conventional approach on mitral valve surgery was performed in median sternotomy with central cannulation [6].

The mitral valve is approached with a traditional left paraseptal atriotomy and exposed using a specially designed atrial retractor held by a mechanical harm inserted through a right parasternal port. Mitral valve procedures were performed under a combination of direct vision and thoracoscopic assistance. All patients received an accurate intraoperative transoesophageal echocardiogram before and after weaning from cardiopulmonary bypass machine. In patients who had an attempt to repair, our policy is to replace the mitral valve if (a) at the hydrostatic saline test after several attempts, there is still some degrees of mitral regurgitation, (b) the surface of coaptation is not enough to guarantee a long durability, (c) at intraoperative echo, there is more than mild mitral regurgitation. Twelve surgeons contributed to this series, with 2 of them (GS, GN) performing 45.2% of the operations.

The indications for initiating treatment with IABP in this patients was the following: (a) IABP support for persistent preoperative ischemia despite maximum medical treatment (b) patients not able to be discontinued from CPB although forced inotropic support, (c) patients in low-cardiac output status just after a "difficult" discontinuation of CPB, supported by high-doses of inotropes, (d) patients with "difficult" discontinuation from CPB and spontaneous appearance of arrhythmia (premature ventricular beats or VT) not amenable in anti-arrhythmic continuous infusion and (e) post cardiotomy low cardiac output syndrome. Prophylactic initiation of IABP treatment was not advocated in any of the cases [7, 8]. A Datascope system (Datascope Corp, Paramus, NJ) was utilised. The IABP was introduced percutaneously through the common femoral artery in 95 patients and through an open access of the femoral artery in the remaining 4 patients [9]. Correct placement of the device was routinely confirmed with Chest X Ray in ICU. Once mediastinal drainage was minimum (< 50 ml/h), patients were anticoagulated with Heparin infusion, keeping the ACT > 180–200 s [10, 11].

ECMO was initiated intraoperatively in the operating room for circulatory instability during or immediately after weaning from the cardiopulmonary bypass (CPB) in the primary cardiac procedure. The capability to institute ECMO secondarily in the ICU, for delayed PCS or cardiac arrest, was available. The clinical criteria for PCS included the following: left atrial pressure > 15 mmHg; central venous pressure > 12 mmHg; metabolic acidosis (i.e. pH < 7.3 with serum lactate > 3.0 mmol/L); end-organ hypoperfusion (urine output < 30 mL/h); cardiac index < 2.2 L/min/m²; and systolic blood pressure < 80 mmHg despite adequate filling volumes, use of multiple adrenergic agents (epinephrine > 0.1 µg/kg/min or dobutamine > 10 µg/kg/min, norepinephrine > 0.1 µg/kg/min), or an intra-aortic balloon pump (IABP). VA-ECMO support was initiated via peripheral cannulation through the femoral route with the semi-open method, and an additional 6 Fr catheter was systematically inserted distally into the femoral artery to prevent leg ischemia [12]. ECMO blood flow was adjusted on based on clinical assessments (e.g. pre-oxygenator venous oxygen saturation, evidence of hypoperfusion, resolution of hyperlactatemia, normalization of mean arterial pressure). Intravenous unfractionated heparin was given to maintain an activated clotting time of 180–210 s, or an activated partial thromboplastin time of 1.5–2 times normal. ECMO-related complications were carefully monitored. ECMO weaning was performed in patients who fulfilled our published institutional weaning criteria and passed an ECMO weaning trial consisting in decreasing and clamping ECMO flow. In general, the patient should have a pulsatile arterial waveform for at least 24 h; be hemodynamically stable, with baseline mean arterial pressure greater than 60 mmHg with no or low doses of catecholamines; should have left ventricular ejection fraction (LVEF) of 35%, and an aortic velocity time integral (VTI) of ≥ 12 cm; and have recovered from major metabolic disturbances [13]. Weaning was considered unsuccessful if ECMO re-cannulation was required within 2 days of decannulation.

Continuous data were expressed as mean ± standard deviation or median with the interquartile range and categorical data as percentages. All statistical analyses were performed with SPSS 22.0 (SPSS, Inc., Chicago, IL, USA).