Harnessing Transcriptomic Signals for Amyotrophic Lateral Sclerosis to Identify Novel Drugs and Enhance Risk Prediction

Introduction

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. This study integrates the latest ALS genome-wide association study (GWAS) summary statistics with functional genomic annotations with the aim of providing mechanistic insights into ALS risk loci, inferring drug repurposing opportunities, and enhancing prediction of ALS risk and clinical characteristics.

Methods

Genes associated with ALS were identified using GWAS summary statistic methodology including SuSiE SNP-based fine-mapping, and transcriptome- and proteome-wide association study (TWAS/PWAS) analyses. Using several approaches, gene associations were integrated with the DrugTargetor drug-gene interaction database to identify drugs that could be repurposed for the treatment of ALS. Furthermore, ALS gene associations from TWAS were combined with observed blood expression in two external ALS case-control datasets to calculate polytranscriptomic scores and evaluate their utility for prediction of ALS risk and clinical characteristics, including site of onset, age at onset, and survival.

Results

SNP-based fine-mapping, TWAS and PWAS identified 117 genes associated with ALS, with TWAS and PWAS providing novel mechanistic insights. Drug repurposing analyses identified five drugs significantly enriched for interactions with ALS associated genes, with directional analyses highlighting α-glucosidase inhibitors may exacerbate ALS pathology. Additionally, drug class enrichment analysis showed calcium channel blockers may reduce ALS risk. Across the two observed expression target samples, ALS polytranscriptomic scores significantly predicted ALS risk (R2 = 4%; p-value = 2.1×10-21).

Conclusions

Functionally-informed analyses of ALS GWAS summary statistics identified novel mechanistic insights into ALS aetiology, highlighted several therapeutic research avenues, and enabled statistically significant prediction of ALS risk.

The third international hackathon for applying insights into large-scale genomic composition to use cases in a wide range of organisms

In October 2021, 59 scientists from 14 countries and 13 U.S. states collaborated virtually in the Third Annual Baylor College of Medicine & DNANexus Structural Variation hackathon. The goal of the hackathon was to advance research on structural variants (SVs) by prototyping and iterating on open-source software. This led to nine hackathon projects focused on diverse genomics research interests, including various SV discovery and genotyping methods, SV sequence reconstruction, and clinically relevant structural variation, including SARS-CoV-2 variants. Repositories for the projects that participated in the hackathon are available at https://github.com/collaborativebioinformatics.

Duration of dual antiplatelet therapy and long-term outcomes following drug-eluting balloon or drug-eluting stents for treatment of in-stent restenosis (DAPT-Dragon Registry)

Objectives

The aim of the DAPT-DRAGON registry was to asses long-term outcomes and the length of dual antiplatelet therapy (DAPT) in patients treated with percutaneous coronary intervention (PCI) due to drug-eluting stent in stent restenosis (DES-ISR) with drug-eluting balloons (DEB) or thin-DES.

Background

Data regarding the duration of DAPT in patients with DES-ISR treated with PCI is still undergoing research and observation, and the adequate duration of DAPT in this group of patients is not unambiguously sanctioned.

Methods

Overall, 1,367 consecutive patients with DES-ISR who underwent PCI with DEB or DES, were entered into the multi-center DAPT-DRAGON Registry (Fig. 1). The mean age was 66.7±9 years (70.5% males). The median follow-up was 3.3 years. There were 34.1% patients with chronic coronary syndrome, 35.2% with unstable angina, 2.9% with ST segment elevation myocardial infarction and 27.7% with non-ST segment elevation myocardial infarction (MI). We assessed selected study endpoints according to the duration of DAPT (≤3 vs. >3 months and ≤6 vs. >6 months), before and after propensity score matching (PSM): stroke, target lesion revascularization (TLR), target vessel revascularization (TVR), MI, death and device-oriented composite endpoints (DOCE).

Results

Among predictors of increased DOCE rate before PSM, we demonstrated: PCI with DEB vs. DES (p<0.001), recurrent ISR (p=0.002), treatment with glycoprotein IIb/IIIa inhibitor during PCI (p<0.001), lower left ventricle ejection fraction (p=0.004) and extent of stenosis (p<0.001). Pairwise contrast analysis considering type of PCI (thin-DES vs. DEB) and duration of DAPT (≤6 vs. >6 months) before PSM revealed superiority of thin-DES+DAPT >6 months vs. DEB+DAPT >6 months for DOCE (p<0.001), TVR (p=0.02) and TLR (p=0.01). After PSM analysis, the length of DAPT (≤3 vs. >3 months) had no significant influence on assessed long-term outcomes, while the percentage of stroke free survival was significantly lower in the group of patients with DAPT ≤6 months vs. >6 months (p=0.01; Fig. 2).

Conclusions

Long-term treatment with DAPT (>6 months) in patients with DES-ISR with DES implantation is related to better long-term outcomes in terms of lower rate of DOCE, TVR and TLR compared to PCI with DEB. DAPT >6 months is related to a greater rate of strokes, independently of the type of treatment (thin-DES and DEB) compared to DAPT ≤6 months.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2

Overview of pleiotropic effects of platelet P2Y12 receptor inhibitors

Dual antiplatelet therapy consisting of one of the P2Y12 receptor inhibitors in conjunction with aspirin is the mainstay of treatment for patients with acute coronary syndromes (ACS) and those undergoing percutaneous coronary interventions (PCI). In recent years, multiple extra-platelet features of P2Y12 receptor antagonists have been reported in numerous clinical trials. The aim of this review is to summarise reported pleiotropic effects of clopidogrel, prasugrel, ticagrelor and other P2Y12 receptor blockers. We included observations made both in human and in animal models, together with proposed mechanisms of action for described features. If confirmed in randomised studies and properly applied to everyday practice, the observed extra-platelet actions could enable us to improve efficacy of ACS and post-PCI treatment, as well as to confine mortality and occurrence rate of cardiovascular events.

Management of atrial fibrillation in the Emergency Department: current approach and future expectations

Atrial fibrillation (AF) is the most common cardiac dysrhythmia and occurs in 3.3%-10% of emergency admissions. It is frequently quoted for people over the age of 75, but the cases of AF in young subjects without structural heart disease are also increasing, therefore, leading to the evaluation of "lonely atrial fibrillation" as a new challenge for the clinician. The first diagnosis and treatment often occur in the emergency room and the emergency physician has therefore to evaluate the initial step towards the therapeutic decisions. Although international standard guidelines are available, AF treatment in the Emergency Department (ED) is still heterogeneous in terms of the management strategy chosen. There are two main strategies for the management of AF: rate and rhythm control. Moreover, antithrombotic treatment is pivotal in AF to prevent cardioembolic stroke and it is considered a primary objective after an accurate assessment of antithrombotic treatment risks and benefits. The introduction of innovative echocardiographic approach, directly in ED, seems to improve the management and risk stratification of patients with AF. This review aims to provide an overview about the current approach and the future expectations in the management of AF in ED. This manuscript represents a synopsis of the lectures on AF management in the ED of the Third Italian GREAT Network Congress, that was hold in Rome, 15-19 October 2012. We decided to use only the most relevant references for each contribution as suggested by each participant at this review.

A critical overview on ticagrelor in acute coronary syndromes

Until a few years ago, the mainstay of anti-platelet therapy in patients with acute coronary syndrome (ACS) was the combination of aspirin and clopidogrel, a P2Y12 receptor inhibitor. However, current clinical practice has now changed with the introduction of ticagrelor, a more potent cardiovascular drug than clopidogrel, without the limitations related to clopidogrel therapy. In this review, we provide a critical overview of ticagrelor in ACS, highlight the results with ticagrelor in several subgroups of patients and discuss the future trials.

Stress hyperglycaemia in patients with first myocardial infarction

OBJECTIVE

To investigate the incidence of stress hyperglycaemia at first acute myocardial infarction (MI) with ST-segment elevation, occurrence of stress hyperglycaemia as a manifestation of previously undiagnosed abnormal glucose tolerance (AGT), and its relation to stress hormone levels.

MATERIALS AND METHODS

  The population of this prospective cohort study consisted of 243 patients. On admission glucose, adrenaline, noradrenaline and cortisol levels were measured. Patients without previously diagnosed diabetes (n = 204) underwent an oral glucose tolerance test on day 3 of hospitalisation and 3 months after discharge.

RESULTS

Abnormal glucose tolerance at day 3 was observed in 92 (45.1%) patients without a previous diagnosis of diabetes mellitus and resolved after 3 months in 46 (50.0%) patients (p < 0.0001). Stress hyperglycaemia, defined as admission glycaemia ≥ 11.1 mmol/l, affected 34 (14.0%) study participants: 28 (54.9%) patients with diabetes vs. 3 (8.8%) subjects with newly detected impaired glucose intolerance (p < 0.00001) and 1 (2.2%) person with AGT at day 3 (p < 0.000001). Multivariable analysis identified elevated glycated haemoglobin (HbA(1c) ; p < 0.0000001), anterior MI (p < 0.05) and high admission cortisol concentration (p < 0.001), but not catecholamines, as independent predictors of stress hyperglycaemia. The receiver operating characteristic curve analysis revealed the optimal cut-off values of 8.2% for HbA(1c) and 47.7 μg/dl for admission cortisol with very good and sufficient diagnostic accuracies respectively.

CONCLUSIONS

  Newly detected AGT in patients with a first MI is transient in 50% of cases. Stress hyperglycaemia is a common finding in patients with a first MI with ST-segment elevation and diabetes mellitus, but is rarely observed in individuals with impaired glucose tolerance or transient AGT diagnosed during the acute phase of MI. The risk factors of stress hyperglycaemia occurrence include elevated HbA(1c) , anterior MI and high admission cortisol concentration.

Phenotyping vs. genotyping for prediction of clopidogrel efficacy and safety: the PEGASUS-PCI study

BACKGROUND

Prognostic values of genotyping and phenotyping for assessment of clopidogrel responsiveness have been shown in independent studies.

OBJECTIVES

To compare different assays for prediction of events during long-term follow-up.

METHODS

In this prospective cohort study polymorphisms of CYP2C19*2 and CYP2C19*17 alleles, vasodilator-stimulated phosphoprotein phosphorylation (VASP) assay, multiple electrode aggregometry (MEA), cone and platelet analyser (CPA) and platelet function analyser (PFA-100) were performed in 416 patients undergoing percutaneous coronary intervention. The rates of events were recorded during a 12-month follow-up.

RESULTS

Platelet aggregation by MEA predicted stent thrombosis (2.4%) better (c-index = 0.90; P < 0.001; sensitivity = 90%; specificity = 83%) than the VASP assay, CPA or PFA-100 (c-index < 0.70; P > 0.05; sensitivity < 70%; specificity < 70% for all) or even the CYP2C19*2 polymorphism (c-index < 0.56; P > 0.05; sensitivity = 30%; specificity = 71%). Survival analysis indicated that patients classified as poor responders by MEA had a substantially higher risk of developing stent thrombosis or MACE than clopidogrel responders (12.5% vs. 0.3%, P < 0.001, and 18.5% vs. 11.3%, P = 0.022, respectively), whereas poor metabolizers (CYP2C19*1/*2 or *2/*2 carriers) were not at increased risks (stent thrombosis, 2.7% vs. 2.5%, P > 0.05; MACE, 13.5% vs. 12.1%, P = 0.556). The incidence of major bleedings (2.6%) was numerically higher in patients with an enhanced vs. poor response to clopidogrel assessed by MEA (4% vs. 0%) or in ultra-metabolizers vs. regular metabolizers (CYP2C19*17/*17 vs. CYP2C19*1/*1; 9.5% vs. 2%). The classification tree analysis demonstrated that acute coronary syndrome at hospitalization and diabetes mellitus were the best discriminators for clopidogrel responder status.

CONCLUSIONS

 Phenotyping of platelet response to clopidogrel was a better predictor of stent thrombosis than genotyping.

Low-molecular-weight heparins vs. unfractionated heparin in the setting of percutaneous coronary intervention for ST-elevation myocardial infarction: a meta-analysis

BACKGROUND

The aim of the current study was to perform two separate meta-analyses of available studies comparing low-molecular-weight heparins (LMWHs) vs. unfractionated heparin (UFH) in ST-elevation myocardial infarction (STEMI) patients treated (i) with primary percutaneous coronary intervention (pPCI) or (ii) with PCI after thrombolysis.

METHODS

All-cause mortality was the pre-specified primary endpoint and major bleeding complications were recorded as the secondary endpoints. Relative risk (RR) with a 95% confidence interval (CI) and absolute risk reduction (ARR) were chosen as the effect measure.

RESULTS

Ten studies comprising 16,286 patients were included. The median follow-up was 2 months for the primary endpoint. Among LMWHs, enoxaparin was the compound most frequently used. In the pPCI group, LMWHs were associated with a reduction in mortality [RR (95% CI) = 0.51 (0.41-0.64), P < 0.001, ARR = 3%] and major bleeding [RR (95% CI) = 0.68 (0.49-0.94), P = 0.02, ARR = 2.0%] as compared with UFH. Conversely, no clear evidence of benefits with LWMHs was observed in the PCI group after thrombolysis. Meta-regression showed that patients with a higher baseline risk had greater benefits from LMWHs (r = 0.72, P = 0.02).

CONCLUSIONS

LMWHs were associated with greater efficacy and safety than UFH in STEMI patients treated with pPCI, with a significant relationship between risk profile and clinical benefits. Based on this meta-analysis, LMWHs may be considered as a preferred anticoagulant among STEMI patients undergoing pPCI.

Ischaemic and bleeding complications with new, compared to standard, ADP-antagonist regimens in acute coronary syndromes: a meta-analysis of randomized trials

BACKGROUND

Platelets play a pivotal role in the pathogenesis of acute coronary syndromes (ACS) and their inhibition remains a mainstay therapy in this setting. We aimed to perform a meta-analysis of randomized trials to evaluate the benefits of new oral antiplatelet regimens to block platelet ADP-receptors compared to standard-dose clopidogrel (300 mg loading dose followed by 75 mg/daily).

METHODS

We obtained results from all randomized trials enrolling patients with ACS. Primary endpoint was mortality. Secondary endpoints were myocardial infarction and definite in-stent thrombosis. Safety endpoint was the risk of major bleeding complications. We prespecified subanalyses according to new antiplatelet drugs (prasugrel/ticagrelor), high-dose clopidogrel (600 mg) and patients undergoing percutaneous coronary intervention.

RESULTS

A total of seven randomized trials were finally included in the meta-analysis (n = 58 591). We observed a significant reduction in mortality (2.9% vs. 3.4%, OR = 0.87, 95% CI 0.79-0.95, P = 0.002), recurrent myocardial infarction (4.2% vs. 5.2%, OR = 0.80, 95% CI 0.74-0.87, P < 0.0001), definite in-stent thrombosis (0.9% vs. 1.7%, OR = 0.52, 95% CI 0.43-0.63, P < 0.0001). The benefits in mortality and reinfarction were driven by the treatment with prasugrel or ticagrelor, without a significant difference in terms of major bleeding complications as compared to standard-dose clopidogrel (5% vs. 4.7%, OR = 1.06 95% CI 0.96-1.17, P = 0.25).

CONCLUSION

This meta-analysis showed that new oral antiplatelet regimens are associated with a significant reduction in mortality, reinfarction and in-stent thrombosis in ACS patients without an overall increase of major bleeding when treated with new antiplatelet drugs.

Early vs. delayed invasive strategy in patients with acute coronary syndromes without ST-segment elevation: a meta-analysis of randomized studies

Although early percutaneous coronary intervention has been demonstrated to reduce the risk of mortality in patients with non-ST-segment elevation acute coronary syndromes (NSTE-ACS), there are emerging conflicting data as to whether the catheterization needs to be done very early or whether it could be delayed while the patient receives medical therapy. The aim of the current study was to perform a meta-analysis of randomized controlled trials (RCTs) comparing early vs. delayed invasive strategies for NSTE-ACS patients. Medline/CENTRAL and the Web were searched for RCTs comparing early vs. delayed invasive strategies for NSTE-ACS patients. The primary endpoint was all cause mortality, whereas myocardial infarction (MI), coronary revascularizations and 30-day major bleeding complications were secondary end points. Fixed or random effects models were used based on statistical heterogeneity. As a sensitivity analysis, Bayesian random effects meta-analysis was performed in addition to the classical random effects meta-analysis. A total of 5 RCTs were finally included, enrolling 4155 patients. As compared with a delayed strategy, an early invasive approach did not significantly reduce the rates of death [odds ratio (OR) 95% confidence interval (95% CI) = 0.81 (95% CI 0.60-1.09), P = 0.17], MI [OR = 1.18 (95% CI 0.68-2.05), P = 0.55] or revascularizations [OR = 0.97 (0.77-1.24), P = 0.82]. There was a not significant trend toward fewer major bleeding complications for the early invasive approach [OR (95% CI) = 0.76 (0.55-1.04), P = 0.08]. The present meta-analysis shows that for NSTE-ACS patients a routine early invasive strategy does not significantly improve survival nor reduce MI and revascularization rates as compared with a delayed approach.

141 EFFECT OF ENVIRONMENTAL TEMPERATURE ON EMBRYO PRODUCTION AND CONCEPTION RATES IN BEEF AND DAIRY CATTLE

The aim of this study was to evaluate the effect of environmental temperature at the time of embryo collection and transfer on embryo quality and conception rates after transfer of fresh and frozen embryos. Purebred dairy (Holstein, Czech spotted cattle, n = 174) and beef (Charolais, Blonde d’Aquitaine, Piedmontese, Hereford, Limousin and Simmental; n = 72) donors were collected during 2005 to 2007. Donor cows received one application of PGF2α and superstimulation was initiated 9 to 11 days following estrus with pFSH (Folltropin-V; Bioniche Animal Health, Belleville, ON, Canada) given twice daily for 4 days. Prostaglandin2α was given on Day 3 of the superstimulation treatment. Donors were inseminated 3 times, with 1 unit of semen on Days 5 and 6 of treatment. Embryo recovery was carried out on Day 7 after insemination. The recipients were synchronized with PGF2α and embryos were transferred on Day 7 after estrus. The effect of temperature at the time of 246 embryo recoveries and 1338 transfers (fresh and frozen embryos) was analyzed using the GLM, assuming quasi-poisson and quasi-binomial error distribution by R software (www.r-project.org). We evaluated the total number of ova/embryos collected, embryo quality, and conception rates after transfer at the environmental temperatures shown below. Temperatures were divided into the following ranges: A) from –5 to 5°C; B) from 6 to 15°C; C) from 16 to 20°C; and D) over 20°C. The average temperature values were obtained from the Czech hydrometeorological institute and corresponded to the following seasons: winter (range A and B); spring (range B and C); summer (range C and D); fall (range C and B). Dairy cows were managed intensively in barns whereas beef cows were managed in barns during the winter and on pasture from April until October. In beef donors the mean number of total ova/embryos collected and transferable embryos were 9.1 ± 7.9 and 4.2 ± 4.5, respectively and no significant effect of temperature was detected (P > 0.05). In dairy donors the mean number of total ova/embryos collected and transferable embryos were 7.9 ± 6.0 and 4.9 ± 4.5, respectively and no significant effect of temperature was detected (P = 0.27). Conception rate was greatest (P < 0.001) in temperature range D (63.64%) compared with the other temperature ranges (A = 27.66%; B = 43.65%; C = 43.21%;) in beef cows and in the range C (65.31%) than in the other temperature ranges (A = 34.7%; B = 52.67%; D = 56.25%) in dairy cows. It was concluded that temperature at the time of embryo collection did not affect embryo production and quality. However, environmental temperature did have a significant effect on conception rates in both beef and dairy recipients. Nutritional status may also have contributed to the increased conception in beef cattle during warmer temperatures. However, the optimal period for conception in dairy cows was in temperature range from 16 to 20°C, because of the potential adverse effect of heat stress in high-yielding cows. Supported by MEYS CR MSM 2678846201, LA 330; NAZV 1B44034.

Percutaneous coronary intervention triggers a systemic inflammatory response in patients treated for in-stent restenosis -- comparison with stable and unstable angina

OBJECTIVE AND DESIGN

It is believed that the magnitude of the systemic inflammatory response induced by percutaneous coronary intervention (PCI) impacts on the long-term outcomes in patients with stable angina (SA) and unstable angina (UA). We aimed to determine whether an inflammatory response appears in in-stent restenosis (ISR) patients undergoing balloon angioplasty and to assess its pattern and magnitude in relation to SA and UA subjects.

SUBJECTS

80 patients (59 with SA, 10 with UA, 11 with ISR) were enrolled into the prospective study.

TREATMENT

SA and UA patients undergoing single vessel coronary balloon angioplasty followed by stenting versus ISR subjects in whom only balloon angioplasty was performed.

METHODS

C-reactive protein (CRP), serum amyloid A (SAA), tumor necrosis factor alpha (TNF-alpha) and interleukin 10 (IL-10) were measured in blood samples collected before and 6, 24 h and 1 month after the procedure.

RESULTS

A comparable pattern of inflammatory response in terms of CRP and SAA concentrations in subjects undergoing PCI due to ISR and SA was discovered while in unstable patients its magnitude was substantially higher. CRP and SAA levels increased significantly in each group with the peak value at 24 h and the baseline levels remarkably correlated with the highest markers' concentrations. In contrast, preprocedural TNF-alpha concentrations were higher in ISR group when compared with SA and UA patients. Additionally, in ISR group a twofold increase in their values of borderline significance at 6 h was noted. SA and UA subjects were found to have significantly lower TNF-alpha levels at 6 and 24 h after the intervention though the marker concentrations markedly increased with peak values at 1 month. The levels of IL-10 did not differ at any time point between the groups.

CONCLUSIONS

We suggest that PCI triggers a systemic inflammatory response in patients with ISR and considerable differences in its pattern when compared with SA and UA patients were demonstrated. Moreover, a high preprocedural TNF-alpha level and its increase provoked by PCI in the ISR group warrant the need for further investigation of its possible involvement in the restenosis process.

Echocardiographic morphometry of the right chambers of the heart in permanent cardiac pacing

Permanent cardiac pacing is a method of choice in the treatment of specific arrhythmias and conduction disturbances. Clinical studies show that cardiac performance diminished at the site of impulse spreading. It determines local hypotrophy below the position of the pacing lead (early electric activation) with hypertrophic changes in the opposite lying myocardium (late electric activation). It seems that morphological changes, especially research by intravital methods, so relevant in permanent pacing to today's invasive cardiologist, are not understood in full. In connection with this we decided, on the basis on the echocardiographic examination, to evaluate in detail the morphology of the right ventricle and atrium in patients with permanent pacing. Research was carried out on a group of 124 patients (68 males, 56 females) from 40-93 years of age (avg. 68 +/- 14 yrs): 86 patients had implanted pacemakers or AICD (group I), the control group consisted of 38 patients with other cardiac diseases without any pacemaker devices (group II). We measured echocardiographically the following diameters: end-diastolic and systolic diameters of the right ventricle/atrium in short and long axis, diameter of the tricuspid orifice valve and calculated area of the tricuspid orifice based on a special formula. Regarding the morphometric parameters of the right ventricle and right atrium, we confirmed that all diameters of group I were overshooting in correlation to group II. Those differences, such as RVd-short and -long, RVs-long, RVinflow, RA-long and -short, TRId, were statistically significant. Regarding the area of the tricuspid orifice (TRIa), we did not observe any changes in the two examined groups. We concluded that patients with implanted devices have changes in the morphometric parameters of the right ventricle, atrium and orifice, but they do not depend on the duration of pacemaker implantation.

Adjunctive stent implantation following directional coronary atherectomy in patients with coronary artery disease

OBJECTIVES

This prospective case-control study evaluated the acute and long-term results of stent implantation preceded by debulking of the plaque by means of directional coronary atherectomy.

BACKGROUND

In comparison with balloon angioplasty, intracoronary stenting produces a larger luminal diameter, maintains artery patency and reduces the incidence of restenosis. Optimal stent deployment is a pivotal factor for achieving the best results, but the bulk of the atherosclerotic plaque opposes stent expansion and may limit the success of the procedure. Debulking of the plaque may provide a better milieu for optimal stent deployment.

METHODS

Directional coronary atherectomy followed by a single Palmaz-Schatz stent implantation was attempted in 100 patients. The successes, complications and angiographic results of the combined procedure were evaluated both acutely and during follow-up. Matched patients undergoing successful Palmaz-Schatz stent implantation alone during the same period served as controls.

RESULTS

Atherectomy followed by stent implantation was performed in 94 patients with 98 lesions; periprocedural complications were observed in four cases. The stenosis diameter decreased from 76+/-9% at baseline to 30+/-13% after atherectomy (p < 0.0001), and 5+/-9% after stent implantation (p < 0.0001); it increased to 27+/-15% at 6-month angiography (p < 0.0001). During the 14+/-10 months of follow-up, none of the patients died or experienced myocardial infarction, but three patients underwent target lesion revascularization. The patients undergoing stent implantation alone achieved smaller acute gains, tended to have a higher late lumen loss, had a higher restenosis rate (30.5% vs. 6.8%, p < 0.0001) and showed a greater incidence of clinical events during follow-up (p < 0.0001).

CONCLUSIONS

Debulking atherosclerotic lesions by means of directional coronary atherectomy before stent implantation is a safe procedure with a high success rate and a low incidence of restenosis at follow-up.

[Evaluation of efficacy and mechanism of action of angioplasty and directed atherectomy assisted by intravascular ultrasonography]

Intravascular ultrasound (IVUS) is a unique method of coronary lumen visualization enabling also examination the structure of the artery wall. Aim of this study was to assess efficacy and mechanisms of action of balloon angioplasty (PTCA) and directional atherectomy by means of IVUS. IVUS examination was performed before and after mechanical revascularization procedure in 37 pts (DCA-19 pts, PTCA-18 pts). Both PTCA and DCA resulted in enlargement of the coronary artery lumen (2.29 +/- 1.19 mm2 vs 2.93 +/- 1.55 mm2) but, also external diameter of the vessel increased after the procedure (1.94 +/- 1.10 mm2 and 0.74 +/- 1.01 mm2 retrospectively). In 55.6% of cases after PTCA plaque rupture or artery wall dissection was observed, mainly in eccentric lesions (70%). IVUS allowed to recognize details of artery lumen and define efficiency of procedure. In about 15% cases decision to continue PTCA or DCA was made on the basis of IVUS images only. The mechanism in which PTCA modifies the artery lumen is diverse and depends on the structure of lesion. Factors possibly responsible for enlargement of the lumen are: stretching, squeezing and translocation of atheroma as well as cracking and dissections along the arterial wall. DCA effectiveness depends on the withdraw of the atheromatous deposit, however, in over one-half of cases also stretching has some effect.

Correlation between clinical and morphologic findings in unstable angina

This study was undertaken to verify the hypothesis that the discrepant findings in published reports on the prevalence of thrombus in unstable angina depend on the inclusion of different clinical subsets in the various studies. We therefore correlated the clinical characteristics of patients included under the label of unstable angina with the morphologic features assessed by coronary angiography and intravascular ultrasound, and with histopathologic findings of atherectomy specimens. Fifty-eight patients with unstable angina (class B of the Braunwald classification) undergoing coronary arteriography followed by either coronary angioplasty (n = 20) or directional coronary atherectomy (n = 38) were studied. Fifteen patients were in class IB and 43 were in class II to IIIB. Among these 43 patients with angina at rest, 28 had ST-segment elevation during pain, and 15 had ST-segment depression, and 26 developed negative T waves on the baseline electrocardiogram (ECG) as a result of prolonged or repeated episodes of resting chest pain. Intravascular ultrasound examination of the culprit lesion was performed in 43 patients before the interventional procedure, and histopathologic analysis of atherectomy specimens was performed in 38 patients. Complex lesion morphology by angiography was observed in 31 patients (53%) without any significant relation to various clinical subsets. Patients in Braunwald class IB had more calcific plaques than patients in class II to IIIB (p < 0.001). Among patients with angina at rest, those with negative T waves on the baseline ECG, as well as those with transient ST elevation during pain, had a significantly higher incidence of noncalcific lesions (p = 0.001 for both). Analysis of atherectomy specimens revealed acute coronary lesions (thrombus and/or intraplaque hemorrhage) in 18 patients (47%). The incidence of acute coronary lesions was significantly higher in patients with than without negative T waves on the baseline ECG (p = 0.005), and increased further when negative T waves were combined with ST elevation during pain (p = 0.001). Multivariate analysis revealed that the presence orf negative T waves on the baseline ECG was the only explanatory variable related to the presence of acute coronary lesions by histology (p = 0.03). Patient subsets included in the broad spectrum of unstable angina have different morphologic features and incidence of acute coronary lesions by histology. These data provide an explanation for the discrepant findings in published reports on the relevance of thrombus formation in the pathogenesis of unstable angina.

Influence of plaque composition on luminal gain after balloon angioplasty, directional atherectomy, and coronary stenting

This study was conducted to correlate the acute luminal enlargement achieved by three different nonsurgical revascularization procedures in 79 patients (32 treated by balloon angioplasty, 29 by directional atherectomy, and 18 by coronary stenting) with the morphologic characteristics of coronary plaques assessed by preprocedure intravascular ultrasound. The absolute luminal gain was 2.41 +/- 1.54 mm2 for balloon angioplasty, 3.17 +/- 1.8 mm2 for directional atherectomy, and 4.56 +/- 1.45 mm2 for coronary stenting (p = 0.00005). However, when luminal gain was corrected for the external vessel area (luminal gain index), such difference was no longer present (0.22 +/- 0.12 for balloon angioplasty, 0.24 +/- 0.15 for directional atherectomy, and 0.30 +/- 0.12 for coronary stenting, p = not significant). Concentric plaques treated by coronary stenting had a higher luminal gain index than eccentric plaques (p = 0.01). A comparison of the three devices showed that a similar luminal gain index was achieved in soft plaques, whereas coronary stenting was superior to directional atherectomy (0.41 +/- 0.10 vs 0.20 +/- 0.09, p = 0.002) and balloon angioplasty (0.41 +/- 0.10 vs 0.19 +/- 0.08, p = 0.0005) in concentric plaques. Coronary stenting also induced a greater luminal gain index than directional atherectomy in calcific plaques (0.30 +/- 0.11 vs 0.18 +/- 0.09, p = 0.04). In conclusion, these data show that plaque morphology assessed by preprocedure intracoronary ultrasound influences the acute luminal enlargement achieved by different coronary interventions. The knowledge of plaque composition may be useful in guiding the choice of the device to be used to obtain a larger acute luminal gain.

[Advantages and controversies regarding physiologic electrostimulation of the heart in sinus node disease]

Pacing mode in sinus node disease (SND) is one of controversies in cardiac pacing. We evaluated atrial pacing mode (AAI) in SND patients (pts). Between 1985 and 1994 AAI pacemaker was inserted in 179 pts due to symptomatic SND of varied etiology.

RESULTS

The majority of pts (91.6%) were free from syncopal episodes after AAI implantation, in 15 pts (8.4%) syncopes were occasionally observed due to disturbances in pacemaker function, AVB III degrees, vaso-vagal syndrome, orthostatic hypotonia or atherosclerotic insufficiency of the cerebral circulation. In 49 (51%) out of 96 pts with brady-tachy syndrome (BTS), episodes of supraventricular tachyarrhythmia were not observed after AAI insertion and in the majority of the remaining pts the frequency of the episodes decreased significantly. Chronic atrial fibrillation developed in 5 (5.2%) pts. In some of the pts the symptoms related to chronic heart failure decreased or disappeared. A reoperation was performed in 44 (24%) pts due to electrode dislocation or fracture, atrio-ventricular conduction disturbances, an increase in pacing threshold or due to local infections. During the follow-up period 13 (7.3%) pts died of reasons unrelated to cardiac pacing therapy.

CONCLUSION

In the majority of SND pts AAI pacing mode prevents from syncopal episodes caused by sinus node disfunction. It decreases the symptoms of heart failure in SND pts and stabilizes the sinus rhythm in the majority of BTS pts. Complications accompanying AAI do not post a major threat for the pts and can be easily resolved. They should by no means discourage from AAI implantation in SND.

Influence of plaque morphology on the mechanism of luminal enlargement after directional coronary atherectomy and balloon angioplasty

OBJECTIVE

To relate the mechanism of luminal gain after directional atherectomy and balloon angioplasty to the morphological characteristics of the coronary lesions, assessed by intravascular ultrasound imaging.

DESIGN

Intravascular ultrasound imaging was performed before and after the revascularisation procedure to assess the contribution of wall stretching and plaque reduction in luminal gain.

SUBJECTS

32 patients undergoing balloon angioplasty and 29 undergoing directional coronary atherectomy.

MAIN RESULTS

The main luminal area in vessels treated by balloon angioplasty increased from 1.51 (SD 0.30) to 3.91 (1.09) mm2 (P < 0.0001) with a concomitant increase in total vessel area from 11.44 (2.73) to 13.07 (2.83) mm2 (P < 0.0001). Therefore stretching of the vessel wall accounted for 68% of the luminal gain while plaque reduction accounted for the remaining 32%. This mechanism ranged from 45% in non-calcific plaques to 81% in echogenic plaques. The main luminal area in vessels treated by directional atherectomy increased from 1.49 (0.32) to 4.68 (1.73) mm2 (P < 0.0001), with a concomitant increase of total vessel area from 13.61 (4.67) to 15.2 (4.04) mm2 (P = 0.006). Thus stretching of the vessel wall accounted for 49% of the luminal area gain and plaque reduction for the remaining 51%. The presence of calcium influenced the relative contribution of these two mechanisms to the final luminal gain after directional atherectomy, since in calcific plaques stretching of the vessel wall accounted for only 9% of the luminal gain as compared to 56% in non-calcific plaques. After balloon angioplasty there was greater evidence of coronary dissections (32% v 3% after directional atherectomy, P < 0.01) and plaque fissure (60% v 0%, P < 0.01). Plaque fissure was more frequently seen in echolucent and concentric lesions, whereas dissections prevailed in echogenic and eccentric lesions.

CONCLUSIONS

Intravascular ultrasound imaging may allow the assessment of acute changes in lumen and vessel wall after revascularisation procedures, and help in evaluating the potential effect of the structure and morphology of coronary lesions on the mechanism of luminal enlargement.

Assessment of left ventricular function by isometric handgrip exercise after thrombolysis in patients with refractory unstable angina

The handgrip test has been proposed for the evaluation of the hemodynamic reserve in patients with coronary artery disease and to quantitate the impairment of left ventricular (LV) function. The present study was designed to evaluate the effect of thrombolytic therapy in patients with refractory unstable angina in order to test the hypothesis that a reduction in intracoronary thrombosis could ameliorate their hemodynamic response to the handgrip test. During left heart catheterization, 20 patients with refractory unstable angina of recent onset performed a handgrip test before (HG1) and 24-72 hours after (HG2) being randomized to receive recombinant tissue-type plasminogen activator or placebo, according to a double-blind parallel group design. HG1 induced an increase in heart rate (p < 0.001), in systolic pressure (p < 0.001), and a reduction in ejection fraction (p < 0.05). Changes in LV end-diastolic pressure during baseline handgrip were highly different in individual patients, resulting in a trend toward an increase. Similarly, a different individual response was observed in the behavior of the isovolumetric and relaxation indices. In comparison with HG1, no difference was detected during HG2 in the 2 treatment groups with respect to changes in LV volumes, ejection fraction, LV systolic and diastolic pressures, +dP/dt, (dP/dt)/P, -dP/dt, and tau index. In patients with refractory unstable angina of recent onset, the handgrip test performed before and after thrombolysis did not prove to be useful in assessing directional changes of LV performance, mainly because of the different individual response to the baseline handgrip test.

Effects of coronary angioplasty on left ventricular function

It is well known that myocardial revascularization after successful coronary bypass surgery results in improved left ventricular function. Coronary angioplasty also results in successful revascularization, favorably affecting both stunned and hibernating myocardium. We studied 22 patients with chronic stable angina who underwent successful angioplasty for an isolated narrowing of the proximal or midportion of the left anterior descending artery. These patients also performed isometric exercises before and after angioplasty, which can be used to characterize left ventricular function. Revascularization after angioplasty induced an immediate improvement in left ventricular function in those patients with dysfunction secondary to hibernating myocardium. Further studies are needed to assess the possibility of the myocardial stunning phenomenon occurring after angioplasty in those patients without left ventricular improvement.

[Left ventricular stroke volume in individuals with dual chamber pacemaker (DDD). Effect of atrioventricular delay]

Programming of atrioventricular delay in patients with dual chamber pacemaker is very important for left ventricular filling and has a consequence for its stroke volume. The aim of this study was to evaluate the influence of atrioventricular delay for left ventricular stroke volume during pacing at two different rates. The study was performed in 36 patients with DDD pacemaker aged from 30 to 81 years, mean 56.1 +/- 14.6. Using Doppler echocardiography we have assessed left ventricular stroke volume during two pacing rates (70 and 100 ppm) with four atrioventricular delays (100, 150, 200 and 250 ms). We have found statistically significant difference between stroke volume with various atrioventricular delays. During pacing rate of 70 ppm the maximal difference was 19% and 15% during 100 ppm. Comparing both pacing rates the distributions of hemodynamically optimal atrioventricular delays was also significantly different. The best atrioventricular delay from the hemodynamic point of view was 36 ms longer during 70 ppm of pacing rate than during 100 ppm (p = 0.0009). The most often optimal delay at 70 ppm was 190-200 ms, and the rarest optimal delay was 90-100 ms; during 100 ppm pacing respectively: 140-150 ms and 240-250 ms. We have observed considerable personal variability in the hemodynamic response for atrioventricular delay changing as well as in the hemodynamically optimal values of this parameter during both pacing rates.

CONCLUSIONS

1. Atrioventricular delay programming has significant influence on left ventricular stroke volume. 2. Programming of atrioventricular delay should be performed individually in every patient because of personal variability of optimal values of this parameter.(ABSTRACT TRUNCATED AT 250 WORDS)

[The evaluation of intracoronary stents by intravascular echography]

BACKGROUND

Intravascular ultrasound (IVUS) provides high resolution of vessel wall pathoanatomy, and because of the highly reflective nature of stent surfaces, can evaluate alterations in stent geometry.

METHODS

This study was performed to assess, by IVUS stent, expansion patterns in patients undergoing implantation of metallic coronary stents, and the mechanisms of restenosis in those patients. Twenty-five patients were studied: 9 pts acutely and 16 pts at routine follow-up 5-8 months after Palmaz-Schatz stent placement. The images recorded by IVUS (25 Mhz 3.9F catheter Intertherapy Inc. California) were quantitatively analyzed for: luminal diameter (LD), luminal cross-sectional area (LA), cross-sectional diameter (SD) and area (SA), comprised by the stent struts. We used quantitative coronary angiography (QCA) (Image Comm System) to measure lumen diameter (LD) and luminal cross-sectional area (LA) in patients in whom IVUS was not performed at the moment of stent placement. These values were considered reference values of LD and LA of the stent at follow-up.

RESULTS

During follow-up, patients showed a reduction of vessel lumen LD (2.09 +/- 0.17 mm) measured by IVUS, versus baseline LD (2.87 +/- 0.39 mm) measured by QCA. SD (2.76 +/- 0.31 mm) and SA (6.30 +/- 1.24 mm2) were unchanged in comparison with LD (2.87 +/- 0.39 mm) and LA (6.47 +/- 1.77 mm2) measured by QCA at the time of stent implantation.

CONCLUSIONS

These data suggest that the mechanism of restenosis is due to intimal proliferation rather than stent collapse.

[Complications associated with use of atrial electrodes]

The higher complication rate with atrial than ventricular leads make the physiological mode of pacing less popular. The aim of this study was to assess the complications associated with atrial leads. Between July 1985 and December 1991 we inserted 174 atrial leads in 165 patients (pts) with sick sinus syndrome or/and a-v block (AAI and DDD system respectively). A variety of different types of unipolar leads have been used: passive fixation simple or J shaped with the porous tip of vitreus-carbon (n = 49) and platinum-iridium (n = 78) or polished tip of Elgiloy (n = 18), active fixation (n = 29). The leads were manufactured by Siemens-Elema, CPI, Biotronik, Medtronic and Vitatron. All leads have similar acute electrical characteristics. The mean follow-up period lasted 28 months (12-83) until June 1992. We observed the following complications: displacement of electrode tip in 16 pts (9.7%), the disturbances of sensing in 10 pts (6%), 3rd degree of a-v block in 6 pts (5.4%) of 111 pts with AAI pacing, the exit-block in 3 pts (1.8%), suppuration in 3 pts (1.8%) in pacemaker area, various in 1 pt (0.6%). Total complication rate, which required reoperation was 20.6%. Complications associated with atrial leads implantation are not dangerous, may be easily treated and should not limit the indication for physiological pacing.

Influence of elastic recoil on restenosis after successful coronary angioplasty in unstable angina pectoris

The elastic behavior of the dilated coronary vessel has been reported to affect the immediate results of coronary angioplasty. To determine whether elastic recoil may also influence the long-term restenosis process, 98 consecutive patients with unstable angina and 1-vessel disease were studied. An automated coronary quantitative program was used for the assessment of balloon and coronary luminal diameters. Elastic recoil was defined as the percent reduction between minimal balloon diameter at the highest inflation pressure and minimal lesion diameter immediately after coronary angioplasty. Follow-up coronary arteriography was performed 8 to 12 months after the procedure in all patients. The mean elastic recoil averaged 17.7 +/- 16% and was correlated to the degree of residual stenosis immediately after coronary angioplasty (r = 0.64; p < 0.001). Restenosis, defined as > 50% diameter stenosis at follow-up, developed in 53 patients (54%). There was no correlation between the degree of elastic recoil and the changes in minimal lesion diameter observed during follow-up, whereas a positive correlation between the amount of elastic recoil and the incidence of restenosis was documented (r = 0.84; p < 0.05). Thus, the elastic properties of the dilated vessel do not influence the active process of restenosis. However, because elastic recoil negatively influences the initial results of angioplasty, it is more likely that further reductions in lumen diameter during follow-up can reach a threshold of obstruction considered critical for a binary definition of restenosis.

Atrioventricular conduction disturbances in patients with sinoatrial node disease and atrial pacing

In sinoatrial node disease (SND) atrial pacing may be limited by progression of AV block. The incidence of AV block after AAI systems implantation range, according to various authors, from 0% to 12%. The aim of this study was to examine the AV conduction disturbances that forced a change in the mode of pacing in patients with AAI pacemakers. The information was collected retrospectively from a cohort of 122 patients. The follow-up period ranged from 5 to 83 months (mean = 35). Among these patients there were 37 with sinus bradycardia and 85 with bradycardia-tachycardia syndrome. Their mean age was 63 years. Before AAI pacemaker insertion, all patients had normal AV conduction on 12-lead ECG, and all but five had a Wenckebach cycle length shorter than 500 msec. Seven out of these 122 patients (5.7%) developed symptomatic conduction disturbances (second-degree type I AV block in five, second degree type II AV block in one, and third-degree AV block in one), necessitating a change from AAI to another mode of pacing. We conclude that progression of AV block after atrial pacemaker implantation in patients with SND is infrequent and mild in the majority of cases. Intraventricular disturbances such as left anterior hemiblock represent contraindication to AAI pacing particularly in patients who may be in need of antiarrhythmic drugs.

[Effect of atrio-ventricular conduction on the appearance of supraventricular arrhythmia and thrombotic complications in patients with chronic stimulation of cardiac ventricles in sick sinus syndrome]

Two hundred three patients with sick sinus node disease were treated with continuous ventricular stimulation between 1981 and 1985. To 1988, 168 patients aged between 26 and 88 years were followed-up for 5.1 years on the average. All these patients were divided into two groups: I (93 patients) with sinusal bradycardia, and group II (93 patients) with brady-tachycardia. Ventriculo-atrial conduction was seen in 82.61% of patients of group I in whom the implantation of electric stimulator produced the attacks of atrial fibrillation, and in 44.23% of patients without such attacks (p < 0.01); in 80.77% of patients of group II in whom atrial fibrillation became stable with time, and in 50.57% with intermittent atrial fibrillation (p < 0.01) ventriculo-atrial conduction was noted. It may be concluded, that the presence of ventriculo-atrial conduction in patients with prolonged stimulation of the cardiac ventricles favor the occurrence and stabilization of the paroxysmal atrial fibrillation and thrombotic complications.

[Transesophageal stimulation of the left cardiac atrium in treatment of atrial flutter]

Transesophageal stimulation of the left cardiac atrium in the treatment of paroxysmal atrial flutter was assessed. An attempt of such a therapy in paroxysmal atrial flutter involved 20 patients. Cardiac atrium was stimulated with overdrive technique, with single or pair of stimuli and multiple impulses of various frequency and duration. Reversal to sinus rhythm was achieved in 10 patients (in 3 out of them through phase of atrial fibrillation transitory). Results confirm therapeutical value of the transesophageal stimulation of the left cardiac atrium in atrial flutter.

Transesophageal atrial pacing complications in patients suspected of tachy-brady syndrome

The clinical effects of transesophageal atrial pacing (TAP) were assessed in 308 patients. Indications for TAP included evaluation for pacemaker implantation in patients suspected of sinus node dysfunction and determination of the suitable type of pacemaker. Most patients underwent program stimulation including rapid as well as burst stimulation. In one patient, following the study, cerebral arterial embolism occurred, most likely secondary to an induced arrhythmia. That was the only single case of permanent consequences following TAP. Additionally, one patient was accidentally stimulated in the ventricle using low voltage electric current that induced ventricular fibrillation. This was promptly reversed with defibrillation. Twenty-six patients in whom an arrhythmia was previously induced, required medical therapy, two of whom required cardioversion, and 24 required drug therapy, subsequent to clinical intolerance of the arrhythmia. No lethal complications occurred.

Left atrial size and wall motion in patients with permanent ventricular and atrial pacing

It is well known that during permanent ventricular pacing atrial arrhythmias and embolic complications occur much more frequently in comparison to permanent atrial or sequential pacing. Hemodynamic disturbances caused by ventriculoatrial conduction (VAC) are thought to be responsible for those complications. The aim of this study was to compare the left atrial size and its wall motion in three groups of patients with sick sinus syndrome. Group 1: 58 patients with VVI pacing and VAC observed (22 males, 36 females, aged 31-86, mean 62.3). Group 2: 43 patients with primary AAI pacing (13 males, 30 females, aged 27-74, mean 57.8). Group 3: 13 patients with AAI or DDD replacing the primary VVI mode due to pacemaker syndrome and/or heart failure, all with VAC present during VVI pacing (7 males, 6 females, aged 26-80, mean 59.8). Two-dimensional/M-mode echocardiography was performed in all these patients. In group 1 mean diastolic as well as mean systolic atrial diameters were significantly greater (P less than 0.005) and wall motion significantly smaller (P less than 0.005) in comparison to the other groups. Left atrial wall motion amounted to only 7.4% of the mean diastolic diameter in this group. Mean left atrial diastolic and systolic diameters and wall motion in patients with pacemakers preserving atrioventricular synchrony (group 2 and group 3) were almost identical and wall motion amounted to about 22% of the diastolic diameter in both these groups. We conclude that ventriculoatrial conduction leads to significant enlargement of left atrium and to the atrial wall-motion decrease. This predisposes to arrhythmias and embolic complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Transesophageal programmed atrial pacing as a method of selecting patients with sick sinus syndrome for permanent atrial pacing

Many recent studies have shown transesophageal programmed atrial pacing (TP) as a very practical, safe and convenient way for assessment of sinus node function and AV conduction. On the other hand, permanent atrial pacing is known to be superior to ventricular pacing due to arrhythmogenic and hemodynamic reasons. This is the reason why we decided to use TP as a method of choosing patients with sick sinus syndrome (SSS) for permanent atrial pacing. Sixty-three patients with symptomatic (58) and asymptomatic (5) SSS in a variety of clinical situations were examined in this way. The following electrophysiological features were examined: sinus cycle length, sinus node recovery time as well as corrected time, secondary pause after overdrive stimulation, sinoatrial conduction time, Wenckebach point, induction of supraventricular arrhythmias by S1, S2, S3 programmed stimulation and burst pacing. Patients with abnormal parameters were examined once more after intravenous atropine 0.2 mg/kg to evaluate parasympathetic component. Standard 12-lead ECG was performed in all, and Holter monitoring in most of patients. Twenty-six patients were candidates for permanent AAI pacing. Failures occurred in eight patients usually due to low P wave amplitude and electrode instability. Eighteen patients received AAI pacing systems: eight with brady-tachycardia syndrome, nine with bradyarrhythmia and one with sinoatrial block. In the follow-up of 5-28 months in one patient occurred high degree AV block (II degree) during digitalis therapy. Reduction of doses made this block disappear. Examination of Wenckebach point and possibility of inducation of supraventricular tachyarrhythmias in cases of atrial overexcitability are particularly useful in selecting patients for AAI pacing.

Cell-mediated immune reactions in measles

Cell-mediated reactions in measles cases, in direct contacts and healthy children were tested. Indices of phytohaemagglutinin-stimulated blastic transformation and leukocyte migration inhibition were evaluated. Positive reactions were found in the first and second weeks after manifestation of clinical symptoms. The application of glucocorticosteroids in clinical complications resulted in delayed and reduced leukocyte migration inhibition. Studies on seronegative contacts suggested that positive cell-mediated reactions may appear before manifestation of clinical symptoms.