Background: In conventional left ventricular assist devices (LVADs) a separate outflow graft is sutured to the aorta. Novel device designs may include intracardiac outflow grafts crossing the aortic valve. While transversal ventricular dimensions are well investigated in patients undergoing LVAD implantation, little is known about the longitudinal cardiac dimensions. These dimensions are, however, particularly critical for the design of LVADs with transaortic outflow graft. We characterized the longitudinal dimensions in patients with dilated cardiomyopathy prior to LVAD implantation. Methods: In an explorative retrospective cohort study at the University Medical Center Freiburg, Germany, the longitudinal cardiac dimensions in patients undergoing computed tomography angiography (CTA) between 06/2002 and 06/2021 prior to LVAD implantation were analyzed. In 14 patients, a postoperative CTA was performed. Figure A and B show the measured dimensions: (a) apex to aortic valve (AV), (b) apex to mitral valve, (c) aortic valve to sinotubular junction (STJ), (d) apex to sinotubular junction, (e) apex to brachiocephalic artery (BCA) and (f) aortic valve to brachiocephalic artery. Correlation between these dimensions and body height was calculated (R, Austria). Results: In total, 44 patients (36 male, age 55.8 years, height 1.75 m) were included. The longitudinal cardiac dimensions measured were (a) 114.5 ± 11.9 mm, (b) 108.0 ± 12.3 mm, (c) 20.9 ± 2.8, (d) 135.4 ± 13.2 mm, (e) 206.0 ± 18.1 and (f) 91.5 ± 9.7 mm. Among LVAD patients these dimensions varied by 12 mm (c) to 72 mm (e). As shown in Figure C, a moderate correlation was found between the selected dimensions and body height. Postoperatively, the distances (a) and (b) decreased by 31.5 and 39.5 %, respectively (n = 14). Conclusions: The analysis presents data about the preoperative longitudinal cardiac dimensions in patients with dilated cardiomyopathy undergoing LVAD implantation, and provides an estimate about changes after LVAD support. A better knowledge of these dimensions and their postoperative alterations may improve surgical planning of patients undergoing LVAD implantation, and helps to design assist devices with transaortic outflow graft.