A closed-chest model of selective atrial myocardial infarction for the study of induced electrophysiological and structural derangements

Background

The diagnosis of atrial infarction is often masked by the frequent association with ventricular infarction. For this reason, the electrophysiological and structural consequences of selective atrial ischemia are poorly understood.

Purpose

The objective of this study was to analyze the alterations in the ECG, local electrograms, and multifrequential atrial myocardial impedance in a new experimental model of acute and chronic atrial infarction.

Methods

Seven anesthetized pigs were subjected to 4h of atrial ischemia induced by selective catheter occlusion of the atrial coronary branches originating in the left circumflex coronary artery. The surface ECG was recorded and the changes in P-wave morphology analyzed. Four weeks later the animals were subjected to endocardial voltage mapping (Carto) and multifrequential impedance. The hearts were processed for anatomopathological study.

Results

Selective occlusion of the coronary atrial branches induced atrial infarction with fibrosis in the left atrium in 6 of the 7 cases (Figure). The surface ECG showed prolongation of the P-wave duration (Figure) (P-wave in lead II: from 72±8ms at baseline vs. 97±18ms at 4 weeks, ANOVA p<0.01; P-wave in lead aVR: from 71±3ms at baseline vs 87±9ms at 4 weeks, ANOVA p<0.01) with no appreciable displacement of the PR segment. Endocardial mapping of the left atrium showed low-voltage bipolar zones with decreased multi-frequency impedance phase angle values, as compared with preserved zones of the same atrium (bipolar electrograms: from 0.6±1mV to 2.0±1.9mV, T-Test p<0.01; Phase angle at 300KHz: from −5.5±2° to −9.0±4.4° T-Test p<0.05).

Conclusion

We developed a closed-chest swine model of selective atrial infarction suitable for the study of ECG patterns and electrophysiological mechanisms linked to atrial myocardial ischemia and infarction. The structural derangements are detectable by endocardial mapping of local voltage electrograms and local tissue impedance.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Supported by grants from ISCI-MINECO (FIS PI17/00069), FEDER, CIBERCV (CB16/11/00276)

Real-time electrophysiological characterization of acute and chronic radiofrequency ablation lesions

Background

Assessment of lesion formation remains one of the most important goals to guide radiofrequency (RF) procedures in the cardiac electrophysiology laboratory. Cardiac navigation systems use specific algorithms to predict the effective lesion size, but these metrics are based only on ablation parameters and ignore local electric tissue characteristics. [1] Recent studies show that local multiparametric impedance is influenced by the intrinsic structural characteristics of the tissue. [2]

Purpose

This study aimed to assess the ability of local multiparametric impedance to characterize acute and chronic RF ablation lesions in the right atrium of pigs.

Methods

Four anesthetized closed-chest pigs were submitted to two interventions. The first intervention aimed at creating RF ablation lesions (30W, 60s, 55°) in the right atrium using an electrocatheter connected to a conventional cardiac navigation system, while mapping the local multiparametric impedance (LMI), the generator impedance (GI) and the bipolar voltage (BiV). All RF ablation lesions were performed with a stable contact force. Four weeks later, the second intervention aimed at mapping again the previous ablation sites. After the second intervention animals were euthanized and the hearts were removed and processed to identify the presence of fibrosis in the previously ablated lesions (Figure).

Results

We performed 19 ablations (5±2 per animal) with an average contact force of 14.2±4.6g. Four weeks later, 14/19 (74%) ablation lesions were identified as fibrotic points in the explanted heart (Figure 1). These showed decreased acute LMI and BiV values that persisted low after 4 weeks (Table 1). The remaining 5/19 ablations that did not present fibrosis had lower baseline LMI and bipolar values that resulted in lower LMI and BiV drops (Table 1). The absolute drop in LMI between effective and non-effective lesions was around 50%, while GI drop was only 21% (LMI drop @51KHz: From −3.0±1.4° to −1.5±0.3°, T-TEST p<0.05; GI drop: From 12.7±27.6Ω to 10.5±21.3Ω, T-TEST p=0.89).

Conclusion

The local baseline electrical properties of atrial myocardium are directly related to the effectiveness of RF ablation lesions. RF ablation sites that resulted into persistent fibrosis points had larger LMI and BiV values, with higher absolute drops than non-effective lesions. The use of LMI in clinical practice could improve the outcome of the procedures of arrhythmia ablation in the electrophysiology lab.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Supported by grants from ISCI-MINECO (FIS PI21/00392), FEDER, CIBERCV (CB16/11/00276)

Outcomes of radiofrequency catheter ablation for persistent and long-standing persistent atrial fibrillation

Introduction

Catheter ablation has become the first-line treatment for symptomatic patients with atrial fibrillation (AF). Several approaches of substrate ablation have been used for persistent and long-standing persistent AF and the best protocol procedure is yet to be established. The purpose of this study was to evaluate the outcomes of patients submitted to catheter ablation of persistent and long-standing persistent AF adding extra-pulmonary substrate approaches to pulmonary vein isolation.

Methods

We retrospectively studied 67 consecutive patients referred for the first procedure of catheter ablation of persistent or long-standing persistent AF from May 2016 to October 2018. The first 27 patients were subjected to pulmonary vein isolation and complex fractionated atrial electrograms (CFAE) ablation (group 1) and the last 40 patients were subjected to a tailored approach guided by voltage map areas and CFAE (group 2). Patient characteristics, procedure details and follow-up were assessed, and predictors of recurrence were determined.

Results

Mean age was 59±11 years with 58% being male. During a mean follow-up of 16±6 months 27% of the patients showed AF recurrence. There were no differences in baseline characteristics of group 1 and 2. A higher recurrence rate was found in group 1 by comparison with group 2 (40.7% vs 17.5%, Log Rank X2 = 5.076, P=0.024) (Figure 1). Also, recurrence was associated with a longer AF duration, an increased baseline Brain Natriuretic Peptide (BNP), an increased left atrium (LA) volume, the presence of hyperthyroidism, the absence of sinus rhythm after procedure, the inducibility of AF post-ablation and the absence of an antiarrhythmic drug at hospital discharge. After adjustment for other confounders, the patient group (HR 5.16 [1.23–21.71] P=0.025), a long-standing AF (HR 9.09 [1.41–58.82] P=0.020), the BNP value at admission (HR 1.03 [1.01–1.05] P=0.033) and the LA volume index (HR 1.13 [1.02–1.25] P=0.017) were the only independent predictors of recurrence.

Conclusion

Ablation of persistent and long-standing persistent AF is feasible with good results when a substrate approach is added to pulmonary vein isolation. A tailored approach seems to be more efficient, showing best outcomes in mid-term follow-up. A long-standing AF, higher BNP value and the LA enlargement are important predictors of recurrence and should be used to better select patients and to manage follow-up.

Funding Acknowledgement

Type of funding sources: None.

Stent strategies in left main bifurcation lesions: the simpler, the better?

Introduction

Although percutaneous coronary intervention (PCI) for ostial or midshaft lesions in left main (LM) disease has shown similar results as compared with coronary artery bypass grafting (CABG), distal LM bifurcations are associated with an increase in procedural complexity and higher rates of target lesion revascularization. Several studies have investigated the optimal stenting strategy in patients with coronary bifurcation lesions and showed no benefit for systematic two-stent approach in comparison with provisional stenting. This is reflected in the current guidelines that recommend provisional stenting of the side branch as the preferred approach for most bifurcation lesions. However, there is still debate about the optimal strategy according to lesion location.

Objectives

This analysis aimed to compare the clinical outcomes of LM bifurcation PCI using a provisional strategy versus a two-stent strategy.

Methods

Retrospective, observational study including patients submitted to LM bifurcation (Medina 1,1,1) PCI between January 2010 and December 2019. Data was collected from the emergency department and hospitalization registries. Patients were divided according to the stenting approach. We made a global analysis including baseline clinical and angiographic data. The primary endpoint was target lesion failure (TLF), defined as the composite of myocardial infarction, cardiac death, and target lesion revascularization (TLR). Secondary endpoints included the individual components.

Results

A total of 106 patients were included (median age 74 [66–82], 79 (74.5%) males), 57 (53.8%) submitted to provisional stenting and 49 (46.2%) to a two-stent technique. Baseline characteristics were well matched (table 1). The mean SYNTAX score was 29.6±10.0 and LM stenosis grade was ≥70% in all lesions. Median follow-up was 26.6 [12.0–48.6] months. No differences were found regarding the primary endpoint (TLF in provisional stenting was 21.7% vs 21.4%, HR 2.432; 95% confidence interval, 0.472–12.450; p=0.233.). Although target lesion revascularization within the LM complex was numerically higher in the two-stent group (10.2% vs. 3.5%, p=0.245), the opposite was found in cardiac death (provisional group 10.5% vs. 4.3%, p=0.289).

Conclusions

Besides being a “simpler” technique, provisional stenting had no significant differences in outcomes compared to two-stent techniques. Without further evidence, revascularization strategies should primarily rely on operator expertise.

Funding Acknowledgement

Type of funding sources: None.

Interventional cardiology in times of COVID-19: impact on a terciary centre

Introduction

Cardiovascular diseases are the leading cause of death worldwide and the pandemic caused by coronavirus disease 2019 (COVID-19) has forced profound changes in the care of patients with cardiac conditions. In Portugal, an increase in mortality beyond that attributed solely to COVID-19 was observed. We aimed to realize how COVID-19 has changed the activity of our Interventional Cardiology Unit.

Methods

We retrospectively assessed all patients submitted to any interventional procedure in 2019 and 2020 in our hospital. A total of 7621 patients and 9163 procedures were evaluated. The mean weekly numbers of coronarography, angioplasty, right heart catheterization and structural heart intervention during 2019 were assessed and were compared with the first COVID-19 wave (comprising March and April 2020) and the second COVID-19 wave (including the time period from October to end of December 2020).

Results

Mean age was 65.2±16.6 years with 72% being male. In the first COVID-19 wave there was a significant reduction in the mean weekly numbers of all procedures, with a 64% decline in coronarographies (30.9±29.3 vs 87.2±12.9, P<0.001), 48% in angiographies (15.7±10.9 vs 30.2±5.7, P=0.004), 51% in right heart catheterizations (5.3±5.9 vs 10.9±4.5, P=0.002) and 57% in structural heart interventions (1.1±1.9 vs 2.6±2, P=0.044). Although there was an evident recovery in activity (figure 1), comparing to 2019, the second wave also showed a significant lower number of procedures, with 24% fewer coronarographies (66.6±20.6 vs 87.2±12.9, P=0.003) and 13% fewer angiographies (26.4±7.6 vs 30.2±5.7, P=0.004). Contrariwise, in the second wave there was no difference in the number of right heart catheterizations (7.3±6.1 vs 10.9±4.5, P=0.055) or structural heart interventions (1.6±1.6 vs 2.6±2, P=0.106).

Conclusions

In our Interventional Cardiology Unit, COVID-19 led to a significant reduction of procedures in the first and second pandemic waves. The effect on the increase in morbidity and mortality has yet to be determined. Health authorities should focus attention in defining measures to amend the consequences of this documented activity reduction.

Funding Acknowledgement

Type of funding sources: None.

Heart failure with reduced ejection fraction: predicting exercise intolerance with echocardiography

Introduction

Cardiopulmonary exercise testing (CPET) is routinely used in the prognostic evaluation of patients with heart failure with reduced ejection fraction (HFrEF). Left ventricular ejection fraction (LVEF) is a strong prognostic marker but have shown a bad correlation with exercise capacity. The aim of this study is to assess the relationship between echocardiographic parameters and exercise capacity in HFrEF patients.

Methods

We retrospectively assessed all patients with HFrEF submitted to CPET and echocardiography between March and September of 2019. 73 patients were eligible for analysis. ANOVA test was used to compare Weber class groups regarding echocardiographic parameters. Multivariate linear regression with a stepwise approach was used to assess independent predictors of peak VO2 uptake. ROC curves were compared to assess the best parameter to discriminate a peak VO2 &lt;10 ml/kg/min (Weber class D).

Results

Mean age was 53.4±11.7 years with 72.6% being male. Mean LVEF was 29.2±7.7% and mean peak VO2 was 13.4±3.8 ml/kg/min. Between the Weber class groups, significant differences were found in left (LV) and right ventricular (RV) longitudinal strain (P&lt;0.001 and P=0.005 respectively), in the left and right atrial reservoir strain (P=0.009 and P&lt;0.001 respectively), in pulmonary velocity acceleration time (P=0.002) and in maximal tricuspid regurgitation velocity (TRmax) (P=0.014). Left ventricular ejection fraction, tricuspid annular plane systolic excursion, and ratio E/e' were not significantly different among exercise capacity groups. Additionally, only RV longitudinal strain (r2=0.225, P=0.008) and TRmax (r2=0.073, P=0.030) were independent predictors of peak VO2. RV longitudinal strain showed the best accuracy in discriminating a Weber class of D (AUC=0.731, 95% CI: 0.613–0.848, P=0.005) with a calculated cut of −8.6% and with a negative predictive value of 95%.

Conclusion

RV longitudinal strain and TRmax seem to be the best echocardiographic predictors of exercise intolerance in patients with HFrEF. Since CPET is not widely available, these echocardiographic parameters can be clinically useful as a surrogate prognostic factor.

Funding Acknowledgement

Type of funding sources: None.

Can left atrial mechanics predict anticoagulation in cryptogenic stroke?

Introduction

Ischemic stroke is a leading cause of death and disability in the Western world, frequently due to cardioembolism and atherothromboembolism. Cryptogenic strokes occur without a well-defined aetiology after a standard vascular and cardiac evaluation, and secondary prevention may include antiplatelet therapy while awaiting results of long-term cardiac monitoring. In this study, we aimed to identify echocardiographic predictors of paroxysmal atrial fibrillation (AF) latter identified in follow-up of patients with cryptogenic stroke.

Methods

We retrospectively assessed all patients with cryptogenic stroke admitted in our hospital in the last 2 years. Only patients in normal sinus rhythm with a minimum of 24 hours of cardiac monitoring at admission and 24 hours Holter monitor within 6 months after discharge were included. Echocardiographic measures included left ventricle ejection fraction, left atrium (LA) volume, left and right atrium longitudinal strain, left and right ventricle longitudinal strain, E/A ratio, E/e' ratio, isovolumetric relaxation time (IVRT) and E wave deacceleration time. Echocardiographic data was assessed to determine its accuracy to identify AF.

Results

The study included 32 patients with a mean age of 72±10 years and a male preponderance (87.5%). AF was identified in 12 (37.5%) patients. This group of patients had a larger indexed LA volume (44.3 vs 29.1 mL/m2, p=0.043), a lower IVRT (87 vs 116 ms, p=0.028), and a lower LA longitudinal strain in contractile (6.7 vs 13.6%, p&lt;0.001) and in reservoir phase (17.1 vs 23.6%, p=0.042). All other variables were not significantly different among groups, including LA longitudinal strain in conduit phase. LA longitudinal strain in contractile phase showed the best predictive power with an area under the ROC curve of 0.925 (95% CI 0.82–1 p=0.001). The cut-off value that best predicted AF was 8.17% with a sensitivity of 1 and specificity of 0.9.

Conclusion

LA longitudinal strain in contractile phase is a powerful method to identify AF in cryptogenic stroke. When reduced, anticoagulation may be considered in order to prevent recurrence. Further studies are warranted to reproduce these results in larger cohorts.

Funding Acknowledgement

Type of funding source: None

162 Right ventricular function: is longitudinal strain by speckle-tracking an option?

Introduction

Estimation of right ventricular (RV) performance by echocardiography is challenging due to its anatomical and functional distinctiveness. RV longitudinal strain (RVLS) by speckle-tracking (STE) is an innovative tool and recent studies show that it can be used with prognostic significance, although it isn’t yet standardized.

Purpose

In this study, we aimed to evaluate global (G) and free wall (FW) RVLS-STE and its correlation with common RV evaluation methods.

Methods

We conducted a prospective observational study including 65 patients and 20 healthy controls. G and FW RVLS-STE were correlated to tricuspid annular plane systolic excursion (TAPSE), Doppler tissue tricuspid lateral annular systolic velocity (S`) and left ventricle ejection fraction (LVEF). Following current guidelines, a TAPSE higher than 17mm, a peak S` wave velocity higher than 9.5cm/s and a RVLS-STE inferior to -20% was considered normal.

Results

Mean age was 66.34 ± 15.45 years with 61.5% males in the patient group and 31.1 ± 7 years with 50% males in the control group. Echocardiographic findings in patient group included 44.6% with reduced LVEF (EF &lt; 50%), 26.2% with moderate to severe valvular disease, 23% with an elevated systolic pulmonary pressure (&gt; 35mmHg) and 36.9% without significant structural disease. The control group had no pathological signs on echocardiography. Peak S` wave and TAPSE showed a better correlation with FW RVLS-STE (r²=0.41, p &lt; 0.001 and r²=0.46, p &lt; 0.001) than G RVLS-STE (r²=0.27, p &lt; 0.001 and r²=0.30, p &lt; 0.001). A high absolute FW RVLS-STE (&lt; -20%) was a good marker of a normal TAPSE and a normal peak S` wave velocity, with a negative predictive value of 87% and 98% respectively. Comparing to control group, patients with reduced LVEF showed a reduction in TAPSE (27.6 mm vs 18.53 mm, p &lt; 0.001), S` (14.8 cm/s vs 10.84 cm/s, p &lt; 0.001) and FW RVLS-STE (-28.7% vs -15.34%, p &lt; 0.001). Patients with moderate to severe valvular disease also showed a reduction in TAPSE (27.6 mm vs 18.4 mm, p &lt; 0.001), S` (14.8 cm/s vs 10.3 cm/s, p &lt; 0.001) and FW RVLS-STE (-28.7% vs -16.04%, p &lt; 0.001). And finally, patients with elevated systolic pulmonary pressure also showed a reduction in TAPSE (27.6 mm vs 17.94 mm, p &lt; 0.001), S` (14.8 cm/s vs 10.47 cm/s, p &lt; 0.001) and FW RVLS-STE (-28.7% vs -16.7%, p &lt; 0.001).

Conclusion

FW RVLS-STE is better than G RVLS-STE as a RV evaluation method. RVLS-STE is correlated with TAPSE and peak S` wave velocity. It was the only parameter that showed reduction to abnormal values (&gt; -20%) in pathological groups and seems to be an accurate marker of RV function particularly detecting early dysfunction

P1249 Straight from the heart

Introduction

Infective endocarditis (IE) remains a diagnostic and therapeutic challenge and is still associated with high mortality. Systemic complications are frequently present, and an adequate assessment and management are needed.

Purpose

Our aim is to show the importance of an early recognition of IE complications.

Clinical case

We present a case of 54 years old women with a past medical history unremarkable. The patient presented to the hospital with high fever and was admitted with a diagnosis of a psoas abscess and staphilococus aureus bacteremia. After one week of antibiotic treatment the patient was transferred to an intensive care unit due to septic shock and respiratory failure. The patient needed to be intubated and ventilated and was on treatment with vancomycin and meropenem. During admission, several infectious loci were identified, including cerebral and pulmonar involvement. An echocardiography identified mild mitral regurgitation, moderate tricuspid regurgitation and confirmed the presence of two vegetations, one in tricuspid valve with 30mm and one in mitral valve with 5mm. Nevertheless, the patient improved clinically. After 15 days of treatment, the patient was extubated and was transferred to the cardiology ward for follow-up. Although clinically stable and without any complain, repeated echocardiographic evaluation identified left ventricular apical aneurysm and partial resolution of vegetations. A coronariography was performed and did not identified any coronary lesion. A magnetic resonance confirmed the ischemic aetiology of the lesions and a diagnosis of embolic myocardial infarction was made. Considering a good resolution of infection, and being the patient stable and asymptomatic, she was discharged after 6 weeks of antibiotic therapy for follow up in cardiology and neurosurgery consultations.

Discussion and conclusion

Despite appropriate antimicrobial treatment, embolic complications are common and usually develop during initial stage of IE. This case shows several embolic complications of IE, including embolic myocardial infarction and cerebral embolism. Although aggressive antibiotic administration was successful in this particular case and cardiac surgery was avoided, the identification of complications allowed a more strict follow up and was determinant for a good clinical result.

Abstract P1249 Figure.

P184 Broken heart complications

Introduction

Patients with persistent chest discomfort or other symptoms suggestive of ischaemia and ST segment elevation in two contiguous leads on electrocardiography should be prompt managed to revascularization and emergent angiography for percutaneous intervention in two hours is the preferred reperfusion strategy.

Purpose

Our aim is to show the importance of differential diagnosis in a patient with an initial diagnosis of ST segment elevation myocardial infarction (STEMI).

Clinical case

We present a case of 67 years old women with a past medical history of dyslipidemia and polymyalgia rheumatica, treated with rosuvastatin 10mg id and prednisolone 5 mg id. The patient was admitted to emergency department complaining of chest pain with 3 hours of evolution that started after a period of nausea and vomiting. Physical examination showed slight tachypnea with 22 breath per minute, blood pressure 93/40 mmHg, heart rate 110 beats per minute, oxygen saturation in room air 90%, heart sounds with a systolic murmur II/VI and lung crackles in inferior lobes, with no peripheral oedema. Electrocardiography showed sinus rhythm and ST segment elevation in DI, DII and V2-6. Patient was treated with aspirin 300mg, ticagrelor 180mg, furosemide 40mg, oxygen therapy and was scheduled for emergent coronariography. This procedure revealed no significant coronary lesions and ventriculography identified apical ballooning, diagnosing takotsubo myocardiopathy. Clinical condition starts to deteriorate, and an echocardiography identified akinetic apical and midventricular segments and hyperkinetic basal segments with systolic anterior motion of mitral valve, significant mitral regurgitation and left ventricular outflow tract obstruction (LVOTO) with an intraventricular gradient superior to 60 mmHg. Adequate hemodynamic monitoring and heart rate control allowed a substantial clinical improvement. Two days later a cardiac magnetic ressonance was done, confirmed the diagnosis and identified an apical thrombus. The patient was later discharged stable with oral hypocoagulation with anti-vitamin K antagonist.

Discussion and Conclusion

Takotsubo cardiomyopathy is a unique cardiac syndrome characterized by transient systolic dysfunction witch often mimics acute coronary syndromes (ACS). After exclusion of an ACS, echocardiography is of primordial importance in the assessment of these patients. Left heart failure with pulmonar oedema, mitral regurgitation, LVOTO and thrombus formation were all complications that were present in this clinical case and established the indication to proper therapeutic attitudes.

Abstract P184 Figure.

P780 Left ventricular torsion in severe valvular disease

Introduction

Left Ventricular (LV) torsion is an important component of LV performance. With the development of speckle tracking echocardiography, it became possible and feasible to measure rotation and twisting with a high degree of accuracy. No standard normal values are defined for peak torsion, although mean values around 10° are found in normal subjects with a slight increase with age.

Purpose

In this study we aimed to evaluate torsion in the different types of severe valvular disease.

Methods

We conducted a retrospective, observational study including patients with severe valvular disease with suitable images for torsion analysis. We included 61 patients (21 with severe aortic stenosis (AS), 20 with severe aortic regurgitation (AR) and 20 with severe mitral regurgitation (MR). Circumferential basal and apical strain was performed, and peak torsion was calculated. Results were compared between groups and were related with echocardiographic parameters, including left ventricle ejection fraction (LVEF).

Results

Mean age was 70.3 ± 13.6 years with a male preponderance (66%). Mean LVEF was within normal range in the aortic valve disease group; no significant difference was found in LVEF between AS and AR patients (57 ± 7.7% vs 55 ± 9.7%, p = 0.57). In comparison with the aortic disease group, MR patients had a reduced LVEF (48 ± 17.3% vs 56 ± 8.7%, p = 0.05). Mean peak torsion was 8.9 ± 5.1° in AS, 12.6 ± 4.9° in AR and 7.9 ± 3.2° in MR (p = 0.004). Comparing with aortic valve disease patients, MR patients had a reduced mean peak torsion (7.9 ± 3.2° vs 10.7 ± 5.3°, p = 0.03). In relation with patients with AS, those with AR had a higher peak torsion (12.6 ± 4.9° vs 8.9 ± 5.1°, p = 0.024) and a higher left ventricle end-diastolic volume (87.3 ± 29.1 mL.m-² vs 64.5 ± 24.9 mL.m-², p = 0.011). Circumferential apical strain showed a negative correlation with peak torsion (r²=0.203, p = 0.006) and with LVEF (r²=0.290, p &lt; 0.001). Peak torsion did not demonstrate any significant correlation neither LVEF nor circumferential basal strain.

Conclusion

LV function and peak torsion are more associated with apical than basal circumferential movement. Aortic valve disease is responsible for LV torsion variations in patients with normal ejection fraction, showing an increase in AR and a reduction in AS. In MR patients a reduced LVEF could entails a decrease in peak torsion.

P1598Electrophysiological and structural characterization of acute atrial myocardial infarction

Background

Atrial myocardial infarction may be a risk for atrial fibrillation. However, the electrophysiological and structural characteristics of the infarcted atrial myocardium are not well known. This study aimed to analyse the changes in local atrial electrograms and myocardial structure in an experimental model of isolated atrial myocardial infarction.

Methods

Five anesthetized, open-chest pigs were submitted to 4 hours of acute atrial myocardial ischemia induced by direct surgical clamping of atrial coronary branches originating from the right coronary artery. In all cases, we recorded simultaneously the 12-lead surface electrocardiogram (ECG) and the epicardial mapping of local atrial electrograms (17 x 12.5 mm patches containing 128 electrodes, with 1 mm inter-electrode distance) in a region close to the occluded branches and in control non-treated atria. The changes in local atrial QRS-ST segment and the amplitude of the P-wave of the ECG were sequentially analysed (Figure). The hearts were removed and processed for anatomopathological examination.

Results

Selective atrial coronary branch occlusion induced a patchy atrial myocardial necrosis with an irregular and abrupt border zone (circled areas in the Figure). During the first 15 min of ischemia, the local atrial electrograms showed increasing R waves, widening of QRS complex, and ST segment elevation leading to monophasic potentials (maximal ST segment at 30 min: from 0.2±0.7 mV to 1.9±1.4 mV, ANOVA p<0.01). This period was followed by a phase of transient electrical recovery characterized by disappearance of monophasic potentials, reduction of ST segment elevation, and recovery of local electrical activation. After 60 min of occlusion, monophasic potentials reappeared and the magnitude of ST segment elevation decreased progressively during the ensuing 3 hours. The spatial transition from areas with monophasic potentials to normal electrograms encompassed 1 or 2 electrodes. The surface ECG showed increased duration of the P-wave (lead II at 3h occlusion: from 73.2±4.5 ms to 88.9±15.5 ms, ANOVA p<0.05) with absence of ST segment changes. Atrial arrhythmias were not observed.

Structural and electrical atrial changes

Conclusion

Selective occlusion of atrial coronary branches induced patchy atrial myocardial necrosis with abrupt anatomical and electrical border zone. The overt QRS and ST segment changes in local atrial electrograms resembled those described in acute ventricular myocardial ischemia, and were associated with widening of the P-wave on the surface ECG. Although acute ischemic arrhythmias were not observed, the atrial structural alterations might set the substrate for re-entrant arrhythmias late after the healing over process.

Acknowledgement/Funding

Supported by grants from ISCI-MINECO (FISPI17/00069), CIBERCV (CB16/11/00276), FEDER and Fundaciό “La Maratό” TV3 (20150830).

Robotic versus laparoscopic distal pancreatectomy: A comparative study of clinical outcomes and costs analysis

BACKGROUND

The robotic surgery cost presents a critical issue which has not been well addressed yet. This study aims to compare the clinical outcomes and cost differences of robotic distal pancreatectomy (RDP) versus laparoscopic distal pancreatectomy (LDP).

METHODS

Data were abstracted prospectively from 2011 to 2017. An independent company performed the financial analysis.

RESULTS

A total of 28 RDP and 26 LDP were included. The mean operative time was significantly lower in the LDP (294 vs 241 min; p = 0.02). The main intra and post-operative data were similar, except for the conversion rate (RDP: 3.6% vs LDP: 19.2%; p = 0.04) and hospital stay (RDP: 8.9 vs LDP 13.1 days; p = 0.04). The mean total costs were similar in both groups (RDP: 9198.64 € vs LDP: 9399.74 €; p > 0.5).

CONCLUSIONS

RDP showed lower conversion rate and shorter hospital stay than LDP at the price of longer operative time. RDP is financially comparable to LDP.

Robotic versus laparoscopic surgery for rectal cancer: a comparative study of clinical outcomes and costs

PURPOSE

The costs involved in performing robotic surgery present a critical issue which has not been well addressed yet. The aims of this study are to compare the clinical outcomes and cost differences of robotic versus laparoscopic surgery in the treatment of rectal cancer and to conduct a literature review of the cost analysis.

METHODS

This is an observational, comparative study whereby data were abstracted from a retrospective database of patients who underwent laparoscopic and robotic rectal resection from October 2010 to March 2017, at Sanchinarro University Hospital, Madrid. An independent company performed the financial analysis, and fixed costs were excluded.

RESULTS

A total of 86 robotic and 112 laparoscopic rectal resections were included. The mean operative time was significantly lower in the laparoscopic approach (336 versus 283 min; p = 0.001). The main pre-operative data, overall morbidity, hospital stay and oncological outcomes were similar in both groups, except for the readmission rate (robotic: 5.8%, laparoscopic: 11.6%; p = 0.001). The mean operative costs were higher for robotic surgery (4285.16 versus 3506.11€; p = 0.04); however, the mean overall costs were similar (7279.31€ for robotic and 6879.8€ for the laparoscopic approach; p = 0.44). We found four studies reporting costs, three comparing robotic versus laparoscopy costs, with all of them reporting a higher overall cost for the robotic rectal resection.

CONCLUSION

Robotic rectal resection has similar clinical outcomes to that of the conventional laparoscopic approach. Despite the higher operative costs of robotic rectal resection, overall mean costs were similar in our series.

Metabolic syndrome contributes to renal injury mediated by hyperoxaluria in a murine model of nephrolithiasis

Metabolic syndrome (MS) individuals have a higher risk of developing chronic kidney disease through unclear pathogenic mechanisms. MS has been also related with higher nephrolithiasis prevalence. To establish the influence of MS on renal function, we designed a murine model of combined metabolic syndrome and hyperoxaluria. Four groups of male Sprague-Dawley rats were established: (1) control group (n = 10) fed with standard chow; (2) stone former group (SF) (n = 10) fed with standard chow plus 0.75% ethylene glycol administered in the drinking water; (3) metabolic syndrome group (MS) (n = 10), fed with 60% fructose diet; (4) metabolic syndrome + stone former group (MS + SF) (n = 10), 60% fructose diet and 0.75% EG in the drinking water. MS group showed a significant injury to renal function when hyperoxaluria was induced. It was demonstrated by a significant decrease of creatinine clearance (p < 0.001), with higher tubular damage (34.3%, CI 95% 23.9-44.7, p < 0.001), produced by deposition of crystals, and increased tubular synthesis of osteopontin as a response to tubular damage. Induction of hyperoxaluria in rats with MS causes severe morphological alterations with a significant impairment of renal function. This impairment is not produced in rats without MS. Therefore, this model can be useful for the study of the influence of MS in stone formation.

A new measuring and identification approach for time-varying bioimpedance using multisine electrical impedance spectroscopy

The bioimpedance measurement/identification of time-varying biological systems Z(ω, t) by means of electrical impedance spectroscopy (EIS) is still a challenge today. This paper presents a novel measurement and identification approach, the so-called parametric-in-time approach, valid for time-varying (bio-)impedance systems with a (quasi) periodic character. The technique is based on multisine EIS. Contrary to the widely used nonparametric-in-time strategy, the (bio-)impedance Z(ω, t) is assumed to be time-variant during the measurement interval. Therefore, time-varying spectral analysis tools are required. This new parametric-in-time measuring/identification technique has experimentally been validated through three independent sets of in situ measurements of in vivo myocardial impedance. We show that the time-varying myocardial impedance Z(ω, t) is dominantly periodically time varying (PTV), denoted as ZPTV(ω, t). From the temporal analysis of ZPTV(ω, t), we demonstrate that it is possible to decompose ZPTV(ω, t) into a(n) (in)finite sum of fundamental (bio-)impedance spectra, the so-called harmonic impedance spectra (HIS) Zk(ω)s with [Formula: see text]. This is similar to the well-known Fourier series of a periodic signal, but now understood at the level of a periodic system's frequency response. The HIS Zk(ω)s for [Formula: see text] actually summarize in the bi-frequency (ω, k) domain all the temporal in-cycle information about the periodic changes of Z(ω, t). For the particular case k = 0 (i.e. on the ω-axis), Z0(ω) reflects the mean in-cycle behavior of the time-varying bioimpedance. Finally, the HIS Zk(ω)s are directly identified from noisy current and voltage myocardium measurements at the multisine measurement frequencies (i.e. nonparametric-in-frequency).

Ileal inducible nitric oxide synthase mRNA expression in response to stress is modified in Sprague-Dawley rats exposed to a previous intestinal inflammation

The ability of stress to initiate or reactivate an inflammatory process seems to depend on an individual's susceptibility to stressful stimuli. The aim of this study was to establish whether previous inflammation alters the response to stress in Sprague-Dawley rats, a strain not especially susceptible to stressful stimuli. Stress exposure was performed in rats treated with indomethacin, to induce cyclic intestinal inflammation, during the inactive phase of inflammation. Both control and indomethacin-treated rats submitted to stress showed a decrease in body weight gain and blood leukocyte levels, as well as an increase in fecal pellet output. The increase in intestinal mucosal mast cell count induced by stress was similar in both groups of animals. Moreover, no differences were observed between control and indomethacin-treated rats in the degree of bacterial translocation and myeloperoxidase levels after stress exposure. Despite these similarities, differences between groups were observed in inducible nitric oxide synthase (iNOS) mRNA expression. Although ileal iNOS mRNA expression was inhibited in healthy rats submitted to stress, stress failed to modify this parameter in indomethacin-treated rats. As iNOS is another inflammatory marker, our results may allow the possibility that a previous intestinal inflammation could change the intestinal susceptibility to stress. Whether these differences in ileal iNOS expression can be indicative of a possible change in the predisposition to develop an intestinal inflammatory reaction in response to stress in Sprague-Dawley rats remains to be elucidated.

Functional changes induced by psychological stress are not enough to cause intestinal inflammation in Sprague-Dawley rats

BACKGROUND

It is well known that stress contributes to the perpetuation of several gastrointestinal diseases. However, its role as a trigger of the inflammatory process in absence of other putative contributing factors remains controversial. Our aim was to elucidate whether stress per se can induce a primary gut inflammation in non-predisposed rats.

METHODS

Male Sprague-Dawley rats were divided in sham and stress groups. Chronic stress was induced by subjecting animals 1 h day(-1) to wrap restraint or water avoidance stress alternatively for five consecutive days, as a model of ongoing life stress.

KEY RESULTS

Chronic stress induced a significant decrease in body weight gain without changes in food intake and an increase in frequency of defecation. Electromiografic (EMG) study showed that the duration of the migrating motor cycles (MMCs), but not its frequency, was shortened in stressed animals compared with non-stress conditions. Moreover, stressful stimulus caused mucosal mast cell hyperplasia and a decrease of iNOS mRNA expression. Bacterial translocation observed in stressed animals was not related to changes in epithelial barrier function and was not enough to induce intestinal inflammation.

CONCLUSIONS & INFERENCES

Decreased MMC duration, mast cell hyperplasia and decreased mRNA iNOS expression, but not altered epithelial barrier function, could be factors implicated in bacterial translocation-induced by chronic stress. However, these changes are not sufficient to induce intestinal inflammation in stress non-susceptible strain of rats.

Supplementation of University of Wisconsin solution with Nitroglycerin and Nicorandil in long-term myocardial preservation: effects on the oxidative state, endothelial function and morphology

The purpose of this study was to assess the effects of the addition of Nitroglycerin or Nicorandil to University of Wisconsin solution in long-term myocardial preservation. In a model of heterotopic heart transplantation in pigs, the donor heart was preserved for 24 hours by means of continuous perfusion in this solution, in the presence or absence of these drugs. During this period, the oxygenation and pH of the solution were measured, as were lactate concentrations and enzyme release. At regular intervals following reperfusion we measured the concentrations of enzymes, antioxidants, glutathione peroxidase, glutathione reductase, malondialdehyde, endothelin and nitrite, and, two hours later, samples of both ventricles were taken for a morphological study. In the treated groups there was a higher lactate production during preservation and, during reperfusion, the signs of contracture and the elevation of enzyme levels were more marked than in the untreated groups. In contrast, the glutathione reductase concentrations did not decrease during the first phase of reperfusion and were directly correlated with those of antioxidants, endothelin levels increased less than in the untreated groups and, in the case of nitroglycerin, the nitrite concentration was significantly greater than in the remaining groups. We conclude that nitroglycerin and nicorandil improved the oxidative state and endothelial function and did not produce substantial morphological changes, but increased cell necrosis and contracture, possibly due to the duration of ischemia.

Hysteresis of a biomaterial: influence of sutures and biological adhesives

We studied the changes in energy consumption of samples of calf pericardium, when joined or not joined by sutures and adhesives, by means of hysteretic cycles. Sixty-four samples were subsequently subjected to tensile stress until rupture. An overlapping suture sewn in the form of a rectangle presented an acceptable mean resistance to rupture of over 10 MPa, although lower than the mean values in an unsutured control series where the mean resistance surpassed 15 MPa. The contribution of an acrylic adhesive to the resistance to rupture was negligible. The sutured samples that were reinforced with adhesives and had not been subjected to hysteretic cycles prior to rupture showed an anisotropic behavior. This behavior appeared to be lost in all the samples that underwent hysteretic cycles. We found an inflection point in the stress/strain curve following the stepwise increase in the load, with a value greater than and proximate to the final load applied. This inflection should be analyzed by means of microscopy. Finally, the mathematical relationship between the energy consumed and the stress applied, the strain or deformation produced and the number of cycles of hysteresis to which the samples were subjected was established as the ultimate objective of this study. The bonding systems provoked a greater consumption of energy, with the greatest consumption corresponding to the first cycle in all the series assayed. An equation relating the energy consumption in a sample to the number of hysteretic cycles to which it was subjected was obtained. Its asymptote on the x-axis indicates the energy consumption for a theoretical number of cycles, making it possible to estimate the durability of the sample.

Elenoside increases intestinal motility

AIM: To study the effects of elenoside, an arylnaph-thalene lignan from Justicia hyssopifolia, on gastro-intestinal motility in vivo and in vitro in rats.

METHODS: Routine in vivo experimental assessments were catharsis index, water percentage of boluses, intestinal transit, and codeine antagonism. The groups included were vehicle control (propylene glycol-ethanol-plant oil-tween 80), elenoside (i.p. 25 and 50 mg/kg), cisapride (i.p. 10 mg/kg), and codeine phosphate (intragastric route, 50 mg/kg). In vitro approaches used isolated rat intestinal tissues (duodenum, jejunum, and ileum). The effects of elenoside at concentrations of 3.2 x 10^-4, 6.4 x 10^-4 and 1.2 x 10^-3 mol/L, and cisapride at 10^-6 mol/L were investigated.

RESULTS: Elenoside in vivo produced an increase in the catharsis index and water percentage of boluses and in the percentage of distance traveled by a suspension of activated charcoal. Codeine phosphate antagonized the effect of 25 mg/kg of elenoside. In vitro, elenoside in duodenum, jejunum and ileum produced an initial decrease in the contraction force followed by an increase. Elenoside resulted in decreased intestinal frequency in duodenum, jejunum, and ileum. The in vitro and in vivo effects of elenoside were similar to those produced by cisapride.

CONCLUSION: Elenoside is a lignan with an action similar to that of purgative and prokinetics drugs. Elenoside, could be an alternative to cisapride in treatment of gastrointestinal diseases as well as a preventive therapy for the undesirable gastrointestinal effects produced by opioids used for mild to moderate pain.

Central nervous activity of elenoside

Elenoside is a cytotoxic arylnapthalene lignan (NSC 644013-W/1) derived from Justicia hyssopifolia (Family: Acanthaceae). The neuropharmacological activity of this lignan, a beta-D-glucoside was studied. The LD50 (24 h) of elenoside in mice is 305 +/- 7 mg/kg by i.p. route. In the present study elenoside was given to rats at doses of 25 and 50 mg/kg, and its effects on locomotor activity (Varimex test), muscular relaxant activity, open-field test and with chlorpromazine, 10 mg/kg was compared. On Varimex test, spontaneous activity was reduced. Elenoside produced a reduction in the permanence time on muscular relaxant activity (traction test). On open-field test, ambulation and rearing were reduced compared with the control group and an increase in boluses of dose-dependent rate was obtained. Thus it can be concluded that elenoside has central sedative effects and possible application in anxiety conditions.

Does providing social services with information and advice on immunisation status of "looked after children" improve uptake?

We prospectively assessed whether providing social services with information on the immunisation status for a cohort of looked after children in the care of an urban unitary authority in England improved uptake rates. The provision of such information did not improve immunisation coverage in these children.

Mechanical effects of increases in the load applied in uniaxial and biaxial tensile testing. Part II. Porcine pericardium

The mechanical behavior of porcine pericardium was analyzed to compare it with that of calf pericardium employed in valve leaflets for cardiac bioprostheses. Forty samples of pericardium were subjected to uniaxial tensile testing, 20 as controls and 20 exposed to loads increasing stepwise from 0.5 to 1.5 kg and to 3 kg, and thereafter to rupture, with a return to zero load between each new increment. Another 20 samples were used in biaxial tensile tests involving the application of loads increasing stepwise (to 0.5, 1.5, 3 and 5 kg) until rupture with a zero-load interval before each increment. The ultimate stresses were very similar, showing no statistically significant differences when compared in terms of type of assay, controls and study samples or region of pericardial tissue being tested. In the stepwise biaxial assays, the mean stresses at rupture were also very homogeneous. Using morphological and mechanical criteria for sample selection, it was possible to obtain mathematical fits for the stress/strain relationship, with excellent coefficients of determination. The relationship between the area under the stress/strain curve and the load applied or the strain observed was also studied in the biaxial assay as an equivalent to the cycles of hysteresis produced in the test. The increment in the area under the curve (the energy consumed) may be a good parameter for assessing the changes in the collagen fiber architecture of the pericardial tissue, changes that may help to detect early failure.

Mechanical effects of increases in the load applied in uniaxial and biaxial tensile testing: Part I. Calf pericardium

The authors analyzed the mechanical behavior of the calf pericardium employed in the construction of valve leaflets for cardiac bioprostheses. Forty samples of pericardium were subjected to uniaxial tensile testing, 20 as controls and 20 exposed to loads increasing stepwise until rupture, with a return to zero load between each new increment. Another 20 samples were used similarly in biaxial tensile tests involving loads increasing stepwise until rupture, again returning to zero load between steps. The ultimate stresses in the uniaxial study were very similar and were not influenced by the region of pericardial tissue being tested or the increments in load to which the tissue was exposed. The mean stresses at rupture in the stepwise biaxial assays were significantly greater (p<0.01). Using morphological and mechanical criteria for sample selection, it was possible to obtain mathematical fits for the stress/strain relationship in both types of assays, with excellent coefficients of determination (R (2)>0.90). In uniaxial tests in which the selection criteria were not applied, the correlation improved as the load increased, a phenomenon that did not occur in the biaxial studies. The values varied throughout the different cycles, adopting exponential forms when the strain was greatest. These variations, which demonstrate that the increase in the energy consumed is a function of the stress applied and of the strain produced, should be good parameters for assessing the changes in the collagen fiber architecture of pericardial tissue subjected to cyclic stress, and may help to detect early failure.

Ventral approach to the rat middle ear for otologic research

OBJECTIVE

To describe a simple approach to the rat middle ear because there are few clear descriptions of this technique with minimal morbidity and mortality.

STUDY DESIGN AND SETTING

Six male Long-Evans rats were used in this study. We designed a cervical approach to the middle ear with the purpose of creating an experimental model of ossiculoplasty that permits the postoperative survival of the animal.

RESULTS

It was possible in all cases to visualize the majority of structures of the tympanic cavity: promontory, round window, stapedial artery, stapes, incus, and tympanic membrane. There were no cases of postoperative infection or facial paralysis.

CONCLUSIONS AND SIGNIFICANCE

The ventral approach to the rat middle ear is a rapid and simple technique that makes the rat the animal of choice for many otologic investigations.

Pharmacological effects of elenoside, an arylnaphthalene lignan

Acute toxicity (24 h) and general behavior in mice of a lignan from Justicia hyssopifolia, a beta-D-glucoside (elenoside), was studied, and the cytotoxic activity was performed. Elenoside (arylnaphthalene lignan) in mice showed a moderate toxicity order (305 mg/kg) and central depressive properties at doses of 25, 50, and 100 mg/kg. It also displayed cytotoxic activity in a range of concentration of 10(-5)-10(-4) M when studied in the human tumor cell line panel of the US National Cancer Institute (NCI). The results indicated that elenoside has central depressant effects, and the cytotoxic activity of elenoside suggests that this compound and its genin derivatives merit further investigation as antitumoral drugs.

General behavior, toxicity, and cytotoxic activity of elenoside, a lignan from Justicia hyssopifolia

Cytotoxicity, acute toxicity, and general pharmacological effects in mice of an arylnaphthalene lignan isolated from Jisticia hyssopifolia were studied. Elenoside was cytotoxic to human cancer cell lines in a range of concentrations from 10(-5) to 10(-4)M. It has an LD(50), ip in mice, of 305 mg/kg and central depressive properties at doses of 25, 50, and 100 mg/kg. Thus, elenoside appears to be a sedative with broad spectrum cytotoxicity.

Titanium levels in rats implanted with Ti6Al4V treated samples in the absence of wear

The effect of implantation time and implant nitriding on titanium ion concentration in several tissues of rats carrying Ti6Al4V implants was studied by means of inductively coupled plasma-mass spectroscopy (ICP-MS). Histological studies were also performed in order to check for tissue degeneration due to the Ti6Al4V implantation. The animals were divided into four groups: one received Ti6Al4V implants, the second received nitrided Ti6Al4V implants, the third group received nitrided and descaled Ti6Al4V implants and the last one was the control group. Half the animals of the implanted groups received the Ti6Al4V implant for 30 days, while the other half received the implant for 120 days. Spleen, muscle, kidney, lung, brain and bone samples were retrieved from these rats as well as the control group. Ion concentration measures did not show significant differences between control and implanted rats for the studied period of time, although histological studies showed minor differences, especially on liver tissue samples.

Increase of C-reactive protein and decrease of surfactant protein A in surfactant after lung transplantation

In this study, we asked whether the serum acute-phase protein C-reactive protein (CRP) increased in large surfactant aggregates after lung transplantation and analyzed the changes in composition and interfacial adsorption activity of those aggregates. Single left lung transplantation was performed in weight-matched pairs of dogs. A double-lung block from the donor animal was flushed with either modified Euro-Collins solution (EC) (n = 6) or University of Wisconsin solution (UW) (n = 6) at 4 degrees C followed by immersion in cold EC or UW for 22 h. The left donor lung was transplanted. The recipient dog was then reperfused for 4.5 h. Irrespective of the preservation fluid, gas exchanged was impaired in the transplanted lung after 4.5 h of reperfusion. Large surfactant aggregates obtained from this lung showed reduced ability to rapidly adsorb to an air-liquid interface. Phospholipid (PL) content and PL composition of surfactant from lung transplants was similar to that of the control lungs. However, the content of surfactant protein A decreased after reperfusion. In addition, Western blot analyses showed that levels of CRP increased in surfactant from transplanted but not from donor lungs. The addition of human CRP to control surfactant (CRP:PL weight ratio, 0.01:1) caused a decrease of surfactant adsorption. We conclude that the impairment of adsorption facilities of surfactant from transplanted lungs may be correlated with decreased levels of surfactant protein A and increased levels of CRP. The presence of elevated levels of CRP in bronchoalveolar lavage could be a very sensitive marker of lung injury.

Initial results of a new procedure for treatment of malignant obstruction of the left colon

PURPOSE

This study was undertaken to analyze the results obtained in 38 unselected patients using a new and original procedure for treatment of malignant obstructions of the left colon.

METHOD

This procedure involves three phases: 1) resolution of the obstruction by means of a stent placed at the site of the tumor; 2) recovery of the general state of the patient, study of the extent of disease, and mechanical preparation of the colon; 3) regulated and final surgery (if this is not suitable, the stent may be used as definitive palliative treatment).

RESULTS

In 35 patients (92 percent), the obstruction was resolved with the stent. In 22 patients the three phases were completed, and in 13 patients the stent constituted definitive palliative treatment. Only one patient (2.6 percent) died after resection of the tumor.

CONCLUSION

This procedure offers a new, safe, and efficacious option for treatment of neoplastic colorectal obstructions.

[Synthetic implants in the reconstruction of the ossicular chain]

Experience has revealed a higher rate of functional failure of biocompatible prostheses used in the surgical reconstruction of the middle ear than was reported initially. The cause of these failures was analyzed in a retrospective study of 135 patients who underwent middle ear reconstructive procedures: 47 of them involved implantation of plastic prostheses. Proplast or Plastipore, and had a sufficient follow-up. We evaluated the prosthetic material and middle-ear conditions for which they were implanted.

Experimental study of the antithrombogenic behavior of Dacron vascular grafts coated with hydrophilic acrylic copolymers bearing salicylic acid residues

The objective of the present work was study of the behavior of active coatings of hydrophilic acrylic polymers bearing salicylic acid residues linked covalently to the macromolecular chains, after their application to woven and knitted Dacron vascular grafts. In vitro tests were carried out under dynamic flow conditions using equipment especially designed to reproduce physiologic conditions, to determine the retention of the coating using a saline solution. Ex vivo tests were carried out in an extracorporeal circuit using the dog as an animal model. The study of the deposition of platelets was followed by labeling of autologous platelets with 111In-oxine, as well as by analysis of the surfaces of the prostheses by scanning electron microscopy. An application of thin coatings of hydrophilic acrylic copolymers improves the antithrombogenicity of the vascular grafts with respect to the uncoated prosthesis. The presence of relatively small amounts of units bearing salicylic acid residues in the copolymer chains (5-20 wt %) gives good results when they are applied to woven and knitten Dacron meshes which have been quantified by analysis of the percentage of radiotracer on the surface of the vascular grafts tested in ex vivo experiments. The salicylic acid residues are released slowly to the medium by hydrolysis of the reversible covalent bonds of this compound to the acrylic macromolecular chains, which provides an additional antiaggregating effect for platelets. The polymeric coating forms a thin active film which improves the antithrombogenic properties of the surface of woven or knitted Dacron vascular grafts in ex vivo experiments.

Modifications induced by atherogenic diet in the capacity of the arterial wall in rats to respond to surgical insult

A study was made of events occurring in the arterial wall of the rat after administration of an atherogenic calcification-inducing diet and of vascular response in a model of combined metabolic aggression (atherogenic, calcification-inducing diet) and surgical aggression (adventitial resection). Female Sprague-Dawley rats were fed an atherogenic, calcification-inducing diet for 24 consecutive days, after which half the rats returned to standard diet (group I, n = 12) and the other half (group II) underwent resection of the adventitia on a segment of common iliac artery on day 25 before returning to standard diet. Normolipemic rats and rats that underwent adventitial resection without the atherogenic, calcification-inducing diet were used as the control groups. The rats were killed at 10 min, 1 and 24 h, 5, 14, 21, 30, 50, 70, 120 and 180 days. Morphologic studies were made with light microscopy and electron microscopy (scanning and transmission), as well as biochemical studies. Monocyte adherence and infiltration of the arterial intima, thickening of the subintimal space, the presence of monocyte-macrophages, calcification in the medial layer, intense adventitial fibrosis, and vacuolization of the endothelial cells of the adventitial microvessels were common findings in the two groups receiving the atherogenic, calcification-inducing diet. However, these groups differed in the intensity of calcification: the deep part of the medial layer did not become calcified when the adventitia was resected. Moreover, adventitial regeneration was delayed in group II with respect to the animals that underwent adventitial resection without atherogenic, calcification-inducing diet. We conclude that this diet induced atherosclerotic lesions in the vessel wall and inhibited adventitial regeneration in the rats that underwent resection.

[Acute effect of lorazepam on respiratory muscles in stable patients with chronic obstructive pulmonary disease]

Benzodiazepines are known to cause muscle hypotonia, but their effects on respiratory muscle function, particularly on diaphragm, have not yet been studied. Our aim was to look for any effect of lorazepam on respiratory muscle function in patients with chronic obstructive pulmonary disease (COPD). Nine stable COPD patients (mean +/- SD forced expiratory volume in one second (FEV1) 0.91 +/- 0.31 l) were included in the study. The following measurements were performed before and 1 hour after lorazepam administration (doses: 1.5 to 2 mg) by sublingual route: forced vital capacity (FVC), FEV1, maximal voluntary ventilation (MVV), arterial oxygen tension (PaO2), arterial carbon dioxide tension (PaCO2), minute ventilation (Ve), tidal volume (Vt), respiratory rate (f), inspiratory time/inspiratory plus expiratory time (Ti/Ttot)-, mean inspiratory flow (Vi), maximal inspiratory (MIP) and expiratory (MEP) pressures, maximal pleural pressure (Pplmax), transdiaphragmatic pressures (Pdi) and skeletal muscle strength and endurance. As expected, no change was noted in FVC, FEV1, FEV1/FVC (Table-1). Besides stability of expiratory flows, this denotes no change in collaboration in spite of the sedative effects of lorazepam. There was a 20% decrease in Ve, due to a Vt reduction and a small increase in PaCO2. These could be explained by the central effects of benzodiazepines. Skeletal muscle strength and endurance decreased significantly (22 and 50% respectively-Table 2), in accordance with the previously reported muscular actions of this pharmacological group. Respiratory muscle function parameters, MIP, MEP, MVV and Ppl showed significant reductions (10 to 20 per cent), as was the case with diaphragmatic function measured by Pdi (Muller maneuver with abdominal protrussion and maximal open-glottis expulsive maneuver) (Table 3). This study demonstrates that a single lorazepam dose reduces strength and endurance of respiratory muscle in chronic stable COPD patients.

Application of new coatings for vascular grafts based on polyacrylic systems with antiaggregating activity

A study has been made of the behaviour of knitted and woven Dacron mesh used in the preparation of vascular grafts when coated with either a layer of poly(2-hydroxyethyl methacrylate) or co-polymers of 2-hydroxyethyl methacrylate with 5, 10 or 20 wt% of an acrylic derivative of salicylic acid, 2-methacryloyloxybenzoic acid. In vitro studies were carried out to quantify the loss of polymer under flow conditions, and ex vivo studies were done in dogs to quantify the deposition of 111In-oxine-labelled platelets. The treated materials showed a lesser deposition of platelet thrombi when compared with the control group.

Prevention of thrombus formation on biomaterials exposed to blood using different antiplatelet drugs: experimental study in dogs

An ex vivo shunt, established in dogs between both femoral arteries and right atrium, has been used to quantify the platelet deposition on six prosthetic materials used in the construction of cardiovascular prostheses: highly porous knitted Dacron (intervascular HP 800, 1400 mL/cm2/min/120 mm Hg), low-porosity woven Dacron (intervascular LP 200, 200 mL/cm2/min/120 mm Hg), double velour knitted Dacron, Avcothane 51 elastomere, and the mesothelial and epipericardial surfaces of bovine pericardium. In the search for a method to prevent platelet thrombi formation on these materials, we studied four groups of dogs: group 1 (control), group 2 (5 mg/kg body weight (BW)/day acetylsalicylic acid), group 3 (20 mg/kg BW/day acetylsalicylic acid), and group 4 (5 mg/kg BW/day acetylsalicylic acid plus 5 mg/kg BW/day dipyridamole). Platelets were labeled with 111In-oxine. The least thrombogenic material was Avcothane 51 elastomere. The only effective treatment for reduction of platelet deposition on the six materials was 5 mg/kg BW/day of acetylsalicylic acid. The dose used in group 3 only decreased the deposition of platelets on three of the six materials studied. The treatment employed in group 4 did not significantly reduce the deposition of platelets on any of the materials when compared with the control group.