College Answer

The PA catheter provides access to pulmonary and central venous circulations, at a relatively low incremental cost.   The main information obtained is from measurement of pressures (eg. within right atrium or pulmonary arteries), but additional information includes core temperature, pressure waveforms,  occlusion  pressure,  cardiac  output  (thermodilution  or  continuous),  mixed  venous oxygen saturation (intermittent [including from sites other than PA] or continuous).  Standard limitations include the variable relationship between pressure and volume, and the risks of using derived variable.   Other risks can be categorised into those associated with central venous catheterisation (e.g. arterial puncture, air embolus, infection), floating of the catheter (e.g. arrhythmias), and balloon inflation (e.g. PA rupture).   Some information can be continuously monitored (e.g. pulmonary arterial pressures); other is intermittently sampled (e.g. occlusion pressure, thermodilution cardiac output), but without the risks of reinsertion.

Transoesophageal echocardiography requires additional very expensive monitoring equipment, and an expensive (but re-usable) probe. The TOE allows visualisation of cardiac (and surrounding) structures, and measurement/estimation of a number of haemodynamic parameters.   A visual estimate is obtained of various parameters: including volume status (pre-load), contractility (left and right sided systolic and diastolic function), regional wall motion, abnormal masses (eg. vegetations) and peri-cardial/pleural/peri-aortic collections. Using Doppler, assessment of valvular function, and estimate of pressures and cardiac output is also possible.   This is an intermittent technique (not usually left in situ for more than a few hours), which is highly operator dependent, where most risks associated with insertion and manipulation (eg. gastrointestinal bleeding/rupture).   Insertion and manipulation usually requires some degree of sedation.

Indications depend on specific information desired, and the local expertise.   The potential information obtained with either technique must be weighed against the risks in any given clinical scenario.  If standard precautions are used, mortality or major morbidity with either technique is thankfully rare.

Discussion

This question lends itself well to a table format.