Sudden cardiac death overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sara Zand, M.D.[2]

Overview

Sudden cardiac death is a natural, rapid, unexpected death secondary to cardiac cause or mechanism. Sudden cardiac arrest is defined as the unexpected cessation of pumping blood into vital organs due to electrical disturbance in the pathway of SA node, AV node, His Purkinje fibers or pumping failure due to conditions such as cardiogenic shock, massive pulmonary thromboembolism,fulminant myocarditis, ruptured left ventricular free wall. Without any intervention for immediate restoration of the circulation, biologic death or sudden cardiac death will happen minutes to weeks after cardiac arrest. Sudden cardiac death is responsible for 50% of cardiac death annually in the united state. In-hospital cardiac arrest happens in 290,000 adults annually in the united states. The most common cause of sudden cardiac death is coronary artery disease and atherosclerosis process. The presence of underlying disorders such as malignancy or liver disease at the time of cardiac arrest makes the condition worst. Patients with acute myocardial infarction and in-hospital cardiac arrest with shockable rhythm have a better prognosis. Post cardiopulmonary resuscitation state management should be focused on neurologic complications, hemodynamic stability, and respiratory support.

Historical perspective

There is no historical perspective available about sudden cardiac death.

Classification

There are some definitions related to cardiac arrest including Sudden cardiac death which is defined as sudden and unexpected death within one hour of being symptomatic such as palpitation, chest pain, shrtness of breath or within 24 hours in an asymptomatic patient due to arrhythmia or hemodynamic instability.Sudden cardiac arrest is suddenly cessation of cardiac activity,unresponsive patient with gasping respiration or no respiratory movement and unpalpable pulses due to cardiac etiology such as arrhythmia, pump failure. Aborted cardiac arrest is explained as unexpected circulatory collapse within one hour of being symptomatic, which is reversible after successful cardiopulmonary resuscitation. SIDS (sudden infant death syndrome) is sudden death when there is normal structural heart without any specific findings in autopsy or toxicology.

Pathophysiology

The pathogenesis of cardiac arrest is characterized by the myocardial inflammatory process in the setting of atherosclerosis, structural heart disease, genetic disorders, and environmental factors. The SCN5A, KCNH2, KCNQ1, RYR2, MYBPC3, PKP2, DSP genes mutation are associated with the development of inherited causes of cardiac arrest and sudden cardiac death.

Causes

Sudden cardiac arrest may be caused by coronary artery abnormality such as coronary atherosclerosis, acute MI, coronary artery embolism, coronary arteritis , hypertrophy of myocardium such as HCM, hypertensive heart disease, primary or secondary pulmonary hypertension , myocardial disease such as ischemic cardiomyopathy, non-ischemic cardiomyopathy, myocarditis ,valvular heart disease such as aortic stenosis, aortic insufficiency, mitral valve prolapse, endocarditis , congenital heart disease such as congenital septal defect with eisenmenger physiology , abnormality in conducting system such as Wolf-Parkinson-White syndrome , electrical instability such as (CPVT, LQTS)

Definition and Diagnosis

The diagnosis of sudden cardiac arrest is made when the following diagnostic criteria are met: the absence of a palpable pulse of the heart due to abrupt cessation of pump function , absent carotid pulse,gasping respiration or NO respiration, loss of consciousness due to cerebral hypoperfusion.Following an initial diagnosis of cardiac arrest, healthcare professionals further categorize the diagnosis based on the ECG rhythm. There are 4 rhythms that result in a cardiac arrest. Ventricular fibrillation (VF) and Pulseless Ventricular tachycardia (VT) are both responsive to a defibrillator and so are colloquially referred to as Shockable rhythms, whereas Asystole and Pulseless Electrical Activity (PEA) are non-shockable. The nature of the presenting heart rhythm suggests different causes and treatment and is used to guide the rescuer as to what treatment may be appropriate.

Epidemiology and Dermographics

The prevalence of sudden cardiac death is approximately 1.40 per 100,000 individuals in women to 6.68 per 100.000 individuals in men worldwide. In 2015, the incidence of adult in-hospital cardiac arrests was estimated to be 970 cases per 100,000 individuals in the united states. Cardiac arrest is more commonly observed within the first year of life due to sudden infant death syndrome and also between 45-75 years old due to increased risk of coronary artery disease. There is a significant decrease in sudden cardiac death at age 75 and older due to decreasing risk of coronary artery disease. Men are more commonly affected with sudden cardiac death than women in all age groups. Black individuals are more likely to develop cardiac arrest.

Risk factors

Common risk factors related to underlying coronary artery disease and inherited causes in the development of sudden cardiac arrest are hypertension, male gender ,Diabetes mellitus, hyperlipidemia, obesity, smoking, older age, obstructive sleep apnea due to hypoxia, early VF (within 48 hours of ACS increasing in-hospital mortality five times), early repolarization patten in early phase of MI, family history of sudden death.

Natural history, Complications, Prognosis

Sudden cardiac arrest occurs due to sudden disturbance in cardiac electrical propagation or failure of the heart to pumping the blood into vital organs. Early clinical features include abrupt palpitation, presyncope, syncope, chest pain, dyspnea, hypotension within one hour before terminal event. Patients may progress to develop cardiac arrest , sudden collapse, loss of effective circulation, loss of consciousness. If left untreated or failed resuscitation, biological death may occur within minutes to weeks. Common complications in survivors of cardiac arrest include pneumonia, gastrointestinal bleeding, injuries related to resuscitation, liver function test disturbance, acure renal failure, electrolytes disturbances, seizure.Two-thirds of patients with out-of-hospital cardiac arrest admitted in intensive care unit die of neurological complications.Most of the in-hospital cardiac death occur due to multiorgans dysfunction and one forth death is due to neurological complications. Factors associated poor prognosis after in-hospital cardiac arrest include age > 70 years old, concomitant underlying disorders such as pneumonia, hypotension, renal dysfunction, hepatic dysfunction,non shockable rhythm such as asystole or pulseless electrical activity. Factors associated with better prognosis after in-hospital cardiac arrest include early detection of cardiac arrest or being witnessed during arrest,shockable rhythm such as VF, VT, women between 15-45 years old. Prognosis of in-hospital cardiac arrest is generally better than out-of- hospital cardiac arrest and the 1-year survival rate of patients who survived to hospital discharge was approximately 25% in the GWTG-R registry. Survival after out-of-hospital cardiac arrest and in-hospital cardiac arrest has continued to improve over time according to the guideline.

History and symptoms

Symptoms related to arrhythmia or underlying heart disease within one hour before cardiac arrest may include , palpitation , lightheadedness , syncope , Dyspnea at rest or on exertion , orthopnea , paroxysmal nocturnal dyspnea , chest pain, edema.

Physical Examination

Patients with cardiac arrest usually appear cyanotic. Physical examination maybe remarkable for heart rate and regularity, blood pressure, Jugular venous pressure, Murmurs , Pulses, bruits , Edema , Sternotomy scars.

Laboratory Findings

An elevated concentration of brain natriuretic peptide (BNP) has been shown as the predictor of ventricular arrhythmia and sudden cardiac death

Electrocardiogram

An ECG may be helpful in the diagnosis of Sudden cardiac death. Findings on ECG associated with sudden cardiac arrest include Sinus tachycardia (39%), abnormal T-wave inversions (30%), prolonged QT interval (26%), left/right atrial abnormality (22%), left ventricular hypertrophy (17%), abnormal frontal QRS axis (17%), delayed QRS-transition zone in precordial leads (13%), pathological Q waves (13%), intraventricular conduction delays (9%), multiple premature ventricular contractions (9%), normal ECG (9%).

X-Ray

A chest x-ray may be helpful in the diagnosis of the underlying cause of cardiac arrest such as cardiomegaly, pulmonary edema, massive pericardial effusion, widening aorta silhouette.

Echocardiography

Echocardiography may be helpful in the diagnosis the cause of lethal arrhythmia and sudden cardiac arrest by assessment of ,Regional wall motion abnormality,systolic function of left ventricle, evidence of myocardial infarction, valvular heart disease such as aortic stenosis,right ventricular cardiomyopathy ,pericardial effusion, Tamponade, aorta dissection.

CT scan

Cardiac CT scan may be helpful in the diagnosis of the causes of cardiac arrest by evaluation of left ventricular volumes, Ejection fraction,Cardiac mass , anomalous origin of coronary arteries , coronary arteries calcification , pulmonary embolism ,aorta dissection.

MRI

Cardiac MRI is an accurate modality for diagnosis of structural and functional causes of cardiac arrest by the evaluation of chamber volumes, left ventricular mass , left ventricular size and function , right ventricular size and function , regional wall motion abnormality

Other Diagnostic Studies

For survivors of sudden cardiac death due to lethal arrhythmia from ischemic heart disease, coronary angiography and probable revascularization is recommended. Electrophysiology study is recommended for induction of bradyarrhythmia , ventricular tachyarrhythmia, determination the indication for ICD implantation in dilated cardiomyopathy,ARVC, HCM. Electrophysiology study is not recommended in long QT syndrome (LQTS), cathecolaminergic polymorphic ventricular tachycardia (CPVT), short QT syndrome (SQTS).

Urgent Treatment

The mainstay of therapy for patients with cardiac arrest is starting cardiopulmonary resuscitation with minimizing interruption in chest compression.The rhythm should be reassessed. If the rhythm is VF or pulseless VT, the shock should be delivered immediately. If the rhythm is asystole or pulseless electrical activity (PEA), CPR should be resumed. Advanced life support (ALS) should be kept with minimizing interruption in chest compression including: advanced airway, continuous chest compressions, capnography, IV/IO access, vasopressors, antiarrhythmics therapy, correcting reversible causes including hypoxia, hypovolemia,hypothermia, hyperkalemia, hypokalemia,acidosis, tension pneumothorax, tamponade, toxins (benzodiazepines, alcohol, opiates, tricyclics, barbiturates, betablockers, calcium channel blockers). The followings should be considered immediately in post cardiac arrest patients: 12–lead ECG ,Perfusion/reperfusion in patients with acute myocardial infarction, Oxygenation and ventilation,temperature controlling, treatment of reversible causes.Management of patients in post-cardiac arrest status include treatment of the underlying disorder, hemodynamic stability, respiratory support, controlling the neurologic complications.