Paroxysmal supraventricular tachycardia on ecg
Paroxysmal supraventricular tachycardia on ecg Paroxysmal supraventricular tachycardia (PSVT) is a common form of arrhythmia characterized by sudden episodes of rapid heart rate originating above the ventricles. These episodes can last from a few seconds to several minutes, often resolving spontaneously or with medical intervention. Understanding how PSVT appears on an electrocardiogram (ECG) is essential for accurate diagnosis and appropriate management.
On an ECG, PSVT typically manifests as a sudden onset and termination of a narrow-complex tachycardia, usually with a heart rate ranging from 150 to 250 beats per minute. The hallmark feature is the presence of a regular, rapid rhythm with narrow QRS complexes, indicating that the electrical conduction is through the normal His-Purkinje system. The rapid rate often leads to a loss of the normal P wave morphology, making the P waves difficult to identify or causing them to be hidden within the preceding T wave. When visible, P waves may appear in unusual locations, such as right after the QRS complex or buried within it, depending on the reentrant circuit involved.
The ECG of PSVT often shows a regular rhythm with a short RP interval, meaning that the interval between the R wave and the subsequent P wave is brief. This helps distinguish PSVT from other arrhythmias like atrial flutter or atrial fibrillation. In some cases, the P waves may be inverted in the inferior leads (II, III, aVF) or in lead V1, reflecting atrial activation from an abnormal focus or reentry pathway. The QRS complexes are generally narrow and uniform, unless there is aberrant conduction or pre-existing bundle branch block.
One of the key features in diagnosing PSVT is the abrupt onset and termination of the tachycardia, which may be evident through changes in the ECG tracing. This paroxysmal nature suggests a reentrant mechanism, often involving pathways such as the atrioventricular (AV) node or accessory pathways like in Wolff-Parkinson-White syndrome. The classic ECG pattern may include a “sawtooth” appearance in some cases, especially during atrial flutter, but in PSVT, the rapid, narrow rhythm is the primary feature.
Physicians look for signs of AV nodal reentry or accessory pathway involvement, which can be inferred from the P wave position, morphology, and the relation to QRS complexes. In some instances, vagal maneuvers or adenosine administration can temporarily interrupt the reentrant circuit, causing the ECG to revert to normal sinus rhythm, further confirming the diagnosis.
In summary, the ECG features of PSVT are distinctive yet can be subtle. Recognizing its sudden onset, narrow QRS complexes, rapid and regular rhythm, and typical P wave alterations is crucial for timely and accurate diagnosis. Effective management may involve vagal maneuvers, pharmacologic agents like adenosine, or electrical cardioversion in more severe cases, highlighting the importance of precise ECG interpretation in acute care settings.