Original Article
Quantitative flow ratio derived pullback pressure gradient and CZT-SPECT measured longitudinal flow gradient for hemodynamically significant coronary artery disease

https://doi.org/10.1007/s12350-023-03245-zGet rights and content

Abstract

Background

Whether physiological coronary diffuseness assessed by quantitative flow reserve (QFR) pullback pressure gradient (PPG) correlates with longitudinal myocardial blood flow (MBF) gradient and improves diagnostic performances for myocardial ischemia remains unknown.

Methods and results

MBF was measured in mL g−1 min−1 with 99mTc-MIBI CZT-SPECT at rest and stress, corresponding myocardial flow reserve (MFR = MBF stress/MBF rest) and relative flow reserve (RFR = MBF stenotic area/MBF reference) were calculated. Longitudinal MBF gradient was defined as apical and basal left ventricle MBF gradient. △longitudinal MBF gradient was calculated by longitudinal MBF gradient at stress and rest. QFR-PPG was acquired from virtual QFR pullback curve. QFR-PPG significantly correlated with hyperemic longitudinal MBF gradient (r = 0.45, P = 0.007) and △longitudinal MBF gradient (stress-rest) (r = 0.41, P = 0.016). Vessels with lower RFR had lower QFR-PPG (0.72 vs. 0.82, P = 0.002), hyperemic longitudinal MBF gradient (1.14 vs. 2.22, P = 0.003) and △longitudinal MBF gradient (0.50 vs. 1.02, P = 0.003). QFR-PPG, hyperemic longitudinal MBF gradient and △longitudinal MBF gradient showed comparable diagnostic performances for predicting decreased RFR (area under curve [AUC]: 0.82 vs. 0.81 vs. 0.75, P = NS) or QFR (AUC: 0.83 vs. 0.72 vs. 0.80, P = NS). In addition, QFR-PPG and QFR in combination showed incremental value compared with QFR for predicting RFR (AUC = 0.83 vs. 0.73, P = 0.046, net reclassification index = 0.508, P = 0.001).

Conclusion

QFR-PPG significantly correlated with longitudinal MBF gradient and △longitudinal MBF gradient when used for physiological coronary diffuseness assessment. All three parameters had high accuracy in predicting RFR or QFR. Adding physiological diffuseness assessment increased accuracy for predicting myocardial ischemia.

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

References (37)

  • TangG

    Nuclear cardiology in China: 2017

    J Nucl Cardiol

    (2017)
  • ZavadovskyKV et al.

    Absolute myocardial blood flows derived by dynamic CZT scan vs invasive fractional flow reserve: Correlation and accuracy

    J Nucl Cardiol

    (2021)
  • FearonWF et al.

    Fractional flow reserve and "hard" endpoints

    J Am Coll Cardiol

    (2020)
  • ColletC et al.

    Measurement of hyperemic pullback pressure gradients to characterize patterns of coronary atherosclerosis

    J Am Coll Cardiol

    (2019)
  • LozanoI et al.

    Diffuse coronary artery disease not amenable to revascularization: long-term prognosis

    Rev Esp Cardiol (Engl Ed)

    (2015)
  • LibbyP et al.

    Atherosclerosis

    Nat Rev Dis Primers

    (2019)
  • LawtonJS et al.

    2021 ACC/AHA/SCAI guideline for coronary artery revascularization: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

    Circulation

    (2022)
  • De BruyneB et al.

    Abnormal epicardial coronary resistance in patients with diffuse atherosclerosis but "Normal" coronary angiography

    Circulation

    (2001)
  • Cited by (0)

    Neng Dai, Buchun Zhang, and Zifan Gong contributed equally.

    The authors of this article have provided a PowerPoint file, available for download at SpringerLink, which summarises the contents of the paper and is free for re-use at meetings and presentations. Search for the article DOI on SpringerLink.com.

    The authors have also provided an audio summary of the article, which is available to download as ESM, or to listen to via the JNC/ASNC Podcast.

    Copyright comment Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

    View full text