Accelerated Junctional Rhythm Junctional Tachycardia

Premature Atrial Contractions (PACs) Rate: Typically normal Rhythm: Underlying rhythm is typically regular with early premature beats P waves: Atrial depolarization is premature, occurring before the next normal P wave. Since the impulse originates outside the SA node, the P wave may have a different shape - often notched, peaked or buried in the proceeding T wave PR Interval: Maybe normal, shorter or longer than normal PR interval, depending on origin of the PAC QRS Width: typically normal but may be prolonged if the PAC is aberrantly conducted through the ventricles Characteristics: The intrinsic pacemaker of the heart is the sinus (SA) node, and normally it initiates each beat. Pacemaker stimuli can also arise from other parts of the heart – the atria, the AV junction, or the ventricles. The terms “ectopy” or “ectopic beat” are used to describe these non-sinus beats. Ectopic beats are often premature; that is, they come in early or before the next sinus beat is due. A premature atrial contraction results from an ectopic stimulus that arises from somewhere in either the left or the right atrium, but not in the sinus node. The atria are depolarized from the ectopic stimulus, but the remainder of the conduction is typically normal through the AV Node-Junction and downward into the bundle branches (i.e. normal PR and QRS morphology and intervals). Possible Causes: PACs are very common and may occur in persons with a normal heart or in persons with virtually any type of organic heart disease. PACs do not imply that a person has cardiac disease and may be seen with caffeine intake and with emotional stress. Other causes include: Administration of sympathomimeticagents (epinephrine, theophylline; Electrolyte abnormalities; Myocardial ischemia or injury; Digoxin toxicity; Hyperthyroidism Other Types of PACs: There are a few variations from the above description. On occasion, a PAC may not conduct into the ventricles or the PAC may conduct into the ventricles in an abnormal way. Nonconducted PACs: If the PAC occurs very prematurely (or close to the preceding T-wave), the early atrial depolarization might be too early for the right and left bundles to conduct the impulse. This type of PAC cannot be conducted down into the ventricles. In this situation, look for an early P wave (which might also be buried in the preceding T wave). The early PAC does not conduct into the ventricles, thus there is no QRS for this one cardiac cycle. Aberrantly conducted PACs: If the impulse should happen to travel abnormally through the ventricles, the QRS may be prolonged. This can happen if either the right or left bundle branches are not ready to depolarize and result in a temporary block. If the QRS is wide following a PAC, it will be called an aberrantly conducted PAC. Nursing Priorities: Intervention not typically required; Heart rate may be irregular during episodes of PACs so assess the pulse for one full minute Potential Treatments: Asymptomatic: Observation and ECG monitoring for frequency and trends. Explore potential underlying causes (caffeine intake, stress reduction, myocardial abnormalities, etc). Symptomatic: Treatment is typically centered around observation and monitoring for increased frequency. • Be aware that individuals may complain of palpitations or feeling a “skipped” heart beat with an irregular pulse. Explain to them the reason for these feelings. Increased number of PACs may be a forerunner of the development of atrial fibrillation or other atrial dysrhythmias.