Background The Plan–Do–Study–Act (PDSA) cycle is an iterative framework that has been gaining traction in primary care for quality improvement. However, its implementation remains understudied. This study evaluated the completion, achievement of goal, content quality, and enablers and barriers associated with completion of high-quality PDSA cycles in cardiovascular disease management in general practices. Methods This study analysed data from intervention practices of the QUality improvement in primary care to prevent hospitalisations and improve Effectiveness and efficiency of care for people Living people with coronary heart disease (QUEL) study. Content quality of cycles was assessed using a scoring system created based on established criteria of ideal PDSA cycles in the healthcare context. Practice-level factors associated with completion and cycles achieving the planned goal were explored through logistic regression models, and with content quality score through linear regression model. Enablers and barriers were assessed using thematic analysis of practices’ responses to the PDSA sections. Results Ninety-seven cycles were reported by 18/26 (69%) practices. Seventy-seven percent of the cycles were completed and 68% achieved the planned goal. Content quality was low, with a median score of 56% (interquartile interval: 44%, 67%). Odds of cycles that were completed and achieved what was planned increased by 3.6- and 9.6-fold, respectively, with more general practitioners (GPs) within practices. Content quality was higher by 15% with more GPs. Lack of interprofessional engagement was a barrier to implementation. Conclusions Cycles were well completed, but poor in content quality, with high variability between practices. Human or capital resources and organisational support may be critical for the completion and cycles achieving the planned goals.