Comparison of coronary angiographic findings during the first six hours of non-Q-wave and Q-wave myocardial infarction

Usefulness of peak systolic strain measurement by automated function imaging in the prediction of coronary perfusion in patients with acute myocardial infarction

BACKGROUND/AIMS

The usefulness of global longitudinal peak systolic strain (GLPSS) measurement by automated function imaging (AFI) in the prediction of perfusion status of infarct-related artery (IRA) before percutaneous coronary intervention (PCI) was evaluated.

METHODS

Sixty-nine patients with acute myocardial infarction (AMI) who underwent successful primary PCI were divided into two groups; the patients with occlusion of IRA (Group I, 41 patients, 63.0 ± 14.9 years of age, 31 males) versus the patients with patent IRA (Group II, 28 patients, 63.8 ± 11.2 years of age, 15 males). GLPSS by AFI and wall-motion score index (WMSI) were analyzed in both groups.

RESULTS

GLPSS was significantly decreased in Group I compared with Group II (-11.2 ± 3.7 vs. -14.1 ± 4.7%, p = 0.005), but WMSI (1.49 ± 0.28 vs. 1.35 ± 0.32, p = 0.062) did not differ between groups. GLPSS of infarct segments was significantly lower (-3.7 ± 5.4 vs. -11.4 ± 4.8%, p < 0.001), and WMSI of infarct segments was significantly higher (2.13 ± 0.57 vs. 1.66 ± 0.57, p = 0.001) in Group I compared with Group II. By receiver operation curve analysis, the area under the curve to predict IRA occlusion was 0.850 in GLPSS of infarct segments and 0.719 in WMSI of infarct segments. The optimal cut-off value to predict IRA occlusion was -9.4% in GLPSS of infarct segments (sensitivity, 85.4%; specificity, 67.9%) and 1.68 in WMSI of infarct segments (sensitivity, 78.0%; specificity, 60.7%).

CONCLUSIONS

The present study suggested that GLPSS measured by AFI is a more sensitive predictor of IRA occlusion than is WMSI before PCI. Routine measurement of GLPSS by AFI can be a very useful tool in risk stratification of AMI.

Impact of delayed presentation on management and outcome of non-ST-elevation acute coronary syndromes

BACKGROUND

The impact of delayed presentation on the management and outcomes of patients with non-ST-elevation acute coronary syndromes (NSTE-ACS) has not been well studied. Furthermore, the prognostic value of initial biomarker level in relation to the time of presentation has not been determined.

METHODS

The Canadian ACS II registry was a national, multicenter, prospective observational study of 1,956 patients with NSTE-ACS (October 2002-December 2003). We compared the baseline characteristics, treatment, and outcomes in early (within 6 hours of symptom onset) versus late presenters (>6 hours). A logistic regression model was developed to examine the independent association of late presentation with 1-year mortality. We also evaluated the prognostic value of initial biomarker level in relation to early versus late presentation.

RESULTS

A total of 1,219 (62.3%) patients presented early, whereas 727 (37.7%) presented late; their rates of in-hospital revascularization were similar (40.5% vs 42.5%, respectively, P = .39). There was also no significant difference in hospital mortality (1.6% vs 2.2%, P = .30) or 1-year mortality (7.6% vs 5.7%, P = .13) between early and late presenters. After adjusting for other prognosticators, late presentation was not an independent predictor of 1-year mortality (adjusted odds ratio 0.78, 95% confidence interval 0.48-1.26, P = .3). Elevated initial biomarker was independently associated with higher 1-year mortality (adjusted odds ratio 2.17, 95% CI 1.31-3.58, P = .002) regardless of whether hospital presentation was early or late (P for interaction = .74).

CONCLUSIONS

There is still considerable delay between symptom onset of NSTE-ACS and hospital presentation in the contemporary era. In contrast to studies of ST-elevation myocardial infarction, we found no significant differences in the management and outcome of early presenters as compared with late presenters with NSTE-ACS. Nevertheless, measures to reduce patient delay time should continue to be implemented. Initial biomarker status is a useful prognosticator irrespective of the delay time.

Myocardial salvage in patients with non-ST-elevation myocardial infarction determined by myocardial perfusion imaging

We compared acute and late myocardial perfusion imaging using technetium-99m isotopes in 69 patients who had non-ST-elevation myocardial infarction. Among these patients, we found that the ischemic risk area was often large (19% of the left ventricle), and that 67% had significant myocardial salvage, defined as a >25% decrease in risk area, which was associated with an improved ejection fraction.

Platelet collagen receptor GPIa (C807T/HPA-5) haplotype is not associated with an increased risk of fatal coronary events in middle-aged men

Platelet GPIa/IIa receptors play key roles in the adhesion of platelets to collagen during the formation of coronary thrombosis. The C807T and HPA-5 polymorphisms of the gene for GPIa define three distinct alleles of GPIa which are associated with the surface expression of the protein in an allele-dependent fashion. Significance of these polymorphisms in victims of sudden cardiac death (SCD) was studied in Helsinki Sudden Death Study (HSDS) comprising 700 autopsied middle-aged Caucasian Finnish men with 288 SCD victims and 84 men with fatal acute myocardial infarction (AMI). The high-expression A1 allele was found in 36.6% of control men as opposed to 38.0% of all SCD victims and 36.9% of men with fatal AMI (P>0.4). The high-expression A1A1 genotype was found in 11.9% of men with fatal AMI and 10.0% of controls as opposed to the low-expression A2A2 genotype which was found in 29.8% of men with fatal AMI and in 31.2% of controls (OR 1.2, P>0.3). Age group (under/over 55) had no effect on the results. Our results do not support an effect of the GPIa haplotype on fatal coronary events among middle-aged men.

Unstable Angina and Non-ST-Segment Elevation Myocardial Infarction

In the last 20 years there have been enormous advances in our understanding of the acute coronary syndromes and how to manage patients presenting with them. In the 1980s, we began to understand the importance of thrombus formation was in the pathophysiology of acute coronary syndromes. Randomized studies also showed that appropriate antithrombotic therapy reduced the subsequent occurrence of myocardial infarction and death. In the 1990s, other therapeutic modalities and particularly percutaneous coronary intervention have come to the forefront as effective therapy in these syndromes. The glycoprotein IIb/IIIa receptor antagonists along with coronary stent implantation have proved extremely beneficial in short- and long-term management. We also have learned the importance of risk-factor modification in preventing subsequent events. In the future, greater efforts will focus on primary prevention.

[Terminology and diagnostic criteria for non-Q wave myocardial infarct]

INTRODUCTION

Non-Q myocardial infarction represents a specific entity of infarction. Many studies have shown that non-Q myocardial infarction differs from Q myocardial infarction not only electrocardiographically, but also from pathophysiological, histological, clinical and prognostic points of view. NON-Q MYOCARDIAL INFARCTION-TERMINOLOGY: Until 1980's, anatomical terminology depending on ECG changes was used in the literature. Subendocardial infarction referred to non-Q myocardial infarction, while transmural infarction referred to Q myocardial infarction. Since it was established that presence or absence of Q waves is a non-specific marker of transmural necrosis, in 1982 Spodick proposed the use of terms based on ECG findings. DIAGNOSTIC CRITERIA FOR NON-Q MYOCARDIAL INFARCTION: Elevation of markers of myocardial damage (CK, CK-MB, Troponin) is the most significant criterion for diagnosis of non-Q myocardial infarction. It cannot be made without this criterion because non-Q myocardial infarction may have ECG changes identical to those in unstable angina. Authors do not agree which type of initial ECG changes is the most frequent (ST elevation, ST depression or inverted T waves).

CONCLUSION

Non-Q myocardial infarction represents a specific entity of myocardial infarction. Anatomically, based on the extension of necrosis, non-Q myocardial infarction is subendocardial, but it can be transmural as well. ECG changes in non-Q myocardial infarction may be identical to those in unstable angina. Therefore, elevation of cardiac enzymes is the golden standard in diagnosis of non-Q myocardial infarction.

Pathophysiology of early coronary angioplasty with stenting on non-Q-wave vs Q-wave myocardial infarction

This study was undertaken to evaluate the pathophysiologic and clinical effects of the early application of percutaneous transluminal coronary angioplasty (PTCA) supported by stenting on non-Q-wave myocardial infarction (MI). Ninety-four patients with non-Q-wave MI and 316 patients with Q-wave MI were studied. Early PTCA with provisional stenting (40%) was performed in all of them. A history of MI (22% vs 12%, p=0.018), preinfarction angina < or = 24 hours before the onset of MI (60% vs 33%, p<0.001), and patent infarct-related vessels (83% vs 21%, p<0.001) were significantly more common in non-Q-wave MI than in Q-wave MI. As predictors of the occurrence of non-Q-wave MI, preinfarction angina (p=0.001) and previous MI (p=0.021) were significant variables. Clinical outcomes showed more improvement in in-hospital death (0.0% vs 5.0%, p=0.036) and long-term event-free curves for death and/or MI (p=0.035) in non-Q-wave MI than Q-wave MI when patients with previous MI were excluded. There was no significant difference in clinical outcome between the two groups when patients with previous MI were included. The high incidence of patent infarct-related vessels and preinfarction angina as well as the improved outcome obtained by early PTCA/stenting suggest instability of coronary occlusion and culprit coronary lesions in non-Q-wave MI. In conclusion, non-Q-wave MI constitutes a characteristic feature of MI induced by unstable coronary lesions, and early interventional therapies are presumed to result in improved outcomes by stabilizing the unstable culprit lesions.

Platelet glycoprotein Ibalpha HPA-2 Met/VNTR B haplotype as a genetic predictor of myocardial infarction and sudden cardiac death

BACKGROUND

Sudden cardiac death (SCD) is one of the leading manifestations of coronary heart disease in early middle age. Platelet glycoprotein (GP) Ib-IX-V receptor complexes play a key role in the initial adhesion of platelets to collagen during the formation of a coronary thrombus. The HPA-2 (Thr145 Met) and VNTR polymorphisms of the gene for GP Ibalpha have been studied previously in hospitalized patients with acute coronary syndromes. The significance of these polymorphisms in victims of sudden cardiac death is not known.

METHODS AND RESULTS

The association of these 2 polymorphisms with coronary atherosclerosis, coronary artery stenosis, coronary thrombosis, myocardial infarction (MI), and SCD was studied in the Helsinki Sudden Death Study, which comprised 2 large autopsy series, collected 10 years apart during 1981 to 1982 and 1991 to 1992, of 700 middle-aged white Finnish men who suffered sudden or violent out-of-hospital death. The 2 polymorphisms showed an almost complete linkage disequilibrium. Men with acute MI (n=80) and coronary thrombosis (n=65) were more likely to be carriers of the HPA-2 Met allele (OR 2.0 and 2.6, respectively, P<0.005 for both) than were control subjects who died of noncardiac causes (n=367). In men <55 years old, the Met allele was overrepresented (OR 2.2) among victims of SCD (n=98) compared with control subjects (n=249). In men <55 years old, 17 of 29 men with acute MI (58.6%) and 16 of 23 men with coronary thrombosis (69.6%) were carriers of the HPA-2 Met allele compared with the 49 of 249 (19.7%) who had died of noncardiac causes (ORs 5.6 and 9.2, respectively). Similar associations were observed in the separate analyses of both autopsy series.

CONCLUSIONS

Our results suggest that the HPA-2 Met/VNTR B haplotype of the platelet von Willebrand factor and thrombin receptor protein GP Ib-V-IX may be considered to be a major risk factor of coronary thrombosis, fatal MI, and SCD in early middle age.

Q-wave evolution of a first acute myocardial infarction without significant ST segment elevation

BACKGROUND

Some patients with acute myocardial infarction presenting without significant ST segment elevation develop a Q-wave infarction. It is unclear whether these patients can be identified from the admission electrocardiogram (ECG) and whether they differ in their in-hospital prognosis from those who retain a non-Q-wave myocardial infarction.

METHODS

In 432 consecutive patients admitted to our centre with a first acute myocardial infarction without Q waves and with ST segment amplitudes < or =0.1 mV on admission, we assessed the frequency, the electrocardiographic predictors and the short-term implications of a Q-wave evolution.

RESULTS

In 94 patients (22%), a Q-wave myocardial infarction evolved before hospital discharge (14 anterior, 26 inferior, six lateral, and 48 posterior). Minor anterior ST segment elevation was 36% sensitive and 95% specific in predicting anterior Q waves; minor inferior ST segment elevation, 42% and 89%, respectively, for inferior Q waves; and a maximal ST segment depression > or =0.2 mV in leads V2-V3 with upright T waves and without remote ST segment depression, 38% and 97%, respectively, for posterior R waves. Although patients with a Q-wave evolution had a greater creatinkinase MB peak than those retaining a non-Q-wave pattern (191+/-113 vs. 105+/-77 IU/l, respectively, P<0.001), they experienced a benign in-hospital course, with similar risk of severe complications after adjustment for the baseline clinical predictors than non-Q-wave patients.

CONCLUSIONS

About one fifth of patients with a first acute myocardial infarction without a significant ST segment elevation develop a Q-wave infarction and the admission ECG can help identify them. This evolution, however, is not associated with a worse in-hospital outcome.

Glycoprotein IIIa Pl(A1/A2) polymorphism and sudden cardiac death

OBJECTIVES

We studied the association of the Pl(A1/A2) polymorphism with coronary thrombosis, myocardial infarction (MI) and sudden cardiac death (SCD) in autopsied victims of sudden death.

BACKGROUND

Sudden cardiac death is one of the leading symptoms of coronary heart disease in early middle age. Platelet glycoprotein (GP)IIb/IIIa fibrinogen receptors play a key role in coronary thrombosis and MI. Pl(A1/A2) polymorphism of the gene for GPIIIa has been previously studied in hospital MI patients. Significance of the Pl(A1/A2) polymorphism in victims of SCD is not known.

METHODS

The Pl(A1/A2) polymorphism was studied in the Helsinki Sudden Death Study comprising 700 autopsied middle-aged white Finnish men (33 to 70 years, mean 53 years) who suffered sudden or violent out-of-hospital death.

RESULTS

Prevalence of the A2 allele decreased with age in the series. This decrease was observed among victims of SCD (n = 281) but not in men who died violently (n = 258) or of other diseases (n = 127). Of SCD victims below 50 years, 39.7% were carriers of the A2 allele compared with 28.3% among men under 50 who died of other causes (odds ratio [OR] 2.5, p = 0.01). Men with acute fatal coronary thrombosis (n = 39) were more often (OR 3.4, p < 0.01) carriers of the A2 allele than were men (n = 242) with SCD in the absence of acute coronary thrombosis (48.7% vs. 24.4%, respectively). In addition, men with MI and recent or old thrombosis (n = 67) were more often (OR 3.6, p = 0.005) carriers of the A2 allele than were men (n = 123) with MI in the absence of thrombosis (44.8% vs. 20.3%, respectively). These associations were especially strong in men under 60.

CONCLUSIONS

Our results suggest that the A2 allele of the Pl(A1/A2) polymorphism of GPIIIa is a major risk factor of coronary thrombosis and may be one important predictor of SCD in early middle age.

Cardiogenic shock with non-ST-segment elevation myocardial infarction: a report from the SHOCK Trial Registry. SHould we emergently revascularize Occluded coronaries for Cardiogenic shocK?

OBJECTIVES

We sought to determine the outcomes of patients with cardiogenic shock (CS) complicating non-ST-segment elevation acute myocardial infarction (MI).

BACKGROUND

Such patients represent a high-risk (ST-segment depression) or low-risk (normal or nonspecific electrocardiographic findings) group for whom optimal therapy, particularly in the setting of shock, is unknown.

METHODS

We assessed characteristics and outcomes of 881 patients with CS due to predominant left ventricular (LV) dysfunction in the SHOCK Trial Registry.

RESULTS

Patients with non-ST-segment elevation MI (n = 152) were significantly older and had significantly more prior MI, heart failure, azotemia, bypass surgery, and peripheral vascular disease than patients with ST-elevation MI (n = 729). On average, the groups had similar in-hospital LV ejection fractions (approximately 30%), but patients with non-ST-elevation MI had a lower highest creatine kinase and were more likely to have triple-vessel disease. Among patients selected for coronary angiography, the left circumflex artery was the culprit vessel in 34.6% of non-ST-elevation versus 13.4% of ST-elevation MI patients (p = 0.001). Despite having more recurrent ischemia (25.7% vs. 17.4%, p = 0.058), non-ST-elevation patients underwent angiography less often (52.6% vs. 64.1%, p = 0.010). The proportion undergoing revascularization was similar (36.8% for non-ST-elevation vs. 41.9% ST-elevation MI, p = 0.277). In-hospital mortality also was similar in the two groups (62.5% for non-ST-elevation vs. 60.4% ST-elevation MI). After adjustment, ST-segment elevation MI did not independently predict in-hospital mortality (odds ratio, 1.30; 95% confidence interval, 0.83 to 2.02; p = 0.252).

CONCLUSIONS

Patients with CS and non-ST-segment elevation MI have a higher-risk profile than shock patients with ST-segment elevation, but similar in-hospital mortality. More recurrent ischemia and less angiography represent opportunities for earlier intervention, and early reperfusion therapy for circumflex artery occlusion should be considered when non-ST-elevation MI causes CS.

No Prognostic Importance of Resistance to Activated Protein C in Unstable Coronary Artery Disease Despite Signs of Thrombin Activation

Resistance to activated protein C (APC resistance) is the single most important hemostatic defect associated with venous thromboembolic disease. However, little is. Known about this defect in arterial disease. The aim of this study was thus to investigate the frequency and prognostic importance of APC resistance and its influence on the coagulation system in one type of arterial thrombosis. In this study, 323 patients admitted to hospital because of unstable coronary artery disease, that is, unstable angina pectoris or non-Q-wave myocardial infarction, were investigated and compared with a reference group of apparently healthy individuals. The patients participated in a prospective, multicenter, randomized, and placebo-controlled investigation evaluating the protective value of low molecular weight heparin (dalteparin) in unstable coronary artery disease. The APC ratio was assayed using a modified activated partial thromboplastin time reaction method to measure the response to activated protein C. APC resistance was defined as an APC ratio </=2.2. Signs of thrombin activation were measured by prothrombin fragment 1+2 levels. The 7.2% (23/318) occurrence of APC resistance found in patients did not differ from the 5.8% (4/69) level in the reference population (P = 0.16). A significant elevation of the prothrombin fragment 1+2 median level of 2.5 nM (interquartile range, 1.9-3.2 nM) was found in the patients with APC resistance compared with 1.7 nM (interquartile range, 1.2-2.4nM) in the group with a normal APC ratio (P < 0.01). During the 150-day follow-up period, there was no increased risk of cardiac events in patients with APC resistance. Although accompanied by signs of increased thrombin formation, APC resistance doesnot seem to be an important risk factor for the development of instability in coronary artery disease.

Tachycardia-induced subendocardial necrosis in acutely instrumented dogs with fixed coronary stenosis

It has been speculated but never proven that tachycardia-induced ischemia per se may lead to myocardial infarction. In 17 anesthetized dogs, the proximal left anterior descending (LAD) artery was cannulated and perfused via bypass from the left subclavian artery. Distal LAD pressure was reduced by a screw clamp to cause > or =20% decrease in wall thickening during pacing tachycardia but no decrease in resting heart rate (approximately 90 bpm). Dogs were randomly assigned to three groups: 1) control (n = 6) maintained at resting heart rate (approximately 90 bpm) and mean coronary pressure of 49+/-5 mm Hg for 4 h; 2) 4-h ischemia (n = 6), paced at 150 bpm and mean coronary pressure maintained at 59+/-6 mm Hg for 4 h; and 3) 1-h ischemia (n = 5), paced at 150 bpm and mean coronary pressure of 54+/-8 mm Hg for 1 h. Myocardial blood flow and infarct area were measured by radiolabeled microspheres and triphenyl-tetrazolium chloride staining, respectively. Despite the higher coronary pressure in the 4-h ischemia group (P = 0.02), patchy subendocardial necrosis occurred in all these dogs and in two of the 1-h ischemia dogs, and one control dog had minimal papillary muscle necrosis. Infarct area was largest in the 4-h ischemic group (15.5%+/-9.1%) compared with control and 1-h ischemia groups (0.09%+/-0.2% and 1.6%+/-2.1%, respectively) (P < 0.002). Relative (risk/ nonrisk areas) subendocardial flow was lower at the end of ischemia in the 4- and 1-h ischemia groups compared with the control group (0.3+/-0.1 and 0.4+/-0.1 vs 0.9+/-0.2; P = 0.008 and 0.01, respectively). Prolonged tachycardia-induced ischemia, in the face of fixed coronary stenosis causing no ischemia at the resting heart rate, leads to patchy subendocardial necrosis, despite anticoagulation and antiplatelet treatment.

IMPLICATIONS

Prolonged tachycardia-induced ischemia, in the face of fixed coronary stenosis causing no ischemia at the resting heart rate, leads to subendocardial infarction in dogs. These findings suggest a possible mechanism for postoperative myocardial infarction.

Nuclear morphometry of the myocardial cells as a diagnostic tool in cases of sudden death due to coronary thrombosis

Sudden cardiac death due to underlying coronary artery thrombosis is one of the leading causes of death. However, in a significant percentage of individuals who died suddenly, no indication of myocardial infarction is found during post-mortem examination, especially when the time interval between appearance of symptoms and death is short. In the present study, we have evaluated certain nuclear morphometric parameters, such as, minimum, maximum, mean and standard deviation of perimeter and area in 20 individuals who died of coronary artery thrombosis, within 1 h from symptoms onset. Furthermore, the above parameters were compared with those of a control population of 20 individuals whose sudden death was caused by traffic accidents. Statistical elaboration of the results by means of t-test, Mann-Whitney (U-test) and analysis of covariance (adjusting for age), showed a statistically significant difference for all variables except for the minimum area. With stepwise discriminant analysis method, the mean perimeter was selected as the best predictor of cardiac death. Mean perimeter achieved a correct reclassification percentage (based on Fisher's linear discriminant function) of 92.5% (85% and 100% for cases and controls, respectively). Moreover, by applying the cut-off of 172 microns, we could identify the individuals who died suddenly because of coronary artery thrombosis with a specificity of 100% (sensitivity 85%, P < 0.001). Our results show that nuclear morphometry of the myocardial cells is a reliable diagnostic tool for the diagnosis of coronary thrombosis based lesion in cases of sudden death, even when methods trying to verify the presence of infarction fail to do so.

Non-Q-wave versus Q-wave myocardial infarction after thrombolytic therapy: angiographic and prognostic insights from the global utilization of streptokinase and tissue plasminogen activator for occluded coronary arteries-I angiographic substudy. GUSTO-I Angiographic Investigators

BACKGROUND

Although the stratification of patients with myocardial infarction into ECG subsets based on the presence or absence of new Q waves has important clinical and prognostic utility, systematic evaluation of the impact of thrombolytic therapy on the subsequent development and prognosis of non-Q-wave infarction has been limited to date.

METHODS AND RESULTS

We examined 12-lead ECG, coronary anatomy, left ventricular function, and mortality among 2046 patients with ST-segment elevation infarction from the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries angiographic subset to gain further insight into the pathophysiology and prognosis of Q- versus non-Q-wave infarction in the thrombolytic era. Non-Q-wave infarction developed in 409 patients (20%) after thrombolytic therapy. Compared with Q-wave patients, non-Q-wave patients were more likely to present with lesser ST-segment elevation in a nonanterior location. The infarct-related artery in non-Q-wave patients was more likely to be nonanterior (67% versus 58%, P=.012) and distally located (33% versus 39%, P=.021). Early (90-minute, 77% versus 65%, P=.001) and complete (54% versus 44%, P<.001) infarct-related artery patency was greater among the non-Q-wave group. Non-Q-wave patients had better global (ejection fraction, 66% versus 57%; P<.0001) and regional left ventricular function (10 versus 24 abnormal chords, P=.0001). In-hospital, 30-day, 1-year, and 2-year (6.3% versus 10.1%, P=.02) mortality rates were lower among non-Q-wave patients.

CONCLUSIONS

The excellent prognosis among the subgroup of patients who develop non-Q-wave infarction after thrombolysis is related to early, complete, and sustained infarct-related artery patency with resultant limitation of left ventricular infarction and dysfunction.

The continuing debate: conservative or interventional therapy for unstable coronary artery disease

A "look-and-act" approach, using a strategy of early intervention, and a "watchful waiting" approach, using medical therapy, are compared for the management of patients with unstable coronary artery disease (UCAD). Results from clinical trials are used to illustrate the advantages of antiplatelet and antithrombotic therapy and the problems associated with early intervention. Finally, a clinical management strategy for patients with UCAD is outlined. It is concluded that watchful waiting appears to be the most effective way of managing both patients and resources.

Late assessment of thrombolytic efficacy (LATE) study: prognosis in patients with non-Q wave myocardial infarction. (LATE Study Investigators)

OBJECTIVES

We examined the impact of thrombolytic therapy and the prognosis of patients with non-Q wave myocardial infarction in a randomized placebo-controlled trial known as the Late Assessment of Thrombolytic Efficacy (LATE) study.

BACKGROUND

Patients with non-Q wave as compared with Q wave myocardial infarction in the era before thrombolytic therapy were traditionally thought to have a higher rate of reinfarction and death between hospital discharge and 1 year such that the overall prognosis for outcome at 1 year was similar in the two groups.

METHODS

The study patients began treatment with either recombinant tissue-type plasminogen activator (rt-PA) or matching placebo, 6 to 24 h after the onset of chest pain. Post hoc analysis of mortality and reinfarction was carried out by comparing rt-PA and placebo in various subsets of patients based on the presenting electrocardiogram (ECG) and the evolution of the ECG with respect to the development of Q waves.

RESULTS

Among 5,711 participants, 4,759 had a confirmed myocardial infarction, including 1,309 classified as having a non-Q wave infarction at hospital discharge. Irrespective of treatment assignment, all patients with non-Q wave versus Q wave infarction had a lower 1-year mortality rate (13.3% vs. 17.1%, p = 0.001) and a similar 1-year reinfarction rate (8.6% vs. 7.9%, p = 0.7). Of the 4,759 patients with confirmed myocardial infarction, 2,973 presented with ST segment elevation or bundle branch block, 528 with ST depression and 1,258 with neither ST elevation nor depression. No overall benefit from rt-PA versus placebo with respect to mortality rate at 1 year was seen among patients presenting with ST elevation (21.2% vs. 22.4%, p = 0.5 [90% power to detect 20% relative difference]). Patients with ST elevation who were treated with rt-PA versus placebo <3 h after hospital admission had a lower mortality rate at 1 year (15.8% vs. 19.6%, p = 0.028) than did those treated after 3 h (17.6% vs. 13.0%, p = 0.055). Patients presenting initially with ST depression >2 mm had significant benefit from treatment with rt-PA with respect to 1 year mortality rate (20.1% vs. 31.9%, p = 0.006).

CONCLUSIONS

Patients with non-Q wave myocardial infarction constitute a heterogeneous group of patients. Although the observations presented here are limited by post hoc analysis, it is apparent that patients classified as having a non-Q wave infarction after thrombolytic therapy have a better prognosis than do those given placebo. Late admission of thrombolytic therapy (after 6 h) may also be beneficial in patients presenting with ST depression >2 mm and confirmed myocardial infarction. These hypotheses require prospective testing in a larger number of patients.