A 72-year-old man with a history of chronic atrial fibrillation (not on anticoagulation) presents with sudden onset dyspnoea, syncope, and haemodynamic instability (BP 88/56 mmHg, HR 118/min). Bedside echocardiography shows RV dilatation and elevated RV systolic pressure. CTPA is urgently performed and shows a large thrombus in the right main pulmonary artery extending into the lower lobe branch. Additionally, the axial CT images at the level of the right ventricle show marked RV dilatation with the RV/LV diameter ratio >1.0, and the RV free wall is thin and akinetic while the RV apex remains relatively spared. What is the most specific CT finding that indicates haemodynamic compromise in this patient?