Dear Editor,

The Emergency Department Cardiology Analogy Model (EDCAM)1 has previously described how patient crowding can be likened to blood flow through the heart with preload, contractility and afterload as factors to consider. Currently working in an ED that is moving down the far side of the Frank–Starling curve in efficiency, we would like to expand on this model to incorporate and delineate cardiac pathology analogies to the ED function.

Angina– pain occurring when the work of the department exceeds staff work capacity. In chronic situations, the pain can become unrecognizable (silent angina). Angina can either be exertional (related to degree of ED activity and bed block) or unstable (because of random events such as external audits or hospital reviews). Pain resolves with decreased work load.

Sick sinus syndrome– poor pacemaker or clinical and managerial leadership activity leading to a poorly contracting or ineffective department. As a last resort, external pacing can be applied but this is a painful process, usually requiring analgesia and sedation.

Atrial fibrillation– uncoordinated ineffective activity by multiple staff members acting independently. Induced by overfilling of the ambulance bay, because of increasing off-load pressure.

Coronary artery plaques– poor recruitment or HR practices resulting in constricted flow of ‘fresh blood’ (medical and nursing staff) to supply the department, leading to the rapid development of pain (see Angina) and/or chronic departmental failure.

Dilated cardiomyopathy– contractility decreases if ventricles expand in size. A similar phenomenon occurs in all growing EDs as physical size and workload increases. Communication, efficiency and ability to manage deteriorate.

Aortic stenosis– a chronic condition occurring after 17.00 hours Monday to Friday, when inpatient team presence reduces by 90%, resulting in a large pressure gradient between the ED and wards, with critical flow reduction. A condition only resolved by major surgery. Many such departments are deemed not fit for surgery and are palliated with conservative measures.

Constrictive cardiac failure– ventricular size and contractility decreasing due to either external pressures when other departments crowd on ED space (tamponade), or internal space pressures.

Jugular venous pressure– visible ‘wave’ of ambulances on the ramp outside ED as a result of congestive failure within.

Thrombus formation– bed blocked patients pooling in poorly contracting departments form large immobile space-occupying clots that tie up departmental space and increase the risk of a departmental adverse event. Can be induced with Atrial fibrillation (see above) but does not occur in free flowing departments.

Inotropic support– might be required when contractility reaches critically low levels. As in other areas of medicine, evidence to choose between different available inotropes is equivocal, and one might choose from alpha agonists such as staff recruitment and retention, beta-agonists such as retraining and locums, and novel agents such as work practice review.

Negative inotrope– new procedure or personnel introduced into the system usually with the intent of improving function but which actually decreases output.

LVAD– an assistance device to drive patients through the department. Can come from improved management or clinical imperatives (such as the 4 h national access target).

ECMO– an external device to bypass patients from the ED and stream patients directly to other areas of the hospital for management, such as mobile home assessment units. An advance on ambulance bypass as it directly moves patients into the hospital system rather than putting the load into another hospital.

Artificial valves– devices, such as operational protocols, that prevent patients from moving backwards or becoming stuck in the ED (see Thrombus formation). Pathological valves can either be regurgitant (with patients pushed backward into the waiting room) or obstructive (a common descriptor for admitting registrars).

Defibrillation–‘kick-start’ that resuscitates a moribund ED. Exceedingly rare but has been documented when an external disaster response creates space on the inpatient wards and the ED empties of thrombus.

Septal defect– barrier in the ED that becomes porus allowing patients and their care to ‘leak’ into the wrong place (e.g. patients being treated in corridors, stable patients in the resus room).

We hope that the extended EDCAM concept will lead to better understanding of the pathological processes occurring in modern EDs and increase the possibility of improved treatments (positive inotropes).

Competing interests

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None declared.


  1. Top of page
  2. Competing interests
  3. Reference
  • 1
    Richardson SK, Ardagh M, Gee P. Emergency department overcrowding: the Emergency Department Cardiac Analogy Model (EDCAM). Accid. Emerg. Nurs. 2005; 13: 1823.