The Article, “Can No-Reflow Be Silent” explains whatno-reflow phenomenon is and how it is important in my field of being acardiovascular technologist. Explanation of no-reflow will be further discussedalong with the signs and symptoms and treatment in the cardiovascular field. No-flow phenomenon, also called “slow-flow” is when there isno blood flow down a vessel that has been treated by stenting, angioplasty, orother intervention such as Rotablator atherectomy.
No-reflow usually occurs whenrestoring blood flow in patients with a ST elevation myocardial infarction(STEMI), stenting degenerated saphenous vein grafts or percutaneous coronaryintervention with thrombus that is distal in the vessel. No-reflow is definedas a TIMI (thrombolysis in myocardial infarction) grade less than or equal to2. According to the Article “Can No-Reflow Be Silent”, the frequency ofno-reflow ranges from 12-25%, and studies have showed that 4-7% of the treatedlesions has a TIMI flow less than or equal to 2. Studies have also showed thathigher rates have been noted when using other flow measurements such asmyocardial contrast echocardiography. The TIMI grade scale is used to accesscoronary artery perfusion beyond the point of occlusion in the vessel. TIMIgrade 2 stands for partial perfusion in which there is delayed antegrade flowwith complete filling distally.
TIMI grade 1 is penetration without perfusionwhere there is faint antegrade flow beyond the occlusion with incompletefilling distally. The last or lowest TIMI grade of 0 refers to no perfusionbeyond the occlusion. With no-reflow having a TIMI grade less than 2, we knowthat there is little to no flow distally in the vessel, even after intervening.With that being said, complications can arise when this happens, like treatinga STEMI patient or working with saphenous vein graft (SVG) interventions. No-reflow is considered adevastating complication with treating ST-elevation myocardial infarction(STEMI) patient or working with saphenous vein graft interventions. Patients canpresent with one of the two types of no-reflow. Reperfusion-related no-reflow(RNR) and primary no-reflow (PNR).
In RNR there is impaired myocardialperfusion due to epicardial coronary obstruction like there is when a patientis having a STEMI. If the obstruction is opened after an intervention, distalmyocardial tissue remains compromised. The left ventricular systolicdysfunction and the size of the infarct is significantly increased with RNR. InPNR, the normal perfused vessel unexpectedly undergoes no-reflow afterintervention. In PNR, PCI relatedbarotrauma is suspected of precipitating distal embolization of atheroma andthrombus. Obstruction more than 50% of the microvasculature is required todecrease myocardial blood flow.
The rate of no-reflow ranges 0.6% to 2% and ismore commonly observes with the use of stents, atherectomy and PCI in saphenousvein grafts (SVG). Patients canpresent with signs and symptoms of no-reflow in multiple ways. In thecatheterization lab, the clinical presentation of no reflow in STEMI patientsis sudden and dramatic. You will be able to see the contrast stop in thecoronary artery, then the patient will feel chest pain, and hemodynamiccompromise will follow. The sudden hemodynamic deterioration may be related to atheroembolismand slowing of blood flow in the healthy arteries. It is often associated with new or persistentST elevation, chest pain, and decreased left ventricular function with lowblood pressure.
It is rare for a patient to have no-reflow, and not presentwith symptoms such as the ones listed above. These signs and symptoms ofno-reflow doesn’t always present while in the catheterization lab. Somepatients do not have any signs of no-reflow until they are in the holding roomafter their intervention has been done, and these are normally lessdramatic. After thrombolytics are given,the patient will have ST-segment elevation and may have hemodynamicdeterioration that will lead to new Q waves. No-reflow phenomenon is alsolinked to ventricular arrhythmias, early congestive heart failure, and evencardiac rupture.
I have not personally been involved with a case whereno-reflow was present after intervention. The best approach in treatingno-reflow is to prevent its occurrence in the first place. It can be preventedor minimized with pharmacological and mechanical pre/post treatment. Whenpossible, a native vessel PCI should be attempted rather than going after aseverely declining saphenous vein graft with a large thrombus. Minimizing thedoor-to-balloon time in an acute MI reduces the chances of RNR. During stentingof high risk lesions, inflations should be of low diameter and pressure whichwould minimize distal embolization. Patients can be pretreated withintracoronary calcium channel blockers for the treatment of saphenous veingrafts.
During rotational atherectomy, no-reflow can be prevented by loweringrotational speed to around 140,000 rpm. Pharmacological preventive measuresduring rotational atherectomy include abciximab, intra-coronary adenosine, anda cocktail including nitrate, verapamil, and heparin. The treatment for noreflow depends on what is causing the no reflow, so it can be treated in a fewdifferent ways. If no reflow is due because of plaque rupture causing thrombusdistally in the vessel, catheter aspiration is done to vacuum the clot out.
Additional anticoagulants such as heparin, ReoPro, or Aggrastat should be givenand rechecking activating clotting time levels is necessary. If no reflow isdue to a dissection, then additional stenting down the vessel is required. Ifno reflow is due to severe spasm, nitroglycerin (100mcg/cc) is recommended torelieve the spasm but it has not been shown to help no-reflow phenomenon unlessgiven in 100 microgram boluses multiple times. Inserting distal protectiondevices or proximal protection is the most common mechanism when performinginterventions on saphenous vein grafts or acute STEMIs. This can help reduceclots and prevent no reflow from happening. No reflow phenomenon, as well as most other cardiovascularcomplications are still being studied for the best treatment. Every patient isdifferent when treating these issues but the treatments listed in the aboveparagraph are the cardiovascular teams “go-to” when treating no-reflowphenomenon.
Filters are still being tested in STEMI but are not standard,however it is always better to be prepared for the worst.