Question 11

Outline how you would distinguish between post-operative myocardial ischaemia and pericarditis on assessment of an ICU patient with ST segment elevation on a 12 lead ECG within the first 48 hours of coronary artery bypass surgery.
Your answer should consider factors that might make this distinction difficult.

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College Answer

Syllabus topic/section:

2.1.18 Peri-operative Issues in Intensive Care – L1.

Aim:

To examine the candidate’s knowledge regarding the assessment and management of a common complication of cardiac surgery.

Discussion:
The question was generally well answered. Candidates who specifically addressed the clinical scenario (post CABG surgery, not general pericarditis presentations) and addressed each aspect of assessment (history, examination, and investigation) performed well. A reminder for candidates to be specific, if possible, with detail (such as specific ECG changes expected). Also, a reminder for candidates to refer to the glossary of terms – outline indicates some detail and explanation required, rather than a simple list.
 

Discussion

  • History
    • Emergency vs. elective bypass: if the patient was already having a STEMI, they are at risk of Dressler's syndrome anyway, leaving aside the complications of cardiac surgery
    • Onset: ischaemia is more likely to be abrupt, whereas pericarditis is more likely to be slow in onset
    • Chest pain, which is made worse by leaning forward
  • Examination findings
    • Haemodynamic parameters:
      • Graft failure or vasospasm would usually be associated with worsening cardiac output and organ perfusion, whereas pericarditis is usually stable
    • Fever, not otherwise explained
    • Pericardial rub on auscultation
  • ECG findings
    • ​​​​​​​Specific findings of pericarditis include:
      • Concave "saddle-like" ST elevation
      • Modest magnitude of elevation, usually 0.5-1.0 mm
      • Depression of the PR interval
      • Reciprocal ST depression and PR elevation in lead aVR
      • Changes are otherwise widespread and do not obey coronary artery territories
  • Biochemistry
    • ​​​​​​​Inflammatory markers (WCC< ESR, CRP) will be elevated - more so in pericarditis then in cardiac ischaemia
    • Trend of cardiac biomarkers (eg. troponin) would be downward with pericarditis and upward with ischaemia
  • Imaging
    • ​​​​​​​TTE or TOE could reveal
      • new regional wall motion abnormalities, suggesting ischaemia, or
      • pericardial effusion and pericardial thickening suggestive of pericarditis
    • CXR, which could reveal pleural effusion
  • Factors that make this distinction difficult:
    • ​​​​​​​The patient may still be sedated and intubated, which makes history taking and examination more challenging
    • Postoperative pain and strong analgesia makes the characteristic pain of pericarditis less discernable
    • Recent cardiac surgery (dressings drains and residual intrapericardial air) obscures classical auscultation findings
    • Intrathoracic hardware makes the CXR difficult to interpret
    • Pacing and myocardial inflammation makes the assessment of the ECG difficult
    • Biomarkers of inflammation and cardiac injury are uninformative, as they are inevitably elevated following cardiotomy

References

Liu, Jing, and Yochai Birnbaum. "ST segment elevation following coronary artery bypass surgery." Journal of Electrocardiology 57 (2019): 128-131.

Lockerman, Zachary S., et al. "Postoperative ST-segment elevation in coronary artery bypass surgery.Chest 89.5 (1986): 647-651.

Sasse, ’Tom, and ’Urs Eriksson. "Post-cardiac injury syndrome: aetiology, diagnosis, and treatment." ESC E-Journal of Cardiology Practice 15 (2017): 21-31.

Aten, Kristopher, Kenneth Raney, and Anas Alomar. "Dressler Syndrome: Not Just a Relic of the Past." Cureus 14.10 (2022).