Outcomes of endovascular treatment for popliteal artery disease.

Background: Finding the appropriate endovascular revascularization strategy for patients with peripheral artery disease and a popliteal artery lesion remains particulary challenging. Data regarding predictors for a beneficial outcome are scarce. Patients and methods: All endovascular procedures of popliteal artery lesions (n=227) performed in 197 patients between February 2009 and May 2018 at our institution were retrospectively analyzed. Hemodynamically relevant restenosis represented the primary endpoint. Results: The overall technical success rate was 98% and yielded 99% for stenoses (n=145) and 97% for occlusions (n=82). In a median follow-up of 10 months, the overall rate of restenosis was 23%. After 1 and 2 years, the primary patency rates were 76% and 55% and the secondary patency rate was 100%, respectively. The estimated probability of restenosis was significantly higher in stented lesions (stent vs. no stent; 36.0% vs. 19.1%; p=0.030). Multivariate analysis identified stent implantation (hazard ratio: 2.4; overall P=0.010) and diabetes (hazard ratio 2.0; P=0.023) as significant predictors for the development of restenosis. Conclusions: Endovascular therapy for popliteal artery disease was associated with high technical success rates and accompanied with a promising mid-term outcome, particularly in lesions treated with balloon angioplasty alone.

Frequency of subclavian artery stenosis in patients with mammarian artery coronary bypass and suspected coronary artery disease progression.

We retrospectively analyzed patient records of all patients with a history of internal mammarian artery (IMA) coronary bypass undergoing coronary angiography at two cardiovascular centers between January 1st 1999 and December 31st 2019. A total of 11,929 coronary angiographies with or without percutaneous coronary intervention were carried out in 3921 patients. Our analysis revealed 82 (2%) patients with documented subclavian artery stenosis. Of these, 8 (10%) patients were classified as having mild, 18 (22%) moderate, and 56 (68%) severe subclavian artery stenosis. In 7 (9%) patients with subclavian artery stenosis, angiography revealed occlusion of the IMA graft. 26 (32%) patients with severe subclavian artery stenosis underwent endovascular or surgical revasculararization of the subclavian artery. In this retrospective multicenter study, subclavian artery stenosis was a relevant finding in patients with an internal mammarian artery coronary bypass graft undergoing coronary angiography. The development of dedicated algorithms for screening and ischemia evaluation in affected individuals may improve treatment of this potentially underdiagnosed and undertreated condition.

The Polyscore of autonomic parameters predicts mortality and identifies low-risk individuals among diabetic survivors of acute myocardial infarction.

Survivors of an acute myocardial infarction with diabetes mellitus retain an increased mortality risk. Reliable assessment of individual risk is required for effective and cost-efficient medical care in these patients. The Polyscore is a previously established risk predictor consisting of seven autonomic tests derived from electrocardiogram, blood pressure, and respiration. The Polyscore allows classification of survivors of myocardial infarction in groups at low, intermediate and high mortality risk. The aim of this study was to investigate the prognostic value of the Polyscore in diabetic survivors of acute myocardial infarction, which may be impaired by the presence of diabetic autonomic neuropathy. Survivors of an acute myocardial infarction were included in a prospective cohort study during hospitalisation due to the index event at two university hospitals in Munich, Germany. The Polyscore was determined from simultaneous non-invasive 30-min recordings of electrocardiogram, continuous arterial blood pressure, and respiration which were performed in all participants. Patients were followed for 5 years. The primary and secondary outcomes were all-cause mortality and cardiac mortality. 184 of 941 enrolled patients (19.6%) suffered from diabetes mellitus. 5-year-mortality was higher in diabetic patients (15.2%) compared to non-diabetic patients (5.8%). A multivariable Cox regression model confirmed the Polyscore as a strong predictor of mortality in diabetic post-MI patients (intermediate risk: HR 6.56, 95% CI 1.61-26.78, p = 0.004, mortality 22.8%; high risk: HR 18.76, 95% CI 4.35-80.98, p < 0.001, mortality 68.8%). There was no interaction between diabetes mellitus and the Polyscore regarding mortality prediction (p = 0.775). Interestingly, in contrast to the groups at intermediate and high risk (73 patients, 39.7%), the Polyscore identified a majority of diabetic patients (111, 60.3%) with a low mortality risk, comparable to that of low-risk non-diabetic patients (3.6% and 2.1%, respectively, p = 0.339). Consistent results were observed for cardiac mortality. This analysis shows that the Polyscore predicts all-cause and cardiac mortality in diabetic survivors of acute myocardial infarction. Within these patients it identifies a large population not affected by the excess mortality associated with diabetes in this setting. Thus, the Polyscore may facilitate risk-adapted follow-up strategies in diabetic survivors of myocardial infarction.

Significant prevalence of peripheral artery disease in patients with disturbed wound healing following elective foot and ankle surgery: Results from the ABI-PRIORY (ABI as a PRedictor of Impaired wound healing after ORthopedic surgerY) trial.

Disturbed wound healing (DWH) following elective foot and ankle surgery is associated with a number of known risk factors. The purpose of this study was to determine if peripheral artery disease (PAD) is a potential risk factor that contributes to an increase in postoperative DWH. In a case-control study, we analyzed all patients undergoing elective foot and ankle surgery between January 1, 2014 and December 31, 2017 at two institutions and identified 51 patients with postoperative DWH. After matching with 51 control patients without DWH, all 102 patients were evaluated for PAD. The prevalence of PAD was significantly higher in the DWH group compared to the control group (41.2% vs 19.6%, p < 0.01). This difference was even more distinctive for patients with any abnormal ankle-brachial index (ABI) (51.0% vs 19.6%, p < 0.001). After adjustment for diabetes, hypertension, hypercholesterolemia, and smoking, any abnormal ABI or a history of PAD remained an independent risk factor for DWH (odds ratio 3.28; 95% CI 1.24-8.71). In this dual-center study, postoperative DWH was associated with significantly higher rates of PAD. These findings suggest that preoperative evaluation for PAD could be a helpful tool to identify patients at high risk for postoperative wound complications undergoing foot and ankle surgery. This trial is registered with drks.de, number DRKS00012580.

Impact of transcatheter mitral valve repair using MitraClip on right ventricular remodeling.

The potential of the MitraClip to prevent from right heart failure or to restore right ventricular (RV) function is still unclear. The aim of the present study was to analyze the impact of the MitraClip implantation on RV function and its association with clinical outcome. After MitraClip implantation patients underwent echocardiography follow-up scheduled between 3 and 6 months after the procedure in the present single-center registry. A total of 93 patients were included. Compared to baseline, RV function declined in 20%, was unchanged in 25% and improved in 55% of the patients. Factors associated with decline in RV performance were atrial fibrillation, decrease in left ventricular function and lack of reduction in pulmonary artery pressure. Patients who experienced worsening in RV function had a significantly lower survival after mean follow-up of 11 ± 7 months compared to those with preserved or improved RV function (15% vs. 83% vs. 83%; p log rank = 0.001). Furthermore, changes in TAPSE were found to be an independent predictor for all-cause mortality [HR 0.88 (0.77-0.99); p = 0.04]. The majority of patients suffering from severe MR benefited from MitraClip with respect to RV remodeling. However, 20% of the patients experienced a decline in RV function, which was associated with poor prognosis. Importantly, changes in RV function after MitraClip were identified as independent predictor for survival in contrast to baseline RV function and, therefore, should be implemented in follow-up routine for better outcome prediction.

Endovascular therapy of subclavian artery occlusive disease involving the vertebral artery origin.

Background: While the majority of subclavian artery (SA) lesions are localized in the proximal segment, the evidence in patients with medial SA disease involving the vertebral artery (VA) origin are scarce. PATIENTS AND METHODS: We retrospectively analyzed all patients who underwent percutaneous revascularization of the SA at our institution. RESULTS: A total of 196 patients were retrospectively analyzed. The majority of SA lesions (n = 163, 83 %) were located in the proximal segment, whereas 28 lesions (14 %) were located in the medial segment, and only 5 lesions (3 %) involved the distal segment. Procedural success was high for both stenosis (96 %) and occlusion (89 %) and did not differ depending on lesion location. Revascularization techniques in the medial segment included stenting of the SA only (13 patients), additional VA balloon-dilatation (6 patients), and bifurcation stenting of the SA and VA using T-stenting technique (9 patients). Outcome after a median of 12 months showed no significant differences in freedom from restenosis between proximal and medial lesions (90 % vs. 95 %; p = 0.67). CONCLUSIONS: Endovascular revascularization of SA disease with medial segments involving the VA origin required more complex techniques and showed long-term patency rates comparable to those in lesions located within the proximal SA.

Prognostic Impact of Left Atrial Function Following Transcatheter Mitral Valve Repair.

Background Left atrial ( LA ) function predicts clinical outcome in a variety of cardiovascular diseases. However, limited data are available in the setting of mitral regurgitation. The aim of the present study was to assess potential changes in LA ejection fraction (LAEF) and its prognostic value in patients following transcatheter mitral valve repair using the MitraClip. Methods and Results A total of 88 consecutive patients undergoing MitraClip implantation with complete echocardiography at baseline and follow-up between 3 and 6 months postprocedure were enrolled. LAEF improved in 58% of the population. Change in LAEF was associated with residual mitral regurgitation, residual transmitral gradient and left ventricular ejection fraction changes. Compared with their counterparts, patients with residual mitral regurgitation ≥grade 2 (change in LAEF, -6% [Interquartile [IQR], -9-1%] versus 4% [IQR, -5-15%]; P=0.05) and with residual transmitral gradient ≥5 mm Hg (change in LAEF, -2% [IQR, -9-9%] versus 5% [IQR, -4-16%]; P=0.03) showed a decline in LAEF , respectively. Furthermore, LAEF significantly correlated with changes in left ventricular ejection fraction ( r=0.40; P=0.001). With regards to clinical outcome, heart failure symptoms as assessed by New York Heart Association class were more severe in patients with worsened LAEF at follow-up. Finally, LAEF change was identified as an independent predictor of all-cause mortality (hazard ratio, 0.94; 95% CI, 0.90-0.98 [ P=0.008]). Conclusions The present analysis showed that changes in LA function in patients undergoing MitraClip implantation are associated with important measures including residual mitral regurgitation, elevated transmitral gradient, and left ventricular function. Importantly, LA function alterations represent a strong predictor for all-cause mortality.

Monocyte-platelet aggregates affect local inflammation in patients with acute myocardial infarction.

The local inflammatory response following acute myocardial infarction (AMI) is increasingly being recognized as a central factor determining infarct healing. Myocardial inflammation can be visualized in patients using fasting 18F-FDG PET/MRI. Although this novel biosignal correlates with long-term functional outcome, the corresponding cellular substrate is not well understood. Here we present a retrospective analysis of 29 patients with AMI who underwent revascularization, suggesting a connection between post infarction myocardial fasting 18F-FDG uptake, monocyte platelet aggregates (MPA), and P2Y12 inhibition. In detail, patients with high MPA percentages of CD14highCD16+ and CD14lowCD16+ monocytes had significantly higher local 18F-FDG uptake (SUVmean) in the infarcted myocardium than patients with low MPA (p < 0.05). Furthermore, there was an association of high MPA percentage in all monocyte subpopulations with deteriorating ΔLV-EF after 6 months (p < 0.01), which was confirmed in an extended analysis with additional 29 patients without PET/MRI data available. In this analysis, administration of Ticagrelor was associated with lower MPA percentage of CD14high monocyte subpopulations than Clopidogrel (p < 0.01) or Prasugrel (p < 0.05). Taken together, the findings from this analysis suggest that platelet aggregability may affect monocyte extravasation into the infarcted myocardium and influence long-term functional outcome. P2Y12 inhibition may intervene in this pathophysiologic process. Prospective studies are needed to further examine this important relationship.

Reverse Cardiac Remodeling After Transcatheter Treatment of Severe Tricuspid Regurgitation Using the Edge-to-Edge MitraClip Technique.

OBJECTIVES: In recent years, transcatheter treatment techniques for tricuspid regurgitation (TR) have rapidly evolved. Cardiac remodeling analysis beyond clinical outcome assessment following transcatheter tricuspid repair is still lacking. The aim of the present case series was to analyze cardiac remodeling after tricuspid valve repair using the edge-to-edge MitraClip technique. METHODS: Echocardiographic analysis was performed prior to MitraClip implantation and at 3-month and 6-month follow-up exams. RESULTS: Six consecutive patients undergoing MitraClip implantation between April 2017 and March 2018 at our institution were enrolled. During follow-up, TR reduction was durable in all patients, without recurrence of severe TR. Compared to baseline, right ventricular function improved in 5 out of 6 patients. Reduction in right ventricular area was observed in the majority of patients and reduction in right atrial volume was observed in all subjects. Patients also experienced beneficial left cardiac remodeling. CONCLUSION: The present series indicates that transcatheter treatment of severe TR using the edge-to-edge MitraClip technique can lead to reverse cardiac remodeling, which is not commonly seen in surgically treated patients.

Risk Prediction After Myocardial Infarction by Cyclic Variation of Heart Rate, a Surrogate of Sleep-Disordered Breathing Assessed From Holter ECGs.

AIMS: Sleep-disordered breathing (SDB) is common among cardiac patients, but its role as an independent risk predictor after myocardial infarction (MI) is unclear. SDB causes cyclic variation of heart rate (CVHR). The aim of this study was to score Holter ECGs of a large cohort of MI survivors for SDB-related CVHR to investigate its value for mortality prediction. METHODS: A total of 1590 survivors of acute MI in sinus rhythm were prospectively enrolled and followed for 5-year all-cause mortality. Heart rate (HR) tachograms were generated from nocturnal (00:00-06.00 am) segments of Holter ECGs, and the minutes with CVHR were quantified by a previously developed algorithm. According to a pre-specified cutpoint, SDB was assumed if CVHR was present during ≥72 min. RESULTS: Seventy-seven patients (4.8%) had flat HR tachograms which prohibited analysis for SDB. Of the remaining 1513 patients, 584 (38.6%) were classified as having SDB. Mortality rates in groups stratified according to ECG-derived SDB did not differ significantly. Taken as a continuous variable, low CVHR duration was associated with increased mortality.The mortality of patients with flat HR tachograms was significantly increased, even after adjustment for age, sex, LVEF, GRACE score and diabetes mellitus. Mortality prediction by a flat HR tachogram was also independent of heart rate variability (HRV), heart rate turbulence (HRT), and deceleration capacity (DC). CONCLUSION: In Holter ECG recordings of survivors of acute MI, signs suggestive of SDB were frequently present, but not associated with mortality. A flat nocturnal HR tachogram was a strong, independent predictor of 5-year all-cause mortality.

Cell-Surface Marker Signature for Enrichment of Ventricular Cardiomyocytes Derived from Human Embryonic Stem Cells.

To facilitate understanding of human cardiomyocyte (CM) subtype specification, and the study of ventricular CM biology in particular, we developed a broadly applicable strategy for enrichment of ventricular cardiomyocytes (VCMs) derived from human embryonic stem cells (hESCs). A bacterial artificial chromosome transgenic H9 hESC line in which GFP expression was driven by the human ventricular-specific myosin light chain 2 (MYL2) promoter was generated, and screened to identify cell-surface markers specific for MYL2-GFP-expressing VCMs. A CD77+/CD200- cell-surface signature facilitated isolation of >97% cardiac troponin I-positive cells from H9 hESC differentiation cultures, with 65% expressing MYL2-GFP. This study provides a tool for VCM enrichment when using some, but not all, human pluripotent stem cell lines. Tools generated in this study can be utilized toward understanding CM subtype specification, and enriching for VCMs for therapeutic applications.

Quantitative cardiovascular magnetic resonance: extracellular volume, native T1 and 18F-FDG PET/CMR imaging in patients after revascularized myocardial infarction and association with markers of myocardial damage and systemic inflammation.

BACKGROUND: Characterization of tissue integrity and inflammatory processes after acute myocardial infarction (AMI) using non-invasive imaging is predictive of patient outcome. Quantitative cardiovascular magnetic resonance (CMR) techniques such as native T1 and extracellular volume (ECV) mapping as well as 18F-FDG positron emission tomography (PET) imaging targeting inflammatory cell populations are gaining acceptance, but are often applied without assessing their quantitative potential. Using simultaneously acquired PET/CMR data from patients early after AMI, this study quantitatively compares these three imaging markers and investigates links to blood markers of myocardial injury and systemic inflammatory activity. METHODS: A total of 25 patients without microvascular obstruction were retrospectively recruited. All imaging was simultaneously performed 5 ± 1 days after revascularization following AMI on an integrated 3T PET/MRI scanner. Native and post-contrast T1 data were acquired using a modified Look-Locker inversion recovery (MOLLI) sequence, ECV maps were calculated using individually sampled hematocrit. 18F-FDG PET was executed after 1 day of dietary preparation, 12 h of fasting, and administration of heparin. ECV, 18F-FDG and native T1 data were compared mutually as well as to peak counts of peripheral blood markers (creatine kinase, creatine kinase-MB, troponin, leukocytes, monocytes) and infarct size. RESULTS: High intra-patient correlations of relative ECV, 18F-FDG PET and native T1 signal increases were observed in combination with no inter-patient correlation of maximum absolute values at the infarct center, suggesting well-colocalized but physiologically diverse processes begetting the respective image signals. Comparison of maximum image signals to markers of myocardial damage and systemic inflammation yielded highly significant correlations of ECV to peak creatine kinase-MB and overall infarct size as well as between native T1 and peak monocyte counts. CONCLUSIONS: Absolute native T1 values at the infarct core early after AMI can be linked to the systemic inflammatory response independent of infarct size. Absolute ECV at the infarct core is related to both infarct size and blood markers of myocardial damage.

Interplay of cell-cell contacts and RhoA/MRTF-A signaling regulates cardiomyocyte identity.

Cell-cell and cell-matrix interactions guide organ development and homeostasis by controlling lineage specification and maintenance, but the underlying molecular principles are largely unknown. Here, we show that in human developing cardiomyocytes cell-cell contacts at the intercalated disk connect to remodeling of the actin cytoskeleton by regulating the RhoA-ROCK signaling to maintain an active MRTF/SRF transcriptional program essential for cardiomyocyte identity. Genetic perturbation of this mechanosensory pathway activates an ectopic fat gene program during cardiomyocyte differentiation, which ultimately primes the cells to switch to the brown/beige adipocyte lineage in response to adipogenesis-inducing signals. We also demonstrate by in vivo fate mapping and clonal analysis of cardiac progenitors that cardiac fat and a subset of cardiac muscle arise from a common precursor expressing Isl1 and Wt1 during heart development, suggesting related mechanisms of determination between the two lineages.

Diagnosis of a rare cardiac human herpesvirus-8 positive B-cell lymphoma manifestation: a case report of a transoesophageal echocardiography-guided trans-septal catheter biopsy.

INTRODUCTION: Human herpesvirus-8-associated B-cell lymphoma is a common disease entity in immunocompromised individuals, particularly in patients with chronic HIV-infection or AIDS. However, cardiac manifestations are extremely rare. Tissue for histopathology of left cardiac tumours is most commonly obtained by open surgery. CASE PRESENTATION: In this report, we present a case of a solitary left atrial manifestation of an HHV8+ B-cell lymphoma in a 59-year-old patient presenting with B symptoms and a cardiac mass on echocardiography. Due to the high operative risk of the patient, a transcatheter/trans-septal biopsy was performed to establish the diagnosis. DISCUSSION: In the era of routine trans-septal catheter interventions, this approach may represent a straight-forward, minimally invasive alternative for patients at high risk for surgery.

Prospective Evaluation of 18F-Fluorodeoxyglucose Uptake in Postischemic Myocardium by Simultaneous Positron Emission Tomography/Magnetic Resonance Imaging as a Prognostic Marker of Functional Outcome.

BACKGROUND: The immune system orchestrates the repair of infarcted myocardium. Imaging of the cellular inflammatory response by (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/magnetic resonance imaging in the heart has been demonstrated in preclinical and clinical studies. However, the clinical relevance of post-MI (18)F-FDG uptake in the heart has not been elucidated. The objective of this study was to explore the value of (18)F-FDG positron emission tomography/magnetic resonance imaging in patients after acute myocardial infarction as a biosignal for left ventricular functional outcome. METHODS AND RESULTS: We prospectively enrolled 49 patients with ST-segment-elevation myocardial infarction and performed (18)F-FDG positron emission tomography/magnetic resonance imaging 5 days after percutaneous coronary intervention and follow-up cardiac magnetic resonance imaging after 6 to 9 months. In a subset of patients, (99m)Tc-sestamibi single-photon emission computed tomography was performed with tracer injection before revascularization. Cellular innate immune response was analyzed at multiple time points. Segmental comparison of (18)F-FDG-uptake and late gadolinium enhancement showed substantial overlap (κ=0.66), whereas quantitative analysis demonstrated that (18)F-FDG extent exceeded late gadolinium enhancement extent (33.2±16.2% left ventricular myocardium versus 20.4±10.6% left ventricular myocardium, P<0.0001) and corresponded to the area at risk (r=0.87, P<0.0001). The peripheral blood count of CD14(high)/CD16(+) monocytes correlated with the infarction size and (18)F-FDG signal extent (r=0.53, P<0.002 and r=0.42, P<0.02, respectively). (18)F-FDG uptake in the infarcted myocardium was highest in areas with transmural scar, and the standardized uptake valuemean was associated with left ventricular functional outcome independent of infarct size (Δ ejection fraction: P<0.04, Δ end-diastolic volume: P<0.02, Δ end-systolic volume: P<0.005). CONCLUSIONS: In this study, the intensity of (18)F-FDG uptake in the myocardium after acute myocardial infarction correlated inversely with functional outcome at 6 months. Thus, (18)F-FDG uptake in infarcted myocardium may represent a novel biosignal of myocardial injury.

Combination of factor Xa inhibition and antiplatelet therapy after stenting in patients with iliofemoral post-thrombotic venous obstruction.

OBJECTIVES: Studies addressing optimal postprocedural pharmacological management after endovascular stenting of iliofemoral post-thrombotic venous obstruction are lacking. We report our early clinical experience with a combination of rivaroxaban and clopidogrel in patients after iliofemoral post-thrombotic venous obstruction stenting. METHODS: Demographic, procedural, and follow-up data of nine patients (seven women; mean age of 32 ± 11 years) undergoing 10 procedures for iliofemoral post-thrombotic venous obstruction performed between August 2012 and January 2014 were retrospectively reviewed. After endovascular intervention, all patients were administered 20 mg rivaroxaban once daily (s.i.d.) and 75 mg clopidogrel s.i.d. or every second day depending on the individual drug responsiveness for at least six months. The adenosine diphosphate-induced platelet aggregation (platelet aggregation, in aggregation units × min) was assessed on a Multiplate analyzer. Patency was verified venographically at procedure end and was evaluated with duplex ultrasound in regular follow-ups. RESULTS: Iliofemoral venous flow was successfully re-established by percutaneous endovascular angioplasty and stent implantation in nine left-sided and one bilateral iliofemoral post-thrombotic venous obstruction. Under dual treatment strategy of rivaroxaban and clopidogrel with platelet aggregation control (median (range): 285 aggregation units × min (192; 402)), none of the patients experienced restenosis or stent thrombosis, respectively. After a median follow-up of 14 months (range: 6-26 months), the primary patency rate was 100% and no in-stent restenosis, stent occlusion or relevant minor or major bleeding occurred. CONCLUSION: Combined factor Xa inhibition and tailored antiplatelet therapy after stenting of iliofemoral post-thrombotic venous obstruction were safe and performed favorably in terms of vessel patency.

Direct nkx2-5 transcriptional repression of isl1 controls cardiomyocyte subtype identity.

During cardiogenesis, most myocytes arise from cardiac progenitors expressing the transcription factors Isl1 and Nkx2-5. Here, we show that a direct repression of Isl1 by Nkx2-5 is necessary for proper development of the ventricular myocardial lineage. Overexpression of Nkx2-5 in mouse embryonic stem cells (ESCs) delayed specification of cardiac progenitors and inhibited expression of Isl1 and its downstream targets in Isl1(+) precursors. Embryos deficient for Nkx2-5 in the Isl1(+) lineage failed to downregulate Isl1 protein in cardiomyocytes of the heart tube. We demonstrated that Nkx2-5 directly binds to an Isl1 enhancer and represses Isl1 transcriptional activity. Furthermore, we showed that overexpression of Isl1 does not prevent cardiac differentiation of ESCs and in Xenopus laevis embryos. Instead, it leads to enhanced specification of cardiac progenitors, earlier cardiac differentiation, and increased cardiomyocyte number. Functional and molecular characterization of Isl1-overexpressing cardiomyocytes revealed higher beating frequencies in both ESC-derived contracting areas and Xenopus Isl1-gain-of-function hearts, which associated with upregulation of nodal-specific genes and downregulation of transcripts of working myocardium. Immunocytochemistry of cardiomyocyte lineage-specific markers demonstrated a reduction of ventricular cells and an increase of cells expressing the pacemaker channel Hcn4. Finally, optical action potential imaging of single cardiomyocytes combined with pharmacological approaches proved that Isl1 overexpression in ESCs resulted in normally electrophysiologically functional cells, highly enriched in the nodal subtype at the expense of the ventricular lineage. Our findings provide an Isl1/Nkx2-5-mediated mechanism that coordinately regulates the specification of cardiac progenitors toward the different myocardial lineages and ensures proper acquisition of myocyte subtype identity.