Influence of extracellular volume fraction on peak exercise oxygen pulse following thoracic radiotherapy.

Canada JM; Weiss E; Grizzard JD; Trankle CR; Gharai LR; Dana F; Buckley LF; Carbone S; Kadariya D; Ricco A; JH; Evans RK; Garten RS; Van Tassell BW; Hundley WG;Abbate A;

Cardio-oncology (London, England) [Cardiooncology] 2022 Jan 18; Vol. 8 (1), pp. 1.
Date of Electronic Publication: 2022 Jan 18.

Background: Radiation-induced myocardial fibrosis increases heart failure (HF) risk and is associated with a restrictive cardiomyopathy phenotype. The myocardial extracellular volume fraction (ECVF) using contrast-enhanced cardiac magnetic resonance (CMR) quantifies the extent of fibrosis which, in severe cases, results in a noncompliant left ventricle (LV) with an inability to augment exercise stroke volume (SV). The peak exercise oxygen pulse (O 2 Pulse), a noninvasive surrogate for exercise SV, may provide mechanistic insight into cardiac reserve. The relationship between LV ECVF and O 2 Pulse following thoracic radiotherapy has not been explored.
Methods: Patients who underwent thoracic radiotherapy for chest malignancies with significant incidental heart dose (≥5 Gray (Gy), ≥10% heart) without a pre-cancer treatment history of HF underwent cardiopulmonary exercise testing to determine O 2 Pulse, contrast-enhanced CMR, and N-terminal pro-brain natriuretic peptide (NTproBNP) measurement. Multivariable-analyses were performed to identify factors associated with O 2 Pulse normalized for age/gender/anthropometrics.
Results: Thirty patients (median [IQR] age 63 [57-67] years, 18 [60%] female, 2.0 [0.6-3.8] years post-radiotherapy) were included. The peak VO 2 was 1376 [1057-1552] mL·min - 1 , peak HR = 150 [122-164] bpm, resulting in an O 2 Pulse of 9.2 [7.5-10.7] mL/beat or 82 (66-96) % of predicted. The ECVF, LV ejection fraction, heart volume receiving ≥10 Gy, and NTproBNP were independently associated with %O 2 Pulse (P < .001).
Conclusions: In patients with prior radiotherapy heart exposure, %-predicted O 2 Pulse is inversely associated markers of diffuse fibrosis (ECVF), ventricular wall stress (NTproBNP), radiotherapy heart dose, and positively related to LV function. Increased LV ECVF may reflect a potential etiology of impaired LV SV reserve in patients receiving thoracic radiotherapy for chest malignancies.