The Two-Headed Swan

Abstract

Pulmonary artery catheterization is a frequent procedure for hemodynamic monitoring in critically ill patients or high-risk surgical patients. Mechanical and infectious complications are recognized, though catheter dysfunction and malposition are more frequent and often require clinical intervention. We present the case of a Swan-Ganz catheter with the appearance of a mechanical fracture at the distal end, which required clinical and radiographic investigation to determine the nature of the aberrancy. The evaluation of a malfunctioning pulmonary artery catheter (PAC) is a frequent occurrence in the intensive care unit and requires careful clinical consideration and radiographic examination.

Introduction

The PAC is commonly referred to as the Swan-Ganz catheter, developed by Henry Swan and William Ganz more than 30 years ago.[1] This vascular catheter is unique because of an inflatable balloon at its distal end, allowing it to be flow directed through the cardiopulmonary circulation. This feature established the ability to perform right heart catheterization at the bedside and is now used 1,500,000 times each year in this country.[2] This catheter allows for measurement of the pulmonary artery "wedge" or "occlusion" pressure, serving as a surrogate measure of cardiac preload or left ventricular end diastolic pressure as well as cardiac output, most commonly by a thermodilution method developed by Dr. Ganz. Both mechanical and infectious complications are recognized in conjunction with the use of this device. Dysfunction or malposition of the catheter is a frequent but underreported occurrence.[2]

Case Report

A 57-year-old male was admitted with an acute coronary syndrome and subsequently underwent "off pump" coronary artery bypass grafting. A PAC was inserted without complications at the time of anesthesia. His postoperative hospital course was complicated by multiple organ failure including septic shock, atrial tachyarrhythmias with variable atrioventricular block, and acute respiratory distress syndrome (ARDS). On the third postoperative day, the pulmonary artery occlusion ("wedge") pressure could not be measured from the PAC. A portable, supine chest radiograph (CXR) was obtained as part of routine evaluation for PAC dysfunction. The CXR (Figure 1) reveals diffuse, patchy consolidations consistent with ARDS and a PAC in the left pulmonary trunk. Two diverging ends of the PAC are apparent on the radiographic image. All previous and subsequent CXRs (Figure 2) confirmed a PAC with a single tip in the left pulmonary artery. The PAC was subsequently adjusted and regained full function, and upon removal was confirmed to be without abnormality. The patient slowly resolved all organ failure and was discharged home on the 11th postoperative day.

Figure 1.

Portable, supine chest radiograph with diffuse bilateral pulmonary infiltrates and a pulmonary artery catheter (PAC) in the left pulmonary trunk. The PAC appears to have a dual-head (arrows) due to tachyarrhythmias and the resultant exaggerated cardiac motion and pulsatile pulmonary artery flow from hyperdynamic sepsis during a normal radiographic exposure.

Figure 2.

Portable, supine chest radiograph with diffuse bilateral pulmonary infiltrates and a single-tipped pulmonary artery catheter in the left pulmonary trunk, taken shortly after the initial radiographic exposure.

Discussion

Upon initial review of the CXR in Figure 1, some physicians felt it was necessary to remove the device and determine if the catheter had suffered a mechanical failure at the distal end. Consideration of the likelihood of such a mechanical fracture led to further clinical and radiologic evaluation that confirmed the catheter to be intact and fully functional (Figure 2). The dual-headed appearance of this PAC was caused by dynamic cardiovascular motion during the radiographic exposure. This was possible because of the proximal position of the catheter in combination with the hyperdynamic state of sepsis and tachyarrhythmias exceeding the duration of radiographic exposure, thus exposing the tip of the catheter to greater cardiac motion and pulmonary arterial pulsation. The findings of this case are important to the practicing intensivist because a dual tip image on CXR may represent a normal, functioning Swan-Ganz catheter that simply needs repositioning. This case further illustrates the variety of complications that may occur with invasive hemodynamic monitoring strategies such as pulmonary artery catheterization.[2]

The PAC has been employed for decades under the assumption that patient care was improved with its use,[3] although recent data have strengthened the association between PAC use and increased mortality.[4] Complications from PAC use most frequently relate to catheter insertion and maintenance[5,6] or to patient management based upon erroneous data acquisition.[7,8] In comparison, radiographic detection of catheter failure is relatively uncommon and most often reported in association with a physical "knot" in the catheter requiring either fluoroscopic or surgical PAC removal.[9-11] Compared with proximal migration in this case, distal catheter migration may more easily be detected by assessment of PAC waveforms.[12] Alternative explanations for the radiographic findings in this case, such as a double exposure CXR, are unlikely given the normal exposure pattern elsewhere on the radiographic film.

The double-headed nature of the PAC in this report is further intriguing beyond the controversies surrounding its use, also symbolizing the multifaceted nature of PAC use.[2] The PAC may serve dual purposes, as an important tool in critical care diagnosis or therapy. In addition, PAC data may be interpreted based upon static or dynamic measures. Recognizing the dual nature of a medical intervention is an important consideration for physicians -- most obviously in the care of a critically ill patient where treatment decisions based upon the PAC may have unintended consequences due to the frequent misinterpretations of PAC data.[2] While large randomized trials have allayed some concerns about mortality specifically attributable to PAC use,[13-15] a high frequency of unexpected complications may result from PAC utilization, including increased frequency of venous thromboembolism[14] and acute renal failure.[15] Thus, the PAC remains a tool that may provide important physiologic information, but at a "cost" that may be unacceptably high. Finally, while daily CXRs are not necessary in all patients with a PAC,[16] as highlighted in this report, they are an important component in the evaluation of a dysfunctional PAC. Given the frequent complications that may arise from PAC use, and the potential for contributing to adverse clinical outcomes, clinicians must strongly reconsider the rationale for routine PAC use in many critically ill patients.

Conclusion

Pulmonary artery catheterization is frequently employed in patients undergoing cardiovascular surgery or suffering other critical illnesses. Dysfunction of the PAC is a common clinical problem requiring immediate and thorough evaluation. The ultimate question is whether its utilization will guide intensivists to improved or worsened outcomes.