[Invasive and non-invasive methods for the diagnosis of tachycardia]

Surface ECG permits, in most cases, to determine the ventricular or supraventricular origin of a tachycardia with wide complexes, to individualize VTs with aspects of Left Buble Branch and left axis, to visualize epsilon waves in some chronic VTs. The late potentials detected by the sum-mean method seem to be well correlated with the occurrence of ventricular tachycardia, especially after myocardial infarction. The area of origin of a VT may be determined quite precisely by cartography and topographic stimulation. The predictive value of the provocation methods (stress test, transesophageal stimulation, endocardiac stimulation) is discussed. Some arrhythmias may be discovered on ultrasonic cardiography and the exact mechanism of some reciprocal permanent junctional tachycardias is well demonstrated with endocardiac stimulation and fulguration. Nuclear magnetic resonance offers a new possibility of etiological diagnosis in ventricular tachycardias with left delay.