What is the clinical presentation of cardiogenic shock in pulmonary artery catheterization (PAC)?

Updated: Dec 22, 2017
  • Author: Bojan Paunovic, MD; Chief Editor: Karlheinz Peter, MD, PhD  more...
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Answer

Cardiogenic shock is the result of severe depression in cardiac performance. Cardiogenic shock is characterized by systolic blood pressure less than 80 mm Hg, cardiac index less than 1.8 L/min/m2, and PCWP greater than 18 mm Hg. This form of shock can occur from a direct insult to the myocardium (eg, large AMI, severe cardiomyopathy) or from a mechanical problem that overwhelms the functional capacity of the myocardium (eg, acute severe mitral regurgitation, acute ventricular septal defect).

Common causes of acute mitral regurgitation in critical care units are ruptured papillary muscles secondary to AMI, myocardial ischemia leading to papillary muscle dysfunction, bacterial endocarditis, ruptured chordae, and trauma. Other causes are rheumatic fever and myxomatous degeneration of the mitral valve. With acute mitral regurgitation, large volumes of blood regurgitate into a poorly compliant LA, raising Ppv and causing pulmonary edema.

Large V waves usually are observed in the PCWP pressure tracing (see images below).

Tall V waves presented here on pulmonary arterial Tall V waves presented here on pulmonary arterial and wedge pressure waveforms are characteristic of severe mitral regurgitation.
Large V waves in a case of mitral regurgitation. Large V waves in a case of mitral regurgitation.
Simultaneous recording of ECG helps identify V wav Simultaneous recording of ECG helps identify V waves in mitral valve regurgitation; V waves correspond to T waves on ECG.

The PA waveform appears falsely elevated because of the large V wave reflected back from the LA through the compliant pulmonary vasculature. The Y descent is quite rapid as the overdistended LA quickly empties. Care must be exercised to distinguish a large V wave from a systolic PA waveform. Failure to recognize a large V wave may cause the PAC to be advanced further in an attempt to record a PCWP pressure, increasing the risk of perforation.

In chronic mitral regurgitation, an equivalent volume of blood may regurgitate, but this volume is better tolerated by a markedly dilated LA. Compared with acute mitral regurgitation, LA pressure may be less and large V waves may be absent.


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