Question 1

Discuss the assessment and initial management (first hour) of an intubated patient admitted to the ICU with cardiogenic shock, after percutaneous coronary intervention for acute coronary syndrome due to a proximal LAD lesion.

Your answer should include but not be limited to the following headings: potential likely causes, suggested diagnostic approach, key elements of the management of likely causes.
(100% marks)

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College answer

Aim: To allow the candidate to demonstrate familiarity with initial ICU management of cardiogenic shock.

Key sources include: Paper 2019.1 Q1, CanMEDS Medical Expert.

Discussion: This is an exploration of cardiogenic shock post ACS. This SAQ is a repeat, almost identical in content to the 2019 SAQ.

Candidates did well if they addressed the aspects asked in the question and answers focused specifically on the details given.

The expert answer detailed the most likely and relevant causes of shock post PCI for an LAD lesion, with management in the first hour specifically addressing these causes. Elements of management contained in the expert pass include but are not limited to the following:

  • Resuscitation details including suggested vasoactive therapies with rationale,
  • Therapies targeting impaired left ventricular function including potential mechanical support,
  • Strategies to rule in/rule out the underlying causes, for example tamponade and other confounders such as electrical, valvular and stent complications.

Candidates are advised to place themselves in the clinical context outlined and describe what they would do, and this would improve their answers.

Candidates who were generic in their answers and who ignored the clinical stem did less well. For example, many candidates answered with a broad differential of all types of shock. Distributive and neurogenic shock is far less likely in the scenario given. The role of PEEP in cardiogenic shock was generally poorly explained and understood. Answers discussing the assessment and initial management should contain elements of prioritization. For example, a bullet point discussion on balloon pumps and the role of emergency CABG would gain more marks than noting the placement of central access and an arterial line.

Discussion

As the college has pointed out, this SAQ is very close in content to Question 1 from the first paper of 2019. In this case the SAQ design and the examiners' comments were a marked improvement; for example the previous SAQ needed the trainees to discuss cardiogenic shock but did not explicitly state this, so even though cardiogenic shock was obviously their expectation, the question approached it so obliquely that it ended up looking like a generic SAQ about the complications of angiography.

This time the examiners were more direct. The SAQ  also gave an expected structure. The patient had an LAD lesion and so right heart stuff is deprioritised in the model answer below, in the interest of saving space:

Potential likely causes of cardiogenic shock in this scenario:

  • Complications of the procedure
    • Cardiac tamponade
    • Coronary artery dissection or perforation
    • Aortic injury
    • Acute aortic or mitral regurgitation
    • Stent thrombosis
  • Complications of the underlying disease
    • Cardiogenic shock due to ischaemia
    • Brady or tachyarrhythmia
    • Severe metabolic acidosis producing low contractility
  • Complications of the anaesthetic
    • Cardiodepressant effect of general anaesthetics
    • Local anaesthetic toxicity
  • Unrelated catastrophic event
    • Pulmonary embolism

Suggested diagnostic approach: 

  • Rule out specific reversible causes:
      • ECG to rule out arrhythmia/ischaemia
      • TTE (or ideally TOE) to
        • assess cardiac systolic function and guide inotrope therapy
        • rule out acute valve pathology
        • rule out tamponade
        • observe new regional wall motion abnormalities
        • determine chamber filling and guide volume resuscitation
      • Repeat angiography to rule out stent misbehaviour (eg thrombosis)

    Key elements of the management of likely causes:

    • Definitive therapies to reverse specific pathologies:
      • Repeat angiography and thrombus aspiration
      • Emergency CABG or emergency valve surgery
      • Pericardiocentesis to correct cardiac tamponade
    • Medical cardiovascular support
      • Rate:
        •  Aim for stable HR 80-100, unless severe diastolic dysfunction is present
        • Chronotropic agents with inotropic effects (eg. dobutamine) would be ideal here
      • Rhythm:
      • Preload:
        • Crystalloid bolus, aiming at a restoration of circulating volume, guided by TTE/TOE
      • Afterload:
        • Noradrenaline to produce sufficient systemic vascular resistance to elevate the diastolic pressure and improve coronary perfusion
      • Contractility:
        • Dobutamine to improve LV contractility
        • Other agents (eg. milrinone, levosimendan) have less evidence in support of them
    • Mechanical cardiovascular support options
      • PEEP to decrease afterload and improve LV transmural pressure gradient
      • IABP to improve coronary diastolic perfusion
      • VA ECMO as a bridge to cardiac recovery

    References