Surgical Treatment of Hypertrophic Obstructive Cardiomyopathy

*Francesca Nicolo', Antonio Lio, Marina Comisso, Romina Pantanella, Roberto Scrofani and Francesco Musumeci*

### **Abstract**

Hypertrophic cardiomyopathy is a genetic disorder of the myocardium, characterized by marked myocardial hypertrophy that may lead to the development of symptoms such as dyspnea, angina pectoris, or stress-induced syncopes, with an increased risk of sudden cardiac death, due to obstruction of the left ventricular outflow tract (hypertrophic obstructive cardiomyopathy). Septal reduction treatment is needed in these patients, in order to relieve of the symptoms. In addition, mitral valve apparatus should be assessed in these patients, in order to recognize a dynamic movement of the MV during systole anteriorly toward the LVOT. In this chapter, we will describe the current surgical management of HOCM.

**Keywords:** hypertrophic obstructive cardiomyopathy, HOCM, myotomy, SAM

#### **1. Introduction**

Hypertrophic cardiomyopathy (HCM) is a genetic disorder of the myocardium, characterized by marked myocardial hypertrophy (>15 mm) that cannot be explained by any other diseases that may cause secondary hypertrophy [1]. Its prevalence is 0.2–0.6% [2], with an overall annual mortality rate of 1%.

People with HCM often remain oligosymptomatic or even asymptomatic for many years; anyway, they may develop as cardinal symptoms dyspnea, angina pectoris, or stress-induced syncopes, with an increased risk of sudden cardiac death, particularly in young people and athletes [3], due to obstruction of the left ventricular outflow tract (LVOT). This obstruction is dynamic and largely influenced by changes in left ventricular loading and contractility, with subsequently increased left ventricular systolic pressure and secondary mitral regurgitation (MR), myocardial ischemia, and reduction in cardiac output. Around 70% of patients with HCM display relevant obstruction (HOCM) with a high peak pressure difference (more than 30 mm Hg) [4]; in half of these patients the obstruction is present even at rest, while in the remainder it is latent, so that a gradient can be demonstrated only under stress. Septal reduction treatments can lead to considerable relief of the symptoms even in patients whose obstruction is latent.

Echocardiography is an important and reliable method for diagnosing HOCM and for planning the kind of treatment. Echocardiography enables determination of the extent of the left ventricular hypertrophy and of the site, severity, and

#### **Figure 1.**

*Transthoracic echocardiography showing LVOT obstruction (A), with a resting LVOT gradient of 77 mmHg (B) and severe MR, due to SAM (C). Figure courtesy of non-invasive cardiology diagnostic laboratory, Cardiology Department, L. Sacco Hospital, Via G.B. Grassi 74, Milano, Italy.*

mechanism of any obstruction. In addition, mitral valve (MV) apparatus can be adequately studied, in order to recognize any systolic distortion of the MV associated with systolic anterior motion (SAM) that often leads to secondary MR (**Figure 1**).

Despite medical therapy (treatment with B-blockers or, sometimes, Verapamil) is the first-line therapy for symptomatic patients with LVOT obstruction [1], a large proportion of patients with dynamic obstruction remain symptomatic so, a septal reduction treatment (SRT) is needed in order to relief of the symptoms. This can take the form of either septal myectomy or percutaneous alcohol ablation of the septum [5]. In this chapter we will describe the current surgical management of HOCM.

## **2. Anatomical classification of HCM**

Morphology is variable, common variants being basal, mid-ventricular, apical, and diffuse types have been described. Maron classification reported 4 variants of HCM [6]:


**109**

*Surgical Treatment of Hypertrophic Obstructive Cardiomyopathy*

ACC/AHA and ESC guidelines recommend that septal reduction therapy should be performed only by experienced operators, working as part of a multidisciplinary team expert, in the management of HCM [1, 7]. A SRT should be performed in

1.Significant LVOT obstruction (resting or maximum provoked LVOT gradient

4.The current indications have expanded recently to include symptomatic patients with low resting outflow gradients and latent obstruction.

Surgical septal myectomy is the therapeutic gold standard for the treatment of drug-refractory disabling symptoms in HCM caused by LVOT obstruction. This procedure can relieve hemodynamic disorders and has an acceptable surgical risk

TAESM through a transverse aortotomy, the aortic valve is totally exposed and the aortic leaflets are retracted so as to inspect the LVOT, the hypertrophic cardiac muscle and anterior MV leaflet. In order to open the LVOT and reduce the gradient to <30 mmHg, resection of the hypertrophic muscle until the thickness of the LV wall and interventricular septum became nearly normal by visual inspection, has to be performed. The myectomy should be initiated about 1.5 cm below the aortic annulus starting at the level of the non-coronary/right-coronary commissure to avoid the membranous septum and avoid creating a secondary ventricular septal defect (VSD). The septum is cut into as much as possible to relieve the obstruction and it is extended toward the left/non-coronary commissure so that the entire

It was performed, for the first time, in 1968 by Morrow et al. [8]; initially, the myectomy was limited in scope, but nowadays the resection is much more aggressive in terms of both width and length [5, 9]. Sparing the cardiac conduction system, septal myocardium is resected, depending on the area of hypertrophy and extending if necessary as far as the level of the papillary muscles, to an extent sufficient to eliminate the obstruction, retaining septal thickness of 1 cm. Surgical

when performed on appropriate patients and in experienced centers [7].

2.Angina, Dyspnea (NYHA functional class III-IV), Syncope

3.Persistent symptoms on maximal medical therapy.

3.Right anterolateral minithoracotomy (IV I.S.)

septal myectomy can be performed as follows:

**5.1 Transaortic extended septal myectomy (TAESM)**

*DOI: http://dx.doi.org/10.5772/intechopen.86816*

**3. Surgical indication**

of ≥50 mmHg)

**4. Surgical approaches**

2.Ministernotomy

1.Standard median sternotomy

**5. Surgical septal myectomy**

presence of:
