Читать книгу Practical Cardiovascular Medicine - Elias B. Hanna - Страница 112

Approximately 15% of occluded arteries acutely recanalize before the PCI procedure, in the first 4 hours, and achieve TIMI 2 or 3 flow (from spontaneous or antithrombotic-induced lysis). This STEMI is called “transient STEMI”, and may also be called “aborted STEMI” if cardiac biomarkers only rise minimally (CK-MB <2× normal).⁹ Residual stenosis usually persists.^60–62

During PCI, the lesion is dilated with balloon angioplasty then stented. In comparison with standalone balloon angioplasty, stenting reduces the early risk of reocclusion/reinfarction by 50% (to <2%) and the late risk of restenosis, without affecting mortality.⁶¹ Drug-eluting stents are used, as they do not increase late stent thrombosis and significantly reduce restenosis.⁶² A routine initial use of aspiration thrombectomy has not shown superiority to balloon angioplasty in two large trials.⁶³

Following primary PCI, ~95% of patients achieve TIMI 3 flow, while 5% achieve TIMI 0–2 flow despite wide macrovascular patency, also called “no reflow.” The term “no reflow” implies poor microvascular flow and is only used after treating all significant epicardial stenoses. TIMI flow <3 is a predictor of poor outcomes, but TIMI 3 flow does not necessarily imply appropriate microvascular flow. In fact, only ~60% of patients with TIMI 3 flow achieve significant ST-segment resolution (= cellular reperfusion), and only 70% achieve appropriate myocardial blush (= microvascular reperfusion).^63,64 “Appropriate myocardial blush,” also called “myocardial blush grade 2 or 3,” is used to describe brisk contrast staining of the myocardium followed by contrast clearance and no residual myocardial stain by the next injection. Impaired coronary flow, impaired myocardial blush, or the lack of ST resolution implies: (i) distal microembolization, (ii) microvascular spasm, or (iii) myocyte injury and swelling from ischemia or reperfusion injury, especially late reperfusion, sometimes irreversible. The best long-term outcomes (survival and LV function) are seen in patients with ST-segment resolution and good myocardial blush, while intermediate outcomes are seen in patients with discordant findings.⁶⁵

Persistent ST elevation after successful primary or rescue PCI implies microvascular obstruction or cellular injury, and thus worse long-term prognosis. The patient may have mild persistent chest pain. Unlike persistent ST elevation after thrombolysis, persistent ST elevation after a successful PCI does not dictate any further procedure, unless the patient has severe recurrence of pain.

Patients with no-reflow are treated with (i) intracoronary vasodilators, (ii) GPI, or (iii) IABP. After treatment of the epicardial stenosis, IABP improves coronary microvascular flow and relieves ongoing ischemia.

When angiography is performed in patients who have been successfully reperfused with fibrinolytics, data from the pharmacoinva- sive trials suggests that ~15–20% of the infarct-related arteries have a residual stenosis <50% that does not require PCI.^30,43,66,67 While most plaques that lead to MI are <50% at baseline, fibrinolytics often partially dissolve the thrombus, not fully, hence the frequent residual obstruction.