Cardiac Valve Operations Using a Partial Sternotomy (Lower Half) Technique

35 Cardiac Valve Operations Using a Partial Sternotomy (Lower Half) Technique Donald B. Doty, M.D., Jean H. Flores, R.N., and John R. Doty, M.D. Department of Surgery, Division of Cardiovascular and Thoracic Surgery, L DS Hospital, Salt Lake City, Utah, and The Johns Hopkins Hospital, Baltimore, Maryland ABSTRACT Background and Aim: Operations o n cardiac valves are being performed more frequently through smaller incisions t h a n traditional midline sternotomy. A variety of alternate incisions have been used, but m o s t of t h e interest appears to focus o n partial sternotomy. The purpose of t h e study w a s to review results using a partial l o w e r sternotomy for cardiac valve operations. Methods: A standard partial lower one-half or t w o - t h i r d s sternotomy was used for cardiac valve operations in 112 patients. The sternum w a s divided transversely in t h e third or second intercostal space and vertically f r o m t h a t p o i n t through the xyphoid process. Standard instruments and retraction devices were used. This incision provided adequate exposure for even complex operations t o b e performed. Small cannulae were placed i n t o t h e aorta and heart through t h e primary incision for cardiopulmonary bypass. Vacuum-assisted venous drainage w a s used. Results: Seventy-four single valve operations were performed. There were 35 double valve and 5 triple valve operations (35.4%) performed. Operative mortality (5.3%) and major complication rates were comparable t o f u l l t h e sternotomy approach. Conclusions: Partial sternotomy (lower half) provides a smaller incision through w h i c h virtually all cardiac valve operations may b e performed. Results achieved with t h i s approach are similar t o those associated with f u l l sternotomy. The smaller incision i s appreciated by patients. IJ Card Surg 2000; 15:35-42) There have been a number of reports describing a variety of incisions that are smaller than standard midline sternotomy for cardiac valve operations. Initial interest in performing cardiac valve operations through a minimal incision was stimulated by Port- Access (Heartport, Redwood City, CA, USA) technology applied experimentally.' It was shown that the mitral valve could be approached through a small right anterior thoracotomy incision when cannulation for cardiopulmonary bypass was done outside the thorax. Subsequently, several clinical series demon- Address for correspondence. Donald B Doty, M D , 324 Tenth Ave. #160, Salt Lake City. Utah 84301 Fax (801) 322-0567 strated the feasibility of this Costs of Port-Access operations, however, have gradually given way to operations performed via partial sternotomy technique^.^ Aortic valve operations have received more attention than mitral valve operations. The most popular incision for aortic valve procedures has evolved to a limited partial sternotomy. Usually the incision is made vertically through the upper one half or t w o thirds of the sternum for aortic valve operations with a number of variations for the transverse section of the sternum including a "T," "J," "C," or even " Z " shape incision,5-'l Parasternal incisions and transverse sternal incisions have been tried and mostly abandoned because of limited exposure, injury to the internal mammary a r t e r ies, and I ung he rn ia .6!' * , I 3 36 DOTY, ET AL. PARTIAL STERNOTOMY, CARDIAC VALVES Our experience using a smaller incision for cardiac valve operations began in March 1997, after 4 months of using a partial sternotomy for coronary artery bypass procedures. We were attracted to a lower one-half sternotomy with a small incision that would provide sufficient versatility that most, if not all, cardiac operations could be performed through a standard incision.14 Moreno-Cabrol15 published a letter in April 1997 describing a lower two-thirds sternotomy that confirmed the use of this approach. This useful incision has not gained much attention, however, among the multiple alternative incisions that have been used for minimally invasive cardiac valve procedures.16 This article presents the techniques and results of operations performed on cardiac valves at LDS Hospital, Salt Lake City, Utah using a partial lower sternotomy. MATERIAL A N D METHODS Operative technique A standard minimal incision is used for all operations on cardiac valves using a partial lower onehalf or two-thirds sternotomy. The patient's body habitus is studied after the patient is placed in the supine position for operation. The location of the J CARD SURG 2000;15:35-42 angle of Louis (second rib) and the second and third intercostal spaces are located. The length of the sternum is evaluated and the shape of the thorax observed. It is desirable to make an incision over the location of the cardiac valves and large enough to accommodate the surgeon's hand, should direct palpation of the heart be required. When the sternum is long and the patient's habitus is slender, dividing the sternum in the third intercostal space is sufficient for most cardiac operations. When the sternum is short or the body habitus is stocky or obese, a second intercostal transverse sternal incision provides better access. Complex valve operations such as the Ross procedure are easier to perform through a second interspace incision. Obviously, third interspace incisions are shorter and produce a better cosmetic result. Evaluation of the chest X-ray will confirm the extent of sternal division that will bring the incision over the heart and the cardiac valves and provide adequate access to the ascending aorta for cannulation for cardiopulmonary bypass. The chest X-ray is usually performed with the patient in the upright position and will likely present the heart in a lower position than when the patient is in the supine position (Fig. 1). Obtaining a supine chest X-ray may be more representative, but there Figure 1. Chest X-ray (normal, upright) showing position of the cardiac valves relative to the proposed sternal incision. A third intercostal space incision provides adequate access to all cardiac valves when the patient is lean body habitus. A second intercostal space incision provides better access for short stocky individuals or for complex operations. J CARD SURG 2000;15:35-42 will not be a lateral view to accompany the usual anterior to posterior view. The skin incision is made in the midline over the sternum extending from the selected interspace to near the end of the sternum. Considerable undercutting of the skin incision at the lower end may be done and still divide the xyphoid, but a t the upper end, the incision must be at or above the intercostal space selected for transverse section of the sternum. The pectoralis major and intercostal muscle are dissected away from the sternum in the second or third intercostal space on each side of the sternum to free the internal mammary vascular pedicle. The sternum is divided transversely at the selected intercostal space and vertically from that point through the xiphoid process using an oscillating saw. The upper one third or one half of the sternum, including all of the manubrium, remains intact. A small Kuyper-Murphy (Pilling-Weck Co., Ft. Washington, PA, USA) (Canadian type) retractor with 3-inch (7.6-cm) concave blades is used to separate the sternal edges. A Cheanvechai-Favalor0 Internal Mammary Retractor with Cheanvechai Swivel Rake Assembly (sharpened) attached to an L bar (Pilling-Weck Co.) is used to elevate the intact upper sternum to expose the underlying ascending aorta. The pericardial sac is opened from the diaphragm to the aortic reflection. The right pleural space is opened and the right lobe of the thymus is resected. Retraction stitches are placed on the pericardial edges to elevate the heart. A stab incision is made on the right side of the anterior chest midway between the clavicle and the nipple of the breast a t the midclavicular line. A 10 3/8-inch (26.4-cm) or a 12 1/2inch (31.8-cm) DeBakey aortic aneurysm clamp (Pilling-Weck Co.) is passed through the incision into the open right pleural space. The length of the clamp should be chosen so that the jaws will reach across the ascending aorta while the hinge is located in the chest wall. A second stab incision is made midway between the nipple and the costal margin on the right side of the chest at the mid-clavicular line. This site will serve as an exit point for the left heart vent and later on for the tube thoracostomy for drainage of the right pleural space. A 24-French thin wall, wire reinforced femoral perfusion cannula (TF-A-024-25; Baxter Research Medical, Salt Lake City, UT, USA) is inserted through standard pursestring suture into the ascending aorta at the usual location at the pericardial reflection through a small stab incision. DOTY, ETAL. PARTIAL STERNOTOMY, CARDIAC VALVES 37 If desired, this cannula may be inserted by needle guidewire technique for added safety, but this has rarely been necessary. Venous cannulation is by single two-stage cannula (29/37-French) or double cannulae 24-French bicaval technique (TF-V-024, Baxter Research Medical). A single cannula technique is used for aortic and aortic/mitral valve operations, while two cannulae are used for mitral, mitral/tricuspid, or triple valve operations. Active venous uptake is used in all cases using a vacuumassisted venous drainage system (Bentley-Baxter, Irvine, CA, USA). Cannulae for cardiopulmonary bypass are placed through the primary incision. The size of the cannulae are small enough to be unobtrusive. Cardiopulmonary bypass is established and the lungs are collapsed. A perfusion cannula is introduced into the coronary sinus for perfusion of cold cardioplegic solution retrograde through the coronary sinus. The aortic occlusion clamp is guided across the open right pleural space into the pericardial sac, placing the posterior blade of the occlusion clamp in the transverse sinus and the anterior blade in front of the aorta. The aorta is occluded. A 1O-French pediatric vent cannula @axter Research Medical) is placed through the right superior pulmonaryvein and advanced through the left atrium, across the mitral valve into the left ventricle. It is connected to suction drainage through the previously made stab site on the lower right chest. The aorta is vented by a needle or aortotomy. Cold blood cardioplegic solution is retrogradely administered through the coronary sinus to achieve total electromechanical arrest of the heart and to achieve a myocardial temperature < 10°C. Cardioplegia infusion is repeated every 20 to 30 minutes throughout the intracardiac procedure. Aortic valve operations Exposure of the aortic valve is accomplished by dividing the aorta above the sinotubular junction. Retraction stitches are placed just above each of the commissures. This rotates the aortic root anteriorly and elevates it for optimum exposure of the aortic root and its contents and the subaortic left ventricular outflow tract (Fig. 2). Mitral valve operations The mitral valve is exposed through the usual incision into the left atrium on the right side behind 38 DOTY, ET AL. PARTIAL STERNOTOMY, CARDIAC VALVES b Aortic Mitral J CARD SURG 2000;15:35-42 , Mitral and Tricuspid Figure 2. Cardiac incisions to expose cardiac valves. The aorta is divided for operations on the aortic valve. The mitral valve is approached through the usual right side left atriotomy. The aorta is divided and the left atrium opened superiorly for aortic and mitral valve procedures. A transeptal approach is used for mitral-tricuspid and triple valve operations. the intra-atrial groove (Fig. 2). A self-retaining retractor is used (T. Koros Surgical Instruments Corp., Moorpark, CA, USA). The lower partial sternotomy is centered over this cardiac incision. foramen ovale, dividing the septum from the inferior aspect of the left atrium to the superior aspect of the septum. The incision is extended over the superior aspect of the left atrium. The aorta is divided for triple valve operations. Cardiac valve operations performed through a partial lower sternotomy proceed as though being performed through a full sternotomy. The exposure is essentially the same though instruments I-inch (2.5-cm) longer are usually used because the surgeon can not get hands conveniently through the incision. Sutures are tied in the usual fashion, and a knot pusher is seldom required. Air is removed from the heart after the intracardiac repair in the usual fashion. Should cardiac defibrillation be required, it is accomplished with standard paddle electrodes or with pediatric paddles for convenience. Closure of the "T" incision is accomplished by wire sutures with the transverse section of the sternum immobilized and supported by a multistrand stainless steel cable (Pioneer Surgical Technology, Marquette, MI, USA) in a figure eight placed around the sternum in the interspace above and below the interspace where the sternum was divided transversely. Patients Aortic and mitral valve operations The aorta is divided above the sinotubular junction and retraction stitches are placed above the commissures of the aortic valve. The aortic valve is excised and the annulus prepared for valve replacement. The retraction stitches are used to retract the aortic root inferiorly. An incision is made in the superior aspect of the left atrium behind the aortic root (Fig. 2). With the aortic root retracted. inferiorly, the entire superior aspect of the left atrium is well exposed so that an incision of adequate length may be created, incising the left atrial appendage if necessary. Mitral/tricuspid and aortic/mitral/tricuspid vaIve operations A transseptal approach is used (Fig. 2). A right atriotomy parallel to the atrioventricular groove is made and the coronary sinus perfusion catheter inserted under direct vision. The right atriotomy is continued medial to the right atrial appendage to the septum and the left atrium behind the aorta. The atrial septum is incised vertically through the There were 113 cardiac valve operations performed in 112 patients through a partial sternotomy (lower half) from March 6, 1997 until December 10, 1999. The patient population (46 women, 66 men) ranged in age from 18 to 87 years (mean 59 years). All operations were primary except for one patient who returned for reoperation for endocarditis, and the partial sternotomy was reentered. RESULTS All operations were performed via the partial sternotomy and are listed in Table 1. There were 73 single valve operations performed. Forty-two patients had aortic valve replacement of which 12 (27.9%) were with coronary artery bypass grafts. Twenty-nine patients had single mitral valve operations, 24 (82.7%) of which were repair procedures. There was a single pulmonary valve and a single isolated tricuspid valve procedure. There were 35 double valve operations. Aortic valve replacement with pulmonary autograft (Ross procedure) was performed in 19 patients. This pro- J CARD SURG 2000;15:35-42 DOTY, ET AL. PARTIAL STERNOTOMY, CARDIAC VALVES ~~~ 39 ~~ TABLE 1 Cardiac Valve Operations Performed Using a Partial Sternotomy Operation Number Mortality 30 day (n) Age, Year Mean (range) 46 ~ Single valve Aortic valve replacement Aortic valve replacement + CABG Mitral valve replacernent Mitral valve repair Tricuspid valve repair Pulmonary valve replacement Double valve Aortic/pulmonary (Ross Procedure) Aortic/m it ra I AorticRricuspid Mitral/tricuspid Triple valve Aoitictmitralltricuspid Total 30 12 5 24 1 1 69 (40-87) 72 (59 83) 66 (53-71) 65 (18-77) 83 42 2 1 0 0 19 12 1 3 37 (20-66) 46 (37-66) 67 64 (63-65) 1 1 0 0 5.3 8.3 0 0 5 113 41 (33-66) 59 (1 8-87) ~- 0 6 0 5.3 1 0 67 83 0 0 100 0 CABG = coronary artery bypass graft. cedure is performed for isolated aortic valve disease, but is included as a double valve operation because the pulmonary trunk must also be replaced with a pulmonary homograft. There were 16 other double valve operations. Triple valve operations were performed in five patients. It was not necessary to extend the incision to a full sternotomy in any patient. The incision was certainly more limited compared with full sternotomy, at times making the operation tedious and challenging but exposure of the cardiac valves was not compromised. No patient died in the operating room. Six (5.3%) patients died after operation within 30 days. Five of the six deaths occurred in association with an aortic valve procedure. There were no deaths following mitral valve operations. Three patients died after aortic valve replacement. One patient had respiratory insufficiency after operation and developed pneumonitis and sepsis with multiorgan failure. One patient had a cerebral injury and died subsequently. A third patient had a routine recovery until cardiac arrest occurred on postoperative day 8 from which he could not be resuscitated. One patient died after the Ross procedure due to cerebral injury accompanying intraoperative hemorrhage, prolonged cardiopulmonary bypass, and postoperative requirement for left and right ventricular assist device. One patient had exigent hemorrhage after operation requiring opening of the wound in the intensive care unit. He died subsequently of ischemic cerebral injury. One 83-year-old patient died of sepsis after removal of an infected pacemaker electrode and tricuspid annuloplasty for endocarditis. Complications associated with operation in patients having partial sternotomy for cardiac valve procedures are listed in Table 2. These complications and their frequency are what would be expected with cardiac valve procedures. COMMENT It is now possible to perform almost all cardiac valve operations through smaller incisions than standard midline sternotomy. Experience and familiarity with smaller incisions has shown that exposure of cardiac valves is not compromised, and even though the smaller incision provides more confined dimensions within which the surgeon must work, results have been equivalent with operations performed through standard exposures. The frequency of application of the minimally invasive approach to cardiac valves has increased, but still remains a small fraction of the total. The Society of Thoracic Surgeons National Adult Cardiac Surgery Database has shown steady growth of the percent of minimally invasive cardiac valve procedures.17 For isolated aortic valve replacement, 8.0% of the operations were attempted by the minimally invasive approach. For isolated mitral valve replacement, 7.0% were minimally invasive procedures. DOTY, ET AL. PARTIAL STERNOTOMY, CARDIAC VALVES 40 _ _ _ J CARD SURG 2000;1535-42 ~- TABLE 2 Major Complications Complication Number of Patients 40 6 4 9 5.3 3.5 Death within 30 days Bleeding, serious intraoperative or reoperation Low cardiac output syndrome Respiratory insufficiency/pneumonitis Renal failure Central nervous system injury Endocarditis Dehiscence of bioprosthesis Heart block and/or pacemaker insertion Atrial fibrillation The lower one-half partial sternotomy approach may be considered for any cardiac valve operation. This approach has allowed the minimally invasive operation in not only isolated single valve replacement but also in complex cardiac valve operations. The incision is centered over the location of the cardiac valves (Fig. 2). Cadaveric dissections performed by Reardon and associates18 confirms the lower one-half sternotomy exposure. They found the pulmonary valve behind the third left costal cartilage, the aortic valve behind the sternum opposite the third intercostal space, and the mitral and tricuspid valves related to the fourth costal cartilage and fourth interspace. Operations on the aortic valve are facilitated by dividing the ascending aorta above the sinotubular junction. The aortic root may then be positioned for direct visualization, allowing precise examination. The mitral valve approach through standard left atriotomy posterior to the intra-atrial groove on the right side is comfortable and familiar to the surgeon. When aortic and mitral valve operations are combined, the mitral valve is easily accessible through the superior aspect of the left atrium, especially with the aorta divided and the aortic root retracted inferiorly. A transatrial septa1 approach is used when the mitral valve is repaired or replaced in conjunction with operations on the tricuspid valve or for triple valve operations. Complex operations such as aortic valve replacement with pulmonary autograft (Ross procedure) are possible using the lower partial sternotomy. Complex operations are easier when the transverse section of the sternum is through the second intercostal space. The ascending aorta may be replaced through this incision, but operations on the aortic arch are likely to be difficult and any added time working in the arch would not be jus- 3 3 4 1 2 9 10 7.9 2.6 2.6 3.5 0.9 1.8 7.9 8.8 tified in the interest of a smaller incision. Although others have used an upper partial sternotomy for arch reconstruction, we would not recommend using an incision smaller than full midline sternotomy. Similarly, when it is anticipated that the operation will involve working in the left ventricle below the plane of the mitral valve annulus, like for attachment of papillary muscles during mitral valve replacement with homograft, we recommend full sternotomy. The patient‘s body habitus considerably influences the incision. A short sternum or deep thorax suggests a second interspace location for the transverse section of the sternum. Operations through lower partial sternotomy are always easier when the second interspace approach is used. Obviously, the longer the sternal incision, the less the incision qualifies as “minimally invasive.” Nevertheless, it is not wise to compromise exposure or needlessly confine the incision to the point that the operation becomes tedious and prolonged. When the third or second interspace is used, the entire manubrium remains intact, along with the clavicular attachment. This should be of substantial benefit to the patient in terms of chest wall stability after operation and eliminate the possibility of dehiscence of the sternal repair a t the manubrium. Initially, w e thought that obesity would be a deterrent to the use of a small incision for cardiac valve operations. On the contrary, we now think that obese patients may be aided by leaving the manubrium of the sternum intact, as they depend substantially on upper body strength for mobility. In obese patients, w e always use a second interspace transverse division of the sternum. Closure of the transverse section of the sternum supported by a figure eight stainless steel cable has greatly improved the stability of this repair. J CARD SURG 2000;15:35-42 Small diameter cannulae have been developed that considerably aid placement of aortic and venous cannulae through the primary incision. The addition of vacuum-assisted venous drainage has also been helpful, allowing not only smaller venous uptake cannulae to be used but also by providing more reserve and safety in the venous drainage system to the reservoir of the oxygenator. It is our impression that the right heart remains empty and collapsed more consistently than with gravity drainage and that air entrainment with air lock, frequently seen with gravity drainage, is eliminated. Air entrainment with a vacuum-assisted system becomes a nuisance that is dealt with leisurely rather than an urgent problem that interrupts the operation when venous drainage is by gravity. These advances in the conduct of cardiopulmonary bypass are transferrable to all cardiac operations regardless of the size of the incision. In addition, Port-Access technology can be used directly through the i n c i ~ i o n . ’ ~ There are several reports suggesting that smaller incisions lessen surgical morbidity and procedural co~t.5,6.7.13,~3-2* Szwerc and associates23 compared partial upper sternotomy to median sternotomy for aortic valve replacement and found comparable results. They showed that partial sternotomy offered a cosmetic benefit but did not reduce pain, length of stay, or cost. They also called attention to the fact that upper sternotomy does not provide access to the heart other than at the aorta and at the base. This cardiac access problem is overcome by lower partial sternotomy that centers the incision over the heart. Port-Access technology has also been used directly through the incision for endoluminal clamping of the aorta.24 Arom and associates4 compared Port-Access to less invasive procedures in which a small incision is made but the aorta and atria are cannulated directly. They found that the Port-Access procedures required more operating room time, longer surgery and cross-clamp time, and more cost than the less invasive procedures. It seems that their experience concurs with many other surgeons so that the trend in cardiac valve operations is toward direct cannulation of the aorta and heart when small incisions are used. Noted also in this series is that less invasive procedures were applied almost exclusively in isolated cardiac valve procedures. Port-Access was applied in 80% of mitral valve procedures while less invasive techniques were used for 76% of aortic valve operations. Only DOTY, ET AL. PARTIAL STERNOTOMY, CARDIAC VALVES 41 3% of patients had a doubte valve procedure in the less invasive group. This is in contrast to this series using a lower one-half sternotomy in which 35.4% of the operations were complex doubte and triple valve procedures. Thus, the approach described in this article would indicate that in fact, virtually any cardiac valve operation may be performed through a partial lower sternotomy. Data is not presented, however, to justify the approach on the basis of cost, length of stay, decreased pain, and so on. It is our impression that in a diverse patient population it is the actual operation, the age of the patients, and other comorbid factors that influence outcomes, frequency of complications, and costs. Complications associated with operations performed through a lower one-half sternotomy appear to be consistent with what would be expected in similar operations performed via midline sternotomy. The Society of Thoracic Surgeons National Adult Cardiac Surgery Database shows major complication rates in 1998 of 15.8% for isolated aortic valve replacement and 19.6% for isolated mitral valve surgery. Complications reported in this series are equivalent or less than those reported by the Society of Thoracic Surgeons National Adult Cardiac Surgery Database. Except for one, all of the operations performed in this series were primary procedures. We did not use partial sternotomy preferentially when patients had previous cardiac valve operations performed through a full midline sternotomy. We preferred to reopen the previous sternotomy incision. Byrne and associatesz4 have reported use of a partial upper hemisternotomy for reoperative aortic valve replacement. They found operative bleeding and operating time were reduced compared to standard full sternotomy during reoperations, and that perhaps this approach should be considered when reoperation is required. In conclusion, partial sternotomy (lower half) provides a smaller, less invasive incision through which essentially all cardiac valve operations may be performed. Standard exposure to the cardiac valves is provided. Standard instruments and retraction devices are used. Advances in cardiopulmonary technology have made operating through a small incision easier and the technology is transferrable to full sternotomy Operations. Maintaining the integrity of the manubrium and upper sternum should be beneficial for patient mobilization and rehabilitation after operation. 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