C34 AN UNUSUAL CASE OF CARDIAC ARREST DUE TO TRAUMA–INDUCED QT PROLONGATION

Abstract

Abstract Background QT prolongation is a well–known cause of sudden cardiac death due to polymorphic ventricular tachycardia triggered by early afterdepolarizations. Acquired long QT is a common finding in several clinical scenarios and invariably represents a high risk feature. Case Report An 84 years–old woman presented to our emergency department (ED) after experiencing a blunt chest trauma due to a car accident. She reported mild dyspnea and chest pain exacerbated by breathing and movement while denied palpitations and loss of consciousness. Baseline ECG showed atrial fibrillation with normal ventricular rate and a prolonged QT interval (QTc 640, Fig 1A) not present at previous ECGs. She did not assume any QT–prolonging drug and laboratory tests at admittance revealed troponin I values slightly elevated (29,6 ng/ml; n.v.: <11,6 ng/l) and no other significant abnormalities. A CT scan demonstrated a displaced fracture of the sternal body. Due to the QT prolongation, the patient was admitted for ECG monitoring.. During the stay in our ED the patient suffered a cardiac arrest. A torsade des pointes triggered by a late–coupled premature ventricular complex (PVC) was documented (Fig 1B). The arrhythmia was interrupted with external DC shock and magnesium solfate infusion was started. The coronary angiography demonstrated normal coronary arteries. The patient underwent cardiac magnetic resonance (CMR) four days later which showed transmural necrosis of the middle third of the lateral wall of the left ventricle at the insertion of the anterolateral papillary muscle (Fig 2). No further ventricular arrhythmias were observed and the patient was discharged after QTc normalization. Cardiac arrhythmias are a rare complication of cardiac contusion ranging from isolated PVCs to atrial or ventricular fibrillation. However, the role of the ECG in this peculiar subset is unclear. The most common ECG abnormalities are non specific ST–T wave changes, whereas in our case the marked QTc prolongation resulted in a closer monitoring of the patient allowing a prompt recognition of cardiac arrest. On the other hand CMR proved to be an effective method to identify a cardiac injury showing the typical pattern of myocardial damage associated with cardiac contusion (stress–induced lesions at the insertions of papillary muscles due to sudden increase of left ventricular pressure) and, thus, could be adopted as a useful tool to identify patients at higher risk for arrhythmic complications.