**4.1. Pathophysiology**

The underlying structural abnormalities in HCM are:


These changes in HCM patients lead to diastolic dysfunction, impaired coronary reserve, supraventricular and ventricular dysrhythmias, and sudden cardiac arrest. Left ventricular remodelling can include fibrosis, focal, diffuse, asymmetric, or concentric hypertrophy, as well as decrease in the cavity size. The most common subtype of HCM presents as hypertrophy of the septum and the anterio-lateral free wall.

LV outflow tract obstruction (LVOTO) occurs in HCM, and initially it was proposed that the basal septal hypertrophy encroaching on the LVOT caused the obstruction of the tract. However, more recent studies have pointed towards the fact that during ventricular systole, flow against an abnormally positioned mitral valvular apparatus results in a Venturi effect on the anterior leaflet of the mitral valve and induces systolic anterior movement (SAM) of the anterior mitral valve leaflet. The mitral valve apparatus abnormalities can include hypertrophied papillary muscles touching the septum, elongated mitral leaflets, anterior displacement of papillary muscles, or anomalous insertion of the papillary muscle onto the anterior mitral leaflet. LVOTO can be precipitated or aggravated by increased contractility of the heart or tachycardia or decreased end-diastolic volume or systemic vascular (arterial) resistance. With HCM, incidence of diastolic dysfunction is more than LVOTO.

Myocardial ischaemia is present in patients with HCM, irrespective of the presence or absence of coronary artery disease. Myocardial ischaemia is precipitated by several factors including


Transesophageal echocardiography (TEE) is also helpful as it identifies causes of hypotension, response to fluid therapy or inotrope support, estimates preload, cardiac output, dia-

Hypertrophic cardiomyopathy can be defined as abnormal LV thickening without chamber dilation that is usually asymmetrical, develops in the absence of an identifiable cause (e.g. aortic valvular stenosis[AS] and hypertension), and is associated with myocardial fibre disarray. Hypertrophic cardiomyopathy (HCM) is very common and can affect people of any age group. It affects both sexes equally. It is a cause of sudden cardiac arrest and death in apparently healthy young people, including young athletes. HCM is a relatively common inherited disorder with an autosomal dominant pattern of inheritance with variable expression and has

Defects of at least 11 genes and >1440 mutations sites demonstrate its genomic heterogeneity.

**1.** myocardial cell disarray where the cells are rearranged in a disorganised pattern as

These changes in HCM patients lead to diastolic dysfunction, impaired coronary reserve, supraventricular and ventricular dysrhythmias, and sudden cardiac arrest. Left ventricular remodelling can include fibrosis, focal, diffuse, asymmetric, or concentric hypertrophy, as well as decrease in the cavity size. The most common subtype of HCM presents as hypertro-

LV outflow tract obstruction (LVOTO) occurs in HCM, and initially it was proposed that the basal septal hypertrophy encroaching on the LVOT caused the obstruction of the tract. However, more recent studies have pointed towards the fact that during ventricular systole, flow against an abnormally positioned mitral valvular apparatus results in a Venturi effect on the anterior leaflet of the mitral valve and induces systolic anterior movement (SAM) of the anterior mitral valve leaflet. The mitral valve apparatus abnormalities can include hypertrophied papillary muscles touching the septum, elongated mitral leaflets, anterior displacement of papillary muscles, or anomalous insertion of the papillary muscle onto the anterior mitral leaflet. LVOTO can be precipitated or aggravated by increased contractility of the heart or tachycardia or decreased end-diastolic volume or systemic vascular (arterial) resistance. With

**2.** coronary microvasculature dysfunction due to increased wall to lumen ratio; and.

stolic dysfunction, valve function, and regional wall motion abnormalities.

**4. Hypertrophic cardiomyopathy**

112 Current Topics in Intensive Care Medicine

The underlying structural abnormalities in HCM are:

**3.** remodelling changes occurring in the heart.

phy of the septum and the anterio-lateral free wall.

HCM, incidence of diastolic dysfunction is more than LVOTO.

opposed to a normal parallel myocyte arrangement;

a prevalence of 1 in 500.

**4.1. Pathophysiology**


Supraventricular or ventricular dysrhythmias are relatively common in these patients due to the presence of disorganised cellular architecture, expanded interstitial matrix and myocardial scarring. They are the cause of incidence of sudden arrest in this group of cardiomyopathy.

#### **4.2. Signs and symptoms**

The clinical presentation of HCM varies widely. These patients can present early in their life with debilitating symptoms or can live for decades asymptomatically while some others die suddenly. The most frequent symptoms include dyspnea, dizziness, exercise intolerance, angina, syncope, and/or sudden death.

Physical examination may be normal at rest but may reveal a double apical impulse, gallop rhythm, a systolic murmur and thrill in the presence of functional LVOTO. It is rare, but some people with hypertrophic cardiomyopathy can suffer sudden cardiac arrest during a vigorous physical workout. The physical activity can trigger dangerous arrhythmias leading to sudden death.

The major risk factors for sudden cardiac death are:


Electrocardiography (ECG) changes include left atrial (LA) enlargement, pathologic Q waves, high QRS voltage complexes, ST segment depression, and inverted T waves in at least two or more consecutive leads.

Echocardiography can easily demonstrate the presence of myocardial hypertrophy. Ejection fraction is usually >80%, reflecting the increase in force of contraction of the heart. Echocardiography can also assess the mitral valvular apparatus, the presence of mitral regurgitation, and the presence of LVOTO by demonstrating turbulent flow across the aortic valve. Pressure gradients across the LVOT can be measured. Echocardiography is useful in evaluating diastolic function of the heart.

**1.** labile obstruction and peak LVOT pressure gradients ≥50 mm Hg during exercise or provo-

Current Perspectives on Cardiomyopathies http://dx.doi.org/10.5772/intechopen.79529 115

Some patients may be candidates for implantable cardioverter-defibrillator (ICD) implanta-

**Prognosis:** The overall mortality rate of HCM is 1% per annum. However, some patients at

**Patients undergoing non-cardiac surgery:** Most of the time, the patients with HCM are asymptomatic when they show up in the PAC clinic for elective surgeries. In the absence of signs and symptoms, the ECG findings may suggest that the patient has underlying HCM.

Initial patient evaluation should be aimed at determining the disease severity by assessing functional status of the patient, personal and family cardiac history, the presence or absence of cardiac and respiratory symptoms, history of rhythm disturbances, current medications, and previous strokes, or congestive heart failure history. During physical examination, all murmurs should be evaluated for dynamic changes with rest and exertion, and patients with murmurs that do not fulfil the criteria of a benign murmur should undergo an echocardiographic examination before surgery. Patients should be instructed to continue their rate controlling medications and maintain proper hydration preoperatively. Moreover, the presence

**Preoperative management:** A lot of patients with HCM may experience perioperative cardiac events like MI, congestive heart failure, severe hypotension, and supraventricular and ventricular tachydysrhythmias. Therefore, we need to focus on understanding the basic pathophysiology of the events and adjust our anaesthetic plans according to the patient needs.

In patients with HCM, preoperative administration of anti-anxiety medications may help to reduce anxiety and prevent the activation of anxiety-induced sympathetic response. Adequate preoperative intravenous fluid administration may help in preventing LVOTO and minimise

For patients who have an ICD in situ, the device should be turned off just before the surgery and an external defibrillator should be readily available and the ICD should be positively

higher risk of sudden death as described before have an annual mortality rate of 5%.

of an automatic ICD and if it has been recently checked should be determined.

the effect of positive pressure ventilation on central blood volume.

• reduction in sympathetic activity to reduce chronotropy and inotropy;

reactivated in the recovery room.

• maintenance of sinus rhythm;

• the maintenance of systemic vascular resistance;

• maintenance of left ventricular filling.

The anaesthetic goals are [4]:

cation and resting gradients >30 mm Hg and.

**2.** NYHA class II through IV symptoms refractory to medical therapy.

tion while as principal surgical option is surgical myomectomy.

Invasive measures like cardiac catheterisation allow direct measurement of the increased left ventricular end-diastolic pressure and the pressure gradient between the left ventricle and the aorta.

The definitive diagnosis of HCM can be made by an endomyocardial biopsy and DNA analysis, but these diagnostic modalities are usually reserved for patients in whom the diagnosis cannot be established by non-invasive means.
