Electrophysiologic Properties of Furosemide in Man

Furosemide has been extensively used in the treatment of heart failure and its effect on cardiovascular dynamics are well established.1Clinical relief of the symptoms of pulmonary congestion frequently precedes any demonstrable diuretic effect, suggesting that extra renal factors may also be involved.2More recent studies on the extra-renal action of furosemide showed an increase of venous capacitance as an early hemodynamic effect of the drug.3 In spite of furosemides wide use in the treatment of heart failure and hypertension, there is no information on the electrophysiologic properties of the drug in man. The present study involving 8 human subjects was undertaken to determine what effect intravenously administered furosemide has on the human conduction system. Material and Methods The study group consisted of 8 patients with organic heart disease. The clinical features of the group are summarized in Table I. All patients were informed of the nature of the study and gave informed consent. They were studied in the supine position in a post-absorptive, non-sedated state. Under local anesthesia, a quadripolar electrode catheter was introduced percutaneously into the right antecubital vein and fluoroscopically positioned against the lateral wall of the high right atrium near its junction with the superior vena cava. The distal pair of electrodes was used to stimulate the atrium while the proximal pair was used to record a high right atrial electro-gram. In addition, a bipolar pacing catheter was introduced percutaneously into the right femoral vein and fluoroscopically positioned at the tricuspid valve. The position was adjusted to obtain optimal recordings of the His bundl