Myocardial flow reserve estimation with contemporary CZT-SPECT and 99m Tc-tracers lacks precision for routine clinical application

J Nucl Cardiol. 2021 Aug 23. doi: 10.1007/s12350-021-02761-0. Online ahead of print.


Background: PET myocardial flow reserve (MFR) has established diagnostic and prognostic value. Technological advances have now enabled SPECT MFR quantification. We investigated whether SPECT MFR precision is sufficient for clinical categorization of patients.

Methods: Validation studies vs invasive flow measurements and PET MFR were reviewed to determine global SPECT MFR thresholds. Studies vs PET and a SPECT MFR repeatability study were used to establish imprecision in SPECT MFR measurements as the standard deviation of the difference between SPECT and PET MFR, or test-retest SPECT MFR. Simulations were used to evaluate the impact of SPECT MFR imprecision on confidence of clinically relevant categorization.

Results: Based on validation studies, the typical PET MFR categories were used for SPECT MFR classification (< 1.5, 1.5-2.0, > 2.0). Imprecision vs PET MFR ranged from 0.556 to 0.829, and test-retest imprecision was 0.781-0.878. Simulations showed correct classification of up to only 34% of patients when 1.5 ≤ true MFR ≤ 2.0. Categorization with high confidence (> 80%) was only achieved for extreme MFR values (< 1.0 or > 2.5), with correct classification in only 15% of patients in a typical lab with MFR of 1.8 ± 0.5.

Conclusions: Current SPECT-derived estimates of MFR lack precision and require further optimization for clinical risk stratification.

背景: PET 心肌血流储备 (Myocardial Flow Reserve, MFR)诊断和预后价值已经明确。SPECT MFR 的量化随着技术的进步也已实现。我们探讨 SPECT MFR 精度能否满足对患者进行临床分类。 方法: 回顾有创血流测量和PET-MFR对比的研究来确定SPECT的整体MFR阈值。PET和SPECT-MFR重复性研究用于确定SPECT-MFR测量的不精确性, 并以此作为SPECT和PET-MFR之间或SPECT-MFR的重测差异的标准差。模拟用来评估SPECT MFR的不精确性对临床相关分类可信度的影响。 结果: 在验证研究中, SPECT-MFR分类采用典型PET-MFR分类 (< 1.5, 1.5-2.0, > 2.0)。对比PET-MFR, 不精确度的比值范围为0.556∼0.829, 重测不精确度为0.781∼0.878。模拟显示, 当 1.5≤真实 MFR≤2.0时, 正确分类的患者只有 34%。 在MFR值为1.8±0.5的典型实验模拟中, 只有15%的患者进行了正确的分类, 只有极端的MFR值 (< 1.0或 >2.5) 才能实现高置信度分类 (>80%)。 结论: 目前SPECT估计得出的MFR缺乏精确性, 用于临床风险分层尚需要进一步优化。.

Keywords: Myocardial flow reserve; SPECT; coronary flow reserve; myocardial perfusion imaging.