Case presentation

A 77-year-old woman presented to the hospital emergency department with chest pain at rest. Fourteen years earlier, she underwent coronary bypass surgery consisting of a left internal mammary graft to the left anterior descending artery and saphenous vein grafts to both the right coronary artery and the first obtuse marginal artery. She did well until 1 year earlier when she developed substernal chest pain occurring with exertion and relieved by rest. This symptom progressed and led to diminished exercise tolerance. Her physician evaluated her progressive anginal symptoms by pharmacologic stress perfusion scintigraphy, which confirmed ischemia in the inferior and lateral walls. Based on these results, her physician scheduled her for an outpatient elective cardiac catheterization. However, several prolonged episodes of rest chest pain resolving only after nitroglycerin prompted this hospital visit.

Upon arrival, her chest pain had already resolved and she did not report any other symptoms. In addition to the prior coronary bypass surgery, review of her past medical history was notable for the presence of a left bundle branch block on electrocardiogram, Factor V Leiden with several occurrences of deep vein thrombosis, hypercholesterolemia, and prior tobacco abuse. Home medications included warfarin, atenolol, aspirin, and fluvastatin. Physical examination found no abnormalities. Routine laboratory evaluation confirmed normal renal function, a hematocrit of 43%, and an International Normalized Ratio (INR) of 2.4. Initial troponin I was 0.02 ng/mL, subsequently increasing to 0.21 ng/mL. She was admitted to a telemetry unit and treated with unfractionated heparin in addition to aspirin, beta blockers, and nitrates; warfarin was held to allow the INR to return to baseline, at which point she underwent cardiac catheterization.

Cardiac catheterization

The diagnostic angiograms demonstrated occlusion of the native right coronary and left anterior descending coronary artery with occlusion of both saphenous vein grafts. A widely patent left internal mammary graft supplied a large left anterior descending artery. Severe disease of the proximal segment of a large first obtuse marginal artery as well as severe disease of a smaller-caliber second obtuse marginal artery likely accounted for her clinical presentation (Figures 18-1, 18-2 and Video 18-1). Based on these angiograms, stress test results, and her symptoms of progressive angina, her physician decided to revascularize the first obtuse marginal artery percutaneously.

FIGURE 18-1 This is a left anterior oblique projection with caudal angulation of the left coronary artery demonstrating a severe stenosis in the proximal segment of the first obtuse marginal artery (arrow). There is also occlusion of the left anterior descending artery.

FIGURE 18-2 This angiogram of the left coronary artery in a right anterior oblique projection with caudal angulation reveals two severe stenoses of the proximal segment of the first obtuse marginal artery. There is tethering of the vessel due to the previously placed saphenous vein graft (arrow). The left anterior descending coronary artery is occluded and there is also severe stenosis of a small-caliber second obtuse marginal artery.

After selective engagement of the left coronary ostium with a 6 French JCL 4.5 guide catheter, and following administration of an intravenous bolus followed by an infusion of bivalirudin, a floppy-tipped 0.014 inch guidewire was advanced to the lesion. The wire tip successfully crossed the two lesions but was unable to advance around the sharply angulated segment, due to tethering of the vessel from the previously placed saphenous vein graft (Figure 18-3). Despite prolonged attempts and the incorporation of various curves applied to the wire tip, followed by the use of a hydrophilic-tipped guidewire (Boston Scientific, PT2), the operator failed to successfully gain access to the distal part of the artery. Additional manipulations ultimately closed the artery (Figure 18-3 and Videos 18-2, 18-3) and the patient experienced chest discomfort but remained hemodynamically stable. Fortunately, removal of the guidewire and administration of intracoronary nitroglycerin led to restoration of vessel patency (Video 18-4); there also appeared to be small dissection flaps within the diseased segment caused by the attempts. The operator abandoned further attempts at percutaneous revascularization and the patient left the cardiac catheterization laboratory with no electrocardiographic changes and noting only minimal chest discomfort.

FIGURE 18-3 Attempts at crossing the lesion with a guidewire were unsuccessful, because of the presence of severe angulation due to the tethering of the vessel from the previously placed saphenous vein graft.

Postprocedural course

The patient was admitted to the coronary care unit for further observation. She remained free of chest pain. Serial troponin I assays demonstrated a further rise in troponin, peaking at 11.30 ng/mL the following morning. Since percutaneous attempts failed and the risk-benefit ratio of repeat coronary bypass surgery appeared prohibitive, she was treated medically with the addition of long-acting nitroglycerin and clopidogrel along with an increase in her beta-blocker dose. She remained symptom-free and was discharged 48 hours later. She remained free of limiting symptoms at a follow-up visit 6 months postprocedure.

Discussion

In the current era, the success rate of percutaneous coronary interventions exceeds 90%, a testimony to the remarkable advances in pharmacology, equipment, and techniques over the past several decades. Several terms are used to define success: 1) angiographic success, 2) procedural success, and 3) clinical success. Angiographic success indicates the presence of less than 20% residual stenosis at the treated lesion. Procedural success is defined as the presence of angiographic success along with the absence of a major complication (death, myocardial infarction, or need for emergency bypass surgery), and clinical success is present when there is procedural success plus improvement in symptoms. Current rates of angiographic and procedural success rates are very high, approaching 95% and 92% respectively.¹

Failure to cross a lesion with a guidewire is one of the most frequent causes of an unsuccessful intervention; it is usually due to the presence of a chronic occlusion, where success rates, even in the best hands, rarely exceed 70%. The present case illustrates the point that failure to cross may also occur in the setting of a patent vessel when there is great complexity to the lesion. In the case described here, difficulty crossing was due to severe angulation from tethering of the vessel from a previously placed saphenous vein graft. Although the operator was able to cross the severe stenosis, the guidewire would not advance around the sharply angulated segment. In such cases, guidewire passage may be difficult or impossible because the wire becomes bound by the stenosis and the operator loses the ability to change the direction of the tip. Additional reasons contributing to an operator’s failure to cross include the presence of marked lesion eccentricity, the presence of a side branch at the site of a severe stenosis, creation of a false lumen or achieving a subintimal position with the wire tip, and the presence of an unrecognized chronic occlusion.

In this case, the attempt to cross with a guidewire led to abrupt vessel closure and a periprocedural myocardial infarction; fortunately the artery reopened spontaneously, limiting the extent of myocardial damage. Guidewire-induced trauma is one cause of abrupt closure after a coronary intervention; additional mechanisms include elastic recoil, dissection, spasm, and thrombus. In the pre-stent era, abrupt vessel closure complicated 2% to 8% of coronary balloon angioplasties. The morbidity of these events was substantial; nearly one third of these required emergency bypass surgery, and there was a high rate of Q-wave myocardial infarction and death.² The advances in pharmacology preventing procedural thrombus and the routine use of coronary stents targeting recoil and dissection reduced the incidence of sustained abrupt vessel closure to less than 1% and the need for emergency bypass surgery to the current, nearly negligible levels.

Fortunately, this patient responded to medical therapy. Since failure to cross with a guidewire excludes percutaneous options, the only revascularization alternative is bypass surgery. In the event of a failed intervention, indications for emergent bypass surgery would include the presence of ongoing ischemic chest pain, hemodynamic instability, or the presence of a large vascular territory at risk from the closed or severely stenotic artery. In this case, based on the relatively small size of the vascular territory, and in the absence of chest pain or hemodynamic instability, her physicians did not feel that the potential benefits warranted the risk of a reoperation.