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1. Which of the following statements about chronic total coronary occlusion are true: a. Patients often present with a
change in exertional angina due to collateral insufficiency Make your selection before scrolling beyond this point Answer: With total coronary occlusion, the underlying pathological process is the principal determinant of clinical presentation, presence of collaterals, myocardial viability, and the nature of the coronary obstruction. Acute occlusion is usually caused by ruptured plaque overlying soft atheroma and presents as acute MI. Spontaneous recanalization occassionally occurs; intracoronary collaterals are rare and intercoronary collaterals are less common than with chronic occlusion; and myocardial viability is uncommon unless collaterals are present. PTCA success exceeds 95%. In contrast, chronic occlusion is caused by complex, fibrocalcific atherosclerosis with layered, chronic, organized thrombus. Spontaneous recanalization is rare; intracoronary (bridging) collaterals are occassionally present and intercoronary collaterals are common; and myocardial viability is common, as collaterals sustain viability. PTCA success is variable, depending on the duration and morphology of the occlusion. (Answer: a) 2. When PTCA is used to treat chronic total occlusions, the most common cause of procedural failure is: a. Failure to cross the occlusion
with a balloon Make your selection before scrolling beyond this point Answer: Compared to PTCA of nontotal occlusions, revascularization rates for chronic total occlusions are disappointingly low. Reported series comprising more than 4400 total coronary occlusions indicate an overall success rate of 69% (range 47-81%). The most common reasons for procedural failure include the inability to cross the occlusion with a guidewire (80%), failure to cross the occlusion with a balloon (15%), and the inability to dilate the stenosis (5%). (Answer: b) 3. Factors favoring success for PTCA of chronic total occlusions include: a. Functional occlusion Make your selection before scrolling beyond this point Answer: PTCA success rates for chronic total occlusion are highly variable, depending on the duration and morphology of the occlusion. Predictors of PTCA success include functional occlusion, occlusion age < 12 weeks, length < 15 mm, tapered stump, no sidebranch at point of occlusion, and no intracoronary bridging collaterals. Predictors of procedural failure include total occlusion, occlusion age > 12 weeks, length > 15 mm, abrupt cut-off, sidebranch present, extensive bridging collaterals ("caput med"). (Answer: e) 4. Percutaneous revascularization is contraindicated when the chronic total occlusion is 6 months old or shows extensive bridging collaterals ("caput med"): a. True Make your selection before scrolling beyond this point Answer: The duration of occlusion may be estimated by time interval between a major ischemic event (Q-wave myocardial infarction, new onset angina, or abrupt worsening in anginal status) and PTCA. Successful revascularization is highest for occlusions < 1 week, intermediate for occlusions 2-12 weeks, and lowest for those > 3 months. Occlusion duration alone should not preclude revascularization since procedural success for occlusions > 6 months old may be as high as 50-75%. Small angioplasty series suggested that bridging collaterals was the most important determinant of successful PTCA of chronic total occlusions. However, in a recent large study, Kinoshita et al reported equally high success rates among 109 total occlusions with bridging collaterals and 324 occlusions without bridging collaterals (75% vs. 83%, p = 0.07). The authors attributed the high success rate to operator experience and aggressive use of stiff wires. (Answer: b) 5. The risk of major complications is similar for PTCA of total and nontotal occlusions: a. True Make your selection before scrolling beyond this point Answer: Although PTCA of a chronic total occlusion is generally considered a "low-risk" procedure, it is not risk-free. Several reports have found that major complications occur with equal frequency among total and nontotal occlusions, and the presence of a chronic total occlusion is an independent predictor of acute closure. Major complications include acute closure (5-10%), MI (0-2%), emergency CABG (0-3%), and death (0-1%). (Answer: a ) 6. Which of the following statements about late outcome after PTCA of chronic total occlusions are true: a. More than 60% of patients with
successful PTCA are asymptomatic at follow-up Make your selection before scrolling beyond this point Answer: The majority of patients with successful PTCA are asymptomatic at follow_up. In the three largest reports, 76%, 69%, and 66% of patients were asymptomatic 1 year 2 years, and 4 years after PTCA. Absence of symptoms does not exclude restenosis since 40% of patients with restenosis may be free of chest pain. Although data are limited, successful PTCA may improve ventricular relaxation and regional wall motion. Global ejection fraction improved in one study, but not in another. Among patients with successfully recanalized occlusions, those with persistent patency and normal flow had better global function and less ventricular dilatation than patients with occluded vessels. Most studies indicate that successful recanalization of a chronic total occlusion reduces the need for CABG by 50-75%. However, PTCA does not appear to improve survival or reduce the incidence of late MI. (Answer: e) 7. Potentially useful
devices for chronic total occlusions which cannot be crossed with a flexible guidewire
include: Make your selection before scrolling beyond this point Answer: Some incremental benefit can be achieved using these devices when a chronic total occlusion cannot be crossed with a conventional PTCA guidewire. Rotablator atherectomy can be used to treat undilatable stenosis but requires initial guidewire crossing. (Answer: d) 8. Prolonged intracoronary thrombolytic infusions have not been shown to improve the recanalization rate of chronic total coronary occlusions: a. True Make your selection before scrolling beyond this point Answer: Data from small reports (using different lytic agents and infusion regimens) suggest that prolonged intracoronary thrombolytic infusions may improve the recanalization rate of chronic total coronary occlusions. Among 56 resistant occlusions (combined data from 3 studies), a post-lytic improvement in coronary flow and PTCA success was achieved in 63% and 73% of cases, respectively. These finding were corroborated by Zidar et al. in a small randomized trial. (Answer: b) 9. Which of the following statement about stents vs. PTCA for chronic total occlusions are true: a. Stents are associated with higher
procedural success but similar restenosis rates Make your selection before scrolling beyond this point Answer: Although the presence of a chronic total occlusion was once a relative contraindication to stenting, recent data indicate a definite role. Most randomized trials have demonstrated less restenosis, less reocclusion, and less target lesion revascularization with stents, although some did not. Risk factors for restenosis are similar to those for stenting nontotal occlusions and include final MLD, length of stent, final balloon/artery ratio, and dissection.Older stent trials frequently used original warfarin-based strategies, which may have had an adverse impact on late outcome; more contemporary antiplatelet strategies have enhanced the safety and efficacy of stenting. (Answer: d) 10. Correct statement about chronic total occlusions of saphenous vein grafts: a. Following bypass surgery, 10-15%
of SVGs will be occluded at one year and 50% by 10 years Make your selection before scrolling beyond this point Answer: Of the more than 600,000 saphenous vein bypass grafts placed each year, 10-15% will be occluded at one year and 50% by 10 years after operation. Among the 10_20% of patients who require reoperation within 10 years, repeat bypass surgery is technically more difficult and has been associated with increased morbidity and mortality compared to the initial operation. The etiology of saphenous vein graft occlusion is dependent on the time interval following bypass surgery. In the first month, graft occlusion is almost always due to graft thrombosis from poor surgical technique (suture line stenosis, intraoperative vein trauma) or poor distal run_off. Between 1-12 months, initial hyperplasia is the most common cause. After 1 year, occlusion is caused by graft atherosclerosis, which is indistinguishable from coronary arteriosclerosis. Once graft occlusion occurs, retrograde thrombosis to the aorto_ostial junction is common. Although PTCA can successfully revascularize approximately 70% of occluded vein grafts, there is a high incidence of distal embolization (11%), late graft occlusion (40-50%), and late cardiac events (event-free survival of 54% at 1 year and 34% at 3 years). When distal embolization occurs, 50% are associated with vessel closure or CK elevation. Embolization may present as abrupt cutoff of distal vessels (amenable to repeat dilation or lytics), or may be inferred on the basis of no-reflow. PTCA alone is rarely utilized as sole therapy for occluded vein grafts. (Answer: a)
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