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Slow Flow – Case 1

Clinical Presentation

  • 86-year-old male who presented with chest pain (CCS Class III).

Past Medical History

  • HTN, HLD, DM, Former Tobacco Use, CAD s/p 3 vessel CABG (SVG to RCA known to be occluded) followed by multiple PCI’s, Prostate Cancer s/p Brachytherapy (2011), OSA, Aortic Stenosis (AVA 0.8 cm2), ESRD on iHD
  • LVEF 37%

Clinical Variables

  • None


  • Home Medications: Aspirin, Clopidogrel, Atorvasatin, Metoprolol Tartrate, Isosorbide Mononitrate, Gabapentin, Cyclobenzaprine, Allopurinol, Phoslo, Insulin
  • Adjunct Pharmacotherapy: Clopidogrel, Bivalirudin, Heparin IV

Pre-procedure EKG


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Right coronary artery (RCA) angiography
  • 80-90% severely calcified ectatic lesions in the tortuous RCA
  • 90-95% calcified lesion in the right posterior descending artery (RPDA).
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Right coronary artery (RCA) angiography

  • 80-90% severely calcified ectatic lesions in the tortuous RCA
  • 90-95% calcified lesion in the right posterior descending artery (RPDA).
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No significant stenosis in the saphenous vein graft (SVG) to the first obtuse marginal (OM1) branch of the left circumflex (LCx) coronary artery.

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No obstruction in LIMA to LAD bypass graft.

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RPDA wired with use of a Teleport microcatheter.

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Wire exchanged for Rota-Extra Support wire and rotational atherectomy performed using a 1.25mm burr at 150k RPM.

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Angiography after rotational atherectomy.

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Repeat rotational atherectomy using a 1.75mm burr at 150k RPM (polishing run).

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Angiography after rotational atherectomy showing slow flow.

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IC vasodilators administered through the guide catheter with no improvement in flow. This was followed by pre-dilatation of the RPDA with a Trek NC 2.5/20mm balloon.

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Pre-dilatation of the distal RCA with a Trek NC 2.5/20mm balloon.

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Guidezilla extension catheter used to help deliver a NC Emerge 2.75mm/8 mm balloon to the distal RCA followed by lesion pre-dilatation.

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Pre-dilatation of the RPDA with a NC Emerge 2.75/8mm balloon.

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Deployment of a Synergy 2.75/38mm stent in the RPDA.

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Post-dilatation of the stent placed in the RPDA with a Trek NC 3.25/12mm balloon.

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Pre-dilatation of the proximal RCA with a Trek NC 3.25/12mm balloon.

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Pre-dilatation of the proximal RCA with a Trek NC 3.25/12mm balloon.

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Angiography of the RCA after proximal RCA lesion pre-dilatation.

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Pre-dilatation of the RCA (distal to proximal) with a NC Emerge 5.0/8mm balloon.

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Deployment of a Synergy 5.0/28mm stent in the distal RCA, overlapping with the proximal stent edge of the recently placed stent in the RPDA.

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Deployment of a Synergy 5.0/12mm stent in the proximal RCA.

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Angiography of the RCA after placement of two additional stents.

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Positioning of a Synergy 5.0/12mm stent in the mid RCA.

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Post-dilatation of stents placed in the RCA with a NC Emerge 5.5/12mm balloon.

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Angiography after stents post-dilatation showing persistent slow flow.

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Final angiography showing TIMI 2 flow in the RCA. Patient was hemodynamically unstable with persistent chest pain, and an intra-aortic balloon pump (IABP) was placed.

Post-procedure EKG

Case Overview

  • Underwent intervention of the RCA.
  • Rotational atherectomy was performed, and after upsizing to a 1.75mm burr the procedure was complicated by slow flow.
  • IC vasodilators were administered through the guide catheter, without improvement in flow.
  • Serial balloon inflations performed followed by placement of multiple stents in the RCA, without improvement in flow.
  • Patient was hemodynamically unstable with ongoing chest pain, and an IABP was placed.
  • Troponin-I peaked at 32.06 ng/mL and CK-MB peaked at 73.8 ng/mL.
  • Patient was discharged 4 days later without further sequelae.

Learning Objectives

  • What is the likely explanation or reason why the complication occurred?
    • Slow flow following rotational atherectomy – likely due to distal embolization of debris.
  • How could the complication have been prevented?
    • When performing rotational atherectomy consider the following to prevent complications:
      • Keep systolic BP >100mmHg and avoid bradycardia
      • Perform short runs <20 seconds with a gentle pecking motion to advance the rota burr, maintain rotational speed around 150-160k RPM
      • Use Rota-flush and consider use of glycoprotein IIB/IIIA inhibitors
    • Vasodilators should be given prophylactically and for treatment of slow flow/no-reflow.
    • Assure patient is given adequate periprocedural antithrombotic therapy (antiplatelets and anticoagulants).
      • Pay close attention to the ACT during the procedure and dose anticoagulation accordingly to maintain ACT >300 prior to performing an intervention (Hemochron machine).
    • Use a rota-burr which is appropriately sized for the vessel. Ideally the burr should be 0.5-0.6x the distal vessel size when performing a plaque modification strategy, and 0.8-0.85x the distal vessel size when performing a debulking strategy (STRATA trial). With plaque modification strategy the purpose is to disrupt the calcium so it allows for safe passage of devices and easier expansion of device, balloons, and stents. With debulking, the aim is to break the calcium into particles so it can move through the coronary artery and eventually washout of the coronary microcirculation.
    • Lithotripsy device: Currently under investigation in the USA (approved for use in Europe). It is uncertain if this device will result in reduced complications including slow flow.
  • Is there an alternate strategy that could have been used to manage the complication?
    • The initial step in management of slow flow/no-reflow involves administration of intra-coronary vasodilators through the guide catheter. If this fails, recommended using a dual-lumen microcatheter (Twinpass is the only dual lumen microcatheter available in the USA) to deliver intra-coronary medications to the distal vessel and microvasculature. Next, perform angiography with delivery of contrast through the microcatheter to determine if there is distal coronary flow. If distal vessel flow is not preserved the likely etiology of abrupt vessel closure (AVC ) is no-reflow due to distal embolization of debris or thrombus, and IC vasodilators should be administered through the microcatheter targeted to the distal vessel and microvasculature. If flow is preserved, then the likely etiology of AVC is dissection (proximal to the point of microcatheter injection), and treatment involves placement of a stent. It is reasonable to perform aspiration thrombectomy prior to microcatheter based angiography injection (depending on the clinical context/presence of thrombus).
  • What are the important learning points?
    • The best treatment for slow flow/no-reflow is to prevent it from happening.
    • The exact mechanism of the no-reflow phenomenon is unclear, but it is thought to be associated with endothelial swelling, neutrophil infiltration, and platelet aggregation causing obstruction and spasm in the microvasculature.
    • One of the possible complications of PCI especially during rotational or orbital atherectomy is slow flow/no-reflow. The common settings where this complication arises are when performing interventions of long calcified lesions, CTO’s (particularly RCA CTO), thrombotic lesions, and vein grafts. Also, incidence is higher when a patient has poor LV function and hemodynamic instability.
    • Important to have multiple vasodilators readily available during a procedure. We use the following agents and administer them intra-coronary.
      • Nitroprusside 50-200 mcg, Adenosine 30-40 mcg, Verapamil 100-200 mcg, Nicardipine 100-200 mcg
      • Nitroglycerin 100-200 mcg (we use NTG for slow flow/no-reflow when it involved the epicardial vessels and not the coronary microvasculature)
    • If the patient is hypotensive and this impedes the administration of intra-coronary vasodilators to treat slow flow/no-reflow, we recommend administration of IV phenylephrine 100-200 mcg as needed (may result in reflex bradycardia) to increase blood pressure, and then administer intra-coronary vasodilators.
    • If there is refractory slow flow/no reflow then consider placement of an IABP. This helps with reduction in afterload, and improves coronary perfusion pressure by increasing coronary blood flow during diastole, and reduction in LVEDP.
    • Depending on the size and function of the LV (LVEF <30%), consider using upfront LV support as it can help improve coronary perfusion pressure.
Educational Content


  • AVC is the commonest major complication of PCI1
  • Incidence: 0.3% [used to be 3% in pre-stent era]2
  • Risk factors:3
    • Proximal vessel tortuosity
    • Diffuse lesion
    • Pre-existing thrombus
    • Degenerated vein graft
    • Extremely angulated lesion
    • Unstable angina
    • Multivessel disease
    • Female gender
    • Chronic renal failure
  • Common causes:3
    • Coronary dissection
    • Intracoronary thrombus formation
    • Native thrombus (or atheroma) embolization
    • Air injection
    • Coronary no-reflow
    • Coronary vasospasm

In the current DES era, commonest causes of AVC are stent edge dissection and acute stent thrombosis. However, the cause is indeterminate in almost 50% of patients.2

  • Classification of coronary perforation: As per the National Heart, Lung and Blood Institute scheme, types A–F classification remains useful to describe the severity of luminal injury:4
Type AMinor radiolucency within the coronary lumen without dye persistence
Type BParallel tracks or double lumen separated by a radiolucent area during angiography without dye persistence
Type CExtraluminal, persisting extravasation of contrast
Type DSpiral luminal filling defects
Type EPersistent lumen defect with delayed antegrade flow
Type FFilling defect accompanied by total coronary occlusion
  • Prevention:
    • Maintain ACT > 300 throughout procedure
    • Make sure interface is free of air
    • Avoid high-pressure balloon dilatation or stenting
    • Avoid unnecessary post-dilatation and very long stents
    • Use distal protection devices in vein graft PCI
    • Be careful when retrieving delivery after stent implantation
    • Avoid geographical miss during stenting
    • Avoid aggressive post-dilatation at the stent edges
    • Be careful while positioning wire distal tip in tortuous vessel
  • Management: Abrupt closure results in acute ischemia manifesting as ECG changes, hypotension, bradycardia, chest pain and ventricular arrhythmias. The first step is to identify the underlying cause of AVC and then treat it accordingly.
    • Immediate priority should be to ensure intraluminal position of coronary guidewire and, if in doubt, an over-the-wire balloon catheter or Twin-Pass or other microcatheter should be advanced distal into the target vessel to allow minimal contrast media injection and confirm wire position.
    • If intraluminal guidewire position is confirmed, the most likely mechanism underlying AVC is dissection or intraluminal thrombus. Prompt balloon

inflation should be attempted to establish antegrade flow. If flow returns immediately after balloon inflation the likely cause of AVC is dissection and urgent stenting is useful for stabilizing.

    • If the distal flow after balloon inflation is sluggish (TIMI 0 or 1), the likely cause of AVC is distal thromboembolism. Using a Twin-Pass or microcatheter to administer distal vasodilators can help reestablish flow.
    • If initial contrast agent injection reveals guidewire position within a false lumen, careful exploration of the occluded segment using a second guidewire must be performed.
    • Aspiration thrombectomy and Glycoprotein IIb/IIIa antagonists may be helpful if acute closure is due to

thrombus. Control of anticoagulation is of paramount importance to avoid thrombotic occlusion of stented artery. ACT should be measured every ~30 minutes to keep ACT > 300 throughout the procedure and dose of anticoagulation is adjusted accordingly. If ACT is not reaching therapeutic levels consider resistance to anticoagulant and a possible reason for suspected thrombus formation causing AVC.

    • Intravenous fluids, vasopressors, inotropes and intra-aortic balloon pump (IABP) should be considered for unstable hemodynamics.
    • Emergency CABG should be considered if patient have persistent AVC depending on the location of the occlusion, patient’s clinical condition and assessment of risks and benefits.

Coronary slow flow/no-reflow phenomenon

Slow flow/No-reflow is an acute reduction in coronary flow (TIMI grade 0–1) in a patent vessel with absence of dissection, thrombus, spasm, or high-grade residual stenosis at the original target lesion.5 The underlying mechanism is complex and not completely understood, but some proposed mechanisms include distal embolization of calcium, plaque or thrombus and microvascular spasm caused by release of vasoconstrictor substances like serotonin and thromboxane, oxidative stress, and reperfusion injury.6 Clinical and lesion characteristics associated with higher incidence of no-reflow include left ventricular systolic serotonin and thromboxane, oxidative stress,and reperfusion injury.6 Clinical and lesion characteristics associated with higher incidence of no-reflow include left ventricular systolic dysfunction or hemodynamic instability, long calcified lesions, ostial lesions, chronic total occlusion of right coronary artery, thrombotic lesions, and vein graft lesions. Use of rotational atherectomy is also associated with a higher incidence of no-reflow.
    • Direct stenting whenever feasible
    • Use of distal embolic protection devices for vein graft interventions.
    • Aspiration thrombectomy in STEMI cases if there is large thrombus burden
    • For cases involving rotational atherectomy, the use of rota flush, small

initial burr sizes, shorter rotablation runs, avoiding drops in rotations per minute (RPMs), and prevention of hypotension/bradycardia

Management: Coronary no re-flow must be immediately differentiated from AVC due to dissection as placement of stent in a vessel with no reflow may worsen the situation. Exclusion of dissection, thrombus, spasm, or high-grade residual stenosis at the original target lesion suggests no-reflow.
    • Stabilize hemodynamics with medications/intra-aortic balloon pump (IABP)
    • IC verapamil (100–200 μg)
    • IV adenosine (10–20 μg)
    • IC nitroprusside (50–200 μg)
    • Moderately forceful injection of blood or saline through the manifold
    • GPIIb/IIIa agents, IV cangrelor may also be helpful

Air Embolism

Intracoronary air embolism is a potentially lethal but rare complication. It could result in hypotension, hemodynamic collapse, cardiac arrest, and in rare cases death. Coronary air embolism is almost always iatrogenic. It occurs mostly when
    • Catheters are not adequately aspirated and flushed
    • During introduction or withdrawal of a guidewire, balloon catheter or other interventional devices
    • Rupture of a balloon during high inflation
    • During intracoronary medication injection

Diagnosis: Coronary air embolism is detected fluoroscopically as intracoronary filling defects during dye injection. It could also be seen as abrupt cutoff of a vessel secondary to occlusion of distal circulation with air column. Clinically small air embolism may be asymptomatic. Larger air embolism may present as chest pain, hypotension, ischemic EKG changes, or cardiac arrest.
    • Do not engage the left main coronary when pulling out the guiding wire unless the patient has excessive aortic tortuosity or an enlarged aortic root.
      • Do not connect the manifold to the catheter with the flush running. This may lead to an air embolism if the catheter already has a column of air inside it.
      • Draw back at least 2 cc of blood into the injection syringe and make sure that the interface is free of air prior to injection.
      • Inject some dye into the ascending aorta prior to engaging left main.
      • Always ensure that all the catheters and tubings are aspirated, flushed and free of air.
      • Take adequate care when prepping stents or balloons and ensure that the syringe tip is facing downwards.
      • Always inject with the syringe tip facing downwards


        • Put patient on 100% oxygen.
        • Flush air free saline vigorously into the coronary arteries. Aspirate blood and air column via guide catheter and reinject saline forcefully back into coronary arteries.
        • Administer IV phenylephrine 200 μg for hypotension. Repeat, as needed every minute. If significant hypotension or hemodynamic collapse is present, push IV 1 cc epinephrine (1:10,000 dilution).
        • Intracoronary injection of vasodilators (adenosine, nitroprusside, verapamil) may be attempted.
        • Supportive measures should be instituted (IABP for persistent hypotention) and patient admitted to intensive coronary care unit for further monitoring

      Coronary Vasospasm

      Coronary vasospasm can be induced by PCI secondary to endothelial denudation and nitric oxide loss.
        • Some cases are catheter-induced which is caused by a contact of a catheter without balloon deployment. It is usually short-lived and is most prone to occur at the ostium of the right coronary artery (RCA). The left main is less susceptible to ostial spasm
        • Rotablator cases are more prone to vasospasm
        • Coronary vasospasm is detected by presence of EKG changes of ST segment elevation in association with angina, and then EKG completely returns to baseline upon resolution of symptoms.
        • The definitive diagnosis of coronary vasospasm is made angiographically by demonstration of reduction of luminal diameter in a discrete segment of the vessel, which is proven reversible by the administration of intracoronary vasodilators.
        • Initial step is intracoronary vasodilatation with IC calcium channel blockers and/or nitrates [nitroglycerin 100-300 mcg, verapamil 100 mcg/min, up to 1.0-1.5 mg, nicardipine 100-300 mcg, nitroprusside 100-300 mcg]
        • IV atropine can be useful if there is associated hypotension of bradycardia
        • If vasospasm persists, remove all hardware and leave the guide wire in place to maintain position. This may

      If vasospasm persists, remove all hardware and leave the guide wire in place to maintain position. This may minimize distal vessel spasm

        • Repeat prolonged PTCA for 2-5 minutes at low pressures (1-4 atmospheres)
        • Stenting should be reserved in cases if all the above measures have failed, as it may lead to propagation of spasm to a new location
        • Refractory vasospasm may be indicative of dissection, which is also an indication for stenting

      Abrupt Vessel Closure Summary

      • Dissection
        • Minor dissections - usually heal without clinical sequelae, no treatment required
        • Major dissections - repeated prolonged low-pressure balloon [distal vessel], stenting [Proximal/mid vessel segment or impaired flow due to dissection]
      • Thromboembolism
        • Twin-Pass or microcatheter to administer vasodilators distally
        • Check ACT to keep > 300. Consider starting IV Cangrelor or bailout GPIs
        • Balloon dilatation and/or thrombus aspiration in case of stent thrombosis
        • Stenting on case of thrombosis in in unstented vessel segment
      • No-reflow
        • Intracoronary Adenosine, Nitroprusside, Nicardipine, Verapamil, or GPI’s
        • A transit catheter or over-the-wire balloon should be used to deliver the vasodilators to the distal microvasculature
        • Insertion of IABP to improve flow
      • Air embolism
        • Start 100% oxygen
        • Flush air free saline vigorously into the coronary arteries. Aspirate blood via guide catheter and reinject forcefully back into coronaries
        • IV phenyl epinephrine or epinephrine as needed
        • Intracoronary injection of vasodilators
      • Vasospasm
        • Intracoronary Nitroglycerin, Adenosine, Nitroprusside, Nicardipine, or Verapamil
        • IV fluid bolus and/or atropine as needed
        • Remove all hardware and leave the guide wire in place to maintain position
        • Repeat prolonged PTCA for 2-5 minutes at low pressures (1-4 atmospheres)
      • Unknown etiology
        • Maintain wire position distally and pass a microcatheter distally to inject contrast
        • If flow distally, problem at site of vessel closure and needs to be investigated
        • If no flow distally, consider no reflow and give IC vasodilators


      1. de Feyter P.J., de Jaegere P.P.T., Murphy E.S., Serruys P.W. (1992) Abrupt coronary artery occlusion during percutaneous transluminal coronary angioplasty. Am Heart J 123:1633–1642.
      2. Francesco Giannini, Luciano Candilio, Satoru Mitomo, Neil Ruparelia, Alaide Chieffo, Luca Baldetti, Francesco Ponticelli, Azeem Latib, Antonio Colombo. Practical Approach to the Management of Complications During Percutaneous Coronary Intervention. J Am Coll Cardiol Intv. 2018 Sep, 11 (18) 1797-1810.
      3. Klein L. (2005) Coronary complications of percutaneous coronary interventions: a practical approach to the management of abrupt closure. Catheter Cardiovasc Interv 64:395–401.
      1. Huber MS, Mooney LF, Madison J, et al. Use of a morphologic classification to predict clinical outcome after dissection from coronary angioplasty. Am J Cardiol 1991;68:467–71.
      2. Rezkalla S.H., Kloner R.A. (2002) No-reflow phenomenon. Circulation 105:656–662.
      3. Piana R., Paik G., Moscucci M., et al. (1994) Incidence and treatment of “no-reflow” after percutaneous coronary intervention. Circulation 89:2514–8.

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