Physiologic assessment of moderate coronary lesions: a step towards complete revascularization in coronary artery bypass grafting

Fractional flow reserve and instantaneous wave-free ratio in coronary artery bypass grafting: a meta-analysis and practice review

Objective

Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are invasive methods to assess the functional significance of intermediate severity coronary lesions. Both indexes have been extensively validated in clinical trials in guiding revascularisation in patients with stable ischaemic heart disease undergoing percutaneous coronary intervention (PCI) with improved clinical outcomes. However, the role of these tools in coronary artery bypass grafting (CABG) is less clear.

Methods

A meta-analysis of randomised trials and observational studies was carried out to help in determining the optimal strategy for assessing lesion severity and selecting graft targets in patients undergoing CABG. Electronic searches were carried out on Embase, MEDLINE, and Web of Science. A group of four authors independently screened and then assessed the retrieved records. Cochrane's Risk of Bias and Robins-I tools were used for bias assessment. A survey was conducted among surgeons and cardiologists to describe current attitudes towards the preoperative use of functional coronary investigations in practice.

Results

Clinical outcomes including mortality at 30 days, perioperative myocardial infarction, number of grafts, incidence of stroke, rate of further need for revascularisation, and patient-reported quality of life did not differ in CABG guided by functional testing from those guided by traditional angiography.The survey revealed that in half of the surgical and cardiology units functional assessment is performed in CABG patients; there is a general perception that functional testing has improved patient care and its use would clarify the role of moderate coronary lesions that often need multidisciplinary rediscussions; moderate stenosis are felt to be clinically relevant; and anatomical considerations need to be taken into account together with functional assessment.

Conclusions

At present, the evidence to support the routine use of functional testing in intermediate lesions for planning CABG is currently insufficient. The pooled data currently available do not show an increased risk in mortality, myocardial injury, and stroke in the FFR/iFR-guided group. Further trials with highly selected populations are needed to clarify the best strategy.

Systematic Review Registration

ClinicalTrials.gov, identifier (CRD42023414604).

Enxerto de Bypass de Artéria Coronária Guiado por Angiografia ou Fisiologia: Uma Metanálise

Fundamento:

Enquanto a angiografia coronária invasiva é considerada padrão outro para o diagnóstico da doença arterial coronariana (DAC), envolvendo os vasos coronários epicárdicos, a revascularização coronariana guiada por fisiologia representa uma prática padrão ouro contemporânea para a administração invasiva de pacientes com DAC intermediária. Porém, os resultados de longo prazo da avaliação da gravidade da estenose por meio da fisiologia, em comparação à angiografia como guia para a cirurgia de bypass – enxerto de bypass de artéria coronária (CABG), ainda são incertos. Esta metanálise visa avaliar os resultados clínicos de um CABG guiado por fisiologia em comparação a um CABG guiado pela angiografia.

Objetivos:

Buscamos determinar se os resultados entre um CABG guiado por fisiologia e os de um CABG guiado por angiografia são diferentes entre si.

Métodos:

Pesquisamos nas bases Medline, EMBASE e Cochrane Library. A última data de busca foi junho de 2020, e todos os estudos anteriores foram incluídos. Realizamos uma metanálise de razão de risco agrupado para quatro principais resultados: morte por todas as causas, infarto do miocárdio (IM), revascularização do vaso alvo (TVR) e eventos cardiovasculares adversos maiores (MACE). Valor de p <0,05 foi considerado estatisticamente significante. A heterogeneidade foi avaliada com o teste Q de Cochran, e quantificada pelo índice I2.

Resultados:

Identificamos cinco estudos incluindo um total de 1.114 pacientes. Uma metanálise agrupada não demonstrou diferenças significativas entre a estratégia da fisiologia e da angiografia para IM (razão de risco [RR] = 0,72; IC95%, 0,39–1,33; I2 = 0%; p = 0,65), TVR (RR = 1,25; IC95% = 0,73–2,13; I2 = 0%; p = 0,52), ou MACE (RR = 0,81; IC95% = 0,62–1,07; I2 = 0%; p = 1). A estratégia da fisiologia apresentou 0,63 vezes o risco de morte por todas as causas em comparação à estratégia da angiografia (RR = 0,63; IC95% = 0,42–0,96; I2 = 0%; p = 0,55).

Conclusão:

Esta metanálise demonstrou uma redução nas mortes por todas as causas quando usada a estratégia do CABG guiado por fisiologia. Porém, o curto período de acompanhamento, o tamanho da amostra pequeno dos estudos incluídos e a não-discriminação das causas de morte podem justificar essas conclusões. Estudos com períodos mais longos de acompanhamento são necessários para tirar conclusões mais robustas e definitivas.

Fractional flow reserve guided versus angiographic guided surgical revascularization: A meta-analysis

BACKGROUND

Clinical benefits of FFR (Fraction Flow Reserve) driven CABG (Coronary Artery Bypass Graft) remain to be established.

METHODS

All randomized controlled trials (RCTs) and observational studies with multivariable adjustement were included. MACE (Major Adverse Cardiac Events) was the primary end point, while its single components (death, myocardial infarction, and total vessel revascularization [TVR]) along with number of anastomoses, on pump procedures and graft occlusion at angiographic follow-up were the secondary ones. Each analysis was stratified for RCTs versus observational studies.

RESULTS

Four studies (two RCTs and two observational) were included, enrolling 983 patients, 542 angio-guided and 441 FFR-guided. Mean age was 68.45 years, 79% male, with a mean EuroSCORE I of 2.7. Coronary lesions were located in 37% of patients in the left anterior descending artery, 32% in the circumflex artery, and 26% in the right coronary artery. After a mean follow-up of 40 months, risk of MACE did not differ (OR 0.86 [0.63-1.18]) as that of all cause death (OR 0.86 [0.59-1.25]), MI (OR 0.57 [0.30-1.11]) and TVR (OR 1.10 [0.65-1.85]). FFR-driven CABG reduced on-pump procedures (OR 0.58 [0.35-0.93]) and number of anastomoses (-0.40 [-0.80: -0.01]) while incidence of graft occlusion at follow-up did not differ (OR 0.59 [0.30-1.15], all CI 95%).

CONCLUSION

Fraction flow reserve driven CABG reduced the number of anastomoses and of on-pump procedures without increasing risk of MACE and without reducing graft occlusion at angiographic follow-up. ID CRD42020211945.

The role of fractional flow reserve in coronary artery bypass graft surgery: a meta-analysis

OBJECTIVES

Fractional flow reserve (FFR) measures the drop in perfusion pressure across a stenosis, therefore representing its physiological effect on myocardial blood flow. Its use is widespread in percutaneous coronary interventions, though its role in coronary artery bypass graft (CABG) surgery remains uncertain. This systematic review and meta-analysis aims to evaluate current evidence on outcomes following FFR-guided CABG compared to angiography-guided CABG.

METHODS

A literature search was conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to identify all relevant articles. Patient demographics and characteristics were extracted. The following outcomes were analysed: repeat revascularization, myocardial infarction (MI) and all-cause mortality. Pooled relative risks were analysed and their 95% confidence intervals (CIs) were estimated using random-effects models; P-value <0.05 was considered statistically significant. Heterogeneity was assessed with Cochran's Q score and quantified by I2 index.

RESULTS

Nine studies with 1146 patients (FFR: 574, angiography: 572) were included. There was no difference in MI or repeat revascularization between the 2 groups (relative risk 0.76, 95% CI 0.41-1.43; P = 0.40, and relative risk 1.28, 95% CI 0.75-2.19; P = 0.36, respectively). There was a significant reduction in all-cause mortality in the FFR-guided CABG group compared to angiography-guided CABG, which was not specifically cardiac related (relative risk 0.58, 95% CI 0.38-0.90; P = 0.02).

CONCLUSIONS

There was no reduction in repeat revascularization or postoperative MI with FFR. In this fairly small cohort, FFR-guided CABG provided a reduction in mortality, but this was not reported to be due to cardiac causes. There may be a role for FFR in CABG, but large-scale randomized trials are required to establish its value.

Evaluation of Myocardial Ischemia with iFR (Instantaneous Wave-Free Ratio in the Catheterization Laboratory: A Pilot Study

BACKGROUND

The Instantaneous Wave-Free Ratio (iFR) is an invasive functional evaluation method that does not require vasoactive drugs to induce maximum hyperemia.

OBJECTIVE

To evaluate the contribution of the iFR to the therapeutic decision-making of coronary lesions in the absence of non-invasive diagnostic methods for ischemia, or in case of discordance between these methods and coronary angiography.

METHOD

We studied patients older than 18 years, of both sexes, consecutively referred for percutaneous treatment between May 2014 and March 2018. Coronary stenotic lesions were classified by visual estimation of the stenosis diameter into moderate (41-70% stenosis) or severe (71%-90%). An iFR ≤ 0.89 was considered positive for ischemia. Logistic regression was performed using the elastic net, with placement of stents as outcome variable, and age, sex, arterial hypertension, diabetes, dyslipidemia, smoking, family history, obesity and acute myocardial infarction (AMI) as independent variables. Classification trees, ROC curves, and Box Plot graphs were constructed using the R software. A p-value < 0.05 was considered statistically significant.

RESULTS

Fifty-two patients with 96 stenotic lesions (56 moderate, 40 severe) were evaluated. The iFR cut-off point of 0.87 showed a sensitivity of 0.57 and 1-specificity of 0.88, demonstrating high accuracy in reclassifying the lesions. Diabetes mellitus, dyslipidemia, and presence of moderate lesions with an iFR < 0.87 were predictors of stent implantation. Stents were used in 32% of lesions in patients with stable coronary artery disease and AMI with or without ST elevation (non-culprit lesions).

CONCLUSION

The iFR has an additional value to the therapeutic decision making in moderate and severe coronary stenotic lesions, by contributing to the reclassification of lesions and decreasing the need for stenting.