Stress pulmonary circulation parameters assessed by a cardiovascular magnetic resonance in patients after a heart transplant

Abstract

Rest pulmonary circulation parameters such as pulmonary transit time (PTT), heart rate corrected PTT (PTTc) and pulmonary transit beats (PTB) can be evaluated using several methods, including the first-pass perfusion from cardiovascular magnetic resonance. As previously published, up to 58% of patients after HTx have diastolic dysfunction detectable only in stress conditions. By using adenosine stress perfusion images, stress analogues of the mentioned parameters can be assessed. By dividing stress to rest biomarkers, potential new ratio parameters (PTT ratio and PTTc ratio) can be obtained. The objectives were to (1) provide more evidence about stress pulmonary circulation biomarkers, (2) present stress to rest ratio parameters, and (3) assess these biomarkers in patients with presumed diastolic dysfunction after heart transplant (HTx) and in childhood cancer survivors (CCS) without any signs of diastolic dysfunction. In this retrospective study, 48 patients after HTx, divided into subgroups based on echocardiographic signs of diastolic dysfunction (41 without, 7 with) and 39 CCS were enrolled. PTT was defined as the difference between the onset time of the signal intensity increase in the left and the right ventricle. PTT in rest conditions were without significant differences when comparing the CCS and HTx subgroup without diastolic dysfunction (4.96 ± 0.93 s vs. 5.51 ± 1.14 s, p = 0.063) or with diastolic dysfunction (4.96 ± 0.93 s vs. 6.04 ± 1.13 s, p = 0.13). However, in stress conditions, both PTT and PTTc were significantly lower in the CCS group than in the HTx subgroups, (PTT: 3.76 ± 0.78 s vs. 4.82 ± 1.03 s, p < 0.001; 5.52 ± 1.56 s, p = 0.002). PTT ratio and PTTc ratio were below 1 in all groups. In conclusion, stress pulmonary circulation parameters obtained from CMR showed prolonged PTT and PTTc in HTx groups compared to CCS, which corresponds with the presumption of underlying diastolic dysfunction. The ratio parameters were less than 1.

Stress and Rest Pulmonary Transit Times Assessed by Cardiovascular Magnetic Resonance

“…While the CMR-derived pulmonary circulation parameters do not assess cardiac pathology, recent studies [14][15][16][17]22,23,28 demonstrate their potential as supplementary tools for stratifying patients…”

“…So far, the most advanced and convenient way to measure pulmonary circulation parameters is with first-pass perfusion sequences in cardiovascular magnetic resonance imaging (CMR). [14][15][16][17]22,23 This method has two substantial advantages. Firstly, it offers a further use of already established and used sequences; the patient does not require special examinations or additional acquisitions.…”

“…23 The second study, by Opatřil et al, compared patients one year after HTx and CCS without systolic or diastolic dysfunction, reporting lower PTT stress values than resting ones in both groups. 17 In addition, a significant prolongation of these stress parameters was reported in the HTx group compared to the CCS group. 17 The authors suggested diastolic dysfunction as one possible explanation.…”

“…17 The authors suggested diastolic dysfunction as one possible explanation. 17 Although adenosine has vasodilatory effects on pulmonary circulation, 14,32 this effect did not explain the prolongation of PTT stress in the CCS group without systolic or diastolic dysfunction. 17 The third study, by Seraphim et al, reported data from 963 patients, with results of a shorter PTT stress when compared to rest values, further documenting this concern.…”

“…Their prolongation has been reported in various cardiac conditions. [14][15][16][17] In the future, this approach could be a promising indicator of heart function and, potentially, of the entire cardiopulmonary system.…”