Myocardial infarct extension: incidence and relationship to survival

Recurrent ischemia after thrombolysis: importance of associated clinical findings. GUSTO-I Investigators. Global Utilization of Streptokinase and t-PA [tissue-plasminogen activator] for Occluded Coronary Arteries

OBJECTIVES

We sought to assess the incidence and clinical relevance of examination data to recurrent ischemia within an international randomized trial.

BACKGROUND

Ischemic symptoms commonly recur after thrombolysis for acute myocardial infarction.

METHODS

Patients (n = 40,848) were prospectively evaluated for recurrent angina and transient electrocardiographic (ECG) or hemodynamic changes. Five groups were developed: Group 1, patients with no signs or symptoms of recurrent ischemia; Group 2, patients with angina only; Group 3, patients with angina and ST segment changes; Group 4, patients with angina and hemodynamic abnormalities; and Group 5, patients with angina, ST segment changes and hemodynamic abnormalities. Baseline clinical and outcome variables were compared among the five groups.

RESULTS

Group 1 comprised 32,717 patients, and Groups 2 to 5 comprised 20% of patients (4,488 in Group 2; 3,021 in Group 3; 337 in Group 4; and 285 in Group 5). Patients with recurrent ischemia were more often female, had more cardiovascular risk factors and less often received intravenous heparin. Significantly more extensive and more severe coronary disease, antianginal treatment, angioplasty and coronary bypass surgery were observed as a function of ischemic severity. The 30-day reinfarction rate was 1.6% in Group 1, 6.5% in Group 2, 21.7% in Group 3, 13.1% in Group 4 and 36.5% in Group 5 (p < 0.0001); in contrast, the 30-day mortality rate was significantly lower (p < 0.0001) in Groups 1, 2 and 3 (6.6%, 5.4% and 7.7%, respectively) than in Groups 4 and 5 (21.8% and 29.1%).

CONCLUSIONS

Postinfarction angina greatly increases the risk of reinfarction, especially when accompanied by transient ECG changes. However, mortality is markedly increased only in the presence of concomitant hemodynamic abnormalities.

The value and promise of echocardiography in acute myocardial infarction and coronary artery disease

Two-dimensional and Doppler echocardiography have become extremely useful in the management of patients with acute myocardial infarction (AMI). Echocardiography is noninvasive, relatively inexpensive, and has no known biohazards. It offers unequaled information about cardiac anatomy and function. In the acute setting it is useful in the diagnosis of AMI and its complications. It is an excellent tool for monitoring therapy. Echocardiography has been shown to be useful in risk stratification upon presentation to the emergency ward and prior to hospital discharge. Stress echocardiography has broadened and sharpened the diagnostic and prognostic information. Contrast echocardiography has promise for demonstrating coronary artery flow. Research in ultrasonic myocardial tissue characterization shows potential for differentiating ischemic myocardium from infarcted myocardium. Thus, echocardiography is likely to become increasingly important in the future management of patients with AMI.

Clinical and angiographic features and prognostic significance of early postinfarction angina with and without electrocardiographic signs of transient ischemia

PURPOSE

The goal of the study was to characterize the clinical and angiographic characteristics and the prognostic significance of early postinfarction angina associated or unassociated with ST-T changes.

PATIENTS AND METHODS

Four hundred forty-nine consecutive patients surviving an acute myocardial infarction and catheterized before hospital discharge were included. They were closely monitored in the coronary care unit and a 12-lead electrocardiogram (ECG) was promptly obtained before the administration of nitroglycerin whenever chest pain suggestive of ischemia occurred. Complete follow-up information was obtained for all patients a mean of 14 +/- 8 months after the qualifying infarction.

RESULTS

Early postinfarction angina occurred in 164 patients. Transient ST-T changes were documented during pain in 79 patients and were absent in 85. Compared with patients without postinfarction angina, patients with angina without ST-T changes were older and had a more frequent past history of angina (42% versus 28%, p = 0.01). They also more often had a non-Q-wave myocardial infarction with lower peak creatine kinase blood level elevation. At angiography, patients with angina had more extensive coronary artery disease (1.9 +/- 0.8 diseased vessels per patient versus 1.6 +/- 0.8, p less than 0.05) and more left ventricular segments at jeopardy by a significant coronary artery stenosis (1.5 +/- 1.1 versus 1.2 +/- 1.1, p less than 0.05). The presence of ST-T changes during chest pain was associated with a further increase in the severity of coronary artery disease (2.1 +/- 0.8 diseased vessels per patient, p less than 0.05) and with a less well-developed collateral circulation (18% versus 34% of patients, p = 0.01) that was more often compromised by a coronary artery stenosis (22% versus 8% of patients, p = 0.008). In-hospital infarct extension occurred in 2% of patients without angina, 3.5% of patients with angina without ECG changes, and 28% of patients with angina and ST-T changes (p less than 0.01). The 2-year survival was similar in the first two groups (90% and 96%), and poorer (83%, p = 0.02) in patients with ST-T changes. Survival rates without myocardial infarction were respectively 80%, 78%, and 67% (p less than 0.004).

CONCLUSION

A gradient in the severity of coronary artery disease and in the extent of myocardium at jeopardy exists from patients with no postinfarction angina to patients with angina and to patients with angina accompanied by ECG signs of ischemia. The presence of ST-T changes during pain indicates a much less favorable clinical outcome.

Relation between anterograde blood flow through a coronary artery and the size of the perfusion bed it supplies: experimental and clinical implications

The relation between anterograde blood flow through a coronary artery and the size of the perfusion bed it supplies is not known. Accordingly, the left circumflex coronary artery was cannulated and perfused with arterial blood in 12 open chest mongrel dogs. In Group I dogs (n = 7), the goal was to correlate the size of the perfusion bed with the magnitude of anterogradely derived myocardial blood flow. The size of the perfusion bed was measured with use of two-dimensional myocardial contrast echocardiography, whereas anterograde myocardial blood flow was determined by injecting radiolabeled microspheres directly into the artery. In Group II dogs (n = 5), the goal was to study the effects of altering coronary blood flow on both anterogradely and collateral vessel-derived myocardial flow within the perfusion bed. In these dogs, microspheres were injected directly into both the coronary artery and the left atrium at each flow rate. In Group I dogs, the left circumflex perfusion bed size, as defined by myocardial contrast echocardiography, decreased at lower anterograde myocardial blood flow rates. The change in perfusion bed size occurred at the lateral zones. There was a linear relation between the normalized perfusion bed size and the normalized anterograde myocardial blood flow: y = 0.45x + 54.2 (p less than 0.001, r2 = 0.77). These results were substantiated in Group II dogs, in which the size of the perfusion bed was approximated with use of radiolabeled microspheres. The size of the perfusion bed was most affected when anterograde myocardial blood flow decreased to less than approximately 33% of normal. At the lowest flow rates, there was a linear relation between anterograde blood flow versus the fraction of the left circumflex flow derived anterogradely: y = 2.41x + 0.22 (p less than 0.001, r2 = 0.90). The lower the level of anterograde flow, the greater was the blood flow derived from remote vessels. It is concluded that the size of the area perfused by a coronary artery is significantly influenced by the magnitude of anterograde blood flow through that artery. These findings may have important implications in experimental and clinical models of myocardial ischemia.

The spectrum of death after myocardial infarction: a necropsy study

To determine the relative frequency of the causes of death in the acute (less than 24 hours), early (24 hours to 3 weeks), and chronic (greater than 3 weeks) phases of myocardial infarction, data from all autopsies performed at a university hospital during a 56-month period were reviewed. Autopsies were performed in 56% of in-hospital deaths and 27% of patients dead on arrival in the emergency room (out-of-hospital deaths). In 271 cases of suspected cardiac death, a myocardial infarction of any age was identified. Death had occurred in the acute phase of a first infarction in 19 patients and was most frequently due to pump failure (37%) followed by cardiac rupture (26%) and arrhythmias (21%). Death had occurred 24 hours to 3 weeks after a first infarction in 80 patients and was most frequently due to pump failure (44%), rupture (27%), and arrhythmias (16%). Recurrent acute infarction was found in 32% of patients whose deaths were due to arrhythmias or pump failure and in 19% of those whose deaths were due to rupture. Death had occurred greater than 3 weeks after a first infarction in 172 patients. In 132 (77%) of these patients death was due to a complication of a new acute or recent infarction. Myocardial rupture was a less frequent cause of death in patients with recurrent infarction (8%) than in those dying in the acute or early phase after their first infarction (27%, p = 0.0009). A primary arrhythmia in the absence of recurrent infarction or ischemia accounted for only 14% of out-of-hospital deaths late after an infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Results of percutaneous transluminal coronary angioplasty for angina pectoris early after acute myocardial infarction

Between May 1980 and July 1985, 70 patients underwent percutaneous transluminal coronary angioplasty (PTCA) for angina occurring 24 hours after and within 30 days of acute myocardial infarction (32 with Q-wave infarction and 38 with non-Q-wave infarction). One-vessel disease was present in 42 (60%) and multivessel in 28 (40%); the mean ejection fraction was 0.56 (greater than or equal to 0.50 in 77% of patients). PTCA was successful in 56 patients (80%) and after introduction of steerable dilating systems in February 1983 this rate became 86%. The success rate for complete occlusions was 76%. The interval from myocardial infarction to PTCA was similar in patients with successful dilation (12.7 +/- 8.1 days) and those without (13.4 +/- 8.0 days). PTCA failed in 14 patients (20%); 8 underwent emergency coronary artery bypass for acute occlusion and 4 of 6 patients whose lesions could not be crossed had elective bypass surgery. There was 1 operative death. No patient sustained a Q-wave infarction. Three patients had non-Q-wave infarctions after technically successful PTCAs. Mean follow-up was 27 months (6 to 67 months). Of the 56 patients successfully dilated, 14 (25%) had 15 cardiac events during follow-up: death (1), non-Q-wave infarction (2), repeat PTCA (7), coronary bypass (4) and recurrence of severe angina (1). The cumulative mortality was 3% and the reinfarction rate was 7% (no Q-wave reinfarctions). Forty-two (60%) of the 70 patients were free of complicating events acutely and during follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Postinfarction angina

In conclusion, the PIA patient is at high risk, with higher early as well as late mortality. The pathophysiology of PIA is complex and may vary from patient to patient. The concepts of ischemia at a distance and ischemia in the infarct zone have led to a better understanding of early PIA. Coronary spasm may play an important role in most PIA patients as in the general population of patients with angina pectoris. Medical therapy is efficacious in many, although it may on rare occasion aggravate myocardial ischemia. Urgent coronary arteriography is generally safe and should be performed as soon as possible for medically refractory PIA. CABG appears to be safe in experienced hands, but its timing must be individualized. The IABP should be reserved for more unstable patients for fear of vascular complications. Randomized controlled trials such as the BARI Trial will further compare PTCA with CABG.

Myocardial infarct extension. Identification of subgroups by the pattern of the serum CKMB level

To examine the clinical course of patients with acute myocardial infarction complicated by "extension", we studied prospectively 141 patients who had been diagnosed as having acute myocardial infarction. The serum CKMB level of these patients was determined at 8-h intervals during the first 5 days following admission. The patients were classified into 3 groups. Group A (early extension): patients who showed CKMB re-elevation before the CKMB values reached normal levels (28%). Group B (late extension): patients who showed CKMB re-elevation after the normalization of serum CKMB levels (21%). Group C (control group): patients without CKMB re-elevation (51%). Patients in group A showed the most unfavourable clinical course with a greater rate of haemodynamic deterioration compared with patients in the B or C groups, and a higher rate of recurrent ischemic pain. We found no significant differences in these parameters between the B and C groups. We were unable to find any risk factor associated with the development of extension. The pattern of the serum CKMB curve may allow a separation of two different subgroups of patients with acute myocardial infarct extension: patients with early extension, who show a high prevalence of haemodynamic deterioration, and patients with late extension, characterized by small infarcts and a benign clinical course.

CPK and CPK-MB in the early diagnosis of acute myocardial infarction and prediction of infarcted area

This study was carried out on patients of a coronary unit to evaluate the diagnostic efficiency of total CPK and CPK-MB by using different analytical techniques: catalytic, immunoassisted, cellulose acetate electrophoresis, radioimmunoassay and immunoradiometric assay. The behaviour of the enzyme was studied in all patients with reference to the localization and extent of the infarct. In all cases a diagnostic algorithm was followed based on the combined use of CPK and its MB isoenzyme; the activity was measured twice, at three-hour intervals after admission. In this way the utilization of total CPK and MB isoenzyme allows almost complete diagnostic efficiency within the first 9 hours from onset of chest pain, together with the possibility of calculating the slope of the curve of MB isoenzyme release useful for calculating infarct size. Maximum diagnostic efficiency is also obtained in cases of small infarcts, with silent ECG, and those difficult to classify clinically.

Mechanisms contributing to precipitation of unstable angina and acute myocardial infarction: implications regarding therapy

Clinical and autopsy studies indicate that most patients who present with unstable angina or an acute myocardial infarction (AMI) have significant underlying coronary atherosclerosis. This review discusses 4 mechanisms that may contribute to the precipitation of these acute ischemic clinical syndromes: progression of atherosclerosis, acute coronary thrombosis, coronary artery spasm, and platelet aggregation. Numerous clinical trials using thrombolytic agents early during AMI have shown the incidence of thrombosis to be at least 60%. Other studies suggest that platelet aggregation frequently contributes to the evolution of AMI from unstable angina and that spasm may occasionally play a similar role. The therapeutic implications of these mechanisms are also considered in light of their potential to restore coronary artery blood flow (vs conventional methods thought mainly to reduce myocardial oxygen demand) and thereby limit the infarct process. The role of vasodilators, thrombolytic agents, antiplatelet drugs and beta-adrenergic blocking drugs are discussed. Finally, therapeutic guidelines for the treatment of acutely ill patients are constructed that emphasize the need for a comprehensive yet time-efficient treatment strategy that uses nitrates, calcium channel-blocking drugs, streptokinase, heparin, aspirin and, in selected patients in an unstable condition, emergency percutaneous transluminal coronary angioplasty and coronary artery bypass grafting.

Clinical characteristics and prognosis of patients with postinfarction angina caused by coronary artery spasm

Clinical features and the course of 15 patients with postinfarction angina caused by coronary artery spasm are described. Episodes of postinfarction angina in the patients recurred at rest in the early recovery phase and were accompanied by transient ST-segment elevation. The area where ST-segment elevations were demonstrated on a 12-lead ECG always included the leads with newly developed abnormal Q waves. Pain resolved spontaneously or after sublingual nitroglycerin in several minutes. Holter ECGs during a 24-h period demonstrated frequent episodes of ST-segment elevation that were not always associated with chest pain. Treatment with calcium antagonist and/or nitrates effectively suppressed angina, and only one patient developed reinfarction. The patient's subjective symptoms were abolished by diltiazem and isosorbide dinitrate. A Holter ECG of the patient revealed silent ST-segment elevations before and after the reinfarction and an increase of the drugs completely suppressed the recurrence of silent ischemic ECG changes. Coronary arteriograms were obtained from 8 patients, which demonstrated more than 75% segmental stenosis on one coronary artery in 5 patients and no significant obstruction in the remaining 3. All patients performed a treadmill exercise stress test before discharge and most demonstrated excellent tolerance. All patients experienced no form of chest pain for an average of 25 months follow-up under medication. We conclude that among patients with postinfarction angina, those cases caused by coronary artery spasm have a relatively good prognosis.

Early recognition of the patient at late high risk: incomplete infarction and vulnerable myocardium

The process of identifying patients with myocardial infarction (MI) at high risk after hospital discharge should begin at admission. By using basic clinical and laboratory information, enhanced by a wide variety of noninvasive tests, not only can individual patients at risk be recognized, but also the processes that determine risk can, at least in part, be appreciated. Outcome is affected by the extent of damaged tissue and, apparently, by the amount of potentially ischemic muscle. MI may change the coronary circulation such that a new and fragile balance between supply and demand results, both within and outside the infarct zone; that is, the infarct may be incomplete and the viable muscle within it may then be vulnerable to later ischemia. Muscle outside the infarct zone may be left in much the same precarious state. Also, coronary spasm may not be infrequent in the weeks after MI. These factors together may underlie recurrent post-MI myocardial ischemia.

The high risk patient after recovery from myocardial infarction: recognition and management

Patients at high risk for recurrent myocardial infarction or death can be identified after recovery from an acute myocardial infarction. Predictors of high risk at the time of initial hospital discharge may vary in different localities depending on the underlying baseline characteristics of the patient cohort. The medical records were analyzed of 139 patients discharged from San Francisco General Hospital after recovery from an acute myocardial infarction between July 1978 and September 1981. Multivariate stepwise discriminant analysis of 20 variables contributing to sudden and total death identified complex ventricular ectopic rhythm as the most important variable, followed by age. Failure to receive chronic long-acting nitrates was an independent variable contributing to total mortality but not to sudden death, while the presence of an initial anterior myocardial infarction and impaired left ventricular function were independent variables contributing to sudden death but not to total mortality. Routine 24 hour ambulatory monitoring, radionuclide ventriculography and submaximal stress tests performed during the second week after recovery from an acute myocardial infarction provide identification of a high risk cohort for subsequent recurrent myocardial infarction or death and permit appropriate interventions designed to lessen risk to be undertaken.