The hTEE system for transoesophageal echocardiographic monitoring of haemodynamic instability

CE marking

The hTEE system is a class IIa medical device that was CE marked to ImaCor Inc. in July 2011.

Description

The hTEE system visualises the structures of the heart and provides episodic assessment of cardiac filling and function in people who are haemodynamically unstable. The system comprises 4 main components:

Optional components are an uninterruptible power supply and a universal serial bus data transfer module.

The disposable ClariTEE probe is 5.5 mm in diameter. It uses a monoplane piezoelectric design operating at 7 MHz and 6 MHz, which provides an image penetration depth of up to 18 cm and an image sector angle of 70° or 90° (software version 2.3.0). The miniature design allows the probe to remain in position for up to 72 hours; the imaging console is attached and detached as needed.

After turning on the machine and entering patient information via an on-screen keyboard (for first assessment only), the user attaches the ClariTEE probe to the control handle. The probe is inserted down the oesophagus where the 4 chamber view, or superior vena cava view, can be obtained. For the trans-gastric short axis view, the probe enters the top of the stomach, where it is then flexed upward (anteflexed up to 90°) or downward (retroflexed to 20° minimum). The user then adjusts the position of the probe with the system in image mode to provide real-time views of cardiac filling and function. A 3-lead electrocardiogram cable may be used to assist the identification of images at end systole and end diastole.

The ultrasound imaging software performs 7 functions:

Cineloops are 3 or 6 second ultrasound image files recorded and saved by the user during real-time imaging. Single-view or split-view screen modes allow real-time images and cineloops to be viewed, acquired, optimised and compared. On-screen imaging controls allow the user to adjust brightness (B-mode), colour flow, gain, filter, contrast and depth to optimise real-time images.

The system provides 3 cross‑sectional views (transgastric short axis, mid‑oesophageal 4 chamber and superior vena cava), allowing the user to assess different aspects of cardiac filling and function. Following assessment, the probe is detached from the umbilical control handle and remains in place for further episodic monitoring or assessment, as needed, for up to 72 hours.

Calculated hTEE parameters are made in measuring mode using stored cineloops which are recalled for review. On-screen playback and, if necessary, further image quality adjustment controls are combined with 2 measurement tools for area (tracing tool) and distance (measuring tape tool) to calculate cardiac filling and function parameters. Cineloops can be transferred from the Zura EVO console and synchronised with a local picture archiving and communication system server. Patient records can also be transferred between Zura EVO systems using a data transfer module connected to the USB port.

Intended use

The ClariTEE probe may remain inserted for up to 72 hours, allowing for the episodic assessment of cardiac filling and function using transoesophageal echocardiography. It is not a continuous monitoring device and is not indicated for use on patients under 18 years of age. As with conventional transoesophageal echocardiography, patients with known contraindications such as oesophageal or stomach varices, obstructive oesophageal pathology, recent surgery or radiation therapy in the oesophageal or gastric area should be evaluated by a clinician before having a hTEE procedure. There are no additional contraindications for hTEE compared with conventional transoesophageal echocardiography.

Setting and intended user

The hTEE system is intended for use on people who require advanced hemodynamic management in critical care settings including the cardiac intensive care unit and the general intensive care unit. After receiving device-specific training, intensive care physicians can conduct the qualitative and semi-quantitative hTEE assessment.

Current NHS options

Current NHS options for providing cardiac imaging in critical care settings include conventional transthoracic echocardiography and transoesophageal echocardiography ultrasound imaging systems.

Conventional transoesophageal echocardiography is understood to be available on most cardiac intensive care units for haemodynamic instability where it would be conducted by an anaesthetist or intensivist. However, on general intensive care units in the UK, it seems more likely that, if available, a transthoracic echocardiogram would be done for haemodynamic instability.

The European Society of Cardiology recommends that transoesophageal echocardiography be used if transthoracic examination is inconclusive and the clinical question is important enough to warrant the risk and moderate discomfort associated with the procedure (Flachskampf et al. 2010).

On a general intensive care unit, a cardiologist is likely to perform conventional transoesophageal echocardiography for diagnostic reasons. These may include identifying or excluding a cardiovascular cause of haemodynamic instability, including valve lesions, endocarditis and other consequences of sepsis, myocardial pump dysfunction, hypovolaemia, cardiac tamponade, aortic dissection, and intracardiac masses (Flachskampf et al. 2010). However, the European Society of Cardiology recommends a higher specification multiplane ultrasound probe for most of these applications, and the basic monoplane ClariTEE probe is not intended for conventional diagnostic use.

As part of the European Society of Cardiology recommendations, Flachskampf et al. (2010) state that transoesophageal echocardiography may be used on a critical care patient with severe or life-threatening haemodynamic disturbance who is unresponsive to treatment, or on patients in whom new or ongoing cardiac disease is suspected and who are not adequately assessed by transthoracic imaging or other diagnostic tests.

NICE is not aware of other CE-marked devices that have a similar function to the hTEE system. The ClariTEE probe is the only miniature, indwelling transoesophageal echocardiography probe intended for episodic monitoring for up to 72 hours.