The exact incidence of chronic total occlusions (CTOs) during routine coronary angiography is not well defined. It has been reported in the literature that CTOs are encountered in approximately one-third of diagnostic cardiac catheterizations.1 Another registry found CTOs present in 52% of cases with significant coronary artery disease (> 70% stenosis).2 The frequency of attempted percutaneous revascularization is not well known. In one review, it accounted for only 8% of attempted revascularizations.1 One reason for this low attempt rate is the highly variable procedural success rate. This is directly influenced by the duration of the occlusion, lesion length, angle of takeoff, calcification, side branch at the site of occlusion and the presence of bridging collaterals, along with a host of other factors.3 Successful intervention on a CTO has been associated with a decrease in the combined endpoint of death or myocardial infarction (MI), referral for coronary artery bypass graft surgery (CABG) and anginal symptoms.4 We report a case of a difficult CTO where the use of an uncommon approach led to procedural success.
Case Report. A 66-year-old white male with a past medical history significant for type 2 diabetes and smoking presented to an outside medical center with the complaint of stuttering chest pain. The pain then recurred the day of presentation and was constant. The patient’s pain was described as a dull ache in the center of his chest with radiation to the left arm. Associated shortness of breath was reported, but no relieving or exacerbating factors were described.
At the outside hospital, 1 mm ST-segment elevation was noted in precordial leads V1–V3 on electrocardiography (ECG). A chest Xray showed no mediastinal widening or air space disease. His home medications were glipizide, metformin, escitalopram and omeprazole. He denied any family history of premature cardiovascular disease. He has worked as a welding inspector and has smoked 2–3 packs of cigarettes per day for the past 40 years. The patient denied alcohol or illicit drug use.
Due to the stuttering nature of the pain and ECG changes, the patient was transferred to our institution for emergent cardiac catheterization. On arrival, physical examination showed an overweight white male, hemodynamically stable, in mild distress. He had no jugular venous distention and no carotid bruits. His cardiac examination revealed a regular heart rate with no apparent murmur, gallop or pericardial rub. His lung fields were clear to auscultation, his extremities had good pulses without femoral bruits and no peripheral edema was evident. A bedside echocardiogram showed normal left ventricular systolic function with mild hypokinesis of the anterior wall and apex. His initial troponin-I level was mildly elevated at 0.2 ng/ml.
The patient was taken to the cardiac catheterization laboratory where angiography revealed a totally occluded mid-left anterior descending artery (LAD) with severe calcification and evidence of minimal contrast staining. The site of the occlusion was at an acute angle just distal to the origin of a large diagonal branch, which had moderate ostial disease (Figure 1). There was faint filling of the LAD via right-to-left collaterals. No other coronary lesions were noted.
Due to the absence of other coronary stenoses and his ongoing chest pain, the decision was made to proceed with PCI to the LAD. An 8 Fr XB 3.5 guiding catheter was used to engage the left main artery. Multiple attempts to cross the LAD occlusion were unsuccessful despite the use of several wires and balloon support, with the wire prolapsing into the patent diagonal branch. This was mainly due to the angulation of the vessel with a very short straight segment proximal to the lesion, as well as calcification at that site. The behavior of the lesion was more consistent with a CTO rather than an acute occlusion. It is possible this might have been an acute occlusion superimposed on a previous severely calcified stenosis.
A wire was then placed in the large diagonal branch over which a Twin-Pass catheter (Vascular Solutions, Inc., Minneapolis, Minnesota) was introduced. The second port of the Twin-Pass catheter was then placed close to the LAD occlusion and a Shinobi wire (Cordis Corp., Miami Lakes, Florida) was advanced through it. The Twin-Pass catheter was used as an anchor to support the Shinobi wire (Figure 2). The lesion was successfully crossed and dilated. Stent implantation was then performed using a crush technique for the bifurcation (Figures 3A and B). The final angiographic result was excellent (Figure 4).
Discussion. This is an interesting case presentation of an acute coronary syndrome, but with angiographic and interventional characteristics more consistent with chronic pathology. Although the LAD lesion behaved as a CTO during PCI, this could have been an acute occlusion on top of a severely calcified stenosis. In the setting of collateral flow and normal systolic function, conservative medical therapy could have been a reasonable alternative to percutaneous coronary intervention. Nonetheless, the technical challenges of crossing such a lesion were quite similar to crossing a CTO. Several different strategies have been employed to achieve procedural success in the situation mentioned above.
In cases of difficult CTO interventions, adequate guide support is paramount. The choice of the guiding catheter, given the characteristics of the aortic root as well as the origin of the coronary arteries is of utmost importance.
Percutaneous recanalization of occluded coronary arteries has improved significantly with the development and refinement of techniques and devices for this challenging lesion subset. Fundamental to these are guidewires specifically designed for crossing total occlusions. Optimal wire selection may make the difference between procedural success and failure. Wires for chronic occlusions have increased stiffness and excellent torque control compared to frontline or workhorse wires. The stiffness of these wires is measured on scale in grams (gm). Such stiff wires have the capacity to cross occlusions, but can easily penetrate, cross and create an extra-arterial course.
Two groups of wires are usually used for CTOs: polymercoated and coil wires. Polymer-coated wires have a hydrophilic coating,5 which means they attract very little resistance passing through the lesion. Hydrophilic-coated guidewires, listed by increasing tip stiffness, include the Whisper wire, 1–2 gm tip stiffness (Guidant Corp., Santa Clara, California), the ChoICE PT6 and PT-Graphix 2–4 gm (Boston Scientific Corp., Natick, Massachusetts), the Pilot 50, 100 and 150 series, with 2–4 gm (Guidant), and the Shinobi and Shinobi Plus 2–4 gm.7
Coil wires have good torqueability, even inside the CTO segment, with good pushability. Simple stiff wires include the High Torque Intermediate and standard guidewires with 2–4 gm tip stiffness (Guidant) and the line of Miracle wires with 3–12 gm tip stiffness (Asahi Intecc, Aiichi, Japan). Heavier coil wires like the Cross-It 300–400 (Abbott Vascular, Abbott Park, Illinois) and Miracle 9–12 gm are reserved for extremely difficult cases.8
Recently, tapered-tip wires9 like the Confianza (Asahi) 0.009–0.014 inches, Confianza Pro (Asahi) and Cross-It XT series 0.014–0.019 inches have been introduced to penetrate and cross occlusions. Using these specific wires requires close attention by the operator to reduce the chance of creating a false lumen, to recognize when a false lumen is created and to avoid perforations.
The use of over-the-wire systems is especially beneficial to provide support for the wire, allow the exchange of wires with different characteristics, as well as confirm the intraluminal position of the wire/balloon after crossing the lesion through a distal port injection.
Different strategies have been developed to negotiate a chronically occluded vessel. Two wire techniques (parallel-wire method, see-saw wire method), subintimal tracking and reentry technique, the retrograde wire approach and recanalization, and anchor-wire techniques are some of the novel methods used. In cases of side-branch origin at the site of lesion, occluding the branch vessel with a balloon while advancing a wire down the CTO vessel has also been used in cases where the wire may prolapse in the patent branch (anchor-wire technique). The use of multiple wires has also been proposed, with one wire obliterating the blind channel or the false lumen, while attempting to penetrate the true lumen with another wire (parallel-wire method). A wide variety of devices has been developed to improve procedural success while attempting percutaneous revascularization of CTOs. The Safe-Cross Radiofrequency (RF) system (IntraLuminal Therapeutics, Inc., Carlsbad, California)10 combines optical coherence reflectometry (OCR) technology with a controlled RF energy that the operator can discharge through the wire tip. The Frontrunner catheter (LuMend Inc., Cordis, J&J)11 is designed to create intraluminal blunt microdissection to facilitate penetration of the fibrous lesion. The Tornus device (Asahi Intecc)12 is a catheter made up of 8 stainless steel strands woven together to enhance flexibility and strength when exchanging wires, delivering balloons and providing support for CTO procedures. The Prima laser guidewire system (Spectranetics Corp., Colorado Springs, Colorado)13 consists of an 0.018 inch hypotube containing a bundle of 45 micron optical fibers coupled to a pulsed excimer laser. The Venture wire control catheter (Velocimed, Minneapolis, Minnesota)14 facilitates negotiating difficult angles due to the ability to vary the angulation of the tip of the catheter.15 The Crosser (FlowCardia, Inc., Sunnyvale, California),16 a novel device dedicated to recanalization of CTOs, relies on a monorail catheter delivering vibration energy to facilitate the crossing of occluded coronary arteries. Another novel approach is the biologic one, in which proteolytic enzymes digest the CTO cap to facilitate mechanical passage.
Conclusion. Interventionists will encounter a wide variety of CTO cases in terms of lesion length, angulations, branch vessels, bridging collaterals and calcification. Special expertise is thus needed to differentiate between the varying anatomic situations, selecting the appropriate devices, ability to change strategies as the case progresses and maintaining safety by avoiding, recognizing and managing potential complications.
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