Basal coronary microvascular resistance is associated with cardiac sympathetic innervation assessed by 123I-MIBG scintigraphy in patients with heart failure
T Nishikawa, H Kadohara, Y Ohga, M Shingu, Y Osumi, K Ishibashi, T Ishii, M Hiraishi, M Kinugasa, Y Hirayama, K TamitaAbstract
Background
Coronary microvascular abnormalities and sympathetic dysregulation are central to heart failure (HF) pathophysiology and risk. Invasive coronary physiology commonly focuses on hyperaemic indices such as coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR). However, resting microvascular resistance assessed by basal IMR (b-IMR) may reflect a distinct domain linked to baseline haemodynamics and neurohumoral activation. Cardiac 123I-metaiodobenzylguanidine (MIBG) scintigraphy provides markers of cardiac sympathetic innervation/activity, including washout rate (WR) and delayed heart-to-mediastinum (H/M) ratio, but their relationship with b-IMR in HF is unclear.
Purpose
To evaluate associations between b-IMR and MIBG-derived WR and delayed H/M ratio in HF, and to compare them with hyperaemic indices (IMR and CFR).
Methods
Single-centre retrospective cohort study. Consecutive patients undergoing invasive coronary physiology during cardiac catheterisation between Nov 2022 and Feb 2026 were screened (N=42); one patient on maintenance haemodialysis was excluded (final N=41). Patients were hospitalised for HF and studied in a stable phase after optimisation of HF therapy. Thermodilution-based physiology was performed to obtain CFR and IMR. b-IMR was defined as resting distal coronary pressure × resting mean transit time. Cardiac index was recorded from invasive haemodynamics when available. MIBG WR and delayed H/M ratio were calculated from background-subtracted and attenuation-corrected images/counts.
Results
Median age was 68 years (IQR 59–86) and 29 (71%) were male. Median BMI was 22.3 kg/m² (IQR 20.0–25.3) and NT-proBNP 1267 pg/mL (IQR 539–2528). Chronic kidney disease was present in 27 (66%) and diabetes mellitus in 9 (22%). LVEF was 34.0% (IQR 25.9–42.6). Most patients had heart failure with reduced ejection fraction; however, 7 (17%) had LVEF ≥50%. Median CFR was 2.9 (IQR 1.5–4.2), IMR 23 (IQR 13–39), and b-IMR 73.5 (IQR 47.9–111.0). b-IMR correlated inversely with WR (r = −0.37, p = 0.017) and positively with delayed H/M ratio (r = 0.31, p = 0.049). In contrast, neither WR nor delayed H/M ratio correlated with IMR or CFR, suggesting that sympathetic imaging markers relate preferentially to resting microvascular resistance.
Conclusions
In stabilized patients following HF hospitalization, higher resting microvascular resistance assessed by b-IMR was associated with cardiac sympathetic innervation/activity on 123I-MIBG scintigraphy, whereas IMR and CFR were not. These findings support the complementary value of b-IMR for HF phenotyping and suggest coupling between resting coronary microcirculation and cardiac sympathetic dysfunction.