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ECHOCARDIOGRAPHY:  TTE / TOE

Philips iE33 ultrasound with Live 3D TEE:  http://www.medical.philips.com/iE33

 Echocardiography
Echocardiography is the use of sound waves to produce an image of the heart and/or surrounding structures. All information obtained from echocardiography is derived from cardiac imaging and analysis of blood flow velocity using various Doppler modes. TTE/TOE has evolved to allow the generation of high quality , real time ultrasonic images in multiple planes. With the addition of Doppler capability, the ability to assess normal and pathological flows is facilitated. It can be used to assess mitral,aortic valuvar disease, prosthetic vale function and evaluate the heart for thrombi, vegetations or dissection. It is used to evaluate the quality of surgical repair or replacement of cardiac valves, assess the quality of congenital heart disease repair. Other applications include assessment of regional wall motion abnormalities and ventricular function, assess ventricular filling, contractility and response to various therapeutic interventions can be observed visually. It can also be used to assess the aetiology of unexplained hemodynamics (effusions). Other conditions that can be diagnosed with TTE/TOE include air embolism, fat embolism and evaluation of PFO, ASD or VSD.

Echocardiography has become an integral part of the management of patients undergoing cardiac surgical procedures and because of the wealth of haemodynamic data obtained is a valuable tool in the management of the critically ill patient. Typical applications include the emergency assessment of patients pre-operatively to determine whether surgery is indicated (dissection or transection of the thoracic aorta ). Other applications include postoperative care and to evaluate and treat the critically ill patient in intensive care.

TTE
Trans thoracic echocardiography is performed with a probe placed on the patient’s chest. Positioning of the patient is important in obtaining adequate views. The advantage of TTE is that the patient can be fully conscious for the examination. However Trans thoracic echocardiography can be difficult because of anatomic and other factors (obesity, emphysema, abnormal chest wall surgical dressings etc). TOE can provide better views of the cardiac anatomy in whom TTE is difficult or it can be used to compliment the TTE examination especially providing better visualisation of the posterior and left sided structures of the heart. TTE cannot be used if the chest is opened or if surgical equipment, drapes, monitoring equipment or dressings block access to the chest.

TOE
TOE can provide better views of the cardiac anatomy in whom TTE is difficult or it can be used to compliment the TTE examination especially providing better visualisation of the posterior and left sided structures of the heart.
A full medical history should be taken with particular reference to dysphagia, upper GIT surgery or radiation , abnormal dentition, cervical spine disease, bleeding problems and allergies. A complete physical examination should be carried out with special attention to the cardio-respiratory system, as well as the mouth, teeth and oro-pharynx.
The anaesthesised or critically ill patient whose trachea is intubated is usually positioned supine. The probe is passes blindly into the oesophagus. The passage of the probe should never be forced. All awake conscious patients should be fasted. In the awake patient non intubated patient the mouth and oro-pharynx are anaesthetised with topical applications of lignocaine. Light intravenous sedation with short acting agents may be used. The patient is placed in a lateral decubitus position and the lubricated probe is gently introduced in the oro-pharynx. A tooth guard should be used to protect the probe from the patient biting down on it. Patient’s swallowing facilitates the passage of the probe into the upper oesphagus. Close monitoring of the cardiorespiratory function is important. The patient should receive supplementary oxygen via nasal prongs and pulse oximentary should be used in all cases.

Contra-indications
Absolute:
• Oesphageal obstruction (stricture, tumour)
• Oesphageal diverticulum
• Oesphageal laceration
• Oesphageal fistula
• Active upper GIT bleeding
Relative:
• Oesphagitis
• Oesphageal varices
• Remote gastric surgery
• Gastric ulcer
• Hiatus hernia
• Cervical spine disease
• Bleeding diathesis

Complications
• Oesphageal rupture
• Pulmonary complications
• Arrythmias
• Angina
• Hypotension
• Pulmonary odema
• Cardiac arrest
• Pharyngeal bleeding
• Laryngospasm