Effect of infarct size measured from antimyosin single-photon emission computed tomographic scans on left ventricular remodeling

Genetic basis of left ventricular remodeling after myocardial infarction

The purpose of the present study was to assess whether the insertion (I)/deletion (D) polymorphism of the angiotensin converting enzyme (ACE) gene, and the polymorphism of angiotensinogen (AGT) gene with threonine (T) instead of methionine (M) at amino acid 235 in exon 2 (M235T) were associated with left ventricular dilatation after myocardial infarction. In 103 patients with myocardial infarction, the left ventricular (LV) end-diastolic volume index (EDVI) and the end-systolic volume index (ESVI) were assessed by echocardiography at two time points, namely at 7 +/- 4 days and at 3.9 +/- 1.3 months (mean +/- S.D.) after the infarction. The increases in the LVEDVI and LVESVI on the second echocardiogram were significantly higher in subjects with the DD and ID genotypes than in patients with the II genotype (P < 0.05 and P < 0.005, respectively). Multiple regression analysis revealed that the LVESVI at the first echocardiographic examination and the ACE I/D genotype were significant predictors of the LVEDVI and LVESVI at the second echocardiographic examination. However, the AGT M235T genotype was eliminated. In conclusion, the DD and ID genotypes of the ACE gene were significantly associated with the progression of the LVEDVI and LVESVI after myocardial infarction. The presence of the deletion allele of the ACE gene may be a risk factor of congestive heart failure after a myocardial infarction.

Determinants of left ventricular function two weeks and one year after an acute myocardial infarction

This study examines possible covariates of left ventricular function two weeks and sixteen months after an acute infarction. It was performed in a group of 312 patients randomized double blindly to recombinant tissue plasminogen activator (rt-PA) (n = 156) or placebo treatment and followed thereafter for at least one year. Two weeks after the infarction, enzymatic infarct size, infarct-related vessel, and number of diseased coronary arteries were significant determinants of the infarct-related regional wall motion (centerline method) (R2 = 0.25 to 0.60, P = 0.0001). Enzymatic infarct size, regional wall motion of both infarct-related and remote areas, reinfarction, and treatment allocation were significant independent correlates of ejection fraction (R2 = 0.76), end-diastolic volume (R2 = 0.20), and end-systolic volume (R2 = 0.69, P < 0.0001). Infarct-related coronary artery and predischarge end-systolic volume were significant independent covariates of ejection fraction at rest (R2 = 0.47) after sixteen months. Age, enzymatic infarct size, and predischarge end-diastolic volume were independent determinants of the maximal (R2 = 0.49, P < 0.0001) and peak exercise ejection fraction (R2 = 0.49, P < 0.0001).

Effects of early administration of enalapril on radionuclide left ventricular ejection fraction and plasma N-terminal atrial natriuretic peptide after acute myocardial infarction

The effects of enalapril therapy on radionuclide ejection fraction and plasma N-terminal atrial natriuretic peptide were investigated in a randomized, double-blind, placebo-controlled study of 52 patients with acute myocardial infarction. The medication was begun intravenously within 24 hours of the onset of symptoms. At discharge and the end point of 6 months, the radiographic size of the heart was significantly smaller in patients receiving (n = 28) than in those not receiving (n = 24) enalapril therapy (p < 0.03 vs < 0.01). However, left ventricular ejection fraction decreased simultaneously from 50 +/- 10% to 47 +/- 11% in patients treated with enalapril, whereas it increased from 48 +/- 13% to 50 +/- 14% in control patients (p < 0.05 for the difference of the changes). The decrease in ejection fraction was most marked in the infarct-related region of the left ventricle (p < 0.01). During the in-hospital period, plasma N-terminal atrial natriuretic peptide was decreased in patients treated with enalapril, whereas it was increased in those treated with placebo with complicated acute myocardial infarction (p < 0.05). During the following 6 months, the differences remained insignificant. Early administration of enalapril significantly attenuated heart enlargement after myocardial infarction and probably improved hemodynamics during the acute phase of complicated infarction. The decrease in ejection fraction during recovery indicates an impairment of systolic function. The decrease in infarct-related regional ejection fraction suggests that the impairment may be due to poor healing of the infarction scar.

Use of composite endpoints in thrombolysis trials of acute myocardial infarction

Although preventing early mortality following acute myocardial infarction (MI) is the most important goal of thrombolytic therapy, insistence on its use as the only or principal endpoint in trials of acute MI will limit the number of new thrombolytic-antithrombotic regimens that can be tested, and thus may inhibit future progress of this important area of cardiovascular therapeutics. Trials of thrombolytic therapy over the past decade, as discussed in this article, have demonstrated that: (1) thrombolytic therapy improves both mortality and intermediate endpoints, and (2) intermediate nonfatal endpoints are strongly linked to long-term mortality. Taken together, these facts provide strong evidence that intermediate nonfatal events can be used as valid endpoints in future trials of thrombolytic therapy. The unsatisfactory outcome composite endpoint, which incorporates mortality and important intermediate endpoints, will make it possible to compare innovative new regimens in much smaller trials. Ultimately, both of these approaches (i.e., megatrials using a mortality endpoint and smaller trials utilizing a composite unsatisfactory outcome endpoint) can be used in a complementary fashion. A new regimen could first be tested using the unsatisfactory outcome endpoint; if it showed particular promise, it could then become a candidate for testing in a megatrial. Conversely, if it did not prove better than standard regimens, futile research in tens of thousands of patients might be prevented. Thus, the use of composite endpoints will expand the number of new thrombolytic-antithrombotic regimens that can be tested and, it is hoped, accelerate progress in the treatment of acute MI.