99 mTc-FAPI SPECT/CT for Evaluation of Myocardial Fibrosis and Cardiac Function in Valvular Heart Disease

Background Active myocardial fibrosis plays a pivotal role in valvular heart disease (VHD) progression. While conventional imaging modalities primarily detect established fibrosis, the detection of active fibroblast activation remains challenging. 99 mTc-FAPI SPECT/CT, offering advantages of wider availability and lower cost compared to PET imaging, represents a promising tool for evaluating active myocardial fibrosis. Methods We conducted a prospective study of 30 VHD patients who underwent 99 mTc-FAPI SPECT/CT imaging with comprehensive clinical evaluation. Patients were categorized into FAPI-positive (n=24) and FAPI-negative (n=6) groups based on myocardial tracer uptake patterns. Thirteen FAPI-positive patients completed a three-month follow-up to assess therapeutic response. Results FAPI uptake parameters showed robust correlations with established myocardial injury markers (Hs-cTnI vs SUVmax: r=0.831, p<0.001; vs SUVmean: r=0.795, p<0.001) and disease severity indices (VHD staging: r=0.812, p<0.001). FAPI-positive patients demonstrated significantly higher atrial fibrillation prevalence (54.2% vs 0%, P=0.024). Post-treatment follow-up revealed significant improvements in FAPI parameters (SUVmax: 2.8±0.4 to 1.9±0.3, p<0.0001; SUVmean: 2.3±0.3 to 1.6±0.2, p<0.0001), accompanied by enhanced left ventricular ejection fraction (45.3±5.2% to 52.1±4.8%, p=0.0176) and NYHA functional status (p=0.0011), despite unchanged structural parameters. Conclusions This study demonstrates that 99 mTc-FAPI SPECT/CT enables non-invasive visualization and quantification of active myocardial fibrosis in VHD patients. The strong associations between FAPI parameters and clinical indices, coupled with its ability to monitor therapeutic response, suggest its potential as a valuable tool for risk stratification and treatment optimization in VHD management. Trial registration ChiCTR2400094867. Registered 30 December 2024. Public site: https://www.chictr.org.cn/index.html .