116 Practical Handbook of Advanced Interventional Cardiology and the catheter should be well fl ushed before starting the procedure. The catheter should be positioned on a straight line, to minimize any friction with the wire. 4 **Balloon angioplasty of large vessels: Current maxi- mal balloon size is 4 mm in diameter, so when the coronary artery or the SVG is larger than 4 mm, the hugging balloon technique or use of a peripheral balloon is suggested. The two balloons are positioned side by side and infl ated simul- taneously. The combined diameter will be 70% of the sum of each balloon alone and the cross-section area will be oval rather than round. 5,6 TROUBLE-SHOOTING TIPS *How to cross a lesion: The standard maneuver is to ad- vance a balloon with the left hand while pulling the wire taut with the right hand (or with the help of an assistant). This technique is to decrease the friction between the wire and the lumen of the balloon catheter. It also helps to keep the wire straight and taut so the balloon catheter can slide more easily on it. **Failure to cross a lesion: The causes of failure to advance a balloon across a tortuous segment in order to reach a lesion are multiple. If the lesion is too severe, the balloon tip will not cross, and the guide will back out; then the guide should be held steady, engaged deeper or be replaced. If there is excessive tortuosity of the arterial seg- ment proximal to the lesion, the solutions are (1) to secure a more stable position of the guide, or (2) to use a stiffer wire for the balloon to be tracked on, or (3) to straighten the artery by asking the patient to take a deep breath, or (4) using a “buddy wire”, placed adjacent to the primary wire. A “wiggle” wire is useful at defl ecting the tip of the balloon of plaques and stent struts, better allowing lesions to be crossed. A smaller balloon with a lower profi le or length may also succeed in crossing a tight lesion. Once infl ated, it creates a channel suffi cient for the optimal size balloon to enter. The different methods for advancing a balloon across a tight lesion are listed below. BEST METHOD Advancing a balloon across a tight lesion: 1. First maneuver: Check the guide position, optimize coaxial alignment, deep-seat the guide if needed, so the guide can provide suffi cient support for advancing the balloon. Balloon Angioplasty 117 2. Second maneuver: As k p at ie nt t o t ak e a de e p b rea th in order to elongate the heart and make the artery less tor- tuo us. Dur ing thi s sh or t wind ow of o pp or tunit y, ad van ce the balloon. This maneuver works best in the RCA. 3. Add a second device: If the balloon could not be ad- vanced because of tortuous proximal segments and if the fi rst two maneuvers fail to advance the balloon, then insert a second (moderately stiff) wire to straighten the proximal segment and most likely it will help to advance the balloon. 4. Change one device: Use a stiffer wire so the arte- rial segments are straightened and the balloon can be tracked on more easily. The disadvantage of this tactic c om pa re d to ad di ng a s ec on d w ir e i s t he ne ed to r em ove the fi rst wire and exchange for a second wire. Tactic (3) above just involves inserting a new wire, so it is simpler and faster. However, if tactic (3) fails to advance the bal- loon, then the balloon may slide better on the second, stiffer wire. 5. Change to an expensive device: Use a lower profi le balloon (monorail, compliant balloon material, center marker). **Failure to dilate a lesion: A rigid lesion with heavy cal- cifi cation may prevent the full expansion of a balloon. The fi rst choice is high pressure infl ations with a non-compliant balloon. It may be successful but it exposes the patient to the risk of dissection or balloon rupture. The second choice is to use a cutting balloon (CB). If the CB is not available then force-focused angioplasty with an extra wire besides the infl ated balloon can be used. In lesions with heavy superfi cial calcium, the problem can be resolved with debulking by rotational atherectomy, followed by low-pres- sure angioplasty. The cutting balloon is the best option in PCI of the undilatable lesion, because the use of rotational atherectomy has become uncommon due to concerns over excessive debris embolization. The different options are listed below. BEST METHOD When a balloon fails to dilate a lesion: 1. First maneuver: High pressure infl ation of non-compli- ant balloon. This balloon should be selected right from the start of the procedure. Now just infl ate the balloon to its maximal pressure possible. 2. Add one device – force-focused angioplasty: Insert a second wire across the lesion and infl ate the non-com- pliant balloon. The pressure will focus on the second wire and break the plaque. This tactic is better than 118 Practical Handbook of Advanced Interventional Cardiology angioplasty with a cutting balloon because it is cheaper (one extra wire) and may be the only possible choice (it is diffi cult or impossible to advance a stiff cutting balloon across a tortuous segment). 3. Change one device: If the non-compliant balloon fails to dilate the lesion at high pressure then cutting balloon angioplasty is the next best choice if it can be advanced across the lesion. 4. Add a new device – rotational atherectomy: Al- though rotablation is excellent in shaving the superfi cial calcium from the plaque and making it susceptible to dilation by balloon angioplasty or stent, this technique is out of favor because of excessive debris embolization causing release of cardiac enzymes. **Force-focused angioplasty: If the balloon fails to break a plaque, it is withdrawn into the guide. A second wire is advanced beyond the lesion. The balloon is readvanced, positioned across the lesion, and infl ated as usual. With the wire across the lesion, the pressure is then focused on the wire, which then acts as a cutting wire to selectively put pressure and crack the plaque. Complications include dis- section, which can be treated by stenting. 7 It is best done with an undersized non-compliant balloon that allows the operator to go to high pressures without concerns of bal- loon oversize relative to vessel size or balloon rupture. **Manipulating the cutting balloon: Because of the presence of the microblades at its side, the cutting balloon is quite stiff, and is diffi cult to curve around sharp bends. To overcome this problem, the cutting balloon is designed with very short length (10 mm). While dilating the cutting balloon, a slow infl ation strategy is used. There should be 3–5 seconds interval between each atmosphere increase, to ensure that the peripheral balloon wings unfold slowly, fi rst around the blades, before infl ation of the central core of the balloon. Rapid infl ation could result in the blades punc- turing the balloon. The cutting balloon is effective in PCI of patient s listed i n Tab le 6 -1. ***Extraction of stent by cutting balloon: The CB has its blades mounted along its length. During infl ation, the Table 6-1 Indications for use of cutting balloon 1. Aorto-ostial lesion 2. Bifurcation lesion 3. Restenotic lesion 4. Highly resistant lesions Balloon Angioplasty 119 blades are protruded outwards and exposed. Then, during defl ation, there is a mechanism for rewrapping the balloons with multiple wings. During this process of rewrapping, there is possibility of the creation of an anchor formed by the balloon and the blades or just because the higher profi le balloon is strengthened with the blades. This recess can get stuck into the stent struts and prevent withdrawal of the CB. If the CB is pulled strongly enough it could pull with it the stent or part of the stent. Because the lumen of the artery is removed with the stent, the lumen can become avulsed and have acute occlusion. 8,9 **Failure to defl ate the balloon: Inability to defl ate the bal- loon is a rare occurrence. Possible causes are excessive twisting (more than 360°) in order to cross a distal lesion 10 or entrapment in the distal portion by a tight lesion. Usual maneuvers to defl ate the balloon are listed in Table 6-2. After exhausting all maneuvers without success, one rarely used measure is to bring a new over-the-wire balloon immediately next to the entrapped and infl ated balloon. Re- verse the wire by reinserting the back end fi rst. Infl ate the new balloon at low pressure to position the sharp tip of the wire at the center of the vessel lumen. Try to puncture the in- fl ated balloon with the back end. A 190-cm wire which has a tapered back end to allow extending may be most effective in puncturing. Although there is a risk of coronary perfora- tion, the hole would be quite small and unlikely to cause any signifi cant complication. In addition, vessel trauma from balloon rupture can be much more extensive and more uncontrolled than a single pinhole puncture. 12 ***Impending rupture due to material fatigue: Besides rupture due to excessive infl ation or calcifi ed plaque, an- other cause of rupture is material fatigue. 11 Balloon fatigue generally occurs after numerous infl ations and defl ations of a re-used balloon – seen frequently outside the US. As the balloon material undergoes fatigue, a focal bulging in the balloon during infl ation may be observed. It is sug- Table 6-2 Technical options when the balloon fails to defl ate 1. Defl ate the balloon with the infl ation device. 2. Defl ate the balloon with a 50 cc syringe directly at the infl ation port. 3. As a last resort, infl ate the balloon to rupture it. Prepare for damage control from dissection or coronary perforation. 11 4. Surgical removal of balloon. 5. Investigational: puncture the balloon with the back end of a wire. 120 Practical Handbook of Advanced Interventional Cardiology gested that when faced with an unyielding stenosis, infl a- tion pressure suffi cient to cause balloon rupture should be avoided. 13 ***Entrapment of defl ated balloon during withdrawal: Even though the incidence of entrapment of a defl ated balloon is low, once it happens, it is quite traumatic to the patient, operator, and the interventional team. The entrap- ment can happen in an unpredicted way. Different options for management are listed in Table 6-3. There are no best options. Different modalities of treatment can be attempted on a trial-and-error basis. ***Using a commercial snare to remove a balloon: Cut the proximal end of the balloon catheter. Advance the snare using the balloon catheter as a wire. Once arriving at the entrapped balloon site, loop the snare around the balloon, tighten the loop by advancing the transport catheter, and pull the snare and the catheter end to free the balloon. 16 Be prepared to unwrap the snare and pull it back alone if it is not able to remove the trapped balloon. ***Management of repeated rupture: Balloon rupture can happen repeatedly as in a case reported by Gilutz et al. In a patient with ISR, three balloons were ruptured during Table 6-3 Management of entrapment of balloon after infl ation 1. Pull the balloon back more forcefully. 14 2. Push the balloon forward then pull it back. 3. Twist the balloon in an attempt to rewrap the balloon before pulling back. 4. Insert a stiffer wire alongside the entrapped balloon before pulling the balloon back so the artery can be more straightened. 5. Advance and infl ate any new balloon alongside the entrapped balloon, or at least in the proximal vicinity, to prepare a pathway so the entrapped balloon can be withdrawn. 15 6. Advance a second wire distally, then insert an over-the- wire balloon alongside the entrapped balloon, and infl ate the new balloon at low pressure to free the entrapped balloon. 7. If the over-the-wire balloon cannot be advanced, then advance a balloon-on-a-wire alongside the entrapped bal- loon and infl ate it to free the entrapped balloon. 8. Advance a commercial microsnare, and tighten the loop near the balloon as much as possible, then pull the bal- loon back as any embolized material. 16 Balloon Angioplasty 121 infl ation. IVUS study showed a ridge of calcium protruding into the lumen. Management of this problem includes use of stronger balloon, rotational atherectomy, which can be problematic because it can ablate the metallic stent struts, or, as in t his ca se rep or t, CABG. 17 ***Damage control for balloon rupture: Balloon rupture is seen under the fl uoroscope as a quick dispersion of contrast agent from the balloon, with short contrast opaci- fi cation of the vessel or decrease in the infl ation pressure. When this occurs, slowly withdraw the balloon proximal to the lesion and inject some contrast to detect whether there is perforation. The balloon is then removed if not entrapped in the lesion. Stenting should be performed if there is dis- section. CONCLUSION Balloon angioplasty is the basic technique of coronary intervention. In many situations it is the only one available, for example, in intervention in small vessels, very tortuous arteries, ISR, bifurcation, and AMI. It is still the only procedure available in many developing countries because of the high cost of stent. Manipulation of a balloon and opening an artery without causing complications requires more than technical skill. Balloon angioplasty is an art: how to unblock diseased arteries in a cost- and time-effective manner. REFERENCES 1. Ellis S. Elective coronary angioplasty: Techniques and complications. In: Topol E, ed. Textbook of Interventional Cardiology, 3rd edition. WB Saunders, 1999. 2. King SB. Complications of angioplasty. In: King SB, Doug- las JS, eds. Atlas of Heart Diseases: Interventional Cardiol- ogy. Mosby, 1997: 12.1 –12.15. 3. Meier B. Balloon angioplasty. In: Topol E, ed. Textbook of Cardiovascular Medicine. Lippincott-Raven Publishers, 1998: 1983. 4. Nanto S, Ohara T, Shimonagata T et al. A technique for changing a PTCA balloon catheter over regular length guide- wire. Cathet Cardiovasc Diagn 1994; 32: 274–7. 5. Krucoff MW, Smith JE, Jackman JD et al. “Hugging bal- loons” through a single 8F guide: Salvage angioplasty with lytic therapy in the IRA of a 40-year-old man. Cathet Cardio- vasc Diagn 1991; 24: 45–50. 6. Feld H, Valerio L, Shani J. Two hugging balloons at high pressures successfully dilated a lesion refractory to routine 122 Practical Handbook of Advanced Interventional Cardiology coronary angioplasty. Cathet Cardiovasc Diagn 1991; 24: 105–7. 7. Yazdanfar S, Ledley GS, Alfi eri A et al. Parallel angioplasty dilation catheter and guide wire: A new technique for the dila- tion of calcifi ed coronary arteries. Cathet Cardiovasc Diagn 1993; 28: 72–5. 8. Kawamura A, Asakura Y, Ishikawa S et al. Extraction of previously deployed stent by an entrapped CB due to blade fracture. Cathet Cardiovasc Interv 2002; 57: 239–43. 9. Harb T, Ling F. Inadvertent stent extraction six months after implantation by an entrapped cutting balloon. Cathet Cardio- vasc Interv 2001; 53: 415–19. 10. Hamada Y, Matsuda Y, Takashiba K et al. Diffi cult defl a- tion of Probe balloon due to twisting of the system stenosis. Cathet Cardiovasc Diagn 1989; 18 : 12–14. 11. Breisblatt WM. Infl ated balloon entrapped in calcifi ed cor- onary stenosis. Cathet Cardiovasc Diagn 1993; 29: 224–8. 12. Personal communication with Khoi Le MD, Palm Spring CA. 13. Kussmaul III WG, Marzo K, Tomaszewski J et al. Rupture and entrapment of a balloon catheter in the LAD: Fluoroscopy of impending balloon rupture. Cathet Cardiovasc Diagn 1993; 19 : 256–9. 14. Rizzo TF, Werres R, Ciccone J et al. Entrapment of an an- gioplasty balloon catheter: A case report. Cathet Cardiovasc Diagn 1988; 14: 255–7. 15. Colombo A, Skinner JM. Balloon entrapment in a coro- nary artery: Potential serious complications of balloon rup- ture. Cathet Cardiovasc Diagn 1990; 19 : 23–5. 16. Watson LE. Snare loop technique for removal of broken steerable PTCA wire. Cathet Cardiovasc Diagn 1987; 13: 44–9. 17. Gilutz H, Weistein J. Repeated balloon rupture during coronary stenting due to a calcifi ed lesion: An IVUS study. Cathet Cardiovasc Interv 2000; 50: 212–14. 123 Structural designs and functional expectations Engineering criteria for stent evaluation Practical clinical evaluation of a stent Advancing a stent BEST METHOD: When a stent fails to advance **To secure a stent on a balloon ***Hand-crimp a stent on a balloon with the tip partially infl ated **Partial infl ation of the balloon in order to cross tortuous segment **Testing the road **The “buddy wire” technique ***Bend the wire **How to calculate the location of the bend **The buddy balloon technique Deploying a stent TAKE-HOME MESSAGE: Direct stenting **Predilating balloon angioplasty in the DES era ***Deploying a stent from the radial approach ***Redeploying an embolized stent ***Balloon rupture **Avoid high pressure post-dilation in the DES era **Deployment of a stent in a tortuous artery ***Stent deployment after balloon rupture ***How to prevent damage from balloon rupture CAVEAT: Check the integrity of the balloon before de- ployment **Appropriate sizing for tapering artery **Overlapping stent in the DES era Redeploying a stent BEST METHOD: How to cross a crushed stent *Basic; **Advanced; ***Rare, exotic, or investigational. From: Nguyen T, Hu D, Saito S, Grines C, Palacios I (eds), Practical Handbook of Advanced Interventional Cardiology, 2nd edn. © 2003 Futura, an imprint of Blackwell Publishing. Chapter 7 Stenting Thach Nguyen, Jia Sanqing, Wang Lei, Yan Songbiao 124 Practical Handbook of Advanced Interventional Cardiology BEST METHOD: Redeploy a stent after failed expansion by balloon BEST METHOD: Redeploy a stent after failure of stent expansion Recrossing a stent BEST METHOD: Recrossing a stented area by a balloon or stent **Dottering for recrossing a newly stented area ***Other exotic techniques ***First balloon defl ecting second balloon from problem- atic area ***Recrossing a stent with a bent stiff wire CAVEAT: Manipulation near a previously deployed stent Side branch dilation ***Opening of a stent at its side by balloon infl ation ***Mechanisms of side opening following dilation ***Main lumen distortion and restoration following dila- tions CAVEAT: Entrapment of a balloon during side branch dilation ***Entr apmen t of the distal ti p of an IVUS cath eter Stent deformations TAKE-HOME MESSAGE: Perfect stenting in the era of drug- eluting stents STRUCTURAL DESIGNS AND FUNCTIONAL EXPECTATIONS As a clinical cardiologist must know the pharmacologic properties of a new cardiovascular drug or the mechanism of a new therapeutic device, interventional cardiologists must understand the basic physical or bioengineering principles of stenting so that the most suitable stent for a given lesion can be selected. Easy delivery = high longitudinal fl exibility + low pro- fi le: A stent mounted on a delivery balloon should be able to negotiate easily the tortuous segments proximal to the target site, without injuring the intima or eliciting spasm. This smooth delivery is termed high trackability as a stent is passed easily over a wire. The two properties, high longitudinal fl exibility and low profi le, help to bring the stent to the target site within an al- lotted time frame and with minimal manipulation. A stent can easily cross an angulated segment if its length can fi t in the widest interval at the curve. If it is longer, it can be advanced as long as it can be bent or curved, or the arterial segment is not too calcifi ed to relax and compliantly accom- modate the stent. Perfect deployment = great radial strength and curve conformity: Once deployed, a stent must have suffi cient ra- dial strength to resist the elastic recoil of the media and of the Stenting 125 shifting plaque. In an emergency situation, it has to be strong to seal the entry of a dissection, patch a dissecting fl ap, or brace against the persistent compression of a growing intra- mural hematoma. In addition, an adaptively deployed stent would mold its shape along the contour of a curved segment rather than straighten it and still provide a large desired lu- men. These two properties of a deployed stent, great radial strength and curve conformity, would give an instant perfect angiographic result. Following deployment, the struts should be well imbedded into the arterial wall and stop any systolic contraction or diastolic relaxation. Therefore, they effectively immobilize the stented arterial segment and prevent any on- going injury to the intima, which is the nidus for any endothelial thrombotic formation. Excellent apposition of the struts on the vessel wall will guarantee the delivery of the cytostatic drug preventing intimal hyperplasia. No subacute thrombosis = high acute gain: While re- stenosis following angioplasty typically is caused by a combi- nation of early elastic recoil, intimal hyperplasia (IH), and late vessel remodeling, the primary cause of restenosis following stenting is excessive IH and late negative remodeling. By serving as a rigid metallic frame, stents prevent early elastic recoil and late remodeling. Therefore, the largest achievable lumen diameter at the acute phase may help to avoid subacute thrombosis, and overcome late lumen loss. With the advent of DES, late restenosis is effectively prevented by cytostatic drugs coated on the stent struts. ENGINEERING CRITERIA FOR STENT EVALUATION Longitudinal fl exibility: In the coil design, a single wire is coiled in different curves and crimped tightly around a de- fl ated balloon. It has no longitudinal strut so it uses the delivery balloon as a platform for its struts to be positioned on the lon- gitudinal plane. Without stiff longitudinal shafts, the coil stent is very fl exible. In the tubular design, the primary mechanism for fl exibility is that the longitudinal struts should be rather short and interrupted while the circular struts should be bent or folded and positioned sideways along the longitudinal axis, before deployment. This arrangement of struts makes a stent high ly fl exible d uring d eliver y. Radial strength: At the target site, the balloon is infl ated to deploy the stent. In the tubular design, the struts that were previously longitudinal or folded along the length of the stent rotate outward away from the long axis, and become the circumferential struts. In the coil design, the circumferential loops are just stretched wider to attain the desired diameter. Because they are incomplete loops, their radial strength is lower, as evidenced by 15% –20% loss of achieved diameter due to intrinsic recoil. [...]... the integrity of the balloon should be checked prior to advancement (Table 7-5 ) In the case of a hand-crimped stent, the balloon-stent complex can be checked again when the stent is at the tip of the guide, before engaging the coronary artery, so there is still time to retrieve it if needed.14 138 Practical Handbook of Advanced Interventional Cardiology Table 7-5 Checking the integrity of a balloon... Practical Handbook of Advanced Interventional Cardiology Table 7-1 Other options when a stent fails to advance Wire manipulations 1 Shape the wire along the curve of the artery in order to lessen wire bias, so there is less friction or resistance at the outer curve of the vessel and the path of the wire is more coaxial with the path of the vessel (rare) Stent manipulations 2 Partial stent-balloon inflation... of the guide Table 7 -3 Factors favoring successful direct stenting 1 2 3 4 5 Young age . are. (Courtesy of the Cardiac Catherization Laboratories of The Heart Institute, National University Hos- pital, Singapore.) C 132 Practical Handbook of Advanced Interventional Cardiology Nitinol. deployed. There was dissection at the distal end of newly deployed stent at the mid-LAD. (Continued) A 130 Practical Handbook of Advanced Interventional Cardiology case report, there is one common. Complications of angioplasty. In: King SB, Doug- las JS, eds. Atlas of Heart Diseases: Interventional Cardiol- ogy. Mosby, 1997: 12.1 –12.15. 3. Meier B. Balloon angioplasty. In: Topol E, ed. Textbook of