Coronary artery calcification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sudarshan Srivats, M.D., M.P.H.[2], Anahita Deylamsalehi, M.D.[3], Parth Vikram Singh, MBBS[4]

Overview

Moderate-to-severe coronary artery calcification is present in roughly one in five patients undergoing PCI by angiographic assessment (with substantially higher detection by intravascular imaging) and is an independent predictor of stent underexpansion, procedural complications (dissection, perforation, slow/no-reflow, device entrapment), stent thrombosis, restenosis, incomplete revascularization, and higher all-cause mortality. The core problem is mechanical: calcified plaque resists balloon dilation and stent expansion, and the strongest modifiable determinant of long-term outcome is achieving an adequate minimal stent area (MSA) through effective lesion preparation.

The coronary angiogram is specific but insensitive for calcium—it detects only large, thick deposits and cannot report calcium arc, thickness, or depth. Contemporary practice therefore centers on intravascular imaging (IVUS or OCT) to quantify calcium burden, select the appropriate modification tool (non-compliant/specialty balloons, rotational atherectomy, orbital atherectomy, excimer laser, or intravascular lithotripsy), confirm calcium fracture, and verify final stent expansion. A key evolution in recent teaching is that "angiographically severe" calcification does not automatically mandate atherectomy: with meticulous imaging-guided balloon-based preparation, many severely calcified lesions can be treated successfully without an atheroablative device. Devices are best reserved for lesions that are uncrossable, undilatable, or predicted to underexpand by imaging.

Assessment and Grading of Calcification

Angiographic Grading

Angiographic grading is a useful bedside first pass but is limited by low sensitivity (~50%) and high specificity (~95%); it systematically underestimates calcium and cannot reliably detect calcified nodules.[1]

  • None — no radiopacity.
  • Mild — faint radiopacities seen only during the cardiac cycle.
  • Moderate — dense radiopacities seen only during the cardiac cycle.
  • Severe — dense radiopacities seen without cardiac motion before contrast injection, typically involving both luminal borders.

The angiographic threshold for "visible" calcium corresponds to an IVUS arc of ~110° or OCT arc ~101°, thickness ~0.57 mm, length ~4 mm.[1]

Intravascular Imaging

Intravascular imaging is the reference standard for procedural planning. IVUS resolves calcium arc and length but cannot measure thickness (acoustic shadowing from complete reflection at the calcified interface). OCT additionally measures calcium thickness and better characterizes calcified nodules and post-modification fracture, at the cost of shallower penetration and the need for contrast clearance (limiting ostial left main use).[1] Emerging OCT data suggest calcium length may correlate with stent expansion even more strongly than arc or thickness.

The 2021 ACC/AHA/SCAI guideline synopsis states that calcium thicker than 500 µm or involving an arc >270° on intravascular imaging predicts the need for modification to facilitate stent delivery.[2] Calcium thickness is a key determinant of fracture: OCT calcium <0.5 mm thick tends to fracture with balloon predilation irrespective of arc, and fracture is associated with greater stent expansion.

IVUS-Based Calcium Score (Zhang et al.)

One point is assigned for each feature; a score ≥2 predicts underexpansion and favors pre-stent calcium modification.[3]

IVUS-Based Calcium Scoring System (Zhang et al.)
Parameter Threshold Points
Maximum calcium arc and length >270° over ≥5 mm 1
Calcium arc 360° 1
Calcified nodule Present 1
Vessel diameter <3.5 mm 1
Interpretation Score ≥2 → high risk of stent underexpansion

OCT-Based Calcium Score (Fujino et al. — "Rule of 5's")

A score of 4 (or ≥3 by some analyses) predicts underexpansion.[4]

OCT-Based Calcium Scoring System (Fujino et al.)
Parameter Threshold Points
Maximum calcium arc >180° 2
Maximum calcium thickness >0.5 mm 1
Calcium length >5 mm 1
Interpretation Score ≥3 → high risk of stent underexpansion

Revised OCT Score for Severe Calcium (Sato et al. — "Rule of 3's")

For severely calcified lesions (arc >270°), a revised score—minimum thickness >0.3 mm, 360° arc, and length >3 mm within the >270° segment—substantially outperformed the original score in severe calcium (AUC ~0.88–0.90 vs 0.54), correcting the original score's low specificity in this subset.[5]

Detection Points

  • The coronary angiogram is insensitive to lesion calcification, particularly deep vessel-wall calcium.[6]
  • Saphenous vein graft calcification is typically within the reference wall rather than the lesion and is associated with older graft age, insulin-dependent diabetes, and smoking; notably, atherectomy is contraindicated in saphenous vein grafts.[7]
  • Calcified nodules (CN) are found in roughly one-quarter to one-half of severely calcified lesions and are frequently missed by angiography; OCT distinguishes eruptive from non-eruptive CN, which have distinct deformability and prognosis.[1][8]

Treatment

Guideline Recommendations

Class 2a, LOE B-R[2]
In fibrotic or heavily calcified lesions, plaque modification with rotational atherectomy can be useful to improve procedural success.
Class 2b, LOE B-NR[2]
In fibrotic or heavily calcified lesions, plaque modification with orbital atherectomy, balloon atherotomy (cutting/scoring), laser angioplasty, or intracoronary lithotripsy may be considered to improve procedural success.
Intravascular imaging — Class 2a, LOE B-R (2021 ACC/AHA/SCAI); upgraded to Class 1, LOE A in 2024–2025 guidelines[2][9][10]
The 2021 ACC/AHA/SCAI guideline states IVUS can be useful for procedural guidance of complex/left main PCI to reduce ischemic events, with OCT a reasonable alternative except in ostial left main disease (both 2a, B-R). The 2024 ESC chronic coronary syndromes guideline and the 2025 ACC/AHA/SCAI acute coronary syndromes guideline upgraded intravascular imaging (IVUS or OCT) to a Class 1 (LOE A) recommendation for complex or left main PCI.

The 2021 guideline notes that large randomized trials show routine use of atheroablative devices does not improve clinical or angiographic outcomes; their value lies in enabling procedural success in specific circumstances (uncrossable/undilatable lesions).[2] SCAI (2024) and EAPCI/EURO4C-PCR (2023) consensus statements provide imaging-driven algorithms, recommending modification prior to stenting for arc 360°, or arc 270° with length ≥5 mm, and also considering modification for calcified nodules, small/negatively remodeled vessels, and OCT minimum thickness ≥0.5 mm.[11][12]

Treatment Workflow (Imaging-Guided)

Imaging-guided management algorithm for the calcified coronary lesion. After angiographic detection of moderate-to-severe calcification, intravascular imaging (OCT/IVUS) directs lesion classification (deep, superficial, calcified nodule, or uncrossable) and calcium scoring, which determines lesion preparation—non-compliant/cutting/scoring balloons (preferred over IVL for deep calcium), IVL, orbital/rotational/laser atherectomy, or combination. Adequate plaque modification (1:1 NC expansion, calcium fracture, debulking) is confirmed by repeat imaging before DES implantation, followed by post-PCI optimization of underexpansion (IVL, super-high-pressure balloon) and follow-up imaging. Note: the figure's OCT cutoff of "= 3" corresponds to the body text's OCT score ≥3 threshold. DES: drug-eluting stent; IVL: intravascular lithotripsy; IVUS: intravascular ultrasound; LA: laser atherectomy; NC: non-compliant; OA: orbital atherectomy; OCT: optical coherence tomography; RA: rotational atherectomy.
  1. Image first. Interrogate calcified lesions with IVUS or OCT (low-profile balloon predilation may be needed to deliver the imaging catheter). OCT-guided PCI produced larger MSA than angiography guidance in the randomized CALIPSO trial.[13]
  2. Uncrossable lesion → primary atheroablation (rotational or orbital atherectomy), then re-image.
  3. Crossable, superficial/deep calcium → select modification by imaging: NC or specialty (cutting/scoring) balloons for lesser burden or deep calcium beneath fibrosis; atherectomy for long/diffuse superficial calcium; IVL for concentric/eccentric calcium and calcified nodules.
  4. Confirm modification. Re-image for calcium fractures and/or perform 1:1 balloon angioplasty to confirm full expansion in ≥2 views before stenting. If suboptimal, escalate (including combination therapy) before deploying the stent.
  5. Deploy DES, then image again for edge dissection, malapposition, tissue protrusion, geographic miss, and underexpansion.
  6. Underexpansion unresponsive to high-pressure NC balloons → super-high-pressure NC balloons, IVL ("stent-through" IVL), or excimer laser.

Combination and Bail-out Strategies

Highly resistant calcium (especially non-deformable calcified nodules) may require combination therapy: RA or OA to debulk followed by IVL to fracture ("RotaTripsy"), or RA with cutting/scoring balloons (PREPARE-CALC-COMBO).[14] For established stent underexpansion, "stent-through" IVL is a recognized bail-out strategy, with efficacy and safety data from the international CRUNCH registry.[15] High-energy excimer laser can disrupt calcium beneath stent struts to facilitate expansion when balloons fail.

Device-Specific Technique and Evidence

Guidewire and Access Technique

Heavily calcified lesions often require a hydrophilic or extra-support guidewire with a core extending to the tip to cross. Once across, exchange for a softer, atraumatic workhorse wire distally to minimize vessel perforation risk. When device delivery is difficult, a microcatheter, a more supportive wire, or a guide extension catheter facilitates equipment passage; a second "buddy" wire can straighten tortuosity and improve deliverability of balloons and stents. Adequate guide-catheter support and coaxial alignment are prerequisites before attempting atherectomy or specialty-balloon delivery.

Balloon-Based Preparation

Calcified plaques require higher pressures to expand. Non-compliant balloons provide more uniform high-pressure expansion and focused force at the calcified plaque, whereas differential expansion of semi-compliant balloons may injure less-diseased adjacent segments. Cutting/scoring balloons score and modify focal calcium and reduce slippage, and are particularly valuable for focal lesions, ostial lesions, and in-stent restenosis; they are not primarily restenosis-reduction tools. Never deploy a stent into a lesion that will not fully expand on 1:1 balloon angioplasty—underexpansion drives restenosis and stent thrombosis.

Rotational and Orbital Atherectomy

Rotational atherectomy ablates rigid fibrocalcific plaque and is favored for uncrossable and long, diffuse superficial calcium. Orbital atherectomy uses an eccentric diamond-coated crown that ablates during forward and backward passes, producing smaller microparticulate debris. Both work by enabling calcium fracture rather than by bulk debulking. Contemporary randomized data (ECLIPSE, ICARE, ROTA.shock) show no clinical superiority of routine atherectomy over balloon-based or IVL strategies; atherectomy is one tool among several. In ECLIPSE, routine orbital atherectomy did not improve MSA or 1-year target-vessel failure versus balloon angioplasty before DES in severely calcified lesions eligible for both strategies (TVF 11.5% vs 10.0%), and only ~5% of balloon-arm lesions crossed over to atheroablation.[16]

Technical safety: Use a burr-to-artery ratio of ~0.5–0.6, short ablation runs (≤15–20 s) with adequate reperfusion between runs, avoid abrupt decelerations, and confirm the dedicated wire is in the distal true lumen before activation. Atherectomy is contraindicated in the presence of dissection or angiographic thrombus, in saphenous vein grafts, and when true-lumen wire position cannot be confirmed.[11][12] Anticipate bradycardia during RCA or dominant LCx atherectomy; have temporary pacing available. Avoid atherectomy once a dissection is present or through acute bends (wire bias raises perforation risk).

Intravascular Lithotripsy (IVL)

IVL delivers sonic pressure waves (~50 atm) from a semi-compliant balloon, fracturing intimal and medial calcium by a fatigue mechanism while minimizing soft-tissue trauma and atheroembolic debris. Across the DISRUPT CAD I–IV program, procedural success was high (~92%) with a favorable safety profile, including very low rates of perforation, slow flow, and no-reflow.[17][18] The Shockwave system is FDA-approved for de novo, severely calcified lesions prior to stent implantation. Head-to-head trials (ROTA.shock; ICARE OFDI) show IVL is non-inferior to RA for MSA with comparable safety and equivalent 12-month target-lesion failure; meta-analyses favor IVL for higher procedural success and fewer perforation/slow-flow events, though RA yields greater acute lumen gain and IVL is costlier.[19][20] IVL can cause transient asynchronous ventricular capture ("shocktopics"), benign but potentially provoking hypotension in bradycardic patients. IVL is delivered on a balloon platform and cannot cross a truly uncrossable lesion without prior modification.

Calcified Nodule Management

Calcified nodule subclassification now guides therapy: eruptive nodules are deformable and respond to balloon/IVL, while non-eruptive nodules are stiff and may need atherectomy ± IVL, with high reprotrusion/TLR risk regardless of strategy. Treating a non-eruptive/stiff nodule as ordinary calcium leads to malapposition, underexpansion, and reprotrusion through struts.[8] Randomized evidence is lacking; OCT-based comparisons of RA/OA/IVL show similar MSA and 1-year outcomes, and drug-coated balloon strategies to avoid stenting remain investigational.

Clinically Actionable Recommendations

  • Use intravascular imaging for any moderately-to-severely calcified lesion to quantify calcium and plan strategy; OCT preferred when thickness/nodule characterization is needed and the lesion is crossable and not ostial left main.
  • Apply a calcium score (IVUS Zhang ≥2; OCT Fujino ≥3–4, or Sato "Rule of 3's" in severe calcium) to decide on upfront modification.
  • Match tool to morphology and length: balloon-based prep for focal/deeper calcium; atherectomy for uncrossable or long diffuse superficial calcium; IVL for concentric/eccentric calcium and eruptive nodules.
  • Confirm calcium fracture / full balloon expansion before stenting.
  • Post-stent imaging is mandatory to detect and correct underexpansion, malapposition, and edge dissection.
  • Do not use atheroablation routinely in lesions that cross and dilate with balloons; reserve devices for uncrossable/undilatable/predicted-underexpansion lesions.
  • Escalate to combination therapy (RA/OA + IVL) for non-deformable, resistant calcium.

Areas of Uncertainty

  • Guidelines still list RA as Class 2a and OA/IVL/laser/atherotomy as Class 2b, but the newest RCTs (ECLIPSE, ROTA.shock, ICARE) show no clinical advantage of routine atheroablation over balloon-based or IVL strategies; the 2b/2a distinction predates several of these trials.
  • IVL vs RA/OA selection remains individualized; no trial shows one device improves hard clinical outcomes over another.
  • OCT vs IVUS for calcified-lesion guidance: OCT better characterizes thickness/nodules/fracture, but definitive superiority is unproven (randomized subgroups show no significant difference).
  • The ideal MSA target in calcified vessels is extrapolated rather than trial-defined, and calcium-score thresholds are not standardized.
  • Drug-coated balloon and "stentless" strategies for prepared calcified lesions remain experimental.

Common Pitfalls

  • Deploying a stent into an unprepared or undilatable lesion—the leading avoidable cause of underexpansion, restenosis, and stent thrombosis.
  • Relying on angiography, which underestimates arc/length and misses nodules.
  • Reflexive atherectomy for any "severe" angiographic calcium—most such lesions can be balloon-prepared successfully.
  • Rotational atherectomy through tortuosity/acute bends or into a dissection—perforation risk from wire bias.
  • Aggressive high-pressure ballooning after medial dissection from atherectomy.
  • Not repeating imaging after modification—failing to verify calcium fracture yields inadequate stent expansion.
  • Ignoring calcified nodule subtype.
  • Undersizing/oversizing the stent by using lumen rather than external elastic lamina–based sizing on imaging.

2011 ACCF/AHA/SCAI Guidelines for Percutaneous Coronary Intervention (DO NOT EDIT)[21]

Calcified Lesions (DO NOT EDIT)[21]

Class IIa
"1. Rotational atherectomy is reasonable for fibrotic or heavily calcified lesions that might not be crossed by a balloon catheter or adequately dilated before stent implantation.[22][23][24] (Level of Evidence: C)"

2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization (DO NOT EDIT)[2]

Calcified Lesions (DO NOT EDIT)[2]

Class 2a, Level of Evidence: B-R
"In patients with fibrotic or heavily calcified lesions, plaque modification with rotational atherectomy can be useful to improve procedural success."
Class 2b, Level of Evidence: B-NR
"In patients with fibrotic or heavily calcified lesions, plaque modification with orbital atherectomy, balloon atherotomy, laser angioplasty, or intracoronary lithotripsy may be considered to improve procedural success."

References

  1. ↑ 1.0 1.1 1.2 1.3 Mintz GS, Matsumura M, Ali Z, Maehara A (2022). "Clinical Utility of Intravascular Imaging: Past, Present, and Future". JACC Cardiovasc Imaging. 15 (10): 1799–1820. doi:10.1016/j.jcmg.2022.04.026.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Writing Committee Members. Lawton JS, Tamis-Holland JE, Bangalore S, Bates ER, Beckie TM; et al. (2022). "2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines". J Am Coll Cardiol. 79 (2): e21–e129. doi:10.1016/j.jacc.2021.09.006. PMID 34895950 Check |pmid= value (help).
  3. ↑ Zhang M, Matsumura M, Usui E, et al. (2021). "Intravascular Ultrasound-Derived Calcium Score to Predict Stent Expansion in Severely Calcified Lesions". Circ Cardiovasc Interv. 14 (10): e010296. doi:10.1161/CIRCINTERVENTIONS.120.010296. PMID 34665658 Check |pmid= value (help).
  4. ↑ Fujino A, Mintz GS, Matsumura M, et al. (2018). "A new optical coherence tomography-based calcium scoring system to predict stent underexpansion". EuroIntervention. 13 (18): e2182–e2189. doi:10.4244/EIJ-D-17-00962. PMID 29400655.
  5. ↑ Sato T, Matsumura M, Yamamoto K, et al. (2025). "A Revised Optical Coherence Tomography-Derived Calcium Score to Predict Stent Underexpansion in Severely Calcified Lesions". JACC Cardiovasc Interv. 18 (5): 622–633. doi:10.1016/j.jcin.2024.12.001.
  6. ↑ Mintz GS, Popma JJ, Pichard AD; et al. (1995). "Patterns of calcification in coronary artery disease. A statistical analysis of intravascular ultrasound and coronary angiography in 1155 lesions". Circulation. 91 (7): 1959–65. PMID 7895353.
  7. ↑ Castagna MT, Mintz GS, Ohlmann P; et al. (2005). "Incidence, location, magnitude, and clinical correlates of saphenous vein graft calcification: an intravascular ultrasound and angiographic study". Circulation. 111 (9): 1148–52. doi:10.1161/01.CIR.0000157160.69812.55. PMID 15723972.
  8. ↑ 8.0 8.1 Shin D, Karimi Galougahi K, Spratt JC, et al. (2024). "Calcified Nodule in Percutaneous Coronary Intervention: Therapeutic Challenges". JACC Cardiovasc Interv. 17 (10): 1187–1199. doi:10.1016/j.jcin.2024.03.032.
  9. ↑ Rao SV, O'Donoghue ML, Ruel M, et al. (2025). "2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the Management of Patients With Acute Coronary Syndromes". J Am Coll Cardiol. doi:10.1016/j.jacc.2024.11.009.
  10. ↑ Vrints C, Andreotti F, Koskinas KC, et al. (2024). "2024 ESC Guidelines for the management of chronic coronary syndromes". Eur Heart J. 45 (36): 3415–3537. doi:10.1093/eurheartj/ehae177.
  11. ↑ 11.0 11.1 Riley RF, Patel MP, Abbott JD, et al. (2024). "SCAI Expert Consensus Statement on the Management of Calcified Coronary Lesions". J Soc Cardiovasc Angiogr Interv. 3 (2): 101259. doi:10.1016/j.jscai.2023.101259.
  12. ↑ 12.0 12.1 Barbato E, Gallinoro E, Abdel-Wahab M, et al. (2023). "Management strategies for heavily calcified coronary stenoses: an EAPCI clinical consensus statement in collaboration with the EURO4C-PCR group". Eur Heart J. 44 (41): 4340–4356. doi:10.1093/eurheartj/ehad342.
  13. ↑ Amabile N, Rangé G, Landolff Q, et al. (2025). "OCT vs Angiography for Guidance of Percutaneous Coronary Intervention of Calcified Lesions: The CALIPSO Randomized Clinical Trial". JAMA Cardiol. 10 (7): 666–675. doi:10.1001/jamacardio.2025.0741.
  14. ↑ Allali A, Toelg R, Abdel-Wahab M, et al. (2022). "Combined rotational atherectomy and cutting balloon angioplasty prior to drug-eluting stent implantation in severely calcified coronary lesions: The PREPARE-CALC-COMBO study". Catheter Cardiovasc Interv. 100 (6): 979–989. doi:10.1002/ccd.30423. PMID 36262074 Check |pmid= value (help).
  15. ↑ Tovar Forero MN, Sardella G, Salvi N, et al. (2022). "Coronary lithotripsy for the treatment of underexpanded stents: the international & multicentre CRUNCH registry". EuroIntervention. 18 (7): 574–581. doi:10.4244/EIJ-D-21-00545. PMID 35318955 Check |pmid= value (help).
  16. ↑ Kirtane AJ, Généreux P, Lewis B, et al. (2025). "Orbital atherectomy versus balloon angioplasty before drug-eluting stent implantation in severely calcified lesions eligible for both treatment strategies (ECLIPSE): a multicentre, open-label, randomised trial". Lancet. 405 (10486): 1240–1251. doi:10.1016/S0140-6736(25)00450-7.
  17. ↑ Kereiakes DJ, Di Mario C, Riley RF, et al. (2021). "Intravascular Lithotripsy for Treatment of Calcified Coronary Lesions: Patient-Level Pooled Analysis of the Disrupt CAD Studies". JACC Cardiovasc Interv. 14 (12): 1337–1348. doi:10.1016/j.jcin.2021.04.015. PMID 34167671 Check |pmid= value (help).
  18. ↑ Hill JM, Kereiakes DJ, Shlofmitz RA, et al. (2020). "Intravascular Lithotripsy for Treatment of Severely Calcified Coronary Artery Disease". J Am Coll Cardiol. 76 (22): 2635–2646. doi:10.1016/j.jacc.2020.09.603. PMID 33069849 Check |pmid= value (help).
  19. ↑ Blachutzik F, Meier S, Weissner M, et al. (2023). "Comparison of Coronary Intravascular Lithotripsy and Rotational Atherectomy in the Modification of Severely Calcified Stenoses". Am J Cardiol. 197: 93–100. doi:10.1016/j.amjcard.2023.02.028. PMID 37182254 Check |pmid= value (help).
  20. ↑ Honton B, Motreff P, Mallet JS, et al. (2026). "Intravascular lithotripsy in comparison to rotational atherectomy for calcified lesions: the ICARE OFDI randomised trial". EuroIntervention. 22 (15): e808–e819. doi:10.4244/EIJ-D-26-00426. PMID 42200665 Check |pmid= value (help).
  21. ↑ 21.0 21.1 Levine GN, Bates ER, Blankenship JC, Bailey SR, Bittl JA, Cercek B, Chambers CE, Ellis SG, Guyton RA, Hollenberg SM, Khot UN, Lange RA, Mauri L, Mehran R, Moussa ID, Mukherjee D, Nallamothu BK, Ting HH (2011). "2011 ACCF/AHA/SCAI Guideline for Percutaneous Coronary Intervention: Executive Summary A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Society for Cardiovascular Angiography and Interventions". Journal of the American College of Cardiology. 58 (24): 2550–83. doi:10.1016/j.jacc.2011.08.006. PMID 22070837. Unknown parameter |month= ignored (help)
  22. ↑ Moussa I, Di Mario C, Moses J, Reimers B, Di Francesco L, Martini G, Tobis J, Colombo A (1997). "Coronary stenting after rotational atherectomy in calcified and complex lesions. Angiographic and clinical follow-up results". Circulation. 96 (1): 128–36. PMID 9236427. Unknown parameter |month= ignored (help)
  23. ↑ Vaquerizo B, Serra A, Miranda F, Triano JL, Sierra G, Delgado G, Puentes A, Mojal S, Brugera J (2010). "Aggressive plaque modification with rotational atherectomy and/or cutting balloon before drug-eluting stent implantation for the treatment of calcified coronary lesions". Journal of Interventional Cardiology. 23 (3): 240–8. doi:10.1111/j.1540-8183.2010.00547.x. PMID 20636844. Unknown parameter |month= ignored (help)
  24. ↑ Brogan WC, Popma JJ, Pichard AD, Satler LF, Kent KM, Mintz GS, Leon MB (1993). "Rotational coronary atherectomy after unsuccessful coronary balloon angioplasty". The American Journal of Cardiology. 71 (10): 794–8. PMID 8456756. Unknown parameter |month= ignored (help)
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