Platelet glycoprotein IIb/IIIa inhibitor tirofiban in clopidogrel-naïve patients undergoing elective percutaneous coronary intervention.

BACKGROUND: The safety of administration of tirofiban, a platelet glycoprotein IIb/IIIa inhibitor, followed by a clopidogrel loading dose in clopidogrel-naïve patients undergoing ad-hoc percutaneous coronary intervention (PCI) is not yet clear. METHODS: In a retrospective observational cohort analysis, clopidogrel-naïve patients undergoing ad-hoc PCI who received a high-dose bolus of tirofiban (25 µg/kg) followed by a 600-mg clopidogrel loading dose (group 1) were compared with patients undergoing elective PCI who were pretreated with clopidogrel (group 2), between September 2014 and October 2021. The primary outcome was major adverse cardiovascular events (MACE) defined as the composite of death, myocardial infarction, stroke, target-lesion revascularisation and bleeding at 30 days. Secondary outcomes were MACE at 7 days and individual components of the primary outcome at 7 and 30 days. RESULTS: A total of 1404 patients were included: 432 (31%) in group 1 and 972 (69%) in group 2. Median age was 69 years, and 28% were female. At 7­day follow-up, MACE occurred in 1.4% in group 1 versus 3.0% in group 2 (p = 0.08). 30-day MACE were observed in 1.9% in group 1 and 4.2% in group 2 (p = 0.03). Secondary outcomes were comparable between the groups. Cox regression analysis, corrected for baseline differences, revealed no significant difference in the primary outcome (hazard ratio: 1.8; 95% confidence interval: 0.8-3.9). CONCLUSION: Ad-hoc PCI in clopidogrel-naïve patients who were treated with high-dose bolus of tirofiban followed by a clopidogrel loading dose immediately after the procedure appeared to be safe.

Long-term follow-up of contemporary drug-eluting stent implantation in diabetic patients: Subanalysis of a randomized controlled trial.

OBJECTIVE: The elevated risk of adverse events following percutaneous coronary intervention in diabetic patients persists with newer-generation DES. The polymer-free amphilimus-eluting stent (PF-AES) possesses characteristics with a potentially enhanced performance in patients with diabetes. Data from the 1-year follow-up period has been previously published. The aim of this subanalysis was to assess long-term performance of two contemporary drug-eluting stents (DES) in a diabetic population. METHODS: In the ReCre8 trial, patients were stratified for diabetes and troponin status, and randomized to implantation of a permanent polymer zotarolimus-eluting stent (PP-ZES) or PF-AES. The primary endpoint was target-lesion failure (TLF), a composite of cardiac death, target-vessel myocardial infarction and target-lesion revascularization. Clinical outcomes between discharge and 3 years follow-up were assessed. RESULTS: A total of 302 patients with diabetes were included in this analysis. After 3 years, TLF occurred in 12.5% of PP-ZES patients versus 10.0% in PF-AES patients (p = 0.46). Similarly, the separate components of TLF were comparable between the two study arms. The secondary composite endpoint of NACE was higher in the PP-ZES arm with 45 cases (29.6%) versus 30 cases (20.0%) in the PF-AES arm (p = 0.036). In the insulin-dependent diabetic population, TLF occurred in 19.1% of PP-ZES patients versus 10.4% of PF-AES patients (p = 0.21). NACE occurred in 40.4% of PP-ZES patients versus 27.1% of PF-AES patients (p = 0.10). CONCLUSIONS: This subanalysis shows that the use of PF-AES results in similar clinical outcomes as compared to PP-ZES, yet some benefits of use of PF-AES in diabetic patients may prevail. Future dedicated trials should confirm these findings.

Prevalence of a History of Metabolic or Hypertensive Pregnancy Disorder in Patients With Myocardial Infarction and Non-obstructive Coronary Arteries: An Observational Cohort Study.

Introduction: Myocardial infarction with non-obstructive coronary arteries (MINOCA) predominantly affects younger females. Women with a history of gestational hypertension (GH), preeclampsia (PE), and gestational diabetes mellitus (GDM) are subjected to an elevated lifetime risk of cardiovascular disease. However, data on the potential association between these obstetric complications and MINOCA is lacking. Therefore, the current study aimed to provide insight in the prevalence of metabolic and hypertensive pregnancy disorders (MHPD) in MINOCA patients and their clinical characteristics. Methods: In this observational cohort study conducted at the Zuyderland Medical Center and Maastricht University Medical Center in the Netherlands, patients were enrolled if they were identified as having MINOCA. Data on individual patient characteristics, laboratory results, electrocardiography as well as (non-)invasive imaging procedures were derived from the electronic health record system. Patients were asked to complete a questionnaire about prior MHPD including GDM, GH, and PE. Patients were grouped into those with MHPD and those with prior uncomplicated normotensive pregnancy (or pregnancies; NP). Results: After excluding patients without 1-year follow-up (n = 53), 86 female MINOCA patients remained eligible for analysis. Of the total female population, 25 (29.1%) patients had MHPD, including GH (n = 19; 22.1%), PE (n = 4; 4.7%), and GDM (n = 7; 8.1%). The MHPD patients showed higher rates of chronic hypertension (84.0 vs. 55.7%; p = 0.013), hypercholesterolemia (64.0 vs. 34.4%; p = 0.012), a family history of CVD (84.0 vs. 45.9%; p = 0.001), gout or rheumatic arthritis (16.0 vs. 1.6%; p = 0.024), and were more often non-smokers (45.8 vs. 78.3%; p = 0.004), compared to the NP patients. Moreover, MHPD patients were more likely to use cardiovascular medications at baseline. A trend toward no specific cause found for the MINOCA event was observed in MHPD patients compared to the NP group (64.0 vs. 42.6%, p = 0.072). Conclusion: A history of metabolic and hypertensive pregnancy disorders occurred in one-third of female MINOCA patients. In these patients, conventional cardiovascular risk factors were more prevalent compared to NP patients. In most MHPD patients, the specific cause for MINOCA remained unclear.

Impact of opioids on P2Y12 receptor inhibition in patients with ST-elevation myocardial infarction who are pre-treated with crushed ticagrelor: Opioids aNd crushed Ticagrelor In Myocardial infarction Evaluation (ON-TIME 3) trial.

AIMS: Platelet inhibition induced by P2Y12 receptor antagonists in patients with ST-elevation myocardial infarction (STEMI) can be affected by concomitant use of opioids. The aim of this trial was to examine the effect of intravenous (iv) acetaminophen compared with iv fentanyl on P2Y12 receptor inhibition in patients with STEMI. METHODS AND RESULTS: The Opioids aNd crushed Ticagrelor In Myocardial infarction Evaluation (ON-TIME 3) trial randomized 195 STEMI patients who were scheduled to undergo primary percutaneous coronary intervention (PCI) and were pre-treated with crushed ticagrelor to iv acetaminophen (N = 98) or iv fentanyl (N = 97) in the ambulance. The primary endpoint, consisting of the level of platelet reactivity units (PRU) measured immediately after primary PCI, was not significantly different between the study arms [median PRU 104 (IQR 37-215) vs. 175 (63-228), P = 0.18]. However, systemic levels of ticagrelor were significantly higher in the acetaminophen arm at the start of primary PCI [151 ng/mL (32-509) vs. 60 ng/mL (13-206), P = 0.007], immediately after primary PCI [326 ng/mL (94-791) vs. 115 ng/mL (38-326), P = 0.002], and at 1 h after primary PCI [488 ng/mL (281-974) vs. 372 ng/mL (95-635), P = 0.002]. Acetaminophen resulted in the same extent of pain relief when compared with fentanyl [reduction of 3 points on 10-step-pain scale before primary PCI (IQR 1-5)] in both study arms (P = 0.67) and immediately after PCI [reduction of 5 points (3-7); P = 0.96]. CONCLUSION: The iv acetaminophen in comparison with iv fentanyl was not associated with significantly lower platelet reactivity in STEMI patients but resulted in significantly higher ticagrelor plasma levels and was effective in pain relief.

Clinical outcomes after permanent polymer or polymer-free stent implantation in patients with diabetes mellitus: The ReCre8 diabetes substudy.

OBJECTIVES: The purpose of this analysis was to compare target-lesion failure (TLF) of a permanent polymer zotarolimus-eluting stent (PP-ZES) versus a polymer-free amphilimus-eluting stent (PF-AES) in diabetics. BACKGROUND: The improvement of outcomes with new-generation drug-eluting stent as seen in the general population is less pronounced among diabetics. The PF-AES introduces an elution-technology with potential enhanced performance in diabetics. METHODS: In this subanalysis of the ReCre8 trial, patients were randomized to either a PP-ZES or PF-AES after stratification for diabetes and troponin status. The primary device-oriented endpoint was TLF, a composite of cardiac death, target-vessel myocardial infarction and target-lesion revascularization. RESULTS: In the ReCre8 trial, 304 (20%) patients were diabetic and 96 (6%) had insulin-dependent diabetes mellitus. There was no statistically significant difference between the two study arms regarding the primary endpoint (PP-ZES 7.2% vs. PF-AES 4.0%; p = .21), although the composite of net adverse clinical events was higher in the PP-ZES arm (15.7 vs. 8.0%; p = .035). Stent thrombosis was low in both groups with no cases in the PP-ZES arm and 1 case in the PF-AES arm (p = .32). Regarding insulin-treated diabetics, TLF was higher in the PP-ZES arm (14.9 vs. 2.1%; p = .022). CONCLUSIONS: Diabetics could potentially benefit from a dedicated stent, releasing sirolimus with a lipophilic carrier (amphilimus-formulation). Future trials should confirm the potential benefit of a PF-AES in this population.

High bleeding risk in patients undergoing percutaneous coronary intervention with drug-eluting stent implantation: ReCre8 subanalysis.

Objectives: In an all-comers cohort undergoing percutaneous coronary intervention (PCI), we aimed to assess prevalence of high bleeding risk (HBR) patients and impact of HBR and dual antiplatelet therapy (DAPT) on clinical events. Background: HBR represents a complex subgroup of patients undergoing PCI. Methods: In the ReCre8 trial, patients undergoing PCI were stratified for troponin status and diabetes and randomized to a permanent polymer zotarolimus-eluting- or polymer-free amphilimus-eluting stent. Patients were treated with 12 months (troponin-positive) or one month (troponin-negative) of DAPT. We evaluated clinical outcomes in patients with and without HBR according to the Academic Research Consortium for High Bleeding Risk criteria. Results: From a total of 1488 patients included in this subanalysis, 406 patients (27.3 %) were identified as being at HBR. Among HBR patients, target-lesion failure (TLF) was similar after one year yet was higher after three years (13.3 % vs. 9.1 %; p = 0.013), compared to non-HBR patients. There was no difference in Bleeding Academic Research Consortium (BARC) 3 to 5 bleeding, however BARC 2 to 5 bleeding was higher after three years with 4.9 % vs. 3.0 % (p = 0.037). There were no differences between troponin-positive (12-months DAPT) and -negative (1-month DAPT) HBR patients with respect to ischemic and bleeding outcomes. Conclusions: In this all-comers population of PCI patients, a higher TLF rate among HBR patients at long-term follow-up was found, underlining the complexities involving treatment of HBR patients. We did not observe statistically significant differences in BARC 3 to 5 bleeding between HBR and non-HBR patients regardless of DAPT duration. Clinical trial registration: URL: http://www.clinicaltrials.gov, unique identifier: NCT02328898.

3-Year Clinical Outcomes After Implantation of Permanent-Polymer Versus Polymer-Free Stent: ReCre8 Landmark Analysis.

OBJECTIVES: The aim of this analysis was to assess long-term clinical outcomes of the polymer-free Amphilimus-eluting stent (PF-AES) compared with a latest generation permanent-polymer drug-eluting stent (DES) in an all-comers population. BACKGROUND: PF-AES possess multiple properties improving targeted drug elution without the presence of polymers. Evaluation of long-term clinical performance of PF-AES versus latest generation permanent-polymer DES has not yet been performed in a large randomized trial introducing shortened dual-antiplatelet therapy. METHODS: In this physician-initiated, multicenter, randomized, all-comers trial, patients undergoing percutaneous coronary intervention with implantation of DES were enrolled. Patients were stratified for diabetes and troponin status and randomized to implantation of a permanent-polymer zotarolimus-eluting stent (PP-ZES) or a PF-AES. Dual-antiplatelet therapy duration was 12 months in troponin-positive patients and 1 month in troponin-negative patients. A noninferiority analysis was conducted to compare the 2 arms regarding target lesion failure (TLF) between 1 and 3 years. RESULTS: A total of 1,491 patients were randomized and treated. In this landmark analysis, between 1- and 3-year follow-up, TLF occurred in 35 patients (4.9%) in the PP-ZES arm and 37 PF-AES patients (5.1%). Clinical noninferiority of the PF-AES was confirmed, with a risk difference of 0.2% (upper limit 1-sided 95% CI: 2.2%; Pnoninferiority = 0.0031). CONCLUSIONS: ReCre8 (Randomized "All-Comer" Evaluation of a Permanent Polymer Resolute Integrity Stent Versus a Polymer Free Cre8 Stent) is the first randomized, multicenter trial with a head-to-head comparison of PP-ZES compared with PF-AES to investigate clinical outcomes of these new-generation DES in an all-comers population with long-term follow-up. On the basis of the present results, PF-AES are clinically noninferior to PP-ZES regarding TLF between 1 and 3 years. (Randomized "All-Comer" Evaluation of a Permanent Polymer Resolute Integrity Stent Versus a Polymer Free Cre8 Stent; NCT02328898).

Long-term outcome after deferred revascularization due to negative fractional flow reserve in intermediate coronary lesions.

OBJECTIVES: The aim was to assess long-term outcome after deferring intervention of coronary lesions with a fractional flow reserve (FFR) value of >0.80 in a real-world patient population and then to identify factors associated with deferred target lesion failure (DTLF). BACKGROUND: Deferring coronary interventions of intermediate lesions based on FFR measurement is safe, irrespective of the extent of coronary artery disease. However, FFR values near the cut-off of >0.80 may have less favorable outcome. METHODS: A retrospective analysis was performed in patients with deferred coronary intervention based on FFR value >0.80. The primary endpoint was DTLF, a composite of acute coronary syndrome (ACS) and any coronary revascularization, related to the initially deferred stenosis. RESULTS: A total of 600 patients, mean age of 66 ± 10 years, and 751 coronary lesions with negative FFR values (mean 0.88 ± 0.04) were included. The mean follow-up was 27 ± 15 months. DTLF occurred in 44 patients (7.3%), revascularization in 42 (7%), and ACS without revascularization in 2 patients (0.3%). Patients with DTLF more often had diabetes mellitus, previous coronary artery bypass grafting, multivessel disease (MVD), and lower FFR at inclusion. Multivariable regression analysis showed that lower deferred FFR values [FFR 0.81-0.85: hazard ratio (HR) 2.79 (95% CI [confidence interval]; 1.46-5.32), p .002], MVD [HR 1.98 (95% CI; 1.05-3.75), p .036], distal lesions [HR 2.43 (95% CI; 1.29-4.57), p .006], and lesions located in a saphenous vein graft (SVG) [HR 6.35 (95% CI; 1.81-22.28), p .004] were independent predictors for DTLF. CONCLUSIONS: The long-term rate of DTLF of initially deferred coronary lesions was 7.3%. Independent predictors for DTLF are lower deferred FFR value, the presence of MVD, distal lesions, and lesions in SVG.

Randomized All-Comers Evaluation of a Permanent Polymer Zotarolimus-Eluting Stent Versus a Polymer-Free Amphilimus-Eluting Stent.

BACKGROUND: Polymer-free amphilimus-eluting stents (PF-AES) represent a novel elution technology in the current era of drug-eluting stents. The clinical safety and efficacy of PF-AES as compared with latest-generation permanent-polymer zotarolimus-eluting stents (PP-ZES) have not yet been investigated in a large randomized trial. METHODS: In this physician-initiated, prospective, multicenter, randomized, noninferiority trial, an all-comers population requiring percutaneous coronary intervention was enrolled across 3 European sites. Randomization (1:1 ratio) to PP-ZES or PF-AES was performed after stratification for troponin status and diabetes mellitus. In both treatment arms, troponin-positive patients were planned for 12-month dual antiplatelet therapy, whereas troponin-negative patients were planned for 1-month dual antiplatelet therapy. Outcome assessors were blinded to the allocated treatment. The device-oriented primary end point of target-lesion failure was defined as cardiac death, target-vessel myocardial infarction, or target-lesion revascularization at 12-months as analyzed by modified intention-to-treat (80% power, and a 3.5% noninferiority margin). RESULTS: In total, 1502 patients were randomized and 1491 treated with the assigned stent and available for follow-up. The primary end point occurred in 42 (5.6%) of the 744 patients receiving PP-ZES versus 46 (6.2%) of the 747 patients receiving PF-AES. PF-AES were clinically noninferior to PP-ZES (risk difference, 0.5%; upper limit 1-sided 95% confidence interval, 2.6%; Pnoninferiority=0.0086). Cardiac death occurred in 10 (1.3%) versus 10 patients (1.3%; P value for difference, 1.00), target-vessel myocardial infarction occurred in 18 (2.4%) versus 17 patients (2.3%; P value for difference, 0.87), and target-lesion revascularization occurred in 22 (2.9%) versus 20 patients (2.6%; P value for difference, 0.75) for PF-AES as compared with PP-ZES. Overall, definite or probable stent thrombosis occurred in 1.0%. CONCLUSIONS: PF-AES were noninferior to PP-ZES regarding target-lesion failure at 12 months. Findings regarding the secondary end point and prespecified subgroups were generally consistent with that of the primary end point. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier: NCT02328898.

Rationale and design of amphilimus sirolimus-eluting stents versus zotarolimus-eluting stents in all-comers requiring percutaneous coronary intervention (ReCre8): A multicenter randomized clinical trial.

BACKGROUND: Amphilimus sirolimus-eluting stents (A-SES) represent a novel elution technology in the current era of drug-eluting stents with promising results in patients with diabetes mellitus. At present no large trial has been designed to evaluate clinical outcomes of A-SES as compared to new-generation drug-eluting stents in unselected patients. Accordingly, we designed this trial to evaluate clinical noninferiority of A-SES as compared with zotarolimus-eluting stents (ZES) in a real-world, all-comers setting. STUDY DESIGN: ReCre8 is a prospective multicenter randomized clinical trial evaluating the clinical outcomes of A-SES as compared with ZES in all-comers requiring percutaneous coronary intervention. Patients are randomized 1:1 to receive either A-SES or ZES. On-site block-randomization is stratified by diabetes mellitus, and troponin status to perform prespecified subanalyses. Patients receive 1-month of dual antiplatelet therapy (DAPT) when troponin-negative, or 12-months of DAPT when troponin-positive. The primary endpoint is target-lesion failure at 1-year follow-up. A total of 1,532 patients will be enrolled to demonstrate clinical noninferiority of A-SES with at least 80% power, a noninferiority margin of 3.5% and a type-I-error of 0.05. CONCLUSIONS: ReCre8 (NCT02328898) is the first randomized multicenter trial with a head-to-head comparison of A-SES as compared with ZES to investigate the clinical safety and efficacy of these new-generation DES in a real-world, all-comers population.

Clinical outcomes of complex real-world diabetic patients treated with amphilimus sirolimus-eluting stents or zotarolimus-eluting stents: A single-center registry.

OBJECTIVE: To assess clinical outcomes of Amphilimus Sirolimus-Eluting Stents (A-SES) as compared to Zotarolimus-Eluting Stents (ZES) in complex real-world diabetic patients. BACKGROUND: Patients with diabetes mellitus represent one of the most challenging scenarios with high rates of restenosis and stent thrombosis in the current era of drug-eluting stents. Hence, we assessed the safety of A-SES versus ZES in complex diabetic patients. METHODS: In this observational study, we analyzed all consecutive patients with diabetes mellitus referred to our center from November 2012 to November 2014. The primary outcome was target-lesion failure at 1-year follow-up. RESULTS: A total of 165 consecutive diabetic patients underwent percutaneous coronary intervention with A-SES or ZES for stable coronary artery disease in our tertiary center. Using the Kaplan Meier method the cumulative incidence of target-lesion failure was 6.7% (5.9% A-SES versus 7.5% ZES, p=0.19) at 1-year follow-up. Event-free survival at 1year follow-up was similar (89.4% A-SES vs. 83.3% ZES, p=0.29). Interestingly, we did not find any cases of definite-, and only one case of probable stent thrombosis in this high risk cohort. CONCLUSION: In this real-world registry, A-SES and ZES seems to be associated with promising 1-year clinical safety outcomes following PCI in a contemporary cohort of high-risk diabetic patients. Our results should be considered hypothesis generating, as the clinical safety of A-SES has to be confirmed in a large trial.

Spatial Heterogeneity of Cx43 is an Arrhythmogenic Substrate of Polymorphic Ventricular Tachycardias during Compensated Cardiac Hypertrophy in Rats.

BACKGROUND: Ventricular remodeling increases the propensity of ventricular tachyarrhythmias and sudden death in patients. We studied the mechanism underlying these fatal arrhythmias, electrical and structural cardiac remodeling, as well as arrhythmogeneity during early, compensated hypertrophy in a rat model of chronic pressure overload. METHODS: Twenty-six Wistar rats were subjected to transverse aortic constriction (TAC) (n = 13) or sham operation (n = 13). Four weeks postoperative, echo- and electrocardiography was performed. Epicardial (208 or 455 sites) and transmural (30 sites) ventricular activation mapping was performed on Langendorff perfused hearts. Subsequently, hearts were processed for (immuno)histological and molecular analyses. RESULTS: TAC rats showed significant hypertrophy with preserved left ventricular (LV) function. Epicardial conduction velocity (CV) was similar, but more dispersed in TAC. Transmural CV was slowed in TAC (37.6 ± 2.9 cm s(-1)) compared to sham (58.5 ± 3.9 cm s(-1); P < 0.01). Sustained polymorphic ventricular tachycardias were induced from LV in 8/13 TAC and in 0/13 sham rats. During VT, electrical activation patterns showed variable sites of earliest epicardial activation and altering sites of functional conduction block. Wandering epicardial reentrant activation was sporadically observed. Collagen deposition was significantly higher in TAC compared to sham, but not different between arrhythmogenic and non-arrhythmogenic TAC animals. Connexin43 (Cx43) expression was heterogeneous with a higher prevalence of non-phosphorylated Cx43 in arrhythmogenic TAC animals. CONCLUSION: In TAC rats with compensated cardiac hypertrophy, dispersion of conduction correlated to arrhythmogenesis, an increased heterogeneity of Cx43, and a partial substitution with non-phosphorylated Cx43. These alterations may result in the increased vulnerability to polymorphic VTs.

Reduced heterogeneous expression of Cx43 results in decreased Nav1.5 expression and reduced sodium current that accounts for arrhythmia vulnerability in conditional Cx43 knockout mice.

BACKGROUND: Reduced expression of connexin43 (Cx43) and sodium channel (Nav1.5) and increased expression of collagen (fibrosis) are important determinants of impulse conduction in the heart. OBJECTIVE: To study the importance and interaction of these factors at very low Cx43 expression, inducible Cx43 knockout mice with and without inducible ventricular tachycardia (VT) were compared through electrophysiology and immunohistochemistry. METHODS: Cx43(CreER(T)/fl) mice were induced with tamoxifen and killed after 2 weeks. Epicardial activation mapping was performed on Langendorff-perfused hearts, and arrhythmia vulnerability was tested. Mice were divided into arrhythmogenic (VT+; n = 13) and nonarrhythmogenic (VT-; n = 10) animals, and heart tissue was analyzed for Cx43, Nav1.5, and fibrosis. RESULTS: VT+ mice had decreased Cx43 expression with increased global, but not local, heterogeneity of Cx43 than did VT- mice. Nav1.5-immunoreactive protein expression was lower in VT+ than in VT- mice, specifically at sites devoid of Cx43. Levels of fibrosis were similar between VT- and VT+ mice. QRS duration was increased and epicardial activation was more dispersed in VT+ mice than in VT- mice. The effective refractory period was similar between the 2 groups. Premature stimulation resulted in a more severe conduction slowing in VT+ than in VT- hearts in the right ventricle. Separate patch-clamp experiments in isolated rat ventricular myocytes confirmed that the loss of Cx43 expression correlated with the decreased sodium current amplitude. CONCLUSIONS: Global heterogeneity in Cx43 expression and concomitant heterogeneous downregulation of sodium-channel protein expression and sodium current leads to slowed and dispersed conduction, which sensitizes the heart for ventricular arrhythmias.

A 50% reduction of excitability but not of intercellular coupling affects conduction velocity restitution and activation delay in the mouse heart.

INTRODUCTION: Computer simulations suggest that intercellular coupling is more robust than membrane excitability with regard to changes in and safety of conduction. Clinical studies indicate that SCN5A (excitability) and/or Connexin43 (Cx43, intercellular coupling) expression in heart disease is reduced by approximately 50%. In this retrospective study we assessed the effect of reduced membrane excitability or intercellular coupling on conduction in mouse models of reduced excitability or intercellular coupling. METHODS AND RESULTS: Epicardial activation mapping of LV and RV was performed on Langendorff-perfused mouse hearts having the following: 1) Reduced excitability: Scn5a haploinsufficient mice; and 2) reduced intercellular coupling: Cx43(CreER(T)/fl) mice, uninduced (50% Cx43) or induced (10% Cx43) with Tamoxifen. Wild type (WT) littermates were used as control. Conduction velocity (CV) restitution and activation delay were determined longitudinal and transversal to fiber direction during S(1)S(1) pacing and S(1)S(2) premature stimulation until the effective refractory period. In both animal models, CV restitution and activation delay in LV were not changed compared to WT. In contrast, CV restitution decreased and activation delay increased in RV during conduction longitudinal but not transverse to fiber direction in Scn5a heterozygous animals compared to WT. In contrast, a 50% reduction of intercellular coupling did not affect either CV restitution or activation delay. A decrease of 90% Cx43, however, resulted in decreased CV restitution and increased activation delay in RV, but not LV. CONCLUSION: Reducing excitability but not intercellular coupling by 50% affects CV restitution and activation delay in RV, indicating a higher safety factor for intercellular coupling than excitability in RV.

Heterogeneous Connexin43 distribution in heart failure is associated with dispersed conduction and enhanced susceptibility to ventricular arrhythmias.

AIMS: Sudden arrhythmogenic cardiac death is a major cause of mortality in patients with congestive heart failure (CHF). To investigate determinants of the increased arrhythmogenic susceptibility, we studied cardiac remodelling and arrhythmogenicity in CHF patients and in a mouse model of chronic pressure overload. METHODS AND RESULTS: Clinical and (immuno)histological data of myocardial biopsies from CHF patients with (VT+) and without (VT-) documented ventricular arrhythmia were compared with controls. In CHF patients, ejection fraction was decreased and QRS duration was increased. Cell size and interstitial fibrosis were increased, but Connexin43 (Cx43) levels, the most abundant gap junction in ventricular myocardium, were unchanged. No differences were found between VT+ and VT- patients, except for the distribution pattern of Cx43, which was significantly more heterogeneous in VT+. Mice were subjected to transverse aortic constriction (TAC) or sham operated. At 16 weeks, cardiac function was determined by echocardiography and epicardial ventricular activation mapping was performed. Transverse aortic constriction mice had decreased fractional shortening and prolonged QRS duration. Right ventricular conduction velocity was reduced, and polymorphic VTs were induced in 44% TAC and 0% sham mice. Interstitial fibrosis was increased and Cx43 quantity was unchanged in TAC mice with and without arrhythmias. Similar to CHF patients, heterogeneous Cx43 distribution was significantly associated with arrhythmias in TAC mice and with spatial heterogeneity of impulse conduction. CONCLUSION: Heterogeneous Cx43 expression during CHF is associated with dispersed impulse conduction and may underlie enhanced susceptibility to ventricular tachyarrhythmias.

Reduction of fibrosis-related arrhythmias by chronic renin-angiotensin-aldosterone system inhibitors in an aged mouse model.

Myocardial fibrosis increases arrhythmia vulnerability of the diseased heart. The renin-angiotensin-aldosterone system (RAAS) governs myocardial collagen synthesis. We hypothesized that reducing cardiac fibrosis by chronic RAAS inhibition would result in reduced arrhythmia vulnerability of the senescent mouse heart. Wild-type mice (52 wk old) were treated for 36 wk: 1) untreated control (C); 2) eplerenone (E); 3) losartan (L); and 4) cotreatment with eplerenone and losartan (EL). Ventricular epicardial activation mapping was performed on Langendorff-perfused hearts. Arrhythmia inducibility was tested by one to three premature stimuli and burst pacing. Longitudinal and transverse conduction velocity and dispersion of conduction were determined during pacing at a basic cycle length of 150 ms. Sirius red staining (collagen) was performed. As a result, in the RV of mice in the E, L, and EL groups, transverse conduction velocity was significantly increased and anisotropic ratio was significantly decreased compared with those values of mice in the C group. Anisotropic reentrant arrhythmias were induced in 52% of untreated mice and significantly reduced to 22%, 26%, and 16% in the E, L, and EL groups, respectively. Interstitial fibrosis was significantly decreased in both the RV and LV of all treated groups. Scattered patches of replacement fibrosis were found in 90% of untreated hearts, which were significantly reduced in the E, L, and EL groups. A strong correlation between the abundance of patchy fibrosis and arrhythmia inducibility was found. In conclusion, chronic RAAS inhibition limited aging-related interstitial fibrosis. The lower arrhythmogeneity of treated mice was directly correlated to the reduced amount of patchy fibrosis.

Combined reduction of intercellular coupling and membrane excitability differentially affects transverse and longitudinal cardiac conduction.

AIMS: Reduced excitability and gap junction expression are commonly found in electrically remodelled diseased hearts, but their contribution to slow conduction and arrhythmias is unclear. In this study, we have investigated the effect of isolated and combined reductions in membrane excitability and intercellular coupling on impulse propagation and arrhythmogeneity in genetically modified mice. METHODS AND RESULTS: Cx43 and Scn5a(1798insD/+) heterozygous (HZ) mice were crossbred to create a mixed offspring: wild-type (WT, n = 15), Cx43 HZ (n = 14), Scn5a(1798insD/+) (Scn5a) HZ (n = 17), and Cx43/Scn5a(1798insD/+) (Cx43/Scn5a) HZ (n = 15) mice. After ECG recording, epicardial activation mapping (208 recording sites) was performed on Langendorff-perfused hearts. Arrhythmia inducibility was tested by one to three premature stimuli and burst pacing. Conduction velocity longitudinal (CV(L)) and transverse (CV(T)) to fibre orientation and dispersion of conduction were determined during S1-S1 pacing (150 ms). Connexin43 (Cx43) and sodium channel Nav1.5 protein expression and myocardial tissue collagen content were determined by immunohistology. Compared with WT animals, P, QRS, and QTc intervals were prolonged in Scn5a HZ and Cx43/Scn5a HZ, but not in Cx43 HZ animals. Scn5a HZ mice showed decreased CV(L) in right ventricle (RV) but not in left ventricle compared with WT. In the RV of Cx43/Scn5a HZ, CV(T) was reduced, but CV(L) was not different from WT. Arrhythmia inducibility was low and not increased in either single- or double-mutant mice. CONCLUSION: Reduction of both electrical coupling and excitability results in normal conduction velocity parallel to fibre orientation but in pronounced conduction slowing transverse to fibre orientation in RV only, although this does not affect arrhythmogeneity.

Dominant arrhythmia vulnerability of the right ventricle in senescent mice.

BACKGROUND: Several cardiac disorders affect the right ventricle (RV) and left ventricle (LV) equally, but nevertheless, RV vulnerability to conduction slowing and arrhythmias exceeds that of the LV. OBJECTIVE: This study sought to assess the mechanism of dominant RV arrhythmia vulnerability in senescent mice as a model of general reduced myocardial integrity. METHODS: Epicardial ventricular activation mapping was performed on senescent (22 months) and adult (3 months) Langendorff perfused mouse hearts. Arrhythmia inducibility was tested by programmed stimulation. Conduction velocity longitudinal and transversal (CVT) to fiber orientation, conduction heterogeneity, and effective refractory period were determined. Subsequently, hearts were processed for immunohistochemistry, Western blotting, and Sirius red staining. RESULTS: In senescent RV, but not LV, CVT was reduced and wavelength decreased, whereas anisotropic ratio and conduction heterogeneity increased. Arrhythmias, based on anisotropic reentry, were induced in 55% of senescent hearts only and predominantly in RV. In senescent mice, Connexin 43 (Cx43) and Cardiac Sodium Channel (Nav1.5) were decreased and interstitial fibrosis increased comparably in RV and LV. However, in senescent mice, heterogeneously distributed patches of replacement fibrosis were present throughout the entire RV myocardium, but only in midendocardium and subendocardium of LV. Cx43 expression in these areas was disrupted. CONCLUSION: Widespread presence of replacement fibrosis in senescent RV compared with LV, combined with Cx43 and Nav1.5 disruption, potentiate shorter wavelength, conduction slowing, and conduction heterogeneity in RV, resulting in greater vulnerability of senescent RV to arrhythmias.

Impaired impulse propagation in Scn5a-knockout mice: combined contribution of excitability, connexin expression, and tissue architecture in relation to aging.

BACKGROUND: The SCN5A sodium channel is a major determinant for cardiac impulse propagation. We used epicardial mapping of the atria, ventricles, and septae to investigate conduction velocity (CV) in Scn5a heterozygous young and old mice. METHODS AND RESULTS: Mice were divided into 4 groups: (1) young (3 to 4 months) wild-type littermates (WT); (2) young heterozygous Scn5a-knockout mice (HZ); (3) old (12 to 17 months) WT; and (4) old HZ. In young HZ hearts, CV in the right but not the left ventricle was reduced in agreement with a rightward rotation in the QRS axes; fibrosis was virtually absent in both ventricles, and the pattern of connexin43 (Cx43) expression was similar to that of WT mice. In old WT animals, the right ventricle transversal CV was slightly reduced and was associated with interstitial fibrosis. In old HZ hearts, right and left ventricle CVs were severely reduced both in the transversal and longitudinal direction; multiple areas of severe reactive fibrosis invaded the myocardium, accompanied by markedly altered Cx43 expression. The right and left bundle-branch CVs were comparable to those of WT animals. The atria showed only mild fibrosis, with heterogeneously disturbed Cx40 and Cx43 expression. CONCLUSIONS: A 50% reduction in Scn5a expression alone or age-related interstitial fibrosis only slightly affects conduction. In aged HZ mice, reduced Scn5a expression is accompanied by the presence of reactive fibrosis and disarrangement of gap junctions, which results in profound conduction impairment.