Reduced intrathoracic blood volume and left and right ventricular dimensions in patients with severe emphysema: an MRI study.

BACKGROUND: Left ventricular (LV) filling is impaired in patients with severe emphysema manifesting in small end-diastolic dimensions. We hypothesized that the hyperinflated lungs of these patients with high intrinsic positive end-expiratory pressure will decrease intrathoracic blood volume (ITBV) and ventricular preload. We therefore measured ITBV, and LV and right ventricular (RV) dimensions and function using MRI techniques in patients with severe emphysema.
METHODS: Patients with severe emphysema (n = 13) and matched healthy volunteers (n = 11) were included. The magnetic resonance (MR) examination consisted of three parts: (1) evaluation of RV and LV dimensions and function and interventricular septum curvature using cine MRI; (2) quantification of aortic flow using MR phase velocity mapping; and (3) calculation of the cardiopulmonary peak transit time (PTT) from the pulmonary artery to the ascending aorta using contrast-enhanced, time-resolved, two-dimensional MR angiography.
RESULTS: There were no differences between the groups regarding age, height, or weight. In the emphysema patients, ITBV index (- 35%), LV end-diastolic volume index (LVEDVI) [- 21%], RV end-diastolic volume index (- 20%), cardiac index (- 22%), and stroke volume index (SVI) [- 40%] were lower compared to control subjects. LV and RV end-systolic volumes, LV wall mass, septal curvature, and PTT did not differ between the groups. LVEDVI (r = 0.83) as well as SVI (r = 0.82) correlated closely to ITBV index. SVI correlated closely to LVEDVI (r = 0.84).
CONCLUSIONS: LV and RV performance is impaired in patients with severe emphysema because of small end-diastolic dimensions. One possible explanation for the decreased biventricular preload in these patients is intrathoracic hypovolemia caused by hyperinflated lungs.