15: ECHOCARDIOGRAPHIC EVALUATION OF VALVE FUNCTION AND ENDOCARDITIS

Introduction

Echocardiography is an effective means of assessing cardiac valve function. It is useful for a rapid qualitative assessment or a more comprehensive assessment for all forms of valve function using transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE). Doppler assessment allows an accurate quantitative measurement of the severity of stenotic and regurgitant lesions. The extent to which the critical care echocardiographer applies the sophisticated tools of the cardiologist to assess valvular heart disease is highly variable. By training, background, and interest, cardiologists often take the lead in this aspect of echocardiography. However, the intensivist who performs echocardiography should have some fundamental competence in assessing valve function, as many patients in the intensive care unit (ICU) may have valve dysfunction that adversely impacts their cardiopulmonary status.

In general, the intensivist will be interested primarily in the identification of catastrophic valve failure or valve dysfunction that is sufficiently severe to impact the hemodynamic functioning of the patient. Conversely, the identification of lesser degrees of valve disease or normal valve function are also of interest, as the intensivist may then determine that valve failure is not a contributing factor to the patient’s critical illness. This chapter will review the echocardiographic assessment of valve function from the perspective of the bedside intensivist.

Level of Training

Intensivists who perform critical care echocardiography (CCE) will typically demonstrate competence in basic CCE (several standard two-dimensional [2-D] views without comprehensive training in Doppler), but may also have competence in advanced CCE (see also Chapter 4). The latter is equivalent to level 2 training by standard cardiology criteria.¹ Intensivists who have basic training in echocardiography have a limited ability to assess valve function. Without training in quantitative spectral Doppler measurements, the basic-level examiner can identify obvious mechanical failure of the mitral valve (MV; e.g., a flail leaflet, ruptured chordae, or ruptured papillary muscle) or obvious aortic valve (AV) disruption. Severe stenosis of these valves may also be apparent. By definition, intensivists with training in basic echocardiography do not have comprehensive Doppler training and lack the ability to perform quantitative measurements of valve function.

The qualitative assessment of valve function is, however, in the domain of the basic critical care echocardiographer and may be carried out using color Doppler. This is not to suggest that the use of color Doppler is straightforward and without nuance. The pitfalls of color Doppler include gain settings, wall jet effects,² angle effects, and shadowing by surrounding structures, such as prosthetic valve apparatus or a calcified annulus, and are not intuitively obvious. Of particular concern with these pitfalls is that the echocardiographer may miss a severe valvular lesion due to misinterpretation of the color Doppler image. Thus, a key cognitive skill for the basic critical care echocardiographer is to recognize when to call for a consultation from a more experienced echocardiographer. If there is the possibility of significant valve dysfunction, ...