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CTO Revascularisation Does Not Improve Diastolic Coupling After STEMI
Among STEMI patients with a concurrent chronic total occlusion, percutaneous coronary intervention of the occluded vessel had no effect on the left atrioventricular coupling index at four months or on its trajectory over time. However, an elevated baseline coupling index independently predicted more than twice the long-term all-cause mortality risk, reinforcing its prognostic value early after myocardial infarction (HR 2.37, 95% CI 1.27–4.45).
What Was Studied
This study examined whether opening a chronically occluded coronary artery via PCI improves diastolic atrioventricular coupling in STEMI patients who also have a concurrent chronic total occlusion (CTO). The left atrioventricular coupling index (LACI)—a ratio of left atrial to left ventricular end-diastolic volumes derived from cardiovascular magnetic resonance imaging—has recently emerged as a sensitive marker of diastolic dysfunction and post-infarction prognosis, making it a clinically relevant endpoint beyond conventional systolic measures.
How It Was Studied
This was a cardiovascular magnetic resonance substudy embedded within the multicentre, randomised controlled EXPLORE trial, which was designed to evaluate the benefit of CTO PCI following primary PCI for STEMI. A total of 200 patients (mean age 60 ± 10 years, 88% male) underwent baseline CMR imaging, with 178 patients providing analysable four-month follow-up scans. Patients were randomised to either CTO PCI or a no-CTO PCI strategy, and LACI was calculated at both time points as the primary outcome measure. Long-term all-cause mortality was also analysed in relation to baseline LACI using multivariable-adjusted survival modelling.
What Was Observed
- LACI improved significantly across the entire cohort over four months, with a median reduction of 1.0 percentage points (Q1–Q3: −4.6 to 2.0, P = 0.005), indicating genuine improvement in diastolic atrioventricular coupling following STEMI regardless of revascularisation strategy.
- CTO PCI did not drive this improvement. There was no statistically meaningful difference in LACI change between the CTO PCI and no-CTO PCI groups (−0.8% in the CTO PCI group, P = 0.122), and the treatment-by-time interaction was also non-significant (P = 0.706), confirming the recovery was independent of whether the CTO was opened.
- A baseline LACI at or above 20.6% was associated with roughly 2.4 times the risk of long-term all-cause death compared with values below this threshold, after adjusting for other prognostic variables (HR 2.37, 95% CI 1.27–4.45, P = 0.007). This identifies elevated LACI as an independent mortality predictor in the early post-STEMI period.
Why This Matters
Prior analyses of the EXPLORE trial already established that CTO PCI did not improve left ventricular systolic function, and this substudy extends that null finding to diastolic atrioventricular coupling, a mechanistically distinct and increasingly recognised cardiac parameter. Together, these results challenge the hypothesis that CTO revascularisation in STEMI confers functional benefit beyond the culprit vessel. Importantly, the study simultaneously validates LACI as a prognostically meaningful, CMR-derivable index in this population, which may support its incorporation into post-STEMI risk stratification frameworks.
How to Read This Result
While the randomised design and CMR methodology are strengths, the findings are drawn from a single substudy population that is predominantly male and middle-aged, which may limit generalisability, and the sample size—though adequate for the primary endpoint—may have been underpowered to detect modest treatment effects within subgroups.
Limitations
The abstract does not explicitly report study limitations.