Coupled FEA Model with Continuum Damage Mechanics for the Degradation of Polymer-based coatings on Drug-Eluting Stents.

Drug-Eluting Stents (DES) are commonly used in Coronary angioplasty procedures to reduce the phenomenon of restenosis. Numerical simulations are proven to be a useful tool to the Bioengineering community in computing the mechanical performance of stents. BioCoStent is a research project aiming to develop a DES with retinoic acid (RA) coating, in the frame of which FEAC is responsible for the in silico numerical simulation of the coating's degradation in terms of Finite Element Analysis (FEA). The coatings under study are poly(lactic-co-glycolic acid) (PLGA) and polylactide (PLA). The FEA is based on the Continuum Damage Mechanics (CDM) theory and considers a mechanistic model for polymer bulk degradation of the coatings. The degradation algorithm is implemented on the NX Nastran solver through a user-defined material UMAT subroutine. This paper describes the developed numerical model to compute the degradation of biodegradable coatings on DES. The transient numerical model provides useful insight into the critical areas with regards to the scalar damage of the coatings. The FEA results present a complete degradation of polymers after several weeks.

FEA of Drug-Eluting Stents and Sensitivity Analysis of a Continuum Damage Model for the Degradation of PLGA Coating.

Drug-Eluting Stents (DES) are commonly used in coronary angioplasty operations as a solution against artery stenosis and restenosis. Computational Bioengineering allows for the in-silico analysis of their performance. The scope of this work is to develop a DES Digital Twin, focusing on the mechanical integrity of its biodegradable coating throughout the operational lifecycle. The implementation leverages the Finite Element Method (FEM) to compute the developed mechanical stress field on the DES during the inflation/deflation stage, followed by the degradation of the polymer-based coating. The simulation of the degradation process is based on a Continuum Damage Mechanics (CDM) model that considers bulk degradation. The CDM algorithm is implemented on the NX Nastran solver through a user-defined material (UMAT) subroutine. For benchmarking purposes and to compare with the baseline design of the BioCoStent project, this conceptual study implements an alternative stent design, to study the effect of the geometry on the developed stresses. Additionally, the effect of the degradation rate on the polymer-based coating's lifecycle is studied via sensitivity analysis.

Monitoring operating room performance with control charts: findings from a Greek public hospital.

OBJECTIVE: To describe the development and demonstrate the use of a statistical framework based on statistical quality control (SQC) in order to monitor the performance of operating rooms (ORs). DESIGN: Data related to scheduled surgical operations have been collected from the information system of an existing Greek hospital. The data that contain the anesthesia and operation start and completion times of the operations carried out in the 14 ORs of the hospital are analyzed using control p-charts and hypotheses testing. The results obtained provide crucial information to health-care managers. SETTING: A large Greek public hospital. PARTICIPANTS: Real-world data captured on daily basis from January 2015 to November 2017. INTERVENTION: The proportion of the idle time of an OR over its total available time is proposed as an OR key performance index. We present two directions of data monitoring and analysis: one that uses control p-charts and a second based on hypotheses testing. The improved Laney's p΄-chart and the Laney's approach for cross-sectional data are employed in order to overcome overdispersion that affects OR idle time data. RESULTS: The proposed methodology allows hospital management (i) to monitor the percentage of the idle time of an operating room through time and (ii) to identify the ORs that demonstrate exceptionally high or low percentage of idle time at a given period of time. CONCLUSION: SQC charts are simple, yet powerful tools that may support the hospital management in monitoring OR performance and decision-making. The development of a dedicated management information system that automatically captures the required data and constructs the corresponding control charts would support effectively managerial decision-making.

Calcium Handling and Arrhythmogenesis.

Intracellular calcium homeostasis plays a fundamental role in the electric and mechanical function of the heart by modulating action potential pattern and duration, by linking cell membrane depolarization to myocardial contraction and by regulating cardiac automaticity. Abnormalities of intracellular calcium regulation disrupt the electrophysiological properties of the heart and create an arrhythmogenic milieu, which promotes atrial and ventricular arrhythmogenesis and impairs cardiac automaticity and atrioventricular conduction. In this brief review, we summarize the basic genetic, molecular and electrophysiological mechanisms linking inherited or acquired intracellular Ca(2+) dysregulation to arrhythmogenesis.

Successful surgical repair of mitral valve prolapse endocarditis: a case report and review of the current literature.

We present the case of a 42-year-old man with mitral valve prolapse (MVP) and infective endocarditis. He was referred to our hospital by his family physician for the evaluation of a cardiac murmur. A detailed medical history revealed that he had been feeling fatigue with occasional episodes of slight fever during the last two months. Echocardiography revealed MVP with a sizeable vegetation and severe mitral insufficiency. Serial blood cultures were positive for Streptococcus viridans, highly penicillin susceptible. He was put on appropriate antimicrobial therapy, but both the vegetation and the concomitant mitral insufficiency persisted after otherwise successful medical therapy. Thus, the patient underwent surgical vegetectomy with mitral valve repair. He had an uneventful postoperative course and remains free of disease at the 12-month follow up. Our case report reinforces the value of early diagnosis in the presence of a high clinical suspicion of MVP endocarditis. An extended clinical workup, including serial detailed echocardiography studies, is mandatory in such a patient. Medical treatment of infective endocarditis in the setting of MVP is often successful. However, cardiac surgical intervention plays an important role in the treatment of intracardiac complications. Mitral valve repair in the context of a healed and stable infective endocarditis is the treatment of choice.

Clinical outcome and angiographic results with novel polysulfone polymer coating paclitaxel eluting stent in real-world clinical practice: a clinical centre registry.

BACKGROUND: The Intek-Apollo stent (Switzerland) employs a polysulfone polymer coating which has demonstrated low interaction with blood and high thrombo-resistance. The aim of this study was to assess the clinical and angiographic outcomes after Intek-Apollo stent utilisation in a real-world setting. MATERIAL/METHODS: A total of 130 patients (77.7% males) were enrolled with 174 lesions in native coronary arteries (92.4%), saphenous vein grafts (7.5%) and in-stent restenosis (6.3%). Indications for stenting were stable coronary artery disease (CAD) 52.3%, acute coronary syndrome (ACS) 37.7% and STEMI 10%. Clinical follow-up and coronary angiography (after symptoms occurrence or positive stress test) was performed at 6 and 12 months.The primary end points were target lesion revascularization (TLR) and target vessel revascularization (TVR), while secondary end points were major adverse cardiac events (MACE) during the follow-up period. RESULTS: The mean age of patients included was 61.62±11.13 years. Complex lesions treatment (ostial, bifurcation) reached 13.7%. Mean stenosis diameter was 83.52±10.5%. Reference vessel diameter was 2.85±0.39 mm with a mean lesion length of 14.66±4.5mm. Average stent size was 2.93±0.39mm × 16.6±4.73 mm. At 15±3 months, primary events included TLR (4.6%), TVR (4.6%) and MACE (2.3%). There was 1one myocardial infarction and no cardiac death). No incidence of early or late stent thrombosis was demonstrated. CONCLUSIONS: Intek-Apollo stent implantation is safe and efficient in a real world population. The unique properties of polysulfone polymer coating can effectively protect from late stent thrombosis and lead to reduced rates of TLR, TVR and MACE.

Sensitivity and specificity of sodium channel blocking test in the diagnosis of Brugada syndrome.

The ECG features of Brugada syndrome are dynamic and frequently concealed. Sodium channels blockers are widely used to unmask the Brugada electrocardiographic (ECG) pattern. The sensitivity and specificity of I(Na) channel blocking test varies significantly. A negative I(Na) blocking test does not exclude the presence of a SCN5A mutation, which is responsible for the phenotype of Brugada syndrome. Herein, we describe the case of a 65-years-old asymptomatic male who underwent a I(Na) channel blocking test, seven years ago due to a type 2 ECG pattern (saddleback configuration) which failed to induce the diagnostic type 1 ECG pattern. Diagnostic considerations at a molecular level and their clinical relevance are being discussed.

Potential-guided versus anatomic-guided approach for slow pathway ablation of the common type atrioventricular nodal reentry tachycardia: a randomized study.

OBJECTIVE: The present study aimed to compare the effectiveness and safety of the potential- and the anatomic-guided approach for slow pathway ablation in patients with recurrent episodes of symptomatic common type atrioventricular (AV) nodal reentrant tachycardia. METHODS: Two hundred and twenty-eight patients were randomly assigned to undergo either a potential- (n=114, 47% men, mean age 52.85 +/- 14.04 years) or an anatomic-guided approach (n=114, 50% men, mean age 52.45 +/- 14.46 years) for radiofrequency ablation of the slow pathway.The mean duration of the follow-up period was 26.7 +/- 7.9 and 24.8 +/- 7.6 months in the potential- and anatomic- guided approach, respectively (P > 0.05). RESULTS: The success rate for slow pathway ablation was 100% in both ablative methods.The mean duration of atrial electrograms at the successful ablation sites of the potential- and the anatomic-guided approaches was 69 +/- 14 msec and 57 +/- 10 msec, respectively (P = 0.001).There were no significant differences between the potential- and the anatomic-guided approach regarding the duration of the procedure (121.13 +/- 56.83 vs. 109.93 +/- 57.12 min, P = 0.139), the duration of fluoroscopic exposure (6.12 +/- 3.32 vs. 6.64 +/- 3.33 min, P = 0.239) or the mean number of radiofrequency applications delivered (3.96 +/- 2.77 vs. 4.33 +/- 2.73, P = 0.311). Residual dual AV nodal pathway following successful ablation was observed in 9.6% of patients who underwent the potential-guided approach and in 23.7% of patients who underwent the anatomic method (P = 0.004). During followup, arrhythmia recurrence was observed in four patients (1.8%), two in each group (P > 0.05). CONCLUSIONS: The efficacy and safety of the slow pathway ablation is very high using either the potential- or the anatomic-guided approach.

Wide QRS complex supraventricular tachycardia with negative precordial concordance.

The authors describe the case of a 49-year-old man who experienced an episode of palpitations and dizziness. The results of 24-hour Holter monitoring demonstrated an episode of wide QRS complex regular tachycardia. During the electrophysiological study, a wide QRS complex tachycardia with negative precordial concordance was induced. A diagnosis of orthodromic atrioventricular re-entrant tachycardia involving a left lateral accessory pathway with left bundle branch aberration was made. This case represents a rare exception to the rule that negative precordial QRS concordance is diagnostic of ventricular tachycardia.

Predictors of atrial fibrillation recurrence in patients with long-lasting atrial fibrillation.

BACKGROUND: Limited data are available on the predictors of atrial fibrillation (AF) recurrence in patients with chronic AF. OBJECTIVES: To evaluate potential clinical, echocardiographic and electrophysiological predictors of AF recurrence, after internal cardioversion for long-lasting AF. METHODS: A total of 99 consecutive patients (63 men and 36 women, mean age 63.33+/-9.27 years) with long-standing AF (52.42+/-72.02 months) underwent internal cardioversion with a catheter that consisted of two defibrillating coils. Shocks were delivered according to a step-up protocol. Clinical follow-up and electrocardiographic recordings were performed on a monthly basis for a 12-month period or whenever patients experienced symptoms suggestive of recurrent AF. RESULTS: Ninety-three patients (93.94%) underwent a successful uncomplicated cardioversion, with a mean atrial defibrillation threshold of 10.69+/-6.76 J. Immediate reinitiation of AF was observed in 15 patients (15.78%) of whom a repeated cardioversion restored sinus rhythm in 13 cases. Early recurrence of AF (within one week) was observed in 12 of 93 patients (12.90%). At the end of the 12-month follow-up period, during which seven patients were lost, 42 of the 86 remaining patients (48.84%) were still in sinus rhythm. Multivariate regression analysis showed that left atrial diameter (OR 1.126, 95% CI 1.015 to 1.249; P=0.025) and mitral A wave velocity (OR 0.972, 95% CI 0.945 to 0.999; P=0.044) were significant and independent predictors of AF recurrence, whereas age, left ventricular ejection fraction and AF cycle length were not predictive of arrhythmia recurrence. CONCLUSION: The present study showed that the left atrial diameter and mitral A wave velocity are the only variables associated with AF recurrence after successful cardioversion.

Determinants of plasma NT-pro-BNP levels in patients with atrial fibrillation and preserved left ventricular ejection fraction.

OBJECTIVES: The present study aimed to investigate the clinical and echocardiographic determinants of plasma NT-pro-BNP levels in patients with atrial fibrillation (AF) and preserved left ventricular ejection fraction (LVEF). METHODS: NT-pro-BNP levels were measured in 45 patients with paroxysmal AF, 41 patients with permanent AF and 48 controls. RESULTS: NT-pro-BNP levels were found significantly elevated in patients with paroxysmal (215+/-815 pg/ml) and permanent AF (1,086+/-835 pg/ml) in relation to control population (86.3+/-77.9 pg/ml) (P<0.001). According to the univariate linear regression analysis, age, hypertension, beta-blocker use, left atrial diameter (LAD), LVEF and AF status (paroxysmal or permanent or both) were significantly associated with NT-pro-BNP levels (P<0.05). In multiple linear regression analysis, LVEF (B coefficient: -53.030; CI: -95.738 to -10.322; P: 0.015) and LAD (B coefficient: 285.858; CI: 23.731-547.986; P: 0.033) were significant and independent determinants of NT-pro-BNP levels. CONCLUSIONS: Plasma NT-pro-BNP levels were significantly higher in patients with paroxysmal and permanent AF compared to those with sinus rhythm in the setting of preserved left ventricular systolic function. LVEF and LAD were independent predictors of NT-pro-BNP levels.

Histological recognition and classification of the atrioventricular node artery variants: a new approach.

BACKGROUND: There is a controversy in the literature concerning the origin, course, and distribution of the atrioventricular (AV) node artery. METHODS: Postmortem coronary angiography, dissection, and microscopic examination were performed in 100 human hearts specimens, providing anatomical, histological, and postmortem angiographic features of the AV node artery. RESULTS: Two anatomical types of AV node artery, depending on its length (long-short), were found. "Long-length" (LL) AV node artery supplied with blood almost all the AV conducting tissue in 72 cases. It consisted of a horizontal and descending part ending in two branches. "Short-length" (SL) AV node artery had only a horizontal part, perfusing exclusively the AV node and several times the nonpenetrating main bundle of His. In 67 of 100 cases, the AV arteries were arising from the right coronary artery, distal to the posterior descending (PD) artery. The AV node artery never originated from the PD artery. In 54 of 100 cases, it passed under the coronary sinus (CS) and in the remaining 46 it passed underneath the right atrium endocardium. CONCLUSIONS: The above-described postmortem coronary angiographic findings are essential for interventional cardiologists and cardiac surgeons. Damage to the LL or SL type of AV node artery may cause severe or limited AV conduction abnormalities, respectively. Furthermore, the course of AV node artery under the CS makes it susceptible to injuries provoked by diagnostic or therapeutic procedures involving the CS area.

Clinical characteristics of patients with drug-induced QT interval prolongation and torsade de pointes: identification of risk factors.

The present study aimed to investigate the causative medications and underlying risk factors that predispose to drug-induced QT interval prolongation. Twenty-one patients with drug-induced long QT (90% females, mean age 64.3 +/- 14.1 years) were included in the study. Transthoracic echocardiography as well as continuous or ambulatory 48-h electrocardiographic monitoring was carried out in all patients during their hospitalization. The mean corrected QT (QTc) interval was 542 +/- 56.8 ms. Known cardiac agents (mainly class III antiarrhythmics) were implicated in 13/21 (62%), antipsychotics in 8/21 (38%), and antibiotics in 5/21 patients (24%). Potential drug-interactions through inhibition of cytochrome P450 isoenzymes were considered responsible in 5/21 cases (24%). The underlying cardiovascular diseases included hypertension (57%) with left ventricular hypertrophy (29%), paroxysmal atrial tachyarrhytmias (48%), heart failure (14%), valvular heart disease (10%), and coronary artery disease (5%). Torsade de pointes (TdP) was recorded in 6/21 of patients, and cardiac arrest necessitating resuscitation occurred in five of them. A significant correlation was observed between administration of cardiac agents and TdP events (P < 0.05). TdP and cardiac arrest events were both associated with a QTc interval >510 ms (P < 0.05). Advanced age (>60 years), female gender, hypertension and paroxysmal atrial tachyarrhytmias were the most common identifiable pre-existing factors for drug-induced long QT in our patient cohort. Marked QTc interval prolongation should be considered of prognostic significance for TdP and cardiac arrest events.

Severe accordion effect: Myocardial ischemia due to wire complication during percutaneous coronary intervention: A case report.

A mechanical alteration during manoeuvring of stiff guidewires in tortuous coronary arteries frequently induces vessel wall shortening and coronary psedostenosis, referred as accordion phenomenon. Subtraction of the guidewires normally leads to the entire resolution of the lesions. A case of this transient angiographic finding, during percutaneous coronary intervention in a tortuous right coronary artery, which resulted in a flow limiting effect and myocardial ischemia, is described in the present report. Differential diagnosis from potential procedure complications and interventional methodology issues are discussed, while similar reports are reviewed.

Large left atrial myxoma presented as fever of unknown origin: a challenging diagnosis and a review of the literature.

Myxoma is the most common type of primary tumors of the heart in adults. The majority of patients with myxomas may experience symptoms due to central or peripheral embolism or intracardiac obstruction, while in some cases, they may be completely asymptomatic. Rarely, patients develop unusual symptoms that complicate the diagnostic evaluation. Herein, we describe the case of a 70-year-old patient with a long-lasting low-grade fever due to a large left atrial myxoma revealed during a transthoracic echocardiography.

Prevalence of paroxysmal atrial fibrillation in Brugada syndrome: a case series and a review of the literature.

OBJECTIVE: The present study aimed at investigating the incidence of paroxysmal atrial fibrillation in 10 patients with spontaneous or induced type 1 electrocardiographic pattern of Brugada syndrome (three with syncopal episodes and seven asymptomatic). Both clinical entities are closely associated with changes in autonomic modulation and, particularly, with increased vagal tone. METHODS: Transthoracic echocardiography, exercise treadmill test and 24-h Holter recordings were performed to all patients. RESULTS: Episodes of atrial fibrillation were recorded in 2/10 patients (20%). These patients suffered from syncopal episodes, exhibited a positive electrophysiological study, and finally received an implantable cardioverter-defibrillator. CONCLUSIONS: The present case series points out a high incidence of paroxysmal atrial fibrillation predominantly in symptomatic patients with type 1 electrocardiographic pattern of Brugada syndrome, indicating that the presence of atrial tachyarrhythmias may reflect an advanced stage of the disease. The prognostic significance of paroxysmal atrial fibrillation, particularly in asymptomatic patients with an electrocardiographic pattern consistent with Brugada syndrome requires further evaluation. Physicians should always be aware of Brugada syndrome in young patients with lone atrial fibrillation, especially in those with a history of syncope.

Brugada electrocardiographic pattern induced during febrile state with marked leukocytosis.

Several agents and conditions have been reported to unmask or accentuate the electrocardiographic pattern of Brugada syndrome including fever. At a molecular level, sodium channels have been showed to be temperature dependent. Herein, we describe a case of Brugada electrocardiographic pattern unmasked during febrile state and marked leukocytosis.

Anomalous origin of the entire coronary system with separate ostia within the right sinus of valsalva: a rare congenital anomaly and a review of the literature.

Congenital coronary artery malformations occur infrequently in the general population. In this report, we describe a rare case of anomalous origin of all three coronary arteries from separate ostia within the right coronary sinus.

Early repolarization syndrome: is it always benign?

Early repolarization syndrome is a well-recognized idiopathic electrocardiographic phenomenon characterized by prominent J wave and ST-segment elevation predominantly in left precordial leads. The syndrome shares remarkable cellular, ionic, and electrocardiographic similarities with the Brugada syndrome and idiopathic ventricular fibrillation (a variant of the Brugada syndrome with ST-segment elevation in inferior leads). Although early repolarization syndrome is considered a benign entity, its arrhythmogenic potential still remains unknown. We report the case of a 39-year-old male with a family history of sudden death and an electrocardiogram consistent with early repolarization syndrome. Diagnostic dilemmas are discussed.