Melchior Seyfarth

Patient-Specific Induced Pluripotent Stem-Cell Models for Long-QT Syndrome

BACKGROUND Long-QT syndromes are heritable diseases associated with prolongation of the QT interval on an electrocardiogram and a high risk of sudden cardiac death due to ventricular tachyarrhythmia. In long-QT syndrome type 1, mutations occur in the KCNQ1 gene, which encodes the repolarizing potassium channel mediating the delayed rectifier I(Ks) current. METHODS We screened a family affected by long-QT syndrome type 1 and identified an autosomal dominant missense mutation (R190Q) in the KCNQ1 gene. We obtained dermal fibroblasts from two family members and two healthy controls and infected them with retroviral vectors encoding the human transcription factors OCT3/4, SOX2, KLF4, and c-MYC to generate pluripotent stem cells. With the use of a specific protocol, these cells were then directed to differentiate into cardiac myocytes. RESULTS Induced pluripotent stem cells maintained the disease genotype of long-QT syndrome type 1 and generated functional myocytes. Individual cells showed a “ventricular,” “atrial,” or “nodal” phenotype, as evidenced by the expression of cell-type–specific markers and as seen in recordings of the action potentials in single cells. The duration of the action potential was markedly prolonged in “ventricular” and “atrial” cells derived from patients with long-QT syndrome type 1, as compared with cells from control subjects. Further characterization of the role of the R190Q–KCNQ1 mutation in the pathogenesis of long-QT syndrome type 1 revealed a dominant negative trafficking defect associated with a 70 to 80% reduction in I(Ks) current and altered channel activation and deactivation properties. Moreover, we showed that myocytes derived from patients with long-QT syndrome type 1 had an increased susceptibility to catecholamine-induced tachyarrhythmia and that beta-blockade attenuated this phenotype. CONCLUSIONS We generated patient-specific pluripotent stem cells from members of a family affected by long-QT syndrome type 1 and induced them to differentiate into functional cardiac myocytes. The patient-derived cells recapitulated the electrophysiological features of the disorder. (Funded by the European Research Council and others.)

Intracoronary Stenting and Angiographic Results Strut Thickness Effect on Restenosis Outcome (ISAR-STEREO) Trial

OBJECTIVES We tested the hypothesis that thinner-strut stents are associated with a reduced rate of restenosis when comparing two stents with different design. BACKGROUND We have previously shown that, for two stents with similar design, the risk for restenosis is dependent on the strut thickness. It is unknown whether strut thickness preserves its relevance as a determinant of restenosis even in the presence of different stent designs. METHODS A total of 611 patients with symptomatic coronary artery disease were randomly assigned to receive either the thin-strut ACS RX Multilink stent (Guidant, Advanced Cardiovascular Systems, Santa Clara, California) (strut thickness 50 microm, interconnected ring design; n = 309) or the thick-strut BX Velocity stent (Cordis Corp., Miami, Florida) (strut thickness 140 microm, closed cell design; n = 302). The primary end point was angiographic restenosis (> or =50% diameter stenosis at follow-up angiography). Secondary end points were the incidence of target-vessel revascularization (TVR) and the combined rate of death and myocardial infarction (MI) at one year. RESULTS The incidence of angiographic restenosis was 17.9% in the thin-strut group and 31.4% in the thick-strut group, relative risk, 0.57 (95% confidence interval, 0.39 to 0.84), p < 0.001. A TVR due to restenosis was required in 12.3% of the thin-strut group and 21.9% of the thick-strut group, relative risk, 0.56 (95% confidence interval, 0.38 to 0.84), p = 0.002. No significant difference was observed in the combined incidence of death and MI at one year. CONCLUSIONS When two stents with different design are compared, the stent with thinner struts elicits less angiographic and clinical restenosis than the thicker-strut stent.

A Randomized Clinical Trial to Evaluate the Safety and Efficacy of a Percutaneous Left Ventricular Assist Device Versus Intra-Aortic Balloon Pumping for Treatment of Cardiogenic Shock Caused by Myocardial Infarction

OBJECTIVES The aim of this study was to test whether the left ventricular assist device (LVAD) Impella LP2.5 (Abiomed Europe GmbH, Aachen, Germany) provides superior hemodynamic support compared with the intra-aortic balloon pump (IABP). BACKGROUND Cardiogenic shock caused by left ventricular failure is associated with high mortality in patients with acute myocardial infarction (AMI). An LVAD may help to bridge patients to recovery from left ventricular failure. METHODS In a prospective, randomized study, 26 patients with cardiogenic shock were studied. The primary end point was the change of the cardiac index (CI) from baseline to 30 min after implantation. Secondary end points included lactic acidosis, hemolysis, and mortality after 30 days. RESULTS In 25 patients the allocated device (n = 13 IABP, n = 12 Impella LP2.5) could be safely placed. One patient died before implantation. The CI after 30 min of support was significantly increased in patients with the Impella LP2.5 compared with patients with IABP (Impella: DeltaCI = 0.49 +/- 0.46 l/min/m(2); IABP: DeltaCI = 0.11 +/- 0.31 l/min/m(2); p = 0.02). Overall 30-day mortality was 46% in both groups. CONCLUSIONS In patients presenting with cardiogenic shock caused by AMI, the use of a percutaneously placed LVAD (Impella LP 2.5) is feasible and safe, and provides superior hemodynamic support compared with standard treatment using an intra-aortic balloon pump. (Efficacy Study of LV Assist Device to Treat Patients With Cardiogenic Shock [ISAR-SHOCK]; NCT00417378).

Intracoronary Stenting and Angiographic Results

BACKGROUND Increased thrombogenicity and smooth muscle cell proliferative response induced by the metal struts compromise the advantages of coronary stenting. The objective of this randomized, multicenter study was to ascertain whether a reduced strut thickness of a stent is associated with improved follow-up angiographic and clinical results. METHODS AND RESULTS The study covered 651 patients with stenosis in the native coronary arteries > 2.8 mm in diameter. They were randomly assigned to receive 1 of 2 commercially available stents of comparable design but different thickness: 326 patients to the thin-strut stent (strut thickness of 50 microm) and 325 patients to the thicker-strut stent (strut thickness of 140 microm). The primary end point was the angiographic restenosis (> or = 50% diameter luminal stenosis at follow-up angiography). The secondary end points were the incidence of reinterventions due to restenosis-induced ischemia and the total rate of death and myocardial infarctions at 1 year (a combined end point). The incidence of angiographic restenosis was 15.0% in the thin-strut group and 25.8% in the thick-strut group (relative risk, 0.58; 95% CI, 0.39 to 0.87; p = 0.003). Clinical restenosis was also significantly reduced. Reinterventions were made in 8.6% of the thin-strut patients and in 13.8% of the thick-strut patients (relative risk, 0.62; 95% CI, 0.39 to 0.99; p = 0.03). No difference was observed in the combined 1-year rate of death and myocardial infarction. CONCLUSIONS The use of a thin-strut device is associated with a significant reduction of angiographic and clinical restenosis after coronary artery stenting. These findings may have relevant implications for the currently most widely used percutaneous coronary intervention.

Effect of a high loading dose of clopidogrel on platelet function in patients undergoing coronary stent placement

Following coronary stent placement, platelet activation is a major determinant of the risk of subacute stent thrombosis.1 Combined antiplatelet treatment with ticlopidine and aspirin reduced platelet activation after coronary stenting1. Although combined antiplatelet treatment consisting of aspirin and ticlopidine has significantly reduced early ischaemic events following coronary stenting, stent thrombosis still occurs in up to 1% of treated patients, especially in the early days after the intervention, probably because of delayed onset of action of ticlopidine. Clopidogrel is a ticlopidine-like novel thienopyridine inhibitor of ADP induced platelet activation.2 Clopidogrel differs from ticlopidine in that it has a favourable safety profile compared to ticlopidine and reveals an accelerated antiplatelet activity after first administration. The present study sought to investigate the antiplatelet effect of various doses of clopidogrel in patients undergoing coronary stent placement; comparison was made with standard ticlopidine treatment. Thirty patients were randomised into three treatment arms: group I (n = 10), ticlopidine 2 × 500 g as loading dose and 2 × 250 mg daily thereafter; group II (n = 10), clopidogrel 1 × 300 mg loading dose and 1 × 75 mg per day; or group III (n = 10), clopidogrel 1 × 600 mg plus 2 × 75 mg daily thereafter. All patients received aspirin 2 × 100 mg per day concomitantly. Peripheral venous blood samples were taken with a loose tourniquet through a short venous catheter inserted into a forearm vein before and then 2, …

Periprocedural bleeding and 1-year outcome after percutaneous coronary interventions: appropriateness of including bleeding as a component of a quadruple end point.

OBJECTIVES The aim of the study was to investigate the relationship between bleeding within the 30 days after percutaneous coronary interventions (PCI) and 1-year mortality and to assess the appropriateness of inclusion of the periprocedural bleeding in a quadruple composite end point to assess PCI outcome. BACKGROUND Periprocedural bleeding is one of the most frequent complications of PCI. METHODS This study included 5,384 patients from 4 randomized placebo-controlled trials on the value of abciximab after pre-treatment with 600 mg of clopidogrel: ISAR-REACT, -SWEET, -SMART-2, and -REACT-2. Bleeding--defined according to the Thrombolysis In Myocardial Infarction criteria--included all bleeding events within 30 days after enrollment. The primary end point was 1-year mortality. RESULTS In the 4 trials, within the first 30 days there were 42 deaths (0.8%), 314 myocardial infarctions (MIs) (5.8%), 52 urgent revascularizations (1.0%), and 215 bleeding complications (4.0%). Mortality at 1 year was 3.6% (n = 197). A Cox proportional hazards model revealed that the 30-day occurrence of bleeding (hazard ratio [HR] 2.96, 95% confidence interval [CI] 1.96 to 4.48; p < 0.001), MI (HR 2.29, 95% CI 1.52 to 3.46; p < 0.001) and urgent revascularization (HR 2.49, 95% CI 1.16 to 5.35; p = 0.019) independently predicted 1-year mortality. The c statistic was 0.79 for bleeding, 0.78 for MI, and 0.78 for urgent revascularization, demonstrating a comparable discriminatory power of these adverse events for predicting 1-year mortality. CONCLUSIONS Our study demonstrates a strong relationship between the 30-day frequency of bleeding and 1-year mortality after PCI and supports the inclusion of periprocedural bleeding in a 30-day quadruple end point for the assessment of outcome after PCI.

Bivalirudin versus Unfractionated Heparin during Percutaneous Coronary Intervention

BACKGROUND Whether bivalirudin is superior to unfractionated heparin in patients with stable or unstable angina who undergo percutaneous coronary intervention (PCI) after pretreatment with clopidogrel is unknown. METHODS We enrolled 4570 patients with stable or unstable angina (with normal levels of troponin T and creatine kinase MB) who were undergoing PCI after pretreatment with a 600-mg dose of clopidogrel at least 2 hours before the procedure; 2289 patients were randomly assigned in a double-blind manner to receive bivalirudin, and 2281 to receive unfractionated heparin. The primary end point was the composite of death, myocardial infarction, urgent target-vessel revascularization due to myocardial ischemia within 30 days after randomization, or major bleeding during the index hospitalization (with a net clinical benefit defined as a reduction in the incidence of the end point). The secondary end point was the composite of death, myocardial infarction, or urgent target-vessel revascularization. RESULTS The incidence of the primary end point was 8.3% (190 patients) in the bivalirudin group as compared with 8.7% (199 patients) in the unfractionated-heparin group (relative risk, 0.94; 95% confidence interval [CI], 0.77 to 1.15; P=0.57). The secondary end point occurred in 134 patients (5.9%) in the bivalirudin group and 115 patients (5.0%) in the unfractionated-heparin group (relative risk, 1.16; 95% CI, 0.91 to 1.49; P=0.23). The incidence of major bleeding was 3.1% (70 patients) in the bivalirudin group and 4.6% (104 patients) in the unfractionated-heparin group (relative risk, 0.66; 95% CI, 0.49 to 0.90; P=0.008). CONCLUSIONS In patients with stable and unstable angina who underwent PCI after pretreatment with clopidogrel, bivalirudin did not provide a net clinical benefit (i.e., it did not reduce the incidence of the composite end point of death, myocardial infarction, urgent target-vessel revascularization, or major bleeding) as compared with unfractionated heparin, but it did significantly reduce the incidence of major bleeding. (ClinicalTrials.gov number, NCT00262054.)

Restenosis after coronary placement of various stent types

Coronary stent implantation is being performed in an increasing number of patients with a wide spectrum of clinical and lesion characteristics. A variety of stent designs are now available and continuous efforts are being made to improve the stent placement procedure. The objective of this study was to perform a comprehensive analysis of the relation between clinical, lesion, and procedural factors, and restenosis after intracoronary stenting in a large and unselected population of patients. A consecutive series of 4,510 patients with coronary stent placement was analyzed. Exclusion criteria were only a failed procedure and an adverse outcome within the first month after the intervention. Follow-up angiography was performed in 80% of patients at 6 months. Clinical, lesion, and procedural data from all 3,370 patients (4,229 stented lesions) with follow-up angiography were analyzed in a logistic regression model for restenosis (> or =50% diameter stenosis). Clinical factors contributed to the predictive power of the model much less than lesion and procedural factors. The strongest risk factor for restenosis was a small vessel size, with a 79% increase in the risk for a vessel of 2.7 mm versus a vessel of 3.4 mm in diameter. Stent design was the second strongest factor; the incidence of restenosis ranged from 20.0% to 50.3% depending on the stent type implanted. In conclusion, this study demonstrates the predominant role of lesion and procedural factors in determining the occurrence of restenosis after coronary stent placement. Among these factors, stent design appears to play a particularly important role in the hyperplastic response of the vessel wall.

Abciximab in Patients With Acute ST-Segment–Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention After Clopidogrel Loading A Randomized Double-Blind Trial

Background— The glycoprotein IIb/IIIa receptor inhibitor abciximab has improved the efficacy of primary percutaneous coronary interventions in patients with acute myocardial infarction. However, it is not known whether abciximab remains beneficial after adequate clopidogrel loading in patients with acute ST-segment–elevation myocardial infarction. Methods and Results— A total of 800 patients with acute ST-segment–elevation myocardial infarction within 24 hours from symptom onset, all treated with 600 mg clopidogrel, were randomly assigned in a double-blind fashion to receive either abciximab (n=401) or placebo (n=399) in the intensive care unit before being sent to the catheterization laboratory. The primary end point, infarct size measured by single-photon emission computed tomography with technetium-99m sestamibi before hospital discharge, was 15.7±17.2% (mean±SD) of the left ventricle in the abciximab group and 16.6±18.6% of the left ventricle in the placebo group (P=0.47). At 30 days, the composite of death, recurrent myocardial infarction, stroke, or urgent revascularization of the infarct-related artery was observed in 20 patients in the abciximab group (5.0%) and 15 patients in the placebo group (3.8%) (relative risk, 1.3; 95% CI, 0.7 to 2.6; P=0.40). Major bleeding complications were observed in 7 patients in each group (1.8%). Conclusion— Upstream administration of abciximab is not associated with a reduction in infarct size in patients presenting with acute myocardial infarction within 24 hours of symptom onset and receiving 600 mg clopidogrel.

Dantrolene rescues arrhythmogenic RYR2 defect in a patient-specific stem cell model of catecholaminergic polymorphic ventricular tachycardia

Coordinated release of calcium (Ca2+) from the sarcoplasmic reticulum (SR) through cardiac ryanodine receptor (RYR2) channels is essential for cardiomyocyte function. In catecholaminergic polymorphic ventricular tachycardia (CPVT), an inherited disease characterized by stress‐induced ventricular arrhythmias in young patients with structurally normal hearts, autosomal dominant mutations in RYR2 or recessive mutations in calsequestrin lead to aberrant diastolic Ca2+ release from the SR causing arrhythmogenic delayed after depolarizations (DADs). Here, we report the generation of induced pluripotent stem cells (iPSCs) from a CPVT patient carrying a novel RYR2 S406L mutation. In patient iPSC‐derived cardiomyocytes, catecholaminergic stress led to elevated diastolic Ca2+ concentrations, a reduced SR Ca2+ content and an increased susceptibility to DADs and arrhythmia as compared to control myocytes. This was due to increased frequency and duration of elementary Ca2+ release events (Ca2+ sparks). Dantrolene, a drug effective on malignant hyperthermia, restored normal Ca2+ spark properties and rescued the arrhythmogenic phenotype. This suggests defective inter‐domain interactions within the RYR2 channel as the pathomechanism of the S406L mutation. Our work provides a new in vitro model to study the pathogenesis of human cardiac arrhythmias and develop novel therapies for CPVT.