14.2 Restrictive, Arrhythmogenic, and Stress Cardiomyopathies

Restrictive physiology is not a single diagnosis

A restrictive cardiomyopathy (RCM) phenotype reflects stiff myocardium: ventricular diastolic pressure rises steeply with a small increase in volume. Ventricles may be normal or small with preserved EF early, while both atria enlarge, AV-valve regurgitation develops, pulmonary pressure rises, and systemic venous congestion appears. Advanced disease can reduce systolic function. Record mitral and tricuspid inflow, septal and lateral e′, E/e′ in its valid context, pulmonary and hepatic venous flow, LA and RA volumes, RV size/function, IVC, PASP, GLS, and pericardium. A short deceleration time, high E/A, short IVRT, and low annular e′ form a restrictive filling pattern but do not name its cause.

Wall thickness guides the differential without settling it. Amyloid can produce increased LV and RV wall thickness, small cavities, thickened valves and interatrial septum, biatrial enlargement, effusion, very low tissue velocities, and reduced GLS with relative apical sparing. Apical sparing is supportive, not diagnostic. Endomyocardial fibrosis or hypereosinophilic disease may cause apical obliteration, thrombus, and AV-valve tethering. Sarcoidosis, hemochromatosis, radiation, storage disease, and idiopathic RCM may look different or even dilated. Constrictive pericarditis can mimic restriction; marked respiratory inflow variation, septal shift, preserved or increased medial e′, and annulus reversus favor constriction, but an incomplete sign set should remain indeterminate.

Examine the arrhythmogenic phenotype systematically

Arrhythmogenic cardiomyopathy is not confined to a visibly enlarged RV. It can be right-dominant, biventricular, or left-dominant, and early disease may have a normal echocardiogram. Obtain a nonforeshortened RV-focused apical four-chamber view plus parasternal long-axis RV inflow, parasternal short-axis RVOT, and subcostal views. Measure RV basal and mid diameters, longitudinal length, RVOT in standardized planes, end-diastolic and end-systolic area, fractional area change, TAPSE, tissue Doppler S′, and RV free-wall strain when feasible. Three-dimensional RV volumes and EF add global assessment when image quality is adequate.

Look for regional akinesia, dyskinesia, aneurysm, systolic bulging, disproportionate RVOT enlargement, reduced global function, and RA dilation. Confirm any small bulge in orthogonal cine loops; near-field dropout, rib artifact, moderator band, tethering, pectus anatomy, and off-axis imaging create false regional abnormalities. Exclude pulmonary hypertension, important TR, shunt, RV infarction, myocarditis, congenital repair, and endurance-athlete remodeling. Do not diagnose arrhythmogenic cardiomyopathy from one RV dimension, one strain segment, or apparent fat. Current diagnosis integrates quantitative imaging with ventricular arrhythmia, ECG depolarization/repolarization, family history, genetics, and CMR tissue characterization.

Recognize stress cardiomyopathy and its complications

Stress cardiomyopathy, often called Takotsubo syndrome, is an acute and usually reversible LV regional systolic phenotype. The classic pattern has apical and midventricular akinesia or dyskinesia with hyperdynamic basal segments, but midventricular, basal or reverse, and focal variants occur. Abnormality commonly crosses a single epicardial coronary distribution, which raises suspicion but does not exclude acute coronary occlusion. Clinical presentation, ECG, biomarkers, coronary evaluation, and often CMR are required to distinguish acute coronary syndrome and myocarditis.

Acquire all standard apical and short-axis levels, contrast unclear borders, and quantify EF without tracing thrombus as myocardium. Inspect the apex for spontaneous contrast or thrombus and assess RV involvement. Hyperdynamic basal contraction can produce SAM, posterior MR, and dynamic LVOT obstruction; use color and PW to localize, then record a separate CW gradient. Also look for low stroke volume, acute MR, pulmonary pressure elevation, pericardial effusion, and mechanical complications. Avoid inotropes or provocation decisions—the sonographer's role is accurate acquisition and immediate escalation of unstable findings.

Serial imaging is central: improvement or resolution supports a stress phenotype, while persistent regional dysfunction redirects the differential. Compare identical views and quantitative methods rather than relying on visual memory. Communicate apical thrombus, severe LVOTO, shock physiology, severe MR, suspected RV involvement, or new deterioration promptly.

Across all three groups, the final report should state the distribution of abnormal structure and motion; LV and RV volumes and function; atrial remodeling; diastolic and venous findings; GLS or RV strain quality; obstruction, valve disease, thrombus, and pressures; rhythm and loading conditions; prior-study change; and technical limitations. “Findings suggest a restrictive, arrhythmogenic, or stress phenotype” is more defensible than converting a suggestive echo sign into a final etiologic diagnosis.

Verify physiology and measurement quality

Restrictive inflow may be absent early or altered by diuretics, tachycardia, AF, MR, and changing preload. Sample both AV valves and systemic and pulmonary venous flow across visible respiration; discordant left- and right-sided findings should trigger review of rhythm, gain, sweep speed, and beat selection before labeling restriction.

Optimize an arrhythmogenic survey with an RV-focused view, adequate frame rate, stable ECG, complete free-wall strain tracking, and vendor-consistent analysis. A normal TAPSE cannot overrule convincing regional disease, while an abnormal TAPSE alone may reflect loading or translational motion. Combine longitudinal, area-based, deformation, and, when feasible, 3-D evidence. Repeat regional loops at a different depth and transducer position to test whether a suspected aneurysm follows myocardium or artifact.