Medical Care
Patients should be treated at centers where intensive cardiac monitoring and appropriate invasive and noninvasive studies can be performed. In general, a cardiovascular service, including interventional cardiology, electrophysiology, and cardiac surgery, is needed.
A cardiologist and a cardiac electrophysiologist should always participate in the care of these patients. Other consultations for expertise include an interventional cardiologist and cardiac surgeon and are made on an individual basis.
Advanced cardiac life support (ACLS)
In the event of cardiac arrest, the immediate implementation of ACLS guidelines is indicated. Widespread interest in improving rates of public ACLS training with a special emphasis on use of early defibrillation by public service personnel (eg, police, fire, airline attendants) exists. Through these measures, the greatest public health benefits can be achieved in the fight against sudden death.
In general, ACLS guidelines should be followed in all cases of sudden cardiac arrest (SCA); however, depending on the presented rhythm, issues that should be considered in acute therapy of SCA are outlined below.
Bystander CPR
The best techniques for bystander cardiopulmonary resuscitation (CPR) continue to evolve based on rigorous scientific evaluation and considerations of practical applicability. Data suggest, for example, that compression-only CPR may be of equal or greater effectiveness than traditional compression plus ventilation techniques. [26]
Early basic life support (BLS) and early defibrillation using automated external defibrillators (AEDs) remain key elements for improving survival in out-of-hospital cardiac arrest (OHCA). [27]
Adielsson et al suggest that the long-term perspective data among patients in ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) who were given bystander CPR revealed that survival to 1 month after VF almost doubled. [28]
Berdowski and colleagues in a cohort study demonstrated that the bystander use of automated external defibrillators can reduce the time to defibrillation from 11 minutes to 4.1 minutes and improves neurologically intact survival to discharge from 14.3% to 49.6%. [1] That observation is consistent with already known facts that the main initiating mechanisms of sudden cardiac death are ventricular tachycardia and ventricular fibrillation, and that time to defibrillation is a critical factor in restoring the rhythm.
The conclusion that may be drawn from the above studies is that immediate chest compression and defibrillation are the most important interventions to improve the outcome in sudden cardiac arrest, whereas ventilation does not play as important a role.
Ventricular arrhythmia (VF and VT)
Defibrillation is the mainstay of the acute therapy of SCA due to VF or VT. Epinephrine (1 mg q3-5min) or vasopressin (40 U single dose) are given. Amiodarone (300 mg IV push and 150 mg repeat IV push if needed) and lidocaine (1 mg/kg IV push q3-5min up to 3 doses) can be used as antiarrhythmic drugs if defibrillation does not control the VF/VT. In case of polymorphic VT or suspected hypomagnesemia, 1-2 g IV push of magnesium is recommended.
Pulseless electrical activity (PEA)
Epinephrine (1 mg q3-5min) can be used as there is no evidence supporting the use of vasopressin in PEA. Atropine (1 mg q3-5min) should be used in case of bradycardia. Sodium bicarbonate (1 meq/kg) should be given if there is associated hyperkalemia and its use may be considered in long arrest intervals and suspected metabolic acidosis.
Asystole
One study suggested that vasopressin is more effective in acute therapy of asystole than epinephrine. [2] Atropine and sodium bicarbonate are used with similar indications in PEA.
Medical stabilization
Careful postresuscitative care is essential to survival because studies have shown a 50% repeat inhospital arrest rate for people admitted after an SCD event. Treatment of myocardial ischemia, heart failure, and electrolyte disturbances are all justified by the results of multiple acute MI and congestive heart failure randomized trials. Empiric beta-blockers are reasonable in many circumstances because of favorable properties discussed in Causes. [29] Empiric antiarrhythmics, including amiodarone, should not supersede ICD implantation unless control of recurrent VT is needed while the patient is in the hospital.
Therapeutic hypothermia
This intervention limits neurologic injury associated with brain ischemia during a cardiac arrest and reperfusion injury associated with resuscitation. [3]
There are several plausible ways that therapeutic hypothermia may prevent neurologic injury, including reduction in metabolism and oxygen consumption of the brain, inhibition of glutamate and dopamine release, and prevention of oxidative stress and apoptosis. Therefore, therapeutic hypothermia should be considered for patients who have been successfully resuscitated from SCA and who are comatose.
In a prospective study of 1145 consecutive patients with out-of-hospital cardiac arrest who had successful resuscitation, therapeutic hypothermia was associated with increased odds of good neurological outcome (odds ratio, 1.9; 95% confidence interval, 1.18-3.06) in patients with VT or VF. [30]
Therapeutic hypothermia is more effective in patients with initial rhythm of VF/VT but is also recommended for patients presenting with asystole and PEA.
Patients who should not receive this therapy include (1) those with tympanic membrane temperature of below 30ºC at the time of presentation, (2) those who were comatose before SCA, (3) those who are pregnant, (4) those who have inherited coagulation disorders, and (5) those who are terminally ill. Two main techniques for induction of therapeutic hypothermia are surface cooling methods with the use of precooled surface cooling pads and core cooling methods with the use of cold intravenous fluids.
Primary prevention of SCD
ICD placement is routinely used for primary prevention of SCD in patients with cardiomyopathy. [31] Several studies have evaluated the use of prophylactic ICDs in patients who have not yet experienced SCD but are at high risk for future SCD. The first of these trials, Multicenter Automatic Defibrillator Implantation Trail (MADIT) demonstrated that patients with ischemic cardiomyopathy (LVEF ≤35%) and inducible but nonsuppressible VT on EPS had a survival advantage by implanting an ICD. [32]
This study was followed by MADIT-2, demonstrating that post-MI patients with an LVEF ≤30% have a survival benefit with ICD implantation. [33] The Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation (DEFINITE) study showed that implantation of an ICD reduced the risk of sudden cardiac death in a patient population of nonischemic cardiomyopathy (LVEF < 36%) who also had PVCs or nonsustained VT. [34]
Finally, the Sudden Cardiac Death in Heart Failure Trial (SCD-Heft) demonstrated that patients with either ischemic or nonischemic cardiomyopathy on optimal medical therapy, LVEF ≤35%, and NYHA II or III treated with an ICD demonstrate greater survival as compared with either amiodarone or placebo. [35]
The Home Automated Defibrillator Trial (HAT) demonstrated no survival benefit for the use of a home AED in patients surviving a recent anterior MI who were not candidates for an ICD. [36] However, the overall mortality and incidence of SCD was much lower than predicted from previous data and the noncardiac mortality was as high as cardiac mortality in the population of this study. These factors led to much less power than initially projected in this trial to detect a significant difference in the mortality rate between the arms.
The use of microvolt T wave alternans (MTWA) to determine which patients with depressed LV systolic function would best benefit from prophylactic ICD placement has been the subject of several clinical trials. To date, the results of these clinical trials has not been conclusive.
Diet
Patients with CAD are advised to follow a diet low in fat and cholesterol. Patients with severe heart failure should monitor their fluid and sodium intake.
Surgical Care
Temporary cardiac pacing
Transcutaneous or transvenous cardiac pacing may be considered in the patients with bradycardia and asystole and in patients with bradycardia-dependent ventricular tachycardia/ventricular fibrillation (VT/VF).
Radiofrequency ablation
Radiofrequency ablation may be indicated for patients with accessory pathways, bundle-branch reentry VT, idiopathic VTs such as outflow tract VTs and fascicular VTs, in scar-related VTs in ischemic and nonischemic cardiomyopathy, in more rare forms of automatic focal VTs such as papillary muscle VT, as well as in those VF cases triggered by uniform premature ventricular contractions (PVCs). Radiofrequency ablation may be useful in the treatment of patients with sudden cardiac death (SCD) who experience frequent recurrent VT/VF after implantable cardioverter defibrillator (ICD) placement, especially those who require frequent defibrillation. In addition, there is a role for VT/VF ablation prior to ICD implantation when there is VT storm despite adequate medical therapy and intervention to correct the underlying cause. In this setting, the patient should be stable enough to tolerate the procedure.
Cardioverter defibrillator therapy
ICD is the standard procedure in patients with sudden cardiac arrest (SCA) probably due to VT/VF for secondary prevention of SCD. Several multicenter trials have shown its efficacy in prevention of SCD) it is included in all related societies guidelines and recommendations. ICD can also be used for primary prevention of SCD in patients who are at risk of SCD; a subject that is still under investigation and precise recommendation depends on the details of the patients' conditions. ICD, however, is contraindicated at the time of VT storm or in patients with expected survival of less than 1 year.
External defibrillation is the single most important treatment in cases of witness and detected VT/VF, whether in the in-hospital or out-of-hospital setting.
Cardiac surgery
Cardiac surgery can be an option in the treatment for SCD via a variety of strategies.
Surgical treatment in patients with ventricular arrhythmias and ischemic heart disease includes coronary artery bypass grafting (CABG). The CASS study illustrated that patients with significant coronary artery disease (CAD) and operable vessels who underwent CABG had a decrease in the incidence of sudden death when compared to patients on conventional medical treatment. The reduction was most evident in patients who had 3-vessel disease and congestive heart failure (CHF).
Surgical treatment of ventricular arrhythmias in patients with nonischemic heart disease includes excision of VT foci after endocardial mapping and excision of left ventricular (LV) aneurysms. This is performed with decreasing frequency, because of perioperative mortality and the alternative, transvenous ICD implantation. Surgical pericardial window is sometimes used for epicardial access for ablations of those VTs with epicardial origin.
Aortic valve replacement is associated with improved outcome in patients with hemodynamically significant valvular stenosis and well-preserved ventricular function. In patients with MVP associated with significant valvular regurgitation and LV dysfunction, malignant tachyarrhythmias and SCD have been reported. These patients are candidates for mitral valve repair or replacement.
Ventricular assisted devices and orthotopic heart transplantation are indicated in certain cases of SCD/VT/VF and refractory heart failure in which significant improvement in actuarial survival is expected. Given a limited donor service, this form of treatment is expected to be beneficial for very few people who survive SCD.
Patients with long QT syndrome who do not respond to beta-blockers are candidates for ICD implantation or high thoracic left sympathectomy.
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Sudden Cardiac Death. Interplay of various risk factors that can lead to sudden cardiac death.
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Sudden Cardiac Death. Plots of mortality rates (deaths per 1000 persons) for ischemic heart disease occurring out of the hospital or in the emergency department (top) and occurring in the hospital (bottom) by age, sex, and race in 40 states during 1985.
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Sudden Cardiac Death. Figure a: Neurologic outcome stratified by initial cardiac arrest score. Neurologic recovery is defined as discharged to home and able to care for self. Figure b: Overall survival stratified by initial cardiac arrest score.
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Sudden Cardiac Death. Epsilon wave in a patient with arrhythmogenic right ventricular dysplasia.
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Sudden Cardiac Death. Ventricular fibrillation appeared during rapid atrial fibrillation in a patient with Wolff-Parkinson-White syndrome.
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Sudden Cardiac Death. Complex arrhythmias such as ventricular tachycardia/ventricular fibrillation (VT/V)F are the result of an imbalance between important components that control the rhythm. Reprinted with permission from Nova Science Publishers, Inc (Dudley SC, Kocheril AG, Sovari AA, Eds. Ventricular Arrhythmia: From Principles to Patients, Part of the Cardiology Research and Clinical Developments Series. Nova Science Publishers. New York, 2013).
