With radiotelemetry either systemic arterial pressure or pulmonary artery pressure or both simultaneously can be measured, which allows testing of all groups of patients with cardiovascular diseases. The telemetry system also allows simultaneous assessment of ECG, which in patients with arrhythmias reveals the hemodynamic effects of ectopic beats. For radiotelemetry of blood pressure the microcatheter (Leadercath system) is introduced by a modified Seldinger technique into the brachial or femoral artery. The pressure transducer (Statham type P 23 and SP 37) is mounted extracorporeally as close as possible to the right atrium.