Influence of thrombolytic treatment followed by full dose anticoagulation on the frequency of left ventricular thrombi in acute myocardial infarction

The Role of Echocardiography in Acute Myocardial Infarction

The indications for echocardiography in the setting of acute myocardial infarction are to identify wall motion abnormalities, to evaluate left and right ventricular function, and to exclude complications such as pericarditis, mitral regurgitation, and ventricular rupture. Doppler echocardiography can provide important hemodynamic information. In the near future, contrast echocardiography can be expected to delineate myocardial perfusion and three-dimensional echocardiography to better define infarct size.

Risk factors for development of left ventricular thrombus after first acute anterior myocardial infarction-association with anticardiolipin antibodies

Background

Left ventricular thrombus(LVT] formation is a frequent complication in patients with acute anterior myocardial infarction(MI). LVT is associated with increased risk of embolism and higher mortality rates after acute MI. Anticardiolipin antibodies (ACA) are immunoglobulins that react with phospholipid-binding proteins interfering with the prothrombin activator complex. The effects of phospholipids on pathophysiology of cardiovascular thrombotic events are well known. In this study, we aimed to evaluate the importance of clinical and biochemical parameters including anticardiolipin antibodies on left ventricular thrombus formation after acute anterior MI.

Methods and Results

Seventy patients with a first anterior AMI were prospectively and consecutively enrolled. Patients with previous MI, autoimmune disease, collagen vascular disease and arterial or venous thrombosis history were excluded from this study. At the time of hospitalization, key demographic and clinical characteristics were collected including age, gender, ethanol intake and presence of traditional risk factors for atherosclerosis (hypertension, diabetes, smoking, hyperlipidemia, positive family history). Patients were evaluated for echocardiographic data, blood chemistry and ACA. Two-dimensional and Doppler echocardiographic examinations were performed in all patients within the first week and at 14 days after MI. LV thrombus was detected in 30 (42.8%) patients. ACA IgM levels were significantly higher in the patient group with LV thrombus than in the group without thrombus (12.44 ±4.12 vs. 7.69 ± 4.25 mpl, p = 0,01). ACA IgG levels were also found higher in the group with LV thrombus (24.2 ± 7.5 vs.17.98 ± 6.45 gpl, p = 0.02). Multivariate analyses revealed diabetes mellitus, higher WMSI, lower MDT and higher ACA IgM and higher ACA IgG levels as independent predictors of left ventricular thrombus formation.

Conclusions

Our data demonstrate that beside the low ejection fraction, lower MDT and higher wall motion score index, modestly elevated ACA IgM and ACA IgG levels are associated with LV thrombus formation in patients with anterior MI.

Influence of thrombolytic therapy on the incidence of left ventricular thrombi after acute anterior myocardial infarction: role of successful reperfusion

BACKGROUND

Previous studies have reported controversial results regarding the effectiveness of systemic thrombolysis in preventing left ventricular (LV) thrombus after acute myocardial infarction (MI).

HYPOTHESIS

This study was performed to evaluate the influences of thrombolysis, and particularly successful reperfusion, on the incidence of LV thrombus formation after acute anterior MI.

METHODS

In all, 191 patients suffering from a first attack of acute anterior MI were prospectively evaluated by two-dimensional echocardiography and coronary angiography, performed at the end of the first week and within the first two weeks of MI, respectively. Of these, 98 who presented within 12 h of onset of symptoms received intravenous streptokinase (1.5 million IU), while the remaining 93 patients who, either because of contraindications or late admission, did not receive thrombolytic treatment served as control group. All patients received aspirin and full-dose anticoagulation with intravenous heparin. Successful reperfusion in the streptokinase group was assessed by enzymatic and electrocardiographic evidence.

RESULTS

The overall incidence of LV thrombi was 24.6% (47/191). When all patients were evaluated, no statistically significant difference was found between the frequency of LV thrombi in the patients who had thrombolysis (22.4%) and those who did not (26.8%), despite a trend toward the formation of fewer thrombi in the initial group (p > 0.05). However, the patients who had successful reperfusion with streptokinase (n = 64) had significantly reduced incidence of LV thrombi compared with those who did not receive thrombolytic therapy (20 vs. 26.8%, p < 0.05). Stepwise multivariate analysis suggested that LV abnormal wall motion score (p = 0.01) and presence of LV aneurysm were independent predictors of LV thrombus formation in patients with acute anterior MI.

CONCLUSION

Not all patients who received streptokinase for acute anterior MI, but only those with successful reperfusion had reduced incidence of LV thrombi. The favorable effects of thrombolysis on LV thrombus formation are probably due to the preservation of global LV systolic function.

Relation between early mitral regurgitation and left ventricular thrombus formation after acute myocardial infarction: results of the GISSI-3 echo substudy

OBJECTIVE

To evaluate the prevalence and correlates of left ventricular thrombosis in patients with acute myocardial infarction, and whether the occurrence of early mitral regurgitation has a protective effect against the formation of left ventricular thrombus.

DESIGN AND SETTING

Multicentre clinical trial carried out in 47 Italian coronary care units.

PATIENTS AND METHODS

757 patients from the GISSI-3 echo substudy population with their first acute myocardial infarct were studied by echocardiography at 24-48 hours from symptom onset (S1), at discharge (S2), at six weeks (S3), and at six months (S4). The diagnosis of left ventricular thrombosis was based on the detection of an echo dense mass with defined margins visible throughout the cardiac cycle in at least two orthogonal views.

RESULTS

In 64 patients (8%), left ventricular thrombosis was detected in one or more examinations. Compared with the remaining 693 patients, subjects with left ventricular thrombosis were older (mean (SD) age: 64.6 (13.0) v 59.8 (11.7) years, p < 0.005), and had larger infarcts (extent of wall motion asynergy: 40.9 (11.5)% v 24.9 (14)%, p < 0.001), greater depression of left ventricular ejection fraction at S1 (43.3 (6.9)% v 48.1 (6.8)%, p < 0.001), and greater left ventricular volumes at S1 (end diastolic volume: 87 (22) v 78 (18) ml/m(2), p < 0.001; end systolic volume: 50 (17) v 41 (14) ml/m(2), p < 0.001). The prevalence of moderate to severe mitral regurgitation on colour Doppler at S1 was greater in patients who had left ventricular thrombosis at any time (10.2% v 4.2%, p < 0.05). On stepwise multiple logistic regression analysis the only independent variables related to the presence of left ventricular thrombosis were the extent of wall motion asynergy and anterior site of infarction.

CONCLUSIONS

Left ventricular thrombosis is not reduced, and may even be increased, by early moderate to severe mitral regurgitation after acute myocardial infarction. The only independent determinant of left ventricular thrombosis is the extent of the akinetic-dyskinetic area detected on echocardiography between 24-48 hours from symptom onset.

Role of echocardiography in the assessment of left ventricular thrombus embolic potential after anterior acute myocardial infarction

The contribution of cardiac ultrasound in assessment of the embolic potential of left ventricular thrombi after anterior acute myocardial infarction was verified in a prospective study of serial echocardiograms (mean, 18.9 examinations per patient) obtained over a long-term period (1-72 months; mean, 38±12). The study population comprised 222 patients (162 men; age, 64±11 years) with a first anterior acute myocardial infarction, treated with thrombolysis (group A) or receiving no antithrombolic therapy (group B). Embolism occurred in a total of 12 patients (11 with a left ventricular thrombus; p<0.005) and was more frequent in group B (10 patients; p<0.04). Predictors of embolism were the absence of thrombolysis, detection of a left ventricular thrombus, protrusion or mobility of the thrombus, and morphologic changes in the thrombus over time. Patients in group A had a lower incidence of each of these predictors, and a higher thrombus resolution rate. An appropriate echocardiographic protocol is crucial to assessment of the embolic potential of left ventricular thrombi after anterior acute myocardial infarction and may help to identify candidates for aggressive antithrombotic therapy (c)2001 CHF, Inc.

Doppler-derived mitral deceleration time as an early predictor of left ventricular thrombus after first anterior acute myocardial infarction

BACKGROUND

The relation between left ventricular (LV) diastolic function and LV thrombus has not yet been fully investigated. The aim of this study was to determine whether early assessment of Doppler-derived mitral deceleration time (DT), a measure of LV compliance and filling, may predict LV thrombus formation after acute myocardial infarction.

METHODS AND RESULTS

Two-dimensional and Doppler echocardiographic examinations were performed in 98 consecutive patients (aged 57 +/- 12 years; 8 women) with first acute myocardial infarction. The patients were studied within 24 hours and at days 3, 7, 15, and 30 after arrival to the coronary care unit. Mitral flow velocities were obtained from the apical 4-chamber view with pulsed Doppler. LV thrombus was detected in 20 of 98 patients. Patients were divided into 2 groups according to LV thrombus formation: group 1 (n = 20) with thrombus and group 2 (n = 78) without thrombus. Mitral E-wave DT was significantly shorter in group 1 than group 2 (134 ms vs 175 ms; P <.001). Patients in group 1 had significantly larger LV end-diastolic and end-systolic volumes and a higher wall motion score index than patients in group 2 (133 +/- 39 mL vs 112 +/- 41 mL, P =.03; 83 +/- 34 mL vs 59 +/- 30 mL, P =.003; and 1.8 +/- 0.3 mL vs 1.5 +/- 0.3 mL, P =.007, respectively). The LV ejection fraction was significantly lower in group 1 than in group 2 (39% +/- 13% vs 48% +/- 12%; P =.004). In a multivariate regression analysis, mitral E-wave DT was identified as an independent variable related to development of LV thrombus (P =.04).

CONCLUSIONS

Doppler-derived mitral DT is superior to conventional clinical and 2-dimensional echocardiographic assessment in estimating the risk of left ventricular thrombosis after myocardial infarction.

Prevalence of early left ventricular thrombus after primary coronary intervention for acute myocardial infarction

The prevalence of left ventricular (LV) thrombus after acute myocardial infarction (AMI) has been reported high at 20-60%. Current reperfusion therapies such as thrombolysis have shown a trend toward reducing the incidence of LV thrombosis. However, the prevalence of LV thrombus after primary percutaneous coronary intervention (PCI) for AMI has not been systematically studied. At Massachusetts General Hospital 71 consecutive patients who underwent primary PCI for acute ST elevation MI were reviewed for the prevalence of LV thrombus evaluated by echocardiography. Echocardiography was performed within 5 days of infarction. PCI was successful in all patients. The time delay from symptom onset to intervention was 191 minutes. Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow was achieved in more than 80% of cases. Only 3 patients (4%) had echocardiographic evidence of LV thrombus. All 3 patients had anterior infarctions. The incidence among patients with anterior MI was 10% (3 of 30 patients). The prevalence of LV thrombus in patients treated with primary PCI for AMI is low (4%).

Predischarge two-dimensional echocardiographic evaluation of left ventricular thrombosis after acute myocardial infarction in the GISSI-3 study

Left ventricular (LV) thrombosis can be found in patients with acute myocardial infarction (AMI). No wide multicenter trial on AMI has provided information about LV thrombosis until now. The protocol of the GISSI-3 study included the search for the presence of LV thrombosis in patients from 200 coronary care units that did not specifically focus on LV thrombosis. We examined the GISSI-3 database results related to 8,326 patients at low to medium risk for LV thrombi in which a predischarge echocardiogram (9 +/- 5 days) was available. LV thrombosis was found in 427 patients (5.1%): 292 of 2,544 patients (11.5%) with anterior AMI and in 135 of 5,782 patients (2.3%) with AMI in other sites (p <0.0001). The incidence of LV thrombosis was higher in patients with ejection fraction < or = 40% (151 of 1,432 [10.5%] vs 276 of 6,894 [4%]; p <0.0001) both in the total population and in the subgroup with anterior AMI (106 of 597 [17.8%] vs 186 of 1,947 [9.6%]; p <0.0001). Multivariate analysis showed that only the Killip class > I and early intravenous beta-blocker administration were independently associated with higher LV thrombosis risk in the subgroup of patients with anterior AMI (odds ratio 1.75, 95% confidence interval 1.28 to 2.39; odds ratio 1.32, 95% confidence interval 1.02 to 1.72, respectively). In patients with anterior AMI, oral beta-blocker therapy given or not given after early intravenous beta-blocker administration does not influence the occurrence of LV thrombosis. The rate of LV thrombosis was similar in patients treated or not treated with nitrates and lisinopril both in the total population and in patients with anterior and nonanterior AMI. In conclusion, in the GISSI-3 population at low to medium risk for LV thrombi, the highest rate of occurrence of LV thrombosis was found among patients with anterior AMI and an ejection fraction < 40%. Killip class > I and the early intravenous beta-blocker administration were the only variables independently associated with a higher predischarge incidence of LV thrombosis after anterior AMI.

Incidence and natural history of left ventricular thrombus following anterior wall acute myocardial infarction

Previous studies have reported left ventricular (LV) thrombus in 20% to 56% of patients after anterior wall acute myocardial infarction (AMI). The Healing and Early Afterload Reducing Therapy (HEART) study was a prospective study comparing effects of early (24 hours) or delayed (14 days) initiation of ramipril, an angiotensin-converting enzyme inhibitor, on LV function after anterior wall AMI. This ancillary study assessed prevalence of LV thrombus. Two-dimensional echocardiography was performed on days 1, 14, and 90 after myocardial infarction. The cohort consisted of 309 patients. Q-wave anterior wall AMI occurred in 78%; 87% received reperfusion therapy. The prevalence of LV thrombus was 2 of 309 (0.6%) at day 1, 11 of 295 (3.7%) at day 14, and 7 of 283 (2.5%) at day 90. One patient had thrombus at 2 examinations. The day 1 echocardiogram was not correlated with thrombus development. LV size increased more in patients with thrombus than in those without thrombus. Patients with thrombus had more wall motion abnormality after day 1 than patients without thrombus (p = 0.03). Thus, the current prevalence of LV thrombus in anterior wall AMI is lower than previously reported, possibly due to changes in AMI management. Preservation of LV function is likely to be an important mechanism. Most thrombi are seen by 2 weeks after AMI. Resolution documented by echocardiography is frequent.

Left ventricular thrombosis after anterior myocardial infarction with and without thrombolytic treatment

OBJECTIVES

To examine the incidence of left ventricular thrombus in patients with anterior myocardial infarction, with and without streptokinase treatment. To identify predictors of thrombus development.

DESIGN

Consecutive patients prospectively studied during the hospitalized period. Echocardiography was performed within 3 days of admission and before discharge.

SETTING

Umeå University Hospital, a teaching hospital in Northern Sweden.

SUBJECTS

Ninety-nine patients with anterior myocardial infarction of whom 74 were treated with streptokinase.

MAIN OUTCOME MEASURES

Left ventricular thrombus and left ventricular segmental myocardial function.

RESULTS

During the hospital stay, a thrombus developed in 46% (95% confidence interval [CI], 35-57%) of the patients in the thrombolysis group and in 40% (95% CI, 21-59%) of the patients in the non-thrombolysis group. No difference in left ventricular segmental myocardial function was found between the thrombolysis and non-thrombolysis groups at hospital discharge. No embolic events were observed. The occurrence of a left ventricular thrombus at hospital discharge was significantly associated with previous myocardial infarction, peak enzyme levels, left ventricular global and segmental dysfunction and an increased dose of peroral diuretics or use of parenteral diuretics. In a multiple logistic regression model, left ventricular segmental dysfunction was the most important predictor of left ventricular thrombus.

CONCLUSION

Thrombolytic treatment with streptokinase does not prevent the development of a left ventricular thrombus but the risk of embolic complications is low. The left ventricular segmental myocardial score can be used to assess the risk of thrombus development, also, after thrombolysis.

Relation between myocardial infarct location and stroke

OBJECTIVES

We sought to compare the likelihood of stroke in patients with anterior versus nonanterior myocardial infarction.

BACKGROUND

The association between anterior infarction and left ventricular thrombus has led to the assumption that embolization from thrombi is an important cause of stroke in patients with anterior infarction. We hypothesized that if anterior infarction is a cause of left ventricular thrombi, the number of strokes should be disproportionately higher in patients with anterior than nonanterior infarction.

METHODS

We performed a retrospective analysis of 2,466 patients randomized from day 3 to day 15 after infarction as part of a multicenter placebo-controlled study of diltiazem to prevent cardiac death or myocardial infarction. Any acute focal cerebral disorder resulting in localizing findings characterized as a stroke or transient ischemic attack was considered an event.

RESULTS

Of 91 events during a follow-up period of 12 to 52 months, 23 (3.2%) occurred in 724 patients with an anterior and 68 (3.9%) in 1,742 patients with a nonanterior myocardial infarction (relative risk 0.81; 95% confidence interval 0.51 to 1.30). Power analysis revealed that the negativity of the study was not the result of inadequate sample size. Life table analysis showed no difference in cumulative event rate (p = 0.42) according to site of infarction. Cox regression analysis showed that of 10 clinical covariates, only systolic blood pressure was predictive of stroke (p < 0.001). The use of warfarin did not contribute to the model. Finally, the addition of site of infarction (anterior vs. nonanterior) did not contribute significantly to the Cox model.

CONCLUSIONS

Although there is a significant incidence of stroke after acute myocardial infarction, there is no relation between the occurrence of stroke and site of infarction. These data do not support the presumed causal relation between anterior myocardial infarction, thrombus and stroke.

Embolic potential, prevention and management of mural thrombus complicating anterior myocardial infarction: a meta-analysis

OBJECTIVES

The management of mural thrombus complicating acute anterior myocardial infarction remains controversial in part because of the small size of studies on this topic. We performed a meta-analysis of published studies to address three questions: 1) What is the embolic risk of mural thrombi after myocardial infarction? 2) What is the impact of systemic anticoagulation in reducing the embolic risk of mural thrombi? 3) What is the impact of systemic anticoagulation, thrombolytic therapy and antiplatelet therapy in preventing mural thrombus formation?

METHODS

Studies were identified by a computerized and manual search and were included if they were published in manuscript form in the English-language literature. Pooling of data was performed by calculating the Mantel-Haenszel odds ratio and an event rate difference by the method of DerSimonian and Laird.

RESULTS

The odds ratio for increased risk of emboli in the presence of echocardiographically demonstrated mural thrombus (11 studies, 856 patients) was 5.45 (95% confidence interval [CI] 3.02 to 9.83), and the event rate difference was 0.09 (95% CI 0.03 to 0.14). The odds ratio of anticoagulation versus no anticoagulation in preventing embolization (seven studies, 270 patients) was 0.14 (95% CI 0.04 to 0.52) with an event rate difference of -0.33 (95% CI -0.50 to -0.16). The odds ratio of anticoagulation versus control in preventing mural thrombus formation (four studies, 307 patients) was 0.32 (95% CI 0.20 to 0.52), and the event rate difference was -0.19 (95% CI -0.09 to -0.28). The odds ratio for thrombolytic therapy in preventing mural thrombus (six studies, 390 patients) was 0.48 (95% CI 0.29 to 0.79) with an event rate difference of -0.16 (95% CI 0.10 to -0.42), whereas for antiplatelet agents (two studies, 112 patients) the odds ratio was 1.43 (95% CI 0.04 to 56.8) with an event rate difference of 0.16 (95% CI -0.20 to 0.52).

CONCLUSIONS

This analysis supports the hypotheses that 1) mural thrombus after myocardial infarction poses a significantly increased risk of embolization, 2) the risk of embolization is reduced by systemic anticoagulation, and 3) anticoagulation can prevent mural thrombus formation. Thrombolytic therapy may prevent mural thrombus formation, but evidence for a similar benefit of antiplatelet therapy is lacking.

Ischemic stroke and intracranial hemorrhage following thrombolytic therapy for acute myocardial infarction: a risk-benefit analysis

Stroke is a potentially serious complication of acute myocardial infarction (AMI). In the prethrombolytic era, most strokes were attributed to cerebral embolism. On the basis of available information, the occurrence of stroke in the thrombolytic era appears to be less than in the prethrombolytic era. In the thrombolytic era, the occurrence of various forms of intracranial hemorrhage has increasingly been documented in addition to cerebral embolism, with intriguing features. In general, however, the delineation of specific stroke subtypes has been imprecise and must take into account factors that are unique to this setting. Age is a risk factor for both ischemic and hemorrhagic stroke. Potential risk factors for intracranial hemorrhage include hypertension, dosage of fibrinolytic agents, and prior neurologic disease. Potential causes of intracranial hemorrhage include combined fibrinolytic/adjunctive therapies, various cerebrovascular lesions, and head trauma. Existing data suggest that mortality related to stroke complicating AMI is on the decline as well. More research is needed in order to quantify precisely the occurrence and proportions of stroke subtypes, risk factors, and causes in order to define mechanisms and preventive measures.

Effects of intravenous recombinant tissue-type plasminogen activator therapy on the incidence and associations of left ventricular thrombus in patients with a first acute Q wave anterior myocardial infarction

Consecutive survivors of a first Q wave anterior myocardial infarction were studied to observe the impact of recombinant tissue-type plasminogen activator (rt-PA) therapy on the incidence and associations of left ventricular thrombus. Fifty-four patients received rt-PA within 4 hours after the onset of cardiac pain, followed by heparin infusion. Forty-four patients who did not qualify for rt-PA therapy but who were anticoagulated with heparin served as a control group. Two-dimensional echocardiography was performed in all patients on days 3 and 7 to detect thrombi and analyze wall motion. Ejection fraction was determined by radionuclide angiography in all patients on day 7. Apical thrombi were detected on day 3 in three patients (5.5%) who received rt-PA and in eight control patients (18%) (p less than 0.05). All patients with a thrombus had apical dyskinesis and 8 of 11 (73%) had an aneurysm. Of the 87 patients without thrombosis, apical dyskinesis and aneurysm were present in 42 (48%) and 11 (13%) patients, respectively (p less than 0.01). Ejection fractions and wall motion scores of patients without a thrombus were significantly better when compared with data from those with a thrombus. There were fewer patients with apical dyskinesis (17 of 54) in the group receiving rt-PA therapy compared with the control group (36 of 44) (p less than 0.01). Ejection fractions and wall motion scores were better in patients who received rt-PA compared with control subjects (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular thrombus in anterior acute myocardial infarction after thrombolysis. A GISSI-2 connected study

BACKGROUND

Streptokinase reduces the incidence of left ventricular thrombosis after acute myocardial infarction. However, it is unknown whether a similar effect can be obtained with different thrombolytic agents and whether subcutaneous calcium heparin can have an additional efficacy.

METHODS AND RESULTS

To compare the effects of two different thrombolytic agents combined or not with heparin on the incidence and features of left ventricular thrombi and their related embolic events, we performed a GISSI-2 ancillary echocardiographic study (the first echocardiogram obtained within 48 hours of symptoms onset and the second before hospital discharge) that enrolled 180 consecutive patients (mean age, 63 +/- 11 years, 142 men) with a first anterior acute myocardial infarction. Patients were randomized into four groups of treatment: recombinant tissue-type plasminogen activator (rt-PA) (n = 47), rt-PA plus heparin (n = 45), streptokinase (n = 39), and streptokinase plus heparin (n = 49). Left ventricular thrombosis was observed in 51 of 180 patients (28%). No significant differences were found concerning the incidence of thrombi in the four treatment groups. Mural shape of left ventricular thrombi was found more frequently than the protruding shape (71% versus 29% at the first examination, 64% versus 36% at the second), particularly in heparin-treated patients (93% versus 7% at first examination, 70% versus 30% at the second). Only one embolic event (0.5%) occurred during the hospitalization.

CONCLUSIONS

We conclude that 1) the rate of left ventricular thrombi does not differ in patients with acute myocardial infarction treated either with streptokinase or rt-PA, 2) subcutaneous heparin, when begun 12 hours after intravenous thrombolysis, does not appear to further reduce the occurrence of thrombi but seems to influence the shape of left ventricular thrombi, and 3) during the predischarge period, embolic events are rare in patients treated by thrombolysis.

Regression of intracardiac thrombus after embolic stroke

Using two-dimensional echocardiography, we studied the pathophysiology of intracardiac thrombus regression accompanied by anticoagulant therapy in 82 consecutive patients with acute cardiogenic cerebral embolism. We noted intracardiac thrombus in 15 patients; nine of the 15 were started on anticoagulant therapy with warfarin potassium to maintain the prothrombin time between 2.5 and 3.5 (international normalized ratio). Serial two-dimensional echocardiograms were obtained for these nine patients before and after anticoagulation, with the plasma levels of fibrinopeptide A, fibrinopeptide B beta 15-42, and D-dimer measured at the same time. In eight of the nine patients the intracardiac thrombi gradually decreased in size while the plasma level of fibrinopeptide A fell to within the normal range and the plasma levels of fibrinopeptide B beta 15-42 and D-dimer remained above the normal ranges. In the other patient the thrombus disappeared, with embolization to the right arm immediately after starting anticoagulant therapy. Mobile or small thrombi regressed earlier than nonmobile or large ones. We conclude that regression of intracardiac thrombi after anticoagulation may be based on the relative predominance of plasma fibrinolytic activity over anticoagulation-inhibited thrombin activity.