Computational generation of the Purkinje network driven by clinical measurements: the case of pathological propagations

To properly describe the electrical activity of the left ventricle, it is necessary to model the Purkinje fibers, responsible for the fast and coordinate ventricular activation, and their interaction with the muscular propagation. The aim of this work is to propose a methodology for the generation of a patient-specific Purkinje network driven by clinical measurements of the activation times related to pathological propagations. In this case, one needs to consider a strongly coupled problem between the network and the muscle, where the feedback from the latter to the former cannot be neglected as in a normal propagation. We apply the proposed strategy to data acquired on three subjects, one of them suffering from muscular conduction problems owing to a scar and the other two with a muscular pre-excitation syndrome (Wolff-Parkinson-White). To assess the accuracy of the proposed method, we compare the results obtained by using the patient-specific Purkinje network generated by our strategy with the ones obtained by using a non-patient-specific network. The results show that the mean absolute errors in the activation time is reduced for all the cases, highlighting the importance of including a patient-specific Purkinje network in computational models.

Sexual dysfunction related to drugs: a critical review. Part IV: cardiovascular drugs

INTRODUCTION

Sexual dysfunction is a potential side effect of cardiovascular drugs: this article is a critical review of the current literature. Many studies have been published on this topic. Most of these studies are not methodologically robust, few are RCTs and most did not use a validated rating scale to evaluate sexual functioning. In addition, other methodological flaws limit greatly the conclusions of these studies. Most studies relate to male populations and only a few have been conducted on women. Also, the majority of studies on sexual dysfunction induced by cardiovascular drugs relate to antihypertensive drugs. While there is evidence to suggest that older antihypertensive drugs (diuretics, beta-blockers, centrally acting agents) have a negative impact on erectile function, newer agents seem to have either neutral (ACE inhibitors, calcium antagonists) or beneficial effects (i. e., angiotensin receptor blockers, nebivolol). Other cardiovascular drugs analyzed in this review also appear to have an inhibitory action on sexual function. For men, there is some weak evidence supporting the use of specific treatment strategies for sexual dysfunction associated with these drugs.

METHODS

This study was conducted in 2014 using the paper and electronic resources of the library of the "Azienda Provinciale per i Servizi Sanitari (APSS)" in Trento, Italy (http://atoz.ebsco.com/Titles/2793). The library has access to a wide range of databases including DYNAMED, MEDLINE Full Text, CINAHL Plus Full Text, The Cochrane Library, Micromedex healthcare series, BMJ Clinical Evidence. The full list of available journals can be viewed at http://atoz.ebsco.com/Titles/2793 or at the APSS web site (http://www.apss.tn.it). In completing this review, a literature search was conducted using the key words "cardiovascular", "adrenergic beta antagonist", "α1-adrenoceptor antagonist", "angiotensin converting enzyme inhibitor", "angiotensin receptor antagonist", "angiotensin receptor blocker", "beta blocker", "beta receptor antagonist", "calcium channel blocker", "diuretic", "antihypertensive", "sexual dysfunction", "sexual side effects", "treatment-emergent sexual dysfunction". All resulting listed articles were reviewed.

CONCLUSION

The review includes studies that investigated the relationship between these drug treatments and sexual dysfunction. The purpose was to identify possible intervention strategies for sexual dysfunction related to these drugs.

Patient-specific generation of the Purkinje network driven by clinical measurements of a normal propagation

The propagation of the electrical signal in the Purkinje network is the starting point for the activation of the ventricular muscular cells leading to the contraction of the ventricle. In the computational models, describing the electrical activity of the ventricle is therefore important to account for the Purkinje fibers. Until now, the inclusion of such fibers has been obtained either by using surrogates such as space-dependent conduction properties or by generating a network based on an a priori anatomical knowledge. The aim of this work was to propose a new method for the generation of the Purkinje network using clinical measures of the activation times on the endocardium related to a normal electrical propagation, allowing to generate a patient-specific network. The measures were acquired by means of the EnSite NavX system. This system allows to measure for each point of the ventricular endocardium the time at which the activation front, that spreads through the ventricle, has reached the subjacent muscle. We compared the accuracy of the proposed method with the one of other strategies proposed so far in the literature for three subjects with a normal electrical propagation. The results showed that with our method we were able to reduce the absolute errors, intended as the difference between the measured and the computed data, by a factor in the range 9-25 %, with respect to the best of the other strategies. This highlighted the reliability of the proposed method and the importance of including a patient-specific Purkinje network in computational models.

Pulmonary fluid overload monitoring in heart failure patients with single and dual chamber defibrillators

AIMS

Heart failure has a relevant healthcare impact. Monitoring of pulmonary fluid overload (PFO), measured by intrathoracic impedance, has been proposed to alert to heart failure worsening before symptoms become patent. The aim of our research was to evaluate whether PFO diagnostics reduce heart failure hospitalizations in heart failure patients receiving single-chamber or dual-chamber implantable cardioverter-defibrillator (ICD) for primary prevention of sudden death.

METHODS

Twenty-five Italian cardiological centers prospectively followed 221 ICD patients (86% men, 66 ± 11 years, 79% New York Heart Association II and left ventricular ejection fraction 28 ± 5%), of whom 123 received an ICD with PFO monitoring (diagnostics group) and 98 an ICD without such a diagnostics (control group). The association of each patient to a group was assigned a priori, independently of patients' characteristics but based on regional device allocation policies.

RESULTS

Patient clinical characteristics and observation period were similar between groups. In a mean follow-up of 17 ± 11 months, heart failure hospitalizations or emergency-room admissions occurred in eight (7%) patients of the diagnostics group and in 16 of the control group (16%; P = 0.02), with an incidence, measured by Kaplan-Meier analysis, of 23% at 2 years and 34% at 3 years in patients of the control group compared with 8% at 2 and 3 years in patients of the diagnostics group (Log rank test P = 0.044).

CONCLUSION

Our data show that in heart failure patients receiving single-chamber or dual-chamber ICD, the use of intrathoracic impedance monitoring is associated with a significant reduction of heart failure hospitalizations. Our results support the hypothesis that PFO diagnostics improve the likelihood of timely detection of heart failure worsening.

[Remarks on the guideline recommendations for cardioverter-defibrillator implantation for primary prevention of sudden cardiac Death in patients with severe ventricular dysfunction. Consensus Document of the Italian Association of Hospital Cardiologists (ANMCO)/Italian Society of Cardiology (SIC)/Italian Association of Arrhythmology and Cardiac Pacing (AIAC)]

The indications for implantable cardioverter-defibrillator (ICD) therapy for the prevention of sudden cardiac death in patients with severe left ventricular dysfunction have rapidly expanded over the last 10 years on the basis of the very satisfying results of the numerous randomized clinical trials that have provided the framework for guidelines. However, the analysis of clinical practice in the real world has highlighted some important criticisms in the complex process of selection-management of those patients candidates for ICD therapy: 1) approximately one fourth of all ICD implantations is not justified by clinical evidence, 2) approximately one half of patients with an indication for ICD therapy do not undergo implantation, 3) the benefits from ICD therapy do not apply uniformly to all patients, 4) the relationship between the lifesaving benefit and the potential for harm of ICD therapy is still scarcely known. The main reason for this clinical scenario can be ascribed to the guideline recommendations that are based only on few standard cut-off criteria and therefore too generic and insufficiently detailed. This does not help cardiologists in their decision-making process, and results in fear, uncertainty, and sometimes emotional choices. The aim of this consensus document is to discuss current guideline recommendations and to provide the Italian cardiologists with the most updated information to optimize the selection of patients with severe left ventricular dysfunction who should receive ICD therapy.

Clinical outcomes in patients with implantable cardioverter defibrillators and Sprint Fidelis leads

OBJECTIVE

The performances of implantable cardioverter defibrillators and leads are important issues for healthcare providers and patients. In 2007 Sprint Fidelis leads were found to be associated with an increased failure rate and so the purpose of the study was to evaluate long-term mortality and clinical outcomes in patients implanted with Sprint Fidelis leads compared with Sprint Quattro leads.

DESIGN, SETTING, PATIENTS

508 patients with Sprint Fidelis leads and 468 with Sprint Quattro leads were prospectively followed in 12 Italian cardiology centres.

MAIN OUTCOME MEASURES

Information on hospitalisations and other clinical events were collected during scheduled and unscheduled hospital visits. Deaths were identified from medical records or via phone contacts with patients' family members or through the National Office of Vital Statistics.

RESULTS

Over a mean follow-up of 27±18 months 141 deaths occurred in the overall population. No death was observed in patients with diagnosed failing lead. Kaplan-Meier patient survival differed between the two lead groups (80±2% in Fidelis leads vs 70±4% in the Sprint Quattro leads at 4 years, p=0.002). Multivariate analyses showed that mortality was neither associated with lead type nor with diagnosed failed lead. The annual rate of lead failure was 1.8% patient-year for Fidelis leads and 0.2% for the Sprint Quattro leads.

CONCLUSIONS

In our multicentre research, the clinical outcomes of patients with Fidelis leads differed from those of patients with Sprint Quattro leads. Nevertheless, neither mortality nor the combined endpoint of mortality and heart failure hospitalisations was associated with the lead type. http://clinicaltrials.gov/ct2/show/NCT01007474.

[How to identify non-responders to cardiac resynchronization therapy]

Cardiac resynchronization therapy (CRT) has been shown to improve survival, morbidity, symptoms, quality of life and exercise capacity, and to promote a beneficial reverse remodeling of the left ventricle in patients with heart failure, dilated hypokinetic left ventricle and wide QRS. The totality of evidence supports the use of CRT also in patients with mild symptoms (NYHA class II). However, the wider diffusion of CRT is determining a growing clinical and economic impact on national health systems. In clinical practice, in spite of "all-or-none" response, variable degrees of therapy response are commonly observed, but several evidence gaps remain to be addressed. According to recent guidelines for CRT implantation, a multiparametric combination of predictive factors emerging from the analysis of clinical trials, observational studies and registries, represents a useful tool for patient selection.

Permanent His-bundle pacing maintains long-term ventricular synchrony and left ventricular performance, unlike conventional right ventricular apical pacing

AIMS

Right ventricular apical pacing (RVAP) may be deleterious, determining abnormal left ventricular (LV) electrical activation and progressive LV dysfunction. Permanent His-bundle pacing (HBP) has been proposed to prevent this detrimental effect. The aim of our study was to compare the long-term effects of HBP on LV synchrony and systolic performance with those of RVAP in the same group of patients.

METHODS

Our analysis included 26 patients who received both an HBP lead and an RVAP lead, as backup, in our electrophysiology laboratory between 2004 and 2007. After implantation, all devices were programmed to obtain HBP. An intra-patient comparison of the effects of HBP and RVAP on LV dyssynchrony and function was performed at the last available follow-up examination.

RESULTS

After a mean of 34.6 ± 11 months, the pacing modality was temporarily switched to RVAP. During RVAP, LV ejection fraction significantly decreased (50.1 ± 8.8% vs. 57.3 ± 8.5%, P < 0.001), mitral regurgitation significantly increased (22.5 ± 10.9% vs.16.3 ± 12.4%; P = 0.018), and inter-ventricular delay significantly worsened (33.4 ± 19.5 ms vs. 7.1 ± 4.7 ms, P = 0.003) in comparison with HBP. However, the myocardial performance index was not statistically different between the two pacing modalities (P = 0.779). No asynchrony was revealed by tissue Doppler imaging during HBP, while during RVAP the asynchrony index was significantly higher in both the four-chamber (125.8 ± 63.9 ms; P = 0.035 vs. HBP) and two-chamber (126 ± 86.5 ms; P = 0.037 vs. HBP) apical views.

CONCLUSION

His-bundle pacing has long-term positive effects on inter- and intra-ventricular synchrony and ventricular contractile performance in comparison with RVAP. It prevents asynchronous pacing-induced LV ejection fraction depression and mitral regurgitation.

[Catheter ablation of atrial fibrillation: Health Technology Assessment Report from the Italian Association of Arrhythmology and Cardiac Pacing (AIAC)]

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and significantly impact patients' quality of life, morbidity and mortality. The number of affected patients is expected to increase as well as the costs associated with AF management, mainly driven by hospitalizations. Over the last decade, catheter ablation techniques targeting pulmonary vein isolation have demonstrated to be effective in treating AF and preventing AF recurrence. This Health Technology Assessment report of the Italian Association of Arrhythmology and Cardiac Pacing (AIAC) aims to define the current role of catheter ablation of AF in terms of effectiveness, efficiency and appropriateness. On the basis of an extensive review of the available literature, this report provides (i) an overview of the epidemiology, clinical impact and socio-economic burden of AF; (ii) an evaluation of therapeutic options other than catheter ablation of AF; and (iii) a detailed presentation of clinical outcomes and cost-benefit ratio associated with catheter ablation. The costs of catheter ablation of AF in Italy were obtained using a bottom-up analysis of a resource utilization survey of 52 hospitals that were considered a representative sample, including 4 Centers that contributed with additional unit cost information in a separate questionnaire. An analysis of budget impact was also performed to evaluate the impact of ablation on the management costs of AF. Results of this analysis show that (1) catheter ablation is effective, safe and superior to antiarrhythmic drug therapy in maintaining sinus rhythm; (2) the cost of an ablation procedure in Italy typically ranges from €8868 to €9455, though current reimbursement remains insufficient, covering only about 60% of the costs; (3) the costs of follow-up are modest (about 8% of total costs); (4) assuming an adjustment of reimbursement to the real cost of an ablation procedure and a 5-10% increase in the annual rate of ablation procedures, after approximately 5-6 years this would result in significant incremental savings for the Italian Healthcare System. In conclusion, catheter ablation of AF is a cost-effective procedure that is inadequately reimbursed in Italy. Insufficient reimbursement may serve as disincentive to perform AF ablation, thereby limiting patient access to this treatment. Considering the healthcare system perspective, higher initial costs for ablation procedures in the short term may be offset by cost savings mainly associated with decreased hospitalizations over time.

Safety and performance of a system specifically designed for selective site pacing

INTRODUCTION

In the right ventricle, selective site pacing (SSP) has been shown to avoid detrimental hemodynamic effects induced by right ventricular apical pacing and, in the right atrium, to prevent the onset of atrial fibrillation and to slow down disease progression. The purpose of our multicenter observational study was to describe the use of a transvenous 4-French catheter-delivered lead for SSP in the clinical practice of a large number of centers.

METHODS

We enrolled 574 patients in whom an implantable device was indicated. In all patients, SSP was achieved by using the Select Secure System™ (Medtronic Inc., Minneapolis, MN, USA).

RESULTS

In 570 patients, the lead was successfully implanted. In 125 patients, atrial SSP was performed: in 75 (60%) the lead was placed in the interatrial septum, in 31 (25%) in the coronary sinus ostium, and in 19 (15%) in the Bachman bundle. Ventricular SSP was undertaken in 138 patients: in 105 (76%) the high septal right ventricular outflow tract (RVOT) position was paced, in seven (5%) the high free-wall RVOT, in 25 (18%) the low septal RVOT, and in one (1%) the low free-wall RVOT. In the remaining 307 patients, the His zone was paced: in 87 (28%) patients, direct His-bundle pacing and in 220 (72%) patients para-hisian pacing was achieved. Adequate pacing parameters and a lead-related complication rate of 2.6% were recorded during a follow-up of 20 ± 10 months.

CONCLUSIONS

Our results demonstrated that many sites, in the right atrium, in the right ventricle, and in His-bundle region, can be paced using the Select Secure System™.

Monitoring intrathoracic impedance with an implantable defibrillator reduces hospitalizations in patients with heart failure

PURPOSE

Some implantable cardioverter-defibrillators (ICDs) are now able to monitor intrathoracic impedance. The aim of the study was to describe the use of such monitoring in clinical practice and to evaluate the clinical impact of the fluid accumulation alert feature of these ICDs.

METHODS AND RESULTS

Five hundred thirty-two heart failure (HF) patients implanted with these ICDs were followed up for 11 +/- 7 months. A clinical event (CE) was deemed to have occurred if it resulted in hospitalization or milder manifestations of HF deterioration. Three hundred sixty-two acute decreases in intrathoracic impedance (Z events) occurred in 230 patients. Of these episodes, 171 (47%) were associated with a CE within 2 weeks of the Z event. In another 71 (20%) Z events, drug therapy was adjusted despite the absence of overt signs of clinical deterioration. The rate of unexplained Z events was 0.25 per patient-year and 25 hospitalizations were not associated with Z events. The audible alert was disabled in a group of 102 patients (OFF group). HF hospitalizations occurred in 29 (7%) patients in the ON group and 20 (20%, P < 0.001) patients in the OFF group. The rate of combined cardiac death and HF hospitalization was lower in patients with Alert ON (log-rank test, P = 0.007).

CONCLUSIONS

The ICD reliably detected CE and yielded low rates of unexplained and undetected events. The alert capability seemed to reduce the number of HF hospitalizations by allowing timely detection and therapeutic intervention.

Usefulness of intrathoracic fluids accumulation monitoring with an implantable biventricular defibrillator in reducing hospitalizations in patients with heart failure: A case-control study

BACKGROUND

The reduction of hospitalizations in patients with heart failure (HF) may have clinical and economical implications.

MATERIALS AND METHODS

In a case-control study, we compared the number of hospital admissions for congestive HF during the same follow-up period in two homogeneous groups of patients, each consisting of 27 consecutive patients treated with biventricular pacing and back-up defibrillator (B-ICD) in our institution. The first group was implanted with an InSync Sentry, (Medtronic Inc, Minneapolis, MN, US), a B-ICD device with the OptiVol feature for monitoring intrathoracic fluid accumulation and equipped with an active acoustic alarm (Group 1); the second group was implanted with an InSync III Marquis (Medtronic), a B-ICD device with similar features except for the absence of the OptiVol (Group 2). Follow-up visits were performed at 3 month interval or in case of acoustic alarm.

RESULTS

The patient clinical characteristics of the two groups were similar. In Group 1, with 359 +/- 98 days follow-up, 12 of the 27 patients, experienced 18 OptiVol alarms with only one hospital admission for congestive HF occurring in a patient who ignored the acoustic alarm for 13 days. In Group 2, eight HF hospitalizations occurred in seven patients (p < 0.05).

CONCLUSIONS

The OptiVol feature is a useful tool for the clinical management of HF patients as it can result in early treatment during the pre-clinic stage of HF decompensation and in a significant reduction of hospital admissions for congestive HF.

Permanent direct his bundle pacing does not induce ventricular dyssynchrony unlike conventional right ventricular apical pacing. An intrapatient acute comparison study

BACKGROUND

Benefits of A-V synchrony during right ventricular apical pacing are neutralized by induction of ventricular dyssynchrony. Only a few data are reported about direct His bundle pacing influence on ventricular synchronism.

AIM

Was to assess the capability of direct His bundle pacing to prevent pacing-induced ventricular dyssynchrony comparing DDD- (or VVI- in case of Atrial Fibrillation) right ventricular apical pacing with DDD- (or VVI-) direct His bundle pacing in the same patients cohort.

METHODS

23 of 24 patients (mean age 75.1 +/- 6.4 years) with narrow QRS (HV < 65 ms) underwent permanent direct His bundle pacing for "brady-tachy syndrome" (11) or supra-Hisian II/III-degree AV Block (permanent atrial fibrillation 7, AV Node ablation 1). A 4.1 F screw-in lead was fixed in His position, guided by endocardial pacemapping and unipolar recordings. Additional permanent (13 patients) or temporary right ventricular apical pacing leads were also positioned. Inter- and left intra-ventricular dyssynchrony, mitral regurgitation and left systolic ventricular function Tei index were assessed during either direct His bundle pacing or right ventricular apical pacing.

RESULTS

Permanent direct His bundle pacing was obtained in 23 of 24 patients. Indexes of ventricular dyssynchrony were drastically reduced, mitral regurgitation decreased and left systolic ventricular function Tei index improved during direct His bundle pacing (or His bundle and septum pacing) in comparison to apical pacing (p < 0.05). No statistically significant differences were observed between direct His bundle pacing and combined His bundle and septum pacing.

CONCLUSION

Direct His bundle pacing (also fused with adjacent septum capture) prevents pacing-induced ventricular dyssynchrony.

[Reduction of radiological exposure time during radiofrequency catheter ablation procedures using a novel intracardiac localization system based on the Ohm's law]

BACKGROUND

Three-dimensional nonfluoroscopic system may be helpful to guide radiofrequency catheter ablation procedures and to reduce the radiological exposure. A new intracardiac navigation and multicatheter visualization system based on Ohm's law (LocaLisa, Medtronic, Minneapolis, MN, USA) has been recently introduced. The aim of our study was to assess the efficacy of the Loca-Lisa system in comparison to fluoroscopy-based approach in reducing the radiological exposure time required for radiofrequency catheter ablation procedures.

METHODS

One hundred and thirty-seven consecutive patients underwent LocaLisa-based radiofrequency catheter ablation procedures in our cardiac electrophysiology laboratory during 19 months of LocaLisa utilization (from October 2001 to April 2003): 46 atrial flutter, 44 atrioventricular node reentrant tachycardia, 16 atrioventricular reentry tachycardia due to atrioventricular accessory pathway, 14 atrial fibrillation, 11 ectopic atrial tachycardia, and 6 atrioventricular node modulation. We retrospectively compared the radiological exposure times of this group of patients to those of the last 137 patients undergone fluoroscopy-based radiofrequency catheter ablation procedures for curing the same index arrhythmia by the same procedural protocol.

RESULTS

The mean radiological exposure time was significantly shorter for the LocaLisa-based radiofrequency catheter ablation procedures (16 +/- 12 vs 34 +/- 17 min; reduction of 53%, p < 0.01) and it occurred for all the arrhythmia types. The reduction was of 64% (from 39 +/- 18 to 14 +/- 12 min, p < 0.01) for atrial flutter, 42% (from 24 +/- 10 to 14 +/- 11 min, p < 0.01) for atrioventricular nodal reentrant tachycardia, 30% (from 40 +/- 14 to 28 +/- 14 min, p = 0.02) for atrioventricular reentry tachycardia, 57% (from 49 +/- 12 to 21 +/- 13 min, p < 0.01) for atrial fibrillation (right atrial linear lesions), 50% (from 38 +/- 12 to 19 +/- 8 min, p < 0.01) for ectopic atrial tachycardia and 42% (from 12 +/- 11 to 7 +/- 5 min, p = NS) for atrioventricular node modulation. The reduction in the radiological exposure time progressively increased as our team got used with the nonfluoroscopic navigation system.

CONCLUSIONS

Overall and single arrhythmia-divided mean radiological exposure times can be significantly reduced by the LocaLisa system during radiofrequency catheter ablation procedures. The reduction of radiation increases progressively by becoming friendly to the system with a very short duration of learning curve phase.

[Hemodynamic and coronary angiographic performance at a center with medium-low activity: organization model, activity indicators, and costs]

BACKGROUND

In order to evaluate the cost-effectiveness of coronary angiography performed in a low volume Center, we examined our 1-year activity.

METHODS

The organizational model of the multipurpose cardiac catheterization laboratory is described. In this type of facility both coronary angiographic and electrophysiological studies are performed. To evaluate the laboratory performance we examined the utilization level, the appropriateness of the studies, the complication rates and the number of studies that had to be repeated because of inadequate data or image quality. The costs were calculated for the in-house laboratory setting (the actual scenario) and for the 25 km distant laboratory setting (the historical scenario).

RESULTS

The laboratory caseload of coronary angiography was 342 studies, 46% of the overall laboratory activity; 175 patients (51%) underwent non-pharmacological therapy, 129 patients (38%) were treated with medical therapy; the percentage of patients with normal coronary arteries was 11%. Two patients (0.58%) had vascular complications, 1 patient (0.29%) developed an acute myocardial infarction 2 hours after coronary angiography without any evidence of angiographic modifications at the repeated study. In no patient the study had to be repeated because of inadequate data or image quality. The mean cost of a coronary angiography was Lit. 512,000 (265 Euro) for the actual scenario; it would have been Lit. 694,000 (359 Euro) for the historical scenario, with Lit. 182,000 (94 Euro) saved.

CONCLUSIONS

These findings are consistent with the accepted criteria of good laboratory performance and cost-effectiveness. Thus coronary angiography can be performed effectively and efficiently in a low volume Center.

[Efficacy of treatment with rt-PA of massive pulmonary embolism in patients with contraindications for thrombolytic therapy]

Pulmonary embolism is a life-threatening condition that is accompanied by significant morbidity and mortality. In massive pulmonary embolism, where restoration of pulmonary arterial flow is urgently required, the only options available are surgical thromboembolectomy and/or thrombolytic therapy. Unfortunately, a large part of thromboembolic diseases is also considered as an absolute or relative contraindication to thrombolysis. The purpose of this paper was to emphasize the possibility of new thrombolytic agents of disregarding, according to circumstances, the contraindications to thrombolytic treatment.