How to screen for inherited cardiac diseases

Background

Population screening for inherited cardiac disorders is a matter of heated debate (1-2) however there are guidelines between the American Heart Association (AHA) and European Society of Cardiology (ESC) that screening of high-risk groups such as athletes should occur (3) - the ACC is keeping a more conservative view on the benefits of screening in this population. On the basis that that there is a 2.5 times increased risk of sudden death in this population compared with the general population and that 90% of causes are cardiovascular (4), the 2006 Lausanne recommendations are for pre-participation screening of athletes. This position has also been endorsed by the Olympics Committee and was made mandatory by the Union of European Football Association for those competing in European championships (5).
Italian law mandates pre-participation screening of all competitive athletes as well. The cost of the screening is supported however by the athletes themselves, who thereby receive medical clearance to practice their sport competitively .
In Veneto, (northern Italy) a screening programme for athletes 12-35 years of age has been in place for over 30 years, and sudden cardiovascular death has decreased among athletes by approximately 90% whilst remaining unchanged in the general population. This outcome is due to early recognition of athletes with cardiomyopathies and exclusion from competitive sport. All athletes were the object of 1) a careful history, 2) a physical examination and 3) an electrocardiogram. A significant reduction in deaths was noted within this programme, nevertheless, it showed a limited ability to detect premature atherosclerosis and coronary artery anomalies. 
In addition, 9% of those screened required additional testing whereas only 2% were ultimately identified as having a cardiac disorder, thus screening in this manner can lead to false positives, which can heighten patient anxiety and expose them to potentially harmful or unnecessary tests (6). 
Below (Table 1) are a number of cardiac conditions that can be detected with screening - and estimated frequency. 
Table 1: Cardiac conditions that can be detected with screening, from most to least frequent.

Whilst concerns regarding cost-effectiveness have generally prevented widespread screening programmes, screening selected individuals referred to the cardiology clinic with a specific question in mind does not have large-scale cost implications.

General office screening methods

Here we focus on the general screening methods and specifically, ECG interpretation. 
Generally, outlines of the constituents of positive screening findings based upon history, physical examination and 12-Lead electrocardiogram are available in the literature (7).
Initally, all patients presenting in our offices and asking ‘Do I have disease “x”?’ should be questioned on 1) family history of the specific disease or sudden cardiac death as well (straightforward) as 2) personal history of symptoms (Table 2). 

Table 2: Italian criteria for a positive personal history (6)

Criteria
Syncope or near syncope
Exertional chest pain or discomfort
Shortness of breath or fatigue out of proportion to the degree of physical effort
Palpitations or irregular heartbeat

In turn, to help to prevent unnecessary investigation or conversely false reassurance:

• Table 3 highlights which ECG abnormalities are considered abnormal and warrant further investigation. 
• Table 4 (8) compares the normal ECG changes associated with athletic training with those deemed potentially pathological. 

Table 3: European criteria for positive 12 lead electrocardiography (7)

European criteria for positive 12 lead electrocardiography

P wave
Left atrial enlargement: negative portion of P wave in lead V1 of depth ≤0.1 mV and duration ≥0.04 seconds
Right atrial enlargement: peaked P wave in leads II and III or V1 of ≥0.25mV amplitude

• QRS complex

• QRS axis deviation: right ≥120° or left −30° to −90°*
  Increased voltage: amplitude of R wave or S wave in a standard lead of ≥2mV, S wave in lead V1 or V2 of ≥3mV, or R wave in lead V5 or V6 of ≥3mV
  Pathological Q waves: duration ≥0.04 seconds, or ≥25% of the height of the ensuing R wave, or QS pattern in two or more leads
  Right or left bundle branch block with QRS duration of ≥0.12 seconds
  R or R’ wave in lead V1 ≥0.5 mV in amplitude and R/S ratio of ≥1

ST segment, T waves, and QT interval
ST segment depression, T wave flattening, or inversion in two or more leads
Prolongation of heart rate corrected QT interval of >0.44 seconds in males and >0.46 seconds in females

Rhythm and conduction abnormalities

Premature ventricular beats or more severe ventricular arrhythmias
Supraventricular tachycardias, atrial flutter, or atrial fibrillation
Short PR interval (<0.12 seconds) with or without ‘delta’ wave
Sinus bradycardia with resting heart rate ≤40 beats/min (Increasing less than 100 beats/min during limited exercise test)
First (PR ≥0.21 seconds - not shortening with hyperventilation or limited exercise test), second or third degree atrioventricular block

Table 4: Training-related vs. training un-related ECG changes (8)

Echocardiography

Echocardiography during heart screening can 1) reduce false positives as well as 2) detect myocardial and structural abnormalities that would be missed with only a 12-lead ECG. Nevertheless, echocardiography has not been widely taken up for pre-participation screening and they are additional costs, reduced equipment availability and additional time required for its study. 
With the development of new portable ultrasound techniques, hand-held echocardiography is starting to be used as an additional resource for screening, particularly in the community setting.

Conclusions

Pre-participation heart screening can reduce the risk of sudden cardiovascular death but there is a recognised false positive rate. It is important to ask about personal symptoms as well as a family history of specific conditions or sudden cardiac death. The European Society of Cardiology recommends performing a 12-lead ECG as part of general screening. Separating ECG findings into training related and non-training related changes will help reduce false positive investigations. Hand-held echocardiography can be quick and effective and potentially reduce the need for more expensive follow-on testing.
For a look at genetic testing in cardiomyopathies, you will find a e-journal article. On how to conduct pre-participation screening in athletes, find an article from the EACPR that descibes the steps.