Category: Fundamentals
Premature atrial contractions (PACs) are common and usually have little clinical significance. PACs are abnormal P waves early in a cardiac cycle. Sometimes, the P wave may be difficult to detect if it is buried within the preceding T wave.
Category: Fundamentals
The hallmark of third-degree AV block, also known as complete heart block, is AV dissociation (no electrocardiographic relationship between P waves and QRS complexes), with an R-R interval longer than the P-P interval.
Category: Fundamentals
Type II second-degree AV block is a conduction block just below the level of the AV node. On the ECG, conduction of atrial impulses is sporadic and typically periodic, but the PR interval does not widen from beat to beat.
Category: Fundamentals
Type I second-degree AV block, is associated with progressive impairment of conduction within the AV node. The ECG shows a lengthening of the PR interval from beat to beat until a P wave is entirely blocked (so-called dropped beat).
Category: Fundamentals
First-degree AV block is from prolonged conduction at the level of the atria, AV node (most common), or His-Purkinje system. On the ECG, first-degree AV block shows a prolonged PR interval (> 0.20 second).
Category: Fundamentals
AV block results from impaired conduction through the atria, AV node or proximal His-Purkinje system. First- and second-degree AV blocks represent partial impairment, whereas third-degree block indicates complete interruption.
Category: Fundamentals
Sick sinus syndrome is a group of dysrhythmias caused by disease of the sinus node and its surrounding tissues, creating sinus bradycardia, sinus arrest or SA exit block. Long-term management requires permanent pacemaker placement.
Category: Fundamentals
Sinus dysrhythmia is a display of variation in heart rate that occurs during the respiratory cycle, manifested as normally conducted P waves with a variable P-P interval. It is a normal variant and is seen frequently in children and young adults.
Category: Fundamentals
Sinus bradycardia is often asymptomatic and requires no specific treatment. If needed, first-line treatment for symptomatic sinus bradycardia in adults is atropine, a 0.5 mg IV bolus, repeated as needed every 3-5 minutes, to a total dose of 3 mg.
Category: Fundamentals
Sinus bradycardia is characterized by a P wave with normal morphology, a fixed P-P interval equal to the R-R interval, and a ventricular rate below 60 beats/min. This pattern may be found in healthy individuals.
Category: Fundamentals
Bradycardia is defined as a ventricular rate of less than 60 beats/min, although in practice rates above 50 beats/min are not usually a concern. Bradycardia occurs because of depression of the sinus node or because of a conduction system block.
Category: Fundamentals
Vagal maneuvers, such as carotid sinus massage and the Valsalva maneuver, transiently slow AV conduction, which may help terminate or uncover a supraventricular rhythm disturbance.
Category: Fundamentals
The 12-lead ECG is essential to evaluating any patient with a suspected dysrhythmia. Use of a single ECG lead is often adequate for diagnosis, especially in unstable patients. Multiple leads are optimal in stable patients.
Category: Fundamentals
Adenosine is a naturally occurring purine nucleoside that is the best choice for the termination of regular, nonatrial, narrow-complex tachydysrhythmias. Adenosine has an onset of action of 5 to 20 seconds and a duration of effect of 30 to 40 seconds.
Category: Fundamentals
Digitalis compounds have a variety of effects on myocardial cells. Digoxin inhibits the adenosine triphosphate (ATP) dependent Na+-K+ exchange pump, increasing intracellular Na+ concentrations and decreasing intracellular K+ concentrations.
Category: Fundamentals
Long-term amiodarone use is associated with extracardiac side effects, including irreversible lung and thyroid disease. Amiodarone alters the pharmacokinetics of numerous other drugs, including digoxin and warfarin.
Category: Fundamentals
Amiodarone is used for the treatment of ventricular and supraventricular dysrhythmias. The serum half-life of amiodarone is 25 hours after a single IV dose and up to 50 days during long-term oral use.
