Dilated & Restrictive Cardiomyopathy

Dilated Cardiomyopathy (DCM)

Dilated cardiomyopathy is the most common cardiomyopathy encountered in general echo labs and is characterized by left ventricular (and often biventricular) dilation with global systolic dysfunction that is disproportionate to any abnormal loading condition or coronary artery disease. Etiologies span idiopathic, familial/genetic, viral/post-myocarditis, peripartum, toxin-related (alcohol, anthracycline chemotherapy), and tachycardia-induced forms; regardless of cause, the echocardiographic phenotype converges on a common pattern.

Key 2D/M-mode and Doppler findings

• LV cavity enlargement — LV end-diastolic diameter typically exceeds the upper limit of normal (commonly >58-60 mm, or an LVEDD index >3.2 cm/m²).
• Global hypokinesis — reduced endocardial excursion and wall thickening affecting essentially all segments equally, in contrast to the regional pattern seen with ischemic disease.
• Reduced ejection fraction — EF is usually well below 40%, often in the 15-30% range in advanced disease; this is the defining functional abnormality of heart failure with reduced ejection fraction (HFrEF).
• Increased sphericity — the normally elliptical LV remodels toward a more spherical shape; the sphericity index (LV short-axis diameter divided by long-axis length) rises toward 1, and apical rounding is common.
• Functional (secondary) mitral regurgitation — the MV leaflets are structurally normal, but annular dilation plus symmetric or asymmetric leaflet tethering from papillary muscle displacement prevents coaptation, producing a central-to-posterior MR jet. Severity tracks the degree of LV remodeling rather than intrinsic valve pathology.
• Diminished tissue Doppler and stroke volume indices — reduced mitral annular s′ and e′ velocities, reduced LVOT VTI/stroke volume, and frequently a restrictive or pseudonormal diastolic filling pattern superimposed on the systolic dysfunction.
• Apical thrombus risk — apical flow stasis from severely reduced EF and spherical remodeling predisposes to LV apical thrombus; every study on a low-EF ventricle should specifically screen the apex (contrast or harmonics if endocardial definition is poor).
• Dyssynchrony clues — a widened QRS with septal-to-posterior wall motion delay on M-mode can flag mechanical dyssynchrony relevant to cardiac resynchronization therapy candidacy, though it is not a primary diagnostic criterion for DCM itself.

Restrictive Cardiomyopathy (RCM)

Restrictive cardiomyopathy is the least common of the three classic cardiomyopathy phenotypes (dilated, hypertrophic, restrictive) but is critical to recognize because its echocardiographic signature is nearly the mirror image of DCM.

Key findings

• Normal or near-normal LV cavity size with preserved, or only mildly reduced, EF — systolic function is often deceptively normal despite severe symptoms, because the disease primarily impairs diastolic compliance rather than contractility.
• Marked biatrial enlargement — both atria dilate significantly (often described as a 'cherry on a stick' appearance against a normal-sized ventricle) because chronically elevated filling pressures are transmitted backward into the atria.
• Restrictive diastolic filling pattern — mitral inflow shows a tall E wave, a blunted A wave, an E/A ratio >2, and a short deceleration time (DT), classically <150 ms, reflecting a stiff ventricle that fills almost entirely in early diastole with minimal atrial contribution.
• Elevated filling pressures — E/e′ is typically elevated and left atrial volume index (LAVi) is increased, both consistent with chronically high left atrial pressure.
• Etiology-specific wall findings — infiltrative causes such as cardiac amyloidosis classically produce increased LV wall thickness with a granular, 'speckled/sparkling' myocardial texture, often paired with a disproportionately low-voltage ECG relative to the degree of wall thickening (a useful clinical discordance clue). Other infiltrative/storage etiologies include cardiac sarcoidosis and hemochromatosis; idiopathic disease and endomyocardial fibrosis are non-infiltrative causes.

RCM vs. constrictive pericarditis

Because both conditions produce a 'restrictive' clinical and Doppler picture, differentiating restrictive cardiomyopathy (myocardial disease) from constrictive pericarditis (pericardial disease) is a frequently tested discrimination:

The 'annulus reversus' pattern (medial e′ ≥ lateral e′) is a particularly useful clue for constriction, because in most other cardiac conditions — including RCM — lateral e′ normally exceeds medial e′ due to tethering effects near the septum.

Strain imaging and secondary clues

Speckle-tracking longitudinal strain adds a further discriminator in suspected amyloid RCM: a 'relative apical sparing' pattern — markedly reduced basal and mid-ventricular longitudinal strain with relatively preserved apical strain — appears on the polar (bullseye) map and is characteristic of infiltrative amyloid infiltration, which preferentially affects the base. Secondary findings supporting RCM over other causes of dyspnea include a thickened, hyperrefractile interatrial septum and valve leaflets (amyloid infiltration), a small or normal-sized pericardial effusion, and elevated estimated pulmonary artery pressure from chronically elevated left-sided filling pressures transmitted backward through the pulmonary vasculature.

Sonographic role

Quickly recognizing these two patterns on a limited or bedside study, then triaging toward the correct confirmatory workup (cardiac MRI with late gadolinium enhancement or biopsy/scintigraphy for RCM/amyloid subtyping; CT for pericardial thickening or calcification in constriction), is a core AE clinical-integration skill and a recurring exam scenario.