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Right Ventricular Structure Differs by Patient Age, Sex, Race


 

FROM CIRCULATION

Right ventricular mass, volume, and ejection fraction differ significantly according to patient age, sex, and race, according to a prospective imaging study of more than 4,000 healthy people that was reported in Circulation on June 6.

Moreover, the effect of these patient characteristics on the right ventricle is independent of body size, blood pressure level, diabetes status, and other conventional cardiovascular risk factors that are known to be associated with right ventricular morphology, said Dr. Steven M. Kawut of the Penn Cardiovascular Institute at the University of Pennsylvania, Philadelphia, and his associates.

Right ventricular structure and function have been "challenging" to measure with standard echocardiography techniques, and to date studies examining possible determinants of RV morphology have been small, have focused on young adults of homogeneous ethnicity, and have produced mixed findings, the investigators said.

In what they described as "the largest study of RV morphology ever performed," Dr. Kawut and his colleagues used cardiac MRI to assess ventricular morphology in a subset of subjects participating in MESA (Multi-Ethnic Study of Atherosclerosis). Their ancillary study specifically included a large number of subjects (4,123) from six communities across the United States who were of four major ethnicities and who ranged in age from 45 to 84 years.

The investigators found a consistent, approximately 5% decrease in RV mass for every 10-year increase in patient age, with men showing significantly larger age-related decrements in RV mass (1.0 g per decade) than did women (0.8 g per decade). These findings "may be surprising," as previous studies have been all over the map, with reports that aging increases, decreases, or makes no changes in RV mass, the investigators said.

Older age also was associated with smaller RV volume, and again the decreases in volume were greater among men than among women. Increasing age also was associated with increasing right ventricular ejection fraction of approximately 1% per decade (in all ethnicities except white), and decreasing right ventricular stroke volume of approximately 3% per decade.

It is possible that both the loss of cardiac myocytes and diminished quality of cardiac myocytes occur with aging, and may account for these changes, they said.

Sex also was independently associated with RV morphology. Men had approximately 8% higher RV mass than did women, as well as approximately 10% larger RV end-diastolic volume, approximately 4% lower RV ejection fraction, and approximately 7% larger RV stroke volume.

These sex differences "appeared to persist despite adjustment for the respective left ventricular parameter, suggesting that these findings were not solely due to secondary effects from the left ventricle or residual confounding by body size or composition." It seems likely that hormonal influences play a role in these sex-based differences, the researchers added.

"To our knowledge, ours is the first study to examine differences in RV morphology between races and ethnicities," they noted.

Blacks and Chinese Americans had a lower RV mass than did whites, whereas Hispanics had higher RV mass. Blacks had smaller RV end-diastolic volume than did whites, whereas Hispanics had larger RV end-diastolic volume than whites. Similarly, RV stroke volume was smallest in blacks, intermediate in whites, and larger in Hispanics. These differences could be the result of genetic variation among ethnic groups and may explain the poorer outcomes that are noted in blacks who have cardiopulmonary disease.

Based on their findings, Dr. Kawut and his associates devised new normative equations for measures of right ventricular morphology based on patient age, sex, and race. When these new equations were applied to the entire study cohort, they "were effective at indexing right ventricular measures to body size, [which is] important for clinical care and research since the outcomes of patients with congestive heart failure and pulmonary arterial hypertension depend on RV morphology and function," they said.

The new equations must be validated in other populations before they can be used clinically, the investigators noted.

This study was limited in that many subjects in MESA were unable to tolerate cardiac MRI, and many of the results for subjects who did undergo the procedure were "uninterpretable," they added.

The authors had no disclosures.

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