Clinical History
An elderly man with several comorbidities including previously treated prostate cancer, diabetes, chronic renal failure and recurrent urinary infections, cardiac and cerebral ischaemic disease, was hospitalised because of an infected diabetic foot.
At admission, previously unknown cardiac arrhythmia with trifascicular atrioventricular block was diagnosed, to be treated with pacemaker positioning.
Imaging Findings
During elective pacemaker (PM) positioning, the attending cardiologist obtains standard venous access at the left subclavian vein, and proceeds with the lead wire under fluoroscopic control to the superior vena cava (SVC), then chooses to interrupt the procedure sensing resistance to advancement from probable venous thrombosis.
Shortly after the procedure, the patient complains of dyspnoea. With stable electrocardiographic findings, further investigation with urgent contrast-enhanced multidetector CT (Figs. 1, 2) is requested. A sizeable hyperattenuating collection of extravasated iodinated contrast medium is contained along the right mediastinal contour, consistent with superior vena cava iatrogenic perforation, causing compression of the patent SVC. Central opacification defect indicating partial thrombosis from previous instrumentation is seen in the left brachiocephalic vein. Pleuro-pulmonary changes are excluded.
During supportive treatment, extravasated contrast in the mediastinum is not detectable at radiographic follow-up 48 hours later (Fig. 3).
Finally, single-chamber PM with right ventricular leadwire is successfully positioned (Fig. 4).
Discussion
Worldwide, permanent cardiac conduction devices (CCD) including pacemakers (PM) and implantable cardioverter-defibrillators are increasingly adopted to treat arrhythmias, in the vast majority (85%) of cases in people over 65 years of age. Despite improvement in pacing technology, relative ease of device implantation, and increasing experience by interventional cardiologists especially in referral centre, risks and complications associated with CCD positioning are often underestimated [1, 2].
Most PM-related complications are acute, as they occur at the time of or immediately after implantation, usually secondary to venous vascular access. Complications include dysrhythmia from improper lead placement, pocket haematoma or serous collection, pneumothorax, haemothorax, perforation of heart muscle or vein, heart valve damage, and venous thrombosis in descending order of frequency. The overall rate of clinically significant complications is 3.3-7.5%, and increases with advanced age. The risk of perioperative death is below 0.5%, and reoperation is needed in up to 5% of patients. Wound infection and/or dehiscence is rare (<1%) but usually mandates pacing system removal [1, 3-5].
Chest radiographs have been traditionally used for identifying the CCD device after implantation and throughout its duration, assessing its position, wires integrity, and to suggest complications. Although pneumothorax and the uncommon haemothorax are increasingly rare with the adoption of axillary vein cannulation, they should still be sought for on routine plain films obtained immediately after CCD positioning. As this case exemplifies, in selected patients multidetector CT imaging proves valuable to further investigate suspected post-procedural complications [1, 3].
Perforation of cardiac cavities or large veins reportedly occurs in 0.5-2% of cases, occurs more frequently in the elderly although risk factors are not clearly defined. The variable clinical manifestations include chest pain, dyspnoea, and hypotension. Perforation may lead to longer hospital stays, cardiac tamponade, and sometimes prove fatal. Myocardial penetration is suggested by abnormal pacing and sensing signals, or atypical position of the right ventricular lead projecting more caudally than normal on the frontal chest radiograph. Alternatively, MDCT imaging may detect new pleural or pericardial effusions, or extraluminal blood, fluid, or contrast medium collections resulting from perforation [1-5].
Furthermore, venous thrombosis from central instrumentation is increasingly common because of the growing number of procedures. PM-related thrombosis of the superior vena cava, brachiocephalic or subclavian veins is reported in up to 0.4% of insertions, may be further complicated by sepsis or endocarditis, and may be confidently detected at MDCT as opacification defects [1, 3].
Differential Diagnosis List
Superior vena cava perforation, brachiocephalic vein thrombosis during pacemaker positioning
Persistent cardiac arrhythmia / PM malfunctioning
Pneumothorax
Haemothorax
Superior vena cava thrombosis
Pulmonary embolism
Infectious endocarditis
Cardiac perforation
Haemopericardium
Pericarditis / Tamponade
Final Diagnosis
Superior vena cava perforation, brachiocephalic vein thrombosis during pacemaker positioning
