Cardiomyopathy

The word cardiomyopathy is used as a general term referring to the abnormal structure or function of the heart. 

Strictly speaking, the definition of cardiomyopathy excludes myocardial dysfunction due to coronary artery disease, systemic hypertension and valvular or congenital heart disease. However, you will still hear terms such as ‘ischaemic cardiomyopathy’ commonly used in clinical practice to describe heart failure secondary to ischaemia. 

Classification and Causes 

There is disagreement regarding the most effective way to classify cardiomyopathies and no universally accepted approach.   

The American Heart Association (AHA) favour using the terms: 

  • Primary: For diseases in which the heart is the sole or predominant organ involved
  • Secondary: For diseases where myocardial dysfunction is a consequence of a systemic disorder 

A diagram for primary cardiomyopathies and how these can be further subdivided is shown below (1). 

image 1

Figure 1: Graphical illustration of the aetiologies of primary cardiomyopathy. Sourced / adapted from (1).

Secondary causes include infiltrative (e.g. amyloidosis), storage (e.g. Fabry’s), toxicity (e.g. drugs) and many others. 

The problem with this classification is that many of the diseases classified as primary cardiomyopathies can be associated with major extra-cardiac manifestations. Equally, pathology in many of the diseases classed as secondary cardiomyopathies can predominantly (or exclusively) involve the heart. 

For this reason, the European Society of Cardiology (ESC) prefer a clinically oriented classification system where cardiomyopathies are grouped according to the ventricular appearance on imaging. A diagram is shown below (2).  

image 2

Figure 2: Classification of primary cardiomyopathies based primarily on ventricular appearance on imaging. Taken from European Society of Cardiology. Sourced / adapted from (2).

This system has its own flaws as there can often be significant overlap between these categories e.g. familial hypertrophic cardiomyopathy will show a hypertrophied LV (HCM) on imaging but as the disease progresses may also show restrictive (RCM) features.  

We will now explore some of the different types of cardiomyopathies in slightly more detail. 

Hypertrophic cardiomyopathy (HCM) 

Hypertrophic cardiomyopathies have increased ventricular wall thicknesses in the absence of abnormal loading conditions e.g. valve disease or hypertension.  

Causes of HCM include:  

Familial/ Genetic: 

  • Familial (accounts for 60% of cases. Autosomal dominant inheritance) 
  • Noonan’s syndrome 

Non familial/ non genetic: 

  • Obesity 
  • Drugs e.g. anabolic steroids 

Signs and symptoms of HCM can be varied but include:  

  • Angina: due to increased oxygen demand from the hypertrophied ventricle.
  • Heart failure: diastolic impairment from a stiff, non-compliant ventricle.  
  • Syncope: due to ventricular arrythmias or left ventricular outflow tract obstruction present in some cases, 
  • Sudden cardiac death (SCD): usually from heart failure, thromboembolism and ventricular arrhythmias.
    • HCM is the most common cause of SCD in young people. 

The diagnostic work up includes:  

  • History and examination: family history including SCD, signs and symptoms as mentioned above. 
  • 12 lead ECG: variable findings but LVH, pathological Q waves, ST and T wave abnormalities are common. 
  • Cardiac imaging: to establish the severity and pattern of LVH and to assess for complications e.g. left ventricular outflow tract obstruction.
    • Echocardiography is the most commonly used imaging modality but CMR can also be useful to differentiate tissue types e.g. physiological hypertrophy (e.g. athletes) versus hypertrophy secondary to fibrosis as seen in familial HCM. 
  • Genetic testing: 60% of HCM is familial and inherited in an autosomal dominant pattern. The patient and other family members should have genetic testing and counselling.   

Many people with HCM are asymptomatic. Treatment of asymptomatic people depends on the underlying cause and involves preventing disease progression, heart failure and arrhythmias.  

In patients with symptomatic left ventricular outflow obstruction, drugs (beta blockers/ verapamil), surgery (ventricular septal myectomy) or septal alcohol ablation can be used. 

Symptoms such as heart failure and arrhythmias should be treated as per the usual management of these conditions.   

Unfortunately, the incidence of SCD in HCM is 1-2% per year from heart failure, thromboembolisms and ventricular arrhythmias.  

The ESC has a “HCM risk-SCD calculator” to determine an individual’s risk of SCD and whether they should have an ICD.   

It takes many factors into account including :  

  • Age  
  • Family history of sudden cardiac death  
  • Unexplained syncope  
  • Left ventricular outflow gradients  
  • Maximum left ventricular wall thickness 
  • Left atrial diameter  
  • Non sustained ventricular tachycardia 

Patients with progressive disease which does not respond to treatment should be considered for heart transplantation.  

The following are possible ECG changes you may expect to see:

image 3

Figure 3: An ECG illustrating the changes in HCM. We can note evidence of Left Ventricular Hypertrophy in some of the precordial leads (V1-V4) alongside pathological Q waves in the inferior leads (II, III, aVF). Sourced from W.G. de Voogt, MD, PhD, SLAZ, The Netherlands (CC BY-SA 3.0)

Dilated cardiomyopathy (DCM) 

Dilated cardiomyopathies have left ventricular dilatation and dysfunction in the absence of abnormal loading (e.g. valve disease) or coronary artery disease.  

[Note: it is common for patients to develop a thin and dilated LV after myocardial infarction. In clinical practice this is often referred to as ‘ischaemic cardiomyopathy’ but the AHA and ESC avoid using this term. They explicitly exclude IHD causes from their definition of cardiomyopathy].  

Causes 

  • Familial 
  • Non familial/ genetic:
    • Drugs inc. alcohol 
    • Pregnancy 
    • Tachycardiomyopathy 

The signs and symptoms of DCM reflect the heart failure and arrhythmias it causes.  

Again, the diagnosis relies on history, echo findings and genetic testing.  

Treatment is focused on removing any triggers e.g. drugs/ alcohol, and the standard heart failure and arrhythmia management.  

ECG example (3):

image 3 1

Figure 4: ECG illustrating the changes in non-ischaemic dilated cardiomyopathy. We can note deep Q waves in the inferior leads, poor R wave progression in the precordial leads and evidence of right cardiac axis deviation. Sourced / adapted from (3).

Arrhythmogenic right ventricular cardiomyopathy (ARVC) 

ARVC is a condition where the right ventricle is infiltrated by fibro-fatty tissue. It is genetic and has autosomal dominant inheritance.  

Signs and symptoms are typically aggravated by exercise and include ventricular arrhythmias, progressive heart failure and sudden cardiac death. ARVC is the second most common cause of SCD in young people after HCM.  

ECG findings include:  

  • Epsilon waves
    • Attributed with dyssynchronous excitation of myocytes
    • Functioning mycotes are interspaced with fatty tissue, which causes delays on myocyte contraction. This means some myocytes have a delay in contraction, producing a second upstroke after the QRS complex
  • TWI in V1-3 (and beyond) 
  • Frequent ventricular ectopics with an LBBB morphology 

A diagnosis of ARVC is a based on meeting various criteria from: 

  • Structural imaging (echo and MRI- generally shows a dilated, impaired RV) 
  • Histology samples  
  • ECG changes 
  • Family history  

ECG example (4):

image 3

Figure 5: ECG illustrating arrhythmogenic right ventricular hypertrophy. We can note the Episilon wave in V1-V2 with T wave inversion in V1-V3. Sourced / adapted from (4).

See “ARCV task force criteria” at the bottom of the page for full details of the diagnostic criteria. 

Restrictive cardiomyopathy (RCM) 

Restrictive cardiomyopathies are probably the least common forms of cardiomyopathy.  

They result from increased stiffness of the ventricles which then only allows small volumes of filling during diastole.  

Causes:  

  • Familial (autosomal dominant) 
  • Non familial/ genetic: 
  • Idiopathic   
  • Amyloidosis 
  • Sarcoidosis 

As mentioned previously, other cardiomyopathies often develop a restrictive pattern when they become advanced e.g. familial HCM. 

ECG changes include low voltage QRS and conduction defects e.g. AV block and bundle branch blocks. 

ECG example (5):

image 4

Figure 6: An ECG illustrating restrictive cardiomyopathy secondary to amyloidosis. We can note low voltage QRS complexes and diffuse flattening of the T waves. Sourced / adapted from (5).

Unclassified cardiomyopathies 

Unclassified cardiomyopathies include: 

  • Takotsubo cardiomyopathy: (everyone’s favourite- named after the Japanese pots used to catch octopus) also known as stress induced cardiomyopathy. Involves apical LV ballooning and dysfunction due to emotional or physical stress (catecholamine release). Symptoms include: angina-like chest pain, diffuse T wave inversion, ST changes and a mild troponin rise. It’s a transient disease and LV function normalises in days-weeks.  
  • Left ventricular non compaction: a congenital cardiomyopathy which results in a ‘spongy’ left ventricle with prominent trabeculations and deep recesses in the LV cavity due to non-compaction of the endocardial layer of the heart.  

References

  1. Maron BJ, Towbin JA, Thiene G, Antzelevitch C, Corrado D, Arnett D, et al. 2006 Apr 11. 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 Functio. Circulation. 113(14):1807–16.
  2. Elliott P, Andersson B, Arbustini E, Bilinska Z, Cecchi F, Charron P, et al. 2007 Dec 12. Classification of the cardiomyopathies: a position statement from the european society of cardiology working group on myocardial and pericardial diseases. Eur Heart J. 29(2):270–6.
  3. Drezner JA, Ashley E, Baggish AL, Börjesson M, Corrado D, Owens DS, et al. 2013 Feb 9. Abnormal electrocardiographic findings in athletes: recognising changes suggestive of cardiomyopathy. Br J Sports Med. 47(3):137–52.
  4. Gibson M. Arrhythmogenic right ventricular dysplasia ECG – wikidoc [Internet]. [cited 2023 Mar 12]. Available from URL: https://www.wikidoc.org/index.php/Arrhythmogenic_right_ventricular_dysplasia_ECG
  5. Abdelazeem B, Malik B, Baral N, Gjeka R, Kunadi A. 2021 Mar 16. A Case Report of Sick Sinus Syndrome as an Initial Presentation of Primary Amyloidosis. Cureus.

Useful links

Author: Dr. Shiraz Khan (FY2)

Reviewed by Dr. S Scholfield (FY3)

Reviewed and edited by Dr. Lucy Priestner (Cardiology ST4)

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