Platelets and cardiac arrhythmia

\u3cp\u3eSudden cardiac death (SCD) remains one of the most prevalent modes of death in industrialized countries, and myocardial ischemia due to thrombotic coronary occlusion is its primary cause. The role of platelets in the occurrence of SCD extends beyond coronary flow impairment by clot formation. Here we review the substances released by platelets during clot formation and their arrhythmic properties. Platelet products are released from three types of platelet granules: dense core granules, alpha-granules, and platelet lysosomes. The physiologic properties of dense granule products are of special interest as a potential source of arrhythmic substances. They are released readily upon activation and contain high concentrations of serotonin, histamine, purines, pyrimidines, and ions such as calcium and magnesium. Potential arrhythmic mechanisms of these substances, e.g., serotonin and high energy phosphates, include induction of coronary constriction, calcium overloading, and induction of delayed after-depolarizations. Alpha-granules produce thromboxanes and other arachidonic-acid products with many potential arrhythmic effects mediated by interference with cardiac sodium, calcium, and potassium channels. Alpha-granules also contain hundreds of proteins that could potentially serve as ligands to receptors on cardiomyocytes. Lysosomal products probably do not have an important arrhythmic effect. Platelet products and ischemia can induce coronary permeability, thereby enhancing interaction with surrounding cardiomyocytes. Antiplatelet therapy is known to improve survival after myocardial infarction. Although an important part of this effect results from prevention of coronary clot formation, there is evidence to suggest that antiplatelet therapy also induces anti-arrhythmic effects during ischemia by preventing the release of platelet activation products.\u3c/p\u3

Initiation of ventricular tachycardia by interruption of pacemaker-mediated tachycardia in a patient with a dual-chamber implantable cardioverter defibrillator

\u3cp\u3eA 74-year-old man with a dual-chamber implantable cardioverter defibrillator implanted 3 years before experienced multiple ventricular tachycardias (VTs). All episodes were initiated by pacemaker-mediated tachycardia (PMT) that was either stopped by atrial undersensing or the tachycardia termination algorithm of the device. After the termination of PMT, two rapid ventricular paced beats, the first initiated by artificial triggering and the second due to retrograde conduction of the first one, initiated VT that was successfully terminated by antitachycardia pacing or a direct current shock of the device. All episodes revealed this pattern of initiation with a short-long-short ventricular sequence inducing VT.\u3c/p\u3

Improving the efficiency of the cardiac catheterization laboratories through understanding the stochastic behavior of the scheduled procedures

\u3cp\u3eBACKGROUND: In this study, we sought to analyze the stochastic behavior of Catherization Laboratories (Cath Labs) procedures in our institution. Statistical models may help to improve estimated case durations to support management in the cost-effective use of expensive surgical resources.\u3c/p\u3e\u3cp\u3eMETHODS: We retrospectively analyzed all the procedures performed in the Cath Labs in 2012. The duration of procedures is strictly positive (larger than zero) and has mostly a large minimum duration. Because of the strictly positive character of the Cath Lab procedures, a fit of a lognormal model may be desirable. Having a minimum duration requires an estimate of the threshold (shift) parameter of the lognormal model. Therefore, the 3-parameter lognormal model is interesting. To avoid heterogeneous groups of observations, we tested every group-cardiologist-procedure combination for the normal, 2- and 3-parameter lognormal distribution.\u3c/p\u3e\u3cp\u3eRESULTS: The total number of elective and emergency procedures performed was 6,393 (8,186 h). The final analysis included 6,135 procedures (7,779 h). Electrophysiology (intervention) procedures fit the 3-parameter lognormal model 86.1% (80.1%). Using Friedman test statistics, we conclude that the 3-parameter lognormal model is superior to the 2-parameter lognormal model. Furthermore, the 2-parameter lognormal is superior to the normal model.\u3c/p\u3e\u3cp\u3eCONCLUSIONS: Cath Lab procedures are well-modelled by lognormal models. This information helps to improve and to refine Cath Lab schedules and hence their efficient use.\u3c/p\u3

Developmental and genetic aspects of atrial fibrillation

\u3cp\u3eAtrial fibrillation (AF) is the most common cardiac arrhythmia encountered in clinical practice. The abnormal rhythm is associated not only with a variety of symptoms, such as palpitations, dizziness, or shortness of breath, but also with increased risk of stroke, heart failure, and mortality. A genetic predisposition is suggested by the fact that the relative risk for the development of AF is estimated at 85% in individuals with at least one parent with a history of AF. Current therapeutic strategies include control of rate or rhythm with medication and catheter ablation procedures. Especially in the pathophysiology of paroxysmal AF, ectopic electrical activity originating in the myocardial sleeves surrounding the pulmonary veins is considered causal. In these cases, ablation is applied to isolate the pulmonary venous myocardium from the remainder of the left atrial myocardium. Other recent evidence has shown that genetic and developmental defects can be involved in the development of AF. In this review, it is our aim to discuss the possible underlying causes of AF from a combined genetic and cardiac developmental view.\u3c/p\u3

Cardiac structure and function before and after bariatric surgery:a clinical overview

\u3cp\u3eObesity, defined as a body mass index of ≥30 kg/m2 , is the most common chronic metabolic disease worldwide and its prevalence has been strongly increasing. Obesity has deleterious effects on cardiac function. The purpose of this review is to evaluate the effects of obesity and excessive weight loss due to bariatric surgery on cardiac function, structural changes and haemodynamic responses of both the left and right ventricle.\u3c/p\u3

Force-interval relationships of the heart measured with photoplethysmography during atrial fibrillation

\u3cp\u3eForce-interval relationships (FIRs) of the heart represent the relationships between inter-beat intervals (IBIs) and strength of the ventricular contractions. These relationships are typically measured invasively and are altered from normal in heart failure (HF). An unobtrusive and continuous measurement of FIRs could be beneficial when HF and atrial fibrillation (AF) coexist in order to understand if AF causes progression of HF. We hypothesize that FIRs could be assessed during AF with IBIs and hemodynamic changes captured unobtrusively by photo-plethysmography (PPG) at the wrist. FIRs were assessed by using Spearman's rank correlation between the pulse onset change in the PPG waveform and either the preceding or pre-preceding IBIs (r \u3csub\u3epre\u3c/sub\u3e\ and r \u3csub\u3epre-pre\u3c/sub\u3e) in 5-minute segments. 32 patients (14 continuous AF, 18 no AF) were measured during the night with PPG and electrocardiography as a reference. The mean and standard deviation of r \u3csub\u3epre\u3c/sub\u3e were -0.25± 0.08 and 0.05± 0.12(p < 0.0001), and of r \u3csub\u3epre-pre\u3c/sub\u3e} 0.60± 0.09 and 0.16± 0.14 (p < 0.0001), during AF and sinus rhythm, respectively. Areas under the Receiver Operating Characteristics curve were 0.987 and 0.998, respectively. Thus, during AF the IBIs correlate with the beat-to-beat changes of blood volume measured with PPG, likely to indicate that FIRs can be measured unobtrusively with the PPG signal. \u3c/p\u3

Reduced number of cardiovascular events and increased cost-effectiveness by genotype-guided antiplatelet therapy in patients undergoing percutaneous coronary interventions in the Netherlands

AIM: \u3cbr/\u3e\u3cbr/\u3eThis study explores clinical outcome in cytochrome P450 2C19 (CYP2C19)-related poor metaboliser patients treated with either clopidogrel or prasugrel after percutaneous coronary intervention (PCI) and investigates whether this could be cost-effective.\u3cbr/\u3e\u3cbr/\u3eMETHODS AND RESULTS: \u3cbr/\u3e\u3cbr/\u3eThis single-centre, observational study included 3260 patients scheduled for elective PCI between October 2010 and June 2013 and followed for adverse cardiovascular events until October 2014. Post PCI, CYP2C19 poor metaboliser patients were treated with clopidogrel or prasugrel, in addition to aspirin. In total, 32 poor metabolisers were treated with clopidogrel and 41 with prasugrel. The number of adverse cardiovascular events, defined as death from cardiovascular cause, myocardial infarction, stent thrombosis, every second visit to the catheterisation room for re-PCI in the same artery, or stroke, within 1.5 years of PCI, was significantly higher in the CYP2C19 poor metaboliser group treated with clopidogrel (n = 10, 31 %) compared with the poor metaboliser group treated with prasugrel (n = 2, 5 %) (p = 0.003). Costs per gained quality-adjusted life years (QALY) were estimated, showing that genotype-guided post-PCI treatment with prasugrel could be cost-effective with less than € 10,000 per gained QALY.\u3cbr/\u3e\u3cbr/\u3eCONCLUSION: \u3cbr/\u3e\u3cbr/\u3eThis study provides evidence that for CYP2C19-related poor metabolisers prasugrel may be more effective than clopidogrel to prevent major adverse cardiovascular events after PCI and this approach could be cost-effective.\u3cbr/\u3