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SamanthaRT2020 SamanthaRT2020 (New Member)

Swan-Ganz catheter & PCWP

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Student Here. I'm currently learning about the mechanisms of right heart catheterization. I know that PCWP is essentially an indirect measurement of LAP, but I cannot figure out why this is. Can someone shed some light on this? Thanks

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LAP is the pressure that is transmitted back through the pulmonary vasculature that must be overcome by the R ventricle in order for blood to flow and arrive at the left atrium.

The PA catheter floats out an artery (via the balloon) and occludes pulsatile flow from behind it that is generated by the R ventricle. Thus it's wedged in there. So the only pressure left that it is seeing is the pressure infront of it, which is transmitted back through the pulmonary system by the left atrium.

There is a relationship between the PAWP(or PCWP, same thing) and the pulmonary artery diastolic pressure: A PAWP higher than the PADP indicates that the PAWP measurement may be erroneous. On the other hand, if the PADP exceeds the PAWP by 6.0 mm Hg or more, the patient has probably developed pulmonary hypertension.

That's all I got.

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Just think of lighting a bright flashlight in a dark hallway, the flashlight being the inflated balloon of the swan wedged in the pulmonary artery. You can see everything in front of the light, and you can't see anything behind the flashlight. Now imagine seeing a yellow balloon at the end of the hallway, and a similar balloon near the flash light. You know they both are yellow balloons.

The yellow balloon closest to the flashlight is your PAP, and the yellow balloon distal to the flashlight is your wedge pressure. In a regular healthy person with no valve disease or pulmonary disease both pressures should be within 5mmhg of each other to truly represent a close to accurate reading. That's why when a swan is first floated into the pulmonary artery, it's very important to document your wedge pressure and your PAP to see any differences when trending your pressures.

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I and many others have abandoned the practice of "wedging" the catheter because of the extremely rare yet lethal complication of pulmonary artery rupture. That number is mostly useless anyway and not worth the risks.

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I had thought wedge pressure readings had pretty well gone the way of the Dodo bird. The last couple places I've worked prohibited wedge pressures outright, the places before that highly discouraged them. They don't really offer anything to decision making in a way that is likely to actually affect outcomes, and they are relatively dangerous.

The incidence of pulmonary artery rupture is reported as high as 1 in every 500 balloon inflations, and half of those patients will die before the rupture can be repaired. That's a lot of risk for something that provides relatively little treatment-guiding hemodynamic data.

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I and many others have abandoned the practice of "wedging" the catheter because of the extremely rare yet lethal complication of pulmonary artery rupture. That number is mostly useless anyway and not worth the risks.

Yes, wedging the swan is rarely even performed due to the risks which out weight its use in the clinical setting. That's why when the interventional cardiologist floats the SWAN, he/she notes both the wedge pressure and PAP to establish a baseline relationship. Once that is established, they would no longer need to perform any further wedge pressures and just rely on the PAP pressures to give an accurate "rough" estimate of your end diastolic pressures or wedge pressure.

The numbers don't mean anything unless they first establish a relationship between the PAP and Wedge pressures in cathlab.

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Yes, wedging the swan is rarely even performed due to the risks which out weight its use in the clinical setting. That's why when the interventional cardiologist floats the SWAN, he/she notes both the wedge pressure and PAP to establish a baseline relationship. Once that is established, they would no longer need to perform any further wedge pressures and just rely on the PAP pressures to give an accurate "rough" estimate of your end diastolic pressures or wedge pressure.

The numbers don't mean anything unless they first establish a relationship between the PAP and Wedge pressures in cathlab.

Especially now that a simple bedside echo gives far more relevant information than a PA catheter in the majority of cases. They're really not worth the trouble except in very specific circumstances.

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something about an uninterrupted fluid column  between the pulmonary artery and the left atrium during a portion of the cardiac cycle which allows for interpretation of the left atrial pressure.  But it is only accurate when there is no cardiac/pulmonary disease that would distort the numbers.  So why would you put in a PAC in a completely healthy person?  It is mainly used in the OR during open hearts to guide fluid resuscitation and if there are any specific abnormalities the cardiologist/anesthesia can interpret it and provide an appropriate intervention.  In our ICU we used them for severe PAH to guide treatment of very potent pulmonary vasodilators. 

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4 minutes ago, murseman24 said:

 It is mainly used in the OR during open hearts to guide fluid resuscitation and if there are any specific abnormalities the cardiologist/anesthesia can interpret it and provide an appropriate intervention.  

We don't even do that anymore...it's all echo now...if the surgeon asks for a PA catheter anymore it's for ICU management. 

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6 minutes ago, offlabel said:

We don't even do that anymore...it's all echo now...if the surgeon asks for a PA catheter anymore it's for ICU management. 

cool.  We use a TEE during the procedure but they still put the PAC in.  I've heard a lot of places don't though.

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