Cardiovascular magnetic resonance (CMR) is generally believed to be an excellent modality for nearly every cardiac or vascular application. However, if there is a perceived weakness related to non-coronary imaging of the cardiovascular system, the general perception in the non-CMR community is that valvular heart disease poses the greatest limitation for CMR. Consequently, echocardiography has assumed the major workload for clinical valvular assessments, and CMR has classically been relegated to a secondary modality upon the failure of echocardiography. As one might infer from the direction of this prose, this notion has clearly changed over the last 5 years, making many elements of CMR comparable, or, in some indications, superior to echocardiography. The main limitation that persists, with the greatest clinical impact, is the relatively limited ability for the CMR-based evaluation of endocarditis.

The severity of valvular heart disease can be assessed in a number of ways by CMR, providing another example of the diversity of the modality to perform a comprehensive cardiovascular examination, especially for valvular assessments. The steady state free precession (SSFP) and the phase velocity mapping (PVM) sequences offer the greatest ability to assess and quantitate the extent of disease. Less often, resorting to the older gradient-recalled echo (GRE) sequences with long echo times (TEs), offers more physiologic representation of the true severity of valvular lesions through loss of signal in jet flow due to the greater intervoxel dephasing phenomena.

By definition, the two lesions that dominate valvular evaluations are regurgitant and stenotic pathologies. Each is approached in a distinct manner, which will be illustrated here by means of case study examples.

In many CMR textbooks valve anatomy is not well described because it has traditionally not been well depicted by CMR. The image in Fig. 9-1 of the aortic valve and its cusp anatomy suggests that this: notion is erroneous and outdated. Using this approach, planimetry of the aortic valve can be formally measured, not grossly estimated, as when employing various geometric formulae available to the echocardiographer or angiographer utilizing the continuity equation or the Gorlin formula. Theoretically and practically, this direct approach yields information closest to what might be obtained in the surgical suite. It would seem intuitive that the closer an imaging modality comes to demonstrating that which is visible to the eye the more accurate and robust the measurement generated would be. The following are a series of case studies and examples of valvular anatomy and lesions.

Mitral regurgitation (ERO) (MR) has been shown to be associated with increased morbidity and mortality, even in asymptomatic patients. Yet, estimation of MR by echocardiography has been primarily limited to quantification of effective regurgitant orifice area derived from various geometric assumptions. CMR also permits indirect quantitation of MR. MR is the most ubiquitous valvular lesion for which a patient may present. Discussed in an earlier chapter, several aspects bear reiteration. First, MR is depicted as a dephasing intervoxel
artifact and is used clinically to gauge semiquantitatively the extent of mitral valve leakage. Using PVM, the exact amount of regurgitation can be measured in a manner very distinct and very different from the many physiologic and geometric assumptions utilized by echocardiography. Measurement of all the blood volume that passes through a plane positioned parallel to the mitral valve annulus completely interrogates the extent (volume) of MR. Moreover, elements to define the underlying anatomic mechanistic perturbations can also be well defined by CMR. In Fig. 9-7, there are several metrics used surgically and clinically to better describe the etiology of MR, where, for two patients with essentially the same left ventricle (LV) metrics, there is a very discordant degree of MR. Examining the mitral valvular apparatuses demonstrates the explanation for the differences in MR (see Table 9-1). In patient A, as opposed to patient B, the mitral annulus, tenting angle, coaptation distance (valve closure point from mitral annulus), and tenting area (area of triangle formed by the junction of the mitral annulus and the valve closure point) are near normal.