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Sudden Cardiac Arrest Due to Ischemic Causes

Article written and reviewed by Dr Luca Moretti

Sudden cardiac arrest (SCA) is a dramatic event characterized by the abrupt cessation of mechanical cardiac activity, resulting in lack of perfusion to vital organs. When cardiac arrest is caused by an acute ischemic event, it is referred to as sudden cardiac arrest due to ischemic causes, which represents the most common cause of sudden cardiac death.

Most cases are due to ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), occurring in the context of an acute coronary syndrome (ACS) or advanced chronic ischemic heart disease.

Pathophysiology

In patients with ischemic heart disease, acute myocardial ischemia can trigger electrical and structural alterations that facilitate the onset of malignant ventricular arrhythmias:

• Myocardial ischemia and hypoxia: alterations in depolarization and repolarization.
• Increased sympathetic activity: facilitation of arrhythmic triggers.
• Electrical reentry phenomena: substrate for ventricular fibrillation.
• Disturbed ionic metabolism: potassium and calcium imbalances that increase electrical instability.

If the cardiac rhythm is not promptly restored with defibrillation, cardiac arrest rapidly evolves into asystole, resulting in the patient's death.

Ischemic Causes of Cardiac Arrest

The main ischemic causes of sudden cardiac arrest include:

• Acute myocardial infarction (STEMI and NSTEMI) with critical myocardial ischemia.
• Wellens' syndrome: severe ischemia with high risk of VF.
• Chronic ischemic heart disease: ventricular remodeling with risk of fatal arrhythmias.
• Coronary microvascular dysfunction: ischemia without epicardial obstruction (INOCA).
• Coronary spasm (vasospastic angina) with transient occlusion.

Clinical Presentation

Ischemic sudden cardiac arrest is typically preceded by prodromal symptoms, but can occur unpredictably. The warning signs include:

• Sudden chest pain, often oppressive and retrosternal.
• Dyspnea, more frequent in patients with left ventricular dysfunction.
• Palpitations and sensation of impending syncope.
• Sudden loss of consciousness, followed by absence of carotid pulse and breathing.

If not treated immediately, the patient progresses to sudden cardiac death.

Diagnosis

Ischemic cardiac arrest is a clinical diagnosis based on:

1. ECG monitoring

   Shows ventricular fibrillation, pulseless ventricular tachycardia or, in advanced cases, asystole.

2. Cardiac biomarkers

   High-sensitivity troponins confirm myocardial necrosis in case of infarction.

3. Emergency coronary angiography

   Essential in survivors of cardiac arrest to identify and treat critical coronary occlusions.

Treatment

Treatment of ischemic cardiac arrest follows the ALS (Advanced Life Support) protocol:

1. Early defibrillation

Immediate defibrillation is the only effective treatment for ventricular fibrillation and pulseless ventricular tachycardia.

2. High-quality CPR

Cardiopulmonary resuscitation (CPR) with effective chest compressions and adequate ventilation improves survival.

3. Post-arrest therapy

After restoration of circulation, it is essential to:

• Hemodynamic stabilization: fluid therapy and inotropic support.
• Immediate coronary angiography: for revascularization in patients with suspected infarction.
• Temperature management: therapeutic hypothermia in comatose patients.

Prevention

Prevention of ischemic cardiac arrest is based on:

• Control of cardiovascular risk factors: hypertension, diabetes, smoking, and dyslipidemia.
• Myocardial revascularization: angioplasty or bypass in high-risk patients.
• ICD implantation: in patients with advanced ischemic heart disease.

Prognosis

Prognosis depends on the rapidity of intervention:

• Defibrillation within 3-5 minutes: survival up to 70%.
• Absence of CPR for more than 10 minutes: survival < 10%.

Timely treatment and secondary prevention are essential to reduce mortality.

References
1. Boriani G, Mei DA, Vitolo M, Imberti JF. 2022 European Guidelines on Ventricular Arrhythmias and Sudden Cardiac Death: a major boost for a multidisciplinary commitment in diagnostic and therapeutic management for accurate personalization of clinical approach. G Ital Cardiol. 2022;23(12):901-906.
2. Zeppenfeld K, et al. 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. G Ital Cardiol. 2023;24(3 Suppl. 1):e1-e132.
3. Priori SG, et al. 2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Eur Heart J. 2015;36(41):2793-2867.
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