Case presentation

An active 60-year-old man with a history of tobacco abuse, prostate cancer, hypertension, and several prior myocardial infarctions in the remote past presented with chest pain. He underwent coronary bypass surgery 16 years earlier consisting of a left internal mammary graft to the left anterior descending artery (LAD). He was in his usual state of health until midnight prior to admission when he awoke with severe substernal chest pain radiating to both shoulders and accompanied by dyspnea and diaphoresis. Sublingual nitroglycerin tablets alleviated the pain temporarily, only for it to recur. He drove himself to the emergency department at 5:00 am, where he was noted to have ST-segment depressions in the anterolateral leads on his ECG; the first troponin was negative. He was admitted and treated with unfractionated heparin, aspirin, clopidogrel, nitroglycerin, and a beta blocker and became pain-free. He was referred for catheterization the next day.

Cardiac catheterization

The left internal mammary graft to the LAD was intact and the LAD supplied collaterals to the circumflex (Video 37-1). The native LAD and circumflex were both occluded. Heavy calcification affected the right coronary artery and severe disease was present in the midsegment of this artery (Figures 37-1, 37-2 and Videos 37-2, 37-3). Because of extensive calcification, rotational atherectomy was planned. This was performed with a 1.5 mm burr through an 8 French right Judkins guide catheter after a temporary pacemaker was placed and procedural anticoagulation was achieved with unfractionated heparin and eptifibatide. Following rotational atherectomy, balloon angioplasty using a compliant, 2.5 mm diameter by 20 mm long balloon was accomplished at several locations within the mid-right coronary, and full inflation of the balloon was noted at nominal inflation pressures (Figure 37-3). The angiogram obtained after rotational atherectomy and balloon angioplasty is shown in Figures 37-4 and 37-5 and Videos 37-4 and 37-5. While the left anterior oblique projections appeared acceptable, the right anterior oblique projection revealed a large dissection in the midsection.

FIGURE 37-1 This is the left anterior oblique projection of the right coronary angiogram showing a severe stenosis in the mid portion of the artery.

FIGURE 37-2 This is the right anterior oblique projection of the right coronary artery showing the severe stenosis of the midsegment of the right coronary artery and extensive calcification.

FIGURE 37-3 The balloon was fully expanded after performance of rotational atherectomy.

FIGURE 37-4 Angiographic appearance following rotational atherectomy and balloon angioplasty.

FIGURE 37-5 An extensive dissection is apparent in the right anterior oblique projection (arrow).

The operator then attempted to advance a stent (3.0 mm diameter by 20 mm long paclitaxel-eluting stent) to the mid-right coronary lesion with the goal of covering the entire dissection. However, the stent would not advance to the desired location. The operator decided to withdraw this stent and try a shorter, bare-metal stent; however, the first stent was firmly embedded in the lesion and would not withdraw to the guide. The operator feared that the stent might come off the balloon if additional force was applied and deployed the stent at the location, it became trapped (Figure 37-6). The angiogram obtained after this stent was deployed proximal to the desired location is shown in Figure 37-7. This stent was then aggressively postdilated with a noncompliant balloon and the unstented lesion in the midportion of the artery aggressively ballooned with a noncompliant balloon to high pressures after an additional and more supportive guidewire was placed as a “buddy” wire to facilitate another attempt at stent placement. The operator then chose a 3.0 mm diameter by 8 mm long bare-metal stent. With great difficulty, this stent was advanced distally, covering the distal part of the dissection (Figure 37-8 and Video 37-6); however, there remained a prominent dissection proximal to this in the midsegment of the artery. Again, the operator aggressively ballooned this area with noncompliant balloons. While the angiographic result appeared acceptable in the left anterior oblique projection (Video 37-7), the prominent dissection was most apparent in the right anterior oblique projection and narrowed the lumen significantly (Figure 37-9 and Video 37-8). One additional 3.0 mm diameter by 8 mm long bare-metal stent was advanced through the proximal stent and covered an additional portion of the dissection, but the operator could not pass this third stent far enough to cover the dissection completely. Despite aggressive ballooning, additional attempts to completely cover the dissection by inserting yet another stent failed. The operator decided to stop the procedure after watching the patient for 15 minutes on the catheterization table and after observing no deterioration in the angiogram or the patient’s clinical status, or any change in the electrocardiogram. The final angiographic results are shown in Figures 37-10 through 37-12 and Videos 37-9 and 37-10.

FIGURE 37-6 This figure shows the location of the first stent deployment. This stent could not be advanced beyond the curve in the midportion of the artery and could not be withdrawn into the guide catheter, so it was deployed at this location.

FIGURE 37-7 Angiographic appearance after first stent deployment.

FIGURE 37-8 Uncovered dissection in the mid-right coronary artery, LAO view (arrow).

FIGURE 37-9 Uncovered dissection in the mid-right coronary artery, RAO view (arrow).

FIGURE 37-10 Final angiographic appearance, LAO view.

FIGURE 37-11 Final angiographic appearance, RAO view. Residual dissection is shown (arrow).

FIGURE 37-12 Final angiographic appearance, lateral view. Residual dissection is shown (arrow).

Postprocedural course

He remained free of chest pain overnight and was discharged the next afternoon after ambulating without symptoms on clopidogrel, aspirin, atenolol, amlodipine, simvastatin, and lisinopril. He remained free of symptoms at follow-up 1 month later but was subsequently lost to follow-up.

Discussion

Coronary dissections are a common complication of percutaneous coronary intervention and, if untreated, can lead to serious sequelae including abrupt vessel closure, periprocedural myocardial infarction, closure of major side branches, emergency bypass surgery, and even death. Coronary stents successfully treat most dissections such that, in the current era, the risk of sustained vessel closure or the need for emergency bypass surgery due to a coronary dissection is very rare. However, as demonstrated by this case, the modern-day interventionalist is sometimes faced with the predicament of a coronary dissection that cannot be stented. The current generation stents are highly deliverable but occasionally, due to the presence of excessive tortuosity, heavy calcification, the presence of prior stents, or inadequate guide catheter backup, a stent may not be deliverable. In such cases, the only options available are either to leave the dissection alone and treat medically or to perform emergency bypass surgery.

The decision to leave a dissection alone depends upon the anticipated risk of vessel closure or other adverse event. The angiographic appearance of coronary dissections can be classified according to the system described by the National Heart, Lung, and Blood Institutes (Table 37-1). Using this classification scheme, the outcomes of 691 coronary dissections from the balloon era (1987-1990) were determined.¹ Type A dissections are of no clinical consequence and were not studied. The incidence of adverse events such as emergency bypass surgery and abrupt vessel closure were very low for Type B dissections. However, Type C through F dissections had a substantially higher incidence of adverse events. The risk of abrupt vessel closure and emergency bypass surgery was nearly 10% for Type C dissections and was between 30% and 60% for the more serious Type D, E, and F dissections.¹ Overall procedural success in this series was 93.7% for Type B dissections (similar to patients without angiographically evident dissections), and was only 38% for patients with Type C through F dissections. Although this information is derived from the balloon angioplasty era and may have little relevance in predicting outcomes in the current era with its advances in pharmacology, this information assists the operator in predicting the risk of vessel closure in cases of a dissection that cannot be stented.

TABLE 37-1 NHLBI Classification of Coronary Dissection

In this case, the angulation and excess calcium led to the dissection. The operator was surprised by the difficulty in passing the stent since a balloon easily passed and fully expanded. Deploying the stent proximal to the lesion only made it more difficult to subsequently pass a stent to the dissected area; however, the operator had no choice, as the stent became firmly lodged in the lesion and there was a risk of stent embolization if excessive force was used to withdraw the stent back into the guide.

Medical therapy for a large dissection is limited, but most advocate the use of a platelet glycoprotein IIb/IIIa inhibitor as an adjunct to prevent thrombotic occlusion. An intraaortic balloon pump may be helpful in the presence of ongoing ischemic symptoms or if the patient is referred for emergency bypass surgery. In many cases, abrupt vessel closure as a consequence of a serious dissection develops in the catheterization laboratory within a few minutes to hours of the procedure. Thus, many clinicians wisely keep the patient on the catheterization laboratory table when they are managing a dissection that cannot be stented and reimage the artery at intervals to assess for deterioration in the lumen or in blood flow. Also, maintaining the arterial access sheath in place for a few hours is good practice to facilitate a prompt return to the catheterization laboratory if necessary. Coronary bypass surgery is indicated when the artery supplies a significant vascular territory and there is abrupt closure that cannot be reopened or there is a dissection with luminal compromise and ongoing symptoms, electrocardiographic changes, or hemodynamic instability.

The dissection noted in this case would be classified as a Type E dissection with a high likelihood of closure if left untreated. Despite the presence of an unstented dissection, the patient actually did very well, but this is likely because stents were successfully delivered on either side of the dissection and because glycoprotein IIb/IIIa inhibitors were used, both of which might have altered the natural history of this type of dissection. Although the patient had a favorable acute outcome, the presence of an unstented dissection adjacent to successfully deployed coronary stents is a risk factor for stent thrombosis.^2,3 Whether this concern justifies a more aggressive approach and is an indication for surgery is unclear.