Differentiating constrictive pericarditis and restrictive cardiomyopathy INTRODUCTION — Constrictive pericarditis is the result of scarring and consequent loss of the normal elasticity of the pericardial sac. This leads to impairment of ventricular filling in mid and late diastole. As a result, the majority of ventricular filling occurs rapidly in early diastole and the ventricular volume does not increase after the end of the early filling period. Restrictive cardiomyopathy is characterized by a nondilated rigid ventricle, resulting in severe diastolic dysfunction and restrictive filling that produces hemodynamic changes similar to those in constrictive pericarditis. Constrictive pericarditis and restrictive cardiomyopathy both lead to diastolic heart failure with normal (or near normal) systolic function, and characteristically abnormal ventricular filling that results in similar clinical and hemodynamic features. However, because of their markedly different treatments, differentiating between the two conditions is critical. In some patients, the correct diagnosis may be readily suggested from the history or routine diagnostic testing. In others, however, this differentiation cannot be diagnosed before biopsy or even surgical exploration. PATHOPHYSIOLOGY OF RESPIRATORY EFFECTS — An understanding of ventricular volume constraints and ventricular interaction is key in any discussion of the hemodynamic differences between constrictive pericarditis and restrictive cardiomyopathy. In patients with constrictive pericarditis, total cardiac volume is fixed by the noncompliant pericardium. The septum is not involved and can therefore bulge toward the left ventricle when left ventricular volume is less than that on the right. As a result, ventricular interdependence is greatly enhanced. This bulging may be seen on echocardiography, or in some cases, on cardiac magnetic resonance imaging . In addition, changes in intrathoracic pressure are not transmitted to the cardiac chambers because of obliteration of the pericardial space. In restrictive cardiomyopathy, on the other hand, pericardial compliance is normal. Left ventricular systolic function is normal, or in severe cases, may even be reduced. The respiratory variation in intrathoracic pressure is transmitted normally to the cardiac chambers I HISTORY AND PHYSICAL EXAMINATION — History — In the evaluation of constrictive pericarditis versus restrictive cardiomyopathy, the history is most valuable in identifying a systemic disorder which can predispose to either constrictive pericarditis or restrictive cardiomyopathy: A prior history of pericarditis, trauma, cardiac surgery, or a systemic disease that affects the pericardium (eg, tuberculosis, connective tissue disease, malignancy) makes the diagnosis of constrictive pericarditis more likely. A history of an infiltrative disease that may involve the heart muscle (eg, amyloidosis, sarcoidosis) favors the diagnosis of restrictive cardiomyopathy. However, prior thoracic radiation treatment (and rarely amyloidosis) can result in either constrictive pericarditis, restrictive cardiomyopathy, or a condition with features of both constrictive pericarditis and restrictive cardiomyopathy. Physical examination — The vast majority of patients with both constrictive pericarditis and restrictive cardiomyopathy display elevated jugular venous pressure (JVP) on physical examination . From the JVP waveform alone, it is not possible to distinguish between constrictive pericarditis, restrictive cardiomyopathy, tricuspid regurgitation with an enlarged compliant right atrium, or right heart failure (eg, due to right ventricular infarction or pulmonary hypertension). The contour of the jugular venous pulse in all these conditions is dominated by a deep, steep Y descent. Additional physical examination findings in patients with constrictive pericarditis or restrictive cardiomyopathy can include: Kussmauls sign (the lack of an inspiratory decline in JVP) Pulsus paradoxus (uncommon) Peripheral edema Ascites and hepatomegaly Pleural effusions. Approximately 50 percent of patients with constrictive pericarditis may present with a pericardial knock (an accentuated heart sound occurring slightly earlier than a third heart sound, which may be audible and rarely is palpable), which is not expected in restrictive cardiomyopathy . Conversely, an audible S3 is frequently present in persons with restrictive cardiomyopathy because of the abrupt cessation of the rapid ventricular filling; this is not usually present in constrictive pericarditis. NON-INVASIVE TESTING — Electrocardiogram — Depolarization abnormalities (such as bundle branch block), ventricular hypertrophy, pathologic Q waves, or impaired atrioventricular conduction strongly favor restrictive cardiomyopathy. Low voltage and isolated repolarization abnormalities can occur in both conditions, although the latter are more common in constrictive pericarditis. Atrial fibrillation is common in the late stages of both diseases. Plasma BNP — Plasma concentrations of B type natriuretic peptide (BNP) are increased in numerous conditions, most notably in patients with left ventricular dysfunction. As a result, plasma BNP has been used in the diagnosis of dyspnea and to assess the efficacy of therapy and estimate prognosis in patients with heart failure. BNP is released in response to left ventricular dysfunction and wall stretch. Wall stretch is increased in restrictive cardiomyopathy. However, in constrictive pericarditis, the myocardium is normal, and stretch is limited by the thickened pericardium. These physiologic differences suggest that measurement of plasma BNP might have value in distinguishing between these two disorders. Chest x-ray — Calcification of the pericardium strongly suggests constrictive pericarditis, but it can also be seen in other conditions, such as asbestosis, which may or may not be associated with constrictive pericarditis . However, the absence of calcification is equally compatible with either diagnosis. Mild cardiomegaly on chest x-ray is common in both conditions, but more prominent in restrictive cardiomyopathy. This is generally due to atrial rather than ventricular enlargement. Pulmonary venous congestion with or without pleural effusions can be seen in restrictive cardiomyopathy but would not be expected in constrictive pericarditis. Pericardial imaging: constrictive pericarditis is usually associated with increased thickness of the pericardium (im. A pericardial thickness exceeding 4 mm is highly suggestive of constrictive pericarditis. However, constrictive pericarditis can also occur in the setting of a non-thickened pericardium. Pericardial thickness can be evaluated using a variety of imaging techniques, including echocardiography, computed tomography (CT), and cardiac magnetic resonance (CMR) imaging. While transthoracic echocardiography is the most frequently imaging modality used in the assessment of suspected pericardial disease, it is also one of the least sensitive for detecting pericardial thickening. In comparison to transthoracic echocardiography, CT and CMR imaging are more sensitive for the detection of increased pericardial thickness. Doppler echocardiography — In addition to its role in evaluating pericardial thickness, transthoracic echocardiography allows for Doppler assessment of hemodynamics, thereby providing significant information that can aid in diagnosing (and differentiating) constrictive pericarditis and restrictive cardiomyopathy. Restrictive cardiomyopathy and constrictive pericarditis share many important hemodynamic characteristics and therefore, have a number of Doppler characteristics in common, most notably a restrictive mitral inflow or ventricular filling pattern (measured as mitral E velocity), with striking E dominance and a short deceleration time . These findings indicate early rapid filling and are seen in both entities. However, Doppler echocardiography can also provide clues to differentiating constrictive pericarditis and restrictive cardiomyopathy: Respirophasic changes in intrathoracic pressure and ventricular filling — The respiratory variation in ventricular filling velocity in restrictive cardiomyopathy is usually minimal (less than 10 percent), while patients with constrictive pericarditis may have respiratory variations as high as 30 to 40 percent in ventricular filling velocity . However, the ventricular filling velocity is highly influenced by the level of the left atrial pressure. When left atrial pressure is greatly elevated in a patient with constrictive pericarditis, respiratory variation in ventricular filling may not be observed, whereas patients with lower left atrial pressure (ie, due to volume depletion or earlier stage of disease) may have more noticeable changes in ventricular filling velocities with respiration. Left atrial pressure can be reduced on physical examination by asking a patient to move from the supine to seated position; such a maneuver may elicit the abnormality . Respiratory variation in mitral E velocity, as with pulsus paradoxus on physical examination, is not specific to constrictive pericarditis and is frequently seen in patients with chronic obstructive pulmonary disease (COPD). In an attempt to distinguish between constrictive pericarditis and COPD, the pulsed-wave Doppler recordings of mitral and superior vena cava flow velocities were compared . The patients with pulmonary disease had a marked increase in inspiratory superior vena cava systolic flow velocity which was not seen in those with constrictive pericarditis. Hepatic venous flow — In patients with constrictive pericarditis, there is a reversal of forward flow during expiration, since the right ventricle becomes less compliant as the left ventricle fills more. In contrast, reversal of hepatic vein flow occurs during inspiration in restrictive cardiomyopathy. Color M mode transit time — Color M mode Doppler shows an excessively rapid transit of blood flow from the mitral orifice to the apex in constrictive pericarditis, whereas the transit is much slower than normal in restrictive cardiomyopathy. Tissue Doppler imaging — The early diastolic Doppler tissue velocity at the mitral annulus (E) is decreased (
Posted on: Sat, 08 Nov 2014 20:33:22 +0000
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