Impact of late coronary artery reperfusion on left ventricular function one month after acute myocardial infarction (results from the ISAM study)

Impact of chronic patency of infarct-related coronary artery on prevalence of myocardial ischemia during the pharmacologic and exercise stress test

BACKGROUND

Even late restoration of anterograde coronary flow may have beneficial effects on left ventricular function, electrophysiology, and survival in postinfarction patients.

HYPOTHESIS

The patency or occlusion of an infarct-related coronary artery in the chronic phase may also be associated with myocardial ischemia provoked by pharmacologic and physiologic stress tests.

METHODS

High-dose dipyridamole echocardiography test (DET) (up to 0.84 mg/kg over 10 min), exercise electrocardiography (EET), and coronary angiographic data in a group of 127 in-hospital patients who had survived an acute myocardial infarction were analyzed. Patients who had only angiographic evidence of infarct-related single artery disease (> or = 50% luminal diameter reduction) and no previous revascularization were enrolled in the study. DET and EET were performed (DET in all, EET in 118 patients) within 5 days before coronary angiography. Fifty-seven patients had total occluded infarct arteries (Group 1) with various degrees of collateral circulation (2.6 +/- 1.1 collateral score, by a 3 grading system), whereas the other 70 patients had patent infarct arteries (Group 2) with significant residual stenoses (82 +/- 13% diameter reduction).

RESULTS

The prevalence of rest angina or effort angina and topography of the infarct-related coronary artery did not differ between the two groups (all p = NS). There were more patients with Q wave in Group 1 than in Group 2 (72 vs. 57%, p = 0.08) compared with non-Q wave infarction (Group 1 = 28 vs. Group 2 = 43%, p = 0.08). Ischemia in the infarct-related artery territory detected by DET (defined as new wall motion dyssynergy or marked worsening of resting hypokinesia) was 61% in Group 1 and 41% in Group 2 (p = 0.025). EET was positive in 26 of 54 (48%) Group 1 and in 21 of 64 (33%) Group 2 patients (p = 0.09).

CONCLUSIONS

Patients with occluded infarct-related arteries have a higher prevalence of ischemia during DET and EET regardless of the presence of collateral flow. These results suggest that the presence of partial anterograde flow in the prolonged period could have a favorable influence on prevalence of residual ischemia in these patients.

Long-term prognosis of late spontaneous reperfusion after failed thrombolysis for acute myocardial infarction

BACKGROUND

Early reperfusion improves left ventricular (LV) function and survival after acute myocardial infarction (MI). Thrombolytic therapy achieves early patency of the infarct artery in about two-thirds of patients. In nearly half of the remaining patients, in whom early reperfusion was not achieved with thrombolytic therapy, the infarct artery might reopen by the time of predischarge angiography. However, the impact of such late spontaneous reperfusion after failed thrombolytic therapy on LV function and long-term survival remained unclear.

HYPOTHESIS

This study was undertaken to assess implication of late spontaneous reperfusion after failed thrombolytic therapy on LV function and long-term survival after acute MI.

METHODS

The study consisted of 198 patients with anterior acute MI who underwent thrombolytic therapy and predischarge angiography: 160 patients with infarct artery patent early and late after therapy (persistent patency), 17 patients with infarct artery occluded early after therapy but patent at predischarge angiography (late spontaneous reperfusion), and 21 patients with infarct artery occluded early and late after therapy (persistent occlusion).

RESULTS

Persistent patency was associated with enhanced improvement in LV ejection fraction (7.7 +/- 11.8%) compared with late spontaneous reperfusion (0.0 +/- 9.6%, p = 0.03) and persistent occlusion (-1.4 +/- 9.7%, p = 0.003). Persistent patency was associated with better long-term survival than with late spontaneous reperfusion (p < 0.001) and persistent occlusion (p < 0.001). Multivariate analysis comparing persistent patency and late spontaneous reperfusion showed that early reperfusion was an independent predictor of long-term survival.

CONCLUSION

Late spontaneous reperfusion after failed thrombolytic therapy was associated with poor LV function and long-term survival, emphasizing the importance of early reperfusion.

Effects of revascularization after first acute myocardial infarction on the evolution of QRS complex changes (the DANAMI trial). DANish Trial in Acute Myocardial Infarction

The changes in QRS complex morphology associated with acute myocardial infarction (AMI) can resolve spontaneously over time. Whether complete revascularization of the infarct-related myocardial territory after AMI affects this QRS resolution has not been studied adequately. The present study compares the evolution of the changes in the QRS complex associated with AMI during 1-year follow-up in patients treated with or without revascularization after their first thrombolyzed AMI. The study is a substudy of the DANish Trial in Acute Myocardial Infarction (DANAMI) (n = 1,008) that randomized patients with inducible ischemia after their first AMI, treated with intravenous thrombolytic therapy, to conservative treatment or coronary angiography followed by the appropriate revascularization strategy. A total of 817 patients had complete sets of evaluable electrocardiograms. Electrocardiograms were obtained at randomization, and at 3, 6, and 12 months of follow-up and subjected to blinded core-laboratory evaluation according to the Selvester QRS scoring method. This score considers Q-, R-, and S-wave duration and ratios to provide a semiquantitative estimate of AMI size. The median electrocardiographic estimated infarct size in the entire population was 15% of the left ventricle at randomization. At the end of the follow-up period this estimate had decreased to 12% (p < 0.00001). There was no difference in the rate of QRS resolution whether the patients were subgrouped according to randomization or subgrouped according to actual treatment with or without revascularization. The present study confirms the findings from previous studies conducted in the prethrombolytic era, that considerable normalization of the QRS complex also occurs after AMI treated with thrombolytic therapy. This QRS normalization seems unaffected by an aggressive treatment strategy with revascularization via balloon angioplasty or bypass surgery.

[The prognostic factors after an acute myocardial infarct treated with fibrinolytics]

BACKGROUND

The usefulness of the exercise test in evaluating patients with an acute myocardial infarction treated with fibrinolytics is controversial. On the other hand, the prognostic value of a patent infarct-related artery has not been clearly established. The objectives of this study were to assess the validity of the exercise test and to study the prognostic value of the artery patency after a myocardial infarction.

MATERIAL AND METHODS

We studied 99 patients with a myocardial infarction treated with fibrinolytics, non-complicated. An exercise test and a cardiac catheterization were performed in the first month. The patients were followed-up for 2 years, recording the major cardiac events (death and reinfarction) and the minor events (angina class (II, left cardiac failure class (II or maintained ventricular tachycardia).

RESULTS

On multivariate analysis with Cox regression, a workload < 4 METS at the exercise test was the only independent prognostic factor of major events (RR 5.6; CI 95% 1.68-19). The independent prognostic factors of minor events were: multivessel disease (RR 3.36; CI 95% 1.56-7.24), anterior infarction (RR 3.15; CI 95% 1.3-7.6), abnormal exercise test (RR 2.98; CI 95% 1.46-6.09) and ejection fraction < or = 40% (RR 2.48; CI 95% 1.07-5.74). The patency of the infarct-related artery was not a predictor of events.

CONCLUSIONS

The exercise test is useful in predicting the prognosis in patients treated with fibrinolytics. An occluded infarct-related artery was not an independent predictor of cardiac events in 2 years of follow-up.

Routine Coronary Arteriography Following Thrombolytic Therapy for Acute Myocardial Infarction: An Unsettled Controversy

Although coronary artery disease remains the leading cause of death in industrialized countries, the management of patients recovering from acute myocardial infarction varies significantly. The issue of routine arteriography and revascularization following thrombolytic therapy remains controversial despite substantial evidence associating infarct-related artery patency with improved cardiac function and survival. Randomized trials of routine intervention after myocardial infarction have generally failed to demonstrate advantages of this invasive approach but methodological problems limit their application to current practice. High-risk patients should be referred for arteriography. While awaiting definitive trials addressing the influence of routine arteriography on patient survival and its cost effectiveness, the management of other patient groups must be individualized.

Accuracy of dobutamine echocardiography for detection of myocardial viability in patients with an occluded left anterior descending coronary artery

OBJECTIVES

We studied the accuracy of dobutamine echocardiography for the detection of myocardial viability in patients with an occluded left anterior descending coronary artery and regional ventricular dysfunction.

BACKGROUND

Contractile reserve during dobutamine echocardiography is an accurate marker of myocardial viability in patients with coronary stenoses and ventricular dysfunction. However, its accuracy in patients with an occluded vessel has not been evaluated.

METHODS

We studied 41 patients with > 50% stenosis of the left anterior descending coronary artery and regional ventricular dysfunction who underwent dobutamine echocardiography for detection of viable myocardium. Contractile reserve was defined as improvement in wall motion score of two or more contiguous septal or anterior segments during doubutamine echocardiography. Recovery of function was defined as improvement in rest wall motion score of two or more contiguous segments after revascularization.

RESULTS

Patients were classified into two groups according to the presence (n = 20) or absence (n = 21) of left anterior descending coronary artery occlusion. Contractile reserve was detected in 40% of patients with an occluded and 43% with a nonoccluded artery (p = 0.8). Of 41 patients, 27 underwent revascularization, 12 with and 15 without an occluded vessel. Recovery of function occurred in 6 (50%) of 12 patients in the occluded artery group and in 5 (33%) of 15 in the nonoccluded artery group (p = 0.4). Among patients with an occluded artery, the positive and negative predictive values of dobutamine echocardiography for recovery of function were 100% (95% confidence interval [CI] 48% to 100%) and 86% (95% CI 42% to 100%), respectively.

CONCLUSIONS

Our results indicate that contractile reserve during dobutamine echocardiography can be detected in patients with an occluded vessel and may be useful for predicting recovery of function after revascularization.

Dobutamine stress echocardiography early after myocardial infarction treated with thrombolysis. Identification of myocardial viability and ischemia and relation to spontaneous functional recovery

The aim of the study was to assess the ability of dobutamine stress echocardiography to detect myocardial viability and ischemia in patients with acute myocardial infarction treated with thrombolysis and to correlate the acute response to dobutamine with late spontaneous functional recovery at follow-up. Forty-two consecutive patients with myocardial infarction treated with thrombolysis underwent low- (5 and 10 mcg/kg/min) and high-dose (20 to 40 mcg/kg/min) dobutamine stress echocardiography at a mean of 7 +/- 3 days of the acute phase. A follow-up 2D-echocardiogram was performed in all patients to evaluate the spontaneous recovery of function in the infarct area. On the basis of the response to the test, 3 groups of patients were identified: group 1 included 7 patients showing an improvement in left ventricular asynergy score index at low doses (from 1.5 +/- 0.3 to 1.3 +/- 0.2, p < 0.05) with no deterioration at high doses, indicative of myocardial viability without ischemia; group 2 (23 patients) showed a significant improvement in the asynergy index at low doses (from 1.58 +/- 0.3 to 1.32 +/- 0.32, p < 0.05) followed by a deterioration at high doses (1.68 +/- 0.4, p < 0.05 vs low-dose), suggestive of residual myocardial ischemia in the infarct zone; group 3 included 12 patients who showed no significant changes in the baseline asynergy score index (1.67 +/- 0.2) either at low or at high doses. The acute response to dobutamine stress echocardiography accurately predicted the spontaneous recovery of function in the infarct area at follow-up: both group 1 and group 2 patients showed a significant reduction in the asynergy score index (group 1: 1.16 +/- 0.3 vs 1.5 +/- 0.2, p < 0.001; group 2: 1.43 +/- 0.3 vs 1.58 +/- 0.3, p < 0.05), while group 3 had no recovery in the asynergy index (1.67 +/- 0.2 vs 1.67 +/- 0.2). Thus, in patients with acute myocardial infarction treated with thrombolysis dobutamine stress echocardiography can detect myocardial viability in 71% and ischemia in the infarct zone in 55% of patients; moreover, the response to the test during the acute phase is correlated with the degree of the late spontaneous recovery of function in the infarct area.

Incomplete, delayed functional recovery late after reperfusion following acute myocardial infarction: "maimed myocardium"

The objective of the current editorial is to introduce a new concept ("maimed myocardium") that we believe describes more accurately the incomplete, delayed recovery of LV function that may occur late after reperfusion after AMI. It has been demonstrated previously that myocardium remains viable for a prolonged period in many patients with nonsustained coronary occlusion, despite the occurrence of myocardial necrosis; late reperfusion may result in myocardial salvage in reversibly ischemic (stunned) segments (complete recovery) and in intensely injured (maimed) segments that display partial return of LV function over time (incomplete recovery). Clinically, the basis for maimed myocardium is the observation that delayed, LV functional recovery may occur in partially infarcted segments where there has been an antecedent ischemic insult of sufficient duration to result in some degree of myocardial necrosis. Certain acute coronary syndromes characterized by nonsustained coronary occlusion followed by spontaneous reperfusion (e.g., non-Q-wave AMI) or drug-induced reperfusion induced by the exogenous administration of thrombolytic therapy are associated with incomplete, delayed recovery of LV function as detected clinically by partial improvement in serial radionuclide-ejection measurement, enhanced metabolic integrity of cardiac tissue by F-18 deoxyglucose myocardial imaging, and scintigraphic findings of reverse thallium redistribution--findings that support the presence of partially viable myocardium that has been incompletely salvaged during reperfusion late after AMI. Experimentally, delayed LV functional recovery has been reported in animal models in which prolonged coronary occlusion (hours to days) followed by reperfusion is associated with late recovery of regional LV function in myocardial segments subtending border (stunned) zones and central infarct (maimed) zones. In studies in animals and human beings, postextrasystolic potentiation and pharmacologic inotropic interventions may augment maimed and stunned segments, although the magnitude of regional contractile reserve that can be unmasked with these interventions is quantitatively less in the maimed than in stunned segments. In summary, the propensity of intensely injured or partially infarcted LV segments to display intermediate functional recovery followed by reperfusion late after coronary occlusion suggests that even severely depressed but residually viable cardiac muscle can be salvaged incompletely over time.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of infarct artery patency on prognosis after acute myocardial infarction. The Survival and Ventricular Enlargement Investigators

BACKGROUND

In patients with acute myocardial infarction (MI), early restoration of patency of the infarct-related artery (IRA) leads to preservation of left ventricular function and improved clinical outcome. However, there is evidence that the benefits associated with a patent IRA are out of proportion to the observed improvement in ventricular function and may result not only from salvage of ischemic myocardium but also from the opening of the IRA beyond a narrow postinfarct time window. The objectives of this study were (1) to assess the effect of IRA patency on outcome of patients after acute MI with left ventricular dysfunction while controlling for differences in left ventricular ejection fraction and the extent of coronary disease and (2) to determine the effect of angiotensin-converting enzyme (ACE) inhibitor therapy on patients with patent as well as occluded infarct arteries.

METHODS AND RESULTS

The Survival and Ventricular Enlargement (SAVE) study consisted of 2231 patients with a documented MI and a left ventricular ejection fraction < or = 40%. They were randomized to the ACE inhibitor captopril (50 mg TID) or placebo 3 to 16 days after MI and were followed for an average of 3.5 years. Left ventricular ejection fraction, measured with radionuclide left ventriculography, was repeated at the end of the follow-up period. The 946 patients in whom the patency of the IRA was established before randomization form the basis of this study. At cardiac catheterization averaging 4.2 days after infarction, 30.7% of patients had an initially occluded IRA. After revascularization, 162 of the 946 patients (17.1%) were left with an occluded IRA at the time of randomization. The 162 patients with persistently occluded IRAs and 784 with patent IRAs had similar clinical baseline characteristics, but those with occluded arteries had a slightly lower ejection fraction than the 784 patients with patent infarct arteries (30% versus 32%, P = .01). Cox proportional-hazards analyses showed that the independent predictors of all-cause mortality were hypertension (relative risk [RR] 1.94, P < .001), number of diseased coronary arteries (RR 1.68, P < .001), occluded IRA (RR 1.49, P = .039), ejection fraction (RR 1.36, P < .001), age (RR 1.10, P = .030), and use of beta-adrenergic receptor blocking agents (RR 0.60, P = .007). Independent predictors of a composite end point consisting of cardiovascular mortality, morbidity, or reduction of ejection fraction of > or = 9 units were occluded IRA (odds ratio [OR] 1.73, P = .002), hypertension (OR 1.71, P < .001), number of diseased vessels (OR 1.38, P < .001), ejection fraction (OR 1.18, P = .003), use of beta-adrenergic receptor blocking agents (OR 0.67, P = .007), and randomization to captopril (OR 0.70, P = .009).

CONCLUSIONS

IRA patency within 16 days after MI predicts a favorable clinical outcome, independent of the number of obstructed coronary arteries or of left ventricular function. The beneficial effect of ACE inhibition is independent of patency status of the IRA. These findings support the need for additional, prospective clinical trials of late reperfusion in MI patients.

Prolonged intracoronary infusion of streptokinase: an alternative pharmacologic approach to extensive thrombus in native coronary artery

Several reports suggest that pretreatment of intracoronary thrombus with fibrinolytic agents may reduce the risk for complications during subsequent balloon angioplasty. We report a case, for the first time, of successful lysis of an extensive thrombus in a native coronary artery by administering a prolonged intracoronary infusion of streptokinase to facilitate subsequent angioplasty and discuss the management strategy when intracoronary thrombus is encountered.

Value of low-dose echodobutamine in the diagnosis of patency of the infarct related coronary artery

The resumption of contractility of asynergic segments in survivors after acute myocardial infarction (AMI) may be detected in viable myocardial areas. We have correlated the detection of viable myocardium, assessed with low dose dobutamine testing, with coronary angiography and clinical outcome in 66 consecutive survivors of AMI using the echocardiographic evidence of left ventricular wall motion abnormalities. The test enabled the identification of two groups: group A, comprising 32 patients (pts) demonstrating wall motion recovery at dobutamine infusion and group B, comprising 34 pts without wall motion recovery. The mean basal asynergy score index was 5.8 +/- 4.2 in group A and 6.0 +/- 4.2 in group B (p = ns). With dobutamine testing the score decreased to 2.8 +/- 3.6 in group A (p < 0.001 with respect to basal value), while it did not change significantly in group B. Left ventricular end diastolic volume (ml) was similar in the two groups (114 +/- 35 vs 107 +/- 79, p = NS). The infarct related artery (IRA) patency rate was 87.5% in group A, vs 26.5% in group B (p < 0.001). After a mean follow-up of 11 +/- 5 months, group A pts had basal asynergy score improvement (2.6 +/- 3.1, p < 0.001) and mild left ventricular end diastolic volume (ml) reduction, (108 +/- 32, p = NS), while group B pts had left ventricle end diastolic volume enlargement (130 +/- 38, p < 0.05), without score asynergy modification. Moreover all pts who experienced heart failure at follow-up were in group B.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of late percutaneous transluminal coronary angioplasty of an occluded infarct-related coronary artery on left ventricular function in patients with a recent (< 6 weeks) Q-wave acute myocardial infarction (Total Occlusion Post-Myocardial Infarction Intervention Study [TOMIIS]--a pilot study)

The effect of late percutaneous transluminal coronary angioplasty (PTCA) of an occluded infarct-related artery on left ventricular ejection fraction was studied in patients with a recent, first Q-wave myocardial infarction in a prospective, randomized study. Forty-four patients (31 men and 13 women, mean age 58 +/- 12 years) with an occluded infarct-related coronary artery were randomized to PTCA (n = 25) or no PTCA (n = 19). Patients received acetylsalicylic acid, a beta blocker and an angiotensin-converting enzyme inhibitor unless contraindicated. Left ventricular ejection fraction was determined at baseline and 4 months. Coronary angiography was repeated at 4 months. Baseline ejection fraction measured 20 +/- 12 days after myocardial infarction was 45 +/- 12% in both groups. PTCA was performed 21 +/- 13 days after the event. The primary PTCA success rate was 72%. One patient in each group died before angiographic follow-up, which was completed in 37 of the remaining 42 patients (88%; 21 with and 16 without PTCA). At 4 months, the infarct-related artery was patent in 43% of PTCA patients and in 19% of no PTCA patients (p = NS). Reocclusion occurred in 40% of patients after successful PTCA. Secondary analyses showed that the change in left ventricular ejection fraction was significantly greater in patients with a patent infarct-related artery (+9.4 +/- 6.2%) than in those with an occluded artery (+1.6 +/- 8.8%; p = 0.0096). Baseline ejection fraction also independently predicted improvement in left ventricular ejection fraction (p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Indications for fibrinolytic therapy in suspected acute myocardial infarction: collaborative overview of early mortality and major morbidity results from all randomised trials of more than 1000 patients. Fibrinolytic Therapy Trialists' (FTT) Collaborative Group

Large randomised trials have demonstrated that fibrinolytic therapy can reduce mortality in patients with suspected acute myocardial infarction (AMI). The indications for, and contraindications to, this treatment in some categories of patient are disputed, examples being late presentation, elderly patients, and those in cardiogenic shock. This overview aims to help resolve some of the remaining uncertainties. From all trials of fibrinolytic therapy versus control that randomised more than 1000 patients with suspected AMI, information was sought and checked on deaths during the first 5 weeks and on major adverse events occurring during hospitalisation. The nine trials included 58,600 patients, among whom 6177 (10.5%) deaths, 564 (1.0%) strokes, and 436 (0.7%) major non-cerebral bleeds were reported. Fibrinolytic therapy was associated with an excess of deaths during days 0-1 (especially among patients presenting more than 12 h after symptom onset, and in the elderly) but this was outweighed by a much larger benefit during days 2-35. This "early hazard" should not obscure the very clear overall survival advantage that is produced by fibrinolytic therapy. Benefit was observed among patients presenting with ST elevation or bundle-branch block (BBB)--irrespective of age, sex, blood pressure, heart rate, or previous history of myocardial infarction or diabetes--and was greater the earlier treatment began. Among the 45,000 patients presenting with ST elevation or BBB the relation between benefit and delay from symptom onset indicated highly significant absolute mortality reductions of about 30 per 1000 for those presenting within 0-6 h and of about 20 per 1000 for those presenting 7-12 h from onset, and a statistically uncertain benefit of about 10 per 1000 for those presenting at 13-18 h (with more randomised evidence needed in this latter group to assess reliably the net effects of treatment). Fibrinolytic therapy was associated with about 4 extra strokes per 1000 during days 0-1: of these, 2 were associated with early death and so were already accounted for in the overall mortality reduction, 1 was moderately or severely disabling, and 1 was not. This overview indicates that fibrinolytic therapy is beneficial in a much wider range of patients than is currently given such treatment routinely.

Is there an age limit for thrombolytic therapy?

Thrombolytic therapy has revolutionized the treatment of acute myocardial infarction. The mortality of infarction increases very steeply with increasing age > 65 years. One-month mortality in such patients is in the range of 20-30%. The proportional benefit of lytic treatment is somewhat less in these older patients, but since mortality is high, the absolute benefit is as large or larger than that in younger patients. The risks of stroke due to thrombolysis are balanced between increased risk of cerebral hemorrhage but decreased risk for ischemic/embolic stroke. This trade-off results, overall, in a slightly increased stroke rate of about 1-2 per 1,000 nonfatal strokes, but with about 20 fewer deaths per 1,000 myocardial infarctions. In addition to these striking mortality benefits, there are also important reductions in infarct size, leading to decreased morbidity from heart failure or arrhythmias.

Dobutamine stress echocardiography for assessment of myocardial viability and ischemia in acute myocardial infarction treated with thrombolysis

To evaluate the role of dobutamine echocardiography for early assessment of myocardial viability and ischemia in acute myocardial infarction (MI), 59 patients with thrombolyzed acute MI underwent low- (5-10 micrograms/kg/min, 8 patients) and high-dose (20-40 micrograms/kg/min, 51 patients) dobutamine echocardiography at a mean of 8 +/- 4 days after acute MI. Myocardial viability in the infarct zone was documented in 43 of 59 (73%) patients (group 1), in whom mean asynergy score index decreased from 1.6 +/- 0.3 at baseline to 1.3 +/- 0.2 (p < 0.001), after low-dose dobutamine. No viability was present in 16 of 59 (27%) patients (group 2). At follow-up, recovery of regional contractile function was observed in group 1 (asynergy score index decreased from 1.6 +/- 0.3 to 1.4 +/- 0.3; p < 0.001), but not in group 2 patients. Sensitivity, specificity, and negative and positive predictive values of low-dose dobutamine echocardiography in predicting spontaneous recovery of function were 79%, 68%, 50%, and 89%, respectively. Of the 51 patients who underwent high-dose dobutamine, 26 of 36 (72%) group 1 patients showed a deterioration of contractility in the infarct zone indicative of myocardial ischemia compared with only 1 of 15 (7%) group 2 patients. At follow-up, recovery of regional function was greater in patients with no evidence of myocardial ischemia at high doses than in those with an ischemic response.(ABSTRACT TRUNCATED AT 250 WORDS)

Prehospital thrombolysis: beneficial effects of very early treatment on infarct size and left ventricular function

OBJECTIVES

The purpose of this study was to compare the effects of very early (< or = 1.5 h after symptom onset) and later (> 1.5 up to 4 h) thrombolytic therapy on infarct size, left ventricular function and early mortality in patients with acute myocardial infarction. To start thrombolysis at the earliest possible moment, it was performed in the prehospital setting. A cutoff time of 1.5 h was prospectively stipulated.

BACKGROUND

Shortening of ischemic time is crucial within the 1st 2 h. Prehospital thrombolysis can reduce time to treatment and enables very early initiation of therapy for many patients.

METHODS

One hundred seventy patients received 30 mg of anistreplase up to 4 h from symptom onset by a mobile intensive care unit physician. Infarct size was measured from cumulative release of alpha-hydroxybutyrate dehydrogenase, and left ventricular function was assessed by contrast angiograms 10 days after the infarction.

RESULTS

The decision to treat on scene was correct in 98% of patients. There were no bleeding complications or deaths outside the hospital setting. In 28 patients (17%) the ischemic process was interrupted. Findings with thrombolytic therapy initiated < or = 1.5 (96 patients) versus > 1.5 h (74 patients) were the following: initial extent of epicardial injury, 1.6 +/- 0.9 versus 1.4 +/- 0.7 mV, p = NS; infarct size by cardiac enzyme release 646 +/- 634 versus 886 +/- 712 IU/liter, p < 0.05; ejection fraction 57 +/- 14% versus 51 +/- 13%, p < 0.05; regional dyssynergic area 24 +/- 22 versus 33 +/- 24 U, p < 0.05; 21-day mortality 1 of 96 versus 5 of 74 patients (1% vs. 7%, p < 0.05).

CONCLUSIONS

The data suggest that in evolving myocardial infarction up to 4 h in duration, the start of thrombolytic therapy at < or = 1.5 h compared with > 1.5 h limits infarct size, preserves left ventricular function and may save lives.

Sudden increase of the ST segment elevation at time of reperfusion predicts extensive infarcts in patients with intravenous thrombolysis

Within 4 hours from the onset of symptoms in 61 patients with myocardial infarction and intravenous thrombolysis, ST segment elevation and creatine phosphokinase (CK) were measured every 15 minutes. Because of a premature enzyme rise, 42 patients (69%) were reperfused early (group 1). Immediately following reperfusion, eight of them (13%, group 1a) showed a marked increase of the ST elevation, in six of whom it was associated with clearly intensified chest pain. These patients exhibited a much steeper enzyme release and developed a larger enzymatic infarct size than patients (group 1b) without an additional transient ST elevation at reperfusion (CK peak 5.1 +/- 1.6 vs 9.8 +/- 4.2 hours after the start of thrombolysis; CK release 48 +/- 22 vs 19 +/- 18 IU/ml x hours, both p < 0.005). At angiography 11 days later, left ventricular function was significantly worse in group 1a than in group 1b (regional dyssynergic area 51 +/- 24 vs 21 +/- 18, global ejection fraction 39 +/- 14 vs 58 +/- 11; both p < 0.0005). During intravenous thrombolysis in acute myocardial infarction, some patients show a marked transient increase of the ST segment elevation at reperfusion. Their enzyme rise is very rapid and suggests a special reperfusion pattern. Most of these patients suffered large infarcts.

Progressive left ventricular dysfunction and remodeling after myocardial infarction. Potential mechanisms and early predictors

BACKGROUND

Left ventricular enlargement and the development of chronic heart failure are potent predictors of survival in patients after myocardial infarction. Prospective studies relating progressive ventricular enlargement in individual patients to global and regional cardiac dysfunction and the onset of late chronic heart failure are not available. It was the aim of this study to define the relation between left ventricular dilatation and global and regional cardiac dysfunction and to identify early predictors of enlargement and chronic heart failure in patients after myocardial infarction.

METHODS AND RESULTS

Left ventricular volumes, regional area shrinkage fraction in 18 predefined sectors (gated single photon emission computed tomography), global ejection fraction, and hemodynamics at rest and during exercise (supine bicycle, 50 W, 4 minutes, Swan-Ganz catheter) were assessed prospectively 4 days, 4 weeks, 6 months, and 1.5 and 3 years after first myocardial infarction. Seventy patients were assigned to groups with progressive, limited, or no dilatation. Patients without dilatation (n = 38) maintained normal volumes and hemodynamics until 3 years. With limited dilatation (n = 18), left ventricular volume increased up to 4 weeks after infarction and stabilized thereafter; depressed stroke volume was restored 4 weeks after infarction and then remained stable at rest. Wedge pressure during exercise, however, progressively increased. With progressive dilatation (n = 14), depressed cardiac and stroke indexes were also restored by 4 weeks but progressively deteriorated thereafter. Area shrinkage fraction as an estimate of regional left ventricular function in normokinetic sectors at 4 days gradually deteriorated during 3 years, but hypokinetic and dyskinetic sectors remained unchanged. Global ejection fraction fell after 1.5 years, whereas right atrial pressure, wedge pressure, and systemic vascular resistance increased. By multivariate analysis, ejection fraction and stroke index at 4 days, ventriculographic infarct size, infarct location, and Thrombolysis in Myocardial Infarction trial grade of infarct artery perfusion were significant predictors of progressive ventricular enlargement and chronic dysfunction.

CONCLUSIONS

Almost 26% of patients may develop limited left ventricular dilatation within 4 weeks after first infarction, which helps to restore cardiac index and stroke index at rest and to preserve exercise performance and therefore remains compensatory. A somewhat smaller group (20%) develops progressive structural left ventricular dilatation, which is compensatory at first, then progresses to noncompensatory dilatation, and finally results in severe global left ventricular dysfunction. In these patients, depression of global ejection fraction probably results from impairment of function of initially normally contracting myocardium. Early predictors from multivariate analysis allow identification of patients at high risk for progressive left ventricular dilatation and chronic ventricular dysfunction within 4 weeks after acute infarction.

Effects of late (1 to 30 days) reperfusion after acute myocardial infarction on the signal-averaged electrocardiogram

Early reperfusion (4 to 6 hours) after acute myocardial infarction reduces mortality and reduces the incidence of late potentials on a signal-averaged electrocardiogram (SAECG). Recent reports suggest that reperfusion accomplished after > 6 hours also may reduce mortality. The effect of such later reperfusion on the SAECG is not known. We hypothesized that reperfusion by angioplasty accomplished > 24 hours after onset of infarction would reduce late potentials and improve the parameters on the SAECG. Forty-one patients with a totally occluded infarct-related artery 12 +/- 8 days after infarction underwent attempted angioplasty. SAECG, echocardiography and thallium-201 imaging were performed before and 1 month after attempted angioplasty. Angioplasty resulted in successful reperfusion in 32 patients and was unsuccessful in 9. No change in the incidence of late potentials occurred after successful reperfusion (13 of 32 patients before and 13 of 32 patients 1 month later) or after unsuccessful reperfusion (6 of 9 patients before and 5 of 9 patients 1 month later). Among patients with successful reperfusion, no significant change occurred in the QRS duration or the terminal signal duration < 40 microV. The terminal root-mean-square voltage in microvolts improved significantly at 1 month (31 +/- 25 before to 38 +/- 29 after, p = 0.004). Twenty-two of 32 patients with successful reperfusion had improved wall motion in the infarct zone at 1 month. Despite an improvement in function in these patients, no change in the incidence of late potentials occurred by 1 month.(ABSTRACT TRUNCATED AT 250 WORDS)

Patency of the infarct-related artery and left ventricular function as the major determinants of survival after Q-wave acute myocardial infarction

One hundred seventy-two patients with 1-vessel disease documented at predischarge angiography who had been followed for 43 +/- 30 months after an initial Q-wave acute myocardial infarction were retrospectively evaluated to investigate the prognostic value of infarct-related artery patency and left ventricular (LV) function. Multiple logistic regression analysis revealed that only infarct artery patency (Thrombolysis in Myocardial Infarction [TIMI] grades 2-3 vs 0-1) (Z = 2.24; p < 0.05) and end-systolic volume index (Z = -2.67; p < 0.01) were independently related to survival. Sixteen cardiac deaths were observed; all 16 patients had LV dysfunction (defined as end-systolic volume index > 40 ml/m2), and 15 had an occluded infarct-related artery. In the subgroup with LV dysfunction, the 10-year percent survival rate was 20% among patients with TIMI grade 0 to 1 versus 96% with grade 2-3 (p < 0.001). Patency of the infarct-related artery was also the only independent predictor of recurrent ischemia (Z = 2.59; p < 0.01). In conclusion, both infarct-related artery patency and LV function are independent predictors of survival after Q-wave acute myocardial infarction. Patients with normal LV function have an excellent long-term prognosis, which is only partially counterbalanced by the tendency toward clinical instability observed in those with an open infarct-related vessel. However, when an occluded infarct-related artery is observed in the setting of LV dysfunction, the long-term outcome appears to be relatively poor.

An association between collateral blood flow and myocardial viability in patients with recent myocardial infarction

BACKGROUND

We hypothesized that successful reperfusion of an occluded infarct-related coronary artery even late after acute myocardial infarction would result in improved regional wall motion and that such improvement might be related to the presence of collateral blood flow within the infarct bed.

METHODS

We assessed regional wall motion by two-dimensional echocardiography at base line and one month after angioplasty was attempted in the occluded infarct-related artery in 43 patients who had had a myocardial infarction two days to five weeks earlier. A wall-motion score was assigned to each patient on a five-point scale (from 1 [normal function] to 5 [dyskinesia]). The percentage of the infarct bed perfused by collateral flow was assessed with myocardial contrast echocardiography.

RESULTS

In the 41 patients who had abnormal wall motion at base line, improvement in function was noted in 25 (78 percent) of the 32 in whom angioplasty was successful, as compared with only 1 (11 percent) of the 9 in whom it was unsuccessful (P < 0.001). The percentage of the infarct bed supplied by collateral flow at base line was directly correlated with wall function and inversely correlated with the wall-motion score one month after successful angioplasty (r = -0.64, P < 0.001). Among the patients in whom angioplasty was successful, the 23 in whom > 50 percent of the infarct bed was supplied by collateral flow had better wall motion (P < 0.001) and greater improvement in wall motion at one month (P = 0.004) than the 9 in whom < or = 50 percent of the bed was supplied by collateral flow. The degree of improvement in function was not influenced by the length of time between the infarction and the attempted angioplasty.

CONCLUSIONS

The myocardium remains viable for a prolonged period in many patients with acute infarction and an occluded infarct-related artery. Viability appears to be associated with the presence of collateral blood flow within the infarct bed.

Importance of early and complete reperfusion to achieve myocardial salvage after thrombolysis in acute myocardial infarction

The importance of the timing and completeness of coronary artery reperfusion for limitation of acute myocardial infarction (AMI) size after intravenous thrombolytic therapy was studied in 39 patients. All had electrocardiographic epicardial injury and acute coronary angiography performed < 8 hours after symptom onset. Acutely jeopardized myocardium was estimated at baseline, and before and after angiography by quantitative ST-segment analysis. The AMI size was estimated on the final electrocardiogram by the Selvester QRS score. Left ventricular ejection fraction was measured at the time of acute angiography and before discharge in 31 of these patients. In the 21 patients with normal flow (Thrombolysis in Myocardial Infarction [TIMI] trial grade 3) in the infarct-related artery, the amount of jeopardized myocardium decreased from baseline to that before and after angiography (17 to 11 and 11%, respectively; p < 0.00005), and the median final AMI size was reduced (17 to 9%; p = 0.0004). In 6 patients with suboptimal flow (TIMI grade 2), the median amount of jeopardized myocardium decreased slightly from baseline to that before to after angiography (15 to 12%); however, the median final AMI size was not reduced (17%). In 12 patients with no reperfusion (TIMI 0 to 1) flow, the median amount of jeopardized myocardium remained unchanged from baseline to that before angiography (21%), and the final AMI size was not significantly reduced. There was a significant inverse correlation between the change in global left ventricular function and the difference between electrocardiographic estimated jeopardized and final AMI size (rs = -0.53; p = 0.008).(ABSTRACT TRUNCATED AT 250 WORDS)

A patency-oriented strategy for early management of acute myocardial infarction using emergency coronary angiography and selective coronary angioplasty

From June 1988 to March 1991, an unselected cohort of 150 consecutive patients with acute myocardial infarction (AMI) (less than 6 hours) was managed according to a strategy designed to ensure early patency of the infarct-related artery in the maximum number of patients. The following procedures were used: (1) intravenous thrombolysis, which was the usual treatment (n = 103), followed in 98 cases by emergency coronary angiography 90 minutes after the beginning of thrombolysis. This identified 31 thrombolysis failures (32%) and led to 19 rescue angioplasties (18 successes). All patients were then scheduled for predischarge angiography. (2) Direct angioplasty, which was performed in 40 patients because of contraindications to thrombolysis (n = 23), cardiogenic shock (n = 3), diagnostic doubt (n = 7) or "ideal" conditions for direct angioplasty (n = 7). Success (defined as Thrombolysis in Myocardial Infarction [TIMI] flow greater than 1, with a residual stenosis less than 50% in the infarct-related artery) was achieved in 36 of 40 patients (90%). (3) The 7 remaining patients were given conventional medical treatment because of advanced age, contraindications to thrombolysis and angioplasty, or spontaneous reperfusion (confirmed by emergency angiography). In all, emergency angioplasty was performed in the acute phase in 39% of the 150 patients in this nonselected cohort.(ABSTRACT TRUNCATED AT 250 WORDS)

Late direct angioplasty in patients with myocardial infarction and fluctuating chest pain

Myocardial infarctions may be associated with reduced but persistent blood flow to the infarct zone. We developed clinical criteria to select patients likely to have persistent perfusion to the infarct zone in the setting of acute myocardial infarction. Twenty-four consecutive patients with fluctuating pain and/or ST segment elevation who presented within 24 hours of the onset of infarction were studied with coronary angiography followed by direct percutaneous transluminal coronary angioplasty. Sixty-seven percent of patients had residual flow to the infarct territory. Eighteen patients had repeat angiography on day 9.4 +/- 4.1, and all arteries were patent (21% +/- 12% stenosis). Ejection fraction had risen from 50.0% +/- 15% to 54.0% +/- 14% (p less than 0.05). At follow-up (9.1 +/- 4.6 months), one patient died of noncardiac causes, and five redeveloped angina and underwent repeat procedures. Patients with fluctuating symptoms and/or ST segments are likely to have residual flow to the infarct zone, and late angioplasty may improve ventricular function in this group.

Patency of the infarct-related coronary artery and ventricular geometry

The pathogenesis of acute myocardial infarction (AMI) involves a sudden thrombotic occlusion of a coronary artery. Spontaneous or pharmacologic thrombolysis may lead to myocardial salvage if patency is achieved within a narrow time window. However, patients in whom thrombolysis occurs late seem to demonstrate improved left ventricular (LV) function and prognosis, which may be independent of myocardial salvage. Preservation of normal LV geometry by reducing expansion of the infarcted segment is a likely mechanism for this benefit. Infarct expansion is most pronounced in patients with anterior wall AMI who have a persistently occluded infarct-related vessel. This process of expansion leads to early increases in LV volume and distortions of LV contour (abnormal LV geometry). Patients whose infarct segment is largest, patients who have manifested infarct expansion, and patients with a persistently occluded infarct-related artery are at highest risk for progressive LV dilation. Experimental data support the concept that reperfusion of occluded vessels that occurs too late for myocardial salvage will preserve LV geometry by limiting infarct expansion. Prospective clinical trials should address whether there is a late, "second time window" during which infarct expansion and distortions of LV geometry may be reduced by (1) therapy with thrombolytic agents applied late after infarction, (2) late mechanical reperfusion with percutaneous transluminal coronary angioplasty (PTCA) or related methods, and (3) load-reducing agents to decrease remodeling, such as angiotensin-converting enzyme inhibitors or nitroglycerin.

Limitations of thrombolytic therapy for acute myocardial infarction complicated by congestive heart failure and cardiogenic shock

As many as one quarter of patients treated with thrombolytic therapy present with congestive heart failure or cardiogenic shock. Although thrombolytic therapy has been shown to limit infarct size, preserve left ventricular ejection fraction and decrease mortality in most subgroups of patients, no apparent benefit has been demonstrated in patients with clinical left ventricular dysfunction. The lack of correlation between ejection fraction and other measurements of left ventricular dysfunction such as exercise time, cardiac output, filling pressures, activation of the neurohumoral system and regional perfusion bed abnormalities may partly explain this paradox. Alternatively, lower perfusion rates, higher reocclusion rates, associated mechanical complications or completed infarction may explain these findings. Preliminary data indicate that emergency coronary angioplasty or bypass graft surgery improves survival in selected patients with cardiogenic shock. Because these findings suggest that restoration of infarct artery patency is especially important in patients with clinical left ventricular dysfunction, additional studies are needed in these patients to investigate the potential benefit that new thrombolytic strategies, inotropic or vasodilator agents or intraaortic balloon counterpulsation might offer by augmenting coronary blood flow and improving reperfusion rates. Currently, acute mechanical revascularization should be considered for patients who present with congestive heart failure associated with hypotension or tachycardia and for patients with cardiogenic shock.

Indices of reperfusion in patients with acute myocardial infarction using characteristics of the CK-MB time-activity curve

The purpose of this study was to identify indices of coronary artery reperfusion in patients treated with thrombolytic therapy for acute myocardial infarction (AMI) by means of characteristics from the serum creatine kinase (CK) isoenzyme MB time-activity curve. Frequent blood sampling as performed in three groups with a first AMI: 29 patients treated with intravenous thrombolytic therapy who had a patent infarct-related artery with normal flow (TIMI-3) at acute catheterization (reperfusion group); four patients with a persistently closed infarct-related artery (no reperfusion group); and 44 patients who did not receive any therapy aimed at coronary reperfusion (no thrombolytic therapy group). In the latter group we prospectively estimated that 25% would have spontaneous reperfusion. A physiologically based computer-calculated multi-compartment method was used to determine the characteristics of the serum CK-MB time-activity curve. In addition to demonstrating an earlier increase, a shorter time to peak of serum CK-MB and a lower estimated infarct size in the reperfusion group (p = 0.025 to 0.00001), the appearance rate constant (k1) and time from estimated initial increase to peak of CK-MB in the blood stream (tRP) were significantly different from those values in the no thrombolytic therapy group (p less than 00001). A cutoff level indicating reperfusion if k1 was greater than 0.185 or tRP was less than 16.5 hours demonstrated overlapping values between these two groups in only four patients (k1), two patients (tRP), and six patients with a combination.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary bypass surgery improves global and regional left ventricular function following thrombolytic therapy for acute myocardial infarction. TAMI Study Group

Coronary bypass surgery was performed prior to hospital discharge in 303 (22%) of 1387 consecutive patients enrolled in the TAMI 1 to 3 and 5 trials of intravenous thrombolytic therapy for acute myocardial infarction. Bypass surgery was of emergency nature (less than 24 hours from treatment with intravenous thrombolytic therapy) in 36 (2.6%) and was deferred (greater than 24 hours) in 267 (19.3%) patients. The indications for bypass surgery included failed angioplasty (12%); left main or equivalent coronary disease (9%); complex or multivessel coronary disease (62%); recurrent postinfarction angina (13%); and refractory pump dysfunction, mitral regurgitation, ventricular septal rupture or abnormal predischarge functional test (1% each). Although patients having bypass surgery were older (59.5 +/- 9.8 versus 56.0 +/- 10.2 years, (p less than 0.0001), had more extensive coronary artery disease (46% with three-vessel disease versus 11%, (p less than 0.0001), had more frequent diabetes mellitus (19% versus 15%, (p = 0.048), had more prior infarctions (p less than 0.0001), had more severe initial depression in global left ventricular ejection fraction (48.0 +/- 11.9% versus 51.8 +/- 11.9%, p = 0.0002), and regional infarct zone (-2.7 +/- 0.94 versus -2.5 +/- 1.1 SD/chord, p = 0.02) and noninfarct zone function (-0.36 +/- 1.8 versus 0.43 +/- 1.6 SD/chord, p less than 0.0001) than patients not having coronary bypass surgery, no difference in the incidence of death in hospital (7% surgical versus 6% nonsurgical) or death at long-term follow-up of hospital survivors (7% surgical versus 6% nonsurgical) was noted between groups. Surgical patients demonstrated a greater degree of recovery in left ventricular ejection fraction (3.4 +/- 9.8% versus 0.16 +/- 8.5%, p = 0.036) and infarct zone regional function (0.71 +/- 1.1 versus 0.34 +/- 0.99 SD/chord, p = 0.001) when immediate (90 minutes following initiation of thrombolytic therapy) and predischarge (7 to 14 days after treatment) contrast left ventriculograms were compared than did patients who received only intravenous thrombolytic therapy with or without coronary angioplasty. These data suggest a beneficial influence of coronary bypass surgery on left ventricular function and possibly on the clinical outcome of patients initially treated with intravenous thrombolytic therapy for acute myocardial infarction.

Comparison of the effects of streptokinase and tissue plasminogen activator on regional wall motion after first myocardial infarction: analysis by the centerline method with correction for area at risk

In a trial of streptokinase versus recombinant tissue-type plasminogen activator (rt-PA) for a first myocardial infarction, 270 patients were randomized. Regional left ventricular function was assessed in 214 patients at 3 weeks. The infarct-related artery was the left anterior descending artery in 78 patients, the right coronary artery in 122 and a dominant left circumflex artery in 14. Analysis was by the centerline method with a novel correction for the area of myocardium at risk, whereby the search region was determined by the anatomic distribution of the infarct-related artery. Infarct-artery patency at 3 weeks was 73% in the streptokinase group and 71% in the rt-PA group. Global left ventricular function did not differ between the two groups. Mean chord motion (+/- SD) in the most hypokinetic half of the defined search region was similar in the streptokinase and rt-PA groups (-2.4 +/- 1.5 versus -2.3 +/- 1.3, p = 0.63). There were no differences in hyperkinesia of the noninfarct zone. Compared with conventional centerline analysis, regional wall motion in the defined area at risk was significantly more abnormal. The two methods correlated strongly, however (r = 0.99, p less than 0.0001), and both methods produced similar overall results. Patients with a patent infarct-related artery and those with an occluded artery at the time of catheterization had similar levels of global function (ejection fraction 58 +/- 12% versus 57 +/- 12%, p = 0.58).(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular remodeling after acute myocardial infarction: clinical course and beneficial effects of angiotensin-converting enzyme inhibition

LV enlargement is an important determinant of survival after AMI. Pathophysiologic mechanisms leading to LV dilatation after an AMI include early thinning and stretching of the infarcted segment (e.g., infarct expansion) and hypertrophy of the noninfarcted myocardium. Such LV dilatation may adversely affect subsequent cardiac function, leading to heart failure and death. Experimental data in animals and preliminary studies in humans have demonstrated that early administration of captopril, an angiotensin-converting enzyme inhibitor, may limit infarct expansion and will attenuate progressive LV dilatation. This article discussed the clinical importance of the dilated left ventricle and reviewed advances and ongoing research in the use of angiotensin-converting enzyme inhibitors in the chronic phase after AMI.

Late streptokinase infusion and antithrombotic treatment in myocardial infarction reduce subsequent myocardial ischemia

Of 255 consecutive patients with acute myocardial infarction, 111 were eligible for attempted late thrombolysis. They were randomly assigned to either thrombolytic and antithrombotic treatment (treatment group) or routine treatment (control group). Patients in the treatment group received streptokinase initiated late (mean 32 hours; range 12 to 49) after the onset of symptoms, followed by heparin infusion for at least 5 days and warfarin and dipyridamole for at least 3 months. Patients were examined clinically and by bicycle ergometry on discharge from the hospital and after 3 and 12 months. The two groups did not differ with respect to deaths or reinfarctions. There was a trend toward a lower incidence of angina pectoris in the treatment group. Exercise tolerance in this group was significantly higher than in the control group (at 3 months 124 +/- 39 W vs 107 +/- 41 W; p less than 0.05). The difference was entirely accounted for by patients with no previous history of infarction or angina pectoris (at 3 months 142 +/- 37 W vs 112 +/- 45 W; p = 0.01). ECG signs of myocardial ischemia, silent or symptomatic, occurred at significantly lower levels of exercise among patients in the control group compared with patients in the treatment group. The results support the notion that thrombolytic therapy given as late as 12 to 49 hours after the onset of symptoms may reduce the incidence of residual ischemia during the postinfarction period.

Factors determining improvement in left ventricular function after reperfusion therapy for acute myocardial infarction: primacy of baseline ejection fraction

Improvement in left ventricular ejection fraction is a measure of salvage of ischemic myocardium after reperfusion therapy for acute myocardial infarction. The degree of improvement in left ventricular ejection fraction may be influenced by many factors. Therefore, 137 patients in whom paired radionuclide angiograms were obtained within 24 h of acute infarction and before hospital discharge were retrospectively evaluated to determine which factors most affect improvement in ejection fraction. Only baseline ejection fraction correlated significantly with improvement in ejection fraction by both univariate analysis (ejection fraction as a continuous variable; p less than 0.001; ejection fraction as a categorical variable, less than or equal to 45% versus greater than 45%, p less than 0.0001) and multivariate analysis (p less than 0.0001). Reperfusion status (patent versus occluded infarct artery) and extent of coronary artery disease (one, two or three vessel) were significant factors by multivariate but not by univariate analysis. Location of infarction, treatment modality and time to treatment did not correlate with change in ejection fraction by either statistical technique. Thus, of those factors tested, baseline left ventricular ejection fraction is the most potent predictor of improvement in ventricular function after acute infarction. Knowledge of baseline ejection fraction may be helpful in deciding whether to treat some patients with equivocal indications or contraindications for reperfusion therapy. Clinical trials of reperfusion strategies should stratify patients on the basis of baseline ejection fraction if ejection fraction is to be used as an end point for myocardial salvage.

Left ventricular ejection fraction may not be useful as an end point of thrombolytic therapy comparative trials

In the era of comparative and adjunctive trials in reperfusion therapy, the need to develop alternative end points for mortality reduction is clear. Left ventricular ejection fraction, which has been commonly used as a surrogate, is problematic due to missing values, technically inadequate studies, and lack of correlation with mortality results in controlled reperfusion trials performed to date. In this paper, we present a composite clinical end point that includes, in order, severity of adverse outcome death, hemorrhagic stroke, nonhemorrhagic stroke, poor ejection fraction (less than 30%), reinfarction, heart failure, and pulmonary edema. Such a composite index may be useful to detect true therapeutic benefit in reperfusion trials without necessitating greater than 20-30,000 patient enrollment.

Fate of patients with acute myocardial infarction with patency of the infarct-related vessel achieved with successful thrombolysis versus rescue angioplasty

Patients with failure of infarct-related artery recanalization after thrombolytic therapy have a poor clinical outcome. These patients have been considered for rescue angioplasty 90 min after thrombolytic therapy at the time of emergency catheterization in the course of five Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) trials. The outcome of 776 patients with patent infarct-related vessels after emergency catheterization was analyzed--607 with thrombolysis-mediated patency of the infarct-related vessel and 169 with patency achieved by angioplasty. Baseline characteristics of the thrombolysis and angioplasty patency groups were similar except for a higher acute left ventricular ejection fraction (51.3% versus 48.2%) in the thrombolysis group (p = 0.003). Seven to 10 day left ventricular ejection fraction was higher (52.3% versus 48.1%), infarct zone functional recovery was greater (0.44 versus 0.21 standard deviation/chord, or 18% versus 7%, p = 0.001) and reocclusion was less (11% versus 21%) in the thrombolysis compared with the angioplasty group. Despite these differences, angioplasty patency was associated with the same low in-hospital mortality rate (5.9% versus 4.6%) and long-term mortality rate (3% versus 2%) as thrombolysis patency. Reocclusion adversely affected the mortality rate and ventricular functional recovery. Technical failure of rescue angioplasty was associated with a much higher mortality rate than was technical success (39.1% versus 5.9%). Thrombolysis patency was preferable to angioplasty patency after thrombolytic therapy in acute myocardial infarction, but both were associated with the same low in-hospital and long-term mortality rates, suggesting that rescue angioplasty is beneficial in some patients with failure of infarct-related artery recanalization after thrombolytic therapy.

Ventricular remodeling after myocardial infarction. Experimental observations and clinical implications

An acute myocardial infarction, particularly one that is large and transmural, can produce alterations in the topography of both the infarcted and noninfarcted regions of the ventricle. This remodeling can importantly affect the function of the ventricle and the prognosis for survival. In the early period, infarct expansion has been recognized by echocardiography as a lengthening of the noncontractile region. The noninfarcted region also undergoes an important lengthening that is consistent with a secondary volume-overload hypertrophy and that can be progressive. The extent of ventricular enlargement after infarction is related to the magnitude of the initial damage to the myocardium and, although an increase in cavity size tends to restore stroke volume despite a persistently depressed ejection fraction, ventricular dilation has been associated with a reduction in survival. The process of ventricular enlargement can be influenced by three interdependent factors, that is, infarct size, infarct healing, and ventricular wall stresses. A most effective way to prevent or minimize the increase in ventricular size after infarction and the consequent adverse effect on prognosis is to limit the initial insult. Acute reperfusion therapy has been consistently shown to result in a reduction in ventricular volume. The reestablishment of blood flow to the infarcted region, even beyond the time frame for myocyte salvage, has beneficial effects in attenuating ventricular enlargement. The process of scarification can be interfered with during the acute infarct period by the administration of glucocorticosteroids and nonsteroidal antiinflammatory agents, which result in thinner infarcts and greater degrees of infarct expansion. Modification of distending or deforming forces can importantly influence ventricular enlargement. Even short-term augmentations in afterload have deleterious long-term effects on ventricular topography. Conversely, judicious use of nitroglycerin seems to be associated with an attenuation of infarct expansion and long-term improvement in clinical outcome. Long-term therapy with an angiotensin converting enzyme inhibitor can favorably alter the loading conditions on the left ventricle and reduce progressive ventricular enlargement as demonstrated in both experimental and clinical studies. With the former therapy, this attenuation of ventricular enlargement was associated with a prolongation in survival. The long-term clinical consequences of long-term angiotensin converting enzyme inhibitor therapy after myocardial infarction is currently being evaluated. Although studies directed at attenuating left ventricular remodeling after infarction are in the early stages, it does seem that this will be an important area in which future research might improve long-term outcome after infarction.