How to identify high risk patients for sudden death on routine electrocardiogram during health checkups

Abstract

 When arrhythmias are detected during health checkups, physicians must consider 1) whether the arrhythmia should be treated or may be left untreated, and 2) whether the arrhythmia may lead to a fatal outcome in the future on the basis of the presence/absence of symptoms and the type of arrhythmia. This document describes how to assess the risk of severe and possibly fatal arrhythmias in patients found to have abnormal ECG findings such as premature ventricular complexes (PVCs) during health checkups. 
The most important factor for the risk of fatal arrhythmia is the presence or absence of structural heart disease. Physicians should be able to recognize abnormal findings on a 12-lead ECG suggestive of heart diseases such as ST-T changes associated with left ventricular hypertrophy, ischemic ST-T changes, and ECG findings of old myocardial infarction, and recommend the patients to undergo echocardiography, stress ECG, coronary CT, or other appropriate examinations. 
The Lown classification was advocated as it was useful in classifying the severity of PVCs and prescribing antiarrhythmic drugs according to the severity scale, but this is only useful for patients in the coronary care unit (CCU) or those with severe heart disease. The risk of sudden death is considered low when structural heart disease is ruled out even when the PVC is rated as severe in the Lown classification. 
There are ECG findings that indicate the risk of sudden death in patients with no arrhythmias on a 12-lead ECG. For example, the ε wave at the terminal portion of the QRS complex in V1, V2 or V3 is specific to arrhythmogenic right ventricular cardiomyopathy (ARVC). 
The document also describes “idiopathic ventricular fibrillation” (IVF) that is defined as ventricular arrhythmia in the absence of structural heart disease. Long QT syndrome, a type of IVF, is a genetic cardiac abnormality that can lead to syncope, seizure or sudden death due to polymorphic ventricular tachycardia. Brugada syndrome, another type of IVF, is a condition that is characterized with typical ST elevation patterns in V1~V3 leads and may lead to sudden death due to ventricular fibrillation, and is classified into the coved type and the saddle back type according to the ST wave form. Recent automatic ECG analyzers recognize the patterns of these waveforms and report them as “Brugada syndrome is suspected”. Physicians should interview such patients for their history of syncope and family history of sudden death to determine whether further examinations are needed or not. Early repolarization syndrome and short PR interval syndrome, which have been recently reported as new entities of IVF, are also described. 
When physicians and laboratory professionals look for slight abnormal findings in routine ECGs, appropriate measure can be taken to prevent cardiovascular events. An understanding of warning ECG abnormalities is essential.