Immediate stent implantation versus conventional techniques for the treatment of abrupt vessel closure or symptomatic dissections after coronary balloon angioplasty☆

Article Outline

• Abstract
• Methods
  • Patients
  • Catheterization procedure including randomization
  • End points
  • Quantitative coronary angiography
  • Statistical analysis
• Results
  • Primary end point
  • Secondary end points
  • Angiographic results
• Discussion
  • Limitations
  • Conclusion
• Appendix
  • Coronary angiographic core laboratory
  • Data coordinating center
  • Monitoring
  • Steering committee
  • The Stent-By study investigators
• References
• Copyright

Abstract 

Background Coronary stenting was initially designed to treat a bailout scenario. Prospective randomized trials comparing stent implantation with standard techniques, including emergency coronary artery bypass grafting, are lacking. The aim of this trial was to test the superiority of immediate stent implantation compared with standard techniques for the treatment of abrupt or threatening closure after coronary balloon angioplasty. Methods In a prospective trial, 100 patients with abrupt vessel closure or symptomatic dissections causing objective signs of ischemia were randomly assigned to treatment with immediate placement of stents (n = 51) versus standard techniques such as prolonged dilatation or emergency bypass surgery (n = 49). The primary end point was the achievement of successful stabilization not requiring crossover to the other study group. Secondary end points included event-free survival and restenosis. Results Successful stabilization was achieved in 94% of patients in the stent group compared with 78% of patients in the standard treatment group (P = .038). Two patients died in each group, and there was a trend toward a higher incidence of myocardial infarction (16% vs 8%; P = .163) and a significantly increased creatine phosphokinase level (245 IU/L [95% confidence interval, 217-265 IU/L] vs 179 IU/L [confidence interval 140-212 IU/L]; P = .0002) in the standard treatment group. Event-free survival after 250 days was 72% in the stent group compared with 29% in the standard treatment group (P = .001). The angiographic restenosis rate was 30% in the stent group versus 59% in the standard treatment group (P = .01). Conclusions Immediate stenting, if technically feasible, shows superior short- and long-term results compared with standard treatment options. (Am Heart J 2000;140:e26.)

Despite substantial technical, procedural, and device-related improvement, percutaneous transluminal coronary angioplasty (PTCA) is limited by the occurrence of abrupt or threatened vessel closure from symptomatic dissections, a result of the unpredictable plastic deformation of the obstructive plaque in association with acute thrombus formation.¹, ², ³ The incidence is reported to vary between 0.5% and 10.5%, and the time frame peaks within the first minutes after the PTCA procedure and is rarely found later than 24 hours after the procedure.¹ As a result, mortality rates are higher in these patients, and survivors frequently have myocardial infarction (MI) develop.², ³

Treatment options include catheter-based approaches with redilatation with prolonged inflations by standard or autoperfusion balloon catheters of slightly larger sizes or higher pressures⁴, ⁵, ⁶ or the application of directional atherectomy.⁷ If these techniques fail to restore adequate flow, emergency coronary artery bypass grafting (CABG) must be considered.⁸, ⁹, ¹⁰

Coronary stents were designed to achieve vessel patency and to restore adequate flow in the case of abrupt vessel closure or symptomatic dissections after PTCA.¹¹ The underlying mechanism is a scaffolding of the obstructive dissections against the vessel wall together with the ability to limit elastic recoil. Although several reports documented the feasibility of stenting in the scenario of abrupt vessel closure or symptomatic dissections,¹², ¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁷, ¹⁸, ¹⁹, ²⁰ no prospective randomized data are available comparing the outcome of stent implantation to standard techniques, including emergency CABG.

To test the hypothesis that immediate stenting is superior to standard techniques or emergency CABG with respect to successful stabilization, we performed this prospective randomized trial in a subset of patients with failed PTCA.

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Methods 

Patients 

The study group consisted of 100 patients with abrupt vessel closure (Thrombolysis In Myocardial Infarction [TIMI] flow 0) or symptomatic threatened closure (TIMI flow 1), with objective signs of ischemia in the electrocardiogram for at least 10 minutes because of significant dissections type C to E after PTCA, in whom emergency coronary artery CABG would be assumed as an alternative treatment. Patients with unprotected left main stenosis; ostial lesions of the right coronary artery, the left anterior descending, and the circumflex arteries; Q-wave MI within 7 days before the intervention; contraindication to oral anticoagulation; or of child-bearing age were excluded from this study because of safety issues. Patients’ baseline characteristics are summarized in Table I.

Table I. Baseline clinical, procedural, and angiographic characteristics

Results are mean ± SD or n (%).

LAD, Left anterior descending artery; LCx, left circumflex artery; RCA, right coronary artery.

The study was carried out according to the principles of the Declaration of Helsinki. Oral or written informed consent was received from all patients according to local practice before the intervention. The study was approved by the independent ethical committee in Freiburg, Germany.

Catheterization procedure including randomization 

All patients underwent cardiac catheterization, including PTCA by the femoral approach according to standard techniques applied in the different centers. Antithrombotic premedication consisted of aspirin 100 mg/d, and 10,000 to 15,000 IU heparin was given as a bolus plus infusion of 800 IU to 1000 IU/h during the procedure. Activated clotting time was checked according to local practice. If a patient fulfilled the inclusion criteria and did not have exclusion criteria, randomization was performed by central phone call-in. In the randomization group of immediate stent placement, operators were advised to fix the bailout situation by implantation of one or more Palmaz-Schatz stents (PS 153 either as a bare stent or premounted on a stent delivery system; Johnson & Johnson, Warren, NJ) without losing time to other preceding maneuvers. Implantation pressure was up to 10 atm, and operators were advised to perform stent dilatation with a balloon/vessel ratio of 1.1:1.2 at pressures >10 atm. If the balloon catheter with the mounted stent could not reach the target vessel site, other interventions had to be considered to improve access such as predilatation with larger balloons or atheroablative techniques. After the procedure, intravenous heparin drip was continued to keep the activated partial thromboplastin time at 50 seconds to 70 seconds until overlapping oral anticoagulation with coumadin was fully achieved at an international normalized ratio of 2.0 to 3.5, which was then prescribed for 3 months. Ticlopidine or clopidogrel was not administered. Patients with stent implantation were kept in the hospital until stable oral anticoagulation was maintained. Aspirin (100 mg/d) was continued.

In patients randomly assigned to standard treatment strategies, the operators were strongly advised to manage the bailout situation by performing longer inflations with standard or autoperfusion balloon catheters or by directional atherectomy. These attempts had to be documented in detail, and operators were strongly recommended not to use stents to complete the procedure to improve the angiographic appearance of the treated site. After the procedure, patients received intravenous heparin according to the suggestion of the operator. Aspirin (100 mg/d) was continued indefinitely.

Crossover from one randomization group to the other was only allowed after failure of the index treatment despite several documented attempts and if the operator believed that crossover would prevent emergency CABG. In any case, the indication for emergency CABG as the final treatment option was left to the operator’s decision in both study groups. Patients were monitored clinically and angiographically for 250 days.

End points 

The primary end point of this study was the achievement of stabilization with relief or significant improvement of angina and relief of ischemic electrocardiographic changes in the index leads without request for crossover or emergency CABG.

Secondary end points included the incidence of death, Q-wave and non-Q-wave MI, thrombotic events (including acute and subacute stent thrombosis, hemorrhagic complications, and the rate of angiographically defined restenosis), and target lesion resvascularization after hospitalization and after 250 days in both study groups. Q-wave MI was defined as the development of a new Q-wave with an increase in creatine phosphokinase (CPK) levels to more than 3 times the normal value and with an increase in the MB fraction to >6% of the total CPK levels. Non-Q-wave infarction was only based on cardiac enzymes, as described. Pathologic CPK levels after the intervention were controlled every 8 hours until normal values were documented again. Target vessel revascularization was defined as any intervention of the restenotic target lesion (>50% diameter stenosis) or CABG of the target vessel because of recurrent angina pectoris or signs of ischemia. Vessel occlusion or subtotal occlusion with visualization of filling defects after stenting within 24 hours together with angina and ischemic electrocardiographic changes were regarded as acute, and later than 24 hours up to 8 weeks as subacute stent thrombosis. Other events were recorded, including hemorrhagic complications (drop of hemoglobin of >3.0 mg/dL) such as bleeding in the groin with or without blood transfusion and gastrointestinal, retroperitoneal, or cerebrovascular bleeding.

Quantitative coronary angiography 

Coronary angiograms for quantitative analysis were performed before and after treatment and at 6 months. Additional angiograms were performed during emergency recatheterizations because of suspected thrombotic vessel closure. All coronary angiograms were analyzed in the core laboratory at the University of Essen, Germany. Quantitative coronary angiography was performed with the edge-detection system developed by Reiber et al (CMS, Medis, Leiden, The Netherlands).²¹ The mean variation for this system in determining the absolute diameter is ≤0.13 mm. For calibration, the non-contrast-filled guiding catheter was used. The vessel diameters proximal and distal to the lesion were used to determine the interpolated reference diameter. From 2 orthogonal views the minimal lumen diameter, the interpolated reference diameter, and the percent diameter stenosis were calculated as a mean according to previous reports. In addition, acute gain, late lumen loss, net gain, and the late lumen loss index were calculated.

Statistical analysis 

Intention-to-treat analysis was applied. Single comparisons were performed with respect to primary and secondary end points, and clinical events were ranked according to severity. The χ² test or Fisher exact test was applied when appropriate. Univariate relative risk for clinical end points was calculated by odds ratio and 95% confidence intervals (CI). Continuous variables were expressed either as mean ± SD or median and CI and compared by the unpaired 2-tailed Student t test, Mann-Whitney test, or Wilcoxon test when appropriate. The composite clinical end points of death, MI, and target vessel revascularization were analyzed by Kaplan-Meier survival curves, with differences between the 2 treatment groups compared by log-rank test. Two-sided P values are reported.

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Results 

From April 1991 to February 1996, 12,390 coronary interventions were performed at the 7 German centers, with a bailout situation in 223 patients (1.8%) according to study definitions, of whom 100 could be enrolled in the study and were randomly assigned to immediate stenting (51 patients) or standard treatment options (49 patients). The remaining 123 patients were either sent for immediate emergency CABG (53 patients) or directly received stents (70 patients) because of life-threatening cardiogenic shock, a situation that did not allow randomization according to the operator’s judgement. In-hospital mortality rate was 11% in these patients, and 36 (33%) of 110 survivors had MI develop.

Primary end point 

In the standard treatment group, autoperfusion balloons were used in 46 (94%) of 49 patients, and directional atherectomy was used in the remaining 3 patients (6%). Successful stabilization was achieved in 38 (78%) of 49 patients in the standard treatment group compared with 48 (94%) of 51 patients in the stent group (relative risk 0.26; 95% CI, 0.08–0.88; P = .038). Despite multiple dilatations with autoperfusion balloons for a total of 792 ± 475 seconds, in the standard treatment group 9 (18%) of 49 patients required crossover to stenting because of persistent flow-limiting dissections, with subsequent successful stabilization in all these patients. Two (4%) of 49 patients were sent for emergency bypass operation because of cardiogenic shock. In the stent group, 3 (6%) of 51 patients required crossover to standard techniques with prolonged balloon inflations with autoperfusion balloons with no need for emergency CABG because the target lesion could not be accessed by the stent (P = .121).

Secondary end points 

In the standard treatment group, 1 (2%) of 49 patients died 3 days after emergency CABG because of cardiogenic shock with unsuccessful resuscitation. In the stent group, 1 of 51 patients died 5 days after successful stabilization after stenting because of subacute stent thrombosis with development of cardiogenic shock requiring mechanical resuscitation with fatal outcome (Table II).

Table II. Cumulative clinical events during hospital course and at 6 months

Results are mean ± SD or n (%).

During follow-up 1 additional patient died in each group from noncardiac events. In the standard treatment group 8 (16%) of 49 patients developed Q-wave MI and an additional 4 patients (8%) non-Q-wave MIs, whereas in the stent group 4 (8%) of 51 patients had Q-wave MIs develop and 2 others (4%) non-Q-wave MIs (P = .357 and P = .637, respectively). MI was related to subacute stent thrombosis in 2 of the crossover patients in the standard treatment group and in 3 patients of the stent group. These patients were treated by emergency recatheterization and PTCA of the occluded vessel. Maximum CPK (median, 245 IU/L; 95% CI, 217-265 IU/L vs median, 179 IU/L; 95% CI, 140-212 IU/L; P = .0002) and CPK-MB rises (median, 27 IU/L; 95% CI, 24-30 IU/L vs median, 20 IU/L; 95% CI, 18-24 IU/L; P = .0004) were significantly higher in the standard treatment group compared with the stent group (Figure 1, top ), which persisted even after exclusion of patients who had Q-wave or non-Q-wave MI develop but had a CPK rise of <3 times the normal value (Figure 1, bottom ).

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• Fig. 1. 

  Maximum values for CPK (left panels) and CPK-MB (right panels) after immediate stent placement or application of standard treatment options in patients with abrupt or threatened closure during PTCA. Bottom panels represent results for subgroup of patients who did not have Q-wave or non-Q-wave MI develop but had a CPK rise of <3 times the normal value. Results are given as individual data and summarized as notched box-and-whisker plots, where notch represents median, box represents upper and lower 95% confidence limits, and error bars represent expected range. Solid circles in upper panels represent results of patients who had Q-wave MI develop.

Hemorrhagic complications occurred in 4 patients (8%) in both study groups, respectively, of whom all 4 of 49 patients in the standard treatment group were crossover patients with stent placement. No patient died from bleeding complications or developed cerebral bleeding.

The duration of hospitalization was significantly longer in the stent group (6.6 ± 2.8 days vs 4.9 ± 2.5 days; P = .002).

At follow-up after 5.9 ± 1.7 months, ischemia-driven target lesion revascularization was performed in 28 (57%) of 49 patients in the standard treatment group compared with 10 (20%) of 51 patients in the stent group (relative risk, 0.34; 95% CI, 0.19–0.63; P = .001). Restenotic lesions were treated by stent placement and stent restenosis was treated by PTCA, except in 2 patients who were sent for CABG because of additional progression of coronary atherosclerosis. Overall event-free survival, defined as survival without any MI or target lesion resvascularization, was significantly better (log-rank χ², 16.05; P = .001) in the stent group compared with the standard treatment group (Figure 2).

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• Fig. 2. 

  Event-free survival (absence of death, MI, CABG, and revascularization of target vessel) within 250 days after immediate stent placement or application of standard treatment options in patients with abrupt or threatened closure during PTCA. Log rank test P = .001.

Furthermore, patients in the stent group were less symptomatic with respect to their angina class at follow-up (Table III).

Table III. Functional angina status at 6-month follow-up

Results are n (%). P = .0005.

CCS, Canadian Cardiovascular Society class.

Angiographic results 

Table IV summarizes the results of quantitative coronary angiography.

Table IV. Coronary angiographic data

Values are mean ± SD or n (%).

Postprocedural minimal lumen diameter was significantly larger and percent residual diameter stenosis smaller in the stent group. Follow-up angiography was performed in 44 of the 49 and 51 patients (88% and 87%, respectively). Based on intention to treat, restenosis was documented in 26 (59%) of 44 patients in the standard treatment group compared with 13 (30%) of 44 patients in the stent group (relative risk, 0.50; 95% CI, 0.30–0.84; P = .01). Acute gain, late loss, the loss index, and net gain were found to be significantly different in the stent group compared with the standard treatment group.

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Discussion 

The results of this prospective, randomized, multicenter trial document that immediate stent placement is superior to standard treatment options, including prolonged dilatation or the option of emergency CABG in the treatment of peri-interventional abrupt or threatened coronary vessel closure during PTCA with respect to acute stabilization and long-term outcome.

The incidence of this bailout situation is reported to occur in 0.5% to 6.4% of PTCA cases, which can increase to 10.5% in patients with acute coronary syndromes.¹, ², ³ The incidence occurs during the procedure in 80% and within the next 24 hours in the remaining 20%.¹ The underlying mechanisms are multifactorial and include mechanical obstruction as a result of intimal and medial flaps, elastic recoil after balloon deflation, platelet adhesion and aggregation with subsequent thrombus formation, subintimal hemorrhage, and vasoconstriction.¹ Thus treatment options must address the mechanical and thrombotic aspects.

The patients for this study were selected very carefully. They had objective signs of severe ischemia related to the treated target vessel segment before undergoing randomization. Therefore this study differs from numerous other studies that showed positive effects of stent placement for the treatment of postinterventional dissections with threatened closure or very infrequently complete vessel closure after PTCA.¹³, ¹⁷, ¹⁸

The rate of successful stabilization after immediate stent placement of 94% in the catheterization laboratory is quite favorable and corresponds to other reports of bailout stent implantation.¹², ¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁷, ¹⁸, ²² It is superior to the rate of 78% in patients treated with techniques such as prolonged inflations with autoperfusion catheters. Prolonged dilatation with autoperfusion balloon catheters for several minutes was assumed as the first-choice standard treatment option in the case of abrupt or threatened closure during PTCA in the early 1990s. Ricci et al²³ reported for the Trial of Angioplasty and Stents in Canada (TASC) II trial a rate of successful stabilization in the stent group of 91% compared with only 46% in the other group.²³ This only other prospective randomized trial of bailout stenting compared with standard treatment options was unfortunately terminated prematurely because of excessive crossover to stenting. De Muinck et al²⁴ performed a similar but retrospective and nonrandomized trial that documented a better restoration of normal flow in 94% of patients in the stent group compared with 70% in the other group. Similar results were documented by Barberis et al²⁵ in retrospective analysis with a rate of 95% versus 72% and by Lincoff et al¹⁵ in a matched case-control study with 97% versus 72%.

Emergency coronary artery CABG is indicated for refractory abrupt or threatened closure with ongoing objective signs of ischemia in the majority of patients. The incidence in the prestent era dropped from 63% from 1980 to 1984 to 32% from 1989 to 1992.¹, ³, ²⁶ Nevertheless, this rescue treatment is associated with a 5% to 10% incidence of death and an approximate 40% incidence of perioperative MI.¹, ⁸ The rate of emergency bypass operation was low in our study, with only 2 patients in the standard treatment group, 1 of whom died. This reflects the general attitude of the study group: emergency bypass operation should be avoided when possible because of the high incidence of associated complications. Furthermore, crossover to stenting was another permitted treatment option.

Adjunct antithrombotic treatment additional to antiaggregation with aspirin and anticoagulation with high-dose heparin (>100 IU per kg body weight) was only administered in 1 patient in the standard treatment group, who received intracoronary thrombolysis with urokinase. Today, more potent antiaggregation by glycoprotein IIb/IIIb blockers is recommended as an adjunct therapy after failed PTCA, especially when filling defects suggest thrombus formation.²⁷

Although there was no statistically significant difference, there were more postinterventional Q-wave and non-Q-wave MIs in the standard treatment group of our study. In addition, the maximum CPK and CPK-MB rises were significantly higher in these patients compared with the stent group. This is mainly from the faster and more effective restoration of antegrade flow to the target perfusion bed by stenting. Because postinterventional CPK rise is a predictor of major adverse events, stenting of abrupt or threatened closure should provide a beneficial long-term outcome.²⁸

Subacute stent thrombosis occurred in 3 patients in the stent group (6%) and in 2 crossover patients (4%) in the standard treatment group, with a total incidence of subacute stent thrombosis of 10% despite aggressive anticoagulation with heparin and overlapping oral anticoagulation with coumadin in addition to aspirin. The incidence of subacute stent thrombosis after bailout stenting ranges between 3% and 32% in the literature.²⁹, ³⁰ In the TASC II trial, the incidence of subacute stent thrombosis was 11%.²³ Currently, the incidence of subacute stent thrombosis has dropped significantly even after bailout stenting because of adjunct antiaggregation therapy with perioperative administration of glycoprotein IIb/IIIa blockers³¹ and oral therapy with ticlopidine and aspirin.³², ³³

Because of the aggressive anticoagulation procedures in our study, hemorrhagic complications were found more frequently in the stent group, which would now be affected by more contemporary antithrombotic approaches. Hospitalization in the stent group was significantly longer, especially because overlapping oral anticoagulation for safety reasons was performed during hospitalization until an international normalized ratio of 2.0 to 3.5 was achieved. This requirement nowadays can be neglected with contemporary antithrombotic therapy excluding coumadin. Furthermore, stenting of the dissected coronary artery maintains a larger and more restored lumen, which allows compensation for neointimal growth. As a result, long-term restenosis is significantly reduced to 26% compared with 52% in the standard treatment group. Very similar results were documented in the TASC II trial with 22% versus 50%.²³ Clinically, patients after bailout stent placement were found less symptomatic and required target lesion revascularization less frequently at 6 months.

Limitations 

Patients with a potentially life-threatening acute disease are difficult to enroll into a prospective randomized trial by telephone allocation. Therefore 123 patients were lost to the study because the operators decided either to perform immediate stent implantation or sent the patient for emergency bypass operation because of cardiogenic shock. Furthermore, management of these high-risk patients by the individual operators is different and therefore responsible for the varying enrollment at the different centers. Nevertheless, the patients of both study groups are quite comparable.

Antithrombotic therapy in patients with stent implantation has changed throughout the study period to a more potent antiaggregation with aspirin and ticlopidine or clopidogrel and away from coumadin, with documented lower incidences of subacute stent thrombosis. Therefore the adverse study results on subacute stent thrombosis and bleeding complications today can be expected in lower incidences. Furthermore, the time to maintain stable oral anticoagulation with coumadin after stenting was the main contributor for prolonged hospitalization after stenting. Currently this is no longer necessary because coumadin is substituted by ticlopidine or clopidogrel. Nevertheless, it cannot be expected that a routine administration of ticlopidine or clopidogrel would have an impact on the primary end point, namely successful stabilization, in one of the study arms.

In the stent group of our study, the 15-mm Palmaz-Schatz stent was implanted. For this stent, mostly beneficial study results are reported.³⁴, ³⁵, ³⁶, ³⁷ Currently, at least in Europe, more than 50 different bare or premounted stents are available for coronary implantation, with different stent lengths up to 40 mm. These newer stents are more appropriate to cover the individual length of an occluded or dissected vessel segment by a single stent compared with multiple stenting, which is a predictor of stent restenosis.

From an ethical point of view, crossover of patients from the standard treatment group to stenting must be allowed before considering emergency bypass operation. Statistically, this can alter the outcome of the study. Therefore very strict recommendations were defined for crossover and checked by the core laboratory data monitoring and evaluation team. In the TASC II trial,²³ there was a much higher rate of crossover to stenting in the standard treatment group (50% vs 18% in our study), leading to premature termination of this study.

Conclusion 

Our study supports the superiority of immediate stent placement for the treatment of abrupt or threatened closure during PTCA and as the first-choice treatment if technically feasible. Because many of the initial drawbacks of coronary stents, namely stent thrombosis and bleeding complications because of aggressive anticoagulation, have been overcome³², ³³ and stents proved beneficial long-term outcome regarding a reduction of restenosis in different patient populations,³⁴, ³⁵, ³⁶, ³⁷ provisional stenting, even before abrupt vessel closure occurs, has gained broad acceptance. Therefore suboptimal postangioplasty results should be stented.

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Appendix 

Coronary angiographic core laboratory 

Michael Haude, MD, Martin Michel, MD, Fedai Özcan, MD, Cardiology Department, University Essen

Data coordinating center 

Michael Haude, MD, Martin Michel, MD, Fedai Özcan, MD, Cardiology Department, University Essen

Monitoring 

Anita Piwinski, Hamburg

Steering committee 

Raimund Erbel, MD, Michael Haude, MD, Hans Wilhelm Höpp, MD, Bernd Heublein, MD

The Stent-By study investigators 

H.W. Höpp, MD, D. Franzen, MD, Department of Medicine III, University of Cologne; R. Erbel, MD, M. Haude, MD, Cardiology Department, University GHS-Essen; H.-J. Rupprecht, MD, Second Medical Clinic, Johannes Gutenberg University Mainz; M. Sigmund, MD, J. vom Dahl, MD, P. Hanrath, MD, Department of Internal Medicine, Medical Clinic 1, RWTH Aachen; B. Heublein, MD, Department of Cardio-Thoracic Surgery, Hannover Medical School; W. Rutsch, MD, Medical Clinic I, Cardiology, Charité; U. Tebbe, MD, Cardiology Department, Hospital Lippe/Detmold

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