Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 102

Two major types are recognised and are classified according to which chambers are affected. Premature atrial contractions (PACs) occur when there is an early contraction of the atria and can usually be recognised on an ECG as an extra P wave. PACs are minor events and often not even perceived by the patient. Premature ventricular contractions (PVCs) occur as a result of early contraction of the ventricles; these are usually more noticeable to the patient. Often the patient will complain that it feels as if their heart has paused (or lurched) in their chest followed by a more powerful subsequent recovery beat.

Frequently PVCs may be experienced in clusters or in predictable patterns before disappearing and returning hours, days or even months or years later. Since PVCs occur as a result of abnormal conduction in the ventricles, they are more easily recognisable as irregular spikes on an ECG that interrupt the normal sinus rhythm. Most PVCs, while quite scary for the patient, are benign and often related to stress, dehydration or use of stimulants such as caffeine or nicotine. They are also very common in women going through the menopause. When PVCs occur sequentially one after the other, they may develop into more serious arrhythmias such as ventricular tachycardia.