There is a paucity of data on the prevalence of primary myxomatous degeneration (PMD) of the cardiac valves. Because the gold standard for the diagnosis is pathology, its preoperative detection rate is relatively low. The purposes of this study were to determine the capability of echocardiography to identify PMD compared with surgical pathological findings and to determine the echocardiographic features of PMD.
Echocardiograms were retrospectively compared with pathologic findings in 1,080 patients undergoing surgery for moderate or severe cardiac valve regurgitation. PMD of the mitral, aortic, and tricuspid valves was retrospectively identified, with a comparison of the echocardiographic and pathologic findings, to estimate the prevalence of PMD and to summarize its echocardiographic features.
Of 1,080 patients, 104 were diagnosed with PMD (prevalence, 9.62%). Echocardiography identified valvular prolapse and thickening in 85% of patients. The echocardiographic characteristics of PMD included valvular regurgitation, valvular thickening, valvular prolapse, and rupture of chordae tendineae. Combinations of these characteristics were seen on multiple valves. Among patients with PMD, 59 had only mitral valve involvement, 25 had only aortic valve involvement, two had only tricuspid valve involvement, 10 had both mitral and aortic valve involvement, and three had both mitral and tricuspid valve involvement.
In patients undergoing surgery for valvular regurgitation, a high prevalence of PMD was found. PMD has distinctive echocardiographic features, suggesting its preoperative diagnosis.
Primary myxomatous degeneration (PMD) of the cardiac valves was first described by Rippe et al. in 1980. The pathologic features of PMD include mucoid degeneration of the fibrous layer of the valve tissue, with significant fibrosis, valvular dehiscence, and valvular rupture without calcification. PMD may lead to valvular prolapse and regurgitation. Roberts reported that 88% of patients undergoing valve replacement for mitral regurgitation had mitral valve myxomatous degeneration. Although the reported prevalence of cardiac valve myxomatous degeneration in Western countries is between 2% and 8%, the prevalence in China may not be the same. PMD has specific pathologic features that distinguish it from other causes of valvular regurgitation, which may vary with different forms of treatment. Previous studies have not correlated echocardiographic observations with pathologic findings. The purpose of this study was to retrospectively review the echocardiograms of patients with pathologic features of PMD seen at Beijing Anzhen Hospital between 2006 and 2008, contrast their echocardiographic and pathologic findings, and determine both the prevalence of PMD and its echocardiographic features, thus enhancing the capability of echocardiography to preoperatively identify PMD.
Of 1,080 patients undergoing cardiac valve repair or replacement for valvular regurgitation at Beijing Anzhen Hospital between 2006 and 2008, 104 were diagnosed with PMD by pathologic analysis and included in the study. The study protocol was approved by the review board of Anzhen Hospital.
The characteristic pathologic feature of PMD is mucopolysaccharide content accumulation. The gross morphologic features and thus surgically observed findings are leaflets that are thickened and voluminous (i.e., increased in tissue volume), and the chordae tendineae of the atrioventricular valves are thickened, elongated, and sometimes ruptured. The normal systolic bulging of the mitral leaflets into the left atrium, which is exaggerated, was termed “billowing,” and in its more advanced form “floppy,” by Barlow. “Billowing” and “floppy” are descriptive terms used by Barlow to describe valvular morphology on cine angiography. On echocardiography, billowing and floppy manifest as valvular prolapse, which in the case of the mitral valve is defined as systolic atrial displacement of the valve leaflets by ≥2 mm beyond the annular plane in its long axis. In addition, the valve leaflets are thickened (by ≥2 mm) and redundant, and the chordae tendineae are thickened and sometimes ruptured. These changes result in secondary morphologic changes with consequent complications, including valvular regurgitation, chordal rupture, and infective endocarditis ( Figures 1–4 ).
Two experienced pathologists independently provided pathologic diagnoses for all valvular tissue specimens from 1,080 patients. The pathologic specimens were reviewed and reevaluated blindly by the same observers with one additional pathologist to confirm the original diagnoses. Pathologic specimens from 112 patients were subsequently reviewed by the same pathologists, and these data were analyzed to determine interobserver and intraobserver variability. Overall agreement was high (intraobserver concordance, 97.32%, κ = 0.791; interobserver concordance, 98.21%, κ = 0.713; Table 1 ).
|% agreement||κ||% agreement||κ|
All patients underwent comprehensive transthoracic echocardiography using Vivid 7 (GE Healthcare, Milwaukee, WI) or iE33 (Philips Medical Systems, Andover, MA) equipment. Transesophageal echocardiography was performed in all patients whose transthoracic studies were suboptimal (12.7%). Also, the echocardiograms of 976 patients without PMD, who underwent surgery for moderate or severe valvular regurgitation, were retrospectively compared with their pathologic findings. Cardiac valvular regurgitation was assessed and graded according to existing criteria. The echocardiographic features of PMD include valvular thickening (>3 mm), exaggerated atrial displacement of the atrioventricular valves, significant valve prolapse, and ruptured chordae tendineae. Valvular prolapse of the atrioventricular valves is defined as systolic atrial displacement of ≥2 mm beyond the annular plane of the valve in its long axis view ( Figures 5–9 ). Other echocardiographic features are valvular thickening of ≥3 mm and thickened and/or ruptured chordae tendineae. The presence of one of these features was sufficient to characterize PMD of the valve. Valve leaflet measurements of PMD were made at the widest or thickest point of the valve in the long-axis view of the transthoracic or, when necessary, the transesophageal echocardiogram.