Epicardial Fat Volume and Aortic Stiffness in Healthy Individuals: A Quantitative Cardiac Magnetic Resonance Study

Abstract

Purpose: To determine epicardial fat volume (EFV) and aortic stiffness (assessed by aortic pulse wave velocity (PWV)) in healthy individuals, and to investigate the relationship of these parameters, and their association with body mass index (BMI) and age.

Materials and Methods: 58 subjects (29 men, mean age 44.7 ± 13.9 years[y]) underwent a CMR exam at 1.5 Tesla. A 2 D velocity-encoded CMR scan was acquired to determine PWV. The EFV was measured based on a 3 D-mDixon sequence. Group comparisons were made between younger (age < 45y; n = 30; mean age 33.4 ± 6.6y) and older (> 45y; n = 28; 56.7 ± 8.4y) subjects and between subjects with a BMI < 25 kg/m² (n = 28; BMI 21.9 ± 2.5 kg/m²) and a BMI > 25 kg/m² (n = 30; 28.7 ± 4.0 kg/m²). Associations between the determined parameters were assessed by analyses of covariance (ANCOVAs).

Results: The mean values of PWV and EFV (normalized to body surface area) were 6.9 ± 1.9 m/s and 44.2 ± 25.0 ml/m², respectively. The PWV and EFV were significantly higher in the older group (PWV = 7.9 ± 2.0 m/s vs. 6.0 ± 1.2 m/s; EFV = 54.7 ml/m² vs. 34.5 ml/m²; p < 0.01, each), with no significant differences in BMI or sex. In the overweighted group the EFV was significantly higher than in subjects with a BMI < 25 kg/m² (EFV = 56.1 ± 27.1 ml/m² vs. 31.5 ± 14.6 ml/m²; p < 0.01) but without a significant difference in PWV. ANCOVA revealed a significant correlation between EFV and PWV, also after adjustment for age (p = 0.025).

Conclusion: An association was found between age and EFV as well as PWV. EFV and PWV were related to each other also after adjustment for age. The metabolic and pro-inflammatory activity found with increased epicardial fat volume may promote the development of atherosclerosis and aortic stiffness. CMR may be valuable for future studies investigating the relationship between EFV and PWV in patients with increased cardiovascular risk.

Key Points:

• EFV and PWV can be assessed in a single CMR exam.

• EFV and aortic stiffness are both associated with cardiovascular risk.

• EFV correlates with aortic stiffness, possibly due to similar pro-inflammatory mechanisms.

Citation Format:

• Homsi R, Thomas D, Gieseke J et al. Epicardial Fat Volume and Aortic Stiffness in Healthy Individuals: A Quantitative Cardiac Magnetic Resonance Study. Fortschr Röntgenstr 2016; 188: 853 – 858

Zusammenfassung

Ziel: Das Ziel war die Messung des epikardialen Fettvolumens sowie der aortalen Steifigkeit (bestimmt anhand der aortalen Pulswellengeschwindigkeit (PWV)) bei Gesunden, sowie die Untersuchung möglicher Zusammenhänge zwischen diesen Maßen, Body Mass Index (BMI) und Alter.

Material und Methoden: 58 gesunde Studienteilnehmer (29 Männer; mittleres Alter 44,7 ± 13,9 Jahre [J]) wurden mittels Kardio-MRT bei 1,5 Tesla untersucht. Die Berechnung der PWV erfolgte mittels 2D-Flussmessung. Das epikardiale Fettvolumen (EFV) wurde anhand einer 3D-mDixon-Sequenz ermittelt. Es erfolgte eine Gruppeneinteilung nach Alter in < 45 J (n = 30; 33,4 ± 6,6 J) und > 45 J (n = 28; 56,7 ± 8,4 J) sowie nach BMI in < 25 kg/m² (n = 28; BMI 21,9 ± 2,5 kg/m²) und > 25 kg/m² (n = 30; 28,7 ± 4,0 kg/m²). Die Gruppen wurden untereinander verglichen und Zusammenhänge wurden mittels Kovarianzanalysen untersucht.

Ergebnisse: Die Mittelwerte von PWV und EFV (bezogen auf die Körperoberfläche) waren 6,9 ± 1,9 m/s und 44,2 ± 25,0 ml/m². Die Gruppe der älteren Personen hatte signifikant höhere PWV- und EFV-Werte als die jüngere Gruppe (PWV = 7,9 ± 2,0 m/s vs. 6,0 ± 1,2 m/s; EFV = 54,7 ml/m² vs. 34,5 ml/m²; jeweils p < 0,01), ohne einen signifikanten Unterschied bezüglich BMI und Geschlecht. Übergewichtige Personen (BMI > 25 kg/m²) hatten signifikant höhere EFV-Werte als die Gruppe mit einem BMI < 25 kg/m² (EFV = 56,1 ± 27,1 ml/m² vs. 31,5 ± 14,6 ml/m²; p < 0,01), ohne signifikante Unterschiede in der PWV. Die Kovarianzanalyse zeigte eine signifikante Korrelation zwischen EFV und PWV, auch nach Adjustierung für das Alter (p = 0,025).

Schlussfolgerung: Das EFV und die PWV zeigen nicht nur einen Zusammenhang mit dem Alter, sondern auch untereinander, unabhängig vom Alter. Eine metabolische und pro-inflammatorische Aktivität bei erhöhtem epikardialem Fettvolumen könnte die Entwicklung einer Atherosklerose und einer erhöhten aortalen Steifigkeit verstärken. Die Kardio-MRT eignet sich zur Untersuchung der Zusammenhänge von EFV und PWV in weiterführenden Studien bei Patienten mit kardiovaskulären Risikofaktoren.

Kernaussagen:

• EFV und PWV können mittels Kardio-MRT in nur einer Untersuchung bestimmt werden.

• EFV und aortale Steifigkeit sind mit erhöhtem kardiovaskulärem Risiko verbunden.

• EFV und aortale Steifigkeit korrelieren miteinander, möglicherweise aufgrund gemeinsamer pro-inflammatorischer Mechanismen.

Key words

epicardial fat - aortic stiffness - CMR - pulse wave velocity - heart

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