Original ArticleQuantitative flow ratio derived pullback pressure gradient and CZT-SPECT measured longitudinal flow gradient for hemodynamically significant coronary artery disease
Introduction
Coronary atherosclerotic plaque formation and progression causes coronary luminal narrowing and decrease in myocardial blood supply,1 thus previous concerns have focused on the identification of myocardial ischemia and treatment of stenosis.2 Nevertheless, myocardial ischemia may happen in the absence of focal epicardial disease,3 which is related with diffuse coronary atherosclerosis. Notably, diffuse coronary artery disease (CAD) jeopardizes myocardium and is the substrate for plaque rupture and coronary events.4,5 In this regard, it might be equally important to assess the plaque distribution (focal or diffuse) as the cumulative total disease burden.
Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) myocardial perfusion imaging are important clinical tools that allow the noninvasive evaluation of myocardial perfusion. Beyond that, longitudinal, base-to-apex myocardial blood flow (MBF) gradient has previously been observed in CAD patients6,7 and been attributed to fluid dynamic consequences of diffuse coronary luminal narrowing.8, 9, 10, 11, 12
Recently, quantitative flow ratio (QFR), which is the angiography-derived fractional flow reserve (FFR), has been validated as an index for assessing the functional significance of coronary atherosclerosis. Aside from its value in identifying myocardial ischemia, functional diffuseness could also be quantified by pullback pressure gradient (PPG) derived from the virtual QFR pullback curve (QFR-PPG).13,14 However, its diagnostic value and relationship with longitudinal MBF gradient has not been validated adequately yet.
Thus, we aimed to investigate the association of physiological coronary diffuseness assessed by QFR-PPG with longitudinal MBF gradient, as well as their values in predicting the presence of physiologically significant CAD.
Section snippets
Study design and population
The study population included patients with suspected or known stable CAD from Zhongshan Registry of cadmium-zinc-telluride SPECT (CZT-SPECT).15 As shown in Figure 1, after excluding patients with history of percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG), chronic total occlusion, left-dominant coronary anatomy, and inadequate quality of CZT-SPECT images, 50 patients (150 vessels) with dynamic CZT-SPECT for myocardial blood flow measurements within 7 days of
Study population characteristics
Among the initial study population, 30 of 150 (20%) vessels were excluded for technical issues, and measurements of longitudinal flow gradient by CZT-SPECT were successful in all patients. In total, 28 patients with 34 vessels were included in the analysis. The clinical and physiologic characteristics were shown in Table 1. Mean age was 64.1 ± 9.5 years, 67.9% were male. The global MFR and stress MBF were 2.16 ± 0.53 and 2.37 ± 0.75, respectively. Regarding the angiography derived parameters,
Discussion
The current study investigated the association of three parameters (QFR-PPG, hyperemic longitudinal MBF gradient and △longitudinal MBF gradient) for functional coronary diffuseness assessment. Furthermore, their values in predicting the presence of physiologically significant CAD were explored.
The key findings were: (1) QFR-PPG was significantly correlated with hyperemic longitudinal MBF gradient and △longitudinal MBF gradient; (2) QFR-PPG, hyperemic longitudinal MBF gradient and △longitudinal
Conclusion
QFR-PPG significantly correlated with longitudinal MBF gradient and △longitudinal MBF gradient when used for physiological coronary diffuseness assessment. All of them showed comparable and high accuracy in predicting hemodynamically significant CAD determined by RFR or QFR. Adding functional diffuseness assessment increased the diagnostic ability for myocardial ischemia.
New knowledge gained
The current study showed the feasibility of functional coronary diffuseness assessments by quantitative flow ratio derived pullback pressure gradient and CZT-SPECT measured longitudinal flow gradient. These two parameters correlated significantly and increased the accuracy in predicting hemodynamically significant coronary artery disease. Integrating coronary physiology, longitudinal pressure, and perfusion gradients might provide a novel insight for diagnosing myocardial ischemia and
Acknowledgments
None
Funding
This work was supported by National Key Research and Development Program of China from the Ministry of Science and Technology of the People’s Republic of China (Grant Number [2020YFC1316700]), Anhui Provincial Key Research and Development Project (Grant Number [2022e07020009]) and China Cardiovascular Health Alliance-Access Research Fund (Grant Number [2020-CCA-ACCESS-124]).
Disclosure
Neng Dai, Gong Zifan, Zheng Dong, Xianglin Tang Haojun Yu, Taoying Gu, Shaofeng Duan, Juying Qian, Hongcheng Shi, and
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Neng Dai, Buchun Zhang, and Zifan Gong contributed equally.
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