Systemic endothelin receptor blockade in ST-segment elevation acute coronary syndrome protects the microvasculature: a randomised pilot study

Aims: ST-elevation acute coronary syndrome (STE-ACS) is characterised by compromised blood flow at the epicardial and microvascular levels. Endothelin-1 (ET-1) is a mediator of microvascular dysfunction and adverse cardiac remodelling. We hypothesised that administration of an endothelin type A (ETA) receptor antagonist (BQ-123; Clinalfa, Laufelfingen, Switzerland) may protect microvascular function. Methods and results: In this proof-of-concept, randomised, double-blind, placebo-controlled trial, patients with posterior-wall STE-ACS (n=57) were randomly assigned to receive intravenous BQ-123 at 400 nmol/minute or placebo over 60 minutes, starting at the onset of primary percutaneous coronary intervention (PCI). Time to myocardial contrast wash-in of the infarcted segment assessed by first-pass perfusion cardiac magnetic resonance imaging was the primary efficacy endpoint. Secondary endpoint's included enzymatic infarct size and left ventricular ejection fraction (LVEF). In patients randomised to BQ-123 we observed shorter microvessel perfusion delays six days after PCI (1.8 sec [0.7-3.4] versus 3.3 sec [2.3-5.4] in placebo-treated patients, p=0.005). The treatment group demonstrated smaller enzymatic infarct sizes (p=0.014). All patients were alive at six months, with an LVEF of 63% (58-69) in patients randomised to BQ-123 and 59% (51-66) in placebo-treated patients (p=0.047). Conclusions: Administration of an ETA receptor blocker during primary PCI in patients with STE-ACS is safe and may improve tissue-level perfusion and LVEF.