11.5.8 Minimally invasive surgery

• Variations of the sternotomy depending on the access required: parasternal incision, L-shaped or inverted L-shaped mini-sternotomy, etc.
• High mini-sternotomy for AVR.
• Right or left mini-thoracotomy (4th intercostal space) for mitral valve surgery.
• Left mini-thoracotomy for aortic valve implantation.
• Video-assisted port access system, HeartPort™ (not widely used).
• Robotic system (AESOP 3000™, Da Vinci™, Zeus™); these systems allow very fine manipulations such as mitral plasty, but it is problematic to perform knots and does not provide tactile sensation to the operator; it remains very expensive (equipment 1.5 million US $, assistance 150'000 US $ / year, disposables 2'000-5'000 US $ / case) [3].
• Capnothorax; insufflation of CO₂ into the thoracic cavity during thoracoscopic robotic surgery significantly reduces the presence of air in the left lung cavities, which are difficult to debulk without direct access to the heart at the end of ECC. Gas pressure must not exceed 10 mmHg (CO₂ flow < 2-3 L/min) to avoid interference with venous return. The presence of air in the thorax acts as an electrical insulator, preventing defibrillation via the external patches; the patient must be ventilated on both lungs and the thorax must be exsufflated in the event of defibrillation or cardioversion.

Telemanipulation, robotics and video assistance have been added. Comparative series show that after a learning curve the results are as good as with the conventional technique [2,4].

• Short and long term mortality identical.
• Identical incidence of atrial fibrillation.
• Lower rate of thoracic wound infection than sternotomy, but possible complications of inguinal incision.
• Particular advantages: better aesthetics, quicker mobilisation, early rehabilitation, shorter hospital stay, fewer transfusions and fewer wound infections.
• Disadvantages: Femoral cannulation imposes retrograde flow in the aorta; there is a risk of aortic dissection and infection of the inguinal wound; these disadvantages are eliminated by right subclavian cannulation. Operating times are longer.

 ECC technique

When using ECC, these techniques are based on modifications of cannulation, aortic clamping and cardioplegia mode [1,3].

• Femoral venous cannulation; a multi-orifice cannula (21F-28F) is inserted into the RA and then advanced 3-5 cm into the superior vena cava. TEE is used to ensure that the guide on which the cannula is mounted is not lost in the atrial appendage (risk of perforation) or in the LA by accidentally crossing a patent foramen ovale.
• Pulmonary drainage; the return to the LV can be performed by draining the pulmonary artery using bypass suction. A multi-orifice balloon-tipped catheter (Endovent™ Edwards) is placed via the right internal jugular vein (11F introducer) and its position between the pulmonary valve and the bifurcation is monitored by TEE.
• Cannulation of the ascending aorta; certain incisions (mini-sternotomy, mini-thoracotomy) provide sufficient access to cannulate the ascending aorta in the conventional way: arterial bypass cannula, cardioplegia cannula, aortic clamping.
• Femoral artery cannulation (17F-21F); the tip of the cannula is in the primitive iliac or distal aorta. Alternatively, if atheromatosis prevents cannulation: right subclavian cannulation.
• Aortic clamping via the transthoracic route using a special clamp, or via the endovascular route using a balloon introduced via the femoral artery (EndoClamp™ Edwards); in the latter case, the position of the balloon must be continuously monitored on TEE, as it can easily migrate proximally and impact the aortic valve, or recede distally and block the brachiocephalic trunk.
• Anterograde cardioplegia using a conventional cannula implanted in the ascending aorta upstream of the clamp (transthoracic access) or via the distal end of the aortic clamping catheter (femoral access). The long-axis TEE view of the ascending aorta (colour Doppler) is used to check that the cardioplegia solution perfuses the root of the aorta.
• Retrograde cardioplegia by endovenous cannulation of the coronary sinus; the catheter is inserted through the right internal jugular vein and guided from the RA into the coronary sinus using TEE. When the balloon is inflated, the pressure recorded by the catheter is similar to that of the RV; the perfusion pressure measured at the tip of the catheter must remain < 30 mmHg during the administration of cardioplegia.

• The choice of technique must take into account three constraints:
  • Unstable haemodynamics, compromised by valvulopathy and possible ventricular dysfunction.
  • Painful stimulation varies according to technique; thoracotomy is more painful than sternotomy, but thoracoscopic incisions during robotic surgery are not very painful.
  • Rapid recovery and early extubation.
  • Propofol and sevoflurane give identical results [2].
• Monitoring identical to conventional surgery:
  • Preferably left radial arterial cannulation; the right radial is useful for monitoring flow in the brachiocephalic trunk. The femoral arteries remain free for bypass cannulation.
  • 2-3 lumen central venous catheter (internal jugular or subclavian).
  • 11F introducer in the right internal jugular vein (for retrograde cardioplegia and/or pulmonary drainage).
  • Continuous echocardiographic monitoring is essential.
• Single lung ventilation in right thoracotomy (double lumen endotracheal tube) as the right lung is between the incision and the heart; this is not generally required in left anterior thoracotomy as access to the pericardium is direct. The 2L tube can be left in place until recovery if this is less than an hour after the end of surgery, otherwise transtubation is required. Transtubation can be avoided by using a bronchial blocking tube. Single-lung ventilation after bypass significantly reduces the PaO₂ /FiO₂ ratio due to the shunt effect in the non-ventilated lung; in the event of arterial desaturation or defibrillation, both lungs must be ventilated briefly.
• Strict installation:
  • Right or left hemithorax elevated by a longitudinal pad under the scapula; the thorax forms an angle of 25-30° with the plane of the table; the arm of the elevated side remains on the table next to the body to free the hemithorax.
  • The ipsilateral crease is left free for access to a femoral cannula, either because it is used or if necessary.
  • External defibrillator plates adhered to the patient, as limited access to the heart means that epicardial paddles cannot be inserted.
• For procedures without ECC, combined anaesthesia is an elegant solution because epidural analgesia promotes early awakening and rapid mobilisation; on the other hand, thoracotomy is a more painful access route than sternotomy in the postoperative period. Alternatives for ECC: intercostal or paravertebral blocks.

• Assessment of blood volume and biventricular function in the absence of a direct view of the heart;
• Pre-operative assessment of the thoracic aorta during femoral cannulation;
• Aids in mandrel and cannula placement;
• Monitoring of the aortic occlusion balloon and possible aortic leakage during endovascular clamping;
• Monitoring of LV for risk of dilatation;
• Debubling at the end of ECC.