How do I investigate the relatives of a patient with sudden cardiac death?

In patients aged over 30 years by far the commonest cause of sudden cardiac death is coronary disease (80%). In patients younger than this, inherited disorders play a major role, with hypertrophic cardiomyopathy accounting for approximately 50% of these deaths. Although perhaps not entirely representative of the general population, the most systematically collected data on sudden death in young people comes from athletes. Aortic root dissection and arrhythmias due to accessory pathways and long QT syndromes may also be causative. A specific diagnosis in the deceased should be pursued by means of expert examination of the postmortem heart if available and attempts to obtain antemortem electrocardiograms and other investigations.

In general first-degree relatives should undergo history, physical examination, 12-lead electrocardiography and 2-D echocardiography. Other investigations may also be performed depending on the suspected cause of death, such as exercise testing in suspected long QT syndrome. In the case of a suspected inherited condition, if both parents of the deceased can be evaluated and found to be free of abnormalities, the condition causing death is likely to have been sporadic and the chances of siblings being affected are low. However, this inference must be tempered by the realisation that some inherited conditions (including hypertrophic cardiomyopathy) may be associated with incomplete penetrance. Extended pedigree analyses have demonstrated that occasionally apparently unaffected individuals, termed “obligate carriers”, carry the mutation. A follow up strategy after an initial negative evaluation is empirical, and depends on the age of the person, the level of anxiety and the nature of the suspected condition.