Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 103

This common arrhythmia is characterised by the rapid and uncoordinated contraction of the atria (fibrillation) which can reduce ventricular filling. Since the atria are only responsible for the last 33 per cent of ventricular filling, symptoms of AF such as weakness, dizziness or breathlessness may only be experienced during exercise or periods of excitement when cardiac output increases. Some individuals may never experience symptoms even with long-standing AF and are only diagnosed following a routine check-up. During periods of sustained AF the uncoordinated irregular contractions cause turbulent blood flow, allowing blood to collect in the atrial recesses, particularly in the left atrial appendage. This static blood can remain for long periods and begin to coagulate, resulting in a progressively enlarging clot (thrombus).

At any time, these thrombi can embolise and travel up into the cerebral circulation, resulting in stroke. If only small clots are dislodged then transient ischaemic attacks (TIAs) may occur, but if clots forming in the left atrial appendage are large and embolise, major cerebral vessels may be occluded, leading to severe CVAs that may be fatal. It has been estimated that the risk of thromboembolic stroke increases around fivefold in patients with persistent AF (Wolf et al., 1991), and so to minimise risk these patients are usually placed on long-term anticoagulation therapies such as warfarin or apixaban.

AF is commonly seen in patients with coronary artery disease or in those that have previously suffered MI; however, age is recognised as the major risk factor for developing AF (Steenman and Lande, 2017). AF is readily diagnosed by reference to a patient’s ECG where the presence of multiple P waves and an irregular heart rate are commonly observed. Since AF is so frequently encountered by nurses, to further your understanding of this important arrhythmia read through Gerald’s case study before attempting Activity 3.2.