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McMaster Textbook of Internal Medicine

Unclassified Cardiomyopathies

How to Cite This Chapter: Da C.Z. Borjaille C, Demers C, Connolly K, Roberts J, Wodniecki J, Leśniak W. Unclassified Cardiomyopathies. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. https://empendium.com/mcmtextbook/chapter/B31.II.2.16.5. Accessed December 05, 2025.
Last Reviewed: June 3, 2025
Last Updated: June 3, 2025
Chapter Information

1. Stress-induced (takotsubo) cardiomyopathy is a nonfamilial cardiomyopathy characterized by acute left ventricular (LV) dysfunction after emotional, physical, or physiologic stress. It is a form of myocardial stunning that is associated with hyperkinesis of the basal LV segments, akinesis of mid LV segments, and dyskinesis of the apical LV segments.

Clinically takotsubo cardiomyopathy can present with ST-segment elevations followed by inverted T waves associated with chest pain and elevations in serum troponin levels. As such, this is a diagnosis of exclusion after acute coronary syndrome has been ruled out. Complications can include LV outflow tract obstruction, shock, LV thrombus, as well as ventricular and atrial arrhythmias. Given the transient nature of the phenomenon, LV contractility often normalizes within days to weeks, and electrocardiography changes resolve much later, within weeks or months. For this reason classification as a cardiomyopathy is not recommended. The prognosis is often good unless complications arise.

2. LV noncompaction or LV hypertrabeculation is a ventricular phenotype characterized by prominent trabeculations in the LV myocardium due to failure of compaction of the trabeculae during gestation. Although frequently seen as a familial trait, it has also been described as acquired and associated with a transient phenomenon in athletes and during pregnancy. For this reason, it should not be considered a cardiomyopathy. Clinical features include systolic dysfunction with heart failure, thromboembolic complications, arrhythmias, and sudden cardiac death. Diagnosis is made based on characteristic features found on echocardiography (Figure 3.6-5) and confirmed by cardiac magnetic resonance (CMR) (Figure 3.6-1).

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Figure 3.6-5. Transthoracic echocardiography (TTE) of a patient with left ventricular noncompaction (apical 4-chamber view, standard probe placement): A, 2D imaging; B, color Doppler examination; C, enlarged panel A; D, color Doppler examination. Yellow arrows mark the spongiform structure of the myocardium in the mid and apical segments of the left ventricle (LV). The layer of the abnormal cardiac muscle is more than twice as thick as the healthy compact layer. A healthy apex of the right ventricle (RV) usually has numerous myocardial trabeculae. For this reason, despite the significantly increased trabeculation (white arrow), it is not clear if this finding can be considered abnormal. Color Doppler revealed blood flow penetrating deep into both ventricular apexes, which indicates that tissue in this area is not solid (a solid tissue structure would be typical for apical hypertrophic cardiomyopathy or ventricular cavities filled with thrombi or other masses). The interatrial septum is markedly protruding to the right (red arrow), which meets the diagnostic criteria for atrial septal aneurysm. LA, left atrium; RA, right atrium. Figure courtesy of Dr Andrzej Gackowski.

Figure 3.6-1. Left ventricular (LV) hypertrabeculation on cardiac magnetic resonance (CMR). The major marker is the presence of several prominent trabeculations in the LV with topographic involvement of apical and mid segments of the lateral and inferior walls. A noncompacted-to-compacted ratio >2.3 on CMR is considered the cutoff for the diagnosis of left ventricular noncompaction. Figure courtesy of Dr Danielle Walker.

 

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