Prognostic value of Doppler transmitral flow velocity patterns in acute myocardial infarction

Doppler transmitral flow patterns are partially dependent on age. We investigated the correlations between the age-adjusted transmitral flow patterns, hemodynamic indexes, and the coronary and clinical outcome in 206 patients with acute myocardial infarction (AMI) and 102 normal control subjects. The peak flow velocity at atrial contraction was significantly lower in 50 of the 206 patients (24%) (low-A group) than in the 102 normal controls. Pulmonary capillary wedge pressure was significantly higher in the low-A group than in the remaining 156 patients with AMI (20 +/- 7 vs 11 +/- 5 mm Hg, p <0.001), and the cardiac index and left ventricular ejection fraction were significantly lower (2.2 +/- 0.6 vs 2.9 +/- 0.7 L/min/m2, p <0.001; 38 +/- 15% vs 52 +/- 13%, p <0.001). The incidence of cardiogenic shock was significantly higher in the low-A group than in the other patients with AMI (42% vs 19%, p <0.001). Regression analysis demonstrated a significant association between decreased atrial filling velocity and increased in-hospital mortality as well as the incidence of heart failure in AMI (p <0.001). The 5-year mortality rate was also significantly higher in the low-A group (p <0.001). The age-adjusted transmitral flow pattern in AMI can identify patients with left ventricular dysfunction, which can lead to a poor prognosis.     

The relationship between the electrocardiographic pattern with TIMI flow class and ejection fraction in patients with a first acute anterior wall myocardial infarction

AIMS: The aim of this study was to assess the value of the electrocardiogram in predicting the patency of the left anterior descending artery and left ventricular ejection fraction in patients with a first acute anterior wall myocardial infarction at discharge from the coronary care unit. METHOD: We included 116 consecutive patients with an acute anterior myocardial infarction who had undergone coronary angiography and left ventriculography before discharge from the coronary care unit (7th to 10th day). The ST segment, either elevated or isoelectric (< 1 mm), and the T wave (positive or negative) in precordial leads V2-V4 were analysed and compared to the TIMI flow from each patient. RESULTS: Out of 69 patients with negative T waves, 38 (55%) had TIMI flow 3 compared with 20 (29%) and 11 (16%) with TIMI flow 2 and 0-1, respectively; and out of 47 patients with positive T waves seven (15%) had TIMI flow 3, 17 (36%) TIMI flow 2 and 23 (49%) TIMI flow 0-1 (P < 0.001). Out of 63 patients with an isoelectric ST segment, 35 (55%) had TIMI flow 3, 18 (29%) TIMI flow 2 and 10 (16%) TIMI flow 0-1, and out of 53 with ST segment elevation, 10 (19%) had TIMI flow 3, 19 (36%) TIMI flow 2 and 24 (45%) TIMI flow 0-1 (P < 0.001). When both parameters were analysed together, we found that in 46 patients with both isoelectric ST segments and negative T waves, 30 (65%) had TIMI flow 3 compared with two of 30 (7%) patients with ST segment elevation and positive T waves (P < 0.001). Patients with isoelectric ST segments had a better degree of left ventricular ejection fraction (57.8 +/- 14.1%) than patients with ST segment elevation (41.7 +/- 13%) (P < 0.001). Patients with positive and negative T waves had a similar left ventricular ejection fraction (49 +/- 18.1% vs 51 +/- 14%). CONCLUSION: We concluded that patients with a first acute anterior myocardial infarction and an electrocardiogram pattern of an isoelectric ST segment and a negative T wave have a higher incidence of a patent left anterior descending coronary artery than similar patients with ST segment elevation and a positive T wave. An isoelectric ST segment is also related to better left ventricular function.     

Influence of residual antegrade coronary blood flow on the long-term prognosis of medically treated patients with myocardial infarction and single-vessel disease

This is a review article concerning an influence of trematodes infections on a defence system of snails. Changes in: snails' plasma composition, a number of hemocytes, size of a hemopoietic organ, molecules secreted by hemocytes and defence cells activities caused by the infections are discussed in detail. The differences in humoral and cellular response between susceptible and resistant strains of snails as well as between young and old snails are also presented in the article. Finally, the problem of an existence of the specific immunological memory in snails is analyzed.     

Alpha-adrenergic blockade improves recovery of myocardial perfusion and function after coronary stenting in patients with acute myocardial infarction

BACKGROUND: AMI reperfusion by thrombolysis does not improve TIMI flow and LV function. The role of infarct-related artery (IRA) stenosis and superimposed changes in coronary vasomotor tone in maintaining LV dysfunction must be elucidated. METHODS AND RESULTS: Forty patients underwent diagnostic angiography 24 hours after thrombolysis. Seventy-two hours after thrombolysis, the culprit lesion was dilated with coronary stenting. During angioplasty, LV function was monitored by transesophageal echocardiography. Percent regional systolic thickening was quantitatively assessed before PTCA, soon after stenting, 15 minutes after stenting, and after phentolamine 12 microg/kg IC (n=10), the alpha1-blocker urapidil 600 microg/kg IV (n=10), or saline (n=10). Ten patients pretreated with beta-blockers received urapidil 10 mg IC. Coronary stenting significantly improved thickening in IRA-dependent and in non-IRA-dependent myocardium (from 27+/-15% to 38+/-16% and from 40+/-15% to 45+/-15%, respectively). Simultaneously, TIMI frame count decreased from 39+/-11 and 40+/-11 in the IRA and non-IRA, respectively, to 23+/-10 and 25+/-7 (P<0.05). Fifteen minutes after stenting, thickening worsened in both IRA- and non-IRA-dependent myocardium (to 19+/-14% and 28+/-14%, P<0.05), and TIMI frame count returned, in both the IRA and non-IRA, to the values obtained before stenting. Phentolamine and urapidil increased thickening to 36+/-17% and 41+/-14% in IRA and to 48+/-11% and 49+/-17% in non-IRA myocardium respectively, and TIMI frame count decreased to 16+/-6 and to 17+/-5, respectively. Changes were attenuated with beta-blocker pretreatment. CONCLUSIONS: Our finding that alpha-adrenergic blockade attenuates vasoconstriction and postischemic LV dysfunction supports the hypothesis of an important role of neural mechanisms in this phenomenon.     

Randomized comparison of coronary stenting with balloon angioplasty in selected patients with acute myocardial infarction

BACKGROUND: Although the benefits of primary angioplasty in acute myocardial infarction have been demonstrated, several areas for improvement remain. Therefore, a prospective randomized trial comparing primary stenting with balloon angioplasty in patients with acute myocardial infarction was conducted. METHODS AND RESULTS: Patients with acute myocardial infarction were randomly assigned to undergo either primary stenting (n=112) or balloon angioplasty (n=115). The clinical end points were death, recurrent infarction, subsequent bypass surgery, or repeat angioplasty of the infarct-related vessel. The overall mortality rate at 6 months was 2%. Recurrent infarction occurred in 8 patients (7%) after balloon angioplasty and in 1 (1%) after stenting (P=0.036). Subsequent target-vessel revascularization was necessary in 19 (17%) and 4 (4%) patients, respectively (P=0.0016). The cardiac event-free survival rate in the stent group was significantly higher than in the balloon angioplasty group (95% versus 80%; P=0.012). CONCLUSIONS: In selected patients with acute myocardial infarction, primary stenting can be applied safely and effectively, resulting in a lower incidence of recurrent infarction and a significant reduction in the need for subsequent target-vessel revascularization compared with balloon angioplasty.     

Intravascular ultrasound assessment of direct percutaneous transluminal coronary angioplasty in patients with acute myocardial infarction

BACKGROUND: Acute myocardial infarction is caused by sudden thrombotic occlusion of the coronary artery due to a previous rupture of atherosclerotic plaque. OBJECTIVE: To use intracoronary ultrasound measurements to evaluate lumen and plaque changes in patients with acute myocardial infarction. METHODS: Patients (n = 103) with acute myocardial infarction who had been scheduled to undergo primary percutaneous transluminal coronary angioplasty (PTCA) were selected. Both before and after successful coronary angioplasty, intracoronary 30 MHz ultrasound studies were performed using a 3.5F monorail catheter. The ultrasound catheter was successfully advanced into the occluded vessel segment without major complications prior to PTCA in 79 of 103 (76.7%) patients and after PTCA in 88 of 103 (85.3%) patients. RESULTS: The plaques were eccentric in 66 patients (83.5%). The plaque morphology was purely low echogenic in 14 (17.7%), highly echogenic in six (7.6%) and mixed in 59 (74.7%) patients. Partial (59 of 79, 74.7%) or ring-like calcification (3 of 79, 3.8%) was observed in 62 patients (78.5%). Plaque fissuring or dissection was detected prior to PTCA in 25 patients (31.7%). Coronary angioplasty successfully enlarged the inner luminal area from 2.1 +/- 0.7 to 7.4 +/- 1.9 mm2 (P < 0.01), whereas the plaque-thrombus area decreased significantly (13.8 +/- 1.7 mm2 before and 9.0 +/- 1.9 mm2 after PTCA; P < 0.01). The total vessel area remained virtually constant (15.9 +/- 1.9 mm2 before and 16.4 +/- 2.5 mm2 after PTCA, NS). PTCA-induced plaque rupture or dissection was observed in only 13 (16.5%) patients. CONCLUSION: Intracoronary ultrasound imaging can be performed safely and successfully prior and subsequent to PTCA in selected patients with acute myocardial infarction. Early reperfusion via PTCA seems to be attributable to a significant reduction in the amount of low-echogenic plaque and thrombus material, whereas factors like balloon-induced dissection and stretching of vessels play only a minor role.     

The effect of batroxobin on coronary segmental resistance and coronary blood flow in acute myocardial ischemic dogs

To study the effects of batroxobin on coronary circulation and cardiac performance in acute myocardial ischemia, Batroxobin was given intravenously to dogs with experimental coronary stenosis. A dose-dependent increase of coronary blood flow (CBF) was observed. Forty minutes after batroxobin (2 BU.kg-1 at infusion rate 0.1 BU.kg-1.min-1) administration, CBF increased by 12% (P < 0.05), small coronary resistance(RS) decreased from 4.1 +/- 0.5 to 3.2 +/- 0.5 mmHg.min.ml-1 (P < 0.01), while large coronary resistance(RL) changed insignificantly from 3.9 +/- 0.8 to 3.8 +/- 0.7 mmHg.min.ml-1 (P > 0.05). Two hours following drug administration, the changes in CBF, RS and RL still remained and RT decreased by 13% (P < 0.05). The + LV(dp/dt)max and -LV(dp/dt)max increased by 14% and 16% (P < 0.05) respectively compared with those in control group. It is concluded that batroxobin improves the ischemic canine coronary circulation and cardiac performance by way of lowering the small coronary resistance and thus increasing CBF. The data also suggest the benificial effect of batroxobin in acute myocardial ischemia.     

Relation among stenosis severity, myocardial blood flow, and flow reserve in patients with coronary artery disease

BACKGROUND: Coronary arteriography is considered the "gold standard" for evaluating the severity of a coronary stenosis. Because the resistance to blood flow through a stenotic lesion depends on a number of lesion characteristics, the physiological significance of coronary lesions of intermediate severity is often difficult to determine from angiography alone. This study of patients with coronary artery disease seeks to determine the relation between myocardial blood flow and flow reserve measured by positron emission tomography (PET) and the percent area stenosis on quantitative coronary arteriography. METHODS AND RESULTS: We studied 28 subjects: 18 patients with coronary artery disease (66 +/- 8 years) and 10 age-matched healthy volunteers (64 +/- 13 years) with dynamic N-13 ammonia PET imaging at rest and after dipyridamole (0.56 mg/kg). The percent cross-sectional area stenosis was quantified on the coronary arteriograms as described by Brown et al. In the 18 patients, a total of 41 non-infarct-related coronary vessels were analyzed. Myocardial blood flows in normal regions of patients with coronary artery disease were not different than those in healthy volunteers, both at rest and after dipyridamole. As a result, the myocardial flow reserve was also similar in both groups (2.4 +/- 0.4 versus 2.6 +/- 0.7, respectively; P = NS). Quantitative PET estimates of hyperemic blood flow (r = .81, P < .00001), flow reserve (r = .78, P < .00001), and an index of the "minimal coronary resistance" (r = .78, P < .00001) were inversely and nonlinearly correlated with the percent area stenosis on angiography. Of note, PET estimates of myocardial flow reserve successfully differentiated coronary lesions of intermediate severity (50% to 70% and 70% to 90%; 2.4 +/- 0.4 versus 1.8 +/- 0.5, respectively; P = .04). CONCLUSIONS: In patients with coronary artery disease, non-invasive measurements of myocardial blood flow and flow reserve by PET are inversely and nonlinearly related to stenosis severity as defined by quantitative angiography. Importantly, coronary lesions of intermediate severity have a differential flow reserve that decreases as stenosis increases that can be detected noninvasively by PET, thus allowing better definition of the functional importance of known coronary stenosis.     

Noninvasive prediction of residual blood flow within the risk area during acute myocardial infarction: a multicenter validation study of patients undergoing direct coronary angioplasty

BACKGROUND: In a previous study from a single center, radionuclide measures of collateral flow with technetium 99m sestamibi have been shown to be significantly associated with angiographic residual (antegrade and collateral) flow and independent predictors of final infarct size in acute myocardial infarction. This study examined whether the previously described radionuclide measures of blood flow to the infarct zone were reproducible with different laboratories and imaging systems. METHODS AND RESULTS: Residual flow to the infarct zone was assessed by both invasive and noninvasive methods in 77 patients with first-time myocardial infarction (32 anterior, 45 nonanterior). All patients underwent acute coronary angiography before any intervention within 8 hours of the onset of chest pain (4.0 +/- 1.5 hours; range 1.2 to 7.9 hours). 99mTc sestamibi was injected intravenously before reperfusion therapy, and tomographic imaging was performed 1 to 6 hours after injection. A central core laboratory processed the acquired images from three centers, each with a unique camera and computer system. Three previously published methods based on the severity of the acute perfusion defect were used to measure residual flow to the infarct zone (nadir, severity index, area). Antegrade (Thrombolysis in Myocardial Infarction flow) and collateral flow before direct angioplasty were blindly graded on a four-point scale (0 to 3) from the acute angiogram. The simple sum of the two grades was defined as the angiographic flow index, representing residual flow to the jeopardized zone. All three noninvasive measures of residual flow were highly associated with the angiographic flow index in a linear fashion: severity index (p = 0.0006), area (p = 0.003), and nadir (minimum/maximum counts; p = 0.004). This association was independent of the laboratory where the data were acquired. CONCLUSIONS: Despite different laboratories and camera systems, radionuclide measures of residual flow were highly associated with the angiographic flow index before reperfusion therapy. These results suggest that these measures are applicable on a broader scale for the noninvasive determination of collateral and antegrade flow in acute myocardial infarction.     

Difference between proximal and distal right coronary flow velocity pattern in humans

The choice of moral acts is governed by the unique ethnic and/or cultural meaning and values ascribed to by the individual. In pursuing an "acceptable" moral choice, the process of analysis is further directed by the ethical theories which are molded by time and tempered by the current context to which the action is undertaken. An OPTIMIN MODEL OF ETHICAL-DECISION MAKING PARADIGM is proposed, and health care policy on cultural diversity is adduced.     

Determination of cardiac troponin I forms in the blood of patients with acute myocardial infarction and patients receiving crystalloid or cold blood cardioplegia

To determine the forms of cardiac troponin I (cTnI) circulating in the bloodstream of patients with acute myocardial infarction (AMI) and patients receiving a cardioplegia during heart surgery, we developed three immunoenzymatic sandwich assays. The first assay involves the combination of two monoclonal antibodies (mAbs) specific for human cTnI. The second assay involves the combination of a mAb specific for troponin C (TnC) and an anti-cTnI mAb. The third assay was a combination of a mAb specific for human cardiac troponin T (cTnT) and an anti-cTnI mAb. Fifteen serum samples from patients with AMI, 10 serum samples from patients receiving crystalloid cardioplegia during heart surgery, and 10 serum samples from patients receiving cold blood cardioplegia during heart surgery were assayed by the three two-site immunoassays. We confirmed that cTnI circulates not only in free form but also complexed with the other troponin components (TnC and cTnT). We showed that the predominant form in blood is the cTnI-TnC binary complex (IC). Free cTnI, the cTnI-cTnT binary complex, and the cTnT-cTnI-TnC ternary complex were seldom present, and when present, were in small quantities compared with the binary complex IC. Similar results were obtained in both patient populations studied. These observations are essential for the development of new immunoassays with improved clinical sensitivity and for the selection of an appropriate cTnI primary calibrator.     

Withholding thrombolysis in patients with diabetes mellitus and acute myocardial infarction

The benefits of thrombolytic therapy in a patient with diabetes having a myocardial infarction are now well accepted but this treatment may be withheld inappropriately because of concerns about retinal haemorrhage. We therefore examined whether junior doctors alter their use of thrombolysis for the treatment of acute myocardial infarctions according to the type of diabetic retinopathy present. A questionnaire asking whether thrombolysis would be given to a 50-year-old male smoker with insulin-treated diabetes and an acute anterior MI was shown, with four unlabelled retinal photographs, to all doctors prescribing thrombolytic therapy in a south London teaching hospital and an affiliated district general hospital. In all, 24 medical SHOs, 16 medical registrars/specialist registrars, 3 medical senior registrars, and 23 casualty SHOs were interviewed. Of these 89% would thrombolyse such a patient with normal fundi, 55% with background diabetic retinopathy, 54 % if this also involved the macula, and 26% if they saw proliferative retinopathy. The more senior grades were more aggressive in their approach. As we believe that all patients with an acute anterior myocardial infarction and diabetes should be considered for thrombolysis irrespective of their retinal appearance these results suggest thrombolytic therapy is being withheld inappropriately.     

In-hospital and follow-up mortality of patients with acute myocardial infarction

Patients with definite acute MI who were admitted to Songkla University Hospital between 1982 and 1990 were studied. The 195 patients and 202 admissions were nearly equally distributed between these 65 and older versus those younger than 65. Three quarters were males. The in-hospital mortality was 19.5 per cent and 76.3 per cent of the deaths were from heart failure. Neither age nor gender determined the mortality once corrected for the Killip's staging. There was no difference in mortality when comparing Q versus non-Q MI, anterior versus inferior wall MI or males versus females. One hundred and thirty-eight patients could be followed for and average of 27.1 months. First year mortality was 11 per cent and the first 2 years was 14 per cent. The in-hospital mortality, representing the prethrombolytic era, appeared to be similar to values reported from the Thai and Western literature. The predominance of death from heart failure rather than from arrhythmia may be a consequence of delayed admission whence arrhythmic death had already occurred or patients will seek hospital advice only if highly symptomatic.     

Regional myocardial blood flow during hyperemia induced by contrast agent in patients with coronary artery disease

Regional myocardial specific blood flow (regional specific flow) was measured at rest and during contrast hyperemia after the intracoronary injection of xenon-133. The changes in regional specific flow were transient, resulting in some compromise in one of the underlying restraints of the inert gas washout method, namely, the presence of a steady state. Therefore, to determine the clinical utility of this technique, regional specific flow values obtained with this method were correlated with the presence and severity of coronary artery disease as assessed from the coronary arteriogram and left ventriculogram. Regional specific flow during contrast hyperemia was 186+/- 11 (mean +/- 1 standard error of the mean) ml/min per 100 g in control patients and 115+/-5 in patients with coronary artery disease. There was an inverse relation between regional specific flow during contrast hyperemia and the percent coronary stenosis when the stenosis was 40 percent or greater (r = 0.70, P less than 0.001). Regional specific flow was significantly less in patients with asynergy (77 +/- 10 ml/min per 100 g) than in patients with normal ventricular function (105 +/- 5) distal to coronary stenoses of greater than 75 percent. Thus regional specific flow measured during contrast hyperemia using the xenon washout technique and the Anger camera differentiated patients with normal coronary arteriograms from those with coronary artery disease. With this technique, good correlation was shown between regional specific flow and the percent coronary stenosis and presence of ventricular wall abnormalities. The information obtained with this method may provide prognostic information concerning suitability for surgical intervention.     

Effects of respiratory alkalosis and acidosis on myocardial blood flow and metabolism in patients with coronary artery disease

BACKGROUND: Variation of the arterial carbon dioxide partial pressure (PaCO2) is not uncommon in anesthetic practice. However, little is known about the myocardial consequences of respiratory alkalosis and acidosis, particularly in patients with coronary artery disease. The aim of the current study was to investigate the effects of variation in PaCO2 on myocardial blood flow (MBF), metabolism, and systemic hemodynamics in patients before elective coronary artery bypass graft surgery. METHODS: In 10 male anesthetized patients, measurements of MBF, myocardial contractility, metabolism, and systemic hemodynamics were made in a randomized sequence at PaCO2 levels of 30, 40, and 50 mmHg, respectively. The MBF was measured using the Kety-Schmidt technique with argon as a tracer. End-diastolic left ventricular pressure and the maximal increase of left ventricular pressure were assessed using a manometer-tipped catheter. RESULTS: The cardiac index significantly changed with varying PaCO2 levels (hypocapnia, - 9%; hypercapnia, 13%). This reaction was associated with inverse changes in systemic vascular resistance index levels. The MBF significantly increased by 15% during hypercapnia, whereas no change was found during hypocapnia. Myocardial oxygen and glucose uptake and the maximal increase of left ventricular pressure were not affected by varying PaCO2 levels. CONCLUSIONS: In anesthetized patients with coronary artery disease, short-term variations in PaCO2 have significant effects on MBF but do not influence global myocardial oxygen and glucose uptake. Changes in systemic hemodynamics associated with respiratory alkalosis and acidosis are caused by changes in systemic vascular resistance rather than by alterations in myocardial contractility.     

Cerebral blood flow velocity in acute schizophrenic patients. A transcranial Doppler ultrasonography study

Arg-Gly-Asp (RGD) motif mediates cell adhesion as a major determinant in interactions of disintegrins with cell surface receptors. In order to obtain a mutant trypsin with both high affinity to integrins and retained proteolytic activity, RGDS and RGD were inserted into a rigid turn region and a flexible loop of trypsin, respectively. Wild type trypsin and substituted mutant trypsins, 37RGDS and 77RGD, were expressed in E. coli and purified. Kinetic properties, autolytic stability as well as platelet aggregation inhibitory activity of both 37RGDS and 77RGD were determined. 37RGDS and 77RGD give retained proteolytic activities of 34% and 87%, respectively, and both become less stable to autolysis. 37RGDS shows an obvious inhibition rate of 29% for platelet aggregation and 77RGD gives a rather weak rate of 14% at the same protein concentration of 3.5 microM, while the wild type trypsin shows no inhibitory activity.     

Regional blood flow, contractility and metabolism in early myocardial infarction

The effects of occlusion of the left anterior descending coronary artery on a variety of metabolic parameters was examined in both infarcted and noninfarcted areas of the dog heart. These included mitochondrial performance, glycolysis, in vitro contractility, and regional myocardial blood flow. Measurements were made at 1 and 3 h after onset of ischemia. Regional coronary blood flow was measured in infarcted, noninfarcted and borderline regions using radioactive microspheres. Blood flow through the ischemic area was reduced by an average of 69% after 1 h of ischemia, and 75% after 3 h. After 3 h the subendocardium of the borderline region also revealed a significantly reduced blood flow. Mitochondria isolated from the ischemic region of the heart exhibited a substantial decrease in the rate of respiration (QO2), and minor reductions in the coupling between oxidative phosphorylation and electron transport (RCI), and in the amount of ADP phosphorylated per oxygen reduced (ADP:O ratio). Levels of hexose monophosphates were elevated 1 and 3 h after ischemia was initiated. At the same time, the concentration of fructose-1,6-diphosphate declined markedly, reflecting inhibition of glycolysis at the phosphofructokinase level. Concentrations of the adenosine phosphate moieties, as well as creatine phosphate, were reduced, while levels of free fatty acids were elevated in ischemic tissue. The in vitro contractility of glycerinated ischemic muscle fibers was also depressed. Significant changes were found in maximal tension development (P0), maximal rate of tension development (dp/dtmax), time to peak tension (t0), and shortening velocity at zero load (Vmax).     

Pathology of acute myocardial infarction with particular reference to occlusive coronary thrombi

Analysis of the pathological findings in 500 cases of fatal acute myocardial infarction showed that in 469 this was localized to one transmural area of the left ventricle; in 31 there was diffuse subendocardial necrosis. In the former occlusive coronary thrombus was found in the related artery in 95 per cent of cases. Variation in the percentage of occlusions found was noted between different prosectors and when coronary artery calcification was present. Only 4 of the 31 patients with subendocardial necrosis had recent occlusion; triple vessel disease was common in this group suggesting general failure of coronary perfusion. It is essential in necropsy studies of the relation of coronary thrombosis to myocardial infarction to be sure that muscle necrosis is present, to distinguish the two forms of myocardial necrosis, and to employ a meticulous dissection technique with decalcification of the arteries when necessary.