| I. Physiologic sinus tachycardia Defining feature: normal sinus mechanism precipitated by exertion, stress, concurrent illness (Table 242-1) II. Pathologic supraventricular tachycardia A. Tachycardias originating from the atrium Defining feature: tachycardia may continue despite beats that fail to conduct to the ventricles, indicating that the AV node is not participating in the tachycardia circuit 1. Inappropriate sinus tachycardia Defining feature: tachycardia from the normal sinus node area that occurs without an identifiable precipitating factor as a result of dysfunctional autonomic regulation 2. Focal atrial tachycardia (AT) Defining feature: Regular atrial tachycardia with defined p wave; may be sustained, nonsustained, paroxysmal, or incessant. Frequent sites of origin occur along the valve annuli of left or right atrium, pulmonary veins, coronary sinus musculature, superior vena cava 3. Atrial flutter—macroreentrant atrial tachycardia Defining feature: organized reentry creates organized atrial activity, commonly seen as sawtooth flutter waves at rates typically faster than 200 beats/min a. Common atrial flutter i. Right atrial reentry parallel to the tricuspid annulus and dependent on conduction through the isthmus between the inferior vena cava and tricuspid annulus 1. Counterclockwise (as viewed from the ventricular aspect) 2. Clockwise b. Atypical atrial flutter i. Usually due to reentry in left or right atrium associated with scars usually from prior surgery or catheter ablation for atrial fibrillation, but may be idiopathic 4. Atrial fibrillation Defining feature: chaotic rapid atrial electrical activity with variable ventricular rate; the most common sustained cardiac arrhythmia in older adults 5. Multifocal atrial tachycardia Defining feature: multiple discrete p waves often seen in patients with pulmonary disease during acute exacerbations of pulmonary insufficiency B. AV nodal reentry tachycardia (AVNRT) Defining feature: paroxsymal regular tachycardia with P waves visible at the end of the QRS complex or not visible at all; the most common paroxysmal sustained tachycardia in healthy young adults; ... |