Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy Joseph A

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Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy Joseph A. Dearani, MD, and Gordon K. Danielson, MD

ransaortic septal myectomy is currently considered to tion of the LVOT gradient is important so that a compar- Tbe the most appropriate surgical treatment for pa- ison can be made with postmyectomy measurements. tients with obstructive hypertrophic cardiomyopathy Standard cardiopulmonary bypass with mild to moderate (HCM) and severe symptoms unresponsive to medical hypothermia (30-34°C) is used and the left heart is vented therapy.1-18 However, there is a significant learning curve with a catheter inserted through the right superior pulmo- for this procedure, and early surgical experience was as- nary vein. Myocardial protection, especially important be- sociated with complications of complete heart block, ven- cause of the severe ventricular hypertrophy, is begun with tricular septal defect, injury to the aortic or mitral valves, a generous infusion of cold blood cardioplegia (800-1000 and incomplete relief of obstruction. Current surgical re- mL) into the aortic root followed by additional doses given sults are vastly improved, although the reported experi- selectively into the left and right coronary ostia every 20 ence in North America is limited to a few centers. minutes. For more complex and lengthy procedures, top- ical cooling with ice-cold saline is applied, and an insulat- Surgical Technique ing pad is placed behind the left ventricle. After the extended left ventricular septal myectomy is Over the last three decades, our technique of septal myec- performed, the resected area can be deepened with a ron- tomy has evolved from the classic Morrow myectomy (Fig geur. Direct inspection and digital palpation evaluate the 1A) to a more extended left ventricular septal myectomy adequacy and distal extent of the resection. The most com- (Fig 1B). mon reasons for residual gradients are inadequate septec- Intraoperative transesophageal echocardiography (TEE) tomy at midventricular level and overlooking anomalous is performed after induction of general anesthesia, with papillary muscles.17 In general, one can visualize the pap- particular attention to the cardiac anatomy, mitral valve illary muscles and chordae while looking through the aor- function, and appearance of the ventricular septum. Im- tic root after the myectomy has been completed. The left portant information obtained from TEE includes the max- ventricle is irrigated to remove any particulate debris and imum thickness of the septum, the distance of maximum the aortic and mitral valves are inspected to insure that thickness from the aortic annulus, the location of the en- there has been no injury to them. After the patient is docardial fibrous plaque (friction lesion), and the apical weaned from cardiopulmonary bypass, pressures are re- extent of the septal bulge. Exposure is gained through a measured in the left ventricle and aorta and TEE evalua- median sternotomy and pressures are measured in all four tion is repeated. TEE can quantify and localize any resid- cardiac chambers and aorta. If the right ventricular pres- ual LVOT gradient or mitral regurgitation and can exclude sure is elevated, pulmonary arterial pressure is also mea- any iatrogenic ventricular septal defect. If successful my- sured to evaluate possible right ventricular outflow tract ectomy has been performed, there will be little or no re- obstruction or pulmonary hypertension. If the left ventric- sidual gradient and little or no systolic anterior motion of ular outflow tract (LVOT) gradient is low (Ͻ30 mmHg) the anterior mitral leaflet. In general, we would resume because of the conditions under anesthesia, provocation cardiopulmonary bypass for further resection if the gradi- with an isoproterenol infusion is performed. Documenta- ent were greater than 15 to 20 mmHg. Transthoracic echo- cardiographic evaluation is routinely performed before Mayo Clinic, Rochester, MN. hospital discharge. Address reprint requests to Joseph A. Dearani, MD, Mayo Clinic, Section of Measurements and distances given in the figure legends Cardiothoracic Surgery, 200 First Street SW, Rochester, MN 55905. pertain to the adult patient (Figs 1-15).

Figure 1 Upper panel, Obstructive hypertrophic cardiomyopathy with basal and midventricular obstruction. (A) Classic Morrow procedure. (B) Extended septal myectomy. Note leftward extension that includes resection from the left ventricular free wall. White arrows indicate rightward and midventricular resections. The endocardial ﬁbrous plaque (friction lesion) shows the location of systolic contact of the anterior mitral leaﬂet with the septum. Lines in the basal septum represent fascicles of the left bundle originating from the membranous septum. 280 J.A. Dearani and G.K. Danielson

Figure 2 A transverse aortotomy is made and carried down toward the middle of the noncoronary sinus (dashed line). The aortotomy is carried to within 0.5 to 1.0 cm of the aortic annulus. Transaortic septal myectomy 281

Figure 3 A vein retractor is used to engage the right aortic sinus. Suspension sutures of pledgeted 4.0 prolene are placed a few millimeters above the aortic valve commissures to maximize exposure of the hypertrophied septum and anterior mitral leaﬂet. 282 J.A. Dearani and G.K. Danielson

Figure 4 Optimal visualization of the ventricular septum is facilitated by posterior displacement of the anterior wall of the left ventricle with a sponge forceps (arrow). A small Yankauer suction cannula is placed across the aortic annulus to retract the anterior mitral leaﬂet and papillary muscles posteriorly and rightward away from the ventricular septum. A closed forceps is used to retract the left coronary cusp. Inspection of the anatomy is performed including identiﬁ- cation of the friction lesion. For optimum accuracy, methylene blue can be used to mark the initial incision lines. Frequent repositioning of the sponge forceps and suction cannula is critical for maintaining exposure of the desired areas of resection. Transaortic septal myectomy 283

Figure 5 The vein retractor is moved to engage and protect the right coronary cusp from injury. The classical portion of the resection is begun by beginning the ﬁrst longitudinal incision at midventricular level (see inset) and extending it upward to within 8 to 10 mm of the nadir of the annulus of the right coronary cusp. It is important to leave 8 to 10 mm of muscle immediately below the aortic annulus to prevent subsequent development of cusp prolapse and aortic regurgitation. This is usually done with a #10 or #12 blade. Care is taken to begin this incision apically well below the friction lesion. Any incision made at the base of the ventricular septum more rightward than the nadir of the right cusp will injure the membranous septum and conduction tissue and result in complete heart block. RCC, right coronary cusp. (Traction sutures are omitted for clarity.) 284 J.A. Dearani and G.K. Danielson

Figure 6 A second longitudinal incision, parallel to the ﬁrst incision, is begun at the midventricular level and carried up to 8 to 10 mm below the plane of the aortic annulus at the commissure between the left and right cusps. The area to the left of this incision is left ventricular free wall. Transaortic septal myectomy 285

Figure 7 The two incisions are joined superiorly. The vein retractor is now moved to engage the aortic annulus in the trough where the two incisions were joined. A small rake retractor or hook (see Fig 10) can be used to engage the distal septum so that it can be pulled cephalad toward the aortic annulus. A deep wedge of left ventricular septum is then resected by beginning at the base of the septum and working toward the midventricle. In general, the thickness of the resected muscle is two-thirds the thickness of septum (as measured by prebypass TEE images), while ensuring that the retained septum is at least 1 cm thick. Retractors are moved accordingly to prevent injury to surrounding structures. This completes the classical portion of the resection. 286 J.A. Dearani and G.K. Danielson

Figure 8 (A) After the classical portion of the resection is completed, the resection is then extended leftward. Because the friction lesion, when present, represents the area of obstruction, it is important to include this in the resection whenever feasible. There is usually a bulge of muscle located between the commissure of the right and left cusps and the anterior mitral leaﬂet (within the dotted line). Improved exposure of this bulge can be accomplished by rightward traction with a Selman forceps. Hypertrophied muscle in this area is part of the left ventricular free wall. It is important to know the thickness of the free wall (obtained by TEE) to avoid excessive resection in this area with resultant perforation of the heart. (B) The completed leftward resection. It is important to also extend this resection down into the ventricle to the level of the bases of the papillary muscles. Transaortic septal myectomy 287

Figure 9 Exposure of the right side of the ventricular septum is facilitated by repositioning the sponge forceps on the outside of the heart, often near the acute margin of the right ventricle (black arrow). The suction cannula is again used to retract the mitral valve chordae and papillary muscles out of the way so that exposure of this rightward septum is optimized. 288 J.A. Dearani and G.K. Danielson

Figure 10 This ﬁgure demonstrates a close-up of the exposure of the rightward portion of the septum. There is 2.5 to 3.0 cm of muscle maintained below the level of the membranous septum, which is the location of the conduction tissue (inset). Engaging the distal aspect of the septum with a small rake or hook retractor can also facilitate exposure of this rightward portion of the resection. The septum is pulled cephalad toward the aortic annulus in addition to the sponge forceps pushing the septum from outside the heart. All bulging septal muscle apical to this area and rightward to the initial classical resection is resected, effectively making the trough much wider at the apex than at the base of the heart (inset). Transaortic septal myectomy 289

Figure 11 After the classical and extended portions of the resection are completed, inspection of the subvalvar apparatus for mitral valve abnormalities is performed. One of the more common abnormalities, which is depicted in this figure, shows the direct insertion of the head of the often large anterolateral papillary muscle into the anterior leaflet of the mitral valve. The muscle insertion site is frequently adjacent to the commissure of the mitral valve. In addition to direct insertion of the papillary muscle into the anterior leaflet, there is often concomitant fusion of the papillary muscle to the left ventricular septum or free wall. In addition to the extended septal myectomy as previously described, the papillary muscle is incised off the left ventricular septum or free wall down to its base (inset).19 This maneuver is important so that the papillary muscle can move out of the left ventricular outflow tract during systole and thus avoid creating LVOT obstruction. 290 J.A. Dearani and G.K. Danielson

Figure 12 This figure demonstrates examples of the many abnormal chordal and subvalvar attachments that can occur in the setting of hypertrophic cardiomyopathy. There can be fibrous attachments between the side of the anterior mitral leaflet and the ventricular septum or free wall. In addition, there can be additional (accessory) papillary muscles or chordae that join the anterolateral papillary muscle to the ventricular septum. These abnormalities are also addressed at the time of myectomy because they can contribute to LVOT obstruction because of the inability of the anterior leaflet and/or papillary muscle and subvalvar apparatus to move out of the LVOT during systole.

Figure 13 (A) This figure demonstrates the basic surgical principle that is applied to all of these abnormalities. It is important to maintain intact all attachments that come to the leading edge of the anterior mitral leaflet. This is shown in the box incorporating the leading edge of the anterior mitral leaflet. Any fibrous and/or muscular attachments that occur between the side of the anterior mitral leaflet or subvalvar apparatus that are attached to the ventricular septum or free wall are incised. This will not result in mitral regurgitation as long as all of the chordal attachments to the leading edge of the valve are preserved. Residual strands of fibrous connections are excised at the base of their site of origin so that small mobile chordae are not seen on the postmyectomy TEE examination. (B) Completed extended left ventricular septal myectomy in addition to resection of abnormal chordal attachments. Transaortic septal myectomy 291

Figure 14 This figure demonstrates an example of an accessory papillary muscle which arises from the ventricular septum. The fibrous attachments to the side of the anterior mitral leaflet can be seen. This muscle contributes to LVOT obstruction because of its presence in the LVOT throughout the cardiac cycle.

Figure 15 This accessory muscle is excised in its entirety. The ﬁbrous attachments to the side of the leaﬂet are cut and the papillary muscle is amputated at its base and removed (dotted line). All of these procedures with an abnormal subvalvar apparatus are done in conjunction with the extended left ventricular septal myectomy. Midventricular obstruction can also be a result of severe hypertrophy of the papillary muscles; additional resection is then performed by shaving the sides of the papillary muscles and resecting obstructing tissue around their bases. 292 J.A. Dearani and G.K. Danielson

Experience at the Mayo Clinic hypertrophic obstructive cardiomyopathy after transaortic myectomy. J Thorac Cardiovasc Surg 106:709-717, 1993 Since 1959, more than 700 patients have had septal my- 7. McCully RB, Nishimura RA, Tajik AJ, et al: Extent of clinical improve- ectomy for HCM at the Mayo Clinic. Data from a retro- ment after surgical treatment of hypertrophic obstructive cardiomyop- 18 athy. Circulation 94:467-471, 1996 spective review of 199 patients have been reported. Ages 8. Wigle ED, Rakowski H, Kimball BP, et al: Hypertrophic cardiomyopa- ranged from 2 months to 80 years (median, 45 years). thy: Clinical spectrum and treatment. Circulation 92:1680-1692, 1995 Preoperative NYHA class was III/IV in 120 patients (60%). 9. Schulte HD, Borisov K, Gams E, et al: Management of symptomatic Mitral valve regurgitation was moderate to severe in 108 hypertrophic obstructive cardiomyopathy: Long-term results after sur- patients (54%). Median resting LVOT gradient was 85 gical therapy. J Thorac Cardiovasc Surg 47:213-218, 1999 10. Robbins RC, Stinson EB: Long-term results of left ventricular myotomy mmHg. Ninety patients (45%) required additional cardiac and myectomy for obstructive hypertrophic cardiomyopathy. J Thorac procedures including division of abnormal mitral papil- Cardivasc Surg 111:586-594, 1996 lary muscle attachments (n ϭ 20), mitral valve replace- 11. Williams WG, Wigle ED, Rakowski H, et al: Results of surgery for ment (n ϭ 5), and other (n ϭ 65). Median intraoperative hypertrophic obstructive cardiomyopathy. Circulation 76:V104-V108, postmyectomy LVOT gradient was 4 mmHg. Postopera- 1987 12. Cohn LH, Trehan H, Collins JJ Jr: Long-term follow-up of patients tive mitral regurgitation was moderate in 16 patients (8%). undergoing myotomy/myectomy for obstructive hypertrophic cardio- Permanent heart block occurred in two patients (1%). No myopathy. Am J Cardiol 70:657-660, 1992 early deaths occurred in the 109 patients undergoing iso- 13. Heric B, Lytle BW, Miller DP, et al: Surgical management of hypertro- lated myectomy. There were three early deaths in patients phic obstructive cardiomyopathy. Early and late results. J Thorac Car- undergoing associated cardiac procedures (overall early diovasc Surg 110:195-206, 1995 mortality 1.5%). Follow-up in 178 patients (91%) ranged 14. McIntosh CL, Maron BJ, Cannon RO, III, et al: Initial results of com- bined anterior mitral leaflet plication and ventricular septal myotomy- up to 23 years (median, 4 years). Overall survival was 91 myectomy for relief of left ventricular outflow tract obstruction in pa- Ϯ 3% at 5 years and 83 Ϯ 4% at 10 years. Median resting tients with hypertrophic cardiomyopathy. Circulation 86;II60-II67, LVOT gradient on follow-up echocardiography in 121 pa- 1992 tients (68%) was 5 mmHg (Fig 7). Follow-up NYHA class 15. Krajcer Z, Leachman RD, Cooley DA, et al: Septal myotomy-myomy- was I/II in 127 patients (81%). ectomy versus mitral valve replacement in hypertrophic cardiomyopathy. Ten-year follow-up in 185 patients. Circulation 80:I57-I64, 1989 16. Merrill WH, Friesinger GC, Graham TP Jr., et al: Long-lasting improve- References ment after septal myectomy for hypertrophic obstructive cardiomyop- 1. McIntosh CL, Maron BJ: Current operative treatment of obstructive athy. Experience over 15 years. J Thorac Cardiovasc Surg 97:666-674, hypertrophic cardiomyopathy. Circulation 78:487-495, 1988 1989 2. Mohr R, Schaff HV, Danielson GK, et al: The outcome of surgical 17. Minakata K, Dearani JA, Nishimura RA, et al: Extended septal myec- treatment of hypertrophic obstructive cardiomyopathy: Experience tomy for hypertrophic obstructive cardiomyopathy with anomalous over 15 years. J Thorac Cardiovasc Surg 97:666-674, 1989 mitral papillary muscles or chordae. J Thorac Cardiovasc Surg 127: 3. Mohr R, Schaff HV, Puga FJ, et al: Results of operation for hypertrophic 481-489, 2004 obstructive cardiomyopathy in children and adults less than 40 years of 18. Dearani JA, Danielson GK: Obstructive hypertrophic cardiomyopathy: age. Circulation 80:191-196, 1989 (suppl 1) Results of septal myectomy, in Maron BJ (ed): Diagnosis and Manage- 4. Williams WG, Rebeyka IM: Surgical intervention and support for car- ment of Hypertrophic Cardiomyopathy. Elmsford, NY, Futura, an im- diomyopathies of childhood. Prog Pediatr Cardiol 1:61-71, 1992 print of Blackwell Publications, 2004, pp 220-235 5. Theodoro DA, Danielson GK, Feldt RH, Anderson BJ: Hypertrophic 19. Maron BJ, Nishimura RA, Danielson GK: Pitfalls in clinical recognition obstructive cardiomyopathy in pediatric patients: Results of surgical and a novel operative approach for hypertrophic cardiomyopathy with treatment. J Thorac Cardiovasc Surg 112:1589-1599, 1996 severe outflow obstruction due to anomalous papillary muscle. Circu- 6. Schulte HD, Bircks WH, Loesse B, et al: Prognosis of patients with lation 98:2505-2508, 1998