Medical and surgical devices and instruments, namely, steam-based catheters for the ablation, cauterization and hemostasis of cardiac tissue and/or associated veins or venous structures; Medical and surgical devices and instruments, namely, steam-based catheters for the ablation and isolation of pulmonary veins from the heart; disposable kits for use with water heating systems that include catheters, heating elements and a water source; Medical devices, namely, water heating systems specially adapted for generating and delivering steam through a catheter