5.1. Imaging Modalities
Initial non-specific investigations such as ECG (electrocardiogram) and CXR (chest x-ray) serve as preliminary tools in the diagnostic workup of CaHD. The ECG might reveal low-voltage QRS complexes more frequently in CaHD patients than in those without the disease, alongside non-specific ST-T changes, PR prolongation and sinus tachycardia, hinting at the underlying cardiac involvement.20 Conversely, CXR may show an enlarged cardiothoracic ratio, indicative of cardiomegaly, primarily due to right-sided chamber enlargement, although these findings are not sensitive or specific to CaHD.21
Ultimately, transthoracic echocardiography is most commonly used in the diagnosis of CaHD, offering more tangible insights into the valvular and subvalvular apparatus affected by the disease. Echocardiographic hallmarks of CaHD include thickening and reduced mobility of the tricuspid and pulmonary valve leaflets, leading to regurgitation and stenosis.22 A distinctive ”dagger-shaped” continuous-wave Doppler profile is emblematic of severe tricuspid regurgitation, illustrating the equalisation of right atrial and ventricular pressures23. Such echocardiographic features are pathognomonic, especially in the absence of exposure to appetite suppressants or ergot-derived agents that could mimic similar valvular abnormalities. The echocardiographic evaluation should encompass multiple views of each valve, especially the tricuspid valve visualised through various echocardiographic windows, to ensure a comprehensive assessment.16 The right atrium and ventricle typically exhibit enlargement due to volume overload, with paradoxical motion of the interventricular septum observable in advanced stages.15 Despite these significant structural changes, right ventricular function often remains preserved until the late disease phase.
TOE (Transoesophageal echocardiography) is subsequently recommended if transthoracic echocardiography fails to provide adequate visualisation of the cardiac structures, offering superior images of the valve leaflets and subvalvular apparatus.2 Similarly, cardiac magnetic resonance imaging (MRI) and 64-slice computed tomography (CT) are also used as critical adjuncts, particularly for evaluating the pulmonary valve when echocardiographic visualisation is challenging.24 These modalities excel in providing clear anatomic and functional information, facilitating the assessment of right ventricular function and aiding in the evaluation of myocardial metastases, which although rare, can present as homogenous well-circumscribed masses. Table 3 summarises the advantages, disadvantages, and key notes of primary and secondary imaging modalities employed in diagnosing CaHD.