Recanalization of chronically occluded coronary arteries.

A chronic coronary occlusion consists of an atherosclerotic plaque and one or several thrombi. It clinically imitates a tight stenosis but is exempt from the risk of truly unstable angina or myocardial infarction. Hence, quality of life is at stake and not longevity. This holds true for balloon angioplasty as well as for surgery. Indications for angioplasty are based on an estimate of technical difficulties and clinical risks balanced against potential subjective benefit and amount of viable myocardium concerned. An occlusion flush at the orifice of the vessel, tapering into a small sidebranch, with bridging collaterals, or devoid of collaterals is no target for angioplasty. Primary success is around 65% and complications are extremely rare. Abrupt vessel closure is common but harmless. No Q-wave infarctions have been reported in that context. The need for emergency bypass surgery may arise from acute closure of a vessel proximal to the occlusion in an exceptional case. Duration and length of occlusion are the most important predictors of success. Recurrence averages 62% (17% reocclusion and 45% restenosis). An important factor for the high recurrence rate is the competitive pressure exerted by the collaterals on standby. Recurrence happens almost exclusively within the first six months. It is innocuous but produces symptoms prompting further interventions (repeat angioplasty or bypass surgery). The conventional technique uses a stiff guidewire and advances the balloon catheter close to the tip of the guidewire for additional rigidity. New technologies are under investigation but no breakthrough has happened so far. They encompass blunt mechanical instruments (e.g., Magnum wire), drills of various velocities, laser energy applied directly to the tissue (some angioscopically guided, some triggered by on-line spectral tissue analysis), catheters dispersing laser energy through a sapphire or converting it into heat (hot tip), and electrical or radiofrequency heat applicators. As low-yield procedures had better be low-risk and low-cost, there are definite limits to how sophisticated, complicated, risky, and expensive tools and techniques for percutaneous coronary recanalization can become. Close relatives of conventional gear such as the Magnum system offer themselves as first choice equipment complemented, in case of need, by mechanical drills.