Sudden Cardiac Arrest and Sudden Cardiac Death

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Chapter 19 Sudden Cardiac Arrest and Sudden Cardiac Death

Please go to expertconsult.com for supplemental chapter material.

The subject of this chapter is the ECG recognition of life-threatening arrhythmias that cause cardiac arrest. By definition, cardiac arrest occurs when the heart stops contracting effectively and ceases to pump blood. The important and closely related topic of sudden cardiac death is also introduced.

Clinical Aspects of Cardiac Arrest

The patient in cardiac arrest loses consciousness within seconds, and irreversible brain damage usually occurs within 4 minutes, sometimes sooner. Furthermore, shortly after the heart stops pumping, spontaneous breathing also ceases (cardiopulmonary arrest). In some cases, respirations stop first (primary respiratory arrest) and cardiac activity stops shortly thereafter.

Key Point

The absence of pulses in an unresponsive individual is the major diagnostic sign of cardiac arrest.

No heart tones are audible with a stethoscope placed on the chest, and the blood pressure is unobtainable. The patient in cardiac arrest becomes cyanotic (bluish gray) from lack of circulating oxygenated blood, and the arms and legs become cool. If the brain becomes severely hypoxic, the pupils are fixed and dilated. Seizure activity may occur.

When cardiac arrest is recognized, cardiopulmonary resuscitation (CPR) efforts must be started without delay. The latest (2010) recommendations for the general public in the initial basic life support treatment of a witnessed cardiac arrest involve an approach of effective, continuous chest compressions without interruption for mouth-to-mouth resuscitation (so-called hands-only resuscitation). These new recommendations (Box 19-1) are designed to improve the practice of resuscitation in untrained bystanders; they apply to adults, children, and infants but exclude newborns.

BOX 19-1 Cardiopulmonary Resuscitation (CPR) Guidelines

Untrained Bystanders

1. Call 911.

2. Begin manual chest compressions at the sternum, at 100 compressions per minute and at a depth of approximately 2 inches.

3. Continue compressions-only CPR until trained professionals arrive, or the victim becomes responsive.

Bystanders Trained in CPR

1. Call 911.

2. Deliver 30 forceful, manual chest compressions of the sternum, at a rate of 100 compressions per minute and at a depth of approximately 2 inches.

3. Open the airway with a head tilt and chin lift.

4. Perform CPR with a 30:2 sternal compression to breath ratio.

5. Continue until paramedics arrive or the victim becomes responsive.

The guidelines do recognize that, in some circumstances, conventional CPR (with a 30:2 compression-to-breath ratio) may provide more benefit than hands-only CPR. Some examples of these circumstances include the following:

• Unresponsive infants and young children

• Adult victims who are found already unconscious and not breathing normally

• Victims of drowning or collapse due to breathing problems

The specific details of CPR and advanced cardiac life support including intubation, drug dosages, the use of automatic emergency defibrillators (AEDs) and standard defibrillators, along with other matters related to definitive diagnosis and treatment, lie outside the scope of this book but are discussed in selected references cited in the Bibliography. This chapter concentrates on the particular ECG patterns seen during cardiac arrest and the clinical implications of these major abnormalities.

Basic ECG Patterns in Cardiac Arrest

The three basic ECG patterns seen with cardiac arrest were mentioned in earlier chapters. Cardiac arrest may be associated with the ECG patterns listed in Box 19-2.

BOX 19-2 Three Basic ECG Patterns with Cardiac Arrest

• Ventricular tachyarrhythmia, including ventricular fibrillation (VF) or a sustained type of pulseless ventricular tachycardia (VT)

• Ventricular asystole or a brady-asystolic rhythm with an extremely slow rate

• Pulseless electrical activity (PEA), also referred to as electromechanical dissociation (EMD)

The ECG patterns seen in cardiac arrest are briefly reviewed in the following sections, with emphasis placed on their clinical implications (Figs. 19-1 to 19-6).

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Figure 19-1 Ventricular fibrillation causing cardiac arrest.

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Figure 19-2 Ventricular tachycardia (VT) and ventricular fibrillation (VF) recorded during cardiac arrest. The rapid sine wave type of ventricular tachycardia seen here is sometimes referred to as ventricular flutter.

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Figure 19-3 Complete ventricular standstill (asystole) producing a straight-line pattern during cardiac arrest.

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Figure 19-4 Escape rhythms with underlying ventricular standstill. A, Junctional escape rhythm with narrow QRS complexes. B, Idioventricular escape rhythm with wide QRS complexes. Treatment should include the use of intravenous atropine and, if needed, sympathomimetic drugs in an attempt to speed up these bradycardias, which cannot support the circulation. If hyperkalemia is present, it should be treated.

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Figure 19-5 External cardiac compression artifact. External cardiac compression during resuscitation produces artifactual ECG complexes (C), which may be mistaken for QRS complexes.

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Figure 19-6 ECG “history” of cardiac arrest and successful resuscitation. The left panel shows the ECG sequence during an actual cardiac arrest. The right panel shows sequential therapy used in this case for the different ECG patterns. A and B, Initially the ECG showed ventricular asystole with a straight-line pattern, which was treated by external cardiac compression, along with intravenous medications. Intravenous vasopressin may also be used here. C and D, Next ventricular fibrillation was seen. Intravenous amiodarone and other medications may also be used in this setting (see text and Bibliography). E to G, Sinus rhythm appeared after defibrillation with a direct current electric shock. C, external cardiac compression artifact; R, R wave from the spontaneous QRS complex; DC, direct current; V, ventricular premature beat.

Ventricular Tachyarrhythmia (Ventricular Fibrillation or Pulseless VT)

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