Page 274 - ACCCN's Critical Care Nursing

Cardiac Rhythm Assessment

and Management 11

Malcolm Dennis
David Glanville

Learning objectives Key words

After reading this chapter, you should be able to: arrhythmia
● describe the various arrhythmogenic mechanisms sinoatrial
implicated in the development and propogation of cardiac atrial
arrhythmias atrioventricular
● recognise the features of the various commonly observed junctional
arrhythmias and discuss the aetiological factors that ventricular
predispose to the development of each bradycardia
● discuss the actual or potential haemodynamic tachycardia
consequences and prognostic implications of each of the anti-arrhythmic
commonly observed arrhythmia types
● describe the general and specific assessment and treatment pacemaker
strategies applicable to each of the various arrhythmia threshold
types failure to sense
● discuss the principles and indications for pacemaker failure to capture
therapy failure to pace
● recognise abnormal pacemaker activity on ECG and discuss oversensing
the causes and corrective actions for complications during implantable cardioverter defibrillator
temporary pacing antitachycardia pacing
● describe the principles and benefits of cardiac cardiac resynchronisation therapy
resynchronisation therapy (CRT), including the factors ablation
which limit the effectiveness of the therapy cardioversion
● discuss the principles and indications for treatment of
arrhythmias including ablation therapies, permanent
pacing, cardioverter defibrillators, cardioversion and
defibrillation.
compromising arrhythmias is effectively the same as the
outcomes of shock from other aetiologies, and includes
reduced oxygen delivery and consumption, increased
INTRODUCTION oxygen extraction and lactic acidosis. This chapter
describes the major arrhythmias encountered in critical
Many critically ill patients experience cardiac arrhyth- care, their causes, ECG features, impact and management.
mias. These typically compromise cardiovascular perfor- Electrical therapies (temporary pacing, permanent pacing,
mance to a greater or lesser extent and may be temporary, implantable cardioverter defibrillator therapies, arrhyth-
recurrent, or permanent. Symptomatic impact ranges mia ablation procedures and external cardioversion) are
from lethargy, exercise intolerance, dyspnoea, lighthe- described, along with their electrocardiographic and
adedness and palpitations, to marked haemodynamic clinical assessments and patient management.
instability and syncope. Brady-asystolic arrhythmias and
tachyarrhythmias may present as, or progress to, cardiac THE CARDIAC CONDUCTION SYSTEM
arrest. Physiological effects of tachyarrhythmias include
increased myocardial oxygen demand at the same time The normal heartbeat sequence occurs through rhythmic
that reduced oxygen delivery is occurring, with scope for stimulation of the heart via its specialised conduction
resultant myocardial ischaemia. The metabolic impact of system. The sinoatrial node, located superiorly in the 251