Pulsus Paradoxus: Cardiovascular Function and Assessment

Cardiovascular Assessment:

Pulsus Paradoxus

Assessing cardiac function, blood pressure and hemodynamic status play an important role during our overall patient assessment and treatment. Although 12 lead ECG evaluation is an essential part of patient assessment, especially cardiac etiology, understanding basic cardiac function plays a major role during treatment and overall patient status.

During normal hemodynamic conditions, inspiration leads to decreased intrathoracic pressures. Changes that occur during these events, lead to changes in blood pressures.  Keep in mind, when we measure non-invasive blood pressures, we are assessing arterial pressures, not venous.

• Normally during  exhalation and early inspiration, thoracic pressures increase (equializing with external pressures) and Cardiac Output (CO) decreases slightly, since the Left Ventricle (LV) does not have the adequate amount of space to expand for full capacity preload

•This drop in blood pressure is normally < 10mmHg

•The heart rate also increases as a compensatory mechanism, in an attempt to maintain normal Oxygen Delivery (DO2)

In a short summary, this occurs due to:

• Decreased intrathoracic pressures increase venous return to the Right Ventricle (RV), while increased pressures during exhalation, reduce venous return

•This increase in Central Venous Pressure (1-6mmHg) which reflects the pressure of the RV, increases the RV volume and capacity, forcing the Interventricular Septum (the wall dividing the ventricles) towards the left

•This Septum shift towards the left slightly reduces the LV capacity. This is even more marked during a Pericardial Effusion (fluid in the pericardial sac), where the LV can’t expand properly due to the pressure from the Septum and the pericardial sac, decreasing it’s internal diameter, leading to decreased Stroke Volume (SV) since it can’t produce a strong contraction

•A decrease in pulmonary vein blood volume to the LV due to blood pooling from increased lung expansion also reduces the amount of blood brought to the LV

 A decrease >10mmHg during the systolic pressures during inspiration, is considered a significant decrease in Left Ventricular (LV) volume, known as Pulsus Paradoxus. The term paradox refers to an audible cardiac cycle without a palpable pulse during this event.

An easy way to assess for Pulsus Paradoxus is by manual BP assessment.

  1. Inflate the blood pressure cuff until no sounds are heard
  2. Begin deflating the cuff at approximately 2-3mmHg/sec, until the first Korotkoff sound (normal auscultated blood pressure sound) during exhalation
  3. Then listen for the next Korotkoff sound during inspiration
  4. If the drop between the first sound and the next is > 10mmHg, then there is positive Pulsus Paradoxus

What does this mean?

The presence of Pulsus Paradoxus means that there is reduced Venous return to the heart which leads to reduced arterial blood pressure, decreasing CO.

The most common causes of of Pulsus Paradoxus include:

. Increased Pulmonary pressures during COPD (Chronic Obstructive Pulmonary Diesease) exacerbation or Asthma

For further information about Pulmonary Pressures, click on the link below:
http://www.ems12lead.com/2014/01/16/pulmonary-pressures-and-ecg-patterns/

. Cardiac Tamponade
. Pericardial effusions (can lead to tamponade)
. Cardiomyopathies
. Cadiomyopahty
. Post large Myocardial Infarction
. Hypovolemia

2 Comments

  • Shane says:

    Sorry I’m confused. I though an increase in intrathoracic pressure decreases pre-load to the heart and not increase it as mentioned here? Could anybody clear this up?

    Thanks!

    • Ivan Rios says:

      Shane, you are correct. Positive intrathoracic pressures decrease venous return (preload), while negative pressures increase it. Notice, the comment is saying that these pressures increase venous return, not increased intrathoracic pressures, however, I will update this portion so there won’t be any further confusion. During inspiration, intrathoracic pressures, which are mainly negative pressures because you’re pulling air into the lungs from the atmosphere, will increase venous return in combination with increased abdominal or diaphragmatic pressures.

      Thank you for your time and input.

      Ivan Rios

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Comments
know it all parapup
83 Year Old Male: Shortness of Breath
@ Kyle I would question your authority to call out people for not having a license or being a know it all parapup when your tx basically entails "call medical control." I think we can both agree that his cardiac output is not great at all. I assume your reluctance to give him any other…
2014-10-30 20:26:11
Kyle
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Well st elevation in avr and v1 associated with anterior and lateral depression would call for possible posterior wall MI. 15 lead would be in order. Also check all the leads for appropriate placing. If v7, v8, and v9 show the elevation i would treat as a STEMI per my protocol. Asprin only until medical…
2014-10-30 18:14:05
Tim
The most awesome STEMI test on the internet!
Thanks for the app. It made me think about all that one may see in the field. The only problem was I never got a score or saw the results of how I did other than saying I had completed the test. Anyway a great way to get the old brain working.
2014-10-30 13:14:27
Brian
83 Year Old Male: Shortness of Breath
I mostly agree with dustin. I believe this is may be an isolated posterior MI. The R wave in V2 points to it being a posterior MI. otherwise it is a 1st degree av block with a LAHB. I am somewhat concerned with the concordant t segment depression noted and in fact if you were…
2014-10-30 04:22:44
Karl Brennan
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Great article , however in VF caused by hyperkalemia it should be avoided along with lidocaine , Since it shuts down the K channels, the eiteiology of the arrest hyper K, K channels are needed to exchange K in the cell. Calcium , Bicarbonate, dextrose and insulin should be used to decrease K levels along…
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