Surgical Myectomy and Associated Procedures: Techniques and Outcomes

Abstract

Patients with HCM and obstructive physiology who remain significantly symptomatic despite optimal medical management are candidates for septal reduction therapy. As surgical septal myectomy has been practiced for over 50 years, with current experience demonstrating excellent short- and long-term survival and minimal complications in experienced centers, this surgery has become the gold standard technique for relief of obstruction. Echocardiographic intraprocedural guidance is essential, as well as a team approach. Novel techniques and approaches continue to evolve to tackle more complex manifestations of the disease involving the mitral valve, apex, or mid-cavity, inclusive of papillary muscle abnormalities.

Questions

• 1. A 60-year-old man undergoes an uneventful septal myectomy and requires pacing while separating from bypass. The following day he is found to have third-degree heart block. What preoperative factor confers the highest risk for permanent pacemaker after septal myectomy?

  • A. AICD placement within 6 months prior to surgery

  • B. Septal thickness less than 20 mm on transesophageal echocardiogram

  • C. Right bundle-branch block on ECG

  • D. Paroxysmal atrial fibrillation

  • E. Family history of HOCM associated sudden death

  Answer: C. The incidence of permanent pacemaker requirement after septal myectomy is about 2–3%. In patients with relatively modest septal thickening, it may be advantageous to resect a shallow but broader segment of septum and even some posterior septum. That may predispose to complete heart block. However, since left bundle-branch block is almost always a consequence of septal myectomy, if the patient has a pre-existing right bundle-branch block, complete heart block and a requirement for a permanent pacemaker is almost a certainty.

• 2. A 54-year-old woman with LVOT gradient of 60 mmHg and septal thickness of 1.9 cm undergoes septal myectomy and resection of excess tissue at the base of her anterolateral papillary muscle. While separating from bypass, TEE demonstrates a significant left to right shunt. What is the most likely site of injury ?

  • A. The distal point of septal resection

  • B. Below the right coronary cusp of the aortic annulus

  • C. Base of the anterolateral papillary muscle

  • D. Proximal aspect of myectomy along the anterior leaflet of mitral valve

  • E. Posterior septum at attachment to free left ventricular wall

  Answer: B. Although it is possible to disrupt the ventricular wall with resection of muscle at the base of the anterolateral papillary muscle, that would lead to a free wall rupture into the pericardium. On the other hand, if the septum is minimally thickened and a broader myectomy is performed, it may extend into the membranous portion of the septum under the right coronary leaflet which is invariably very thin. This is the most common location for a VSD.

• 3. A 58-year-old man arrives in the recovery room following septal myectomy and has a new left bundle-branch block with heart rate 70 and blood pressure 90/40 mmHg, CVP 5, PA 25/15, and cardiac index 1.6. What is the best approach to initial management ?

  • A. Contact electrophysiology for urgent permanent pacemaker.

  • B. Bedside echocardiogram to assess for ventricular septal defect.

  • C. Initiate inotropic support with dobutamine.

  • D. Trial of pacing via temporary wires at rate of 90.

  • E. Administer 1 L crystalloid and initiate phenylephrine drip.

  Answer: E. Patients with HCM suffer with varying degrees of diastolic dysfunction due to myocardial fibrosis. It is not uncommon to have a low cardiac output state in the immediate post-op period. It is critical not to administer any inotropic support as this will further limit ventricular filling. Likewise, pacing at a faster rate would have the same effect. The PA pressure is too low to be consistent with a VSD. These patients almost invariably require higher filling pressures, especially in the immediate post-op period.

• 4. A 54-year-old woman with history of persistent atrial fibrillation and left atrial diameter of 52 mm and septal thickness of 20 mm. Which of the following is not a risk factor for mortality after isolated septal myectomy?

  • A. Female gender

  • B. Age 54

  • C. Preoperative atrial fibrillation

  • D. LA diameter 52 mm

  • E. Septal thickness 20 mm

  Answer: E. Age, gender, and atrial fibrillation are all risk factors for mortality in open-heart surgery in general. A dilated left atrium is usually the consequence of the atrial fibrillation. Although modest septal thickening may seem like a risk factor for creation of a VSD, that has not been shown to be true.

• 5. Which of the following best describes the role of AICD for patients undergoing septal myectomy?

  • A. AICD placement is recommended in all patients with EF <60% at time of septal myectomy.

  • B. After septal myectomy, AICD firing rate decreases to <0.5% per year.

  • C. Septal myectomy obviates the need for subsequent AICD placement.

  • D. Most AICD should be explanted at time of septal myectomy.

  • E. Patients with preoperative AICD have a threefold increase in the risk of postoperative VSD complicating septal myectomy.

  Answer: B. The need for AICD in patients with HCM is decided by predetermined criteria. Recent follow-up information would suggest that although there is a decrease in the firing of an AICD after a properly performed surgical myectomy, because myocardial fiber disarray persists in the remainder of the muscle, ventricular tachyarrhythmias can still occur with deadly consequences. Therefore, the current recommendation is to keep the AICD in these patients who fulfill criteria for their original implantation. A LVEF of <60% is not criteria, and there is no relationship between AICD placement and subsequent VSD.

• 6. A 60-year-old man with LVOT gradient of 60 mmHg, septal thickness of 26 mm, and class III heart failure undergoes septal myectomy. Five years later he is seen in follow-up with an LVOT gradient of 15 mmHg and class I heart failure. Which of the following is not an expected long-term benefit following septal myectomy compared to medical treatment?

  • A. Decreased risk of atrial fibrillation and left atrial size

  • B. Decrease in risk of sudden death to age- and sex-matched controls

  • C. Improvement in functional heart failure class

  • D. LVOT gradient <30 mmHg

  • E. Improved survival compared to asymptomatic or minimally symptomatic HOCM patients

  Answer: B. A properly performed septal myectomy with resolution of a resting and provocable gradient to near normal gives the patient a normal life expectancy. It would not improve the life expectancy beyond age- and gender-matched controls, nor would it eliminate the risk of sudden death from a ventricular tachyarrhythmia. That risk does, however, match a control population.

• 7. A 39-year-old woman undergoes septal myectomy and plication of the anterior leaflet of her mitral valve for LVOT gradient of 65 mmHg with septal thickness of 24 mm. A TEE is performed during weaning from bypass. Which of the following scenarios would be the least likely to prompt further investigation?

  • A. New onset mild tricuspid regurgitation

  • B. Inotrope-provoked gradient of 30 mmHg

  • C. Turbulent LVOT flow

  • D. 2+ mitral regurgitation

  • E. Left to right shunt at level of midventricular septum

  Answer: A. After septal myectomy, there should no longer be a resting or provocable gradient above 20 mmHg. Mitral insufficiency should also not be tolerated since that would be a consequence of either an inadequate operation or damage to the supporting mitral valve substructure. A VSD would also not be tolerated. Mild tricuspid insufficiency, on the other hand, may be a consequence of some RV dysfunction secondary to heart-lung bypass and usually is self-limiting in the postoperative period.

• 8. Which of the following is correct regarding anterior mitral leaflet plication during septal myectomy?

  • A. Most successful when redundant anterior leaflet height is less 20 mm in length.

  • B. Vertical plication is more technically challenging but allowed for greater reduction in postoperative SAM.

  • C. Horizontal plication preserves the zone of coaptation between leaflets.

  • D. Easiest to perform prior to distortion of anatomy resulting from septal myectomy.

  • E. Contraindicated in patients undergoing concomitant coronary artery bypass grafting.

  Answer: C. Although vertical plication has been described to be a useful tool in the surgical treatment of HCM, it has also been found to cause central mitral regurgitation in some cases due to malcoaptation of the leaflets. Horizontal plication is most easily accomplished after the myectomy, since visualization in the LV chamber is greatly improved. The anterior leaflet is usually in excess of 3.5 cm in length in cases where plication would be useful.

• 9. A 58-year-old man has severe midventricular obstruction from septal hypertrophy. Which of the following is correct regarding approach to this lesion?

  • A. Apical myotomy is a useful approach in patients with apical aneurysm.

  • B. Using a ventriculotomy approach, the septal wall can easily be distinguished from papillary muscles by identifying cordal attachments.

  • C. Midventricular obstruction cannot be fully resected via aortotomy.

  • D. Multiple layers of septal resection allows for the most accurate depth of resection.

  • E. Successful resection of midventricular hypertrophy prevents SAM without the need for additional mitral intervention.

  Answer: A. Although it is possible, it can be extremely challenging to resect adequate septal muscle in cases of midventricular obstruction through an aortotomy. If an apical aneurysm is present, it is helpful to approach these resections from both the apex and the aortotomy. In the approach through the apex, unless the aneurysm is very large, differentiating the septum from hypertrophied papillary muscle can be difficult. It is useful to do as much of a resection as possible through the aortotomy, then open the apex, and locate the site of resection and complete it apically. In general, patients with midventricular obstruction do not have SAM.

• 10. Which of the following patients would least likely benefit for septal myectomy?

  • A. A 50-year-old man with resting gradient 48 mmHg and recurrent syncope on disopyramide

  • B. A 60-year-old man with provoked gradient of 45 mmHg and resolution of chest pain on verapamil

  • C. A 72-year-old woman with provoked gradient of 55 mmHg and persistent dyspnea on metoprolol

  • D. A 26-year-old woman with exercise intolerance and resting gradient of 50 mmHg

  • E. A 45-year-old man on verapamil with intermittent chest pain that resolves with rest and a provoked gradient of 60 mmHg

  Answer: B. Patients undergoing surgical management for HCM must fulfill certain criteria. They must have a resting or provocable gradient of at least 50 mmHg, and they must be symptomatic. Control of symptoms and gradient with medication is not an indication for surgical management.

• 11. Known mitral valve anomalies in HCM do not include:

  • A. Anomalous papillary muscles

  • B. Elongated anterior mitral leaflet

  • C. Elongated posterior mitral leaflet

  • D. Thickened or fibrotic leaflets

  • E. Cleft leaflets

  Answer: E. A wide variety of mitral valve abnormalities can be present along with septal hypertrophy that can contribute to obstruction. Although some advocate for minimizing mitral valve manipulation in the surgical treatment of obstruction, some patients have such minimal septal hypertrophy that without addressing the mitral valve pathologies, obstruction and mitral regurgitation are likely to persist to a significant degree. Cleft leaflets, however, are not part of this pathology.

• 12. The “extended myectomy ” includes all of the features except:

  • A. Wide resection of the basal septum

  • B. Shaving of papillary muscle heads

  • C. Removal of lateral attachments

  • D. Transaortic exposure

  • E. Simple trough-like removal of septum

  Answer: E. The classic “morrow” myectomy traditionally consists of a trough resection roughly 1 cm wide, 1 cm deep, and about 3–4 cm long. As our understanding of the pathophysiology of obstruction has progressed, it is clear that a large proportion of patients require a wider and more extensive resection in order to allow for a more linear stream of outflow, thereby minimizing the risk of the “pushing force of flow” that catches the anterior leaflet of the mitral valve and propels it into the outflow tract.

• 13. Absolute indications for surgery for HCM include:

  • A. Enlarged LA and atrial fibrillation

  • B. Persistent symptoms despite maximal medical therapy

  • C. Gradient >30 mmHg

  • D. Severe mitral regurgitation

  • E. Moderate aortic insufficiency

  Answer: B. There are clear published indications for surgical management of outflow tract obstruction in the treatment of hypertrophic cardiomyopathy. There must be a gradient, either at rest or on provocation of >50 mmHg, and symptoms.

• 14. Absolute proven benefits of septal myectomy include:

  • A. Improved quality of life

  • B. Improved ejection fraction

  • C. Prevention of arrhythmias

  • D. Better long-term survival

  • E. Prevention of sudden death

  Answer: A. Although mid- to long-term follow-up would suggest that a well-performed surgical septal myectomy dramatically lowers the risk of sudden death, because muscle fiber disarray persists in the rest of the unresected myocardium, a risk of sudden death persists. These patients, in general, all have normal ejection fractions already, and unless a concomitant ablation procedure is indicated and performed, septal myectomy on its own does not limit atrial fibrillation.

• 15. The most common complication after myectomy surgery is:

  • A. Death

  • B. VSD

  • C. Pacemaker

  • D. Atrial fib

  • E. Stroke

  Answer: D. The risk of permanent pacemaker implantation after septal myectomy varies from 2% to 5% in published reports. Death, stroke, and VSD are extremely rare when myectomy is performed in referral center programs with large volumes. Atrial fibrillation occurs after septal myectomy in roughly the same incidence as any other open-heart surgical procedure – anywhere from 20% to 45%.

• 16. Common acceptable medications to be used after myectomy for HCM include:

  • A. Beta-blockers

  • B. Epinephrine

  • C. Norepinephrine

  • D. Dobutamine

  • E. Milrinone

  Answer: A. As these patients already have a degree of diastolic dysfunction from varying amounts of fibrosis and since the ejection fraction is almost always hyperdynamic, any inotrope (epinephrine, norepinephrine, dobutamine) administered in the immediate postoperative period would further limit ventricular filling and cardiac output. The same would be true for a peripheral vasodilating medication (milrinone) which would reduce afterload and promote ventricular emptying. Beta-blockade is usually always necessary after myectomy surgery both to improve ventricular relaxation and limit postoperative atrial fibrillation which tends to be poorly tolerated by HCM patients.

• 17. Surgical options in the presence of abnormal papillary muscles include:

  • A. Resection

  • B. Thinning

  • C. Repositioning within the left ventricle

  • D. Replacement of chordae

  • E. Cutting of chordae

  Answer: A. Although a great deal of procedures have been described to aid in moving the anterior leaflet of the mitral valve out of the outflow tract, the papillary muscles themselves cannot be completely resected without ultimately causing prolapse. Accessory attachments, however, can be considered for resection if there are other supporting structures.

• 18. The main difference between the lateral and horizontal plication of the AML is:

  • A. Number of stitches

  • B. Location of stiches

  • C. Shortening of the leaflet

  • D. Postop MR

  • E. Long-term changes to the valve

  Answer: C. Both lateral and horizontal plication have been described as successful ancillary procedures to help in gradient reduction in HCM surgery. Whereas lateral plication is thought to limit billowing into the outflow tract, horizontal plication both limits billowing and also shortens the leaflet in the A/P dimension, further limiting the leaflets’ ability to have SAM and subsequent obstruction. The number of stiches and location are inconsistent in both cases.

• 19. All of the following are related to transmitral resection techniques except:

  • A. Can be done minimally invasively

  • B. Require AML dislocation and resewing

  • C. Risk long-term changes to AML

  • D. Provide exposure to septum

  • E. Can cause aortic insufficiency

  Answer: E. Some have advocated transmitral access to the septum for myectomy and in small series published to date have shown good results. Others have not adopted this approach because septal access is relatively limited, and the current extended myectomy would be somewhat limited as a consequence. Additionally, this procedure requires dislocation of the entire anterior mitral leaflet. This has apparently not been a problem in short-term follow-up. However, given the relative young age of most patients, the concern remains that there may be long-term sequelae to this degree of manipulation of the AML. Since there is no transaortic access, there should not be any complications with the aortic valve in this approach.

• 20. Large retrospective studies have suggested that risk factors for HCM surgery include all of the following except:

  • A. Women

  • B. Age > 50

  • C. Atrial fibrillation

  • D. Concomitant surgery

  • E. Mitral regurgitation

  Answer: E. As is known in most other open-heart procedures, age, female gender, multiple procedures, and atrial fibrillation all increase the risk of surgery. Since almost all of these patients (HCM) have mitral insufficiency, that would not be an additive risk factor.