Cross-modality comparisons of coronary and myocardial flow reserve – a systematic review and meta-analysis
S Sorensen, J H S Soby, L D R Dupont Rasmussen, M B Bottcher, S W WintherAbstract
Background
The 2024 European Society of Cardiology guidelines for chronic coronary syndrome highlight the importance of diagnosing ischemia in patients with angina and non-obstructive coronary arteries (ANOCA). Invasive coronary arteriography (ICA) with coronary functional testing has a Class I, Level of evidence B recommendation for diagnosing ANOCA endotypes without considering the invasive method. In contrast, PET holds a Class I, Level of evidence B recommendation for quantifying myocardial blood flow, but non-invasive imaging methods only hold a Class IIb, Level of evidence B recommendation for diagnosing endotypes in ANOCA patients. Hence, the optimal diagnostic approach for assessing microvascular angina (MVA) remains uncertain.
Purpose
To conduct a systematic review and meta-analysis of head-to-head studies comparing non-invasive and invasive quantitative perfusion modalities for diagnosing MVA and to investigate correlations and assess agreement between modalities.
Methods
PubMed was systematically searched to identify head-to-head comparison studies. Studies reporting global coronary flow reserve or LAD-territory flow reserve measured by Doppler were included. Correlation strength was predefined, with strong correlation defined as ρ > 0.70.
Results
A total of 39 studies were identified. Positron Emission Tomography (PET) was most frequently used as the reference modality (n=17), including comparisons among different PET tracers (n=8). Comparisons of bolus thermodilution ICA with continuous thermodilution ICA and doppler ICA were frequent (n=10), whereas only one direct comparison between continuous thermodilution ICA and doppler ICA was identified. Overall, only a few studies (n=8) evaluated correlations between invasive and non-invasive modalities. In general, bolus thermodilution ICA demonstrated weak correlation with continuous thermodilution ICA and moderate correlation with doppler ICA. Bolus thermodilution ICA showed weak-to-moderate correlations with PET, cardiac magnetic resonance (CMR) and transthoracic doppler echocardiography, whereas both continuous thermodilution ICA and doppler ICA demonstrated strong correlations with PET. Also, doppler ICA showed strong correlations with CMR and transthoracic doppler echocardiography. Correlations among non-invasive modalities were generally moderate without a consistent pattern.
Conclusion
Bolus thermodilution ICA appears suboptimal for the assessment of MVA due to a lack of correlation to all other modalities. Continuous thermodilution ICA and doppler ICA demonstrate strong correlations with PET; however, the available evidence is limited. Further head-to-head studies including PET, thermodilution ICA and doppler ICA are warranted to establish reference standards for quantifying myocardial and coronary flow reserve and identify the optimal diagnostic strategy for patients with suspected MVA.Flowchart_modalities