Pathophysiology of valvular heart disease: Implications for nuclear imaging

Abstract

In general, the echocardiogram has become the mainstay of diagnosis in patients with valvular heart disease. Its strength is that it provides information about valve pathoanatomy and about the severity of stenosis and regurgitation not available by other techniques. However, radionuclide studies offer a more precise gauge of left and right ventricular ejection performance, which is useful in the timing of surgery. Because, at present, most cardiac catheterization procedures in patients with valve disease are performed to evaluate coronary anatomy, a noninvasive technique for detecting coronary disease could obviate the need for invasive studies prior to surgery. The presence of left ventricular hypertrophy especially in aortic stenosis has made myocardial imaging less than perfect in this preoperative evaluation, but clearly this is an area of potential fruitfulness in the use of radionuclide techniques. Additional studies regarding the utility of exercise RNA seem warranted and might be of particular interest in mitral regurgitation, in which little is known about the ability of such studies to help time mitral valve surgery. The addition of estimates of loading during exercise studies is an attractive pathophysiologic adjunct and should be helpful in the interpretation of such studies. The potential role for targeted “hot spot” imaging of ischemia, apoptosis, and necrosis in patients with valvular heart disease remains undefined, although such imaging represents another potential area of investigation that warrants further evaluation.