**2. Strain imaging: general principles**

Strain is defined as the fractional change in length of a myocardial segment relative to its baseline length, it is expressed as a percentage. Strain rate is the temporal derivative of strain, providing information on the speed at which the deformation occurs. Echocardiography, because of its dynamic nature, is ideally suited for the evaluation of cardiac mechanics through the application of deformation indices [5, 6]. Two echocardiographic techniques have dominated the clinical and research arena of deformation echocardiography: (1) tissue Doppler imaging, and (2) speckle tracking imaging. Both techniques lend to the derivation of multiple parameters of myocardial function. Tissue Doppler Imaging (TDI) was the first method used to measure myocardial deformation by echocardiography. The method is well validated and has been shown to provide valuable data in a wide range of conditions. Tissue Doppler is currently used mainly for evaluation of diastolic LV function, its use in aortic valve disease will not be discussed in this chapter. Speckle tracking, mainly through the use of global longitudinal strain (GLS), is increasingly used to identify subclinical myocardial dysfunction in patients with valvular heart disease and to identify optimal timing for surgery or intervention and prognosticate outcomes after surgery/intervention, and is the main focus of this review.

## **3. Strain imaging in aortic stenosis**

Aortic stenosis inflicts progressive pressure overload on the LV with compensatory concentric hypertrophy (**Figure 1**). Initially, the increased wall thickness and conservation of normal LV chamber dimensions offsets the increased LV pressure, maintaining a normal ejection fraction. If the aortic stenosis is not corrected it will inexorably lead to reduced myocardial perfusion, and eventual fibrosis with consequent drop in ejection fraction. It is well recognized that LV GLS is superior to LVEF in detecting perturbations in myocardial function. Compared with normal controls, severe aortic stenosis patients have impaired strain in all three layers of the LV myocardium. LV strain analysis in aortic stenosis has been evaluated in different settings as noted in the following sections.

**45**

stenosis:

**Figure 1.**

*valve area (AVA) of 1.1 cm<sup>2</sup>*

*Clinical Applications of Strain Imaging in Aortic Valve Disease*

**4. Strain imaging and ejection fraction in aortic stenosis**

*(EF). The GLS is normal at −20% indicating absence of any LV dysfunction.*

Measuring LV ejection fraction is crucial in the management of patients with asymptomatic severe aortic stenosis (AS). According to the current American Heart Association/American College of Cardiology and European Society of Cardiology guidelines there is a Class I indication (Level of Evidence: B) to perform aortic valve intervention in asymptomatic patients with severe AS when the LVEF becomes <50% [7, 8]. Predictors of poor outcome in aortic stenosis include advanced age, significant leaflet calcification, rapid disease progression and decreased left ventricular (LV) ejection fraction (EF). Patients can develop impaired LVEF due to afterload mismatch or from true depression of myocardial contractility due to myocardial fibrosis. Myocardial fibrosis occurs early in the natural history of aortic stenosis, affecting diastolic and systolic function and offering a substrate for ventricular arrhythmias, playing a role in the progression to heart failure and sudden cardiac death. These observations indicate that current echocardiographic assessment of LV function by measuring only the LVEF is insufficient and that new parameters detecting subtle myocardial impairment are needed to improve risk stratification and predict outcomes in patients with AS.

*Severe aortic stenosis: global longitudinal strain (GLS) in a patient with severe aortic stenosis with an aortic* 

*ventricular end-diastolic and end-systolic volumes (EDV, ESV) are normal as well as the LV ejection fraction* 

 *maximal velocity (AV V2) of 3.9 m/s and a mean gradient of 48 mm Hg. Left* 

Several studies have defined the added value of global longitudinal strain over LVEF to characterize and prognosticate the clinical evolution of patients with aortic

• There is growing evidence suggesting the prognostic role of global longitudinal strain (GLS), in asymptomatic patients with AS. The American Society of

*DOI: http://dx.doi.org/10.5772/intechopen.93341*

*Clinical Applications of Strain Imaging in Aortic Valve Disease DOI: http://dx.doi.org/10.5772/intechopen.93341*

### **Figure 1.**

*Advances in Complex Valvular Disease*

**2. Strain imaging: general principles**

main focus of this review.

**3. Strain imaging in aortic stenosis**

settings as noted in the following sections.

damaged.

disease.

(LVH), LV end-systolic volume (LVESV), degree of leaflet calcification, and trans-aortic valve gradients. Because of the LV deformation indices potential to detect subclinical LV dysfunction, they are being used with increasing frequency in the management of patients with aortic valve disease [4] and advancing the timing for aortic valve surgery or intervention, before the LV is irreversibly

Our objective with this chapter is to describe the use of strain imaging, particularly global longitudinal strain in the assessment of cardiac function in patients with aortic valve disease. We review the current clinical applications of strain analysis in patients with aortic valve disease, highlighting strengths and weaknesses and emphasizing normal and abnormal findings in aortic stenosis (AS) aortic regurgitation (AR) and mixed aortic valve disease (ASAR); we summarize unresolved issues, potential future research priorities, and recommended indications for incorporating this technique into the clinical practice of patients with aortic valve

Strain is defined as the fractional change in length of a myocardial segment relative to its baseline length, it is expressed as a percentage. Strain rate is the temporal derivative of strain, providing information on the speed at which the deformation occurs. Echocardiography, because of its dynamic nature, is ideally suited for the evaluation of cardiac mechanics through the application of deformation indices [5, 6]. Two echocardiographic techniques have dominated the clinical and research arena of deformation echocardiography: (1) tissue Doppler imaging, and (2) speckle tracking imaging. Both techniques lend to the derivation of multiple parameters of myocardial function. Tissue Doppler Imaging (TDI) was the first method used to measure myocardial deformation by echocardiography. The method is well validated and has been shown to provide valuable data in a wide range of conditions. Tissue Doppler is currently used mainly for evaluation of diastolic LV function, its use in aortic valve disease will not be discussed in this chapter. Speckle tracking, mainly through the use of global longitudinal strain (GLS), is increasingly used to identify subclinical myocardial dysfunction in patients with valvular heart disease and to identify optimal timing for surgery or intervention and prognosticate outcomes after surgery/intervention, and is the

Aortic stenosis inflicts progressive pressure overload on the LV with compensatory concentric hypertrophy (**Figure 1**). Initially, the increased wall thickness and conservation of normal LV chamber dimensions offsets the increased LV pressure, maintaining a normal ejection fraction. If the aortic stenosis is not corrected it will inexorably lead to reduced myocardial perfusion, and eventual fibrosis with consequent drop in ejection fraction. It is well recognized that LV GLS is superior to LVEF in detecting perturbations in myocardial function. Compared with normal controls, severe aortic stenosis patients have impaired strain in all three layers of the LV myocardium. LV strain analysis in aortic stenosis has been evaluated in different

**44**

*Severe aortic stenosis: global longitudinal strain (GLS) in a patient with severe aortic stenosis with an aortic valve area (AVA) of 1.1 cm<sup>2</sup> maximal velocity (AV V2) of 3.9 m/s and a mean gradient of 48 mm Hg. Left ventricular end-diastolic and end-systolic volumes (EDV, ESV) are normal as well as the LV ejection fraction (EF). The GLS is normal at −20% indicating absence of any LV dysfunction.*
