Echocardiography of the heart walls

Assessment of hypertrophy and obstruction

EchoCG allows the identification of various variants of myocardial thickening: asymmetric, septal, symmetric, apical, midventricular (midventricular), noncontiguous (noncontiguous), and mass-like (mass-like).

Classic hypertrophic cardiomyopathy (HCM) is characterized by interventricular septum (IVS) thickening of more than 15 mm in a non-dilated left ventricle. If the patient has symptoms (dyspnea, syncope, chest pain) or specific ECG changes, this isolated sign is sufficient for diagnosis. As an additional criterion, the ratio of IVS thickness to the posterior wall at the midventricular level is assessed — it must exceed 1.3.

In 25% of patients with asymmetric or septal hypertrophy, left ventricular outflow tract (LVOT) systolic obstruction develops. It is based on the Venturi effect, where the anterior mitral valve leaflet is drawn toward the hypertrophied septum. Doppler ultrasound allows the recording of a systolic pressure gradient, and the assessment of transmitral blood flow demonstrates diastolic dysfunction: the amplitude of the early filling E wave decreases and becomes comparable to the atrial systole A wave.

Method limitations and alternatives

Despite ubiquitous availability, EchoCG has several strict limitations:

• Apical patterns of hypertrophy are difficult to visualize due to the apex being located too close to the low-frequency ultrasound transducer.
• Mass-like changes require complex differential diagnosis, as ultrasound cannot reliably distinguish a hypertrophied area from a true neoplasm.
• Poor acoustic window (e.g., due to patient constitution) makes the study uninformative.

In such situations, tomographic methods are used. Computed tomography (CT) provides accurate information on wall thickness at a very low radiation dose (1–3 mSv), but does not yet have proven advantages over magnetic resonance imaging (MRI) in diagnosing non-ischemic diseases.

Capabilities of MRI in myocardial assessment

MRI compensates for the shortcomings of ultrasound, allowing precise measurement of left ventricular mass and assessment of right heart involvement. The main advantage of this method is its unique ability to visualize interstitial fibrosis.

Due to impaired contrast washout (wash-out) and expansion of the extravascular collagen bed, the late gadolinium enhancement (late gadolinium enhancement, LGE) technique is used. Fibrous tissue retains gadolinium and appears as a "bright" myocardium against the healthy "dark" background on images. This is critically important for clinical practice, as pronounced fibrosis is directly associated with the risk of severe arrhythmias via the re-entry mechanism and increases the likelihood of sudden cardiac death in patients under 40 years of age.

Modern technologies include T1 mapping (T1 mapping), which allows the calculation of the extracellular volume fraction (extracellular volume, ECV). This parameter helps differentiate pathology from normal state: in HCM or dilated cardiomyopathy (DCM), the ECV index increases due to cardiomyocyte disorganization and fibrosis, whereas in the physiological "athlete's heart" it decreases due to an increase in the volume of healthy muscle cells.

Differential diagnosis of phenotypes

The hypertrophic phenotype (significant wall thickening) occurs not only in HCM. Analysis of contrast enhancement patterns on MRI allows precise determination of the cause of the lesion:

1. Anderson-Fabry disease: typical subepicardial contrast enhancement in the inferolateral wall.
2. Amyloidosis: diffuse protein infiltration impairs the suppression of the myocardial signal, forming a focal intramural or diffuse bright pattern.
3. Sarcoidosis: a patchy distribution with small foci, reflecting granulomatous inflammation.

In the dilated phenotype, when the left ventricle dilates without relation to ischemia or hemodynamic overload, the walls do not thicken, but diffuse fibrosis also forms within them. On MRI, native T1 values increase, which inversely correlate with wall thickness, and thrombi characteristic of this disease can be clearly visualized in the ventricular cavity.

Class and exam questions

What else to study on this topic

• Clinical significance and prognostic role of myocardial fibrosis
• Principles of T1, T2, and T2* mapping in cardiology
• Calculation of the myocardial extracellular volume (ECV) fraction
• Myocardial pathomorphology: cardiomyocyte disarray
• MRI presentation of infiltrative lesions: amyloidosis, Fabry disease, sarcoidosis

Other topics in the «Chest Radiology» section

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