Cardiomyopathy:
how it is diagnosed and which tests are needed

Article written and reviewed by Dr Luca Moretti

The diagnosis of cardiomyopathy does not depend on a single test. It usually begins with the clinical and family history, a cardiology assessment, electrocardiogram and echocardiogram; depending on what emerges, Holter monitoring, exercise testing, cardiac magnetic resonance imaging, blood tests, genetic testing and other targeted investigations may be added.
The aim is not only to establish that the heart muscle is abnormal, but to understand which phenotype is present, what may be causing it and what risks it carries. This is important because different cardiomyopathies may require different follow-up, treatments and screening of family members.

The investigations most frequently used include:

• personal and family history and a cardiology examination;
• 12-lead electrocardiogram;
• transthoracic echocardiogram;
• Holter ECG monitoring or longer recordings when indicated;
• cardiac magnetic resonance imaging;
• blood tests selected according to the clinical picture;
• genetic testing and genetic counseling in appropriate cases;
• exercise testing, coronary imaging, scintigraphy or biopsy in selected situations.

Cardiomyopathies include different phenotypes and numerous possible causes. For this reason, modern guidelines recommend a multiparametric pathway: the shape and function of the heart are the starting point, but a complete diagnosis requires integration of imaging, heart rhythm, family history, extracardiac manifestations and, when useful, genetics.

Diagnosis begins with the clinical history and the family

Before instrumental tests, it is important to reconstruct the symptoms, when they began and under what circumstances they occur. Shortness of breath, reduced exercise capacity, chest pain, palpitations, dizziness and syncope can guide the diagnostic pathway, but they must be interpreted together with blood pressure, medications, alcohol consumption, exposure to cardiotoxic substances, previous infections, systemic diseases and other conditions that may cause myocardial damage.
The family history is also part of the diagnostic investigation. Cardiomyopathies, heart failure without a clear cause, heart transplantation, sudden death, ventricular arrhythmias, or pacemakers or defibrillators implanted in relatively young relatives may suggest an inherited predisposition.

Physical examination may reveal murmurs, rhythm abnormalities, signs of congestion or other abnormalities, but cardiomyopathy can also be present with an unremarkable physical examination. It is therefore the combination of information that determines which tests are needed and with what priority.

ECG and echocardiogram: the basic tests

The electrocardiogram records the electrical activity of the heart. It may show repolarization abnormalities, signs of hypertrophy, conduction disorders, pathological waves or arrhythmias. None of these abnormalities, taken in isolation, automatically identifies cardiomyopathy, but certain patterns can point toward specific phenotypes or indicate the need for further investigation.

The echocardiogram, on the other hand, allows the structure and function of the heart to be observed in real time: chamber dimensions, wall thickness, systolic and diastolic function, valves, atria, right ventricle, estimated pressures and possible obstructions. It is essential, for example, for recognizing a dilated ventricle with reduced function in dilated cardiomyopathy or an unexplained increase in myocardial thickness in hypertrophic cardiomyopathy.
Echocardiography, however, mainly describes the phenotype. If the appearance of the heart is not sufficient to clarify the origin of the abnormality, tests that can better characterize the tissue or identify a specific cause are needed.

Holter monitoring and exercise testing: when rhythm and response to exercise need to be studied

An electrocardiogram lasts only a few seconds and may fail to record intermittent arrhythmias. Holter monitoring, performed for one or more days or replaced in selected cases by longer recordings, makes it possible to quantify premature beats, tachycardias, atrial fibrillation and other rhythm abnormalities. It is particularly important when palpitations or syncope are present, in arrhythmogenic cardiomyopathy, or when the number and type of arrhythmias contribute to risk assessment.

The exercise test can be used to assess functional capacity, the blood pressure and rhythm response to exercise, and the onset of symptoms. In hypertrophic cardiomyopathy, it can also help reveal a dynamic obstruction that is absent at rest or is not sufficiently defined. In other cases, it may be combined with measurement of respiratory gases to quantify cardiopulmonary capacity more precisely.
These tests are not performed in the same way for everyone: their type, duration and intensity depend on the clinical question and the person's risk profile.

Cardiac magnetic resonance imaging: why it has become so important

Cardiac magnetic resonance imaging has a central role in the modern diagnostic pathway for cardiomyopathies. It accurately measures ventricular volumes, mass and function and, above all, makes it possible to characterize myocardial tissue. With specific techniques, it can identify fibrosis and scars, edema, infiltration or accumulation of substances, providing information that echocardiography cannot always supply.
The pattern and distribution of so-called late gadolinium enhancement, together with T1 and T2 mapping and other parameters, can help distinguish different phenotypes and point toward certain causes. Cardiac MRI can therefore contribute not only to diagnosis but also to prognostic stratification and treatment decisions.

This does not mean, however, that every abnormality seen on MRI automatically corresponds to a diagnosis. The results must be integrated with ECG, echocardiography, family history, laboratory tests and the clinical context. The choice of contrast medium and whether the examination can be performed also depend on individual characteristics.

Blood tests, genetics and tests targeted to the cause

Laboratory tests are used both to assess the consequences of heart disease and to look for conditions that can cause or mimic cardiomyopathy. Depending on the case, they may include a complete blood count, kidney and liver function tests, electrolytes, thyroid hormones, iron and ferritin, creatine kinase, troponin, natriuretic peptides and more specific tests for metabolic, autoimmune, infiltrative or storage diseases.
There is therefore no identical "cardiomyopathy panel" for everyone. The selection of tests should be guided by the phenotype and any extracardiac signs.

Genetic testing, accompanied by appropriate counseling, is indicated when it can help define the etiology, risk or management and when the result may be useful to family members. If a pathogenic or likely pathogenic variant consistent with the clinical picture is identified, relatives can undergo targeted testing for that variant.
In selected situations, tests to exclude coronary artery disease, scintigraphy or PET, invasive hemodynamic studies or endomyocardial biopsy may also be necessary. Biopsy is not a routine test: it is used when a specific disease is suspected in which tissue analysis can concretely change the diagnosis or treatment.

Frequently asked questions about the diagnosis of cardiomyopathy

What is the first test used when cardiomyopathy is suspected?
There is no single initial test that is appropriate for everyone. History, physical examination, ECG and echocardiography are generally combined.

Is an echocardiogram enough?
Not always. The results may need to be combined with Holter monitoring, cardiac MRI, blood tests, genetic testing or other investigations.

What is cardiac magnetic resonance imaging used for?
To accurately assess the structure and function of the heart and characterize myocardial tissue, identifying, for example, fibrosis, scars, edema or infiltrative patterns.

When is genetic testing performed?
When the clinical picture suggests an inherited form or when the result can clarify the etiology, guide management and enable targeted screening of family members.

Is a heart biopsy necessary for everyone?
No. It is reserved for selected cases in which tissue examination can answer a specific diagnostic question and change clinical management.