BACKGROUND: In an attempt to deal with the pressures on the healthcare system and to guarantee sustainability, changes are needed. This study is focused on a cardiology Primary Care Plus intervention in which cardiologists provide consultations with patients in a primary care setting in order to prevent unnecessary referrals to the hospital. This study explores which patients with non-acute and low-complexity cardiology-related health complaints should be excluded from Primary Care Plus and referred directly to specialist care in the hospital. METHODS: This is a retrospective observational study based on quantitative data. Data collected between January 1 and December 31, 2015 were extracted from the electronic medical record system. Logistic regression analyses were used to select patient groups that should be excluded from referral to Primary Care Plus. RESULTS: In total, 1525 patients were included in the analyses. Results showed that male patients, older patients, those with the referral indication 'Stable Angina Pectoris' or 'Dyspnoea' and patients whose reason for referral was 'To confirm disease' or 'Screening of unclear pathology' had a significantly higher probability of being referred to hospital care after Primary Care Plus. CONCLUSIONS: To achieve efficiency one should exclude patient groups with a significantly higher probability of being referred to hospital care after Primary Care Plus. TRIAL REGISTRATION NUMBER: NTR6629 (Data registered: 25-08-2017) (registered retrospectively).