The no reflow phenomenon in the coronary arteries.

In the last twenty years, the treatment of coronary heart disease with cardiac catheterization has greatly advanced. This therapeutic approach has had unexpected side effects, however, for which solutions must be found, particularly in the are of interventional cardiology. The “noreflow” phenomenon, a side effect, is an uncommon and critical occurrence and, if not reversed, causes a high rate of morbidity and mortality. Its most intriguing clinical characteristic perhaps is its unpredictability. Kloner and co-workers 1 first described the “noreflow” phenomenon in 1974 in dogs with experimentally induced myocardial infarction. The coronary arteries of these dogs were occluded for 40 or 90 minutes, and after that, they were reperfused and studied by means of contrast medium injection. In the coronary arteries occluded for 40 minutes, there was uniform reperfusion of the ischemic myocardium; however, in those occluded for 90 minutes, there was no reperfusion after removal of the coronary occlusion. These investigators concluded that the absence of flow was an ischemic phenomenon, related to the duration of coronary occlusion, which resulted in muscle injury and death of myocardial cells . Later, “no-reflow” was observed in patients who experienced short periods of ischemia and coronary reperfusion with thrombolytic agents 2 and, more recently, in different types of coronary interventions with catheter . This phenomenon was also observed in other organs, such as the skin, kidneys and brain, where ischemia occurred . The “no-reflow” phenomenon can be defined as an acute and severe reduction of coronary flow (TIMI 0 to 2)* after removal of an arterial occlusion, in the absence of spasm, thrombi, severe residual lesions, and arterial dissection. It is not to be confused with slow flow, which is a much less critical situation that is more frequently observed and usually reversible. “No-reflow,” when visualized by angiography, appears as a column of contrast medium with slow back and forth movements inside a vessel usually close to the site of the treated lesion without progression of the contrast medium to the distal portion of the coronary artery. When coronary blood flow velocity is analyzed by Doppler flow-wire, retrograde systolic flow, reduction of anterograde systolic flow and fast deceleration of diastolic flow caused by the “no-reflow” phenomenon can be observed .