Detection of iatrogenic cardiac tamponade by transesophageal echocardiography during vena cava filter procedure

Evaluation of hypoxemic patients with transesophageal echocardiography

OBJECTIVE

To summarize the use of transesophageal echocardiography when investigating hypoxemic patients in the intensive care unit, to assess its risks and benefits, and to evaluate which diseases of the cardiopulmonary system, mediastinum, and thorax it will help to guide therapeutic decisions.

DESIGN

A review of current literature and practice guidelines was performed.

RESULTS

Hypoxemia, due to a number of different reasons, is common in critically ill patients. Many diagnoses and therapeutic decisions have to rely on good-quality imaging. However, transthoracic echocardiography often produces poor-quality pictures; other imaging modalities involve transferring unstable patients to the imaging suite. Transesophageal echocardiography can safely be performed at the bedside and generates excellent image quality.

CONCLUSION

Transesophageal echocardiography is a safe procedure that can be performed at the bedside and that produces high-quality images of the heart, its related structures, and its function. It helps detect extracardiac pathology leading to hypoxemia and may be used to guide fluid resuscitation and optimize tissue oxygenation.

Efficient implementation of non-linear valve law and ventricular interaction dynamics in the minimal cardiac model

A minimal model of the cardio-vascular system (CVS) with ventricular interaction and inertial effects that accurately captures the physiological trends of a variety of disease states has been developed. However, the physiologically accurate open on pressure, close on flow valve law is computationally heavy to implement, reducing the model's potential clinical benefit. A significantly simpler representation of the valve law using Heaviside functions is derived and the ventricular interaction equations are reformulated to obtain a unique closed form analytical solution. The new formulation is tested and compared with the previous formulation for a healthy human and four clinically significant disease states: mitral and aortic stenosis, pulmonary embolism and septic shock. The new model formulation matches the previous model definition, differing by a mean model response error of no more than 0.2%. Computationally, it is 24 x faster than the previous method. More specifically, a short 20-beat simulation that took 102 s now requires 4.3 s, significantly improving the model's potential for practical use in a diagnostic and/or decision support role in the intensive care unit.

Complications of Inferior Vena Cava Filters

Inferior vena cava (IVC) filters offer a safe and effective means of preventing pulmonary embolus and have reduced complications when compared to earlier techniques of caval interruption. However, despite continued improvement in filters and insertion methods, complications still occur. Pneumothorax, hemorrhage, and vessel injury may result while obtaining vascular access. Filter misplacement, excessive tilt, and vascular injury have been reported with insertion, but preinsertion cavography is helpful in preventing these insertion-related complications. Attention to detail, proper use of guidewires, and preinsertion imaging are vital in preventing insertion-related complications as well. Long-term complications occur in a minority of patients and include recurrent pulmonary embolus, caval occlusion, and filter migration. Overall, the benefits of preventing pulmonary embolism far exceed the risks related to filter placement in properly selected patients.