Myocardial infarction in intensive care units; a systematic review of diagnosis and treatment.
Iain Carroll,1Thomas Mount,2Dougal Atkinson.2 1Royal London Hospital, 2Central Manchester Foundation Trust.
Patients in the intensive care unit are vulnerable to myocardial injury from a variety of causes, both ischaemic and non-ischaemic.1Ischaemiamay not be apparent in critically ill patients and therefore the distinction between myocardial injury and myocardial infarction (MI) is challenging.2 Furthermore, the relationship between underlying coronary artery disease and MI is less secure in the ICU setting than a general population, where conditions such as anaemia contribute to an imbalance between myocardial oxygen supply and demand and can cause type 2 MI.3
Consensus guidelines on management of MI, such as those from ESC and NICE, are difficult to apply to intensive care patients and the 3rd Universal definition of MI notes “ it may be a challenge for the clinician, caring for a critically ill patient... to decide on a plan of action when the patient has elevated cTn values.”1
In view these uncertainties, we conducted this review to address two questions:
When the clinician suspects an ICU patient is undergoing an MI, what diagnostic tests are most helpful?
When an ICU patient is diagnosed with MI, what treatment is most appropriate?
A systematic review was performed to identify relevant studies.
19 studies concerning use of ECG, cardiac enzymes, echocardiography and angiography were identified. 4 studies considered treatment of myocardial infarction.
A different strategy is required to reach a diagnosis of MI in intensive care than in patients presenting to hospital with chest pain. Patients rarely present with symptoms of ischaemia and when tests only are used in response to symptoms, signs or clinical suspicion, diagnosis of MI is frequently missed.
Regular 12 lead ECG or 12 lead ECG monitoring is more sensitive than 2 lead monitoring, regular measurement of cardiac enzymes is more sensitive than when provoked by symptoms. Echocardiographic abnormalities were more common the greater the increase in cTn, and in one study were associated with increased likelihood of angiographic abnormality. However, lesions requiring interventional treatment remained unusual.
1. Lim W, Qushmaq I, Cook D et al. Elevated troponin and myocardial infarction in the intensive care unit: a prospective study. Crit Care 2005;9:R636-44.
2. Thygesesn K, Alpert J, Jaffe A et al. Third universal definition of myocardial infarction. Eur Heart J 2012; 33: 2551–2567
3. ThygesenK, Alpert J, Jaffe A et al. Diagnostic application of the universal definition of myocardial infarction in the intensive care unit. CurrOpinCrit Care 2008;14:543–548