Inherited cardiac conditions are common but often misdiagnosed so it is essential health professionals know the symptoms and when to refer to cardiac experts
In this article…
- The pathology of inherited cardiac conditions
- Definition and UK prevalence of inherited cardiomyopathies
- Definition and UK prevalence of inherited arrhythmias
Janet Hunt is cardiac genetics nurse specialist; Lorraine Cadd is inherited cardiac syndromes nurse specialist; both at Queen Elizabeth Hospital Birmingham and West Midlands Regional Genetics Unit, Birmingham Women’s Hospital - inherited cardiac syndromes service.
Hunt J, Cadd L (2013) Rare diseases 2: treatment of inherited cardiac conditions. Nursing Times; 109: 45, 16-18.
Inherited cardiac conditions are difficult to detect and screen for. Part 2 of our six part series on rare diseases explains why health professionals need to be aware of the symptoms associated with inherited cardiac conditions so they can make swift referrals to expert services.
5 key points
- An estimated 12 people aged 35 years or under die each week in the UK from undiagnosed cardiac conditions
- Most sudden cardiac deaths are a result of inherited cardiomyopathies and arrhythmias
- Many patients with cardiomyopathies and arrhythmias are undiagnosed or their symptoms are thought to be due to another illness
- Difficulties in diagnosing arrhythmias make it almost impossible to clinically screen relatives
- Treatment of cardiomyopathy will not cure the patient, but can control symptoms
It is estimated that every week in the UK, 12 apparently fit and healthy young people aged 35 years or under die from undiagnosed cardiac conditions (Papadakis et al, 2009). Sudden cardiac death (SCD) or a serious event in an otherwise healthy young person raises the possibility of an underlying genetic condition and suggests their relatives may also be at risk.
The underlying cardiac pathology of inherited cardiac conditions (ICCs) can be structural or non-structural and fall into five main categories:
- Muscular dystrophies;
- Familial hypercholesterolaemia.
The majority of SCDs are due to inherited cardiomyopathies and arrhythmias (Elliott et al, 2011). Genetic diseases of the heart are caused by a mutation in one or more of the genes that affect the structure or function of the heart muscle or conduction pathways (Kumar and Elliott, 2010).
The majority of ICCs are inherited in dominant genes, with a small number inherited recessively.
Cardiomyopathies can be divided into five specific subgroups: hypertrophic; dilated; arrhythmogenic; restrictive; and unclassified (Elliott et al, 2008). Table 1 gives the definitions and prevalence of these subgroups.
The clinical course of cardiomyopathies and arrhythmias is variable. Many patients are asymptomatic or present with symptoms that can be misdiagnosed as asthma or epilepsy. Symptoms can include:
- Shortness of breath (dyspnoea);
- Chest pain (angina);
- Irregular heartbeat (palpitations);
- Light-headedness or dizziness (presyncope);
- Fainting (syncope);
- Sudden unexplained cardiac death.
Arrhythmias/cardiac ion channelopathies
Long QT syndrome, short QT syndrome and Brugada syndrome belong to a group of arrhythmic syndromes called cardiac ion channelopathies (CICs) (Martin et al, 2012). Other rare arrhythmia syndromes include catecholaminergic polymorphic ventricular tachycardia and Wolff-Parkinson-White syndrome (Table 2).
An arrhythmia that causes SCD leaves no signs and can be virtually impossible to diagnose during a post mortem, even by an expert cardiac pathologist. This makes it difficult to effectively clinically screen first-degree relatives and requires the expertise of a clinician with appropriate CIC expertise and advanced electrocardiogram interpretation skills, such as a consultant cardiologist or electrophysiologist (Cardiac Risk in the Young, 2003). Symptom onset is often sudden, and includes palpitations, presyncope or syncope.
It is important to recognise patients who may be presenting with an arrhythmic syndrome or CIC and to seek prompt medical assessment from an expert clinician (Wilson et al, 2008). As many of these syndromes are likely to be inherited, it may be appropriate to refer immediate family members quickly but sensitively for clinical screening and genetic testing. Several regional ICC services across the country provide counselling, clinical screening and genetic testing; a list of these is on the Association for Inherited Cardiac Conditions website (Box 1).
Treatment for cardiomyopathies and arrhythmias will not reverse the condition but is often effective in controlling symptoms, particularly if used in conjunction with lifestyle changes.
If a patient’s risk stratification shows a risk of SCD, the cardiologist will discuss the need for an implantable cardiac defibrillator (CRY, 2003).
Sometimes, cardiomyopathy symptoms can mimic those of congestive heart failure (especially activity intolerance and dyspnoea). It is essential to get an accurate diagnosis as treatment is very different - diuretics work well in heart failure but can exacerbate symptoms in cardiomyopathy (Jessop et al, 2009).
Beta-blockers (such as nadolol or bisoprolol) are commonly used for both cardiomyopathies and arrhythmias. These can slow the heart rate and make the heart contract less forcefully, allowing more time for the ventricle to fill with each heartbeat and helping to reduce chest pain, breathlessness and palpitations. Competitive sports are not advisable for patients taking beta-blockers due to the possibility of sudden collapse or increased heart failure (Gersh et al, 2011).
The role of clinical nurse specialists is to facilitate streamlined care for referred families.
We are often the first point of contact for those who have lost a relative due to SCD or are diagnosed with an ICC that may affect other family members. Families often feel frightened and unsure of the next steps - as specialist nurses we “walk alongside” them through the process. We offer support and guidance, obtain the family history, organise cardiac investigations and ensure relevant medical notes are available to coordinate families through a one-stop shop clinic with cardiologists and geneticists for clinical screening, genetic testing and follow-up where needed.
Bjerregaard P, Gussak I (2005) Short QT Syndrome. Annals of Non-invasive Electrophysiology; 10: 4, 436-40.
Burkett EL, Hershberger RE (2005) Clinical and genetic issues in familial dilated cardiomyopathy. Journal of the American College of Cardiology; 45: 969-981.
Elliott P et al (2011) Inherited Cardiac Disease. Oxford: Oxford University Press.
Elliott P et al (2008) Classification of the cardiomyopathies: a position statement from the European Society Of Cardiology Working Group on Myocardial and Pericardial Diseases. European Heart Journal; 29: 2, 270-276.
Gersh B et al (2011) Guideline for the diagnosis and treatment of hypertrophic cardiomyopathy. Circulation; 8, 1-36.
Gollob MG et al (2001) Identification of a gene responsible for familial Wolff-Parkinson-White Syndrome. The New England Journal of Medicine; 344: 1823-1831.
Jessop M et al (2009) ACCF/AHA guidelines for the diagnosis and management of heart failure in adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines: developed in collaboration with the International Society for Heart and Lung Transplantation. Circulation; 119: 14, 1977-2016.
Kumar D, Elliott P (2010) Principles and Practice of Clinical Cardiovascular Genetics. Oxford: Oxford University Press.
Maron BJ et al (2006) Contemporary definitions and classification of the cardiomyopathies: an American Heart Association Scientific Statement from the Council on Clinical Cardiology, Heart Failure and Transplantation Committee; Quality of Care and Outcomes Research and Functional Genomics and Translational Biology Interdisciplinary Working Groups; and Council on Epidemiology and Prevention. Circulation; 113, 1807-1816.
Papadakis M et al (2009) The magnitude of sudden cardiac death in the young: a death certificate-based review in England and Wales. Europace; 11: 10, 1353-1358.
Sen-Chowdhry S et al (2004) Arrhythmogenic right ventricular cardiomyopathy: clinical presentation, diagnosis, and management. American Journal of Medicine; 117: 9, 685.
Sharkey SW et al (2010) Natural history and expansive clinical profile of stress (tako-tsubo) cardiomyopathy. Journal of the American College of Cardiology; 55: 4, 333-341.
Wilson MG et al (2008) Efficacy of personal symptom and family history questionnaires when screening for inherited cardiac pathologies: the role of electrocardiography. British Journal of Sports Medicine; 42: 207-211.