Can Functional Testing for Ischemia and Viability Guide Revascularization?

Intentional coronary revascularization versus conservative therapy in patients after peripheral artery revascularization due to critical limb ischemia: the INCORPORATE trial

OBJECTIVES

INCORPORATE trial was designed to evaluate whether default coronary-angiography (CA) and ischemia-targeted revascularization is superior compared to a conservative approach for patients with treated critical limb ischemia (CLI). Registered at clinicaltrials.gov (NCT03712644) on October 19, 2018.

BACKGROUND

Severe peripheral artery disease is associated with increased cardiovascular risk and poor outcomes.

METHODS

INCORPORATE was an open-label, prospective 1:1 randomized multicentric trial that recruited patients who had undergone successful CLI treatment. Patients were randomized to either a conservative or invasive approach regarding potential coronary artery disease (CAD). The conservative group received optimal medical therapy alone, while the invasive group had routine CA and fractional flow reserve-guided revascularization. The primary endpoint was myocardial infarction (MI) and 12-month mortality.

RESULTS

Due to COVID-19 pandemic burdens, recruitment was halted prematurely. One hundred eighty-five patients were enrolled. Baseline cardiac symptoms were scarce with 92% being asymptomatic. Eighty-nine patients were randomized to the invasive approach of whom 73 underwent CA. Thirty-four percent had functional single-vessel disease, 26% had functional multi-vessel disease, and 90% achieved complete revascularization. Conservative and invasive groups had similar incidences of death and MI at 1 year (11% vs 10%; hazard ratio 1.21 [0.49-2.98]). Major adverse cardiac and cerebrovascular events (MACCE) trended for hazard in the Conservative group (20 vs 10%; hazard ratio 1.94 [0.90-4.19]). In the per-protocol analysis, the primary endpoint remained insignificantly different (11% vs 7%; hazard ratio 2.01 [0.72-5.57]), but the conservative approach had a higher MACCE risk (20% vs 7%; hazard ratio 2.88 [1.24-6.68]).

CONCLUSION

This trial found no significant difference in the primary endpoint but observed a trend of higher MACCE in the conservative arm.

Total-Body PET/CT Applications in Cardiovascular Diseases: A Perspective Document of the SNMMI Cardiovascular Council

Digital PET/CT systems with a long axial field of view have become available and are emerging as the current state of the art. These new camera systems provide wider anatomic coverage, leading to major increases in system sensitivity. Preliminary results have demonstrated improvements in image quality and quantification, as well as substantial advantages in tracer kinetic modeling from dynamic imaging. These systems also potentially allow for low-dose examinations and major reductions in acquisition time. Thereby, they hold great promise to improve PET-based interrogation of cardiac physiology and biology. Additionally, the whole-body coverage enables simultaneous assessment of multiple organs and the large vascular structures of the body, opening new opportunities for imaging systemic mechanisms, disorders, or treatments and their interactions with the cardiovascular system as a whole. The aim of this perspective document is to debate the potential applications, challenges, opportunities, and remaining challenges of applying PET/CT with a long axial field of view to the field of cardiovascular disease.

Diagnostic Performance of PET Versus SPECT Myocardial Perfusion Imaging in Patients with Smaller Left Ventricles: A Substudy of the 18F-Flurpiridaz Phase III Clinical Trial

The performance of SPECT myocardial perfusion imaging (MPI) may deteriorate in smaller hearts, primarily because of the lower resolution of conventional Anger cameras. ¹⁸F-flurpiridaz is a novel PET MPI agent with superior image and defect resolution. We sought to determine the diagnostic performance of ^99mTc-labeled SPECT MPI compared with ¹⁸F-flurpiridaz PET MPI according to left ventricle (LV) size. Methods: We conducted a substudy of the phase III clinical trial of flurpiridaz (n = 750) and stratified diagnostic performance according to the median PET LV end-diastolic volume (LVEDV), with smaller LVs defined as having an LVEDV of less than 113 mL (n = 369) and larger LVs defined as having an LVEDV of at least 113 mL (n = 381). Images were interpreted by the majority rule of 3 independent masked readers. The reference standard was quantitative invasive angiography, with at least 50% stenosis in at least 1 coronary artery considered significant. Results: SPECT performance decreased significantly from an area under the curve (AUC) of 0.75 in larger LVs to 0.67 in smaller LVs (P = 0.03), whereas PET performance was similar in larger and smaller LVs (AUC, 0.79 vs. 0.77, P = 0.49). Accordingly, in smaller LVs, PET had a higher AUC (0.77) than the SPECT AUC (0.67) (P < 0.0001), a phenomenon driven by female patients (P < 0.0001). In smaller LVs, there was a degradation of SPECT sensitivity that was highly significant (P < 0.001), whereas there was no significant change in PET sensitivity according to LV size (P = 0.07). Overall, PET had significantly higher sensitivity than SPECT in both smaller LVs (67% vs. 43%, P < 0.001) and larger LVs (76% vs. 61%, P < 0.001). The specificities of PET and SPECT were similar in larger LVs (76% vs. 83%, P = 0.11). Although SPECT specificity improved in smaller compared with larger LVs (90% vs. 83%, P = 0.03), the PET specificity did not change with LV size (76% vs. 76%, P = 0.9). Conclusion: The diagnostic performance of ¹⁸F-flurpiridaz PET MPI is not affected by LV size and is superior to SPECT MPI in patients with smaller LVs, highlighting the importance of appropriate test selection in these patients.

Association of coronary revascularisation after physician-referred non-invasive diagnostic imaging tests with outcomes in patients with suspected coronary artery disease: a post hoc subgroup analysis

OBJECTIVE

We aimed to evaluate the association of the prognostic impact of coronary revascularisation with physician-referred non-invasive diagnostic imaging tests (single photon emission CT (SPECT) vs coronary CT angiography) for coronary artery disease.

DESIGN

A post hoc analysis of a subgroup from the patient cohort recruited for the Japanese Coronary-Angiography or Myocardial Imaging for Angina Pectoris Study.

SETTING

Multiple centres in Japan.

PARTICIPANTS

From the data of 2780 patients with stable angina, enrolled prospectively between January 2006 and March 2008 in Japan, who had undergone physician-referred non-invasive imaging tests, 1205 patients with SPECT as an initial strategy and 625 with CT as an initial strategy were analysed. We assessed the effect of revascularisation (within 90 days) in each diagnostic imaging stratum and the interaction between the two strata.

PRIMARY AND SECONDARY OUTCOME MEASURES

Major adverse cardiac events (MACEs), including death, myocardial infarction, hospitalisation for heart failure and late revascularisation, were followed up for 1 year. The χ² test, Student's t-test, Kaplan-Meier analysis, log-rank test and multivariable Cox proportional hazard model were used in data analysis.

RESULTS

A total of 210 (17.4%) patients in the SPECT stratum and 149 (23.8%) in the CT stratum underwent revascularisation. Although in each stratum, the cumulative 1 year incidence of MACEs was significantly higher in patients who underwent revascularisation than in those who did not (SPECT stratum: 9.1 vs 1.2%, log-rank p<0.0001; CT stratum: 6.1 vs 0.8%, log-rank p=0.0001), there was no interaction between the risk of revascularisation and the imaging strata (SPECT stratum: adjusted HR (95% CI), 4.25 (1.86-9.72); CT stratum: 4.13 (1.16-14.73); interaction: p=0.97).

CONCLUSION

The association of revascularisation with the outcomes of patients with suspected coronary artery disease was not different between SPECT-first and CT-first strategies in a physician-referred fashion.

Myocardial Viability and Long-Term Outcomes in Ischemic Cardiomyopathy

BACKGROUND

The role of assessment of myocardial viability in identifying patients with ischemic cardiomyopathy who might benefit from surgical revascularization remains controversial. Furthermore, although improvement in left ventricular function is one of the goals of revascularization, its relationship to subsequent outcomes is unclear.

METHODS

Among 601 patients who had coronary artery disease that was amenable to coronary-artery bypass grafting (CABG) and who had a left ventricular ejection fraction of 35% or lower, we prospectively assessed myocardial viability using single-photon-emission computed tomography, dobutamine echocardiography, or both. Patients were randomly assigned to undergo CABG and receive medical therapy or to receive medical therapy alone. Left ventricular ejection fraction was measured at baseline and after 4 months of follow-up in 318 patients. The primary end point was death from any cause. The median duration of follow-up was 10.4 years.

RESULTS

CABG plus medical therapy was associated with a lower incidence of death from any cause than medical therapy alone (182 deaths among 298 patients in the CABG group vs. 209 deaths among 303 patients in the medical-therapy group; adjusted hazard ratio, 0.73; 95% confidence interval, 0.60 to 0.90). However, no significant interaction was observed between the presence or absence of myocardial viability and the beneficial effect of CABG plus medical therapy over medical therapy alone (P = 0.34 for interaction). An increase in left ventricular ejection fraction was observed only among patients with myocardial viability, irrespective of treatment assignment. There was no association between changes in left ventricular ejection fraction and subsequent death.

CONCLUSIONS

The findings of this study do not support the concept that myocardial viability is associated with a long-term benefit of CABG in patients with ischemic cardiomyopathy. The presence of viable myocardium was associated with improvement in left ventricular systolic function, irrespective of treatment, but such improvement was not related to long-term survival. (Funded by the National Institutes of Health; STICH ClinicalTrials.gov number, NCT00023595.).

Rational and design of the INtentional COronary revascularization versus conservative therapy in patients undergOing successful peripheRAl arTEry revascularization due to critical limb ischemia trial (INCORPORATE trial)

Critical limb ischemia is associated with excessively high risk for cardiovascular events, including myocardial infarction and death. Additionally, in this patient population non-invasive evaluation of coronary artery disease is limited due to (1) inability of exercise testing, (2) frequent occurrence of balanced ischemia and (3) frequent occurrence of diffuse coronary calcification. Intentional Coronary Revascularization Versus Conservative Therapy in Patients Undergoing Peripheral Artery Revascularization Due to Critical Limb Ischemia trial (INCORPORATE trial) is a multicentric international randomized open label clinical trial. Trial will recruit patients, who underwent successful peripheral artery revascularization due to critical limb ischemia and randomize 1:1 to conservative medical therapy versus an immediate invasive strategy to investigate and treat coronary artery disease. The objective is to evaluate whether intentional invasive strategy with ischemia targeted reasonably complete coronary revascularization is superior as compared to conventional primarily conservative approach in terms of spontaneous myocardial infarction and overall survival at 12 months follow-up. The trial is registered at clinicaltrials.gov (NCT03712644).

Limited prognostic value of myocardial viability assessment in patients with coronary artery diseases and severe left ventricular dysfunction

Background

Myocardial viability assessment is typically performed in patients with coronary artery disease (CAD) and severe left ventricular (LV) dysfunction to identify those who might benefit from revascularization and assist in decision making process. However, the prognostic value of myocardial viability testing remains a debating issue.

Methods

Positron Emission Tomography using ¹⁸F-fluorodeoxyglucose (¹⁸FDG-PET) was performed in 81 patients with ischemic LV dysfunction [ejection fraction (EF) ≤35%] for myocardial viability assessment prior to coronary artery bypass surgery. Fifty-three of them received finally coronary artery bypass grafting and were divided into two groups according to the extent of myocardial scar: one group with scar burden ≥10% (n=30) and the other with scar burden <10% (n=23). The remaining patients were contraindicated for CABG and received optimal medical treatment (OMT, n=28). All patients were followed up and the primary endpoint was all-cause mortality and the secondary endpoint was a composite of all-cause mortality and major adverse cardiovascular and cerebrovascular events (MACCE).

Results

¹⁸FDG-PET revealed a different profile of myocardial viability among three groups with respect to the extent of myocardial scar, the hibernating myocardium (both P<0.01), some echocardiographic parameters such as left ventricular diastolic dimension (LVDD) and EF were also significantly different (both P<0.05). Nevertheless, the baseline prevalence of comorbidities and functional classifications were comparable. The per-procedural parameters were not significantly different between two CABG groups. In a median follow-up time of 32 months, Kaplan Meier analysis uncovered no significant difference in terms of overall survival (P=0.74) and MACCE-free survival (P=0.66) among three groups.

Conclusions

Myocardial viability assessment using ¹⁸FDG-PET is of limited prognostic value in patients with CAD and severe LV dysfunction. In patients with substantial myocardial scar burden despite the existence of considerable hibernating myocardium, functional recovery following surgical revascularization is not necessarily translated to survival benefits.