AIMI-HF trial - Ischemia and viability imaging in heart failure: The alternative imaging modalities in ischemic heart failure trial
Reported from ACC.23/WCC
Nicola Ryan provides her take on this clinical trial presented by Lisa Mielniczuk at the American College of Cardiology Scientific Session (ACC.23/WCC) – note this analysis is based upon the presented slides alone.
The AIMI-HF Trial is a prospective comparative effectiveness study assessing the effects of imaging strategies, advanced: CMR or PET versus standard: SPECT, on the composite endpoint of cardiac death MI, resuscitated cardiac arrest and cardiac re-hospitalisation in patients with heart failure due to ischaemic heart disease.
Why this study – the rationale/objective?
The role of revascularisation in patients with heart failure due to underlying ischaemic heart disease remains uncertain. To date, the evidence supporting complete revascularisation in patients with ischaemic cardiomyopathy comes from the extended follow-up of the STICH trial suggesting lower all-cause and cardiovascular mortality at 10 years in patients undergoing CABG (1). However, this population does not represent current optimal medical therapy and the advantage for surgical revascularisation only emerged at extended follow-up. A subgroup analysis of the ISCHAEMIA trial showed that in patients with heart failure and an EF 35-45% had a lower rate of the composite of CV death, MI hospitalisation for unstable angina, HF or resuscitated cardiac arrest with an invasive compared to conservative strategy (17.2% versus 29.3%; difference in 4-year event rate, −12.1% [95% CI, −22.6 to −1.6%]).
More recent data from REVIVED-BCIS2 showed that in patients prescribed optimal medical therapy with severe LV impairment due to ischaemic heart disease with demonstratable myocardial viability revascularisation with PCI did not reduce all-cause death or hospitalisation for heart failure (2). In AIMI-HF the investigators aimed to determine the impact of advanced imaging modalities, CMR or PET, compared to SPECT on the composite endpoint of cardiac death MI, resuscitated cardiac arrest and cardiac re-hospitalisation in patients who required further definition of ischaemia or viability.
How was it executed - the methodology?
Patients with known or suspected coronary artery disease documented by angiography, previous MI, moderate ischaemia or scar with NYHA Class II-IV symptoms and an EF <45% or NYHA Class I symptoms and an EF <30% were eligible for inclusion. Patients were randomised to advanced imaging strategy or standard imaging (271 patients), patients who met inclusion criteria but were not randomised due to clinical management decisions but underwent imaging were included in the registry (1,110).
- The primary outcome was time to cardiac composite event; cardiac death, MI, resuscitated cardiac arrest, cardiac hospitalisation (worsening HF, ACS, arrhythmia)
- Secondary outcomes, individual components of the primary outcome, event rates of composite and each component, all-cause death.
- Effect of imaged strategy on incidence of revascularisation and the interaction of imaging and revascularisation on the primary outcome and CV death were secondary outcomes
- Secondary outcomes included outcomes in the ischaemia and viability cohorts.
What is the main result?
Overall 1,381 patients underwent imaging in the study, 1069 in the advanced imaging group and 312 in the SPECT group. The primary clinical question was ischaemia in 672 and viability in 709 with a median follow-up of 24.1 months. Propensity score matching was used to adjust for differences in baseline characteristics study site and randomisation versus registry. The majority of patients were in NYHA Class II/III in both groups with low rates of MRA prescription and <85% prescribed ACEi/ARB.
- There was no difference in the primary composite outcome in the overall population (HR 0.95, 95%CI 0.71-1.25, p=0.696) or in the ischaemia cohort (HR 0.86 95%CI 0.61-1.21, p=0.388).
- Similarly, there was no difference in the primary composite outcome in the randomisation arm (Advanced 27.9% vs SPECT 29.6% HR 0.88, 95%CI 0.55-1.43, p=0.6615) or in cardiac death in the randomisation arm (Advanced 13.7% vs. SPECT 19.8% HR 0.63 95%CI 0.34-1.18, p=0.152).
- Patients were more likely to undergo revascularisation in the advanced imaging group (p<0.0001) and in the viability cohort (p<0.001), with 61% undergoing revascularisation via CABG.
- Early revascularisation guided by imaging strategy did not significantly reduce the incidence of the primary composite endpoint in the overall population (HR 0.71, 95%CI 0.37-1.38, p=0.317) or the ischaemia cohort (HR 0.52, 95%CI 0.23-1.15, p=0.107) though it was numerically reduced with an advanced imaging strategy in both populations.
- In the ischaemia cohort, the incidence of cardiac death was reduced in the advanced imaging group with the curves separating at 24 months (HR 0.61, 95%CI 0.38-1.0, p=0.049).
Critical reading and the relevance for clinical practice
The results of this study show that in patients with impaired LV function due to ischaemic heart disease, there were no differences in the primary composite endpoint of cardiac death, MI, resuscitated cardiac arrest, cardiac hospitalisation between the advanced imaging and the SPECT groups. The authors emphasised that in patients evaluated for ischaemia an advanced imaging strategy may be associated with a reduction in CV death however this only just reached statistical significance and the curves began to separate at 24 months. Given the overall low rates of device implantation as well as suboptimal medical therapy, it is difficult to draw definitive conclusions from this.
Overall there are a number of significant limitations to this trial, most importantly the low number of patients included in the randomised arm. The trial began recruiting in January 2011 and completed recruitment in October 2020. Over this 9-year period, only 271 patients were randomised across 15 sites. Whilst propensity matching was carried out for the registry arm patients this has inherent limitations along with the potential bias introduced by clinical decisions to opt for one imaging modality above another. The medical therapy used in this trial does not reflect current guideline-directed medical therapy with <40% of patients prescribed an MRA and no commentary with regard to the use of SGLT2 inhibitors or ARNIs. Furthermore, the overall rates of both ICD and CRT appear low given the reported mean EF. Revascularisation occurred more frequently in patients who underwent advanced imaging however the criteria used for revascularisation are not.
The question remains whether any imaging strategy has the potential to guide treatment and improve clinical outcomes in patients with LV impairment due to ischaemic cardiomyopathy. It will be of interest to read the full publication of the data however significant advances in the pharmacotherapy for LV impairment as well as potential underuse of CRTs and ICDs in this population limit its generalisability to current management of patients with ischaemic cardiomyopathy.
References
- Petrie MC, Jhund PS, She L, Adlbrecht C, Doenst T, Panza JA, et al. Ten-Year Outcomes After Coronary Artery Bypass Grafting According to Age in Patients With Heart Failure and Left Ventricular Systolic Dysfunction: An Analysis of the Extended Follow-Up of the STICH Trial (Surgical Treatment for Ischemic Heart Failure). Circulation. 2016 Nov 1;134(18):1314–24.
- Perera D, Clayton T, O’Kane PD, Greenwood JP, Weerackody R, Ryan M, et al. Percutaneous Revascularization for Ischemic Left Ventricular Dysfunction. New England Journal of Medicine. 2022 Aug 27;0(0):null.
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