Primary prevention
Since coronary artery disease (CAD) is a common cause of cardiac arrest, management of CAD risk factors is important in the primary prevention of cardiac arrest. This may include treatment of hypertension, diabetes, dyslipidaemia, and general lifestyle interventions such as healthy diet and regular exercise. Natriuretic peptides may have a role in identifying people at greater risk of sudden cardiac death (SCD) in the general population or patients with CAD.[7]
Several randomised controlled trials and prospective registries have found a mortality reduction when implantable cardioverter defibrillator (ICD) therapy is used for the primary prevention of SCD in heart failure patients with a left ventricular ejection fraction (LVEF) of <35%.[7]
ICD is recommended in the following cases:
Patients with ischaemic cardiomyopathy and ejection fraction ≤30%.[44][45]
Patients with non-ischaemic cardiomyopathy, New York Heart Association class II or greater, congestive heart failure, and ejection fraction ≤35%.[29][45]
Patients with hypertrophic cardiomyopathy (HCM) and two or more of the following risk factors: syncope, left ventricular thickness >3 cm, abnormal blood pressure response to exercise (hypotension), non-sustained ventricular tachycardia (VT), and family history of sudden cardiac death. Patients with only 1 risk factor should be counselled and considered on a case-by-case basis.[30]
Patients with arrhythmogenic right ventricular dysplasia (ARVD) and extensive disease of the right ventricle, involvement of the left ventricle, history of syncope, or family history of sudden cardiac arrest.
Patients with congenital long QT syndrome (LQTS) who have a history of cardiac arrest, are symptomatic on beta-blocker therapy and genotype-specific therapies, or who are asymptomatic but have a high-risk profile (based on the 1-2-3 LQTS Risk Calculator).[7]
Patients with Brugada syndrome and a history of syncope with ST-segment elevations in leads V1 through V3 or documented VT.[40]
ICDs should only be considered in patients who are expected to survive for more than one year of good quality life.[7]
In patients with heart failure with reduced ejection fraction (<40%), guideline-directed medical therapy is recommended to reduce sudden cardiac death (and all-cause mortality).[45] This may include a beta-blocker, mineralocorticoid receptor antagonist, SGLT2 inhibitor, and renin-angiotensin system inhibitor (ACE inhibitor, angiotensin-II receptor antagonist or angiotensin-II receptor antagonist plus neprilysin inhibitor). Anti-arrhythmics have been studied for prevention of sudden cardiac death.[46] In patients at high risk for sudden cardiac death, amiodarone has been shown to reduce sudden cardiac death, cardiac mortality, and all-cause mortality when compared with placebo or no intervention.[47]
Screening for athletes shows potential to identify those at risk for cardiovascular disease before onset of symptoms. In younger athletes, a combination of medical history, physical examination and ECG appears effective in identifying cardiovascular disease by identifying relevant symptoms, such as exertional syncope, or ECG abnormalities. Older athletes can be evaluated using risk score systems, such as European Society of Cardiology SCORE2.[7]
In cases of sudden cardiac death, the underlying cause should be investigated and autopsy considered, particularly in the young (under 50 years old). Autopsy can identify conditions such as cardiomyopathy and premature coronary artery disease. When possible genetic cardiac disease is identified, first-degree relatives should be assessed in a specialised cardiology clinic and genetic testing may be considered. In autopsy-negative cases, targeted post-mortem genetic testing can identify a mutation in up to one-third of cases.[7]
Secondary prevention
Survivors of cardiac arrest should be assessed for suitability for implantable cardioverter defibrillator (ICD) placement.[7] A meta-analysis of three key early ICD trials comparing ICD to medical therapy (primarily amiodarone) for secondary prevention of sudden cardiac death demonstrated a 28% mortality reduction in the ICD group, almost entirely due to a 50% reduction of arrhythmic death.[135] Therefore, the use of an ICD for secondary prevention in patients with either ischaemic or non-ischaemic cardiomyopathy who have survived a cardiac arrest that is not due to reversible causes is widely accepted.[7][64][136] The key determinant for intervention common to all those potentially eligible for a device is a meaningful life-expectancy greater than 1 year.[64] Complications of ICD therapy include inappropriate shocks, lead fractures, and device-related infections.[7]
Patients with ICDs who have frequent arrhythmia recurrences and ICD shocks (despite optimal programming) may benefit from anti-arrhythmic medicines or catheter ablation. Anti-arrhythmic drugs may also have a role in patients who do not want or are ineligible for an ICD (e.g., due to a limited life-expectancy and/or functional status).[64]
Beyond ICDs, secondary prevention is generally condition specific, for example, performing revascularisation for patients with coronary artery disease, administering beta-blockers, avoiding QT-prolonging medicines in patients with long-QT syndrome, and abstaining from participation in competitive athletics in patients with arrhythmogenic right ventricular cardiomyopathy.[124]
In all patients diagnosed with heart disease, cardiovascular risk factors should be addressed. Smoking cessation should be emphasised and aggressive interventions including support groups and pharmacological (nicotine and non-nicotine-containing) products are recommended. Similarly, diet and lipid-lowering therapy should be pursued. Blood pressure and diabetes management should be optimised. One study found that initiation or maintenance of at least 5 days of moderate intensity activity or 3 days of vigorous-intensity activity a week is associated with reduced risk of all-cause, cardiovascular and noncardiovascular deaths in older adults with newly diagnosed cardiovascular disease.[137]
Efforts to maximise the probability of survival should a further arrest occur include educating family and carers about what a cardiac arrest may look like and when to call for help. Some hospitals offer cardiopulmonary resuscitation training to patients and their families before discharge.[124]
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