A coronary sinus catheter for the retrograde infusion of cardioplegia solutions into the coronary sinus. The catheter is adapted for improved retention in the coronary sinus. The catheter comprises a catheter tube having infusion, pressure-sensing and balloon-inflation lumens, an inflatable balloon and a pressure sensor tube in fluid communication with the balloon-inflation lumen for sensing pressure in the inflatable balloon. The internal volume of the pressure sensor tube is relatively non-expansible relative to the internal volume of the inflation balloon in normal operation of the catheter. Other aspects of the invention include a constricted portion in the infusion lumen that is believed to eliminate spraying of fluid through the infusion lumen outlet(s), and a temperature sensor strip providing a display on the catheter of the temperature of the infused fluid.