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Complex Coronary Intervention
Calcium Modification &
Complex Angioplasty
Severely calcified coronary arteries resist stent expansion — the single most common cause of stent failure. Dr Nijjer performs the full range of calcium modification techniques, from scoring balloons to shockwave lithotripsy, rotational atherectomy, and orbital atherectomy, selecting the right tool for each patient based on intracoronary imaging.
C 
The Challenge of Calcified Coronary Disease
Why Calcium Must Be Treated Before Stenting
Calcium deposits within coronary plaque are as hard as bone. When a stent balloon inflates inside a heavily calcified artery, the calcium resists expansion — the stent cannot fully open to its intended diameter, leaving it underexpanded in the segment surrounded by calcium. Underexpansion is the leading cause of in-stent restenosis (re-narrowing) and stent thrombosis, and cannot be reliably detected on angiography alone.
Intracoronary imaging with IVUS or OCT measures the arc and depth of calcification before treatment — information that directly determines which modification technique will be most effective. Heavy circumferential calcium covering more than 270° of the vessel circumference reliably predicts stent underexpansion and mandates specific treatment before any stent is placed.
The goal of calcium modification is not to remove the plaque entirely but to fracture or debulk the calcified shell sufficiently that a stent balloon can subsequently inflate the vessel to its true diameter. Different technologies achieve this in different ways — ablation, acoustic fracture, scoring, or cutting — and each has specific advantages depending on the calcium pattern, vessel anatomy, and clinical context.
Dr Nijjer's approach. Dr Nijjer performs the full spectrum of calcium modification techniques as part of his complex coronary intervention practice at Hammersmith Hospital and One Heart Clinic. Every case is planned with intracoronary imaging (IVUS and OCT) to characterise calcium severity and guide technique selection. Post-modification imaging confirms stent expansion has met the target before the procedure ends.
Calcium Modification Techniques
Treatment Options
Four distinct classes of technology are used for calcium modification. Selection is based on calcium arc and depth on imaging, vessel anatomy, ability to cross the lesion, and operator experience. Techniques can be combined sequentially in the most complex cases.
NC / SC
Non-Compliant, Scoring & Cutting Balloons
Superficial calcium
Non-compliant (NC) balloons are made from inelastic materials that maintain their size at high pressures, delivering a focused radial force against resistant plaque. Scoring balloons (such as AngioSculpt) carry spiral nitinol wire elements around their surface that concentrate stress onto the plaque and create longitudinal scores during inflation. Cutting balloons have three or four microsurgical atherotomes — tiny metal blades — that make precise longitudinal incisions as the balloon inflates. The OPN Super NC balloon achieves the highest inflation pressures available in a coronary system, up to 35 atmospheres, for lesions that resist standard high-pressure dilatation.
Best forMild-moderate superficial calcium; adjunctive treatment after atherectomy; in-stent restenosis
EvidenceEstablished standard of care; extensive trial database across lesion types
- No specialist equipment required beyond standard catheter laboratory
- Fast and straightforward to use in any coronary anatomy
- Scoring balloons reduce slippage and balloon watermelon effect in fibrocalcific lesions
- OPN balloon achieves pressures inaccessible to standard balloons
Limited effect on deep or circumferential calcium; cannot treat lesions that cannot be crossed with a balloon
IVL
Intravascular Lithotripsy — Shockwave
Superficial calcium Deep calcium
A balloon catheter containing multiple piezoelectric emitters is positioned across the calcified lesion and inflated to a low pressure of 4 atmospheres. High-voltage electrical pulses vaporise a small fluid-filled reservoir within the balloon, generating powerful omni-directional acoustic pressure waves — the same physical principle used in kidney stone lithotripsy. These shockwaves pass harmlessly through soft tissue and blood but selectively fracture both superficial and deep calcium within the plaque wall. The balloon is then inflated to higher pressure to dilate the now-modified lesion before stenting.
Best forConcentric deep calcium; moderate-to-severe calcification; tortuous vessels unsuitable for atherectomy
EvidenceDISRUPT CAD I, II, III trials — 92% procedural success; <1% perforation rate
- The only technique that effectively fractures deep intimal and medial calcium
- No ablation debris — calcium is fractured in situ, not removed
- Can be used in tortuous vessels where rotablation is contraindicated
- Simple to use — similar technique to standard balloon angioplasty
- Minimal risk of slow flow or vessel perforation
Requires the lesion to be crossed with the balloon catheter; less effective for very dense nodular calcium requiring debulking before delivery
ROTA
Rotational Atherectomy — Rotablator
Superficial calcium
A diamond-coated metal burr, ranging from 1.25 mm to 2.5 mm in diameter, is driven at 135,000–180,000 rpm by a compressed nitrogen turbine. The burr uses the principle of differential cutting: its high-speed rotation ablates hard, calcified plaque while the elastic properties of soft tissue allow it to deflect away from the burr surface, protecting the vessel wall. Ablated calcium is ground into micro-particles smaller than 5 microns — smaller than a red blood cell — which pass harmlessly through the coronary microcirculation. Rotablation modifies the superficial calcium shell to allow subsequent balloon and stent delivery.
Best forFibrocalcific lesions that cannot be crossed or dilated; ostial lesions; heavy superficial calcium with balloon under-delivery
EvidenceOver 25 years of clinical evidence; established guideline-recommended technique for undilatable lesions
- Improves catheter and stent deliverability through previously impassable lesions
- Highly effective debulking of fibrocalcific plaque
- Most widely available atherectomy technique in UK centres
- Can be combined with IVL for very complex calcium (ablate then shockwave)
Not suitable in tortuous vessels, significant angulation (>45°), thrombus-containing lesions, or severely reduced LV function; risk of slow flow/no-reflow requires preparation
OA
Orbital Atherectomy — Diamondback 360°
Superficial calcium Some deep calcium
A single diamond-coated crown (1.25 mm) is mounted eccentrically on a flexible drive shaft and spins at two speeds — 80,000 rpm (low orbit) and 120,000 rpm (high orbit). Unlike rotational atherectomy, which rotates a burr along the vessel axis, orbital atherectomy generates an eccentric orbital motion: the crown swings in widening arcs as speed increases, contacting the vessel wall across a wider surface area. This allows one crown size to treat vessels of varying diameters by adjusting the orbital radius with speed, and creates a larger effective ablation channel than a comparably-sized rotablation burr.
Best forModerate-severe calcium; eccentric plaque distribution; ostial lesions; cases where rotablation size matching is challenging
EvidenceORBIT I and II trials — high procedural success with low perforation and slow-flow rates
- Single crown size treats the full range of coronary vessel diameters
- Eccentric orbit produces a larger ablation channel relative to crown size
- Bidirectional rotation reduces the risk of crown entrapment
- The orbital motion pattern may provide more uniform calcium disruption than a fixed-axis burr
Less widely available than rotablation across UK centres; similar vessel anatomy contraindications apply (tortuosity, angulation)
Imaging-Guided Treatment Selection
Calcium Grading & Treatment Strategy
Matching the Tool to the Calcium
IVUS and OCT measure the calcium arc — the proportion of the vessel circumference affected — expressed in degrees. This measurement, combined with calcium depth (superficial vs deep on OCT), directly determines which modification strategy to use. The four grades below reflect current practice guidelines and intracoronary imaging trial data.
Grade 1 — Mild
< 90° arc · superficial or deep
<90°
High-pressure NC balloon post-dilatation · stenting generally achievable without modification
Grade 2 — Moderate
90–180° arc · predominantly superficial
90–180°
Scoring or cutting balloon pre-treatment → NC balloon → stent · IVL an alternative for deep component
Grade 3 — Severe
180–270° arc · superficial dominant
180–270°
Rotablation or orbital atherectomy → NC balloon → stent with imaging confirmation of MSA · IVL if deep calcium co-exists
Grade 4 — Circumferential
>270° arc · deep & superficial
>270°
IVL (deep fracture) ± rotablation (if uncrossable) → NC balloon → stent · Imaging essential throughout · Combined technique often required
What to Expect
The Procedure
01
Access & Angiogram
A sheath is placed in the radial or femoral artery under local anaesthetic. A diagnostic coronary angiogram outlines the coronary anatomy and identifies the target lesion. Heparin anticoagulation is administered. The overall procedure typically takes 60–120 minutes depending on the complexity of the calcium modification required.
02
Imaging Assessment
Before any treatment, an IVUS or OCT catheter is passed across the lesion to measure the calcium arc, depth, and lesion length precisely. These measurements determine stent size, length, and which modification technique is appropriate. This step takes 5–10 minutes but is the foundation for every subsequent decision.
03
Calcium Modification
The selected technique is applied — rotablation burr runs, orbital atherectomy passes, IVL pulses, or scoring balloon inflations. For atherectomy, the burr is advanced and withdrawn in smooth, controlled movements while monitoring speed and pressure. For IVL, the balloon delivers multiple 10-pulse cycles at the target site. A temporary pacemaker wire may be placed beforehand as a precaution for some techniques.
04
Stenting
After calcium modification, a drug-eluting stent is deployed at high pressure across the prepared segment, sized to the true vessel diameter identified on pre-procedure imaging. Further high-pressure non-compliant balloon post-dilatation optimises stent expansion. A second imaging run confirms that the minimum stent area has been achieved and that no significant edge dissection or malapposition is present.
05
Recovery
You are monitored on the ward for a minimum of four hours following the procedure. Most patients are discharged the same day or the following morning. Dr Nijjer will discuss the result with you before discharge, including the imaging findings and the final angiographic appearance. A follow-up appointment is arranged to review your medication, symptoms, and recovery.
Complex Coronary Disease,
Expert Treatment
Heavily calcified coronary arteries require specialist technique and technology. Dr Nijjer performs the full range of calcium modification procedures, guided by imaging, at Hammersmith Hospital and One Heart Clinic.