An apparatus for percutaneous laser revascularization of a patient's beating heart includes a laser system that produces a pulsed laser beam with a wavelength in a range of approximately 1.7 .mu.m to approximately 2.15 .mu.m, each pulse of the laser beam having a pulse duration in a range of approximately 1 ms and greater and having a pulse energy in a range of approximately 5 J to approximately 25 J. The pulse can include a train of micropulses. A fiber optic element that is coupled to the laser system is arranged with a catheter to pass through a vasculature of the patient and to deliver pulses of the laser beam to an interior wall of the patient's heart. The laser system can include a flash lamp-pumped laser in which a large capacitor bank discharges only a fraction of its stored energy through a flash lamp to fire the laser, wherein the capacitor discharge is turned off by a switchable device, such as a high current transistor, after the integrated energy of a laser pulse reaches a selected value. A pair of concave mirrors are arranged facing either end of the laser rod to form a resonant cavity, wherein each mirror has a curvature selected to compensate for changes in the index of refraction of the laser rod as a function of radius due to heating from the flash lamp. The laser system can be triggered to provide a laser pulse only during a refractive portion of the patient's heartbeat cycle. The apparatus is capable of forming a channel in the patient's heart to any desired depth by applying only a single laser pulse.