ONE MARROW CELL THERAPY IS currently being investigated as a new therapeutic option for patients with ischemic heart disease. The goal of this treatment is to improve myocardial perfusion and contractile performance through administration of therapeutic cells into ischemically damaged myocardium. The majority of clinical studies conducted so far investigated whether intracoronary bone marrow cell infusion could enhance functional recovery after acute myocardial infarction. 1-3 Animal model studies, however, suggested that bone marrow cell therapy may also improve myocardial perfusion and increase left ventricular (LV) function in chronic ischemia. 4,5 A number of nonrandomized clinical studies indicated the safety and feasibility of intramyocardial bone marrow cell injection. 6-9 Moreover, a beneficial effect on myocardial perfusion and LV function was presumed. Until now, only 2 smallsized randomized controlled studies assessed the effect of bone marrow cell injection in patients with chronic myocardial ischemia. 10,11 Since the results of these 2 studies were discrepant, the beneficial effect of this treatment mo-Author Affiliations are listed at the end of this article.

Stem cell therapy has emerged as a potential therapeutic option for cell death-related heart diseases. Preclinical and a number of early phase human studies suggested that cell therapy may augment perfusion and increase myocardial contractility. The rapid translation into clinical trials has left many issues unresolved, and emphasizes the need for specific techniques to visualize the mechanisms involved. Furthermore, the clinical efficacy of cell therapy remains to be proven. Imaging allows for in vivo tracking of cells and can provide a better understanding in the evaluation of the functional effects of cell-based therapies. In this review, a summary of the most promising imaging techniques for cell tracking is provided. Among these are direct labeling of cells with super-paramagnetic agents, radionuclides, and the use of reporter genes for imaging of transplanted cells. In addition, a comprehensive summary is provided of the currently available studies investigating a cell therapy-related effect on left ventricular function, myocardial perfusion, scar tissue, and myocardial viability.

IMPORTANCESmart technology via smartphone-compatible devices might improve blood pressure (BP) regulation in patients after myocardial infarction. OBJECTIVES To investigate whether smart technology in clinical practice can improve BP regulation and to evaluate the feasibility of such an intervention. DESIGN, SETTING, AND PARTICIPANTS This study was an investigator-initiated, single-center, nonblinded, feasibility, randomized clinical trial conducted at the Department of Cardiology of the Leiden University Medical Center between May 2016 and December 2018. Two hundred patients, who were admitted with either ST-segment elevation myocardial infarction or non-ST-segment acute coronary syndrome, were randomized in a 1:1 fashion between follow-up groups using smart technology and regular care. Statistical analysis was performed from January 2019 to March 2019. INTERVENTIONSFor patients randomized to regular care, 4 physical outpatient clinic visits were scheduled in the year following the initial event. In the intervention group, patients were given 4 smartphone-compatible devices (weight scale, BP monitor, rhythm monitor, and step counter). In addition, 2 in-person outpatient clinic visits were replaced by electronic visits. MAIN OUTCOMES AND MEASURESThe primary outcome was BP control. Secondary outcomes, as a parameter of feasibility, included patient satisfaction (general questionnaire and smart technology-specific questionnaire), measurement adherence, all-cause mortality, and hospitalizations for nonfatal adverse cardiac events. RESULTSIn total, 200 patients (median age, 59.7 years [interquartile range, 52.9-65.6 years]; 156 men [78%]) were included, of whom 100 were randomized to the intervention group and 100 to the control group. After 1 year, 79% of patients in the intervention group had controlled BP vs 76% of patients in the control group (P = .64). General satisfaction with care was the same between groups (mean [SD] scores, 82.6 [14.1] vs 82.0 [15.1]; P = .88). The all-cause mortality rate was 2% in both groups (P > .99). A total of 20 hospitalizations for nonfatal adverse cardiac events occurred (8 in the intervention group and 12 in the control group). Of all patients, 32% sent in measurements each week, with 63% sending data for more than 80% of the weeks they participated in the trial. In the intervention group only, 90.3% of patients were satisfied with the smart technology intervention. CONCLUSIONS AND RELEVANCEThese findings suggest that smart technology yields similar percentages of patients with regulated BP compared with the standard of care. Such an intervention (continued)

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Human mesenchymal stem cells are able to repair conduction block in cardiomyocyte cultures, probably through connexin-mediated coupling.