The Occluded Artery Trial - TOAT

Description:

The Open Artery Tial was a randomized trial comparing conservative therapy to late recanalization of the infarct related artery after acute myocardial infarction

Hypothesis:

Late reperfusion of the infarct realted artery would have a beneficial effect on left ventricular remodeling after acute anterior wall myocardial infarction.

Study Design

Study Design:

Patients Screened: 223
Patients Enrolled: 66
Mean Follow Up: 12 months
Mean Patient Age: 18-75 years. Mean 58 years
Female: 20%
Mean Ejection Fraction: 13-31%

Patient Populations:

1) Acute anterior wall myocardial infarction without post-infarction angina 2) Ejection fraction <50% or >3 pathological Q waves in the precordial ECG leads 3) Absence of chest pain, ECG change or hemodynamic disturbance during modified Bruce treadmill test 4) Coronary angiography performed between 3 days and 4 weeks of anterior wall myocardial infarction demonstrating an occluded LAD coronary artery (TIMI 0 or 1 flow) and <50% stenosis in the other epicardial coronary arteries

Exclusions:

1) Non sinus rhythm 2) Bundle branch block 3) Age <18 or >75 years 4) NYHA class III or IV heart failure. 5) Clinical indication for revascularization such as chest pain or significant stress-induced ischemia; 6) Prior coronary bypass surgery 7) Dilated non-ischemic cardiomyopathy 8) Severe renal disease with a creatinine > 2.5 9) Chronic occlusion of the infarct related artery 10)Infarct artery too small for percutaneous revascularization

Secondary Endpoints:

1) Exercise tolerance 2) Quality of life 3) Combined death, reinfarction and repeat revascularization

Drug/Procedures Used:

Percutaneous coronary intevention with stent placement and conventional medical therapy (open artery) OR conventional medical therapy alone (closed artery). Echocardiography was performed at 6 weeks, three months and 12 months after myocardial infarction and repeat coronary angiography was performed at 12 months.

Concomitant Medications:

Conventional medical management including aspirin, beta-blockers, ACE inhibitors, lipid-lowering agents

Principal Findings:

Percutaneous coronary intervention was successful in 94% of open artery patients. Follow-up angiography revealed that reocclusion occurred in 11% and restenosis (>50% diameter stenosis) in 19% of open artery patients. Spontaneous recanalization occurred in 19% of patients treated with medical therapy alone. Left ventricular end systolic, end diastolic and ejection fractions were similar in the two groups. At 12 months, the left ventricular end systolic volume increased over time in the open artery group (p<0.01), and this increase was greater than in the closed artery group (p<0.01). At the end of the follow-up period, exercise duration and self-reported functional impairment was less in the open artery group. During follow-up, clinical events were more frequent in the open artery group (17) compared to the closed artery group (12; p<0.05). These events were predominantly due to repeat revascularization for: stent occlusion and reinfarction (3), restenosis (2), arrhythmia (1) and progressive heart failure (1).

Interpretation:

Among asymptomatic patients, recanalization of occluded infarct-related arteries 1 month post AMI was associated with an adverse effect on remodeling but tended to increase exercise tolerance and improve quality of life. There are some trial data to suggest that there are benefits of opening an occluded artery late, that are independent of myocardial salvage such as favorably improving LV remodeling. Despite this postulated benefit, remodeling was worse in the present study and also in the TAMI 6 study, where end systolic volume increased by 9% in the interventional group and decreased by 13% in the conservative group. Other groups have shown that a favorable impact on LV remodeling may be time dependent with benefits observed if the PCI is undertaken within 2 to 3 weeks, but not after that. One-third of patients in the present study underwent PCI between 3 and 7 days of MI, while in another one-third it was between 36 and 42 days. The LV ESV changes between 6 weeks and 12 months of MI in the two sub-groups, however, were similar. Thus, in the present study, neither the direction nor the amplitude of the changes in LV ESV was dependent on the timing of PCI was directly related to the interventional procedure, and the other two occurred six and eight weeks after intervention. In the setting of an occluded infarct vessel, distal ischemic myocardium is often supported by collateral vessels. After intervention, collateral vessels may become embolized, and this may be one mechanism contributing to the documented and rapid regression of recruitable collateral support after PCI for total occlusions. Interestingly, the 2 patients who had their arteries open who went on to have an MI had loss of collaterals at the time of the second angiogram. Neither GP IIB/IIIA inhibitors nor distal protection devices were used in this study and whether they may have improved distal perfusion is not known. A large, prospective trial of late intervention, the open artery trial (OAT) is underway and should help answer these question more definitively in a larger number of patients.

References:

Yousef ZR, Redwodd SR, Bucknall CA. Late Intervention After Anterior Myocardial Infarction: Effects on Left Ventricular Size, Function, Quality of Life, and Exercise Tolerance. J Am Coll Cardiol 2002;40:869–76.

Clinical Topics: Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Atherosclerotic Disease (CAD/PAD), Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Interventions and Coronary Artery Disease, Interventions and Imaging, Angiography, Echocardiography/Ultrasound, Nuclear Imaging

Keywords: Exercise Tolerance, Coronary Artery Disease, Follow-Up Studies, Platelet Aggregation Inhibitors, Electrocardiography, Constriction, Pathologic, Anterior Wall Myocardial Infarction, Platelet Membrane Glycoprotein IIb, Stents, Percutaneous Coronary Intervention, Lisinopril, Coronary Angiography, Quality of Life, Chest Pain, Ventricular Remodeling, Heart Failure, Stroke Volume, Echocardiography, Exercise Test


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