The clinical and electrocardiographic differentiation of supraventricular and ventricular tachycardias with regular rhythm

Abstract

1. 1. The differentiation of a supraventricular from ventricular tachycardia can usually be made by careful bedside auscultation, if particular care is paid to splitting of the heart sounds. 2. 2. In a case of rapid regular tachycardia, if the first and second sounds are single or normally split, the diagnosis of supraventricular tachycardia can be made with confidence, and ventricular tachycardia can be excluded with confidence. 3. 3. In a case of rapid regular tachycardia, if there is wide splitting of both sounds, ventricular tachycardia is usually present. 4. 4. In a case of rapid regular tachycardia, if there is wide splitting of both sounds, variation in the intensity of the first sound and independent, irregular “Cannon A” waves in the jugular venous pulse, the diagnosis of ventricular tachycardia can usually be made with confidence. 5. 5. The wide splitting of both heart sounds is a manifestation of ventricular asynchrony; the variation in the intensity of the first sound and the independent, irregular “Cannon A” waves is a reflection of auriculoventricular dissociation. 6. 6. Supraventricular tachycardia with bundle branch block, ventricular tachycardia with auricular fibrillation and ventricular tachycardia with retrograde conduction are all rare conditions, in which ventricular asynchrony occurs without auriculoventricular dissociation. Wide splitting of both heart sounds without variation in the intensity of the first sound is therefore encountered. Differentiation is difficult but can be made by careful study, as discussed. 7. 7. The great value of the esophageal lead in the electrocardiographic diagnosis has been clearly demonstrated. 8. 8. In a case of rapid regular tachycardia, if the electrocardiogram reveals a QRS interval of normal duration, the diagnosis of supraventricular tachycardia is established. Auricular activity can usually be demonstrated by standard electrocardiograms and esophageal leads are rarely necessary. 9. 9. In a case of rapid regular tachycardia, if the electrocardiogram reveals a widened QRS, supraventricular tachycardia with bundle branch block cannot be differentiated from ventricular tachycardia, unless auricular activity is demonstrated. Whereas clinical evidence of auricular activity can be readily detected, the diagnosis cannot usually be made by the conventional electrocardiogram, as the P waves are often obscured by the widened QRS-T complexes. The esophageal leads, however, will clearly demonstrate P waves and thus overcome this problem. 10. 10. The esophageal lead is essential in the differentiation of supraventricular tachycardia with bundle branch block, ventricular tachycardia with independent auricular activity, ventricular tachycardia with retrograde conduction, and ventricular tachycardia with auricular fibrillation. 11. 11. The same clinical features that help to differentiate supraventricular tachycardia from ventricular tachycardia help to differentiate auricular from ventricular premature systoles.