Practice Essentials
Sudden cardiac death (SCD) is an unexpected death due to cardiac causes that occurs in a short time period (generally within 1 hour of symptom onset) in a person with known or unknown cardiac disease. It is estimated that more than 7 million lives per year are lost to SCD worldwide, including over 300,000 in the United States. See the image below.
Signs and symptoms
Patients at risk for SCD may have prodromes of chest pain, fatigue, palpitations, and other nonspecific complaints. Factors relating to the development of coronary artery disease (CAD) and, subsequently, myocardial infarction (MI) and ischemic cardiomyopathy include the following:
Family history of premature coronary artery disease
Smoking
Dyslipidemia
Hypertension
Diabetes
Obesity
Sedentary lifestyle
Specific factors relating to cardiovascular disease are listed below.
Coronary artery disease
Previous cardiac arrest
Syncope
Prior myocardial infarction, especially within 6 months
Ejection fraction of less than 30-35%
History of frequent ventricular ectopy: More than 10 premature ventricular contractions (PVCs) per hour or nonsustained ventricular tachycardia (VT)
Dilated cardiomyopathy
Previous cardiac arrest
Syncope
Ejection fraction of less than 30-35%
Use of inotropic medications
Ventricular arrhythmias
Hypertrophic cardiomyopathy
Previous cardiac arrest
Syncope
Family history of SCD
Symptoms of heart failure
Drop in systolic blood pressure (SBP) or ventricular ectopy upon stress testing
Palpitations
Presence of ventricular arrhythmias
Considerable structural abnormality, usually defined as >3 cm left ventricular septal thickness
Presence of myocardial fibrosis detected by late-gadolinium enhancement in cardiac MRI
Most persons are asymptomatic
Valvular disease
Valve replacement within past 6 months
Syncope
History of frequent ventricular ectopy
Symptoms associated with severe, uncorrected aortic stenosis or mitral stenosis
Presence of bradycardia
Long QT syndrome
Family history of long QT and SCD
Medications that prolong the QT interval
Bilateral deafness
Excess QT length; usually QTc > 500 ms
See Presentation for more detail.
Diagnosis
Laboratory studies
Cardiac enzymes (creatine kinase, myoglobin, troponin)
Electrolytes, calcium, and magnesium
Quantitative drug levels (quinidine, procainamide, tricyclic antidepressants, digoxin): High or low drug levels may have a proarrhythmic effect
Toxicology screen: For drugs, such as cocaine, that cause vasospasm-induced ischemia
Thyroid-stimulating hormone
Brain natriuretic peptide (BNP)
Other tests to evaluate or predict risk of SCD in certain cases
Imaging studies: Chest radiography, echocardiography, nuclear scintigraphy, and/or cardiac MRI to detect the presence and extend of cardiac structual abnormality
Electrocardiography (ECG): Including, possibly, signal-averaged ECG to detect certain ECG signs of syndromes associated with SCD and to detect arrhythmia
Coronary angiography: To detect significant coronary artery disease
Electrophysiology study: To assess the electrical properties of the heart and the inducibility of ventricular arrhythmias; also to detect scar and fibrosis by obtaining voltage map of the heart
See Workup for more detail.
Management
In general, advanced cardiac life support (ACLS) guidelines should be followed in all cases of sudden cardiac arrest (SCA).
Bystander cardiopulmonary resuscitation (CPR)
Immediate chest compression and defibrillation are reportedly the most important interventions to improve the outcome in SCA. Research indicates that bystander use of automated external defibrillators for shockable rhythm increases neurologically intact survival to discharge (14.3% without bystander defibrillation; 49.6% with defibrillation).
Pharmacologic therapy
Medications used in SCD include the following:
Ventricular arrhythmia: Epinephrine or vasopressin; amiodarone and lidocaine can be used as antiarrhythmic drugs if defibrillation does not control the arrhythmia. In certain cases, such as those with early repolarization syndrome or those with Brugada syndrome; VT storm should be managed by infusion of isoprotrenol. In certain cases, such as those with polymorphic VT and VF due to long QT interval, lidocaine is the preferred drug; amiodarone may prolong the QT interval and be further proarrhythmic.
Pulseless electrical activity (PEA): Epinephrine; atropine is used in certain case of bradycardia.
Asystole: One study suggested that vasopressin is more effective in acute therapy for asystole than epinephrine
. Both agents can be used.
Medical stabilization: Treat any known underlying cardiac, pulmonary, or renal problem. Empiric beta blockers are reasonable in many circumstances if the patient’s hemodynamic parameters are relatively stable.
Therapeutic hypothermia
This intervention limits neurologic injury associated with brain ischemia during a cardiac arrest and reperfusion injury associated with resuscitation.
Surgery
Temporary cardiac pacing in the case of bradycardia and bradycardia-induced VT/VF
Radiofrequency ablation in the case of VT storm and repeated shocks despite all medical treatments. The patient should be otherwise stable enough to tolerate the procedure.
Cardioverter defibrillator therapy: ICD is a very effective therapy; however, it is contraindicated in the case of VT storm. It is used more for longer term protection of the patient against future possible events. External defibrillation is the first-line therapy for witnessed or in-house VT/VF.
Coronary artery bypass grafting (CABG) in the case when the cause of SCD is thought to be multivessel coronary artery disease not suitable for percutaneous intervention.
Excision of ventricular tachycardia foci: Rarely used these days.
Excision of left ventricular aneurysms: Occasionally used when there is LV aneurysm with substrate for causing VT/VF that is not treatable with catheter ablation.
Aortic valve replacement in cases of sudden cardiac arrest (SCA) and severe aortic stenosis.
Ventricular assisted devices and orthotopic heart transplantation: These are usually the last measures when SCD and VT/VF fail to respond to any therapy. Not all patients are suitable for these therapies, and there are limited centers performing these procedures.
See Treatment for more detail.