**3.6 Echocardiography**

Echocardiography is the most valuable tool in valvular heart disease due to its portability, ease of use. Low cost, steadily improving resolution, and its ability to assess hemodynamics, additional ultrasound-based modalities can provide information about cardiac anatomy, function, and hemodynamics. These modalities include two dimensional (2D) or B-mode in which sound waves are in a fan-like distribution, yielding a real wedge-shaped tomographic image of the heart. There are three subtypes of Doppler ultrasound. Continuous-wave Doppler, all velocities along a continuous line through the heart are displayed as a spectrum over time. In pulse wave Doppler, the sample volume is placed on a 2D image, and the spectral splay of velocities represents the blood flow velocities in this region only.

Tissue Doppler is yet another form of Doppler echocardiography which measures the velocity of anatomic structures rather than red blood cells; it currently has very limited application in valvular heart disease [30, 31].

Hemodynamic assessment. Firstly, the pressure gradient a valve or between two chambers can be estimated by taking advantage of the relationship between pressure (P), and velocity (v) as described in is the conservation of flow and different diameter, the flow of fluid through one section match flow through the other end. Since flow equals the product of orifice area and flow velocity, this principle can be stated as Area 1 × Velocity 1 = Area 2 × Velocity 2. This is used explicitly in the determination of aortic valve area (**Figure 3**) [30].

Another hemodynamic measure important valvular heart disease are the rate of pressure equilibration between two chambers (e.g. pressure half-time, deceleration).

Cardiac catheterisation and direct measure of intracardiac pressures, ventriculography, aortography, and assessment of coronary vessels before valve surgery all continue to be an essential tool in the evaluation of valvular heart disease.

**Figure 2.** *Cardiomegaly and pulmonary congestion.*

### **Figure 3.**

*Echocardiogram assessment of aortic valve.*

Occasionally, balloon valvotomy serves an important therapeutic and diagnostic role in mitral, and occasionally, aortic stenosis.

Positron emission tomography (PET) is an emerging imaging technique which allows improved resolution more flexibility than SPECT, including the possibility of imaging metabolic substrates and neural transmitters. In light of its expense and dependency mostly cyclotron-produced isotopes, its role in valvular heart disease remains to be determined.
