Sudden Cardiac Death (SCD)

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Unexpected death within 1 hour of onset of symptoms; if a patient is successfully resuscitated, it is called a sudden death episode

• Primary electrical mechanisms include:

  • – Ventricular fibrillation (VF)

  • – Ventricular tachycardia (VT)

  • – Asystole

  • – Pulseless electrical activity

• May also be due to massive pulmonary embolism, rupture of an aortic aneurysm, or massive stroke

GENERAL CONSIDERATIONS

• Each year, 300,000 individuals in the United States die suddenly from cardiovascular disease

• Associated diseases include:

  • – Coronary artery disease

  • – Dilated cardiomyopathy

  • – Hypertrophic cardiomyopathy

  • – Arrhythmogenic right ventricular dysplasia

  • – Primary electrophysiologic disorders such as long QT syndrome, Brugada’s syndrome, and idiopathic ventricular arrhythmia

• Patients with ischemic heart disease are the largest single group at risk for sudden death

• Myocardial infarction (MI)–related scar is the substrate, and the triggering event may be ischemia, electrolyte imbalance, autonomic dysfunction, or drug toxicity

• Ejection fraction (EF) is an important predictor of survival in those who survive an episode of sudden death

  • – EF is also an important tool in assessing the risk for sudden death

  • – The lower the EF (< 0.35), the higher the risk and maximal benefit from primary prevention therapy (implantable cardioverter-defibrillator [ICD])

• Sudden cardiac death is rare among patients with structurally normal hearts

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Cardiac arrest

• Patients may arrive at the hospital after successful resuscitation

PHYSICAL EXAM FINDINGS

• Assess hemodynamic stability

• Many patients are on ventilatory support

• Shock, cold clammy extremities, and pulmonary edema are not uncommon

• Features of neurologic insult may be primary or secondary to prolonged resuscitation and anoxic encephalopathy

• Aortic regurgitation murmur secondary to dissection of the aorta

• Gray Turner’s or Cullen’s sign secondary to intraperitoneal hemorrhage secondary to rupture of aortic aneurysm

DIFFERENTIAL DIAGNOSIS

• Syncope

• In young patients, consider coronary artery anomalies, with intermittent ischemia giving rise to ventricular arrhythmia

• Drug-induced torsades de pointes

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• CBC, comprehensive metabolic panel including thyroid-stimulating hormone

• Cardiac biomarkers

• Arterial blood gas analysis

ELECTROCARDIOGRAPHY

• ECG to evaluate for acute MI, ischemia or arrhythmia such as VT, evidence of preexcitation, long QT syndrome, or Brugada pattern ECG

IMAGING STUDIES

• Both transthoracic and transesophageal echocardiogram:

  • – To evaluate left ventricular function

  • – To assess the aorta for dissection, valvular function, right ventricular dilatation (suggests pulmonary embolism), and hemodynamic status

• Spiral CT of the chest

• CT of the head

DIAGNOSTIC PROCEDURES

• Depends on the suspected cause, but electrophysiology study may be indicated

• Coronary angiography to assess for coronary artery disease and acute MI if ...