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.
Echocardiography may be helpful in the diagnosis the cause of lethal arrhythmia and sudden cardiac arrest by assessment of the following:
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
Sudden cardiac death echocardiography and ultrasound
Sudden cardiac death other diagnostic studies
Sudden cardiac death electrocardiogram
Carcinoid syndrome echocardiography or ultrasound
Stress cardiomyopathy echocardiography or ultrasound
Hypertrophic cardiomyopathy electrocardiogram
Chronic stable angina electrocardiography
Atrial fibrillation echocardiography or ultrasound