Minimally invasive techniques in congenital heart surgery

A right anterior minithoracotomy (AMT) is less visible in females as the incision will remain within the submammary sulcus. A ministernotomy (MS) is mostly offered to male children but also employed in females for repairing lesions other than an atrial septic defect (ASD) II because it can guarantee, according to our experience, a better exposure of the great vessels when other manoeuvres are required (such as aortic cross-clamping, pulmonary valvotomy, closure of patent ductus arteriosus).

According to our minimally invasive surgical protocol, when central cannulation is employed, aortic cannulation is carried out using straight aortic cannulae (DLP cannulae; Medtronic, US), and bicaval cannulation is achieved using angled venous cannulae (DLP cannulae; Medtronic) or straight armed cannulae (Fem-flex II Duraflo-treated femoral venous cannulation cannulae; Edward Lifesciences).

Since June 2008, as an evolution of our minimally invasive protocol, we have routinely employed peripheral cannulation for cardiopulmonary bypass in patients with simple CHD and a body weight >18kg. (This body weight cut-off for peripheral arterial cannulation has progressively decreased over the last few years; it was 35kg at the beginning of our experience.) Remote cardiopulmonary bypass is carried out by percutaneous cannulation of the internal jugular vein (IJV) followed by surgical isolation and cannulation of the femoral vessels. The IJV cannulation is performed under two-dimensional echo guidance by an anaesthesiologist (DLP femoral arterial cannulae; available in three sizes, 14 Fr., 17 Fr. and 21 Fr.) after 100U/kg of heparin have been systemically administered.

 

A 2-cm incision is then employed at the inguinal fold (the so called ‘bikini’ incision) for exposing the femoral vessels. After full systemic heparinisation has been achieved (activated clotting time (ACT), >400 seconds), direct arterial cannulation is carried out (Fem-flex II Duraflo-treated femoral venous cannulation cannulae). Venous cannulation is then performed using the Seldinger technique under two-dimensional transoesophageal echo guidance (Fem-flex II Duraflo-treated femoral venous cannulation cannulae) (Figure 1).

In patients requiring femoral cannulation, our routine practice is to include the use of near infrared spectroscopy (NIRS) (Invos Cerebral Saturometer, Somanetics, US) to monitor both lower extremities (the NIRS sensors are positioned on the anterior side) to appreciate any variation of oxygen saturation in the cannulated leg during extracorporeal perfusion. We usually add selective distal arterial perfusion in cases of prolonged cardiopulmonary bypass (>80 minutes) when the NIRS values become critical (NIRS, ≤30).

Assisted venous drainage (with a maximum vacuum of 50mmHg achieved by wall suction) is adopted to optimise perfusion flows and help minimise the sizes of tubing and venous cannulae. Wall suction is applied directly and modulated and measured in the venous reservoir. 

Once cardiopulmonary bypass is started, mild hypothermia (rectal temperature, 34–35°C) is reached. At full flows, the venae cavae are usually snared using umbilical tapes or, as an alternative, the superior vena cava is occluded with a vascular clamp (Debakey vascular clamp; Codman, US), inserted through a 0.5cm separate incision (Figure 2).

The MS approach has been employed to correct simple CHD lesions such as ASD, partial atrioventricular (AV) septal defects and ventricular septal defects. However, the application of this technique has recently been extended to correct selected patients with other, more complex CHDs, including complete AV canal defects, tetralogy of Fallot and transposition of the great arteries. 

When we began using the technique, a 6–7cm skin incision in the midline of the chest was adopted with division of about half of the sternum. Due to optimisation of the retraction system (Bookwalter retractor; Codman, Germany), we now employ a 2–4cm skin incision in the midline of the chest; the superior margin of the incision is at or about 2cm below the level of the nipple (see Figures 3 and 4). The sternum is longitudinally divided only in its lower third (only the xiphoid apophysis) and retracted in order to expose the aorta. Due to the small surgical field, the inferior vena cava cannula is passed through a separate 5mm skin incision (which is later used for inserting a chest drainage) in order to optimise surgical manoeuvres.

It is of note that the right pleural space is routinely opened and the pericardium is incised laterally down to 1cm from the right phrenic nerve to avoid possible cardiac tamponade due to postoperative pericardial effusion (now draining into the pleural space). This procedure has contributed to the decreased incidence of postcardiotomy syndrome.

We utilise right anterior minithoracotomy (AMT) in children and adults for ostium secundum type ASD closure and repair of partial AV canal defects. It is used mainly in females as an alternative to MS and is chosen by the majority of males who undergo minimally invasive procedures. 

When we began using the technique, a 6–7cm semilunar incision in the sulcus of the right breast was used (6–8cm away from the nipple area), allowing entry to the chest in the fourth intercostal space. In the prepuberty age group the incision was kept very low under the right nipple, particularly in female patients where the aim is to avoid any possible future interference with breast development.

Presently, the incision length is 2–4cm due to utilisation of the peripheral bypass technique and the retraction system (Bookwalter retractor; Codman, Germany) (Figures 3–5). Subcutaneous fat and mammary glands are gently dissected from the fascia up to the fourth intercostal space where the chest cavity was entered. The incision of the intercostal space is about 1cm longer than the skin incision at each side. A soft tissue retractor (Edward Lifesciences) is used to retract soft tissue (and its utility is larger when the subcutaneous tissue is well represented) and for haemostasis (see Figure 2). 

The utilisation of video-assisted optical technology by means of an optical scope (Vitom 25 exoscope, Tricam® three-chip camera head, Aida® Control Karl Storz, Germany) inserted through a separate 5mm incision in the fourth intercostal space has also contributed to the miniaturisation of the surgical incision and to facilitating surgical manoeuvres which may not be possible by direct operator vision.

Special surgical instruments are used in our minimally invasive practice in patients requiring AMT (minimally invasive needle holder, forceps and scissors, Cardiovations, Ethicon US; Scanlan, US; Knot pusher, Aesculap, Cook Medical, US); this facilitates surgical manoeuvres in a much-reduced field of action. 

Right lateral minithoracotomy 

In addition to a lower MS and a right AMT, a right posterior minithoracotomy (RPT) is offered as a surgical option. We have found this an ideal approach for treating discrete subaortic stenosis, partial anomalous pulmonary venous connections and sinus venosus ASD closure. This technique has been a surgical option for patients with simple CHD since 2001.

It was described as a technique for repairing simple CHD by Metras et al in 19996 and has been modified by us from a classic, wide RPT to a minimally invasive approach. Currently, the chest is entered in the fourth intercostal space through a 4cm subscapular incision starting from the angle of the scapula and extending anteriorly (Figure 6). This technique has been mainly employed in female patients (under the patient’s specific request). Through this approach, the aorta can be easily visualised and cross-clamped. Furthermore, a lateral approach is ideal when partial anomalous pulmonary venous connections are associated with sinus venosus defects. The cross-clamping of the aorta is usually employed with this approach by means of the Cygnet aortic cross-clamp (Novare Surgical System, US), and the cardioplegic solution is delivered by a 60cm long cardioplegia needle (Maquet cardioplegia needle, Germany); both these instruments are designed to optimise surgical vision. 

In patients treated with MS or RPT, a conventional aortic cross-clamping followed by cold haematic cardioplegic cardiac arrest is employed. Heart arrest is obtained by inducing a ventricular fibrillation with an epicardial fibrillator (Stocker Instrument Fibrillator, Stocker) in all patients requiring an AMT.

At the end of the intracardiac repair, an accurate deairing of the left cardiac section is performed under transoesophageal, two-dimensional echocardiographic monitoring. The deairing is achieved by filling the left cardiac chambers with saline solution before complete separation of the systemic from the pulmonary circulations; a sustained blow ventilation is always performed by the anaesthesiologist to clear the left atrial chamber from residual air bubbles. It is of note that during induced ventricular fibrillation it is important to avoid blood suction inside the left cardiac sections.

In patients requiring aortic cross-clamping, a further debubbling is achieved through the cardioplegia needle before and after aortic clamp removal by continuous suction. After surgical repair is completed and the intracardiac air bubbles are cleared, induced fibrillation is discontinued. A lidocaine intravenous bolus of 1mg/kg is given, and the heart is promptly defibrillated by external DC shock (3–5J/kg) by means of external defibrillation pads (Philips Medical Systems, US) when the regular rhythm is not naturally restored. 

At the end of cardiopulmonary bypass, systemic heparinisation is reverted and the femoral cannulae are removed. During the closure of the surgical incisions, the superior vena cava cannula is removed by the anaesthesiologist. 

In order to minimise patient’s trauma and to obtain the maximal drainage capability, a silicon chest tube (Blake drains, Ethicon, US) is usually positioned to remove residual intrathoracic fluids, both from the right pleural space and the mediastinum. This particular drainage system, according to our unpublished studies, has some advantages if compared to conventional drainages: 

• each single tube drains more than one mediastinal space
• the drain has the same drainage efficacy as conventional chest tubes with a lower calibre
• the drain presents significantly less related postoperative complications 
• use of the drain is associated with lower postoperative pain, as perceived by the patients. 

At the end of surgery, a skin adhesive (Dermabond skin adhesive, Ethicon, US) is positioned at the level of the incision as an ‘add-on-measure’ to the intradermic suture line to protect the surgical site (antibacterial barrier). The use of this skin adhesive, from our unpublished studies, is associated with a significantly lower incidence of postoperative wound infections and dehiscence when compared to the use of a traditional intradermic suture alone; in addition, it does not require additional wound medications and is cost-effective.  

Postoperative pain control is achieved by a continuous infusion of analgesic medications (ropivacaine, 0.2–0.4mg/kg/h) in the subcutaneous tissue by a pump (Solace postoperative pain pump, Truvice Surgical Device, LLC). This subcutaneous infusion system avoids, in our experience, the additional requirements of any intravenous pain medications. 

A full sternotomy is not usually necessary for the correction of simple CHD, and many institutions have reported excellent surgical results using the transxyphoid approach or MS.(2,7,8) An inferior partial sternotomy ensures good access to the great vessels for cannulation; in addition, MS guarantees better chest stability in the postoperative period and a reduction in wound infections,(7) has the theoretical advantages of shorter hospitalisation and cost reduction(3) and improves quality of treatment and patient satisfaction.(2)

Since 1996, we have routinely adopted a minimally invasive, gender-differentiated surgical approach for the correction of simple CHD. We offer an AMT to females as the incision remains within the submammary sulcus and aortic cross-clamping is not usually required. We recommend an MS for male children, but also for females when repairing lesions other than ASD II because it can guarantee, according to our experience, a better exposure of the great vessels when other manoeuvres are required.

The use of right anterolateral thoracotomy has been advocated for the correction of simple and complex CHD.(9–11) This may be associated with right breast asymmetry, although recent publications report only a rare incidence for such a complication.(2–4) 

Our institutional policy of promoting a gender-differentiated minimally invasive approach for patients with CHD(2,4,5) has proven safe and produced excellent clinical results comparable to classic, more invasive approaches. In addition, our results with AMT show 95% patient satisfaction (which has increased to 100% in the last 3 years) with no evidence of scoliosis, restriction of shoulder movement or problems with breast development or lactation at follow-up. The only complication reported in our female patients with MT is a temporary trivial neurosensorial deficit in the mammary area that disappears within six months of surgical repair. In addition to the benefit of a limited cutaneous incision, we believe that the quality of our results is related to the extreme attention we pay to the dissection and reconstruction of muscle planes. We strongly suggest that the location of the incision in the submammary area be very low, under the right nipple and away from any possibility of future breast development.

The introduction of right lateral minithoracotomy in our minimally invasive surgical armamentarium proves safe and effective, especially in patients where visualisation of the superior vena cava at the right atrial junction is mandatory (as in patients with anomalous pulmonary venous returns from the right lung to the superior vena cava) and also when visualisation of the aortic root is needed (during aortic cross-clamping or while gaining access to the aortic valve or subvalvar area).

The use of peripheral cardiopulmonary bypass(11–13) with direct femoral artery cannulation can be safely utilised in patients with a body weight >18kg without increased operative morbidity or complications related to  peripheral cannulation. The prolonged cardiopulmonary bypass time is associated with plasmatic elevation of creatine kinase and myoglobin levels, especially in patients with critical NIRS values on the cannulated leg during extracorporeal perfusion, which promptly normalise after restoring the physiologic leg perfusion at cardiopulmonary bypass discontinuation. A selective distal leg perfusion should be considered a safe and excellent option in selected patient cases with prolonged cardiopulmonary bypass times.

It is of note also that our liberal use of induced ventricular fibrillation(14,15) has proved to be a safe and reproducible technique. This allows us to avoid cumbersome cross-clamping of the aorta and consequently to minimise surgical incisions, especially in AMT approaches. 

In conclusion, the application of minimally invasive surgical techniques in paediatric cardiac surgery is evolving and new applications are emerging. The application of new retracting systems and the use of peripheral cardiopulmonary bypass allow us to further minimise our surgical approaches without increasing the risk of morbidity for our patients. In the near future, we believe that, due to the miniaturisation of surgical instruments, cannulae and tubing systems, we will extend the use of minimally invasive surgery with peripheral cardiopulmonary bypass in even smaller children or to more complex forms of CHDs.

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