Experimental myocardial infarction: II. Acute depression and subsequent recovery of left ventricular function: serial measurements in intact conscious dogs

Acute myocardial infarction causes depression of left ventricular function, but the capacity of the ventricle to recover from such an injury remains unknown. This problem was explored by measuring left ventricular function in eight intact conscious dogs before, 1 hr after, and again 6-8 days after myocardial infarction. Acute myocardial infarction was produced using a technique which entails gradual inflation over an average period of 1 hr of a balloon cuff previously implanted around the left anterior descending coronary artery. Occurrence of anterior wall infarction was detected electrocardiographically and later confirmed by postmortem examination. Left ventricular function was evaluated from the relationship between left ventricular developed pressure (left ventricular peak systolic pressure minus left ventricular end-diastolic pressure) and left ventricular end-diastolic pressure during transient aortic occlusion with a balloon catheter. Left ventricular function curves were obtained by plotting left ventricular-developed pressure at increasing left ventricular end-diastolic pressures up to 50 mm Hg. Acute myocardial infarction caused marked depression of left ventricular function measured 1 hr after onset of infarction, but 1 wk later all eight animals showed improvement with return of function toward the control levels. A small but significant descending limb was noted at left ventricular end-diastolic pressures above 35 mm Hg. Quantitatively, the descending limb was similar before, 1 hr after, and 1 wk after myocardial infarction. Hemodynamic data revealed evidence of left ventricular failure in all animals, but variability in individual hemodynamic parameters was noted. The data indicate that the marked depression of left ventricular function observed immediately after experimental acute myocardial infarction undergoes considerable resolution within 1 wk, but that functional recovery remains incomplete.     

Experimental myocardial infarction: VI. Efficacy and toxicity of digitalis in acute and healing phase in intact conscious dogs

Use of digitalis in myocardial infarction is controversial. To determine the efficacy and toxic threshold, serial infusions of 3 μg/kg per min of acetyl-strophanthidin were given to six intact conscious dogs 24 hr before and 1 hr, 2 days, and 7 days after myocardial infarction induced by inflation of a balloon cuff implanted on the left anterior descending coronary artery. Within 1 hr after myocardial infarction, heart rate increased by 28%. Left ventricular end-diastolic pressure increased from 7 to 20 mm Hg, and stroke volume decreased by 25%. At this time acetylstrophanthidin caused no beneficial hemodynamic change, 1 wk later, the heart rate and left ventricular end-diastolic pressure had declined toward normal but remained elevated. At this time, acetylstrophanthidin lowered left ventricular end-diastolic pressure by 25%, and increased the stroke volume and cardiac output by 25% and 21% respectively, without any change in heart rate or aortic pressure. Tolerance to acetylstrophanthidin, defined as appearance of ventricular tachycardia, declined the 1st hr after myocardial infarction by 24% (P<0.05) from the control level of 43 ±4 μg/kg (SEM), but subsequently returned to control.     

Alterations in left ventricular diastolic function in conscious dogs with pacing-induced heart failure.

We investigated in conscious dogs (a) the effects of heart failure induced by chronic rapid ventricular pacing on the sequence of development of left ventricular (LV) diastolic versus systolic dysfunction and (b) whether the changes were load dependent or secondary to alterations in structure. LV systolic and diastolic dysfunction were evident within 24 h after initiation of pacing and occurred in parallel over 3 wk. LV systolic function was reduced at 3 wk, i.e., peak LV dP/dt fell by -1,327 +/- 105 mmHg/s and ejection fraction by -22 +/- 2%. LV diastolic dysfunction also progressed over 3 wk of pacing, i.e., tau increased by +14.0 +/- 2.8 ms and the myocardial stiffness constant by +6.5 +/- 1.4, whereas LV chamber stiffness did not change. These alterations were associated with increases in LV end-systolic (+28.6 +/- 5.7 g/cm2) and LV end-diastolic stresses (+40.4 +/- 5.3 g/cm2). When stresses and heart rate were matched at the same levels in the control and failure states, the increases in tau and myocardial stiffness were no longer observed, whereas LV systolic function remained depressed. There were no increases in connective tissue content in heart failure. Thus, pacing-induced heart failure in conscious dogs is characterized by major alterations in diastolic function which are reversible with normalization of increased loading condition.     

Experimental myocardial infarction: IV. Reduction of left ventricular compliance in the healing phase

Compliance of the infarcted left ventricle was studied in dogs 3-5 days after occlusion of the left anterior descending coronary artery. Compliance was assessed from postmortem pressure-volume curves and from pressure-length measurements (mercury-in-silastic segment length gauges) made both in vivo and postmortem. Postmortem pressure-volume curves showed reduced compliance compared to sham-operated animals. Postmortem pressure-length curves of infarcted and adjacent normal myocardium indicated that the diminished total compliance could be attributed to an increase in stiffness of the infarcted area. This was confirmed by in vivo end-diastolic pressure-length changes produced by transient aortic occlusion. The infarcted area was akinetic, showing neither contraction nor aneurysmal bulging. In addition, anesthetized dogs with infarcts, when compared with sham-operated animals, had similar left ventricular end-diastolic volumes (indicator dilution method), but higher left ventricular end-diastolic pressures. Taken with previous observations, which show that systolic aneurysmal bulging is uniformly present at the onset of ischemia, these results indicate that stiffening of the ischemic myocardium occurs during the first 5 days after infarction, and show that elevation of left ventricular filling pressure does not necessarily signify ventricular dilatation. The results also suggest a mechanism whereby ventricular performance may improve during recovery from acute myocardial infarction.     

急性心肌梗死晚期再灌注对左室重构及心功能的影响

目的　探讨Q波型前壁心肌梗死恢复期开通梗死相关冠状动脉对左室重构 (LVRM )及心功能的影响。方法　选择 4 0例近期首次发生过Q波型前壁心肌梗死且造影显示供血区供血冠状动脉闭塞者作为研究对象 ,按前瞻性随机方式分组 ,治疗组患者心肌梗死后 4周内行冠状动脉内支架置入术 ;对照组患者心肌梗死后不作支架术。均于梗死后 4周和 2 4周进行超声心动图观察。分别测定左室舒张末期容量(LVEDV)、左室收缩末期容量 (LVESV)、左室射血分数 (LVEF)。结果　心肌梗死后均可发生明显左室重构 ;治疗组 2 4周与 4周时对比 ,LVEDV与LVESV均减小 (P <0 .0 5 ) ,而LVEF升高 (P <0 .0 5 ) ,LVRM与心功能明显改善 ,治疗组 2 4周时与对照组比较 ,以上指标有显著性差异 (P <0 .0 5 ) ;对照组 2 4周与梗死后 4周比较无显著性差异 (P >0 .0 5 )。结论　晚期恢复梗死相关动脉可明显减轻或逆转Q波型前壁心肌梗死患者的LVRM ,明显改善左心室功能。     

Effects of carbon dioxide and pH on myocardial function in dogs with acute left ventricular failure

The present study was undertaken to examine the effects of changes in PaCO2 and pHa on myocardial blood flow and central hemodynamics during acute ischemic left ventricular failure. Six closed-chest dogs anesthetized with pentobarbital were hyperventilated, and CO2 was added to the inspiratory gas to induce: a) normocapnia, b) hypocapnia, c) hypercapnia, and d) hypercapnia with sodium carbonate given to correct pH. Embolization of the left coronary artery with 50-microns microspheres resulted in deterioration of left ventricular function, as indicated by increased left ventricular end-diastolic pressure and mean pulmonary arterial pressure, while cardiac output decreased. During hypocapnia with left ventricular failure, the central hemodynamics remained unchanged, while a minor but nonsignificant decrease in myocardial blood flow was observed. Hypercapnia aggravated the heart failure, as indicated by increased left ventricular end-diastolic pressure, mean right atrial pressure, and mean pulmonary arterial pressure; however, the pump function of the heart was unchanged, as demonstrated by the unaltered cardiac output, heart rate, and mean aortic blood pressure. The changes in the central hemodynamics were reversed when pH was normalized during hypercapnia. Thus, in the present study pH, and not PaCO2, was responsible for the hemodynamic deterioration observed during hypercapnia in the failing heart.     

Residual left ventricular pump function after acute myocardial infarction in NIDDM patients.

OBJECTIVE--Left ventricular remodeling occurs immediately after MI, involving structural changes in noninfarcted segment. However, the residual left ventricular pump function in NIDDM patients after acute MI has not been clarified. The purpose of this study was to evaluate the difference in the process of left ventricular remodeling between NIDDM and nondiabetic patients. RESEARCH DESIGN AND METHODS--Left ventricular regional EF images obtained by radionuclide angiography were investigated in 20 NIDDM and 29 nondiabetic patients the 3rd wk after acute MI. RESULTS--Regional EF of the noninfarcted area and P/V had a significant hyperbolic relation with left ventricular EDV in both groups of patients. Despite no difference in the extent of myocardial necrosis and the number of coronary vessels diseased between NIDDM and nondiabetic patients, regional EF of the noninfarcted area and P/V were significantly lower when left ventricular EDV increased in NIDDM patients compared with nondiabetic patients. CONCLUSIONS--Pathogenetic changes of the residual myocardium associated with NIDDM may adversely influence the process of left ventricular remodeling after MI, especially in patients with increased left ventricular EDV.     

急性心肌梗死首次发作后左室非同步运动对左室功能早期改变的影响

目的探讨急性心肌梗死患者左室非同步运动是否可作为左室射血分数(LVEF)降低的一个独立影响因素。方法急性心肌梗死首次发作患者(梗死组)47例,经皮冠状动脉介入治疗术后2~4 d,实时三维超声心动图观测左室舒张末容积(LVEDV)、左室收缩末容积(LVESV)、LVEF及左室非同步指数(SDI)。体检健康者35例作为对照组。结果与对照组比较,梗死组LVESV、SDI增高,LVEF减低(均P0.01),SDI与LVEF呈负相关(r=-0.948,P0.01)。多重线性回归分析,与LVEF相关的因素有体质量、心电图ST段改变、冠状动脉病变条数、LVEDV、LVESV及SDI。结论患者体质量、心电图ST段异常、冠状动脉病变条数、LVEDV、LVESV及SDI均可作为可作为评估、预测左室功能的重要指标,尤以心电图ST段异常及SDI影响较大。     

Pre-ejectional left ventricular wall motions studied on conscious dogs using Doppler myocardial imaging: relationships with indices of left ventricular function

Duration of the pre-ejection period is a sensitive index of myocardial function. Our purpose was to document normal pre-ejectional left ventricular (LV) wall motions at rest and under dobutamine using Doppler myocardial imaging (DMI), and to correlate posterior wall velocities with indices of LV systolic function. M-mode recordings of both walls were imaged on eight conscious dogs chronically instrumented. Subendocardial pre-ejectional velocities were digitized and measured every 3.8 ms. DMI analysis consisted of sign recognition, velocity measurement, duration and timing from the Q wave of the electrocardiogram. Isovolumic contraction time (Ict) was represented by the time interval from onset to peak of the first derivative of LV pressure. Conventional Doppler labelling of velocity signs, positive toward and negative away from the transducer, was applied to the direction of encoded wall motions. For physiological understanding, wall motions of both walls were also labelled inward and outward with respect to the left ventricular cavity center. In each wall, PEP was shown as several colored strips, each strip representing the period of time that the wall was moving in one direction. Changes in velocity sign corresponding to changes in direction of motion were opposed in each wall (p < 0.001), featuring successive inward and outward wall motions. There was a markedly sustained inward motion during Ict. Its velocity amplitude increased with dobutamine. There was a positive correlation between velocities of the inward motion contemporaneous of Ict and ejection fraction (r = 0.72, p < 0.003). Values of Ict respectively drawn from DMI and from hemodynamics were also significantly correlated (r = 0.85, p < 0.007). Thus, the inward motion evidenced by DMI during Ict appears promising to assess myocardial function and effect of drugs.     

多普勒超声心动图对急性心肌梗死患者左室舒张功能的评价

目的:采用多普勒超声心动图对急性心肌梗死(AMI)患者左室舒张功能(LVDF)的测定,判断心肌梗死面积和恢复情况,从而了解预后。方法:应用3.25MHz探头对21例AMI患者急性期和恢复期分别行二尖瓣口血流频谱(MVFP)和肺静脉血流频谱(PVFP)检测。结果:AMI患者MVFP中急性期较恢复期舒张早期流速(E峰)增加,舒张晚期流速(A峰)下降,E/A比值增大以限制性异常(左房压增高)充盈波形表现为主;有14例(66.7%)E/A>1.6,DT和IVRT短于恢复期,提示心梗面积较大,左室顺应性降低,舒张功能异常,病情严重。恢复期E峰较急性期降低,A峰则增加,E/A比值下降以松弛性异常(主动舒张迟缓)充盈波形表现为主,有18例(85.7%)E/A<0.8,说明治疗后随着心肌梗死的恢复,梗死心肌愈合,左室舒张功能逐渐改善,提示病情的好转。PVFP中急性期和恢复期S波均相似文献   

Immediate effects of captopril in acute left ventricular failure secondary to myocardial infarction

Abstract. In eight patients with acute left ventricular failure secondary to myocardial infarction the haemo-dynamic effects of captopril (25 mg), an orally active converting enzyme inhibitor, were measured. Haemo-dynamic modifications were maximal at 60 min and lasted for 2–3 h. Pulmonary wedge pressure fell from 23–5± 4.9(mean ± SD)to 16–8 ± 4.7 mmHg(P<0–01), cardiac output rose from 3–24 ± 1 to 4–05 ± 0–91 1/min (P<001). Systemic vascular resistance decreased from 27–34 ± 3–81 to 17.52 ± 1–65 mmHg min 1^-1 (P<001). Mean arterial pressure fell from 89.6 ± 13.9 to 75.7±0 16.3 mmHg (P<0001) while heart rate was not significantly modified. Six patients who had high pretreatment plasma renin activity values responded by a decrease in ventricular filling pressure and/or an increase in cardiac output. One patient with normal initial plasma renin activity value showed similar haemodynamic effects. These data suggest that in the short term captopril is a vasodilator with both arterial and venous effects and improves cardiac function in acute left ventricular failure secondary to myocardial infarction.     

Left ventricular function in acute myocardial infarction

Left ventricular catheterization was carried out in 40 patients with acute myocardial infarction. Left ventricular end-diastolic pressure (LVEDP) was elevated in 85% of the patients studied. In 14 patients with apparently uncomplicated infarcts, LVEDP averaged 15 mm Hg, and cardiac index (2.98 liter/min/m(2)), stroke volume (38.3 ml/m(2)), and stroke work (49.2 g-m/m(2)) were within normal limits. In 12 patients with clinical signs of left ventricular failure, LVEDP averaged 29.9 mm Hg, cardiac index was at the lower limit of normal (2.79 liter/min/m(2)), but stroke volume (31.6 ml/m(2)) and stroke work (37.3 g-m/m(2)) were reduced. In 14 patients with clinical signs of shock, LVEDP averaged significantly lower than in the heart failure group (21.1 mm Hg), but cardiac index (1.59 liter/min/m(2)), stroke volume (16.5 ml/m(2)), and stroke work (11.1 g-m/m(2)) were markedly reduced. A large presystolic atrial "kick" (average amplitude 9.5 mm Hg) was an important factor in the high LVEDP in the patients with heart failure but not in those with shock. The first derivative of left ventricular pressure was significantly lower in shock than in the nonshock group. Although right atrial pressure (RAP) and LVEDP were significantly correlated (r = 0.49), wide discrepancies in individual patients rendered the RAP an unreliable indicator of the magnitude of left ventricular filling pressure.THESE DATA SHOW THE FOLLOWING: (a) LVEDP is usually elevated in acute myocardial infarction, even in absence of clinical heart failure; (b) cardiac output apparently is supported by increased LVEDP and compensatory tachycardia; (c) in patients with shock, left ventricular function usually is markedly impaired, but inadequate compensatory cardiac dilatation or tachycardia could contribute to the reduced cardiac output in some individuals; (d) lower LVEDP in shock than in heart failure may represent differences in left ventricular compliance.     

超声心动图对急性心肌梗塞后左心室结构和功能的评价

目的 动脉观察急性心肌梗塞后左室结构和功能的变化,评价溶栓治疗对梗塞后心室重构的影响。方法 对２８例首发急性心肌梗塞患者于梗塞后第４周和第１２周进行超声心动图观察。所测参数有：左室舒张末期和收缩末期容积指数（ＬＶＥＤＶＩ,ＬＶＥＳＶＩ）及射血分数（ＥＦ）。结果 急性心肌梗塞患者ＬＶＥＤＶＩ,ＬＶＥＳＶＩ均明显增高;栓组ＬＶＥＤＶＩ,ＬＶＥＳＶＩ无明显变化,ＥＦ升高,未溶栓组ＬＶＥＤＶＩ,ＬＶＥＳＶ     

Plasma YKL-40 and recovery of left ventricular function after acute myocardial infarction

Abstract

Background: Plasma YKL-40 is increased early in patients with ST-elevation myocardial infarction (STEMI). It is not known whether plasma YKL-40 is related to infarct size and recovery of ventricular function after primary percutaneous coronary intervention (PCI) of STEMI and whether granulocyte colony-stimulating factor (G-CSF) therapy influence plasma YKL-40 concentration. Materials and methods: A total of 72 patients (age: 56 ± 9 years (mean ± SD), 56 men and 16 women) with STEMI treated with PCI were included in a double-blind, randomized, placebo-controlled trial with subcutaneous G-CSF or placebo injections from day 1 to 7 after the STEMI. Plasma YKL-40, high-sensitivity C-reactive protein (hs-CRP) and CK-MB concentrations were measured at baseline and during the first month. Infarct size and left ventricular ejection fraction (LVEF) were measured by magnetic resonance imaging at baseline and after 6 months. Results: Baseline plasma YKL-40 was increased (median 92 μg/L) compared to healthy subjects (median 34 μg/L, p <0.001). In the placebo group hs-CRP and YKL-40 correlated at baseline (p = 0.04) and day 3 (p = 0.01), but not at day 7 and 30. Moreover, YKL-40 correlated negatively to LVEF recovery (p = 0.04) but not infarct size. G-CSF injections increased YKL-40 compared to placebo (p <0.001), but were not associated with infarct size or LVEF recovery. Conclusion: Plasma YKL-40 was significantly increased in STEMI patients at admission and G-CSF treatment caused a further increase in YKL-40. Plasma YKL-40 may be an indirect marker of LVEF recovery, independent of hs-CRP, and higher plasma YKL-40 indicates a lower recovery.     

位移曲线对犬正常及心肌梗死模型左室心肌局域功能的评价

目的通过研究犬心肌梗死模型左室局域心肌的位移曲线特征,寻求在生理和病理情况下评价心肌功能的合理量化指标.方法 27只犬采用开胸结扎冠状动脉左前降支复制心肌梗死模型;分别采集结扎前后心尖长轴不同切面(二腔、四腔、五腔)的各三个完整心动周期动态多普勒组织速度图;应用EchoPAC PC外置数字超声工作站同步获取左室心肌不同节段心肌组织位移曲线,记录每一位移曲线上长轴方向收缩期位移峰值及达峰值时间,计算等容舒张期开始时间、等容收缩期时间、等容舒张期时间.结果正常心肌位移曲线呈现规律性变化;梗死后前间隔、前壁各节段、后间隔近心尖部运动位移峰值与结扎前相比明显减低(P≤0.001);心梗后等容舒张期时相较结扎前明显延长(P＜0.05).结论位移曲线可以定量评价心肌梗死后局域心肌运动异常;位移峰值降低、等容舒张期时相延长可能是评价局部心肌梗死后局域心肌运动异常的早期敏感指标.     

Clinical course of acute myocardial infarction and left ventricular function in long-term epidural analgesia

The study of 76 patients with macrofocal myocardial infarction (MI) evaluated effects of epidural and standard analgesia on pumping capacity of the left ventricle (LV) and clinical course of MI. The study group consisted of 37 patients exposed to long-term morphine-clopheline epidural analgesia. In the control 39 patients analgesia was induced conventionally (intravenous injection of morphine). Both groups received the same routine treatment. Long-term morphine-clopheline epidural analgesia noticeably improves pumping LV function and clinical course of MI.     

Restrictive left ventricular diastolic filling identifies patients with heart failure after acute myocardial infarction.

Left ventricular diastolic filling was characterized by transmitral pulsed-wave Doppler velocities in 62 patients with acute myocardial infarction, and diastolic filling variables were correlated with the presence of clinical heart failure. At the time of admission, 47 patients were free of heart failure and 15 patients were in Killip class II to IV. In the latter group of patients with heart failure, peak velocity of late filling wave caused by atrial contraction (A) was lower (0.48 versus 0.59 m/sec, p < 0.05), ratio of peak velocity of early rapid filling wave to peak velocity of late filling wave caused by atrial contraction (E/A) was higher (1.5 versus 1.1, p < 0.01), and deceleration time (136 versus 196 msec, p = 0.0001) was shorter when compared with the patients not in heart failure after acute myocardial infarction. Multivariate analysis showed that the deceleration time was a powerful independent predictor of presence of heart failure after controlling for systolic functional variables. Therefore, diastolic filling variables can complement systolic functional variables in the identification of the patients with postinfarction left ventricular failure.     

三维与二维斑点追踪技术评价急性心肌梗死犬左心室局部收缩功能的实验研究

目的 探讨三维斑点追踪显像(3D-STI技术)评价急性心肌梗死犬左室局部收缩功能的应用价值.方法 对24只成年比格犬左冠状动脉前降支(LAD)结扎前、结扎180 min后分别行二维斑点追踪显像(2DD-STI)及3D-STI检查.实验结束后,行心肌氯化三苯基四氮唑(TTC)染色,确定梗死心肌节段和非梗死心肌节段,比较两者间纵向收缩期峰值应变(LS)的大小及运用2D-STI和3D-STI的耗时.结果 20只犬成功建立急性心肌梗死模型.结扎后梗死心肌节段2D-STI和3D-STI的LS均较结扎前的基础状态明显减低(P＜0.01),运用3D-STI存储和分析图像所用时间明显短于2D-STI(P＜0.01).3D-STI参数的ROC曲线下面积比2D-STI大.以3D-STI的LS值-12.56％为截点诊断急性心肌梗死的敏感性77.9％,特异性88.2％.结论 3D-STI可准确评价节段性室壁运动异常,是一种方便、准确的评价急性心肌梗死的新方法.     

Factors related to long-term prognosis following acute myocardial infarction. Importance of left ventricular function.

Factors related to 2-year and 4-year prognosis after acute myocardial infarction were studied in a series of 158 men. Stepwise multiple discriminant analysis was applied to findings recorded during hospital admission and to results of an exercise test carried out 6-8 weeks after the infarction. The best indicators for predicting a poor prognosis in the course of the following 2 years were a low systolic blood pressure on exercise and a palpable paradoxical cardiac pulsation. During the 4-year follow-up an abnormality of P terminal force in the ECG, which reflects left atrial overload, was the main predictor of poor prognosis.