Pathophysiology and Diagnosis of Constrictive Pericarditis

Constrictive pericarditis (CP) is a relatively uncommon form of clinical heart failure. The true population prevalence is unknown, but amongst those with viral pericarditis it has been estimated to occur in less than 0.5% of cases.1 However, because it is potentially reversible, the diagnosis must not be missed. Surgical pericardiectomy has the ability to "cure" CP, with dramatic improvements in symptoms and quality of life.2,3 Although the etiology of CP can be varied (idiopathic, post viral, tuberculous, post-surgical, radiation-induced, etc.), the final common pathway is development of fibrous thickening or calcification of the pericardium resulting in pericardial non-compliance.

Pericardial physiology and pathophysiology in constriction:

The normal pericardium minimally impedes ventricular distensibility at normal cardiac operating volumes. In CP, pericardial non-compliance creates a stiff ventricular-pericardial unit, leading to increased diastolic pressures and more rapid rise in ventricular pressures for a given venous return. The noncompliant pericardium limits ventricular relaxation and determines ventricular diastolic pressure, resulting in elevated, equalized diastolic pressures in all chambers. Clinically, this presents predominantly as right-sided congestion (jugular venous distention, edema, and ascites). Elevation in pulmonary capillary wedge pressure and a decreased cardiac output response to exercise (given inadequate ventricular filling) results in dyspnea and effort intolerance, although frank pulmonary edema is less common than typical systolic heart failure.

The normal pericardium regulates coupling of left- and right-sided stroke volumes during acute changes in preload, such that a sudden increase in right-sided venous return (during inspiration) is associated with leftward septal bowing and a decrease in left ventricular (LV) transmural filling pressure (LV diastolic pressure – pericardial pressure). This in turn decreases the LV end diastolic volume (LV preload) and therefore left-sided stroke volume.4 In the normal heart, these changes in stroke volume with respiration are minimal. Given a fixed pericardial volume in CP, pericardial coupling is greatly exaggerated, leading to dramatic ventricular interdependence. Abnormal ventricular septal motion results from enhanced respirophasic alterations in left- and right-sided stroke volume.

In CP, due to the heart being encased by a noncompliant pericardium, the normal inspiratory decrease in intrathoracic pressure is not transmitted to intracardiac pressures. This effect amplifies inspiratory decreases in pulmonary venous pressure (since pulmonary veins are primarily extrapericardial), translating to a reduced left-sided inspiratory preload, further reducing left-sided inspiratory stroke volume. Multimodality diagnostic evaluation of CP highlights these findings, facilitating the diagnosis.

Initial assessment:

The low prevalence of CP makes identifying key physical examination and historical features an important initial step in the diagnostic process. A history of cardiac surgery, radiation or tuberculosis should heighten clinical suspicion in the presence of edema, abdominal distention and exertional dyspnea. Elevated jugular venous pressure (JVP) is present in virtually all patients that are not hypovolemic. Pericardial constraint results in the inability of the right heart to accommodate inspiratory abdominal venous return, translating to an inspiratory increase in the JVP (Kussmaul's sign).5 The jugular x and y descents are prominent in CP, due to exaggerated longitudinal annular motion and prominent early ventricular filling, respectively. In contrast, restrictive cardiomyopathy demonstrates blunting of the x descent, due to impaired atrial relaxation and atrial myopathy. Auscultation may disclose a high pitched pericardial knock along the left sternal border. Ascites and significant lower edema are common and often lead to the misdiagnosis of liver disease if the JVP findings are not recognized.

Laboratory testing in CP is nonspecific. A high BNP can suggest a greater likelihood of restrictive cardiomyopathy, but studies have shown great overlap in diagnostic values in this population limiting clinical utility.6-9

Echocardiography:

As an initial diagnostic test, echocardiography can confirm the diagnosis of CP in most cases if pre-test probability is sufficiently high.10 Echocardiography demonstrates features of both exaggerated ventricular interdependence and intrathoracic-intracardiac dissociation. The pathognomonic finding is respirophasic septal shifting, detected by either M mode or 2D imaging.5 In addition to this exaggerated respiratory septal motion, there is also an abnormal beat-to-beat septal motion, or "shudder," due to differential rapid early diastolic filling of the right and then left ventricle.11 The inferior vena cava is universally plethoric in the absence of hypovolemia; a sensitive but nonspecific feature of CP. Expiratory hepatic vein reversals and decreased diastolic forward flow occur due to rightward ventricular septal motion from an expiratory increase in LV preload, with a resultant decrease in effective operating right ventricular compliance.

The exaggerated respiratory preload changes are also exemplified by an inspiratory decrease in mitral valve inflow Doppler and an increase in tricuspid valve inflow Doppler. However, these findings are insensitive. In the presence of significantly increased left atrial and pulmonary capillary wedge pressures, the decrease in wedge pressure-LV gradient with inspiration is insufficient to change LV preload enough to alter mitral inflow Doppler magnitude.12 Because of lateral wall tethering, the lateral mitral annulus early diastolic tissue Doppler velocity (e') is often decreased and abnormally lower than the medial e' velocity (annulus reversus).13 In contrast to cardiomyopathic causes of heart failure, the medial e' velocity is relatively normal (or even increased, termed annulus paradoxus) given normal myocardial relaxation and compensatory medial annular longitudinal motion in the setting of lateral wall tethering.14,15

Cardiac radiology:

In CP, chest x-rays can demonstrate pericardial calcification, a pathognomonic finding in the presence of clinical heart failure and elevated JVP. Chest CT is more sensitive for pericardial calcification than chest x-ray.16 Chest CT and MRI allow for precise measurement of pericardial thickness, with MRI in particular demonstrating excellent accuracy (93%) in detection of pericardial thickening >4 mm.17 However, it is important to remember that up to 18% of cases of surgically confirmed CP can have normal pericardial thickness despite pathological noncompliance.18 Pericardial tethering, which can be visualized via echocardiography, CT, or MRI may also provide insight into the presence of CP. MRI imparts information about active pericardial inflammation, which can help guide therapeutic decisions. Furthermore, cardiac MRI provides unique myocardial assessment, which may identify cardiomyopathic processes when the diagnosis is uncertain. Myocardial delayed enhancement is typically absent in isolated CP, but can occur in nearly one-third of cases with restrictive cardiomyopathy.19

Unlike echocardiography, cardiac CT and MRI are not dependent upon patient habitus and can provide better cardiac visualization when echocardiographic imaging is suboptimal. Respirophasic shifts in septal motion are well demonstrated on both CT and MRI. In addition, CT and MRI may provide information on alternative causes of dyspnea such as lung disease or diaphragmatic paralysis.

Diagnosis beyond cardiac imaging:

Cardiac catheterization remains the gold standard diagnostic test, if non-invasive testing is inconclusive, to assess for presence of constriction and evaluate hemodynamic significance. While most patients with CP do not require hemodynamic catheterization for diagnosis, one subgroup of particular concern is patients with radiation heart disease, in whom it is often difficult to identify the degree of underlying restrictive cardiomyopathy, even if constrictive features are present. Even with high quality echocardiography and cardiac radiology, these patients may require invasive hemodynamic catheterization to assess elevation in filling pressures with diastolic equalization, ventricular interdependence and intrathoracic-intracardiac dissociation.2

Treatment:

Once CP is identified, medical treatment with diuresis is often only partially effective at palliating symptoms. If there is extensive pericardial inflammation, a trial of anti-inflammatory therapy is warranted to assess for reversibility prior to proceeding with pericardiectomy. Some patients can have improvement in pericardial compliance if they have only transient constriction from inflammation.20 Surgical complete pericardiectomy is indicated to relieve symptoms in patients with CP. Using a multimodality diagnostic approach (Figure 1), it is now uncommon for patients to proceed to the operating room for confirmation of CP. Given the often transformative nature of pericardiectomy for patients' quality of life, clinicians must continue to maintain a high index of suspicion for this rare but curable form of heart failure.

Figure 1

Figure 1

References

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  13. Reuss CS, Wilansky SM, Lester SJ, et al. Using mitral 'annulus reversus' to diagnose constrictive pericarditis. Eur J Echocardiogr 2009;10:372-5.
  14. Ha JW, Oh JK, Ling LH, Nishimura RA, Seward JB, Tajik AJ. Annulus paradoxus: transmitral flow velocity to mitral annular velocity ratio is inversely proportional to pulmonary capillary wedge pressure in patients with constrictive pericarditis. Circulation 2001;104:976-8.
  15. Ha JW, Ommen SR, Tajik AJ, et al. Differentiation of constrictive pericarditis from restrictive cardiomyopathy using mitral annular velocity by tissue Doppler echocardiography. Am J Cardiol 2004;94:316-9.
  16. Ling LH, Oh JK, Breen JF, et al. Calcific constrictive pericarditis: is it still with us? Ann Intern Med 2000;132:444-50.
  17. Masui T, Finck S, Higgins CB. Constrictive pericarditis and restrictive cardiomyopathy: evaluation with MR imaging. Radiology 1992;182:369-73.
  18. Talreja DR, Edwards WD, Danielson GK, et al. Constrictive pericarditis in 26 patients with histologically normal pericardial thickness. Circulation 2003;108:1852-7.
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Clinical Topics: Cardiac Surgery, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Pericardial Disease, Cardiac Surgery and Heart Failure, Acute Heart Failure, Chronic Heart Failure, Interventions and Imaging, Computed Tomography, Echocardiography/Ultrasound, Nuclear Imaging

Keywords: Blood Pressure, Cardiac Catheterization, Cardiomyopathy, Restrictive, Diagnostic Errors, Diagnostic Tests, Routine, Diuresis, Dyspnea, Echocardiography, Edema, Heart Failure, Systolic, Heart Ventricles, Hepatic Veins, Hypovolemia, Mitral Valve, Pericardiectomy, Pericarditis, Constrictive, Pericardium, Pulmonary Edema, Pulmonary Veins, Pulmonary Wedge Pressure, Tricuspid Valve, Tomography, X-Ray Computed, Vena Cava, Inferior, Venous Pressure, Ventricular Pressure, X-Rays


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