Normal Ratios of Right and Left-Sided Parameters in Adults Free of Cardiovascular Disease: The Framingham Heart Study (RF_FR_333)

Friday, January 31, 2025

11:20 AM – 11:30 AM East Coast USA Time

Location: Blue Room PreFunction

Presenting Author(s)

MC

Michael Chuang, MD

Seated
Cardiovascular Research Foundation

Primary Author(s)

MC

Michael Chuang, MD

Seated
Cardiovascular Research Foundation

Co-Author(s)

PG

Philimon Gona, PhD

Professor
University of Massachusetts Boston
MQ

Mariam S. Qazi, DO

Research Fellow
University of Texas, Houston
CS

Carol Salton, BA

Research Associate
Beth Israel Deaconess Medical Center
CO

Christopher O'Donnell, MD

Professor
Harvard Medical School
WM

Warren J. Manning, MD

Section Chief, Non-invasive Cardiac Imaging
Beth Israel Deaconess Medical Center/Harvard Medical School
Beth Israel Deaconess

Background: An increased ratio of right ventricular (RV) to left ventricular (LV) diameter in the four-chamber view is a marker of right ventricular strain in acute pulmonary embolus. However, the shape of the right ventricle, roughly triangular in long-axis planes, and irregularly crescentic in the short axis, can result in different values of “RV diameter” with even slight differences in the orientation of the nominal 4-chamber view. The ratio of RV to LV volumes (RLVR) does not depend on a reproducible 4-chamber view and thus may have advantages over the corresponding diameter ratio. Similarly, the ratio of main pulmonary artery diameter (MPA) to ascending aorta diameter (PAAR) also may be useful in identifying acute right-sided volume and pressure overload. Therefore, we sought to determine whether RLVR and PAAR differ with sex or age-group, as different threshold values would be needed to identify an increased ratio if this were the case.

Methods:

1794 adults from the community-dwelling Framingham Heart Study Offspring cohort underwent cardiovascular magnetic resonance (CMR) at 1.5 T. RV and LV volumes at end-diastole and end-systole were determined by manual planimetry from bSSFP images. RLVR was calculated at end-diastole. Aortic and MPA diameters were measured from an axial, black-blood T2W slice at the level of PA bifurcation. A referent group free of any history of myocardial infarction, heart failure, wall motion abnormality by CMR, hypertension, greater than mild heart-valve disease, asthma, COPD and deep venous thrombosis was identified and stratified by sex and age group (< 55, 55 to < 65, ≥65 years). Mean (SD) values were compared between sexes by two-sample t-test, and potential within-sex age group trends were assessed by linear regression with age-group analyzed as an ordinal variable.

Results:

Referent-group participants were similar in mean age for both sexes: 60.3(8.2)y (271 men) vs. 61.4(8.3)y (420 women). Mean RLVR was 1.02 (0.15) among men and 0.98 (0.12) among women, p=0.001. There was no statistical evidence of linear trends with age-group for RLVR in either sex, p=0.59 (men), p=0.82 (women). The upper 95^th percentile for RLVR was 1.23 for men and 1.17 for women. Mean PAAR was 0.76(0.10) for men and 0.75(0.12) for women. PAAR decreased with advancing age-group among both men (p< 0.0001) and women (p=0.002), primarily driven by increasing diameter of the ascending aorta with greater age. The inverse association of age with PAAR suggests that age-group specific thresholds would be required to identify increased PAAR; upper 95^th PAAR values across increasing age groups were 0.98, 0.89, 0.88, respectively among men; and 0.93, 0.90, 0.87, respectively, for women.

Conclusion:

We determined the normal ratio of RV to LV volume among community-dwelling adults free of significant cardiopulmonary disease. RLVR did not vary across age-groups within each sex. Although both sexes had mean RLVR close to unity, RLVR was slightly greater among men than women. We identify sex-specific upper 95^th percentile values for RLVR which may be useful for identification of acutely increased RV volume, as in acute right-heart strain as associated with pulmonary embolism. Though technically simpler to obtain, PAAR would require sex and age-group specific thresholds.