Difference between ventricular tachycardia and supraventricular tachycardia on ecg
Difference between ventricular tachycardia and supraventricular tachycardia on ecg Ventricular tachycardia (VT) and supraventricular tachycardia (SVT) are two common types of rapid heart rhythms that cardiologists frequently encounter. While both conditions involve an abnormally fast heartbeat, their origins, mechanisms, and characteristic features on an electrocardiogram (ECG) significantly differ, which is crucial for accurate diagnosis and effective management.
Ventricular tachycardia originates from abnormal electrical activity within the ventricles—the heart’s lower chambers. It typically presents as a rapid, broad-based rhythm on the ECG, with heart rates often exceeding 100 beats per minute. The hallmark of VT on an ECG is the presence of wide QRS complexes, usually greater than 120 milliseconds, occurring at a regular rhythm. These wide complexes are due to abnormal conduction pathways within the ventricles, causing the electrical impulses to bypass the normal conduction system. In some cases, VT can be monomorphic, where the QRS complexes look similar from beat to beat, or polymorphic, where the morphology varies. Patients may experience symptoms such as dizziness, palpitations, or even syncope, especially if the VT is sustained or degenerates into ventricular fibrillation.
In contrast, supraventricular tachycardia originates above the ventricles, typically in the atria or at the atrioventricular (AV) node. On the ECG, SVT is characterized by narrow QRS complexes, generally less than 120 milliseconds, due to normal ventricular conduction pathways. The heart rate in SVT usually ranges from 150 to 250 beats per minute. The hallmark feature is the presence of rapid, regular rhythm with absent or indistinct P waves because the atrial activity often overlaps with the QRS complex, making them difficult to discern. The onset and termination of SVT are usually sudden, often triggered by premature atrial or AV nodal impulses.
One of the key differences between VT and SVT on ECG is the width of the QRS complexes. Wide QRS complexes suggest ventricular origin, pointing towards VT, whereas narrow complexes indicate supraventricular origin. However, sometimes VT can be difficult to distinguish from SVT with aberrant conduction, especially if the ventricles are conducting abnormally, such as in bundle branch block. Additional clues include the morphology of the QRS complexes, AV dissociation (where atrial and ventricular activities are independent) seen more commonly in VT, and the presence of fusion or capture beats.
Correctly identifying whether a tachycardia is ventricular or supraventricular is vital because the treatment approaches differ markedly. VT may require antiarrhythmic drugs, implantable defibrillators, or urgent cardioversion, especially if the patient is unstable. SVT, on the other hand, often responds well to vagal maneuvers, adenosine, or other medications targeting the AV node.
In conclusion, while VT and SVT can present with similar rapid heart rates, their ECG features are distinctive. Recognizing the width of QRS complexes, the regularity of rhythm, and specific features such as AV dissociation helps clinicians differentiate between these two arrhythmias, ensuring timely and appropriate treatment.
