POCUS Case of the Month
A 65 year old male presented to his family doctor with 15 minutes of severe central chest pain. His ECG demonstrated tombstone ST-segment elevation in the anterolateral leads, so an ambulance was called to transport him to hospital.
On paramedic arrival he was found to be in complete heart block (CHB) with no recordable blood pressure. They treated him with aspirin, atropine and an adrenaline infusion whilst rapidly moving him towards the Emergency Department. Just minutes away from the ED, he deteriorates into a pulseless electrical activity (PEA) arrest and CPR is commenced…
On arrival to the ED, CPR was still in progress. The patient had no pulse and monitored in a complete heart block rhythm. An urgent Basic Echo in Life Support (BELS) study was performed…
From the echo above, a pericardial effusion (+tamponade) was excluded as a cause for the patients PEA arrest. The clips below demonstrated the presence of atrial contraction but no conduction to the left ventricle.
A trial of external cardiac pacing was done with successful left ventricular capture confirmed by Point of Care Ultrasound (POCUS) and clinically by the return of a perfusing circulation.
Pacing was successful for about 10 minutes with visible LV contraction and a palpable pulse however subsequently there was a loss of output despite continued attempts at external pacing. CPR continued however patient became increasingly acidotic and the decision was made terminate resuscitative efforts.
The development of complete heart block in acute myocardial infarct (MI) is associated with a poorer outcome. There is, however a difference in prognosis between anterior MI and inferior MI, with anterior being more sudden and having a worse outcome(1).
Heart block in inferior MI is often as a result of increased vagal tone or the release of adenosine and is usually transient; whereas in anterior MI it is related to ischaemia and necrosis of the conduction system with a worse outcome.
Transcutaneous pacing can provide an effective temporary method to increase heart rate an output in these patients but this may only have a limited impact on prognosis as it is the size of the infarct that will ultimately determine the outcome. Nonetheless it should be performed if it improves haemodynamics.(2)
Take Home Messages.
- POCUS in this case allowed the treating team to immediately rule out significant pericardial effusion (while CPR was in progress) and confirm ventricular capture with pacing.
- Complete heart block in AMI is associated with poorer outcomes but anterior infarct is worse than inferior.
- It is worth attempting transcutaneous pacing as it may improve haemodynamics.
- Thompson PL. Cardiac arrhythmias and conduction disturbances in acute coronary syndromes. In: Window J, editor. Coronary Care Manual. 2 ed. Australia: Elsevier; 2011. p. 495-502.
- Antman EMaJL. ST-Segment Elevation Myocardial Infarction. In: Dennis Kasper ea, editor. Harrison’s Principles of Internal Medicine. New York: McGraw-Hill; 2015.
Author: Anthony Wald AMS, PoCUS Echo Educator MonashHeart, Monash Health
Images: Dr Gabriel Blecher MBBS (Hons), FACEM, CCPU Emergency Physician Monash Health