不同心肌保护方法在双瓣膜置换术中对心肌的保护作用

目的探讨双瓣膜置换术(DVR)中更有效的心肌保护措施。方法选择2010年2月～2011年8月在我院行二尖瓣和主动脉瓣双瓣膜置换术的30例患者为研究对象,根据入院顺序将患者分为3组,每组10例。①顺行灌注组:经左、右冠状动脉开口顺行性灌注冷血心脏停搏液,完成双瓣膜置换术;②逆行灌注组:经冠状静脉窦间断逆行灌注冷血心脏停搏液,完成双瓣膜置换术;③顺逆联合灌注组:先按顺行灌注方法,再采用逆行灌注方法,完成双瓣膜置换术;观察3组术后早期临床疗效;观察心肌乳酸释放率、血清心肌肌钙蛋白Ⅰ(cTnI)、磷酸肌酸激酶同工酶(CK-MB)的含量变化。结果 30例患者无手术死亡,均痊愈出院。顺行灌注组和顺逆联合灌注组主动脉阻断60min时心肌乳酸浓度低于逆行灌注组。主动脉开放20min、术后第1d顺行灌注组和顺逆联合灌注组的血清CK-MB、cTnI浓度低于逆行灌注组。结论以上3种心肌保护方法均有效,但顺行灌注组和顺逆联合灌注组效果较好;顺逆联合灌注方法操作方便,不影响手术进程,是一种有效的选择。     

未成熟心肌保护与停搏液灌注压的试验研究

目的 确定婴幼儿先心病心内直视术中不同灌注压力的冷晶体停搏液对未成熟心肌保护的效应关系.方法 将60例择期在体外循环(ECC)和心脏停搏下,行单纯VSD(室间隔缺损)修补术的先心病患儿,随机分成3组,每组20例,主动脉阻断(ACC)后于其根部分别以45、75、100 mm Hg的压力顺行灌注冷晶体停搏液.在围术期采集患儿中心静脉血测定血浆心肌酶(CK-MB)和肌钙蛋白Ⅰ(cTn-Ⅰ)水平.临床观察心脏停跳及复跳情况、术后机械通气时间及术后正性肌力药物的应用情况.结果 (1)3组在ACC后各时点CK-MB、cTn-Ⅰ与基础值相比明显升高,且分别于术后1、24 h时达到高峰,但升高幅度45 mm Hg组低于75 mm Hg组(P＜0.05),更低于100 mm Hg组(P＜0.01).(2)灌注压力与诱导停搏时间呈负相关(P＜0.01);与自动复跳时间呈正相关(P＜0.01).(3)心脏自动复跳率45 mm Hg组(100%)明显高于其它2组.(4)术后多巴胺辅助用量大于5μg·kg-1·min-1者,45mm Hg组明显低于其它2组的例数,肾上腺素支持者同样有显著区别(P＜0.05).结论 婴幼儿先心病心内直视手术时,停搏液的灌注压力在小于100mm Hg时心肌保护安全,但以45 mm Hg时对未成熟心肌保护效果最佳.     

体外循环心脏手术中心肌保护方法的改进

采用充氧温血停跳液经主动脉根部间断灌注，或经冠状静脉窦持续逆行灌注，应用26例。其中单瓣置换8例，双瓣置换4例，主动脉窦瘤破裂修补2例，左房粘液瘤切除5例，心功能Ⅲ～Ⅳ级者22例。对照观察发现，充氧温血灌注法术中心脏自动复跳率高，术后循环功能稳定，严重心律失常及低心排综合征发生率低，对缺血心肌的保护优于冷晶体灌注法。     

犬的原位心脏移植实验

从1990年12月至1993年8月笔者等施行了13次犬的心脏原位移植实验,在供心的完整采取、心肌保护和心脏缝接技术等方面摸索了一套经验。第一组(6只)的供心行单次冷晶体心麻液经主动脉根部顺行灌注;第二组(7只)的供心经冠状静脉窦持续逆行灌注中低温高钾氧合血。两组供心的保存时间平均为155分。实验结果证实第二组的心肌保护效果好:心脏自动复跳率高、存活时间长(P<0.01)、心脏超微结构改变轻微;第一组心移植后存活时间为3小时～6小时10分(平均4小时47分);第二组术后存活时间3小时30分～21小时25分(平均6小时27分)。移植后死亡原因主要为心、肾功能衰竭。     

冠状静脉窦逆行灌注VEGF蛋白的实验研究

目的观察经冠状静脉窦逆行灌注血管内皮生长因子(VEGF)对其分布的影响。方法20只新西兰大白兔随机分为实验组(VEGF组)和对照组,2组动物常规全麻,气管插管,胸骨正中切开,暴露心脏,结扎左室支建立心肌梗死模型,冠状静脉窦插管,实验组逆行灌注VEGF蛋白,对照组以生理盐水对照。全程记录心电,逆行灌注后30min取梗死区(左室心尖部)及非梗死区(高侧壁)心肌检测VEGF蛋白分布情况。结果结扎左室支即刻所有动物出现ST段抬高并与T波融合,免疫组织化学显示实验组梗死区有大量的VEGF蛋白,Western blot分析显示实验组梗死区在22kd处有明显的阳性条带,而非梗死区及对照组则为阴性。结论冠状静脉窦逆行灌注技术能很好地将VEGF蛋白靶向导入梗死区。     

温血逆行灌注对瓣膜置换同期冠脉搭桥术患者心肌保护作用的研究

目的：探讨使用温血逆行灌注技术对瓣膜置换同期冠脉搭桥术患者的心肌保护作用。方法40例行瓣膜置换手术加冠状动脉搭桥手术患者随机分为两组：研究组（温血逆行灌注组）和对照组（常规灌注组）,各20例。对照组常规冷晶体氧合血顺行灌注,研究组在温晶体氧合血的基础上给于逆行灌注。观察两组术中心脏复苏情况,分别于转流前、主动脉开放后10min、术后2h、术后4h和24h,采集动脉血标本,检查心肌肌钙蛋白T(cTnT)、心肌肌酸激酶(CK)、肌酸激酶同工酶(CK-MB)。结果转流前及主动脉阻断开放后10min,两组心肌酶学指标无明显差别(P>0.05)。而术后2h、4h和24h研究组cTnT、CK和CK-MB指标低于对照组(P<0.05);且两组分别与转流前相比差异均有统计学意义(P<0.05)。结论温血逆行灌注对瓣膜置换同期冠状动脉搭桥手术患者有较好的心肌保护作用。     

冠状动脉搭桥术后心脏炎症因子变化

目的:探讨冠状动脉搭桥术后心脏炎症对心功能的影响。方法:42例稳定型心绞痛患者行体外循环下冠脉搭桥术。体外循环运行前,心脏复跳后5、20min分别取动脉及冠状静脉窦血标本;检测白细胞介素(IL)-6、IL-8、IL-10,细胞间黏附分子-1(ICAM-1)和P-选择素(P-selectin)等炎症因子及乳酸水平。记录术后患者肌酸激酶同工酶(CK-MB)、肌钙蛋白-I变化及血流动力学资料。结果:体外循环前IL-6动脉血水平低于冠状静脉窦血水平(P<0.05)。ICAM-1及P-selectin水平高于冠状静脉窦水平(P<0.05)。主动脉开放心脏复跳后动脉血IL-6、IL-8、IL-10、ICAM-1及P-selectin水平与冠状静脉窦水平差别无统计学意义。主动脉开放后20minIL-6、ICAM-1桡动脉和冠状静脉窦血水平差值(CS-A)与术后12h心排指数呈弱负相关。体外循环前动脉血乳酸水平高于冠状静脉窦水平(差值,-0.14±0.25),再灌注阶段心脏乳酸高于体外循环前水平(差值,5min时,0.36±0.22;20min时,0.14±0.20,与术前比较,P<0.01)。主动脉开放后20min后经心乳酸(CS-A)与术后24、48h心肌酶呈正相关。结论:体外循环冠脉搭桥术后心脏炎症反应与术后心功能损害有关,抑制心肌炎症反应有可能改善术后心功能。     

体外循环心内手术主动脉开放前纯温血灌注的心肌保护效果

目的 探讨纯机器氧合血灌注诱复的心肌保护效果.方法 40例重症心脏瓣膜置换术患存均分两组,A组开放主动脉前用温血停搏液灌注+纯机器氧合血顺-逆灌注,待心脏复苏后再开放升主动脉;B组开放升主动脉前单用温血停搏液灌注后即开放升主动脉.于转流前、术毕、术后6 h和1、3、5 d取外周血测定心肌肌钙蛋白I(cTnI),记录心脏复跳、主动脉阻断、辅助循环、机械通气和ICU停留时间.结果 两组术后cTnI均较转流前增高,A组增高明显少于B组(P<0.01);A组自动复跳率高于B组,辅助循环、机械通气和ICU停留时间均短于B组(P<0.05).结论 主动脉开放前纯温血顺-逆灌注诱复后再开放方法有较好的心肌保护作用.     

白内障撕囊口控制环的临床应用价值分析

目的 评价白内障撕囊口控制环的临床应用效果。方法 选取60例(60眼)年龄相关性白内障患者为研究对象,按照随机数字表法分为A组与B组,每组30例(30眼)。A组行常规连续环形撕囊白内障超声乳化+折叠式人工晶状体植入术, B组在白内障撕囊口控制环辅助下行连续环形撕囊白内障超声乳化+折叠式人工晶状体植入术。比较两组撕囊口合格率、人工晶状体轻度偏移情况、视力、眼压,以及术中和术后并发症发生情况。结果 两组均顺利完成连续环形撕囊。A组撕囊口合格24眼(80.0%), B组合格30眼(100.0%)。B组撕囊口合格率高于A组,差异有统计学意义(P<0.05)。两组术后1个月人工晶状体轻度偏移率比较差异无统计学意义(P>0.05)。两组术后1 d、1周视力>0.5占比比较,差异无统计学意义(P>0.05)。术前, A组眼压为(14.17±2.47)mm Hg(1 mm Hg=0.133 kPa), B组为(14.60±2.97)mm Hg;术后A组眼压为(15.37±3.59)mm Hg, B组为(15.63±3.05)mm Hg。手术前后两组眼压比较差异无统计学意义(P&...     

药物联合双侧顺行性脑灌注在中低体温停循环A型主动脉夹层手术脑保护中的临床研究

目的：探讨药物联合双侧选择性顺行脑灌注对中低体温停循环(MHCA)A型主动脉夹层(TAAD)患者的脑保护作用。方法：选择赣南医学院第一附属医院2021年1月—2022年2月收治的TAAD行孙氏手术患者90例,采用简单随机数字表法分为A组[采用单侧选择性顺行脑灌注(UASCP)]、B组[采用双侧选择性顺行脑灌注(BASCP)]及C组[药物(精氨酸+硫酸镁+丙泊酚)联合BASCP]三组,每组30例,比较三组治疗效果。结果：三组手术时间、术后ICU停留时间、术后麻醉清醒时间、术后出现短暂性神经功能缺损(TND)例数及中国临床神经功能缺损程度(CSS)评分>16分的例数比较,差异有统计学意义(P<0.05)。与A组患者相比,B组患者手术时间、体外循环时间明显减少,C组患者手术时间明显增加(P<0.05);A组术后ICU停留时间长于C组(P<0.05);A组与B组患者术后出现TND例数、CSS评分大于16分的例数均多于C组(P<0.05);A组与B组患者术后清醒时间均长于C组(P<0.05)。结论：药物联合双侧顺行选择性脑灌注(BASCP)方案可有效缩短MHC...     

血浆趋化因子受体CCR1在急性冠脉综合征患者围术期强化他汀治疗中的作用

目的观察负荷量阿托伐他汀对急性冠脉综合征(ACS)患者经皮冠状动脉介入治疗(PCI)术后的影响及血浆CC趋化因子受体1(CCR1)在其中的作用。方法 120例ACS患者随机均分为试验组和对照组,试验组入院后30min内给予阿托伐他汀80mg,PCI术当日起40mg/d,30d后改为20mg/d;对照组入院后起即给予阿托伐他汀20mg/d。观察两组围术期心肌梗死及30d主要不良心血管事件(MACE)的发生率;ELISA法检测术前、术后24h、1、2、4周血浆CCR1水平。结果试验组围手术期心肌梗死发生率明显低于对照组(5.00%vs.23.33%)(P<0.01);30dMACE发生率低(3.33%vs.15.00%)(P<0.05)。与PCI术前比较,对照组术后24h血浆CCR1明显升高(P<0.01);两组术后1、2、4周两组CCR1的水平均明显下降(P<0.01),试验组低于对照组(P<0.01)。结论术前强化阿托伐他汀治疗显著降低ACS患者PCI术后CCR1水平,从而减少围手术期心肌梗死和30dMACE发生率。     

Effects of nitroglycerin on regional myocardial function in the underperfused canine heart

Effects of nitroglycerin (3 micrograms/kg/min i.v.) on regional myocardial contractility during acute coronary stenosis were studied in open-chest dogs using a strain-gauge arch. Stenosis-induced stepwise decreases in coronary perfusion pressure (CPP) at less than 40 mm Hg correspondingly reduced contractility in the underperfused area and increased the left ventricular end-diastolic pressure (LVEDP). Nitroglycerin caused significant increases in contractility, along with decreases in arterial and left ventricular pressures; at stenosis-induced CPP less than 30 mm Hg, contractility in the underperfused are fell precipitously below the control, while LVEDP increased. When nitroglycerin infusion under coronary stenosis (CPP of 40 mm Hg) decreased CPP to less than 30 mm Hg, contractility fell. When CPP greater than 30 mm Hg was maintained, contractility increased and LVEDP decreased. In conclusion, at least in the absence of well-developed collateral circulation, the critical level of CPP was 40 mm Hg for contractility and LVEDP without nitroglycerin, which shifted to 30 mm Hg with the addition of nitroglycerin. Nitroglycerin resulted in a significant increase in plasma catecholamines, and the increase in contractility diminished with propranolol, indicating participation of beta-adrenoceptor in the positive inotropic effect of nitroglycerin. However, catecholamines at high concentrations probably further aggravated the impaired cardiac function at CPP less than 30 mm Hg.     

Evaluation of the effect of myocardial perfusion after percutaneous coronary intervention in coronary artery disease by using intracoronary myocardial contrast echocardiography and two other angiographic techniques

Detection of abnormal myocardial perfusion is crucial to the prognosis of patients with coronary artery disease (CAD) after they have undergone percutaneous coronary intervention (PCI). The objective of this study is to evaluate the effect of myocardial perfusion by three different methods—intra-coronary myocardial contrast echocardiography (ICMCE), corrected thrombolysis in myocardial infarction frame count (CTFC), and coronary blood flow velocity (BFV)—and to determine the value of these different methods in the evaluation of the effect of myocardial perfusion post-PCI. For the study sixty-eight patients were divided into four groups based on selective coronary angiography results: group A (normal coronary artery), group B (75%–95% coronary artery stenosis), group C (coronary artery stenosis >95%) and group D (acute total coronary occlusion). The effect of myocardial reperfusion was evaluated using the above mentioned three methods 15 min after PCI. IC-MCE was also performed before PCI in group D. The quantitative parameters of MCE involved: contrast peak intensity, time to peak intensity and area under the curve, representing myocardial blood volume, reperfusion velocity and myocardial blood flow, respectively. No difference was found in CTFC between the coronary artery stenosis group and the normal group. BFV was slower in group D than in group A(P < 0.05). The myocardial blood volume and the myocardial blood flow of the IC-MCE quantitative parameters were markedly lower in group C compared with those in group A (P < 0.05), and there were significant differences in the three MCE parameters between group D and group A (P < 0.05). For those patients with acute or total occlusion, the levels of myocardial perfusion before and after PCI were similar, as determined by IC-MCE and visually analyzed from 61 segments (P < 0.05). Quantitative IC-MCE evaluation of myocardial reperfusion is more accurate than with the other two methods. Moreover, with qualitative IC-MCE the level of myocardial reperfusion can be viewed directly and rapidly. Thus, the IC-MCE method is of great value to coronary artery disease (CAD) patients undergoing PCI, especially for those with acute myocardial infarction (AMI).     

腹腔镜阑尾切除术不同CO_2气腹压力对局部疼痛的影响观察

目的探讨腹腔镜阑尾切除术（LA）不同CO2气腹压力对局部疼痛的影响。方法将本院117例行LA的患者随机分为3组,每组39例,A组气腹压力为10mm Hg,B组气腹压力为12mm Hg,C组气腹压力为15mm Hg,比较3组术后肩部疼痛发生率及疼痛程度。结果 117例患者均顺利完成LA手术,无中转开腹病例。A组术后肩部疼痛程度与B组和C组比较均差异有统计学意义（P〈0.05）,B组与C组比较,差异无统计学意义（P〉0.05）。结论 LA术后局部疼痛可能与人工气腹张力有关,在10mm Hg低压气腹下行LA,可显著降低LA术后局部疼痛情况。     

左-卡尼汀心停搏液对犬体外循环心肌的保护作用

目的研究左-卡尼汀(L-CN)心停搏液冠状动脉间断顺行灌注对犬体外循环(CPB)心肌的保护作用。方法20只♂健康成年杂种犬,随机分为实验组和对照组,每组n=10。实验组术中于4℃ST.Thomas Ⅱ心停搏液中按12g·L-1加入L-CN;对照组以等量生理盐水代替L-CN加入ST.Thomas Ⅱ号冷晶体液作为心停搏液,其它条件同治疗组。升主动脉每阻断30min灌注1次,共4次,末次灌注液中氯化钾浓度减半。结果①升主动脉阻断时,两组冠状静脉窦血清心肌肌钙蛋白I(cTnI)、肌酸激酶MB同工酶(CK-MB)水平,左心室心肌丙二醛(MDA)和三磷酸腺苷(ATP)含量以及超氧化物歧化酶(SOD)活性比较差异无统计学意义(P>0.05);升主动脉开放时,实验组cTnI、CK-MB和MDA均低于对照组(P<0.05或P<0.01),SOD和ATP则高于对照组(P<0.05)。②与对照组比较,实验组术毕心脏自动复跳率明显升高(P<0.01)。③Western blot法分析腺苷二磷酸-核糖多聚酶(PARP)的裂解情况,两组术毕心肌均有PARP完整的113ku被水解为89ku的片段,但实验组被水解的PARP完整片段明显少于对照组。结论L-CN心停搏液通过改善CPB心肌的能量代谢,降低心肌细胞毒性产物的生成,减少心肌细胞凋亡,从而达到较好的心肌保护作用。     

麝香保心丸联合冠脉内注射尼可地尔对STEMI患者PPCI术后心肌血流灌注及近期预后的影响

目的观察麝香保心丸联合冠脉内注射尼可地尔对ST段抬高型心肌梗死(ST-segment elevation myocardial infarction,STEMI)患者PPCI术后心肌血流灌注及近期预后的影响。方法入选2017年1月至2018年1月就诊联勤保障部队第九〇〇医院行直接经皮冠状动脉介入治疗(PPCI)术后的STEMI患者共151例,按随机数字法分为常规治疗组(A组)51例、冠状动脉内注射尼可地尔组(B组)50例和麝香保心丸+冠状动脉内注射尼可地尔组(C组)50例。比较术中校正的TIMI帧数(corrected TIMI frame count,cTFC)、术后TIMI 3级血流比例、2 h心电图ST段回落>50%指数、住院期间主要心血管不良事件(major adverse cardiovascular events,MACE)发生率以及术后3个月内心绞痛等级和MACE发生率等指标。结果 B、C组在术中即刻c TFC、术后2 h心电图ST段回落>50%指数均优于A组(P<0.05),C组结果优于B组;术后3个月内心绞痛分级C组优于A、B组(P<0.05)...     

Pretreatment with captopril improves myocardial recovery after cardioplegic arrest.

Among the interventions designed to limit postischemic oxidative injury, those that enhance the myocardial content of thiol groups are attractive because thiols are powerful antioxidant. Indeed, part of the protection afforded by the angiotensin-converting enzyme (ACE) inhibitor captopril in regional myocardial ischemia is attributed to its thiol group. This study assesses the effects of captopril in a surgically relevant model of global ischemic arrest. Thirty rats were implanted subcutaneously (s.c.) with osmotic pumps that allowed continuous delivery of captopril (total dose 75 mg), enalapril (a nonthiol-containing ACE inhibitor, total dose 7.5 mg) or saline in 48 h. Drug concentrations were equipotent in their effect on angiotensin I (ANGI) pressor response. Hearts were then excised, perfused under isovolumic conditions, and subjected to 90-min cardioplegic arrest at 30 degrees C followed by 1-h reperfusion. Pre- and postischemic coronary flows were significantly higher to a similar extent in the two drug-pretreated groups than in controls. However, captopril-pretreated hearts had the best recovery of contractility (dP/dtmax; 3,590 +/- 74 versus 2915 +/- 64 mm Hg s-1 in the enalapril group, p less than 0.001), and diastolic pressure (13.7 +/- 0.9 mm Hg vs. 20.0 +/- 1.6 mm Hg in the enalapril group, p less than 0.05). We conclude that pretreatment with ACE inhibitors improves myocardial recovery after cardioplegic arrest and that captopril is more effective than enalapril. The additional protection afforded by captopril was not flow mediated, suggesting that the cardioprotective effects of this drug not only involve an ACE inhibition-dependent coronary vasodilation but could be related to a thiol-dependent limitation of oxidative injury.     

替罗非班在血栓抽吸前后使用对急性ST段抬高型心肌梗死患者的影响

目的比较在急性ST段抬高心肌梗死(STEMI)患者急诊经皮冠状动脉介入(PCI)术中,血栓抽吸导管前后使用替罗非班对心肌再灌注水平、术后不良事件的影响。方法 153例接受急诊PCI术的急性STEMI患者,造影证实病变处有明显血栓负荷后,将患者随机分为A、B 2组,A组80例患者为血管造影后使用替罗非班,再进行血栓抽吸,最后行PCI治疗,B组73例为血管造影后行血栓抽吸,再使用替罗非班,最后行PCI治疗。比较2组心肌再灌注水平、不良事件发生率。结果 A组和B组患者在心肌呈色分级、出院时射血分数(EF)值方面有显著性差异,A组患者显示有较好的预后。但2组间心肌梗死溶栓(TIMI)血流、校正的心肌梗死溶栓帧数(CT-FC)、ST段回落率、住院期间不良事件发生率差异无统计学意义(P>0.05)。结论在接受急诊PCI术的急性STEMI患者中,血栓抽吸前使用替罗非班较血栓抽吸后使用对改善心肌再灌注及出院时的EF值有利。     

Effect of antiischemic therapy on coronary flow reserve and the pressure-maximal coronary flow relationship in anesthetized swine.

The effect of nifedipine (0.5, 1.0, and 2.0 micrograms/kg/min), metoprolol (0.1, 0.5, and 1.0 mg/kg), the beta 1-selective adrenoceptor partial agonist epanolol (10, 50, and 200 micrograms/kg), or equivalent volumes of isotonic saline (n = 6, in each group), on coronary blood flow capacity were studied in anesthetized swine. Intracoronary bolus injections of adenosine (20 micrograms/kg/0.2 ml) were administered without and during three levels of coronary stenosis, prior to and following each dose of drug, to obtain maximal coronary blood flows at different perfusion pressures in the autoregulatory range. Coronary perfusion pressures were varied by partial inflation of a balloon around the left anterior descending coronary artery. Special care was taken that the stenoses not lead to myocardial ischemia. Three indices of coronary blood flow capacity were used: absolute coronary flow reserve (ACFR, the ratio of maximal to resting coronary blood flow), the slope and the extrapolated pressure at zero flow (Pzf) of the pressure-maximal coronary flow (PMCF) relationship, and relative coronary flow reserve (RCFR, the ratio of maximal coronary blood flow with a stenosis to maximal coronary blood flow without a stenosis) at two of the three levels of stenosis. Nifedipine decreased ACFR from 4.5 +/- 1.9 to 1.9 +/- 0.3 (mean +/- SD; p less than 0.05), reflecting in part the increase in resting coronary blood flow. The nifedipine-induced changes in maximal coronary blood flow were not only due to a drop in perfusion pressure, as the slope of the PMCF relationship decreased from 2.27 +/- 0.49 ml/(min.mm Hg) to 1.54 +/- 0.51 ml/(min.mm Hg) (p less than 0.05), and Pzf decreased from 30 +/- 4 mm Hg to 20 +/- 7 mm Hg (p less than 0.05). Consequently, calculated maximal coronary blood flow was attenuated from 114 +/- 31 ml/min to 93 +/- 37 ml/min at 80 mm Hg, but was enhanced from 23 +/- 13 to 37 +/- 24 ml/min at 40 mm Hg coronary perfusion pressure. In concert with the change in the PMCF relationship, RCFR at equivalent severe stenosis increased from 0.33 +/- 0.06 to 0.47 +/- 0.10 (p less than 0.05). No changes were observed with metoprolol, epanolol, or saline. The effect of nifedipine on the PMCF relationship not only provides a mechanism for the drug's antiischemic action, but should also be considered in the interpretation of coronary flow reserve measurements in patients on nifedipine treatment.