The Paradoxical Alternative

aka Cardiovascular Curveball 006

Consider a 49 year-old female with a history of smoking and two weeks of increasing shortness of breath. She is being treated for pneumonia on the ward for three days but getting worse. An ICU review is performed on the ward and the following ECG is obtained.

Paradoxical Alternative ECG

Q1. Describe the ECG findings. What investigation is indicated?

Curveball Answer

The most significant finding on this ECG is the presence of electrical alternans.

The rhythm is sinus tachycardia at 100/min and the axis is normal.

The investigation indicated is an echocardiogram to confirm the presence of a pericardial effusion and to look for echocardiographic evidence of  pericardial tamponade.

Q2. You ring the cardiologist they ask you to assess the degree of pulsus paradoxus. What is pulsus paradoxus and what are the potential causes of this phenomenon?

Curveball Answer

Pulsus paradoxus is defined as an inspiratory drop in blood pressure of 10mmHgor more during normal breathing.

Pulsus paradoxus is caused by:

  • pericardial tamponade
  • hypovolaemia (especially during positive pressure ventilation)
  • acute asthma
  • massive pulmonary embolism

On the cardiologist’s advice you assess the degree of pulsus paradoxus and no significant respiratory variation in systolic pressure is present.

Check that the R-R interval on the ECG is regular to rule out arrhythmia as the cause of a fluctuating systolic blood pressure.

Q3. The cardiologist argues that the absence of pulsus paradoxus is reassuring. Are they right?

Curveball Answer

In this particular case, no.

Electrical alternans is usually associated with tamponade and there are many reasons why pulsus paradoxus may be absent in the presence of cardiac tamponade including:

  • Pericardial adhesions (particularly over the right heart)
    • impede volume changes
  • Severe left ventricular failure or marked left ventricular hypertrophy
    • in these circumstances the pericardial pressure effectively equilibrates only with the right heart pressures with the much less compliant left ventricle resisting phasically changing pericardial pressure
  • Right ventricular hypertrophy without pulmonary hypertension
    • causes right-sided resistance to the effects of breathing
  • Atrial septal defects
    • increased venous return balanced by shunting to the left atrium
  • Severe aortic regurgitation
    • produces sufficient regurgitant flow to damp down respiratory fluctuations

  • Spodick DH. Acute cardiac tamponade. N Engl J Med. 2003 Aug 14;349(7):684-90. PMID: 12917306.

Cardiovascular curveball 700


Cardiovascular Curveball

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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