The supraventricular tachycardia ecg changes
The supraventricular tachycardia ecg changes Supraventricular tachycardia (SVT) is a rapid heart rhythm originating above the ventricles, primarily involving the atria or the atrioventricular (AV) node. It is a common arrhythmia characterized by episodes of sudden-onset, rapid heartbeats that can be alarming and sometimes distressing for patients. One of the primary diagnostic tools for identifying SVT is the electrocardiogram (ECG), which reveals distinct patterns and changes that help clinicians distinguish it from other arrhythmias.
On a standard ECG, SVT typically presents with a narrow QRS complex, generally less than 120 milliseconds, indicating that ventricular conduction is normal. The hallmark feature is a rapid heart rate, usually between 150 and 250 beats per minute. Because of the increased rate, the P waves—representing atrial depolarization—may be obscured or hidden within the preceding T wave due to the rapid succession of beats. As a result, the classic P wave morphology may be difficult to discern, and in many cases, it appears as a small, pseudo R’ in V1 or as a pseudo S in inferior leads.
The QT interval in SVT often appears shortened or normal, but it can vary depending on the underlying heart rate and individual patient factors. The PR interval may be difficult to measure accurately because of the fusion of P waves with T waves at high rates or their concealment within the QRS complex. In some cases, especially in atrioventricular nodal reentrant tachycardia (AVNRT)—a common form of SVT—the P waves may appear as retrograde impulses that follow the QRS complex, leading to a characteristic “short PR, with pseudo R’ or pseudo S waves.”
ECG changes during SVT are dynamic and can vary depending on the type, duration, and the patient’s response to the arrhythmia. During episodes, the ECG will demonstrate a regular, narrow-complex tachycardia with a consistent rate. The morphology of the QRS complex remains narrow unless aberrant conduction occurs or pre-existing bundle branch blocks are present. In some cases, especially with AV reciprocating tachycardia involving accessory pathways, delta waves or pre-excitation patterns may be evident during sinus rhythm, but these are typically absent during SVT episodes.
Identification of specific ECG features allows clinicians to differentiate SVT from other tachyarrhythmias such as ventricular tachycardia or sinus tachycardia. A key aspect is the regularity, narrow QRS complexes, and the absence of visible P waves in some cases. The response to vagal maneuvers or adenosine, which temporarily blocks AV nodal conduction, often results in the termination of the SVT, further confirming the diagnosis. Post-episode ECG may be normal, but a detailed analysis during the arrhythmia is crucial for definitive diagnosis.
In summary, ECG changes in supraventricular tachycardia include a narrow QRS complex, a rapid and regular heart rate, and often concealed or pseudo P waves. Recognizing these features is vital for accurate diagnosis and management, allowing appropriate interventions such as medication, vagal maneuvers, or catheter ablation to effectively control or eliminate episodes.
