Technique and Patient Selection Criteria of Right Anterior Mini-Thoracotomy for Minimal Access Aortic Valve Replacement

Summary

The goal of this protocol is to describe in detail the technique of minimally invasive aortic valve replacement through a right anterior mini-thoracotomy and central aortic cannulation. This technique can potentially enhance patients' comfort and, by reducing post-operative morbidity, promote lowering the length of stay and global costs.

Abstract

Aortic valve stenosis has become the most prevalent valvular heart disease in developed countries, and is due to the aging of these populations. The incidence of the pathology increases with growing age after 65 years. Conventional surgical aortic valve replacement through median sternotomy has been the gold standard of patient care for symptomatic aortic valve stenosis. However, as the risk profile of patients worsens, other therapeutic strategies have been introduced in an attempt to maintain the excellent results obtained by the established surgical treatment. One of these approaches is represented by transcatheter aortic valve implantation. Although the outcomes of high-risk patients undergoing treatment for symptomatic aortic valve stenosis have improved with transcatheter aortic valve replacement, many patients with this condition remain candidates for surgical aortic valve replacement. In order to reduce the surgical trauma in patients who are candidates for surgical aortic valve replacement, minimally invasive approaches have garnered interest during the past decade. Since the introduction of right anterior thoracotomy for aortic valve replacement in 1993, right anterior mini-thoracotomy and upper hemi-sternotomy have become the predominant incisional approaches among cardiac surgeons performing minimal access aortic valve replacement. Beside the location of the incision, the arterial cannulation site represents the second major landmark of minimal access techniques for aortic valve replacement. The two most frequently used arterial cannulation sites include central aortic and peripheral femoral approaches. With the purpose of reducing surgical trauma in these patients, we have opted for a right anterior mini-thoracotomy approach with a central aortic cannulation site. This protocol describes in detail a technique for minimally invasive aortic valve replacement and provides recommendations for patient selection criteria, including cardiac computer tomography measurements. The indications and limitations of this technique, as well as its alternatives, are discussed.

Introduction

Among heart valve lesions diagnosed as hemodynamically relevant and clinically receiving particular attention, aortic valve stenosis is the most common valvular pathology in the United States and developed countries^1,2. In the Cardiovascular Health Study, 2% of patients had frank aortic stenosis, with a clear increase in prevalence with growing age: 1.3% in patients aged 65-75 years, 2.4% in those aged 75-85 years, and 4% in patients older than 85 years¹. For symptomatic patients presenting with severe aortic valve stenosis, aortic valve replacement is a Class I recommendation in the guidelines of the American Heart Association for the management of patients with valvular heart disease³.

Conventional surgical aortic valve replacement through median full sternotomy (FS) has been established as the gold standard for treating aortic valve stenosis with excellent results in terms of morbidity and mortality⁴. These results have encouraged the extension of therapeutic indications to older patients and patients with a higher risk profile. A number of treatment strategies have been implemented in these patient subsets to maintain the same good results achieved by conventional surgical aortic valve replacement in the general population. Among these alternative treatment modalities, transcatheter aortic valve implantation (TAVI) was introduced in 2002 by Cribier and colleagues⁵. Performed initially in moribund patients, TAVI has rapidly emerged as the treatment of choice for patients with severe aortic stenosis who are not suitable for conventional surgical aortic valve replacement^6,7, or as a less invasive approach for surgery for patients at high risk^8,9.

Despite the improved outcomes of TAVI in selected patient subsets, many patients with symptomatic aortic valve stenosis are still candidates for surgical aortic valve replacement. In these patients, FS aortic valve replacement is the most frequently used approach by cardiac surgeons. Nevertheless, various 'minimally invasive' techniques have been developed with the rationale of reducing surgical trauma¹⁰. All these minimal-access techniques have aimed at improving patient comfort by reducing post-operative pain and accelerating patient recovery by shortening the hospital stay and potentially saving global costs¹⁰. Among minimally invasive incisional approaches upper hemi-sternotomy (UHS) and right anterior mini-thoracotomy (RAMT) have become the predominant techniques reported in the literature¹¹. Right anterior mini-thoracotomy for aortic valve replacement was initially reported by Benetti et al.¹², and upper hemi-sternotomy was first described by several authors¹¹. In addition to incisional alternatives, two arterial perfusion strategies are currently used: i) peripheral femoral arterial cannulation, which is more frequently employed than ii) central aortic cannulation.

In spite of reported improvement in patient outcomes following minimally invasive aortic valve replacement, concerns about the disadvantages of restricted operative field and peripheral arterial perfusion strategies¹³ lead many cardiac surgeons to not let their patients benefit from potential advantages of minimal access approaches for aortic valve replacement. The goal of this protocol is to describe in detail this technique of minimally invasive aortic valve replacement through a right anterior mini-thoracotomy without rib resection/fracture, and with central aortic cannulation for arterial perfusion. By following this protocol, a larger number of cardiac surgeons can perform right anterior mini-thoracotomy for aortic valve replacement in certain patient groups. Patient selection and limitations of the technique are discussed. Early results are compared to those of a cohort of patients undergoing isolated aortic valve replacement by full sternotomy.

Protocol

The protocol follows our institutional guidelines of the human research ethics committee.

1. Patient Selection (Table 1)

1. Identify patients necessitating isolated aortic valve replacement¹⁴.
2. Select among these patients a subgroup without major chest deformities (Kypho-scoliosis), previous history of irradiation or surgery of the right hemi-thorax, need for emergency operation, and operation for active endocarditis.
3. Perform a chest computed tomography (CT) scan to exclude patients with ascending aortic aneurysm ≥4.5 cm.
4. Make the final decision according to the measurements provided by the chest CT (Figure 1 and 2 and Table 1). Choose between the second or third intercostal space, based on closer distances to the aortic cannulation site and the aortic annulus.

2. Preparation for Surgery

1. Prepare the patients for surgery following the institutional guidelines and recommendations for adult cardiac surgery patients, as previously described¹⁴.
2. Place the external defibrillator pads on the back and left chest anteriorly prior to draping.

3. Surgery

1. Access to the heart through a right anterior mini-thoracotomy
   1. Incise the skin transversally over 8 cm with an 18-blade knife over the chosen intercostal space, starting 1 cm to the right of the right sternal edge.
   2. Cut the pectoralis and the superficial layers of the intercostal muscles using the electrocautery. To avoid injury to the right lung, enter the right pleura first with Metzenbaum scissors. Then enlarge the opening of the intercostal muscles with electrocautery.
   3. Preserve the right internal thoracic pedicle by freeing it from the fascia and soft tissue around it using Metzenbaum scissors.
   4. Insert the soft tissue retractor into the right pleura and fix it onto the wound. Take care not to injure the right internal thoracic pedicle.
   5. Place the minimal access retractor over the soft tissue retractor and open it gently and gradually.
   6. Grab the cranially overlying fat with Carpentier forceps and cut it with electrocautery. Take care not to injure the right phrenic nerve.
   7. Open the pericardium over the right atrium with electrocautery and place 2/0 polyglactin stay sutures on both sides of the opening in order to spread the pericardium.
   8. Continue opening the pericardium cranially over the ascending aorta and caudally over the right atrium. Place 2/0 polyglactin stay sutures on both sides of the opening to spread the pericardium.
   9. Check the distal pericardial reflection line over the ascending aorta and the basis of the aortic root to prepare for the placement of the aortic cannulation purse-strings.
   10. Verify the anatomy of the right superior pulmonary vein for the placement of the left ventricular vent.
   11. To expose the distal part of the ascending aorta, gently push down the ascending aorta using a peanut gauze mounted on an Allis clamp.
   12. Place the first purse-string for aortic cannulation just below the distal pericardial reflection line over the ascending aorta using 4/0 polypropylene suture. Complete the preparation for aortic cannulation by adding a second purse-string around the first one using 4/0 polypropylene suture.
   13. Give 300 I.U. of heparin/kg (concentration 5,000 U/mL) through the IV line.
2. Connect the patient to the cardiopulmonary bypass
   1. First puncture the right femoral vein and place the guidewire through the needle into the vein. Enlarge the skin opening with an 11-blade knife. Dilate the puncture site with successive dilators and introduce percutaneously the femoral venous cannula over the guidewire under transesophageal echocardiographic control (Figure 3).
   2. Gently push down the ascending aorta using a peanut gauze mounted on an Allis clamp and puncture the ascending aorta in the middle of the purse-strings. Cannulate the aorta over the guidewire.
   3. Start the cardiopulmonary bypass and cool down the patient to 30 °C (Figure 4). To improve the venous return, let the perfusionnist apply assisted negative pressure of -50 mmHG.
   4. Gently push the superior vena cava towards the left side and place a purse-string on the right upper pulmonary vein with a 4/0 polypropylene monofilament suture. Insert the left ventricular vent through the purse-string to unload the left heart.
3. Prepare for valve resection and replacement
   1. Cross-clamp the ascending aorta just below the aortic cannula using a flexible clamp with a retractable rigid shaft.
   2. Perform an inverted-L aortotomy parallel and at the level of the sino-tubular junction, extending to the non-coronary Valsalva sinus. Retract the inferior ridge of the aortotomy with an Allis clamp.
   3. In case of aortic regurgitation, deliver the antegrade crystalloid cardioplegia directly into the coronary ostia.
   4. Extend the aortotomy through the non-coronary sinus to 1 cm above the aortic annulus. Check the left and right coronary ostia.
   5. Place a 5/0 polypropylene suture on the inferior ridge of the aortotomy and fix it superficially to the anterior aspect of the right ventricle to improve the exposure of the aortic valve.
   6. Place another 5/0 polypropylene suture on the superior ridge of the aortotomy and fix it superficially to the pericardium to improve the exposure of the aortic valve.
   7. Grab in turn the right, non-coronary, and left coronary cusp with endo-forceps and excise them with endo-scissors. Check the mitral valve through the aortotomy.
   8. Use commercially available valve sizers to determine the labeled size of the valve to be inserted. Choose a sizer which comfortably passes through the aorto-ventricular junction.
   9. Place the first braided polyester 2/0 with pledget U-suture on the commissure between the left and right coronary sinuses, using an endo-needle holder. Pass the suture from the ventricle up so that the pledget is on the ventricle side.
   10. Continue the placement of the braided polyester 2/0 with pledget U-sutures clockwise to complete the right coronary sinus.
   11. Place clockwise braided polyester 2/0 with pledget U-sutures on the non-coronary sinus.
   12. Complete the annulus sutures by placing counter-clockwise braided polyester 2/0 with pledget U-sutures on the left coronary sinus, starting at the commissure between the right and left coronary sinuses.
   13. Pass the braided polyester 2/0 sutures onto the sewing ring of the valve prosthesis using a Ryder needle holder.
   14. Slide down the valve prosthesis and remove the valve holder. Tie the sutures and check for any gap between them and the aortic annulus. Verify that the left and right coronary ostia are unobstructed.
   15. Cut the tied sutures using Metzenbaum scissors. Remove the 5/0 exposure sutures on the inferior and superior ridge of the aortotomy.
   16. Close the aortotomy by two 5/0 polypropylene running hemi-sutures. Place the first one on the nadir of the aortotomy in the non-coronary sinus and tie it. Then come up to the angle of inverted L-aortotomy. Put the end of the suture under slight tension.
   17. Continue the closure of the aortotomy by the second 5/0 polypropylene running hemi-suture starting on the left end and coming towards the right side to meet the end of the first hemi-suture. Tie the two ends together and cut them.
   18. Place the ventricular pacing wires on the right ventricle before unclamping the aorta.
   19. Let the operating table tilt in the Trendelenburg position. Reduce the pump flow to 50% of the full flow. Under gentle aspiration of the left ventricular vent, slowly remove the aortic cross-clamp¹⁴.
   20. Resume the full flow of the cardio-pulmonary bypass. Check the hemostasis of the aortotomy closure. Remove the left ventricular vent and tie its purse-string. Check for hemostasis.
   21. Rewarm the patient to 37 °C. Separate the patient from the cardio-pulmonary bypass. When a stable blood pressure is reached, neutralize the heparin by a protamine-infused IV in a 1:1 ratio (3 mg/kg corresponding to 300 U/kg of heparin)¹⁴.
   22. Prepare for removal of the aortic cannula by tying down the first purse-string. Let the assistant gently remove the aortic cannula and finish tying the purse-strings.
   23. Double-secure the aortic cannulation site with a figure of eight 4/0 polypropylene suture. Cut the sutures.
   24. Remove the femoral venous cannula and secure the hemostasis by manual compression for 20 min.
   25. Place one pericardial and one right pleural chest tube. Adapt the pericardium with three loosely tied braided 2/0 polyglactin sutures.
   26. Adapt the ribs with two braided 0 polyglactin sutures. Close the wound in layers in a standard fashion.

4. Post-Operative Patient Care

1. Following the transfer to the intensive care unit, provide the patient with standard post-operative care for cardiac surgical operations¹⁴.

Results

Statistical analysis is done for continuous variables (presented as means ± SD) in Table 2, Table 3, and Table 4 using the non-parametric Mann Whitney test. Categorical variables are presented as percentages in Table 2, Table 3, and Table 4, and are compared by the Chi-square test. The statistical analyses are performed using commercially available software, with a statistical signif...

Discussion

In this protocol, we describe in detail the technique of right anterior mini-thoracotomy for isolated aortic valve replacement, and highlight the patient selection criteria for this procedure. As for any other therapeutic intervention, proper patient selection is the key to successful accomplishment of the procedure. The optimal CT measurements for consideration of patients for this technique are precisely described in this protocol, and are based on experience and consider the extensive work of Dr. Glauber and coworkers...

Materials

Name	Company	Catalog Number	Comments
Heart surgery infrastructure:
Heart Lung Machine	Stockert	SIII
EOPA 24Fr. arterial cannula	Medtronic	77624
FemFlex arterial cannula	Edwards	FEMII20A
Quickdraw 25Fr. femoral venous cannula	Edwards	QD25
Biomedicus 25Fr. Nextgen venous cannula	Medtronic	96670-125
LV vent catheter 17Fr.	Edwards	E061
Antegrade 9Fr. cardioplegia cannula	Edwards	AR012V
Coronary artery ostial cannula 90°	Medtronic	30155
Coronary artery ostial cannula 45°	Medtronic	30255
Soft tissue retractor
STAR soft tissue atraumatic retractor	Estech	EC400220
Soft tissue retractor	Edwards	TRM
Electrocautery	Covidien	Force FXTM
Sutures:
Polypropylene 4/0	Ethicon	8871H
Polypropylene 5/0	Ethicon	8870H
Braided polyesther 2/0 ligature with polybutylate coating	Ethicon	X305H
Braided polyesther2/0 with pledgets V5	Ethicon	MEH7715N
Braided polyglactin 2/0 suture	Ethicon	V114H
Braided polyglactin 0 suture	Ethicon	W9996
Drugs:
Midazolam	Roche Pharma	N05CD08
Rocuronium	MSD Merck Sharp & Dohme	M03AC09
Propofol	Fresenius Kabi	N01AX10
Fentanil	Actavis	N01AH01
Heparin	Braun	B01AB01
Protamin	MEDA Pharmaceutical	V03AB14
Custodiol cardioplegia solution	Dr. F. Köhler Chemie GmbH	B05CX10
Instruments:
Window access retractor SI	Estech	400-400
SI retractor blade 40W50L	Estech	400-172
Ceramo atraumatic forceps 2.8x15/350	Fehling	FE-MRA-3
Ceramo HCR valve forceps 3.0x15/350	Fehling	FE-MRA-0
Ceramo HCR needle holder 2x10/340	Fehling	FE-MRB-2
Ceramo TC HCR needle holder curved 3x10/340	Fehling	FE-MRG-9
Ceramo HCR valve scissors 350	Fehling	FE-MRA-7
Ceramo HCR curved scissors 350	Fehling	FE-MRA-6
Cygnet flexible arched aortic clamp	Vitalitec	V10143
Intrack insert set double traction	Vitalitec	N10122
Dissection forceps Carpentier	Delacroix-Chevalier	DC13110-28
Scissors Metzenbaum	Delacroix-Chevalier	B351751
Needle holder Ryder	Delacroix-Chevalier	DC51130-20
Dissection forceps DeBakey	Delacroix-Chevalier	DC12000-21
Lung retractor	Delacroix-Chevalier	B803990
Allis clamp	Delacroix-Chevalier	DC45907-25
O’Shaugnessy Dissector	Delacroix-Chevalier	B60650
18 blade knife	Delacroix-Chevalier	B130180
11 blade knife	Premiere	9311-2PK
Leriche haemostatic clamp	Delacroix-Chevalier	B86555
Data analysis
Mann-Whitney and Chi-square tests	GraphPad	Prism 7