ESSENTIALS OF DIAGNOSIS
Predominant biventricular diastolic dysfunction with lesser impairment of systolic performance.
Echocardiography: small stiff ventricles, preserved systolic function (until late stages), dilated atria, and diastolic dysfunction by Doppler.
Many disorders manifest restrictive “physiology” and must be excluded (eg, hypertrophic cardiomyopathy and constrictive pericarditis).
Cardiac magnetic resonance imaging powerful: delineates myocardial infiltration, inflammation, and fibrosis and assesses pericardium, thereby helping establish underlying disorder.
Tissue biopsy may be necessary for definitive diagnosis in some disorders (eg, amyloidosis).
Restrictive cardiomyopathies (RCM) are indolent disabling diseases resulting from pathophysiologic processes that induce predominant diastolic chamber dysfunction with lesser impairment of systolic performance. RCM is characterized by small stiff ventricles with progressive impairment of diastolic filling, leading to the hemodynamic conundrum of low preload but high filling pressures (Figure 24–1). This pattern of diastolic dysfunction leads to dilated atria and elevated mean atrial pressures, resulting clinically in biventricular “backward failure” manifest as pulmonary venous congestion (dyspnea) as well as systemic venous pressure elevation (peripheral edema). Systolic function is preserved in most cases, depending on the underlying cause (at least in the presenting stages of most of the underlying diseases). However, despite intact systolic function, the restrictive constraints on true ventricular preload limit stroke volume, thereby resulting in low cardiac output (fatigue) and ultimately hypoperfusion.
Pathophysiology of restrictive cardiomyopathy (RCM). CO, cardiac output; LA, left atrium; RA, right atrium; SOB, shortness of breath; SV, stroke volume.
The abnormal diastolic properties of the ventricle are typically attributable to abnormalities of the myocardium (hypertrophy, infiltration, inflammation, or fibrosis) or the endomyocardial surface (inflammation and scarring). RCM classification (Figure 24–2) may be most easily considered based on underlying pathophysiologic process as: (1) hypertrophic (eg, hypertension, aortic stenosis); (2) deposition, including both infiltrative diseases (eg, amyloidosis) and storage disorders (eg, hemochromatosis); (3) inflammatory (eg, hypereosinophilic syndrome); and (4) primary or idiopathic, including diabetes. It is important to consider the general perception of the “typical” RCM versus the clinical reality; that is, the term RCM tends to conjure cardiac amyloidosis, an infiltrative disease inducing “classic” and dramatic clinical manifestations of RCM. Certainly, identification of specific infiltrative and storage diseases may have important prognostic and therapeutic implications. However, far more prevalent is restrictive “physiology,” which most commonly results from hypertrophic states typically seen in patients with advanced hypertension and the elderly (and in more complex forms in cases with aortic stenosis). Such “restrictive physiology” induces clinical manifestations similar and often indistinguishable from other “classic” forms of RCM.
Classification of restrictive cardiomyopathies. HOCM, hypertrophic obstructive cardiomyopathy.