ICU · Equipment, physics & clinical measurement
ECG & Electrical Safety
Also known as ECG · Electrocardiogram · Electrical safety · Microshock · Macroshock · Line isolation monitor · Equipotential earthing · CF equipment
ECG and electrical safety for the ICU First Part: how the 12-lead ECG records cardiac potentials (Einthoven's triangle, limb and precordial leads, electrical axis), the signal path and filtering, and the principles of electrical safety - macroshock vs the much lower microshock threshold when current reaches the heart through a central line, and the protective measures (isolation, equipotential earthing, CF equipment).
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Meet the patient
A 64-year-old man, day 3 after an out-of-hospital arrest, has a right internal jugular central line whose tip lies in the right atrium, a transvenous pacing wire for intermittent complete heart block, and a noradrenaline infusion. He is connected to the bedside ECG monitor, a pressure transducer and a fluid warmer. The line-isolation monitor at the bedside suddenly alarms, and the nurse asks whether to silence it.[1]
Two First-Part competencies collide at this bed. The first is reading the monitor — recognising the paced rhythm, the capture and sensing, the ischaemia that may be hiding under the pacing spikes. The second is electrical safety — understanding why this patient, with a direct conductive path to his myocardium, is a microshock candidate, and why silencing that alarm without finding the fault could kill him. Both halves of this topic live at the same bedside.[1]
References5ShowHide
- [1]Thygesen K, Alpert JS, Jaffe AS, et al. Fourth universal definition of myocardial infarction (2018) Eur Heart J, 2019.PMID 30165617
- [2]Sgarbossa EB, Pinski SL, Barbagelata A, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators N Engl J Med, 1996.PMID 8559200
- [3]Mitani Y, Ohashi H, Sawada H, et al. In vivo plaque composition and morphology in coronary artery lesions in adolescents and young adults long after Kawasaki disease: a virtual histology-intravascular ultrasound study Circulation, 2009.PMID 19451352
- [4]Koga Y, Tomita M, Shibata K, et al. Pacemaker implantation in a neonate with congenital complete heart block--a case report Jpn J Surg, 1982.PMID 7069946
- [5]Brugada P, Brugada J Right bundle branch block, persistent ST segment elevation and sudden cardiac death: a distinct clinical and electrocardiographic syndrome. A multicenter report J Am Coll Cardiol, 1992.PMID 1309182