人血清心脏肌钙蛋白Ⅰ定量和定性测定比较

目的比较心脏肌钙蛋白Ⅰ(cTnI)定量和定性测定方法,评价其临床检测意义.方法应用酶联免疫吸附试验(ELISA)和固相层析免疫法(敏感阈值0.2ng/ml)对517份人血清标本分别进行cTnI定量和定性测定.结果定性分析cTnI阴性组、弱阳性组、阳性组和强阳性组其定量测定cTnI平均浓度分别为0.195、0.658、3.580和53.730ng/ml.两法总符合率为94.39(488/517),相对特异性91.35%(169/185),相对敏感性96.08%(319/332).固相层析免疫法18次重复测定四组已知浓度标本总符合率均100%;ELISA法测定结果变异系数在10%左右,所测范围可由1×10-2mg/ml至1×102ng/ml,测定范围线性关系良好.结论固相层析免疫法和ELISA法测定cTnI,两法结果较为符合,均有较好的准确度.前者稳定性较好,且操作更为简便快速,但对病情和疗效的观察有一定的限制.ELISA法检测结果明确,测定范围广,有助于病情和疗效观察,但精确度稍差.认为两法用于cTnI临床检测各有其长处,须把好试剂质量关和注重科学性.     

快速全血心肌肌钙蛋白Ⅰ检测床边诊断急性心肌梗死

AMI组80例发病后12h内入院。入院后即刻、4、8、24、48、168h采静脉血用固相层析免疫分析技术定性检测心肌肌钙蛋白(cTnI)。结果:入院后即刻cTnI阳性率95％,其余各时点阳性率均100％。心衰组30例,非心脏病组30例各时点cTnI均阴性。cTnI     

时间分辨荧光免疫分析法和酶联免疫吸附实验法测定乙型肝炎病毒大蛋白的方法学比较

目的对时间分辨荧光免疫分析(time-resolved fluoroimmunoassay,TRFIA)和酶联免疫吸附实验(enzyme-linked immunosorbent assay,ELISA)检测乙型肝炎患者血清中病毒大蛋白(hepatitis B virus large surface protein,HBV-LP)进行方法学比较。方法收集30例正常体检血清标本作为阴性对照和150例慢性乙型肝炎患者血清标本,利用ELISA法检测HBV-LP,将其中70例阳性标本作为阳性样本,70例阴性标本作为阴性样本,再分别采用TRFIA法检测HBV-LP,对二者的灵敏度、特异度、一致性、检测线性范围、精密度、相关性及两种试剂盒的稳定性进行比较。其中TRFIA与ELISA结果不一致的12例标本采用PCR法进行验证。结果TRFIA检测HBV-LP的最小测定值为0.1 ng/ml,ELISA检测HBV-LP的最小测定值为2.5 ng/ml,二者的特异度均为100%。TRFIA和ELISA检测HBV-LP的Kappa值为0.83。12例ELISA和TRFIA检测不一致的标本,经PCR验证后有10例HBV DNA103拷贝数。TRFIA试剂检测的线性范围在0.625~10 252 ng/ml之间,ELISA试剂盒检测的线性范围在5~1 281.6 ng/ml。TRFIA法检测高、中、低3个浓度水平的批内CV平均为6.10%,ELISA法的批内CV平均为8.98%。TRFIA批间CV平均为6.91%,ELISA的批间CV平均为10.45%。TRFIA试剂盒的结合下降率为6.61%,ELISA试剂盒的结合下降率为23.59%。结论 TRFIA与ELISA具有高度的一致性,但是两者相比,前者有更高的灵敏度和精密度,且TRFIA试剂盒的稳定性更好。     

cTnI自身抗体对两种cTnI检测方法检测结果的影响

目的:比较心肌肌钙蛋白I(cTnI)抗体结合位点不同的两种免疫分析仪检测cTnI的差异,观察cTnI自身抗体对急性心肌梗死(AMI)患者cTnI检测结果的影响。方法:采用AQT90快速免疫分析仪的时间分辨荧光免疫法(2个捕获cTnI抗体位点之一处于cTnI分子稳定区中间片断之外,不受cTnI自身抗体干扰,总的来说受cT-nI自身抗体干扰较少)和Centaur CP全自动免疫系统的化学发光法(2个捕获cTnI抗体位点都处于cTnI分子稳定区中间片断,受cTnI自身抗体干扰较多),分别对36例AMI患者血浆中cTnI的含量进行检测,并以酶联免疫吸附法(ELISA)对这些患者血浆cTnI自身抗体进行检测。结果:36例AMI患者AQT分析仪cTnI测定值(2.492±5.91μg/L)高于CP分析仪的(1.934±6.06μg/L),但不显著(P>0.05)。按两种分析仪测定值的差异分AQT>CP组(20例),和AQTCP组的cTnI自身抗体浓度(2465.0±1706.4)pg/ml,AQT的cTnI测值为(4.64±7.97)μg/L,高于CP测值(3.70±8.48),但P>0.05;而AQTCP组,P<0.001,AQT仪,CP仪的cTnI测值分别为(0.59±0.44)μg/L,(0.68±0.54)μg/L,二者非常接近,无显著差异(P>0.05)。结论:结果说明cTnI自身抗体浓度对于cTnI测定值有显著影响,于自身抗体浓度高时,AQT法受自身抗体浓度影响小,其cTnI测定值高于CP仪的cTnI测定值;于自身抗体浓度不高时,两种仪器测定的cTnI值非常接近,无显著差异。     

ABC-ELISA检测喜马拉雅旱獭鼠疫FI抗体的研究

用ABC-ELISA和常规ELISA检测了19份血凝阳性喜马拉雅旱獭(Marmota himalayana)血清和48份血凝阴性喜马拉雅旱獭血清及247份近年采自疫区的该旱獭血清,比较了两法的敏感性与特异性。两法的阳性、阴性符合率均为100％,但检测阳性血清的OD均值ABC-ELISA法明显地比常规ELISA法高(P<0.01)。ABC-ELISA与常规ELISA法对疫区血清标本的阳性检出率分别为9.7％与8.1%,后者出现1.6％的漏检率,滴度也显著低于前者(P<0.01)。表明ABC-ELISA用于检测旱獭鼠疫FI抗体可明显提高ELISA法的敏感性,且能保持良好的特异性。     

联合检测hs-CRP、cTnI和心肌酶谱在诊断儿科感染性疾病的应用

目的:探讨超敏C-反应蛋白(hs-CRP)、肌钙蛋白I(cTnI)和心肌酶谱联合检测在儿科感染性疾病鉴别诊断中的意义。方法:应用全自动化学发光免疫分析仪和全自动生化分析仪对3组研究对象血清hs-CRP、cTnI、肌酸激酶(CK)、肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH)和α-羟丁酸脱氢酶(α-HBDH)分别进行测定,并做统计学处理。结果:hs-CRP在细菌感染组中(18.27±3.90)mg/L显著高于病毒组(5.56±0.60)mg/L和健康对照组(4.02±0.60)mg/L(P0.05);cTnI在细菌组中(0.030±0.010)ng/ml显著低于病毒感染组(0.126±0.040)ng/ml(P0.05),但高于健康对照组(0.022±0.010)ng/ml(P0.05);CK、CK-MB、LDH和α-HBDH在细菌感染组中显著低于病毒感染组(P0.05),但高于健康对照组(P0.05)。结论:多项生化标志物联合检测综合判断,可弥补单项检测的不足,有利于感染性疾病患儿鉴别诊断,避免误诊而延误治疗。     

血清肌钙蛋白I、肌酸激酶同工酶对急性心肌梗死诊断价值的对比研究

目的：对比研究血清肌钙蛋白I(cTnI)、肌酸激酶同工酶（CK-MB）对急心肌梗死（AMI）的诊断价值。方法：采用化学发光法定量检测17例AMI、14例不稳定性心绞痛（UA）、9例陈旧性心肌梗死（OMI）患血清中的cTnI及CK-MB。结果：17例AMI患cTnI浓度均大于1.5ng/ml，11例UA及9例OMI患cTnI浓度小于1.5ng/ml，3例UA患大于1.5mg/ml。13例AMI、5例UA和1例OMI患CK-MB浓度大于5.0ng/ml，其余患CK-MB浓度均小于5.0ng/ml。CTnI诊断AMI的敏感性为100％，特异性为86.96％，阳性预测价值为85％，阴性预测价值为100％，正确率为92.5％；CK-MB诊断AMI的敏感性为76.47％，特异性为73.91％，阳性预测价值为68.42％，阴性预测价值为80.95％，正确率为75％。结论：cTnI对急性心肌梗死的诊断价值优于CK-MB。     

心肌肌钙蛋白I在不稳定型心绞痛患者中的应用价值

目的：探讨心肌肌钙蛋白I（cTnl)检测在不稳定型绞痛患中的临床应用价值。方法：对80例不稳定型心绞痛（UAP）患进行临床Braunwald分级,固相层析免疫法测定血清cTnI,酶学法测定肌酸磷酸激酶（CK）及其同功酶（CK－MB）,并观察住院期间心脏事件发生率。结果：80例UAP患中22例（27．5％）血清cTnI检测呈弱阳性或阳性,而CK－MB仅2例（2．5％）升高（P＝0．0001）。cTnI阳性组（22例）与阴性组（58例）之间临床除Braunwald分级存在差异（77．3％比48．3％,P＝0．02）外,其他均无差异。住院期间发生心脏事件率在cTnI阳性组较阴性组明显增高（40．9％比6．9％,P＝0．007）,多元logistic回归分析发现,cTnI是预测不稳定型心绞痛患住院期间心脏事件的最主要独立危险因素。结论：心肌肌钙蛋白I是反映心肌细胞损伤较灵敏、较特异的指标,是判断不稳定型心绞痛患近期预后的最主要独立预测因素。     

射频消融后心脏肌钙蛋白Ⅰ测定与心肌损伤的关系

采用固相层析免疫分析技术对31例因阵发性室上性心动过速、房性心动过速及室性心动过速接受射频消融（RFCA）治疗者测定其术后血清心脏肌钙蛋白I（cTnI）。结果显示，RFCA术后cTnI弱阳性率51．61％、阳性率16．13％；cTnI阳性组累积放电能量（19411．94±2251．74W／s）明显高于cTnI阴性组（8601．11±1791．88W／s）（P＜0．01）；心室放电组cTnI阳性率（88．2％）明显高于心房放电组（42．8％）（P＜0．05）。提示RFCA对心肌有轻微损伤，影响其损伤程度的因素有累积放电能量和放电部位。     

巨片形吸虫病快速诊断胶体金免疫层析试条的研制与评价

目的建立快速、简便诊断巨片形吸虫病的胶体金免疫层析试条方法。方法提取巨片形吸虫总RNA,通过RT-PCR获得FgCL1-YN基因片段,并克隆入pET28a(+)表达载体,异丙基-β-D-硫代半乳糖苷(IPTG)诱导表达得到重组蛋白(r FgCL1-YN);将r FgCL1-YN和羊抗鼠IgG抗体分别包被于硝酸纤维素膜的适宜位置作为检测带和质控带,以胶体金标记抗人IgG4抗体的鼠单抗作为检测试剂,制备检测特异性IgG4型抗体的免疫层析试条。用该试条检测巨片形吸虫病患者(30份)、日本血吸虫病患者(15份)以及健康人(32份)血清,评价其诊断价值,同时用ELISA法进行平行检测作为对照。结果试条检测法的敏感性为100%(30/30),特异性为97.9%(46/47),总体符合率为98.7%(76/77)。ELISA法检测的敏感性、特异性和总体符合率分别100%(30/30)、100%(47/47)和100%(77/77)。试条法与ELISA法的敏感性、特异性和总体符合率,经四格表确切概率法检验,P值分别为1、0.5和0.5,全部大于0.05。显示,试条法与ELISA法检测巨片形吸虫病患者血清的结果高度一致。另外,试条法的检测时间为10min,血清用量低于10μL,且具较高的敏感度。结论以r FgCL1-YN建立的快速诊断胶体金免疫层析试条,检测巨片形吸虫病具有较高的诊断价值。     

Utility of Cardiac Troponin to Predict Drug Overdose Mortality

Drug overdose is now the leading cause of injury-related mortality in the USA, but the prognostic utility of cardiac biomarkers is unknown. We investigated whether serum cardiac troponin I (cTnI) was associated with overdose mortality. This prospective observational cohort studied adults with suspected acute drug overdose at two university hospital emergency departments (ED) over 3 years. The endpoint was in-hospital mortality, which was used to determine test characteristics of initial/peak cTnI. There were 437 overdoses analyzed, of whom there were 20 (4.6 %) deaths. Mean initial cTnI was significantly associated with mortality (1.2 vs. 0.06 ng/mL, p < 0.001), and the ROC curve revealed excellent cTnI prediction of mortality (AUC 0.87, CI 0.76–0.98). Test characteristics for initial cTnI (90 % specificity, 99 % negative predictive value) were better than peak cTnI (88.2 % specificity, 99.2 % negative predictive value), and initial cTnI was normal in only one death out of the entire cohort (1/437, CI 0.1–1.4 %). Initial cTnI results were highly associated with drug overdose mortality. Future research should focus on high-risk overdose features to optimize strategies for utilization of cTnI as part of the routine ED evaluation for acute drug overdose.     

血清心肌肌钙蛋白Ⅰ判断病毒性心肌炎炎性损伤及预后的探讨

目的探讨心肌肌钙蛋白I(cTnI)判断急性病毒性心肌炎炎性损伤程度及预后。方法采用抗人cTnI单抗,应用酶联免疫法测定52例急性病毒性心肌炎患者血清cTnI,同时作肌酸磷酸激酶及其同工酶(CK,CK-MB)检测,血清cTnI>7μg／L为阳性。第1次cTnI阳性者第2次复查仍然阳性者归入cTnI持续阳性组(18例),复查cTnI阴性者归入cTnI阴性组(20例)。结果cTnI阴性组与cTnI持续阳性组临床症状好转率、心律失常治愈率比较均有极显著性差异(P<0．01)。cTnI持续阳性组中,有2例患者发展为心肌炎后心肌病。52例急性病毒性心肌炎患者中第1次检测cTnI有38例患者cTnI阳性(73．1％),有3例CK-MB异常(5．8％)。cTnI持续阳性组柯萨奇B病毒中和抗体转阴率明显低于cTnI阴性组,两者比较P<0．05。结论cTnI可作为急性病毒性心肌炎炎性损伤及预后判断的指标。     

False-positive troponin I measured with the Abbott AxSYM attributed to fibrin interference

BACKGROUND: Serum is often used for the measurement of cardiac troponin I (cTnI). Previous reports suggest that fibrin present in serum samples collected for cTnI analysis may interfere with measurement of this marker. We investigated the incidence and magnitude of fibrin interference in serum specimens submitted for cTnI measurement using the AxSYM analyzer by performing duplicate analysis of all specimens with increased cTnI results. METHODS: Over a 4-month period, we analyzed 3692 specimens for cTnI with the Abbott AxSYM. Of these, 307 (8.3%) showed increased cTnI. A threshold of three times the precision of the method (15%) was used to judge discrepancies between duplicate analyses of specimens; all specimens being recentrifuged between the initial and repeat cTnI analyses. RESULTS: Of 307 patient specimens with elevated cTnI concentrations, 24 (7.8%) demonstrated differences of greater than 45% between duplicate analyses. Concentrations of cTnI obtained on initial analysis of these 24 specimens ranged from 2.4 to 24.0 microg/l. Repeat analysis showed the repeat values for 20 (83%) to be within the normal reference interval, with 16 (67%) showing concentrations of less than 0.3 microg/l. CONCLUSIONS: Our finding indicates that interference should be highly suspected in serum specimens where the initially measured cTnI concentrations is in the range of 2.0-25.0 microg/l when using the Abbott AxSYM. The finding of no interference in specimens with measured troponin concentration greater than 25.0 microg/l suggests that the interference effect of fibrin is generally not sufficient to cause spurious elevations of cTnI into this range. In addition, since switching to plasma as the specimen of choice for the AxSYM, we have not observed any discrepant cTnI results following duplicate analysis of over 200 patient samples with initial measured cTnI concentrations of 2.0 microg/l or greater.     

病毒性心肌炎的快速检测心肌肌钙蛋白Ⅰ

目的 :探讨快速检测心肌肌钙蛋白 ( c Tn I)对病毒性心肌炎 ( VMC)的诊断价值。方法 :对 72例 VMC患者和 30例对照者进行 c Tn I和心肌酶谱检测分析。结果 :在诊断 VMC时 ,c T-n I敏感性和特异性都明显高于心肌酶谱 ( P <0 .0 0 1 )。结论 :c Tn I可作为诊断 VMC的重要指标     

Higher incidence and serum levels of minor cardiac biomarker elevation in sirolimus-eluting stent (Cypher) than bare metal stent implantations

OBJECTIVES: Minor cardiac biomarker elevation after percutaneous coronary intervention has long-term prognostic significance. The sirolimus-eluting stent (Cypher) has been reported to require high postinflation pressure for optimal implantation. We examined the incidence of minor cardiac biomarker elevation induced by Cypher implantation. METHODS: We measured the serum concentration of cardiac troponin-I (cTnI) 24 h after stenting and those of creatine kinase isoenzyme MB and creatine kinase before, immediately after, and 6, 12 and 24 h after implantation in patients who underwent Cypher stent (CS group; n=53) or bare metal stent (BMS group; n=57) implantation. RESULTS: No significant difference in clinical background was observed between the two groups. When a cutoff cTnI value of 0.50 ng/ml was used, the CS group showed a significantly higher incidence of cTnI elevation (35.8%, 19/53) than the BMS group (14.0%, 8/57) (P<0.05). Similarly, the incidence of cTnI > or = 0.03 ng/ml tended to be higher in the CS group (88.7%, 47/53) than in the BMS group (73.7%, 42/57: 0.05相似文献   

氟伐他汀干预治疗对不稳定性心绞痛患者介入治疗后炎症因子影响的研究

目的　研究氟伐他汀对不稳定性心绞痛冠状动脉介入(PCI)治疗术患者高敏C -反应蛋白(hs- CRP)、肿瘤坏死因子α(TNFα)和肌钙蛋白I(cTnI)的影响。方法　选择2002年7月至2004年4月在我院行冠状动脉介入术的60例不稳定性心绞痛患者为研究对象,随机分为二组:对照组29例,常规药物治疗(抗凝、硝酸酯类、β受体阻断剂、血管紧张素转换酶抑制剂和钙拮抗剂等) 2周;氟伐他汀干预组31例,在常规治疗基础上加用氟伐他汀(商品名来适可)每日40mg治疗2周。分别于药物治疗前、药物治疗后2周(术前当天)及术后24h采集空腹静脉血,测定血清hs -CRP、TNFα和cTnI浓度。结果　药物治疗后,氟伐他汀干预组较对照组血清hs CRP、TNFα和cTnI浓度降低更明显(P<0 .01);氟伐他汀干预组术后血清hs- CRP、TNFα和cTnI浓度明显低于同期对照组(P<0. 01)。结论　冠状动脉介入术后增加血清hs- CRP、TNFα和cTnI水平;氟伐他汀降低冠心病患者血清hs -CRP、TNFα和cTnI浓度;氟伐他汀降低冠状动脉介入术后患者血清CRP、TNFα和cTnI水平。     

Diagnostic accuracy study of urine dipstick in relation to 24-hour measurement as a screening tool for proteinuria in lupus nephritis

OBJECTIVE: Early detection of renal involvement in lupus prevents poor outcomes. Although published guidelines recommend urine dipstick as an appropriate screening test and evidence suggests a majority of American rheumatologists use dipstick to screen for proteinuria, the performance of this diagnostic approach in lupus has not been reported. We examined the validity of qualitative urine dipstick versus quantitative 24-hour measurement to accurately detect proteinuria, including low-level proteinuria. METHODS: We performed a diagnostic accuracy study using paired samples from the Johns Hopkins University School of Medicine and the Ohio State University School of Medicine lupus cohorts. All qualitative urine dipstick values were obtained within 1 day of a 24-hour urine collection. RESULTS: We analyzed the performance of 3 urine dipstick assays to detect proteinuria compared to 24-hour protein/creatinine ratios, using 2224 dipstick measures from 296 patients. The sensitivity of a > or = 1+ dipstick result to detect quantitative proteinuria (> or = 0.50 g protein/g creatinine) was 82.7% for the Clinitek, 97.7% for the Atlas, and 85.5% for the Bayer assay. The corresponding sensitivity to detect low-level proteinuria, (0.50-0.99 g protein/g creatinine) was 63.1%, 96.4%, and 80.7%, respectively. The specificity to correctly exclude proteinuria (< 0.50 g protein/g creatinine) with negative/trace results was 86.1%, 62.2%, and 59.4%. There was considerable variability in the range of protein/creatinine ratios detected at each dipstick level of proteinuria. CONCLUSION: Urine dipsticks demonstrate substantial variability and often poor validity to accurately detect proteinuria at quantitative levels; this warrants further diagnostic evaluation. Clinicians should consider quantified proteinuria assays as a more accurate screening tool in the diagnostic evaluation of lupus nephritis.     

Cardiac troponin I predicts myocardial dysfunction and adverse outcome in septic shock

OBJECTIVE: The objectives of this study were to determine myocardial injury in patients with septic shock by measuring serum cardiac troponin I (cTnI), to evaluate relationship between elevated cTnI and myocardial dysfunction and to determine if cTnI is a predictor of outcome in these patients. METHODS: Thirty-seven consecutive patients with septic shock were included in the study. Serum cTnI was measured at study entry and after 24 and 48 h. Transthoracic echocardiogram, electrocardiogram and regular biochemical and hemodynamic assessments were performed. RESULTS: Sixteen (43%) patients had elevated serum cTnI. These patients had higher need for inotropic/vasopressor support (94% vs. 53%, p=0.018), higher APACHE II score (28 vs. 20, p=0.004), higher incidence of regional wall motion abnormalities on echocardiography (56% vs. 6%, p=0.002), lower ejection fraction (46% vs. 62%, p=0.04) and higher mortality (56% vs. 24%, p=0.04) compared to normal cTnI patients. By multiple logistic regression analysis, serum cTnI and APACHE II score were independent predictor of death and length of stay in intensive care unit. Serum cTnI, APACHE II score, anion gap and serum lactate were independent predictor of need for inotropic/vasopressor support. Receiver-operating characteristics of serum cTnI as a predictor of death in septic shock were significant. The elevated serum level of cTnI correlated with the lower left ventricular ejection fraction (p<0.001). CONCLUSIONS: Myocardial injury can be determined in patients with septic shock by serum cTnI. Serum cTnI concentration correlates with myocardial dysfunction in septic shock. High serum cTnI predicts increased severity of sepsis and higher mortality. A close monitoring of patients with septic shock and elevated levels cTnI is warranted.     

血清miR-499及SOX6的表达与急性心肌梗死患者预后的关系及其预测价值

目的 探讨血清miR-499及SOX6表达对急性心肌梗死(AMI)患者预后的评估价值.方法 选取2016年2月～2019年10月在石家庄人民医院心内科确诊的AMI患者132例,收集患者一般临床资料,采用实时荧光定量PCR(RT-qPCR)技术检测患者血清miR-499及SOX6的表达水平.根据患者随访期间是否发生主要不...     

Cardiac transgenic and gene transfer strategies converge to support an important role for troponin I in regulating relaxation in cardiac myocytes

Elucidating the relative roles of cardiac troponin I (cTnI) and phospholamban (PLN) in beta-adrenergic-mediated hastening of cardiac relaxation has been challenging and controversial. To test the hypothesis that beta-adrenergic phosphorylation of cTnI has a prominent role in accelerating cardiac myocyte relaxation performance we used transgenic (Tg) mice bearing near complete replacement of native cTnI with a beta-adrenergic phospho-mimetic of cTnI whereby tandem serine codons 23/24 were converted to aspartic acids (cTnI S23/24D). Adult cardiac myocytes were isolated and contractility determined at physiological temperature under unloaded and loaded conditions using micro-carbon fibers. At baseline, cTnI S23/24D myocytes had significantly faster relaxation times relative to controls, and isoproterenol stimulation (Iso) had only a small effect to further speed relaxation in cTnI S23/24D myocytes (delta Iso: 7.2 ms) relative to the maximum Iso effect (31.2 ms) in control. The Ca(2+) transient decay rate was similarly accelerated by Iso in Tg and nontransgenic (Ntg) myocytes. Gene transfer of cTnI S23/24D to myocytes in primary culture showed comparable findings. Gene transfer of cTnI with both serines 23/24 converted to alanines (cTnI S23/24A), or gene transfer of slow skeletal TnI, both of which lack PKA phosphorylation sites, significantly blunted Iso-mediated enhanced relaxation compared with controls. Gene transfer of wild-type cTnI had no effect on relaxation. These findings support a key role of cTnI in myocyte relaxation and highlight a direct contribution of the myofilaments in modulating the dynamics of myocardial performance.