Alcohol septal ablation versus surgical myectomy: a ...

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Alcohol septal ablation versus surgical myectomy: a patient with obstructive HCM Giovanni La Canna*, Flavio Airoldi, Elvia Capritti, Antonio Grimaldi, Antonio Colombo and Ottavio Alfieri

Vanderbilt Continuing Medical Education online

SUMMA RY Background A 42-year-old woman with a 20-year history of obstructive

hypertrophic cardiomyopathy was referred for alcohol septal ablation following a worsening of symptoms, which had persisted despite medical treatment. Investigations Physical examination, electrocardiography, rest–exercise Doppler and two-dimensional echocardiography, coronary angiography, intracoronary myocardial contrast echocardiography, and intraoperative transesophageal and epicardial echocardiography. Diagnosis Symptomatic obstructive hypertrophic cardiomyopathy. Management The patient was deemed unsuitable for alcohol septal ablation and underwent surgical myectomy guided by intraoperative echocardiography. keywords alcohol septal ablation, myocardial contrast echocardiography, obstructive hypertrophic cardiomyopathy, surgical myectomy

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G La Canna is Director and E Capritti and A Grimaldi are Assistant Directors of the Echocardiography Unit of the Cardiac Surgery Department, F Airoldi is Assistant Director and A Colombo is Director of the Catheterization Laboratory, and O Alfieri is Professor of Cardiac Surgery and Chief of the Cardiac Surgery Department, at the Vita-Salute San Raffaele University, Milan, Italy. Correspondence *Echocardiography Unit, Department of Cardiac Surgery, San Raffaele University Hospital, Via Olgettina 60, 20132 Milan, Italy [email protected] Received 21 February 2007 Accepted 15 June 2007 www.nature.com/clinicalpractice doi:10.1038/ncpcardio0988

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This article offers the opportunity to earn one Category 1 credit toward the AMA Physician’s Recognition Award.

THE CASE

A 42-year-old woman with obstructive hypertrophic cardiomyopathy (HCM) was referred for alcohol septal ablation (ASA). She had been diagnosed with HCM 20 years earlier following presentation with recurring exertional syncope. Echocardiography of her mother and sister showed HCM in both these individuals, but there was no family history of sudden cardiac death. The patient’s general quality of life had been good, including a normal pregnancy, but a year before her referral she had developed exertional dyspnea and paroxysmal atrial fibrillation, which persisted despite treatment with 200 mg/day amiodarone. Six months before referral for ASA, non­sustained ventricular tachycardia was recorded on 24 h Holter monitoring, and, as a consequence, the patient was fitted with an automatic implantable cardioverter-defibrillator at another hospital. Despite increased medical treatment (with metoprolol, verapamil and disopyramide), the patient’s symptoms continued to limit her quality of life, and she was referred for ASA. On admission for the procedure, clinical examination of the patient revealed a systolic murmur along the left sternal border and apex. Electrocardiography revealed a normal sinus rhythm, left ventricular (LV) hypertrophy, and inverted strain T-waves in the lateral leads. Echocardiography showed a nondilated hypertrophic left ventricle with no primary valvulo­ pathies. Systolic anterior motion of the mitral valve leaflets (SAM) and anterior mal­­positioning of the lateral papillary muscle (LPM) were evident, both resulting in systolic contact with the septum (Figure 1). The complete findings of twodimensional and Doppler echo­cardiography in the patient are summarized in Box 1. The septal thickness, measured at the zone responsible for the LV obstruction, was 20 mm—making the patient eligible for either surgical myectomy or october 2007 vol 4 no 10

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A

B

TZ

AV

D

C

Figure 1 General features of the patient’s obstructive hypertrophic cardiomyopathy at the time of referral for alcohol septal ablation. (A) Two-dimensional transthoracic echocardiogram (apical long-axis view) showing asymmetrical septal hypertrophy and systolic contact of the septum with both the SAM (dotted arrow) and the PM (solid arrow) , at distances of 4.5 cm and 2.5 cm, respectively, from the aortic valve plane. The dotted line denotes the area that is responsible for the LV obstruction—the target zone for either ASA or surgical myectomy. (B) Continuous Doppler echocardiogram demonstrating a baseline intraventricular pressure gradient of 60 mmHg. (C) Left ventricular angiogram (right anterior oblique view) showing typical systolic obliteration of the left ventricle. (D) Simultaneous recordings from the mid-left ventricular cavity and the aorta, showing a varying pressure gradient. Abbreviations: AO, aorta; ASA, alcohol septal ablation; AV, aortic valve; LV, left ventricular; PM, papillary muscle; SAM, systolic anterior motion of the mitral valve leaflets; TZ, target zone.

ASA. She was informed of the advantages and risks of both procedures, and chose ASA. Left coronary angiography showed three septal branches seemingly supplying the ASA target zone. Intracoronary myocardial contrast echocardiography (MCE) was performed with 300 mg/ml Levovist® (a galactose-based contrast agent; Bayer Schering Pharma, Berlin, Germany), which was injected through the central lumen of the occluded balloon catheter during transthoracic echocardiography monitoring in the harmonic imaging mode (Figure 2). Injection of Levovist® into the first coronary septal branch resulted in opacification of the right side of the septum outside the target zone, and the balloon catheter was removed. After cannulation of the second septal branch, MCE showed minimal

opacification in the mid-septum at the point of contact with the anterior papillary muscle, and the appearance of contrast in the LV cavity. The LV gradient remained unchanged after probatory balloon occlusion of both the first and second septal branches. Cannulation of the tortuous third septal branch was unsuccessful. These MCE findings indicated that the coronary septal branches did not accurately supply the target zone. Alcohol injection could, therefore, fail to cover the lesion effectively, and induce damage outside this target area. In light of this finding, ASA was aborted, and the patient was referred for surgical treatment of LV obstruction. Intraoperative transesophageal and epi­cardial echocardiography were used to delineate the target site and to measure the distance of the LV

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Box 1 Echocardiography findings from the patient at the time of referral for alcohol septal ablation. 2D echocardiography ■ Asymmetrical hypertrophy of the left ventricle extending to the infundibular right septum, with maximal hypertrophy of the interventricular septum and the LV anterolateral free wall and apex ■

Septal–SAM contact at 2.5 cm from the aortic valve plane



Anterior malpositioning of the LPM, making systolic contact with the septum at 4.5 cm from the aortic valve plane



RVOT hypertrophy



Left atrial enlargement (anteroposterior diameter 48 mm, volume 100 ml)

Color Doppler flow mapping ■ High velocity intraventricular flow at the points of septal–SAM and septal–LPM contact ■

Moderate SAM-related mitral regurgitation (grade 2), with jet towards the lateral left atrial wall

Continuous Doppler echocardiography At rest ■ Intraventricular pressure gradient of 60 mmHg, increasing during inspiration (to 80 mmHg) and the Valsalva maneuver (to 70 mmHg) ■

No RVOT pressure gradient

At exercisea ■ Limiting dyspnea ■

Systemic arterial hypotension (systolic pressure decreased from 120 mmHg to 90 mmHg)



Increased LV pressure gradient during recovery phase (100 mmHg)



Increased SAM-related mitral regurgitation, from moderate to severe (grade 2 to grade 4)



Severe pulmonary hypertension (55 mmHg, vs 30 mmHg at rest)



No RVOT pressure gradient

aObservations are at exercise peak. A cycle ergometer was

used with 10 W/min load increase, and exercise was stopped at 60 W/min owing to limiting dyspnea. Abbreviations: 2D, two-dimensional; LPM, lateral papillary muscle; LV, left ventricular; RVOT, right ventricular outflow tract; SAM, systolic anterior motion of the mitral valve leaflets.

obstruction from the aortic valve plane, and the corresponding septal thickness. Accordingly, the surgeon performed a myectomy with a transmural depth of 10 mm and a longitudinal extension of 45 mm, which involved the point of septal contact with both the SAM and the LPM (Figure 3). The patient also underwent surgical ablation for atrial fibrillation. Post-pump echocardiography confirmed complete relief of 572 nature clinical practice CARDIOVASCULAR MEDICINE  © 2007 Nature Publishing Group

the LV obstruction, without residual mitral or aortic regurgitation. Six months later the patient was symptomfree. Transthoracic echocardiography showed an enlarged LV outflow tract without obstruction (either at rest or on provocation) and a steady sinus rhythm. DISCUSSION OF DIAGNOSIS

HCM is an autosomal dominant genetic disorder characterized by abnormalities in the structure and function of cardiac sarcomere.1 A diagnosis of HCM is made with the use of echo­cardiography, which typically demonstrates hypertrophy of the left ventricle with no apparent cause and no signs of storage syndrome.1,2 The septum is generally more affected than the posterior or free wall of the left ventricle, although any pattern can occur, including symmetrical, mid­ventricular or apical hypertrophy, and extended or isolated right hyper­ trophy. Left ventricular hypertrophy can also be asymmetrical, as in the patient reported here. Approximately 30–70% of patients with HCM show a resting or provocable intra­ventricular pressure gradient, with or without SAM.2,3 Mitral regurgitation occurs in almost all patients, owing to SAM-related leaflet malcoaptation. LV obstruction in HCM arises from varying degrees of myocardial hypertrophy, either with or without anatomical or functional abnormalities of the mitral valve apparatus (Box 2). For a complete review of the mechanisms of HCM, see Elliott and McKenna1 and Maron et al.2 Varying clinical presentation can be observed with HCM. The disease has a silent clinical course in many patients and might only be discovered during opportunistic or family echocardiographic screening. Nevertheless, HCM can cause severe symptoms, including unexpected sudden cardiac death. Following the syncope that led to diagnosis in this patient, her disease remained clinically silent for 19 years until the development of dyspnea and paroxys­mal fibrillation 1 year before her admission for ASA. The initial diagnosis of HCM was supported by the patient’s family history and by echo­ cardiographic evidence of unexplained LV hypertrophy. LV obstruction was evident, and was caused by systolic contact of both the SAM and the LPM with the hypertrophied septum. At the time of referral for ASA the patient had developed limiting dyspnea and maladaptive hemodynamics, including pulmonary hyper­ tension and systemic arterial hypotension, which LA CANNA ET AL. october 2007 vol 4 no 10

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A

C

E

1° 1°



2° 3°

B

D

F

LV PM RV RV

SAM AV

Figure 2 Intracoronary myocardial contrast echocardiography in the harmonic imaging mode demonstrated that the patient was unsuitable for alcohol septal ablation. (A) Left coronary angiogram showing the three septal branches (arrows) that potentially supply the target zone (dotted line)—the area of septal contact with the SAM (arrow) and the PM (B). Note the tortuosity of the third septal branch, which was unsuitable for cannulation. (C) Left coronary angiogram and (D) Myocardial contrast echocardiogram following injection of contrast into the first septal branch (arrow). The right side of the septum is opacified (dotted line) outside the target zone, precluding this branch as a possible route for alcohol injection. (E) Left coronary angiogram and (F) myocardial contrast echocardiogram following injection of contrast into the second septal branch (arrow). There is minimal opacification (dotted line) of the septum inside the target zone, suggesting that this branch was also unsuitable for alcohol injection. Abbreviations: AV, aortic valve; LV, left ventricle; PM, papillary muscle; RV, right ventricle; SAM, systolic anterior motion of the mitral valve leaflets.

were caused by an increase in LV obstruction and SAM-related mitral regurgitation. TREATMENT AND MANAGEMENT

The main objectives of HCM management are to relieve cardiac symptoms and to prevent sudden death. LV obstruction has recently been identified as a predictor of an unfavorable clinical course.4,5 Nonpharmacological treatment of HCM, such as surgery or ASA, is needed in patients with an LV outflow gradient greater than 50 mmHg either at rest or during exercise and with symptoms refractory to optimum medical therapy. To optimize the treatment of obstructive HCM, clinicians should carefully address the obstruction mechanisms, exclude primary causes of mitral regurgitation, and measure the thickness

Box 2 Different pathophysiological mechanisms for left ventricular obstruction in hypertrophic cardiomyopathy.a ■

SAM-related: arising from septal contact with the SAM, leading to dynamic mitral regurgitation.



SAM-free: caused by septal contact with a malpositioned or aberrant papillary muscle, abnormal insertion of the papillary muscle into the left ventricular outflow tract, or mid-ventricular or apical obliteration due to massive hypertrophy.

aBoth

SAM-related and SAM-free mechanisms can coexist in the same patient (as in the case described here), with variation in the septal thickness and distance from the aortic valve plane. Abbreviation: SAM, systolic anterior motion of the mitral valve leaflets.

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A

B IS

AV LVOT

MV LA

PW

C

D IS AV LVOT MV PW

LA

E

Figure 3 Deemed unsuitable for alcohol septal ablation, the patient instead underwent surgical myectomy guided by echocardiography. (A) Preoperative epicardial echocardiogram (parasternal-equivalent long-axis view) demonstrating the thickness of the interventricular septum in the target zone (20 mm) and the distance of septal contact with the PM (4.5 cm; solid arrow) and SAM (2.5 cm; dotted arrow) from the AV plane. Blue dots represent 1 cm intervals. (B) Preoperative continuous Doppler echocardiogram demonstrating a pressure gradient of 85 mmHg across the LVOT. (C) Postoperative epicardial echocardiogram showing successful remodeling of the LVOT following elimination of septal contact with the SAM and the PM—leading to a reduction in related mitral regurgitation. (D) Postoperative continuous Doppler echocardiogram showing no residual interventricular pressure gradient. (E) Photograph of the surgically excised portion of the septum. Abbreviations: AV, aortic valve; IS, interventricular septum; LA, left atrium; LVOT, left ventricular outflow tract; MV, mitral valve; PM, papillary muscle; PW, posterior wall; SAM, systolic anterior motion of the mitral valve leaflets.

of the septum in the target zone—the area responsible for LV obstruction. The choice of appropriate nonpharmaco­logical treatment for obstructive HCM is increasingly becoming a challenge for both cardiologists and surgeons.6,7 Surgical myectomy is regarded

as first-line treatment for symptoms caused by resting or provocable LV obstruction. Principally, myectomy aims to eliminate mitral–septal contact and associated mitral regurgitation by remodeling the LV outflow tract. Data accumulated over 40 years show that myectomy reduces

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obstruction-related symptoms effectively and is associated with low mortality, with outcomes being dependent on patient selection and the skill of the surgical team.2,6,7 Published reports have also demonstrated that patients with obstructive HCM who underwent myectomy had an improved life expectancy (comparable with that of the general population) and a reduced risk of sudden death compared with those who were treated pharmacologically.8 A septal thickness of at least 18 mm in the culprit zone is regarded as being the anatomic threshold at which myectomy can be performed without complications. Intraoperative echocardiography is an important guide for determining the transmural and longitudinal extension of myectomy, which depend on the septal thickness and the distance from the aortic valve plane of the septal contact with the SAM or the LPM. In patients with primary valve abnormalities or minimal septal hypertrophy in the target zone, mitral valve repair or replacement should be carried out.6 We believe that physicians should begin to consider using ASA to relieve LV obstruction in patients who are anatomically suitable for myectomy, taking advantage of the percutaneous approach and short hospital stay.6 ASA involves the injection of alcohol into the coronary septal branch that supplies the target zone, inducing myocardial damage and mimicking the results of surgical myectomy. To select the appropriate artery, the characteristics of the septal coronary anatomy (its origin, size and distribution), the LV obstruction mechanisms, and the size and site of septal thickness in the target zone, must all be considered. ASA can relieve the obstruction through a biphasic mechanism—it causes a postischemic loss of septal contractility in the short term, followed by remodeling of the LV outflow tract as a result of septal scarring. Consequently, long-term observation is required to evaluate the effectiveness of ASA.9 In patients who are referred for ASA, accurate targeting of the correct area of the septum will maximze the effects on LV obstruction, while avoiding necrosis-related compli­cations both inside and outside the culprit zone (Figure 4). Common periprocedural complications of ASA include right-bundle-branch block and atrio­ventricular block, for which pacemaker implantation is required in 10% (range 0–40%) of patients.10 ASA can also lead to threatening necrosis involving the papillary muscle, LV free wall or right ventricle. The true rate of fatal

2D echocardiography

Identification of LV obstruction site and mechanisms (SAM-related/SAM-free) in order to delineate the target zone

Septal thickness in the target zone ≥18 mm

Septal thickness in the target zone