The V-beam laser is a type of pulsed dye laser (long pulse) designed to treat vascular lesions such as port wine stains or the skin vessels of rosacea. Tiny visible facial veins, called telangiectasias, are also effectively treated by this laser, though other lasers, like the KTP, work as well or better in some situations and patients. Normal skin veins are both too large and too deep to even be affected by a V-beam, pulsed dye, or KTP laser. Normal skin vessels are not affected at all by any of these lasers, which emit light in visible wavelengths, not any kind of ionizing radiation. Other than a burn or blister (which could leave a scar), these lasers do not penetrate like industrial lasers or the laser beams of science fiction or the phasers of Star Trek!
Pulsed dye lasers work by emitting laser energy at a 585nm (yellow) wavelength that happens to correspond to an absorption peak of oxyhemoglobin. This means that this color of laser energy is preferentially absorbed by oxygenated blood, which of course is what is in our blood vessels (even veins). The V-beam laser is one kind of pulsed dye laser that operates at or near this same wavelength and has selectable shutter durations and power settings.
Blood vessel abnormalities such as port wine stains are actually capillary malformations, or abnormal dilations of capillaries close to the surface of the skin. The color of the port wine stain (pink to salmon-red to purple) relates to the flow rates (and subsequent absorption of the oxygen bound to the hemoglobin molecules) within these tiny vessels. Rosacea is a skin condition characterized by sebaceous hyperplasia, skin thickening, dilated vessels, and often certain kinds of intra-follicular bacteria.
Same dilated surface capillaries, different cause. Same treatment (as far as the vessels are concerned).
Neither condition has "broken" vessels, and in fact this is a lay term that is incorrect medically, but often used by physicians because that is the terminology patients use. These vessels are (more) visible because they are dilated, not "broken."
To destroy these dilated vessels enough energy needs to be absorbed by the vessel to do one of two things, preferably without damaging the normal skin structures.
The vessel absorbs enough energy to actually burst, releasing a blush of blood (the bruise) which demonstrates the capillaries in that laser spot received adequate energy to be destroyed. The pulse of energy is timed so that the laser shuts off so fast, heat damage is minimized to other tissues. This combination of proper energy for a specific duration is dependent on vessel diameter, and is termed the thermal relaxation time. Of course, depth of vessel is also important, but these laser wavelengths penetrate only about a millimeter or so before all the energy is absorbed, especially by a port wine stain or the dilated capillaries of rosacea. The bruise takes about two weeks to go away, just like a black eye.
The vessel heats up more slowly and the vessel spasms and the blood is actually constricted away from the vessel. This occurs when the energy is applied slowly, rather than in the half of a thousandth of a second that the pulsed dye laser beam duration is. The vessel (hopefully) heals shut permanently.
A V-beam laser is a long-pulse pulsed dye laser, with shutter durations which can be twice to as much as 20 times the shutter duration (1-10 milliseconds) of the "standard" pulsed dye laser (450 microsecond shutter duration). Typically, this will be enough energy to cause a bruise (bursting) of only a few of the capillaries in a port wine stain or rosacea blush, since usually these energies cause the vessels to heat up and spasm rather than burst. So, a bruise is not necessary, but if it occurs, it always signifies that at least some of the offending vessels have been properly damaged and will now be gone! The V-beam laser can cause enough thermal damage to blister and scar skin, so proper energy selection is important.
Depending on the size (diameter) and flow rates of the vascular lesion to be treated, V-beam is more nonspecific than the short-duration pulsed dye laser, which is specifically designed to treat the type and diameter of the vessels in port-wine capillary malformations. BTW, pulsed dye laser treatment of larger vascular lesions such as venous malformations or hemangiomas is generally not effective, since the target size of the vessel is too large for the energy and pulse duration of this laser. V-beam treatment may be more effective, or other recommendations need be considered. (Outside the scope of this discussion.)
So, bruising is a normal response to laser treatment of these kinds of surface capillaries; bruising DOESN'T "help" the treatment be more effective. It is simply a sign that the capillaries that you want destroyed burst and can be considered "gone." The absence of bruising doesn't mean that the treatment was ineffective, but it COULD mean that. It's all in the energy, the vessel size, the depth and flow rates of the vessels, and therefore the skill and experience of the doctor choosing the laser type, settings, and usage. It's not about laser brand names either.
Select a laser surgeon who knows enough science to answer questions like this, not just what they point the laser beam at, and the statement that "It works great for ___________!" Best wishes!