Introduction: Cardiac sarcoidosis (CS) may initially present with cardiac symptoms, yet timely diagnosis remains challenging. Limited data are available on clinical worsening during the diagnostic delay.

Objectives: To evaluate clinical worsening and post-diagnosis outcomes in patients with early (≤6 months) versus late (>6 months) diagnosis of CS after first cardiac symptoms.

Materials and Methods: In this retrospective study at a tertiary referral centre, we included patients presenting with cardiac symptoms as the first manifestation of CS. Patients were stratified into early (≤6 months) and late (>6 months) diagnosis groups based on time from symptom onset to CS diagnosis. Clinical worsening during the diagnostic delay was defined as a decline in left ventricular function, new clinically relevant arrhythmias and/or conduction disturbances and was assessed in the late diagnosis group. Post-diagnosis outcomes were evaluated using a composite of cardiac death, ventricular arrhythmias, appropriate ICD therapy, heart failure hospitalization, LVAD implantation, or heart transplantation.

Results: Among 105 patients (mean age 53.0±9.3 years, 65.7% male), 72 (68.6%) had an early and 33 (31.4%) a late diagnosis. At first presentation, disease severity was comparable between groups, including similar rates of left ventricular (LV) dysfunction. In the late diagnosis group, high-degree AV block did not prompt etiological workup in 11 patients (33%), and 20 patients (60%) were assigned an alternative diagnosis (Figure 1). During the diagnostic delay, clinical worsening occurred in 57.6% of patients (Figure 2). At diagnosis, LVEF was significantly lower in the late versus early group (43.0% [33.0–45.0] vs 53.0% [39.5–60.0], p<0.01). Despite these differences, post-diagnosis outcomes were comparable during a median follow-up of 5.8 years.

Conclusions: Diagnostic delay in CS is associated with clinical worsening prior to diagnosis, particularly decline in LV function. These findings underscore the importance of early recognition and timely evaluation in patients with unexplained AV conduction block, ventricular arrhythmias, or LV dysfunction.