The paroxysmal supraventricular tachycardia ecg features
The paroxysmal supraventricular tachycardia ecg features Paroxysmal supraventricular tachycardia (PSVT) is a common arrhythmia characterized by sudden episodes of rapid heart rate originating above the ventricles. Recognizing its electrocardiogram (ECG) features is essential for accurate diagnosis and effective treatment. PSVT episodes are often abrupt in onset and termination, which can sometimes make their identification challenging without careful ECG analysis.
One of the hallmark features of PSVT on an ECG is a narrow QRS complex, typically less than 120 milliseconds, indicating that the conduction pathway involves the normal His-Purkinje system rather than abnormal ventricular pathways. During an episode, the heart rate usually ranges from 150 to 250 beats per minute, resulting in a rapid, regular rhythm. This high rate often leads to the merging or loss of distinct P waves, making the atrial activity difficult to distinguish from the ventricular activity.
In many cases, P waves are either hidden within the QRS complex or appear immediately after it, producing a pseudo R’ or pseudo S wave pattern. When visible, P waves may be seen in the inferior leads (II, III, aVF) or sometimes in the V1 lead, but their morphology often resembles retrograde atrial activation, indicating that the atria are activated from an abnormal pathway or via retrograde conduction through the AV node. This retrograde P wave typically appears after the QRS complex, in the ST segment or early T wave, creating a characteristic short RP interval—usually less than 70 milliseconds.
The T wave in PSVT often appears normal, but in some cases, it may be inverted in the inferior leads if retrograde conduction is prominent. The presence of a rapid, regular rhythm with a narrow QRS complex, combined with the short RP interval and retrograde P waves, is highly suggestive of PSVT. The sudden onset and termination of episodes are also distinguishing features, often triggered by premature atrial or ventricular beats.
Another important ECG feature is the absence of visible P waves in many cases during the tachycardia, which can sometimes be confused with other forms of supraventricular tachycardia. However, the key to differentiating PSVT lies in the short RP interval and the regularity of the rhythm. In some cases, vagal maneuvers or adenosine administration can transiently slow or terminate the arrhythmia, confirming the diagnosis. Adenosine temporarily blocks AV nodal conduction, revealing the underlying atrial activity and helping distinguish PSVT from other arrhythmias, such as atrial flutter or atrial fibrillation.
Understanding these ECG features is crucial for clinicians, as they influence management strategies. Accurate identification allows for prompt intervention, whether through vagal maneuvers, pharmacologic therapy, or electrical cardioversion if necessary. Recognizing PSVT’s characteristic ECG features ensures appropriate treatment and reduces the risk of complications associated with misdiagnosis or delayed therapy.
