Evaluation of constrictive pericarditis in conventional modalities requires high-quality imaging of the pericardium. Echocardiography has a well-defined limited ability to delineate the anatomic features of the pericardium. Although the posterior wall is often seen to be thick, it is due to a far-field artifact, generating a hyperechoic signal, often mimicking a thickened, highly calcified pericardium. Pulse-wave Doppler techniques demonstrating evidence of a restrictive pattern, as well as an abnormal tissue Doppler signal with an exaggerated “e” and blunted “a” wave are helpful in the evaluating the presence of constricted physiology. When a respirometer is available, the perturbed physiology can be evaluated more accurately, whereupon inspiration and expiration produce a characteristic Doppler pattern that can aid in diagnosis. In the catheterization suite, reliance on a morphologic “square root sign” is the cardinal feature. When fluid boluses are given, the specificity is increased, but still is far from diagnostic in many cases. A technique that has received some popularity in the catheterization suite is using the concept of “ventricular interdependence” in which during inspiration and expiration there is a characteristic separation in contraction of right and left atrial pressures. This can be a cumbersome technique, and requires invasive instrumentation to make this diagnosis, but in expert hands has high accuracy. Because physical examination, although helpful, has very limited sensitivity and specificity and is chiefly detected by a most subtle pericardial knock, is often not present until middle stages of disease, requiring an astute clinician and high clinical suspicion, there exists a great need for a technique that is both noninvasive, easy-to-use, and near foolproof. It is important to note that the ability to accurately detect constricted pericarditis has tremendous upside and downside potential (see Fig. 16-1). In these patients, who often present late, with months to years of vague progressive indolent symptoms that culminate in severe right heart failure, the accurate diagnosis leads to median sternotomy and pericardial stripping with dramatic improvement in the patient’s symptomatology (see Fig. 16-2). However, in the same setting, with the patient in extremis, an incorrect diagnosis can lead to needless open-heart surgery. Consider the following hypothetical conversation with the cardiothoracic surgeon, in whom you have misdiagnosed constriction in a patient, “Would you please come down to the operating room to show me where you think I should cut the pericardium. By the way, would you mind telling the patient why I needlessly opened this patient up?” When stated in this graphic manner, it is clear that a versatile technique, such as CMR, would be advantageous (see Fig. 16-3).

The technique of radiofrequency tissue tagging, in which saturated lines of magnetization are placed in
either a radial or gridlike pattern across the myocardium noninvasively, is useful in assessing pericardial disease. Typically, radiofrequency tagging is used to determine myocardial contraction patterns, and has been well described by us and others to provide knowledge of segmental myocardial deformation and measurement of strain in a transmural manner across the myocardium. This has been used to evaluate the post-myocardial infarction (MI) remodeling process and assess the effects of myocardial performance before and after surgical intervention. Measurement of circumferential, longitudinal, and radial strain patterns in one, two, and three dimensions has been performed, detailing high-fidelity physiologic patterns of normal and deranged
physiology. However, the clinical applicability is only now becoming recognized for quantitation of myocardial mechanics using this technique. An offshoot of this technology has been applied to evaluation of constrictive pericarditis in which tissue tagging has proved to be a robust and clinically applicable technique. The grid pattern is placed over the entire field of view (FOV), which includes the myocardium and pericardium by definition, and allows separation of pericardial signal from myocardial signal. Except for bulk translation, the pericardial signal is fixed in healthy individuals; therefore the epicardial signal should “slide” past the pericardial surface during systolic contraction and diastolic relaxation. Therefore, the visceral surface of the pericardium (epicardium) should migrate past the stationary parietal pericardium. Failure to see slippage between the visceral and parietal pericardium, evidenced by lack of relative motion, is diagnostic of adherence between the two layers. The observation of a fixed or grid pattern, without slippage, demonstrates that there is fibrosis, scarring, or union between the parietal and visceral pleura. This observation is the sine qua non of constrictive pericarditis (see Fig. 16-4). In our practice, in which we see sliding between the two pericardial layers, despite evidence by echocardiography or catheterization suite of constriction, we are confident in assuring the surgeon that there is no reason to take the patient to surgery. On the other hand, despite absence of constriction by other imaging modalities including the presence of a thin pericardium on computed tomography (CT), if there is no slippage in the major portion of the pericardium by CMR, we can assure the surgeon
that they will find an adherence pattern consistent with constrictive pericarditis upon opening the chest. In our series of more than 50 patients, we have never been incorrect.