The application of ballistocardiography (BCG) for unobtrusive monitor of (beat-to-beat) heart rate in sleeping subjects has seen increased attention in recent years. While most studies are performed on healthy volunteers, some studies have included subjects with sleep-related problems. Even so, little attention has been payed to patients suffering from cardiovascular diseases. In addition, most studies are either limited to short laboratory measurements or overnight recordings of sleeping subjects.In this work, we present preliminary results on beat-to-beat interval estimation of long-term (> 21 h) BCG recordings in a hospital environment. Measurements were obtained from five subjects after peripheral vascular surgery or endovascular interventions and compared to Holter recordings. The commercially available sensor Emfit QS as well an augmented version of the CLIE interval estimation algorithm were used. Using the proposed approach, an average relative beat-to-beat interval error of 3.8 % at a coverage of 61.5 % was achieved. Error and coverage were found to vary from subject to subject as well as time of day. On average, findings are comparable though inferior to results reported on insomniac subjects in a sleep laboratory environment.