Background Valvular heart disease and intracardiac shunts can disrupt the balance between left ventricular (LV) and right ventricular (RV) stroke volumes. However, the prognostic value of such imbalances has not been established among asymptomatic individuals. Purpose To assess the association between differential ventricular stroke volumes quantified using cardiac MRI and clinical outcomes in individuals without cardiovascular disease. Materials and Methods This secondary analysis of a prospective study included participants without cardiovascular disease at enrollment (July 2000 to July 2002) who underwent cardiac MRI. Differences in stroke volume were calculated as LV stroke volume minus RV stroke volume, and participants were categorized as having balanced (greater than or equal to -30 mL to ≤30 mL), negative (less than -30 mL), or positive (>30 mL) differential stroke volumes. Multivariable Cox proportional hazard regression models were used to test the association between differences in stroke volume and adverse outcomes. Results A cohort of 4058 participants (mean age, 61.4 years ± 10 [SD]; 2120 female) were included and followed up for a median of 18.4 years (IQR, 18.3-18.5 years). During follow-up, 1006 participants died, 235 participants developed heart failure, and 764 participants developed atrial fibrillation. Compared with participants who had a balanced differential stroke volume, those with an increased differential stroke volume showed a higher risk of mortality (hazard ratio [HR], 1.73 [95% CI: 1.12, 2.67]; P = .01), heart failure (HR, 2.40 [95% CI: 1.11, 5.20]; P = .03), and atrial fibrillation (HR, 1.89 [95% CI: 1.16, 3.08]; P = .01) in adjusted models. Participants in the negative group, with a decreased differential stroke volume, showed an increased risk of heart failure compared with those in the balanced group (HR, 2.09 [95% CI: 1.09, 3.99]; P = .03); however, this was no longer observed after adjusting for baseline LV function (P = .34). Conclusion Participants without cardiovascular disease at the time of study enrollment who had an LV stroke volume exceeding the RV stroke volume by greater than 30 mL had an increased risk of mortality, heart failure, and atrial fibrillation compared with those with balanced stroke volumes. ClinicalTrials.gov Identifier: NCT00005487 © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Almeida in this issue.