双源计算机断层扫描成像在冠状动脉小血管支架内再狭窄的应用价值

目的探讨双源计算机断层扫描冠状动脉造影术(dual source computed tomography coronary angiography,DSCT-CA)在冠状动脉小血管支架内再狭窄的应用价值。方法对76例(男59例,女17例)有胸闷、胸痛的患者在术后6～12个月行经皮冠状动脉造影后行DSCT-CA检查。根据心率及造影结果将患者分成不同的组别:心率≤70次/min组[n=48,扫描时心率(58±5)次/min]与心率﹥70次/min组[n=41,扫描时心率(78±9)次/min];简单病变组(单个支架,n=54)与复杂病变组(重叠支架及分叉支架,n=35);右冠状动脉组(n=33)、左回旋支组(n=43)和左前降支组(n=13),并比较分析DSCT-CA对各组诊断的敏感性、特异性及阳性预测值、阴性预测值。结果76例患者共植入89个支架,其中31.4%(28/89)的支架经血管造影证实有再狭窄。DSCT-CA对支架内再狭窄的敏感性、特异性及阳性预测值、阴性预测值分别为89%、87%、76%和95%。DSCT-CA对心率≤70次/min组与心率﹥70次/min组的诊断价值比较,差异无统计学意义(P>0.05)。DSCT-CA对冠状动脉三主支的诊断价值比较,差异也无统计学意义(P>0.05)。DSCT-CA诊断复杂病变组的敏感性、阳性预测值、特异性,阴性预测值均低于简单病变组,差异有统计学意义(83%vs.94%,P<0.05;63%vs.88%,P<0.05;74%vs.95%,P<0.05;89%vs.97%,P<0.05)。简单病变组组内分析结果显示,其敏感性和特异性比较,差异无统计学意义(94%vs.95%,P>0.05);阳性预测值低于阴性预测值,差异有统计学意义(88%vs.97%,P<0.05)。4年的质控分析结果显示,DSCT-CA检测小血管支架内再狭窄率呈逐年上升趋势,2006年及2007年再狭窄率均在平均水平以下,2009年超出了平均水平的一倍。结论DSCT-CA可作为小血管支架术后再狭窄的筛选手段,阴性者可排外支架内再狭窄,阳性者需进一步行冠状动脉造影以明确诊断。     

SSF在改善冠状动脉CT图像质量中的应用

目的:探讨冠脉运动追踪冻结平台(SSF)在改善64层螺旋CT冠状动脉图像质量中的应用价值。方法:回顾性分析行冠状动脉CT成像(CCTA)检查的121例患者的标准重建图像及基于SSF的运动校正图像,平均心率(HR)≤60次/min 39例,HR 60~70次/min 42例,HR70次/min 40例。分析平均HR、HR变异及HR波动对冠状动脉图像质量的影响;分析同一平均HR时,运动校正前后冠状动脉图像质量的差异。结果:平均HR是影响冠状动脉图像质量的主要因素。HR≤60次/min时,SSF在改善右冠状动脉的图像质量中有价值;HR 60~70次/min时,SSF在改善右冠状动脉及左冠状动脉小血管的图像质量中有价值;HR70次/min时,SSF能显著改善左右冠状动脉的图像质量。结论:SSF在改善冠状动脉的图像质量中有良好应用价值,特别是对高HR患者。     

心率对老年人64层CT冠状动脉造影质量的影响

目的探讨心率对老年人64层CT冠状动脉造影质量的影响。方法回顾性分析137例老年患者64层螺旋CT冠状动脉造影结果。根据检查时心率不同分为三组:A组58例,心率70次/min,平均64次/min;B组55例,心率70～79次/min,平均74次/min;C组24例,心率80～88次/min,平均85次/min。采集的原始图像采用容积再现技术(VRT),多平面重建(MPR),曲面重建(CPR)和最大密度投影(MIP)等后处理技术。冠状动脉主要分支(RCA、LM、LAD、LCX)的CT图像质量采用双盲法、按照5级评分法进行评估,3分以上认为图像质量合格,达到诊断要求。结果图像质量符合诊断要求比率分别为:A组96.6%(224/232),B组92.7%(204/220),C组83.3%(80/96)。经χ2检验,A、B两组之间图像质量合格率无统计学差异(χ2=3.28,P0.05)。结论应用64层螺旋CT进行冠状动脉造影在一定程度内适当放宽对心率的要求(≤80次/min),图像质量仍可基本满足诊断需要,是一种筛查老年人冠心病的安全、有效手段。     

SSF技术在高心率和心率波动受检者CCTA中的应用价值

目的探讨SSF技术在改善高心率(心率70次/min)和心率波动受检者冠状动脉成像质量中的临床应用价值。方法选取66例高心率和心率波动受检者进行冠脉CT血管成像扫描后,分别得到A、B两组图像,其中A组图像采用标准重建,B组图像采用SSF重建,并将检查结果进行对比,分析两组之间冠状动脉图像质量差异。结果除了左主干显示无明显差异外,其余冠状动脉节段B组图像质量均优于A组(P0.05),右冠状动脉S2、S3段及回旋支S10段图像质量明显改善;随着心率增加,A、B两组图像质量均有下降,二者之间无统计学意义(P0.05)。结论 SSF技术可以改善高心率及心率不稳病人的冠状动脉成像质量,满足临床诊断需求,拓宽了受检者临床检查范围,让冠状动脉CTA检查成为真正意义上的冠状动脉病变首选筛查手段,为冠心病临床诊断提供有价值的影像学信息。     

两种方法控制64排螺旋CT冠状动脉成像中心率的比较

目的: 通过两组病例的对比研究,探讨控制患者检查前的心率和效果。方法: 基础心率大于70次/min的患者654例,分为药物干预组352例和心理干预组302例,进行不同的心率干预措施后行64排螺旋CT冠状动脉成像,将两组患者的心率控制效果,冠状动脉图像质量及图像后处理的时间进行比较。结果: 经过口服倍他乐克减慢和稳定心率后, 340例（96.6%）心率降至70次/min以下,12例（3.4%）口服倍他乐克者未降至目标心率。352例患者中有347例（98.8%）的整体图像能满足诊断要求。心理干预组127例（42.0%）经过给予心理护理后心率降至70次/min 以下,154例（58.0%）未降至目标心率。302例患者中266例（88%）能满足诊断要求。控制组图像后处理的平均时间为（12±5）min,对照组图像后处理的平均时间为（18±6）min。结论: 倍他乐克可降低心率明显提高冠状动脉CTA的成像质量,药物控制心率优于心理护理。     

静息心率增高对冠心病患者的影响

目的探讨静息心率(RHR)对冠心病患者产生不良心脏事件及心率变异性的影响和临床意义。方法106例冠心病患者,按RHR水平分为:50~65次/min组(A组),28例;66~84次/min组(B组),41例;≥85次/min组(C组),37例。对入选患者分别进行24 h动态心电图、心电图检查和发病情况进行询问。结果随着RHR的增高,不良心脏事件的发生率和心肌缺血检出率增加,心率变异性明显降低。各组间比较差异有统计学意义(P<0.05或P<0.01)。结论冠心病患者随着RHR的增高,不良心脏事件发生率和心肌缺血检出率增加,心率变异性明显降低,RHR的增高是发生不良心脏事件的危险因素和预测因子。     

中青年甲亢患者心电图分析

目的 探讨心电图变化对中青年甲亢的诊断价值。方法 对我院门诊就诊且初次诊断为甲亢的75例患者的心电图资料进行分析,并且选择75例来我院体检,性别、年龄匹配的正常人群的心电图资料作为对照。结果 甲亢组患者心电图改变37例(49.33%),正常对照组心电图改变23例(30.67%),两组差异有统计学意义(P<0.05),且心电图改变主要为ST段、T波的改变。甲亢组心率明显快于正常对照组,甲亢组心率(77.72±12.98)次/min,正常对照组心率(71.29±10.14)次/min,两组差异有统计学意义。甲亢患者中,心电图异常率女性患者(61.70%)明显高于男性患者(32.14%),两者比较差异有统计学意义。甲亢组相对于对照组QT间期缩短、QTc间期延长、P波振幅增高,两组比较差异有统计学意义。结论 甲亢患者心电图异常发生率比对照组高,心电图对甲亢的诊断有一定的参考价值。     

探索64排CT后门控冠状动脉图像质量与心率的关系

目的探讨64排CT后门控冠状动脉图像质量与心率的关系。方法将372例分三组,A组心率70次/min,B组心率70次/min80次/min,C组心率80次/min(心率大于90次/min药物控制),部分数据通过冠脉多期相重组来改善图像质量,最后只对运动幅度相对较大的、较难成像的RCA进行图像质量评价,图像质量评价标准改良分为3个等级(Ⅰ级管腔光整,边缘锐利;Ⅱ级局部少许管腔不光整,不影响诊断;Ⅲ级多处管腔边缘不光整,但可以做出诊断)。结果 64排CT冠脉图像质量随着心率的升高而降低;对于部分高心率(大于80±2次/min),经双扇区的选择及多期相重建,图像质量C组与B组接近,双扇区、时相重建选择虽延长了后处理的时间,但对图像质量明显改善,仍能满足诊断及临床的需求。     

老年高血压患者静息心率增加对靶器官损害的临床研究

目的探讨老年原发性高血压(EH)患者静息心率(RHR)与靶器官损害的关系。方法入选老年EH患者206例,按RHR水平分为RHR1组<70次/min(56例),RHR2组70次≤RHR<80次/min(84例),RHR3组RHR≥80次(66例)三组。对人选患者做以下检查心电图、超声心动图、颈动脉超声、肌酐清除率以及尿微量白蛋白。结果(1)RHR2组和RHR3组的颈动脉内膜厚度(IMT)、颈动脉内径(CAD)、左心室重量指数(LVMI)以及尿微量白蛋白定量(MAU)均高于RHR1组(P<0.01),而左室射血分数(LVEF)、肌酐清除率小于RHR1组(P<0.01)。(2)RHR与IMT、CAD、LVMI、MAU呈正相关(r分别为0.312、0.289、0.630、0.576,P<0.01),而与LVEF、肌酐清除率呈负相关(r分别为-0.563、-0.510,P<0.01)。(3)非条件Logistic回归分析显示,RHR、收缩压(SBP)、舒张压(DBP)、脉压(PP)对高血压性心脏病、冠心病、心力衰竭、脑血管意外和肾功能损害有不同程度的影响(P<0.05或P<0.01),其中SBP和RHR的作用更大。结论RHR可能是老年EH患者靶器官损害的独立危险因素。     

冠心病血运重建后静息心率控制情况及影响因素分析

目的:了解血运重建1年后稳定的冠心病患者静息心率控制情况及相关影响因素。方法:按照标准筛选我院2016年9月1日至2017年3月31日,行血运重建的冠心病患者。收集患者基本信息、临床指标、冠心病用药及血运重建治疗情况。根据术后1年静息心率分为三组,即心率≤60次/min组(278例)、61～69次/min组(425例)及≥70次/min组(357例);根据患者是否使用β受体阻滞剂,将患者分为两组,即用药组(804例)和未用药组(256例)。通过Logistic多因素回归分析心率控制不良(心率≥70次/min)的因素和影响患者服用β受体阻滞剂的因素。结果:入选了1 060例血运重建后稳定的冠心病患者,26. 2%患者静息心率≤60次/min,40. 1%患者静息心率在61～69次/min,33. 7%患者静息心率≥70次/min,75. 9%的患者使用β受体阻滞剂治疗。心率在61～69次/min组中β受体使用比例最高。在心率≥70次/min组中美托洛尔使用的平均剂量最高。心率控制不佳(≥70次/min)的危险因素包括:正在吸烟(OR=2. 72,95%CI:1. 84～4. 00,P<0. 01)、糖尿病(OR=1. 63,95%CI:1. 14～2. 32,P<0. 01);而对目标心率的知晓则与心率控制成正相关(OR=0. 02,95%CI:0. 01～0. 04,P<0. 01)。影响β受体阻滞剂的因素包括:对心率控制知晓(OR=3. 63,95%CI:2. 18～6. 06,P=0. 000),心肌梗死(OR=1. 71,95%CI:1. 17～2. 49,P=0. 005)和基础静息心率高(OR=1. 08,95%CI:1. 05～1. 11,P=0. 000)。结论:尽管β受体阻滞剂的广泛应用,但仍有1/3的患者静息心率控制不佳。在心率≥70次/min患者中,β阻滞剂使用剂量同时也高,考虑患者基础心率高,医师加强心率控制,但仍待进一步提高。同时告知患者心率控制目标可加强门诊随访,调整药物。     

High-Pitch Coronary CT Angiography at 70 kVp With Low Contrast Medium Volume: Comparison of 80 and 100 kVp High-Pitch Protocols

The purpose of this article is to evaluate image quality and radiation dose of prospectively electrocardiogram (ECG)-triggered high-pitch coronary computed tomography angiography (CCTA) at 70 kVp and 30 mL contrast medium.One hundred fifty patients with a heart rate ≤70 beats per minute (bpm) underwent CCTA using a second-generation dual-source computed tomography (CT) scanner and were randomized into 3 groups according to tube voltage and contrast medium volume (370 mg/mL iodine concentration) (100 kVp group, 100 kVp/60 mL, n = 55; 80 kVp group, 80 kVp/60 mL, n = 44; 70 kVp group, 70 kVp/30 mL, n = 51). Objective and subjective image quality along with the effect of heart rate (HR) and body mass index (BMI) was evaluated and compared between the groups. Radiation dose was estimated for each patient.CT attenuation and image noise were higher in the 80 and 70 kVp groups than in the 100 kVp group (all P < 0.001). Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were lower in the 70 kVp group than in the 80 and 100 kVp groups (all P < 0.05). There was no difference for subjective image quality between the groups (P > 0.05). HR did not affect subjective image quality (all P > 0.05), while patients with BMI <23 kg/m² had higher image quality than patients with BMI ≥23 kg/m² (P < 0.05). Compared with the 100 kVp group, the radiation dose of the 70 kVp group was reduced by 75%.In conclusion, prospectively ECG-triggered high-pitch 70 kVp/30 mL CCTA can obtain diagnostic image quality with lower radiation dose in selected patients with BMI <23 kg/m² compared with 80/100 kVp/60 mL CCTA.     

心率及心率波动对256层CT回顾性心电门控冠状动脉成像质量的影响简

目的 探讨心率及心率波动对256层计算机断层扫描（computerized tomography,CT）冠状动脉成像图像质量的影响.方法 150例疑为冠状动脉粥样硬化性心脏病（冠心病）的患者行256层CT回顾性心电门控冠状动脉检查,对直径＞1.5 mm的冠状动脉节段进行评分.根据平均心率分为3组：A组,心率＜65次/min;B组,65次/min～80次/min;C组,心率≥80次/min.比较不同心率组间的图像质量,采用Pearson相关分析方法分析平均心率及心率波动对图像质量的影响,并采用线性回归方程确定需进行干预的心率临界点.结果 在最佳重组时相上,可满足诊断要求的图像占97.9％.冠状动脉总体、右冠状动脉、左前降支及左旋支的图像质量评分与心率显著相关,相关系数分别为0.473、0.425、0.409、0.413（P均＜0.001）,冠状动脉图像质量与心率波动无明显相关（P＞0.05）.不同心率组间冠状动脉图像质量比较,差异有统计学意义（P＜0.05）.当心率＜83.1次/min时,可获得优良的图像质量,而为获取满足临床诊断要求的图像,心率应＜119.1次/min.心率＜65次/min时,舒张期重建的图像质量佳;心率＞71次/min时,收缩期重建的图像质量佳.结论 心率波动对256层CT同顾性心电门控冠状动脉图像质量无显著影响,但心率仍是影响图像质量的一个重要因素;降低心率有助于提高图像质量.     

Coronary computed tomography angiography in a patient with atrial fibrillation, case report

Atrial fibrillation (AF) is the most common persistent arrhythmia. It is associated with wide range of cardiac clinical conditions. Because of variable duration of cardiac cycle resulting in reduced image quality, AF has been considered relative contraindication for performing coronary computed tomography angiography (CCTA). However, recent reports have suggested that newer dual source scanner with higher temporal resolution can be used in patients with AF ( [Oncel et al., 2007] , [Wolak et al., 2008] and [Rist et al., 2009] ). Image quality can be maintained if heart rate is lowered to less than 70 beats per minute. However, high heart rate can still be challenging. Mapping systolic phase with the use of absolute delay reconstruction algorithm has been shown to provide better image quality. In this article, we present a case of patient with chronic AF and in whom coronary examination was required before going to repair of aortic root dissection. CCTA, with the use of absolute delay reconstruction algorithm, provided diagnostic image quality of the coronary arteries.     

Multidetector-row computed tomography coronary angiography: optimization of image reconstruction phase according to the heart rate.

BACKGROUND: To optimize the image reconstruction phase of multidetector-row computed tomography (MDCT) coronary angiography according to the heart rate is crucial. METHODS AND RESULTS: Scan data were reconstructed for 10 different phases in 58 sequential patients who underwent 8-row cardiac MDCT. The obtained images were scored and compared in terms of motion artifacts and visibility of the vessels, and moreover, ECG record-based evaluations were added for clarification of the temporal relationships among these 10 phases. In the cases with lower heart rates (<65 beats/min), the best quality images were obtained when the end of the image reconstruction phase was positioned at the peak of the P wave. In some cases with higher heart rates (>65 beats/min), they were obtained in the late systolic period. CONCLUSION: As the heart rate increased, the optimal image reconstruction phase changed from mid diastole to late systole. However, it is recommended to try to decrease the heart rate of patients before data acquisition.     

增龄及冠心病对运动的反应和心率变异性的影响

目的　研究 70岁以上冠心病及非冠心病老人心血管系统对运动负荷的反应 ,探讨其运动负荷特征与心率变异各能谱范围的关系。方法　经活动平板运动试验、动态心电图心率变异能谱分析、并行冠状动脉造影患者 2 16例。 70岁以上老人 96例为老年组 (Ⅰ组 ) ,70岁以下 12 0例为对照组 (Ⅱ组 ) ,两组各分两个亚组 ,冠心病患者分别为Ⅰa、Ⅱa组、非冠心病患者各为Ⅰb组、Ⅱb组。比较各组患者运动前后各生理指标的变化。结果　 (1)Ⅰ组运动峰值心率低于次极量心率 (极量心率 85 % )或 <12 0次 min者多于Ⅱ组 (Ⅰa组 35 .14 %vsⅡa组 15 .5 5 % ,P <0 .0 1,Ⅰb组 16 .95 %vsⅡb组 5 .33% ,P <0 .0 5 ) ;ⅠaⅠb组运动后 1min心率恢复值均 <12次 min ;心率变异高能谱范围呈现增龄性改变 (Ⅰa组vsⅡa组 ,P <0 .0 5 ;Ⅰb组vsⅡb组 ,P <0 .0 5 )。 (2 )Ⅰa组心肌缺血多发生于较低运动负荷时 [ST压低 1mm时的代谢当量 (METs)Ⅰa组 4 .4 8vsⅡa组 5 .4 8,P <0 .0 5 ];Ⅰa组心率变异各能谱范围多呈有意义降低 ,心率变时性损害Ⅰa组高于其他 3个组。结论　 (1)老年人尤其老年冠心病患者存在运动后心血管系统反应迟钝现象 ,心率变异高能谱范围呈现增龄性改变。 (2 )老年冠心病患者心率变异各能谱均有异常。 (3)老年冠心病患?     

Dual-Source Computed Tomographic Coronary Angiography: Image Quality and Stenosis Diagnosis in Patients with High Heart Rates

We sought to evaluate prospectively the effects of heart rate and heart-rate variability on dual-source computed tomographic coronary image quality in patients whose heart rates were high, and to determine retrospectively the accuracy of dual-source computed tomographic diagnosis of coronary artery stenosis in the same patients.We compared image quality and diagnostic accuracy in 40 patients whose heart rates exceeded 70 beats/min with the same data in 40 patients whose heart rates were 70 beats/min or slower. In both groups, we analyzed 1,133 coronary arterial segments. Five hundred forty-five segments (97.7%) in low-heart-rate patients and 539 segments (93.7%) in high-heart-rate patients were of diagnostic image quality. We considered P < 0.05 to be statistically significant. No statistically significant differences between the groups were found in diagnostic-image quality scores of total segments or of any coronary artery, nor were any significant differences found between the groups in the accurate diagnosis of angiographically significant stenosis.Calcification was the chief factor that affected diagnostic accuracy. In high-heart-rate patients, heart-rate variability was significantly related to the diagnostic image quality of all segments (P = 0.001) and of the left circumflex coronary artery (P = 0.016). Heart-rate variability of more than 5 beats/min most strongly contributed to an inability to evaluate segments in both groups. When heart rates rose, the optimal reconstruction window shifted from diastole to systole.The image quality of dual-source computed tomographic coronary angiography at high heart rates enables sufficient diagnosis of stenosis, although variability of heart rates significantly deteriorates image quality.Key words: Artifacts, coronary angiography/methods, coronary stenosis/diagnosis/radiography, diastole/physiology, heart rate/physiology, image processing, computer-assisted, prospective studies, radiographic image interpretation, computer-assisted, sensitivity and specificity, systole/physiology, technology assessment, biomedical, tomography, spiral computed/instrumentation/methods/standardsDuring the past few years, noninvasive coronary angiography upon multidetector-row computed tomography (MDCT) has rapidly progressed and has shown promise with regard to the detection and quantification of coronary artery stenosis.^1–4 However, despite the increase in temporal resolution from 16- to 64-detector-row computed tomography (CT), coronary CT angiography remains sensitive to motion artifacts, which occur especially at higher heart rates.^2,5–7 Results of a study³ of 64-detector-row CT coronary angiography showed a nonsignificant tendency toward lower image quality at higher mean heart rates, and a significant negative relation between image quality and heart-rate variability. In order to reduce motion artifacts, it has been proposed that patients be administered oral β-blocker medication for heart-rate control, even when 64-detector-row CT is to be used.^8–11 In most studies that have involved 16- or 64-detector-row CT, the target for scanning has been maintained at heart rates slower than 70 or even 60 beats/min, so that good-quality images of coronary arteries could be obtained. The requirement to premedicate patients with β-blocker drugs in order to achieve a sufficiently low heart rate for scanning has been considered a major limitation surrounding the clinical use of MDCT coronary angiography.Dual-source CT (DSCT) coronary angiography incorporates 2 X-ray tubes and 2 detectors that are mounted onto a rotating gantry, with an angular offset of 90°.¹² The DSCT system affords a high temporal resolution of 83 ms in monosegment reconstruction mode. In contrast with single-source CT systems that rely on multisegment reconstruction techniques, temporal resolution upon DSCT is independent of heart rate. Initial studies have shown that DSCT enables the study of coronary arteries with excellent diagnostic quality in all patients, independent of heart rate—thus obviating the need to premedicate patients with β-blockers.^12–15 We believed that the effects of heart rate and heart-rate variability on image quality, diagnostic accuracy, and optimal reconstruction windows merited further evaluation in patients whose heart rates exceeded 70 beats/min.The aim of this study was to evaluate prospectively the effect of heart rate and heart-rate variability on DSCT image quality in patients who had high heart rates, and to determine retrospectively the accuracy of DSCT in the diagnosis of coronary artery stenosis, using invasive coronary angiography as the reference standard.     

超声心动图对不同频率AAI及VVI起搏的血流动力学研究

目的本研究的目的在于评价不同频率ＡＡＩ及ＶＶＩ起搏的血流动力学效果，探索最佳起搏频率范围，比较ＡＡＩ及ＶＶＩ起搏的血流动力学效果。方法３７例植入永久心脏起搏器的患者分为两组，ＡＡＩ组１７例，ＶＶＩ组２０例。程控起搏频率从５０～１００次／分，以超声心动图评价其血流动力学效果。结果在ＡＡＩ起搏组，７０次／分起搏的心排血量（ＣＯ）高于５０及６０次／分起搏（Ｐ＜０．０５）。８０～９０次／分起搏的ＣＯ变化无显著性差异。１００次／分起搏的ＣＯ低于９０次／分起搏。在ＶＶＩ起搏组，起搏频率超过８０次／分时，ＣＯ不再增高，１１０次／分起搏的ＣＯ甚至低于７０次／分起搏，左室射血分数（ＬＶＥＦ）则随之下降。但ＡＡＩ起搏的ＣＯ及ＬＶＥＦ在起搏频率相同情况下显著高于ＶＶＩ起搏组。结论在有心脏病的患者，最佳起搏频率范围较窄，为７０～８０次／分。ＡＡＩ起搏的血流动力学效果显著优于ＶＶＩ起搏。     

Effects of heart rate changes on arterial distensibility in humans

In rats, an increase in heart rate by pacing is accompanied by progressive large-artery stiffening. Whether this is also the case in humans is unknown. We enrolled 20 patients who were chronically implanted with a pacemaker because of atrioventricular block or sick sinus syndrome. Arterial distensibility was measured by an echo-tracking device. In 10 patients, the evaluation was performed on the radial artery by using continuous finger blood pressure measurements, whereas in the remaining 10 patients, the common carotid artery was studied with a semiautomatic measure of brachial artery blood pressure. Diastolic diameter, systodiastolic diameter change, and distensibility were obtained at baseline (heart rate 63+/-2 beats/min) and after atrial and ventricular sequential pacing at a heart rate of 90 and 110 beats/min. At baseline, the diameter was 7.8+/-0.3 mm in the carotid artery and 2.4+/-0.1 mm in the radial artery; the respective systodiastolic diameter change values were 375.4+/-31.0 and 55.9+/-9.0 (microm) and the distensibility values were 1.4+/-0.1 and 0.7+/-0.1 (1/mm Hg 10-3). Blood pressure and diameter were not significantly modified by increasing heart rate, which markedly modified systodiastolic diameter change and distensibility. In the radial artery, distensibility was reduced by 47% (P<0.05) at a heart rate of 90 beats/min with no further reduction at 110 beats/min. In the carotid artery, distensibility was reduced by 20% at a heart rate of 90 beats/min (P<0.05) with a further reduction at 110 beats/min (45%, P<0.05). These data provide the first evidence in humans that acute increases in heart rate markedly affect arterial distensibility and that this occurs in both large- and middle-size muscle arteries within the range of "normal" heart rate values.     

Demonstration of training effect during chronic beta-adrenergic blockade in patients with coronary artery disease

Attenuation of exercise-induced increases in heart rate and cardiac output by chronic beta-adrenergic blockade has been thought to compromise benefit of exercise training in patients with coronary artery disease (CAD). To assess this important issue, 35 CAD patients were evaluated by a 3-month walk-jog-cycle training program: 14 patients received no beta blocker (group 1), 14 received propranolol, 30-80 mg/day (group 2), and seven patients received propranolol, 120-240 mg/day (group 3). The extent of CAD, resting heart rate before training blood pressure and VO2 max were similar (p = NS) in each group. The maximal exercise heart rate (mean +/- SD, 147 +/- 21 beats/min in group 1 vs 120 +/- 10 beats/min in group 2 and 115 +/- 12 beats/min in group 3 (both p less than 0.05 vs group 1). The VO2 max before training was 25 +/- 5.0 ml/kg/min in group 1 vs 23 +/- 3.2 ml/kg/min in group 2 and 26 +/- 2.8 ml/Kg/min in group 3 (all p = NS). Training consisted of three 1-hour periods per week at a heart rate of 70-85% of the maximal pretraining heart rate. In each group, VO2 increased (p less than 0.05) after training: group 1, 27%; group 2, 30%; group 3, 46%. The double product was unchanged after training (p = NS) in each group. These data indicate that substantial training effects may be achieved in CAD patients despite therapeutic doses of beta blockers and a reduced training HR. Thus, there appears to be no indication to reduce beta blockers in CAD patients engaged in cardiac rehabilitation.