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 on the other hand 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, as is in our case, the correct diagnosis may be readily suggested from the history or routine diagnostic testing.
Constrictive pericarditis is usually associated with increased thickness of the pericardium with a pericardial thickness exceeding 4 mm being 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 computed tomography (CT), and cardiac magnetic resonance (CMR) imaging. Echocardiography is not reliable in this respect in comparison with the above tools.
PATHOPHYSIOLOGY OF RESPIRATORY EFFECTS — An understanding of ventricular volume constraints and ventricular interaction is key to comprehend 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. The respiratory variation in intrathoracic pressure is transmitted normally to the cardiac chambers.
The different effects of respiration on ventricular filling between the two diseases may be explained by the following mechanisms:
· In patients with constrictive pericarditis, the pulmonary capillary wedge pressure is influenced by the inspiratory fall in intra-thoracic pressure, while the left ventricular pressure is shielded from respiratory pressure variations by the pericardial scar. Thus, inspiration lowers the pulmonary capillary wedge pressure, and presumably left atrial pressure, but not left ventricular diastolic pressure, thereby decreasing the pressure gradient for ventricular filling. The less favorable filling pressure gradient during inspiration explains the decline in filling velocity. Reciprocal changes occur in the velocity of right ventricular filling. These changes are mediated by the ventricular septum, not by increased systemic venous return.
· In patients with restrictive cardiomyopathy, inspiration lowers pulmonary wedge and left ventricular diastolic pressures equally, thereby leaving the pressure gradient for ventricular filling and filling velocity virtually unchanged.
· A lower left ventricular filling pressure gradient with constrictive pericarditis also leads to a delay in mitral valve opening and therefore, a longer isovolumic relaxation time during inspiration. This inspiration decline in the filling gradient is seen in constrictive pericarditis but not restrictive cardiomyopathy.
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 and fluoroscopy may be used also to look for this calcification.
-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 (similar to that seen in cardiac tamponade). Usually a 25% variation is considered significant. 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). Patients with pulmonary disease however have a marked increase in inspiratory superior vena cava systolic flow velocity which was not seen in those with constrictive pericarditis.
· Hepatic venous flow: Measurement of hepatic venous flow can help to distinguish constrictive pericarditis from restrictive cardiomyopathy. 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.
· Doppler tissue velocity: The early diastolic Doppler tissue velocity at the mitral annulus (E') is decreased (<8 cm/sec) in restrictive cardiomyopathy, due to an intrinsic decrease in myocardial contraction and relaxation. In contrast, the transmitral E' is frequently increased (>12 cm/sec) in constrictive pericarditis, since the longitudinal movement of the myocardium is enhanced because of constricted radial motion.
Unlike in normal individuals, mitral lateral (and tricuspid) annular E' velocities are often relatively reduced in patients with constrictive pericarditis ("annular reversus"). This reduction may be the result of lateral adhesion of the pericardium while the longitudinal movement of the septal annulus is unimpeded. These mechanics are not evident in restrictive cardiomyopathy. Thus, the ratio between lateral (both mitral and tricuspid) and septal annuli velocities is reduced in patients with constrictive pericarditis compared with that in patients with restrictive cardiomyopathy (and controls) and may be useful to discriminate these groups of patients. (see figures 3,4 and 5). In a study of 37 patients with constrictive pericarditis, 35 patients with restrictive cardiomyopathy (the majority with amyloidosis) and 70 normal controls, the lateral E'/septal E' ratios were 0.94 ± 0.17, 1.35 ± 0.31, and 1.36 ± 0.24, respectively (ref 2).
· Regional longitudinal strains measured with STE may avoid the limitations of tissue Doppler annular velocities when patients have a thickened annulus. The ratios of LV free wall systolic strain/septal wall systolic strain and RV free wall strain/septal strain were significantly lower in 52 patients with constrictive pericarditis (0.8 ± 0.2, 0.8 ± 0.4) than in 35 patients with restrictive cardiomyopathy (1.1 ± 0.2, 1.4 ± 0.5) and 26 control subjects (1.0 ± 0.2, 1.2 ± 0.2). The strain ratios were more robust than the ratio of annular tissue velocities. In patients with constrictive pericarditis, the regional myocardial mechanics significantly correlated with regional pericardial thickness and improved after pericardiectomy (ref. 4).
1. Annulus paradoxus: transmitral flow velocity to mitral annular velocity ratio is inversely proportional to pulmonary capillary wedge pressure in patients with constrictive pericarditis. Ha JW, Oh JK, Ling LH, Nishimura RA, Seward JB, Tajik AJ. Circulation. 2001; 104(9):976
2. Comparison of mitral inflow and superior vena cava Doppler velocities in chronic obstructive pulmonary disease and constrictive pericarditis. Boonyaratavej S, Oh JK, Tajik AJ, Appleton CP, Seward JB. J Am Coll Cardiol. 1998;32(7):2043
3. Constrictive pericarditis in the modern era: novel criteria for diagnosis in the cardiac catheterization laboratory. Talreja DR, Nishimura RA, Oh JK, Holmes DR. J Am Coll Cardiol. 2008; 51(3):315
4. Biventricular mechanics in constrictive pericarditis comparison with restrictive cardiomyopathy and impact of pericardiectomy. Kusunose K, Dahiya A, PopovićZB, Motoki H, Alraies MC, Zurick AO, Bolen MA, Kwon DH, Flamm SD, Klein AL. Circ Cardiovasc Imaging. 2013; 6 (3):399.