Ecg findings in supraventricular tachycardia
Ecg findings in supraventricular tachycardia Supraventricular tachycardia (SVT) encompasses a group of arrhythmias originating above the ventricles, characterized by rapid heart rates that can cause symptoms such as palpitations, dizziness, and shortness of breath. Accurate interpretation of electrocardiogram (ECG) findings is crucial for diagnosis, management, and understanding the underlying mechanisms of SVT.
Ecg findings in supraventricular tachycardia On the surface, the ECG during SVT typically displays a narrow QRS complex tachycardia, generally less than 120 milliseconds in duration, indicating that ventricular depolarization proceeds via the normal His-Purkinje system. The heart rate usually ranges from 150 to 250 beats per minute. The regularity of the rhythm is a key feature, with consistent RR intervals, although some forms may demonstrate variability.
One of the hallmark features seen on ECG in typical SVT, especially atrioventricular nodal reentrant tachycardia (AVNRT), is the presence of P waves that are either buried within the QRS complex or appear as pseudo R’ or pseudo S waves. In AVNRT, the reentrant circuit involves the AV node, leading to a nearly simultaneous atrial and ventricular depolarization. This results in P waves often being hidden within the QRS complex or appearing just after it, sometimes leading to a short RP interval (less than 70 milliseconds). In contrast, atypical AVNRT may show longer RP intervals, with P waves visible after the QRS complex. Ecg findings in supraventricular tachycardia
Ecg findings in supraventricular tachycardia In atrioventricular reentrant tachycardia (AVRT), which involves an accessory pathway, the ECG may reveal a similar narrow complex tachycardia with P waves that are often difficult to discern. The presence of delta waves during sinus rhythm (pre-excitation) can suggest Wolff-Parkinson-White (WPW) syndrome, which predisposes to AVRT. During tachycardia episodes in WPW, the ECG may display a short PR interval, delta waves, and a widened QRS complex that resembles a bundle branch block pattern, reflecting pre-excitation.
Distinguishing SVT from other wide complex tachycardias is essential. While most SVTs are narrow complex, some may appear wide due to aberrant conduction or pre-existing bundle branch block. In such cases, the ECG may show wide QRS complexes with a regular rhythm, necessitating careful analysis to differentiate from ventricular tachycardia.
Ecg findings in supraventricular tachycardia Another key aspect is the response to vagal maneuvers or adenosine administration. Adenosine, which transiently blocks AV nodal conduction, is often both diagnostic and therapeutic. During AVNRT or AVRT, administration of adenosine typically results in sudden termination of the tachycardia, restoring sinus rhythm. The ECG after adenosine may reveal underlying atrial activity or P waves that were previously obscured.
In summary, the ECG findings in SVT are characterized by a narrow QRS complex tachycardia with a rapid, regular rhythm, P wave positioning that varies depending on the type of SVT, and specific features such as short RP intervals in AVNRT. Recognizing these patterns is vital for accurate diagnosis and guiding appropriate treatment strategies, which may include vagal maneuvers, pharmacotherapy, or interventional procedures like catheter ablation. Ecg findings in supraventricular tachycardia
