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extensive ischaemia due to MVD, acute severe mitral regurgitation, and mechanical complications. Patients with ACS and CS should be transferred as soon as possible to a PCI centre where immediate coronary angiography, and PCI of the IRA if needed, can be performed.404,505 In patients with CS complicating ACS in whom the coronary anatomy is not suitable for PCI, emergency CABG is recommended. Management of MVD in this context is detailed in Section 10. The clinical benefit of percutaneous MCS devices and/or VA-ECMO in the context of ACS remains unclear.402,561 Micro-axial MCS devices have not been associated with lower 30-day mortality in comparison to IABP in observational studies.400 In a large retrospective registry of 48 306 patients (>80% ACS) undergoing PCI with MCS, micro-axial MCS support was associated with higher mortality and bleeding rates in comparison to IABP.562 Similar results were observed in another propensity-matched registry analysis confined to patients with CS, where micro-axial MCS support was also associated with more complications and higher mortality than IABP.563 In the IABP-SHOCK II trial, the routine use of IABP in patients with ACS and CS did not reduce 30-day, 1-year, or 6-year mortality.399,405,407 Based on these data, a benefit of LVAD in patients with ACS has not been demonstrated, and given that observational data have suggested that this may be associated with harm, caution is advised in this regard until further RCT evidence is available.

12.2.2 Mechanical complications

Mechanical complications may occur in the first days following MI, most commonly in patients presenting with STEMI. The incidence of mechanical complications has fallen significantly in the era of PPCI.564 A recent large epidemiological investigation including almost 9 million ACS patients reported an overall prevalence of mechanical complications in 0.27% of STEMI cases and 0.06% of NSTEMI cases, with in-hospital mortality rates of 42.4% and 18%, respectively.564 Mechanical complications are life-threatening and therefore require prompt identification and management (Supplementary data online, Table S14). Sudden hypotension, the recurrence of chest pain, new cardiac murmurs suggestive of acute mitral regurgitation or a ventricular septal defect, pulmonary congestion, or jugular vein distension should raise suspicion of a mechanical complication. Immediate echocardiographic assessment is indicated when mechanical complications are suspected. The use of temporary MCS for mechanical complications, either to improve pre-operative clinical/haemodynamic status or prophylactically, represents a new trend in management. However, this approach requires more data and evidence in order to determine if it provides a clinical benefit.565–568 Surgery is currently regarded as the treatment of choice for patients with ACS and mechanical complications, although percutaneous strategies are occasionally used in selected candidates with a prohibitive risk profile or contraindications to a surgical approach.569–572 A multidisciplinary approach to the management of these patients is of paramount importance, and should apply to all stages of care, from the initial stabilization of the patient to discussion and application of the therapeutic strategy, including palliative care.573,574 Patients with ACS-related mechanical complications should be considered for IABP while awaiting surgery.

12.2.3 Left ventricular thrombus

While the incidence of LV thrombus following AMI has declined due to advances in reperfusion and antithrombotic therapies, it remains relatively common, particularly following anterior STEMI, where it can be present in >9% of patients according to a large meta-analysis.575,576

Echocardiography remains the first-line imaging test for the detection of LV thrombus. In patients where the apex is not well visualized on regular echocardiography, contrast echocardiography may be considered for improved image quality. CMR is the gold standard imaging modality for the diagnosis and assessment of LV thrombi. Contemporary CMR data report LV thrombi in up to 6.3% of all STEMI patients and in 12.2% of those with anterior STEMI, suggesting that the incidence of LV thrombi may be underestimated with echocardiography.577 Patients with LV thrombi that were not evident on echocardiography but were detected by CMR appear to have similar clinical outcomes to patients with LV thrombi that were evident on echocardiography.578 Therefore, CMR should be considered in patients with equivocal echocardiographic images or in patients considered to be at a particularly high risk of LV thrombus. The timing of imaging for LV thrombus may also be relevant, given that the identification of LV thrombus has been reported to increase in the first 2 weeks post-MI.579 While more contemporary data are required, these data suggest that a high proportion of LV thrombi may develop following hospital discharge, indicating that delayed imaging at 2 weeks in high-risk patients may be of value. Once an LV thrombus has been diagnosed, OAC therapy (warfarin or NOAC) should be considered for 3–6 months, guided by repeated echocardiography or CMR and with consideration of bleeding risk and the need for concomitant antiplatelet therapy.580,581 However, there are a lack of prospective randomized data on the optimal anticoagulation regimen, anticoagulation duration, and the combination of oral anticoagulation with antiplatelet agents in patients with LV thrombus following MI.581 The choice of therapy should be tailored to the patient’s clinical status and the results of follow-up investigations.

12.2.4 Post-acute coronary syndrome pericarditis

Pericardial complications that may develop after an AMI include early infarct-associated pericarditis (occurring from a few hours to 4 days after AMI, mostly transient), late pericarditis or post-cardiac injury (Dressler) syndrome (typically occurring 1–2 weeks after AMI), and pericardial effusion.548,582 This topic is discussed further in the Supplementary data online.

12.2.5 Arrhythmias

12.2.5.1. Atrial fibrillation Atrial fibrillation is the most frequent supraventricular arrhythmia in patients with ACS.583 AF may be pre-existing, first time detected, or of new onset during ACS management. Patients with AF have a greater number of comorbidities compared with patients without AF and are at higher risk of complications.584 In most cases, AF is well tolerated and no specific treatment is required, apart from anticoagulation.585 Prompt treatment is required for AF causing acute haemodynamic instability, with electrical cardioversion being the preferred approach. Adequate rate control can be achieved by administration of betablockers depending on the presence of HF and low ejection fraction. For patients with depressed LVEF, amiodarone or digoxin could be used (preferably amiodarone). In cases of hypotension, digoxin is preferred over amiodarone or beta-blockers. Patients with AF and risk factors for thrombo-embolism should be adequately treated with chronic oral anticoagulation.585 ACS patients with documented AF of any Downloaded from academic.oup.com/eurheartj/article/44/38/3720/7243210 by guest on 07 October 2026