Echocardiographic characteristics and causal mechanism of physiologic mitral regurgitation in young normal subjects

Abstract

SummaryBuckground: It has become evident that mitral regurgitation (MR) is not uncommon in healthy subjects, and Doppler color flow mapping is a technique that imparts important information relevant to its detection.Hypothesis: Using transthoracic echocardiography, this study evaluated the mechanism of physiologic MR in young normal subjects using transthoracic echocardiography.Methods: The study population consisted of 48 young normal subjects (mean 21 5 5 years) with M R (physiologic MR group), 40 age-matched young normal subjects (mean 20 k 5 years) without MR (control group), 45 patients (mean 41 k 15 years) with mitral valve prolapse with MR (MVP group), and 27 patients (mean 59 k 13 years) with ruptured chordae tendineae (rupture group).Results: Men were predominant in the rupture group, whereas there were no significant gender differences in the other three groups. Left ventricular end-diastolic dimension and left atrial systolic dimension were slightly smaller in the physiologic MR group than in the control group, but were significantly smaller than those in the MVP and rupture groups. The ratio of the maximum anteroposterior diameter to the maximum transverse diameter on chest radiography and the ratio of the short-to long-axis diameter of the left ventricular cavity at end diastole, determined from two-dimensional short-axis echocardiogram, were significantly lower in the physiologic MR group than in the other three groups. Mitral regurgitation occurred more frequently at the posteromedial commissural site in the physiologic MR and MVP groups. whereas there was no preference for location in the rupture group. Early systolic MR was often observed in the physiologic MR group, whereas pansystolic MR was common in the MVP and rupture groups.Conclusion: As a causal mechanism for physiologic MR detected in young normal subjects, "flattening" of the thorax during growth may cause morphologic abnormalities of the left atrial and ventricular cavities, resulting in spatial imbalance of the mitral complex and resulting in malcoaptation of the valve.

Echocardiographical Characteristics of Healthy Young Subjects with Physiological Mitral Regurgitation

“…As a result, we did not find any statistical differences in the mean ventricular or atrial diameters between the two groups. Our results were different from those of the study by Mishiro et al 15 It has been reported that another cause of PMR could be the anatomical differences in the chordeal networks. In an autopsy series by Lam et al, it was reported that the commissural chordea attached to the posteromedial commissural site were too long.…”

“…In that study, narrowing of the thorax resulting in malcoaptation of the mitral valve was suggested as the mechanism that caused PMR in young normal subjects. 15 In our study, cadets with a flattened thorax were excluded from the study, so the PMR observed in our study was not related to thorax flattening. As a result, we did not find any statistical differences in the mean ventricular or atrial diameters between the two groups.…”

“…1,3,16 However, with colour Doppler imaging, trivial valvular regurgitations, defined as physiological, may be detected in healthy subjects. 15 Physiological regurgitations over the tricuspid and pulmonary valves have been reported. 17,18 Reports have also demonstrated physiological regurgitation over the mitral valve.…”

“…as a possible explanation of how PMR develops. 21 Mishiro et al 15 stressed the importance of this factor in their study, which demonstrated that the ratio of the short-to long-axis diameter of LVIDd was significantly lower in a group of subjects with PMR compared with control subjects, subjects with mitral valve prolapse and MR, and subjects with ruptured chordae tendineae. The subjects with PMR also had smaller left atrial cavities compared with subjects in the other groups.…”

“…7 -14 With regard to the development of PMR, many mechanisms related to the physical dimensions of the body, as well as to the structure of the cavities and valves, have been proposed. 15 This study aimed to determine the echocardiographical characteristics of healthy subjects with PMR and the causal mechanism of the development of PMR.…”