Multifocal spasm with acetylcholine in Prinzmetal angina.

A 60-year-old female patient with Prinzmetal angina and a single non-critical (<50%) focal obstruction in the right coronary artery was referred for percutaneous coronary intervention. Coronary angiography with provocative testing using incremental doses of acetylcholine demonstrated diffuse mild vasoconstriction and multifocal hyperreactive vasoconstriction in apparently normal coronary segments but not at the site of the nonsignificant obstruction. We refrained from intervention and advised avoidance of beta-blockade, and continuation of medical therapy with nitrates and calcium antagonists. (Neth Heart J 2008;16:134-6.).

Continuously improving the practice of cardiology.

Guidelines for the management of patients with cardiovascular disease are designed to assist cardiologists and other physicians in their practice. Surveys are conducted to assess whether guidelines are followed in practice. The results of surveys on acute coronary syndromes, coronary revascularisation, secondary prevention, valvular heart disease and heart failure are presented. Comparing surveys conducted between 1995 and 2002, a gradual improvement in use of secondary preventive therapy is observed. Nevertheless, important deviations from established guidelines are noted, with a significant variation among different hospitals in the Netherlands and in other European countries. Measures for further improvement of clinical practice include more rapid treatment of patients with evolving myocardial infarction, more frequent use of clopidogrel and glycoprotein IIb/IIIa receptor blockers in patients with acute coronary syndromes, more frequent use of ß-blockers in patients with heart failure and more intense measures to encourage patients to stop smoking. Targets for the proportion of patients who might receive specific therapies are presented.

Value of fractional flow reserve in making decisions about bypass surgery for equivocal left main coronary artery disease.

OBJECTIVE: To investigate the value of coronary pressure derived fractional flow reserve (FFR) measurements in supporting decisions about medical or surgical treatment in patients with angiographically equivocal left main coronary artery stenosis. DESIGN: A two centre prospective single cohort follow up study. INTERVENTIONS: FFR of the left main coronary artery was determined in 54 consecutive patients with angiographically equivocal left main coronary artery disease. If FFR was >/= 0.75, medical treatment was chosen; if FFR was < 0.75, surgical treatment was chosen. MAIN OUTCOME MEASURES: Freedom from death, myocardial infarction, or any coronary revascularisation procedure. RESULTS: In 24 patients (44%), FFR was >/= 0.75 and medical treatment was chosen (medical group). In the remaining 30 patients (56%), FFR was < 0.75 and bypass surgery was performed (surgical group). Mean (SD) follow up was 29 (15) months (range 12-65 months). Survival among patients at three years of follow up was 100% in the medical group and 97% in the surgical group. Event-free survival was 76% in the medical group and 83% in the surgical group. CONCLUSIONS: FFR supports decision making in equivocal left main coronary artery disease. If FFR is below 0.75, the decision for bypass surgery is supported. If FFR is above 0.75, a conservative approach is justified.

Continuing medical education in Europe: NVVC, CVOI, ESC, UEMS and EBAC.

The European Board for Accreditation in Cardiology (EBAC) is a joint initiative of the European Society of Cardiology (ESC) and the Cardiology Section of the Union of European Medical Specialists or Union Européenne des Médecins Spécialistes (UEMS). EBAC operates independently from these parent organisations. The ESC is the highest cardiovascular scientific authority in Europe and the most important provider of Continuing Medical Education (CME) in cardiology. The UEMS officially represents the European medical specialists at the European Union (EU). The UEMS consists of different mono-specialist sections, among which the Cardiology Section. The recognition of the importance of CME and the need for quality standards and quality control led the UEMS to establish the European Accreditation Council for CME (EACCME) in January 2000. CME activities that seek European accreditation have to comply with the regulations of this council. As a consequence of the establishment of EACCME, the mono-specialist sections of the UEMS together with the different European scientific societies started to create accreditation boards with the aim to assess international CME activities in accordance with the regulations of UEMS and EACCME. EBAC was founded in 2000. EBAC accreditation is complimentary to national CME accreditation. The Netherlands Society of Cardiology (Nederlandse Vereniging voor Cardiologie, NVVC) and its Institute for CME, the Netherlands Institute for Continuing Cardiovascular Education (Cardio-Vasculair Onderwijs Instituut, CVOI) formally recognise EBAC accreditation and Attendance Certificates.

Pharmacokinetics and hemostatic effects of saruplase in patients with acute myocardial infarction: comparison of infusion, single-bolus, and split-bolus administration.

Saruplase, or unglycosylated, single-chain urokinase-type plasminogen activator (scu-PA) selectively activates fibrin-bound plasminogen, and is subsequently converted to its two-chain derivative tcu-PA (urokinase) by plasmin. The efficacy of a 20 mg IV bolus followed by an infusion of 60 mg over 1 hour (standard regimen) has been demonstrated in acute myocardial infarction (AMI). The Bolus Administration of Saruplase in Europe (BASE) study compared the efficacy of standard therapy, single bolus (80 mg), and split bolus (2 x 40 mg at 30-minute intervals) in AMI. In a substudy of BASE, the pharmacokinetics of total u-PA activity (amidolytic activity after plasmin treatment), high molecular weight (HMW) u-PA antigen, and tcu-PA activity were compared in patients receiving standard therapy (n = 4), single bolus (n = 4), or split bolus (n = 5). Total u-PA activity and HMW u-PA antigen were similar. The maximum concentration (C(max,), mean +/- SD) of total u-PA activity was 2.2 +/- 0.3 microg/mL after standard therapy, 16.3 +/- 3.9 microg/mL after single bolus, and 8.2 +/- 1.6 ug/mL after split bolus. The area under the concentration versus time curve (AUC) values of total u-PA activity were 1.7 +/- 0.1 microg/mL*h (standard therapy), 4.0 +/- 0.9 microg/mL*h (bolus), and 3.0 +/- 0.7 microg/mL*h (split bolus). The dominant initial half-lives (t(1/2) alpha) were 7.1 +/- 1.1 minutes (standard), 8.8 +/- 0.8 minutes (bolus), and 5.1 +/- 2.1 minutes (split bolus). Maximum plasma concentrations of of tcu-PA activity were observed at 5.2 +/- 7 minutes (standard), 21 +/- 10 minutes (bolus), and 42 +/- 2 minutes (split bolus). C(max) was lowest after standard therapy (0.6 +/- 0.3 microg/mL), highest after bolus (4.2 +/- 2.2 microg/mL), and approximately twice as high as standard therapy after split bolus (1. 3 +/- 0.8 microg/mL). After standard therapy the mean fibrinogen concentration decreased gradually from approximately 300 mg/dL to 70 mg/dL at 90 and 120 minutes. After a single bolus the fibrinogen concentration decreased below the limit of quantification within 30 minutes and remained there for at least 120 minutes. Directly after the second 40 mg dose of the split bolus, the fibrinogen levels had an accelerated and more pronounced decrease to approximately 65 mg/dL at 90 and 120 minutes. A single bolus results in very high early total u-PA activity, which accelerates the appearance of tcu-PA activity and fibrinogen consumption. The pharmacokinetics and hemostatic effects of the split-bolus regimen are more comparable with those of standard therapy.

Comparison of quantitative coronary angiography, intravascular ultrasound, and coronary pressure measurement to assess optimum stent deployment.

BACKGROUND: Although intravascular ultrasound (IVUS) is the present standard for the evaluation of optimum stent deployment, this technique is expensive and not routinely feasible in most catheterization laboratories. Coronary pressure-derived myocardial fractional flow reserve (FFRmyo) is an easy, cheap, and rapidly obtainable index that is specific for the conductance of the epicardial coronary artery. In this study, we investigated the usefulness of coronary pressure measurement to predict optimum and suboptimum stent deployment. METHODS AND RESULTS: In 30 patients, a Wiktor-i stent was implanted at different inflation pressures, starting at 6 atm and increasing step by step to 8, 10, 12, and 14 atm, if necessary. After every step, stent deployment was evaluated by quantitative coronary angiography (QCA), IVUS, and coronary pressure measurement. If any of the 3 techniques did not yield an optimum result, the next inflation was performed, and all 3 investigational modalities were repeated until optimum stent deployment was present by all of them or until the treating physician decided to accept the result. Optimum deployment according to QCA was finally achieved in 24 patients, according to IVUS in 17 patients, and also according to coronary pressure measurement in 17 patients. During the step-up, a total of 81 paired IVUS and coronary pressure measurements were performed, of which 91% yielded concordant results (ie, either an optimum or a suboptimum expansion of the stent by both techniques, P<0.00001). On the contrary, QCA showed a low concordance rate with IVUS and FFRmyo (48% and 46%, respectively). CONCLUSIONS: In this study, using a coil stent, both IVUS and coronary pressure measurement were of similar value with respect to the assessment of optimum stent deployment. Therefore, coronary pressure measurement can be used as a cheap and rapid alternative to IVUS for that purpose.

Usefulness of fractional flow reserve to predict clinical outcome after balloon angioplasty.

BACKGROUND: After regular coronary balloon angioplasty, it would be helpful to identify those patients who have a low cardiac event rate. Coronary angiography alone is not sensitive enough for that purpose, but it has been suggested that the combination of optimal angiographic and optimal functional results indicates a low restenosis chance. Pressure-derived myocardial fractional flow reserve (FFR) is an index of the functional severity of the residual epicardial lesion and could be useful for that purpose. METHODS AND RESULTS: In 60 consecutive patients with single-vessel disease, balloon angioplasty was performed by use of a pressure instead of a regular guide wire. Both quantitative coronary angiography (QCA) and measurement of FFR were performed 15 minutes after the procedure. A successful angioplasty result, defined as a residual diameter stenosis (DS) <50%, was achieved in 58 patients. In these patients, DS and FFR, measured 15 minutes after PTCA, were analyzed in relation to clinical outcome. In those 26 patients with both optimal angiographic (residual DS by QCA /=0.90) results, event-free survival rates at 6, 12, and 24 months were 92+/-5%, 92+/-5%, and 88+/-6%, respectively, versus 72+/-8%, 69+/-8%, and 59+/-9%, respectively, in the remaining 32 patients in whom the angiographic or functional result or both were suboptimal (P=0.047, P=0.028, and P=0.014, respectively). CONCLUSIONS: In patients with a residual DS /=0.90, clinical outcome up to 2 years is excellent. Therefore, there is a complementary value of coronary angiography and coronary pressure measurement in the evaluation of PTCA result.

Hemostatic changes after thrombolytic therapy with saruplase (unglycosylated single-chain urokinase-type plasminogen activator) and urokinase (two-chain urokinase-type plasminogen activator).

Urokinase, or two-chain urokinase-type plasminogen activator (tcu-PA), is an effective thrombolytic agent. Its single-chain precursor (scu-PA), unlike tcu-PA, is able to selectively activate fibrin-bound plasminogen. The induced clot lysis is amplified by plasmin-triggered conversion of scu-PA to tcu-PA. The aim of our study was to compare the hemostatic effects of recombinant unglycosylated scu-PA, INN saruplase, and urokinase, at doses considered optimal (80 mg saruplase and 3 million units urokinase) in patients with acute myocardial infarction, within 6 h of onset of pain. Complete sample sets from more than 230 patients in each treatment group have been analyzed. The median hemostatic changes caused by saruplase and urokinase were virtually identical indicating that saruplase is converted early in vivo to its active tcu-PA derivative with the dose regimen used. Fibrinogen degradation products were higher for saruplase with a maximum at 2h. They rose markedly after saruplase from 0.43 mg/l at 0 h to a maximum of 160 mg/l at 2 h, whereas the increase after urokinase (from 0.45 mg/l to 89.0 mg/l) was significantly smaller (P < 0.001).

Recombinant hirudin and front-loaded alteplase in acute myocardial infarction: final results of a pilot study. HIT-I (hirudin for the improvement of thrombolysis).

Recombinant hirudin, a specific thrombin inhibitor, has been shown to accelerate thrombolysis and reduce reocclusions in experimental models. In a pilot trial recombinant hirudin (HBW 023) was used as an adjunctive therapy to thrombolysis with front-loaded tissue plasminogen activator (t-PA) (100 mg.90 min-1) in 40 patients with acute myocardial infarction whose duration of symptoms was less than 6 h. Patients received a bolus of r-hirudin of 0.07 mg.kg-1 b.w. followed by an infusion of 0.05 mg.kg-1.h-1 over 48 h. Complete patency (TIMI grade 3) of the infarct-related artery at 30, 60 and 90 min after the start of thrombolytic therapy was seen in 38.5%, 64.1% and 71.0% of patients, respectively. After 24-48 h, 80% of patients had a complete patent infarct vessel. A very early, complete and sustained patency (TIMI grade 3 at 60 and 90 min and at 24-48 h) was observed in 55% of patients. Reocclusions during the hirudin therapy appeared in six (16.1%) patients, two of whom had a PTCA at 90 min. The only reinfarction was seen after 6 h; this was successfully treated with additional thrombolysis. Major bleedings, mostly related to the invasive procedure, were observed in three patients. Spontaneous organ bleedings and intracerebral haemorrhages did not occur. There was one in-hospital death due to a late retroperitoneal bleeding. In was concluded that, with regard to safety and efficacy, the general feasibility of r-hirudin as adjunctive therapy to thrombolysis with front-loaded t-PA, has been demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of recruitable coronary collateral blood flow in conscious humans and its potential to predict future ischemic events.

OBJECTIVES: The present study was designed to evaluate the applicability of a pressure-flow equation for quantitative calculation of recruitable collateral blood flow at coronary artery occlusion in conscious patients and to investigate the value of that index to predict future ischemic events. BACKGROUND: Recent experimental studies have indicated that recruitable collateral blood flow at coronary artery occlusion can be expressed as a fraction of normal maximal myocardial blood flow by simultaneous recordings of mean arterial, coronary wedge and central venous pressures, respectively. This index is called the pressure-derived fractional collateral flow and is independent of hemodynamic loading conditions. METHODS: In 120 patients undergoing elective coronary angioplasty, mean arterial, coronary wedge and central venous pressures were measured at balloon inflations of 2 min. All patients had a recent exercise electrocardiogram (ECG) with positive findings showing clearly distinguishable, reversible ECG abnormalities, enabling recognition of ischemia at balloon inflation. Fractional collateral blood flow at angioplasty was calculated by coronary wedge pressure minus central venous pressure divided by mean arterial pressure minus central venous pressure and correlated to the presence or absence of ischemia at balloon inflation. Ischemic events were monitored during a follow-up period of 6 to 22 months. RESULTS: In 90 of the 120 patients, ischemia was present at balloon inflation, and in 82 of these patients, fractional collateral blood flow was < or = 23%. By contrast, in 29 patients, no ischemia was present, and fractional collateral blood flow was > 24% in all 29. During the follow-up period, 16 patients had an ischemic event. Fifteen of these 16 patients were in the group with insufficient collateral flow (p < 0.05). CONCLUSIONS: To our knowledge, this study presents the first method for quantitative assessment of recruitable collateral blood flow in humans in the catheterization laboratory. Sufficient and insufficient collateral circulation can be reliably distinguished by this method. Use of this method can also help to provide more insight into the extent and behavior of the collateral circulation for investigational purposes and may have potential clinical implications.

Oral anticoagulation in the prevention of one-year vein graft occlusion after aortocoronary bypass surgery: optimal therapeutic range and practical limitations. CABADAS Research Group of the Interuniversity Cardiology Institute of The Netherlands.

To assess the optimal level of oral anticoagulation to prevent occlusion of vein coronary bypass grafts, 318 patients from a graft patency trial were analysed retrospectively. Oral anticoagulant therapy was started one day before surgery and continued for one year, after which graft occlusion was assessed by angiography. The aimed level of anticoagulation was 2.8-4.8 International Normalized Ratio (INR). Clinical outcome was assessed by the incidence of myocardial infarction, thrombosis and major bleeding. The observed anticoagulation level was 2.8-4.8 INR for 54%, and 1.8-3.8 INR for 75% of time per patient. Occlusion rates in patients who spent < 35, 35-70, and > or = 70% of time within INR range 2.8-4.8 were 10.5%, 10.8% and 11.8%, respectively (differences not statistically significant). Patients who spent > or = 70% of time within INR range 1.8-3.8 versus 2.8-4.8 showed comparable occlusion rates. The risk of graft occlusion was not related to quality of anticoagulation early (0-3 months) or late (3-12 months) after surgery. Myocardial infarction, thrombosis and major bleeding occurred in 1.3%, 2.0% and 2.9% of patients. To maintain vein graft patency in the first postoperative year by oral anticoagulation, a level within INR range 1.8-3.8 for > or = 70% of time seems to be sufficient.

Culprit lesion morphology and stenosis severity in the prediction of reocclusion after coronary thrombolysis: angiographic results of the APRICOT study. Antithrombotics in the Prevention of Reocclusion in Coronary Thrombolysis.

OBJECTIVES: In the APRICOT study (Antithrombotics in the Prevention of Reocclusion In Coronary Thrombolysis), we sought to determine whether angiographic characteristics of the culprit lesion could predict reocclusion after successful thrombolysis and to analyze the influence of three antithrombotic treatment regimens. BACKGROUND: After successful thrombolysis, reocclusion is a major problem. Prediction of reocclusion by angiographic data and choice of antithrombotic treatment would be important for clinical management. METHODS: After thrombolysis, patients were treated with intravenous heparin until initial angiography was performed within 48 h. Patients with a patent infarct-related artery were eligible. Three hundred patients were randomly selected for treatment with coumadin, aspirin (300 mg once daily) or placebo. Patency on a second angiographic study after 3 months was the primary end point of the study. RESULTS: Reocclusion rate was 25% with aspirin, 30% with coumadin and 32% with placebo (p = NS). Lesions with > 90% stenosis reoccluded more frequently (42%) than did those with < 90% stenosis (23%) (p < 0.01). Reocclusion rate of smooth lesions was higher (34%) than that of complex lesions (23%) (p < 0.05). In lesions with < 90% stenosis, the reocclusion rate was lower with aspirin (17%) than with coumadin (25%) or placebo (30%) (p < 0.01). In complex lesions, the reocclusion rate was lower with aspirin (14%) than with coumadin (32%) or placebo (25%) (p < 0.02). Multivariate analysis showed only stenosis severity > 90% to be an independent predictor of reocclusion (odds ratio 2.31, 95% confidence interval 1.28 to 4.18, p = 0.006). CONCLUSIONS: Angiographic features of the culprit lesion after successful coronary thrombolysis significantly predict the risk of reocclusion: high grade (> 90%) stenoses reoccluded more frequently. Aspirin was effective only in complex and less severe lesions (< 90% stenosis). These findings should prompt investigation of the effects of an aggressive approach to patients with severe residual stenosis.

Retrieval of undeployed stents from the right coronary artery: report of two cases.

Two patients are described in whom an undeployed stent (1 Wiktor and 1 Palmaz-Schatz) was retained in the proximal segment of the right coronary artery during coronary angioplasty. In both cases the stent was caught by a technique using a second guidewire. The stent was removed in the first patient during bypass surgery; in the second patient it was removed from the femoral sheath.

Acute myocardial ischaemia and cardiogenic shock after percutaneous transluminal coronary angioplasty; risk factors for and results of emergency coronary bypass.

Between 1 September, 1980 and 1 January, 1989, 4142 patients underwent percutaneous transluminal coronary angioplasty (PTCA). We retrospectively studied the 155 [3.7%; 119 males, mean age 53.4 years, (range 33-78 years) and 36 females, mean age 59.6 years (range 40-74 years)] who required urgent coronary artery bypass grafting (CABG) (Group I) and a select control group of 155 patients, in whom PTCA was performed without complications (Group II). Before PTCA, 14 Group I and 42 Group II patients had angina Class II, and 78 Group I and 49 Group II patients had angina class IV (chi 2-test, P less than 0.05). There were 445 complications in the 155 group I patients: 303 (68%) early (during PTCA) and 141 (32%) late (within 24 h). On arrival in the operating room 126 patients were stable; five were in cardiac arrest and 19 in cardiogenic shock (AS-group; 24 patients). In the AS-group and control group, respectively, angina Class II occurred in 2/24 (8.3%) and 42/155 (27.1%) patients, angina Class IV in 14/24 (58.3%) and 49/155 (31.6%) (P less than 0.05), single-vessel disease in 8/24 (33.3%) and 85/155 (54.8%), triple-vessel disease in 7/24 (29.2%) and 23/155 (14.9%) (P less than 0.05); elective PTCA in 11/24 (45.8%) and 92/155 (59.4%), urgent PTCA in 12/24 (50%) and 48/155 (30.9%) (P less than 0.05), PTCA of the left anterior descending artery (LAD) in 18/24 (75%) and 86/166 (51.8%), PTCA of the right coronary artery in 2/24 (8.3%) and 47/166 (28.3%) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Comparative randomized study of the effectiveness of intravenous recombinant tissue-type plasminogen activator and intravenous streptokinase in patients with acute myocardial infarct. Report of the European Cooperative Study Group for Recombinant Tissue-Type Plasminogen Activator]. / Vergleichende randomisierte Untersuchung zur Wirksamkeit von rekombinantem Gewebe-Plasminogen-Aktivator i.v. und Streptokinase i.v. bei Patienten mit akutem Herzinfarkt. Bericht der Europäischen Gemeinschafts-Studiengruppe für rekombinanten Gewebe-Plasminogen-Akivator.

In a single-blind randomised trial in patients with acute myocardial infarction of less than 6 h duration, the frequency of coronary patency was found to be higher after intravenous administration of recombinant human tissue-type plasminogen activator (rt-PA) than after intravenous streptokinase. 64 patients were allocated to 0.75 mg rt-PA/kg over 90 min, and the infarct-related coronary artery was patent in 70% of 61 assessable coronary angiograms taken 75-90 min after the start of infusion; 65 patients were allocated to 1,500,000 IU streptokinase over 60 min, and the infarct-related vessel was patent in 55% of 62 assessable angiograms. The 95% confidence interval of the difference ranges from +30 to -2% (p = 0.054). Bleeding episodes and other complications were less common in the rt-PA patients than in the streptokinase group. Hospital mortality was identical in the 2 treatment groups. At the end of the rt-PA infusion the circulating fibrinogen level was 61 +/- 35% of the starting value, as measured by a coagulation-rate assay, and 69 +/- 25% as measured by sodium sulphite precipitation. After streptokinase infusion, corresponding fibrinogen levels were 12 +/- 18% and 20 +/- 11%. In the rt-PA group only 4.5% of the fibrinogen was measured as incoagulable fibrinogen degradation products, compared with 30% in the streptokinase group. Activation of the systemic fibrinolytic system was far less pronounced with rt-PA than with streptokinase.

Inadvertant balloon extrusion through a side hole in a guiding catheter.

A patient presented with an acute inferior myocardial infarction. Coronary angiography in the acute stage revealed total occlusion of the right coronary artery. Reperfusion was obtained after intracoronary infusion of 250,000 units of streptokinase. Angioplasty was subsequently performed because of a high grade residual stenosis. An 8-French right Judkins guiding catheter with a single side hole (USCI), a 3.0 mm balloon dilatation catheter (ACS), and a 0.018 high torque floppy guide wire (ACS) were used. After successful angioplasty angiography was repeated with the guide wire in the RCA, but the balloon was withdrawn into the guiding catheter. After injection of contrast, it was impossible to withdrawn the balloon catheter out of the guiding catheter. Fluoroscopy revealed extrusion of the balloon through the side hole in the guiding catheter.

Improved success rate of percutaneous transluminal graft and coronary angioplasty with the El Gamal guiding catheter.

In the period between October 1980 and December 1982 we evaluated the outcome of percutaneous transluminal graft and coronary angioplasty when a Judkins type guiding catheter (J gc) was initially used, but the lesion could not be passed and a subsequent attempt was made with the El Gamal guiding catheter (EG gc). Seven of twelve attempts to dilate stenotic coronary artery bypass grafts failed. The EC gc was tried in six, five were successfully dilated; one failed. Our initial attempts to dilate a stenosed right coronary artery failed in 16 of 68 attempts. The EG gc was attempted in 14. We successfully dilated ten, two dissections required emergency coronary artery bypass grafting (CABG); two failed. Our initial attempts to dilate a left anterior descending artery stenosis failed in 14 of 109 attempts. Six lesions were passed when the EG gc was tried. Five were successfully dilated, and one acute dissection required emergency CABG; eight failed. The EG gc is useful for transluminal angioplasty of stenosed aortocoronary bypass grafts. It increased the success rate of right coronary artery dilatation from 76-91%, but was of limited use in dilatation of left anterior descending lesions.

Balloon inflation caused by contrast injection through the guiding catheter: an unusual observation during coronary angioplasty.

Balloon inflation caused by contrast injection through the guiding catheter has been observed during several angioplasty procedures. The phenomenon is observed when employing an 8F USCI guiding catheter in combination with an ACS dilatation catheter. Two cases demonstrating the phenomenon are described in detail, together with an in vitro experiment that illustrates and quantifies the mechanism.