DESCRIPTION 
- Sudden death is defined as the natural, sudden, unexpected loss of consciousness and death of a person in previously stable condition. It is usually assumed to be a consequence of a ventricular arrhythmia, but other causes may include bradycardia, pulmonary embolism, and noncardiac causes.
- Synonym(s): Cardiac arrest and sudden cardiac death; Ventricular fibrillation
Pregnancy Considerations
Pregnancy may precipitate ventricular arrhythmias in patients with long QT syndrome or structural heart disease.
EPIDEMIOLOGY
~350,000 sudden, unexpected deaths occur each year in the U.S. Persons of any age may be affected.
RISK FACTORS
- Same as in coronary artery disease (cigarette use, hyperlipidemia, and HTN)
- EKG abnormalities (typically nonspecific), often determined by ambulatory monitoring, including premature ventricular contractions and nonsustained ventricular tachycardia, LV hypertrophy, nonspecific ST-T wave changes, intraventricular conduction delays, increased QT dispersion, T-wave alternans, and decreased heart rate variability
- Decreased functional capacity
- Increased age
- Obesity
- Low LV ejection fraction
- Inducible ventricular tachycardia in high-risk patient (after MI, low LV ejection fraction)
ETIOLOGY
- Coronary artery disease, with or without prior MI is the most common cause,
- Cardiomyopathies, both hypertrophic and dilated, are associated with sudden, arrhythmic death.
- There are some clearly inherited disorders of rhythm and conduction, such as the long QT syndrome, Brugada syndrome, congenital complete heart block, myotonic dystrophy, Kearns-Sayre syndrome, and, rarely, arrhythmogenic RV dysplasia.
COMMONLY ASSOCIATED CONDITIONS
See "Risk Factors."
Outline
Signs and symptoms:
- By definition, the unexpectedness makes prodromal symptoms not a necessary component of the syndrome.
- New or worsening chest discomfort, dyspnea, palpitations, or fatigue over weeks or months may be present suggesting a change in cardiac status.
- 40–50% of all persons who die suddenly have seen a physician in the preceding month because of symptoms not necessarily recognized as being related to the heart.
DIAGNOSTIC TESTS & INTERPRETATION
- ECG (in the setting of MI)
- Cardiac enzymes [creatine kinase (CK), CK with MB fraction, troponin]
- Echo
- Coronary and LV angiography
- Cardiac MRI (may be useful in diagnosing arrhythmogenic RV dysplasia or infiltrative diseases)
- Exercise test with perfusion imaging (to assess ischemia)
- Electrophysiologic study
- Many other tests may be appropriate depending on the clinical circumstances. For example, if pulmonary embolus is suspected, ventilation-perfusion imaging, spiral CT scanning, or pulmonary angiography can be considered. If intracranial hemorrhage is suspected, cerebral MRI or CT scanning would be indicated.
Lab
- Cardiac enzymes may identify MI, they may also be elevated due to a primary arrhythmia resulting in prolonged coronary hypoperfusion and/or requiring repeated electrical defibrillation.
- MI as a cause of cardiac arrest would prompt evaluation of coronary anatomy.
Pathological Findings
- Coronary artery disease with or without prior MI is the usual substrate.
- Cardiomyopathy, either hypertrophic or dilated
- Anomalous coronary artery
- Pulmonary embolus
- Cerebral hemorrhage
DIFFERENTIAL DIAGNOSIS
- The cause of sudden, unexpected collapse and death within 1 hr of symptom onset is often elusive.
- Although such events are usually presumed to be cardiac in origin, many other catastrophic events can present with a similar time course, such as pulmonary embolism, aortic rupture, and intracerebral hemorrhage.
- Sometimes postmortem exam can define the cause of sudden death, but even then, the cause cannot always be determined.
Outline
ADDITIONAL TREATMENT
General Measures
- Prompt resuscitation
- Management of airway, circulation, and brain
SURGERY
- Surgical interventions are dictated by the cause of the cardiac arrest.
- If there is severe coronary artery disease, coronary revascularization is indicated.
- If profound bradycardia is documented, a pacemaker should be implanted.
- If ventricular fibrillation or tachycardia is documented, implantation of an implantable defibrillator should be considered.
IN-PATIENT CONSIDERATIONS
Admission Criteria
- The resuscitation rate in the field is usually <10%.
- If a survivor makes it to the hospital, admission is obviously the only option.
- Even survivors to admission have a high in-hospital mortality rate and often disability if they are discharged alive.
Outline
FOLLOW-UP RECOMMENDATIONS
Patient Monitoring
- Assess changes in functional capacity and cardiac symptoms that may be warning of changing ischemic substrate.
- If drug therapy is chosen, assess compliance, drug levels, effect on ECG, and changes in myocardial substrate.
- Device follow-up if implantable defibrillator chosen
- Control of coronary risk factors and prevention of acquired heart disease
- Correct ischemia (surgical or percutaneous revascularization,
-blockade). - Improve LV function (ACE inhibitors in coronary artery disease).
- If amiodarone is used, follow CXR, thyroid and liver function, and ECG.
- Avoid proarrhythmic drugs.
- Identification of high-risk groups by noninvasive (ECG, signal averaged ECG, heart rate variability, baroreflex depression) and invasive (electrophysiologic study) assessment
PATIENT EDUCATION
- Genetic testing and counseling, if indicated (eg, for patients with long QT syndrome or Brugada syndrome)
- Avoidance of drugs that may be proarrhythmic, such as QT-prolonging drugs in patients with long QT syndrome (www.qtdrugs.org)
- Recommendations for diet and activity are specific for the individual patient affected.
PROGNOSIS
- Outcome depends on the underlying substrate. In the absence of acute new Q wave MI, the risk for recurrent cardiac arrest if sudden death was due to ventricular fibrillation or tachycardia may be up to 30% at 1 yr.
- In the AVID trial, 1,013 patients with sudden death or hemodynamically unstable VT were randomized to either implantable cardioverter–defibrillator (ICD) or amiodarone therapy. The ICD group had a 30% relative risk reduction in total mortality.
Outline