No-Reflow During PCI: A Bedside Reference for Operators

The stent is deployed, the angiographic result looks acceptable, and then the contrast column stops moving. The patient becomes bradycardic, complains that the pain is worse than before, and the ST segments that were coming down start to climb again. In a large tertiary centre this is a moment for a second operator and a shelf full of intracoronary agents. In much of international practice it happens with one operator, one scrub nurse, whatever vasodilators the pharmacy stocked last quarter, and no surgical cover. This reference is organised around the choices that have to be made in those next fifteen minutes, in the order they arise.

Naming the problem accurately

Impaired antegrade filling despite a patent, unobstructed epicardial vessel is a microvascular diagnosis made by exclusion at the table. Grade it the same way every time: TIMI flow for the epicardial column, corrected TIMI frame count when the difference between grades 2 and 3 is arguable, and myocardial blush grade for tissue-level perfusion. Blush is the parameter most often omitted and the one that correlates best with infarct size, so make it a habit rather than an afterthought. Where physiology is available, an index of microcirculatory resistance measured after the case gives you a number that predicts subsequent left ventricular remodelling independently of how satisfying the final run looked.

The distinction between transient slow flow and established no-reflow is largely a distinction of duration. Both start with the same four processes: distal embolisation of atherothrombotic debris, microvascular spasm, reperfusion injury with oedema and capillary compression, and a platelet-leukocyte inflammatory response that scaffolds microthrombi. The last of these is what converts a recoverable problem into a fixed one, which is why hesitation is expensive.

The decision points

1. Spend sixty seconds excluding the mimics

Before any drug goes down the guide, rule out the conditions that look identical and need the opposite treatment. Wire position in a false lumen or an unrecognised dissection is the dangerous one: advance a microcatheter and inject selectively, or take an intravascular image. Epicardial spasm responds to intracoronary nitroglycerin and should be tested first. Stent underexpansion and edge dissection are mechanical problems requiring mechanical answers, and imaging settles the question faster than argument. Air embolism is unmistakable once seen and is treated with forceful saline flushing and high-flow oxygen. Residual proximal thrombus and an occluded side branch are excluded with a second projection.

2. Treat perfusion pressure as a drug

Microvascular flow is driven by the gradient between aortic diastolic pressure and left ventricular end-diastolic pressure. Allowing a mean arterial pressure of 55 mmHg to persist while you inject vasodilators is self-defeating. Restore volume, start norepinephrine early rather than late, treat bradycardia and atrioventricular block with atropine and a temporary wire, and load volume with inotropic support in right ventricular infarction. In frank cardiogenic shock, mechanical circulatory support belongs in the conversation before the third dose of anything. Haemodynamic restoration is therapy here, not supportive care.

3. Get the drug to the distal bed, not into the guide catheter

This is the single most consequential technical decision in the whole sequence, and it is the one most often skipped under pressure. Comparative work on delivery route has shown substantially better restoration of epicardial flow and tissue blush when agents are delivered distally through a microcatheter, an over-the-wire balloon or an aspiration catheter, compared with injection into the guide, with the choice of agent mattering considerably less than the route. If you take one habit away from this page, make it the reflex of parking a microcatheter distally before you inject.

4. Climb the pharmacological ladder deliberately

Start with an intracoronary vasodilator delivered distally and repeat it freely. Adenosine is the traditional first agent and has the advantage of a half-life measured in seconds, though the accumulated randomised evidence for it is weaker than its popularity suggests, with calcium channel blockade and diluted epinephrine performing better in pooled analyses of final flow and ST-segment resolution. Where the mechanism is clearly embolic or thrombotic and bleeding risk permits, a glycoprotein IIb/IIIa inhibitor is a reasonable second line. Diluted intracoronary epinephrine is the rational refractory choice in the normotensive or hypotensive patient, where further vasodilatation would be unsafe. Nicorandil, where stocked, and rapid saline boluses through a distally positioned aspiration catheter are useful adjuncts.

5. Reassess with numbers, not impressions

Repeat the frame count and the blush grade after each intervention. Visual estimation drifts towards optimism at exactly the moment optimism is dangerous. Check ST-segment resolution at sixty to ninety minutes; failure to resolve identifies a patient who needs closer surveillance regardless of the final angiographic appearance. The relationship between microvascular integrity and later ventricular function is covered in more depth in our coronary physiology in practice reference.

6. Know when to stop and when not to stent

Deploying a stent into an unperfused bed converts a recoverable problem into a permanent one. If flow remains absent with a heavy thrombus burden after wiring and gentle preparation, deferring stenting for 24 to 48 hours under potent antithrombotic therapy is a legitimate strategy; DEFER-STEMI reduced angiographic no-reflow markedly, although the larger DANAMI-3-DEFER programme did not translate that into a clinical endpoint benefit. Reserve the tactic for the genuinely high thrombus burden case rather than adopting it routinely.

7. Prevent the next one before you start

Anticipation outperforms rescue. Screen every case across patient factors (late presentation, hyperglycaemia on admission, renal impairment, anaemia, shock), lesion factors (large thrombus burden, absent antegrade flow before wiring, long lipid-rich lesions, degenerated vein grafts) and procedural factors (multiple long stents, aggressive high-pressure work, prolonged thrombus manipulation). Grade thrombus burden only after the wire has crossed, since pre-wire grading systematically misleads. High-dose statin loading before intervention, adequate antiplatelet loading, prophylactic distal vasodilatation before stenting, and undersized balloon preparation at a conservative balloon-to-artery ratio all reduce the odds. These pre-case habits are set out procedurally in our primary angioplasty golden hour protocol.

When to escalate, transfer or call for help

• Call the second operator immediately if flow has not recovered after two rounds of distally delivered vasodilator, or if you are considering intravascular imaging while the patient is unstable.
• Escalate to mechanical support when hypotension persists despite vasopressors in a large anterior territory. Support restores the perfusion gradient the microcirculation needs and buys time for the vasodilators to work.
• Place a temporary pacing wire, or at minimum draw up atropine, before giving adenosine or verapamil into a dominant right coronary artery.
• Arrange transfer to a centre with circulatory support and surgical cover if refractory no-reflow coexists with shock, mechanical complication or recurrent ventricular arrhythmia. Reference material for stabilising these patients during transfer is collected in the acute cardiac care worldwide protocols and the interventional and acute care reference hub.

What to document

• TIMI flow before wiring, after wiring, and at the end of the case, with corrected frame counts where the grade is borderline.
• Myocardial blush grade at the end of the case. Its absence from a report is conspicuous.
• Thrombus grade assessed after wire crossing.
• Every agent given, with dose, dilution and the route of delivery stated explicitly as guide or distal.
• Haemodynamic interventions, including pacing, vasopressors and any mechanical support.
• ST-segment resolution at 60 to 90 minutes, and the index of microcirculatory resistance if measured.
• The follow-up imaging plan, since these patients warrant an early assessment of ventricular function.

Bench card

Order of operations to keep taped inside the cupboard door: exclude mimics, fix the pressure, park a microcatheter distally, vasodilate and repeat, escalate to glycoprotein blockade or epinephrine, reassess with frame count and blush, decide about deferring the stent. Wider procedural context sits in the cath lab reference collection and the volume on catheterisation laboratory complications. A more didactic treatment of the same territory is available as this no-reflow and slow flow management guide.

Questions from the floor

Is aspiration thrombectomy justified when flow is lost?

Routine use during primary intervention is not supported, but bailout aspiration for a large residual thrombus remains a defensible operator decision. Its more useful role in this setting is often as a delivery conduit for distal drug administration.

Which agent should a small laboratory stock if it can only stock two?

A calcium channel blocker without strong nodal effect and a preparation of epinephrine suitable for dilution will cover most scenarios, including the hypotensive patient in whom further vasodilatation is unsafe. Adenosine is convenient but should not be the only option available.

Does no-reflow at the table always mean a worse outcome?

It is consistently associated with larger infarcts, more adverse remodelling and higher mortality, but the association is graded. A patient whose flow and blush recover fully during the case sits in a different risk category from one who leaves the laboratory with persistent microvascular obstruction, which is precisely why objective grading before and after matters.

Should these patients have cardiac magnetic resonance imaging?

Where available, it quantifies microvascular obstruction and intramyocardial haemorrhage and refines prognosis, particularly when ventricular function is borderline. In settings without access, an early echocardiogram with strain assessment is a reasonable substitute for follow-up planning.

Reviewed by Dr A M Thirugnanam, MD, MSICP, FSCAI, Ph.D., Senior Interventional Cardiologist — drawn from primary angioplasty practice in laboratories where the operator is also the person who has to stabilise the patient.