Constrictive pericarditis (CP) is an uncommon entity predominantly manifesting as right-sided heart failure resulting from a fixed, thickened, fibrotic pericardium and subsequently impaired ventricular filling [1]. Most cases are idiopathic or iatrogenic following cardiac surgery; however, tuberculosis remains the leading cause in developing countries. Other etiologies include connective tissue disease, radiation, malignancy, or uremia [1, 2].

The pericardium, even healthy and non-diseased, contributes substantially to diastolic ventricular interdependence, a phenomenon in which the filling of one ventricle affects the compliance and geometry of the other ventricle [3]. An exaggerated inspiratory fall of systolic blood pressure of greater than 10 mmHg, or pulsus paradoxus, can be seen in various conditions including CP, asthmatic exacerbation, right ventricular infarction, and pulmonary embolism [4, 5]. A dissociation of the intrathoracic and intracardiac pressures due to pericardial constraint leads to pooling of blood in the pulmonary vasculature and loss of pressure gradient with subsequent underfilling of the left ventricle (LV) during inspiration. LV underfilling is exacerbated by the filling of right ventricle (RV) and a resultant leftward septal shift [4].

TTE is usually an initial imaging study of choice for a diagnosis of CP, although not without limitation. Pericardial thickness is often not easily measured by TTE [6]. Image quality can also be limited by body habitus, lung disease, and intervening air space after cardiac surgery. Despite optimal image quality, TTE results from our patient were inconclusive. Evidence of ventricular interdependence, respirophasic variation in septal shift and mitral inflow velocities, was absent in our patient. The lack of interdependence may be explained by hemodynamic changes associated with AR with resultant elevated left ventricular filling pressures and dampening of the effect from respiratory variation [5]. Though, it is possible that the constrictive process may not be uniform, thus classic hemodynamic hallmarks may not always be present.

Owing to its high spatial and temporal resolution, cine CMR provides excellent anatomic detail and tissue characterization, in addition to functional evaluation of the hemodynamics associated with CP [7]. It has proven to be an excellent non-invasive modality for the diagnosis CP given its excellent sensitivity and specificity. To rule out right ventricular failure, a condition sharing similar clinical presentation with CP, the use of cine CMR with steady-state free precession (SSFP) is the gold standard to quantify cardiac volume and ejection fraction of both ventricles [7].

In a retrospective cohort study of patients with surgically-proven CP, a model incorporating both relative interventricular septal excursion and pericardial thickness (≥ 3 mm) exhibited 100% sensitivity and 90% specificity in diagnosing CP [8]. Other parameters include diastolic septal bounce and eccentricity index, both of which are a manifestation of ventricular interdependence [8].

Tagged cine CMR, which utilizes SPAMM, is a useful tool to evaluate fibrotic adhesion of pericardial layers [9]. In normal pericardium, the shear motion between pericardial layers leads to the displacement of tag continuity [7]. The persistent continuity of tagged signals between the pericardium and myocardium throughout cardiac cycles signifies an adhesion to the myocardium as seen in our patient [9].

The presence and extent of pericardial inflammation and fibrosis can be readily assessed with the use of gadolinium [1]. It was shown by a small pilot study that the presence of LGE was associated with reversibility and positive response to anti-inflammatory therapy [10]. The presence of myocardial LGE, which can be seen in myopericarditis or restrictive cardiomyopathy (RCM) is associated with worse outcomes. It is of paramount importance to differentiate CP from RCM as the treatment strategies are vastly different [7]. Although biatrial enlargement is a common finding in both CP and RCM, the relative atrial volume ratio, as defined by the left atrial volume divided by right atrial volume, may help differentiate CP from RCM with sensitivity of 82.6% and specificity of 86.4% using a cut-off value of > 1.32 [11].

CMR was integral in confirming the diagnosis of CP for this patient whose echocardiographic findings were inconclusive. It clearly characterized a thickened pericardium with LGE and evidence of tethering on tagged images. Additionally, the severity of AR was also quantified, and a loculated pericardial effusion was identified. The location and extent of pericardial fluid is easily assessed by CMR. It was previously suggested that effusive-constrictive pericarditis is likely an evolution of acute pericarditis progressing to eventual chronic constrictive pericarditis without effusion [12].