Cardiogenic shock (CS) is a life-threatening condition resulting from inadequate tissue perfusion due to reduced cardiac output. Despite advancements in cardiovascular care, its short-term mortality rate remains high, around 40-50%. CS can arise from diverse causes, including acute myocardial infarction (AMI), heart failure, post-surgical complications, and non-myocardial conditions such as arrhythmias and valvular diseases. It is often classified based on severity, with staging systems such as the Shock Academic Research Consortium (SHARC) and the Society for Cardiovascular Angiography and Interventions (SCAI) helping to standardise its diagnosis and severity classification. The SCAI system includes stages from "at risk" to "extremis" based on haemodynamic status, hypoperfusion, and use of circulatory support devices. This classification system helps predict outcomes and guide management.
Pathophysiologically, CS involves impaired stroke volume and reduced cardiac output, leading to tissue hypoperfusion. Compensatory mechanisms like vasoconstriction and fluid retention can worsen the condition, causing organ congestion and dysfunction. A critical aspect of CS is biventricular failure, which is common, particularly in AMI-related CS. Right ventricular dysfunction can also lead to impaired left ventricular filling, exacerbating shock.
Management of CS includes pharmacotherapy, such as inotropic and vasopressor agents, and advanced interventions like mechanical circulatory support (MCS). Early revascularisation is critical in AMI-related CS, and coronary interventions have been shown to improve survival. However, challenges remain in selecting the appropriate pharmacologic treatment, as many studies show limited efficacy. For example, while norepinephrine is commonly used as a vasopressor, its benefits over other agents like dopamine or levosimendan remain debated. New pharmacological approaches, such as adrenomedullin and ketone esters, are being explored.
Prognosis in CS is determined by factors such as age, blood pressure, organ function, and the need for vasoactive drugs. Prediction models, like the CardShock score, attempt to quantify risk but face limitations in clinical application. Standardising care through multidisciplinary teams and regionalised systems of care is essential for improving outcomes, but more studies are needed to refine protocols and therapies, particularly for non-AMI-related causes of CS.
The treatment of CS faces significant challenges, especially in advanced stages, where pharmacotherapy and addressing the underlying cause may not stabilise the patient. Over the years, temporary MCS devices have been developed, but clinical trial evidence supporting their use is limited. For example, the intra-aortic balloon pump (IABP) shows minimal benefit in improving survival or outcomes in patients with infarct-related CS, leading to a reduced recommendation for routine use.
Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is a more potent MCS device, though data on its survival benefits in AMI-related CS are inconclusive. While it may be beneficial as a bridge to recovery or other treatments in specific conditions (like fulminant myocarditis or massive pulmonary embolism), its complications, including bleeding and ischaemia, remain a concern. Research is ongoing into combining VA-ECMO with other devices (e.g., Impella) to improve outcomes.
The Impella device has shown some promise in certain patients with ST-elevation myocardial infarction-related CS, although it carries risks like bleeding and limb ischaemia. Despite these complications, evidence of mortality benefit is still unclear. Future trials should address the variability in CS causes, patient characteristics, and timing of MCS initiation.
ECPR (extracorporeal cardiopulmonary resuscitation), which uses VA-ECMO during refractory cardiac arrest, can improve outcomes in out-of-hospital cardiac arrest but lacks conclusive survival benefits in in-hospital settings.
The management of organ dysfunction (e.g., respiratory, renal, and hepatic failure) is critical in CS patients. Ventilation strategies, fluid management, and renal replacement therapy are key considerations, though evidence for optimal approaches remains insufficient.
The long-term outcomes for CS survivors are concerning, with many facing physical and mental health sequelae, requiring ongoing care. The economic burden of CS treatment is high, and cost-effective strategies for managing the condition need further investigation.
Ultimately, the future of CS treatment lies in more personalised approaches, combining evidence-based therapies with innovations in mechanical support and management protocols. There is a need for a better understanding of complications, risk factors, and the best timing for interventions.
Source: The Lancet
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