Serial changes in left and right ventricular systolic and diastolic dynamics during the first year after an index left ventricular Q wave myocardial infarction

Hyperbaric oxygen treatment does not affect left ventricular chamber stiffness after myocardial infarction treated with thrombolysis

BACKGROUND

It has been shown that transient increase in left ventricular stiffness, assessed by Doppler-derived early filling deceleration time, occurs during the first 24 to 48 hours after myocardial infarction but returns to normal within several days. It has been reported that hyperbaric oxygen treatment has a favorable effect on left ventricular systolic function in patients with acute myocardial infarction treated with thrombolysis. However, there are no data on the effects of hyperbaric oxygen on diastolic function after myocardial infarction.

METHODS

To assess acute and short-term effects of hyperbaric oxygen on left ventricular chamber stiffness, we studied 74 consecutive patients with first acute myocardial infarction who were randomly assigned to treatment with hyperbaric oxygen combined with streptokinase or streptokinase alone. After thrombolysis, patients in the hyperbaric oxygen group received 100% oxygen at 2 atm for 60 minutes in a hyperbaric chamber. All patients underwent 2-dimensional and Doppler echocardiography 1 (after thrombolysis), 2, 3, 7, 21, and 42 days after myocardial infarction.

RESULTS

Patient characteristics, including age, sex, risk factors, adjunctive postinfarction therapy, infarct location, and baseline left ventricular volumes and ejection fraction, were similar between groups (P >.05 for all). For both groups, deceleration time decreased nonsignificantly from day 1 to day 3 and increased on day 7 (P <.001, for both groups), increasing nonsignificantly subsequently. The E/A ratio increased in the entire study group throughout the time of study (P <.001, for both groups). The pattern of changes of deceleration time was similar in both groups (P >.05 by analysis of variance), as was in subgroups determined by early reperfusion success.

CONCLUSIONS

These data in a small clinical trial do not support a benefit of hyperbaric oxygen on left ventricular diastolic filling in patients with acute myocardial infarction treated with thrombolysis.

Use of electron beam tomography to quantify cardiac diastolic function

The examples provided in this article indicate that EBT, in addition to allowing for detailed descriptions of cardiac anatomy and contraction characteristics in man, can also be used to evaluate global and regional LV diastolic function using an approach previously validated for applications in radionuclide angiography. EBT is an established imaging modality that has been shown to be highly applicable to quantitative determination of ventricular mass, RV and LV volumes, and global and regional ventricular systolic and diastolic function in a variety of cardiac pathologic states. The attractiveness of EBT lies not so much in a single determination of systolic function or diastolic filling in a given individual, but in the strength of an easily acquired, highly reproducible, and accurate serial imaging method in patients following pharmacologic or interventional therapy for a specific cardiac disease.

Assessment of Right Ventricular and Right Atrial Systolic and Diastolic Performance Using Automated Border Detection

Noninvasive assessment of right ventricular (RV) function is important clinically, but current techniques have limitations. Acoustic quantification (AQ) is an automated endocardial border detection technique that allows continuous determination of RV and right atrial (RA) area waveforms and may be useful for the assessment of RA and RV systolic and diastolic performance. Fifty patients (10 normal, 40 with RV pathology) were studied. Signal-averaged RA and RV AQ area waveforms were obtained and analyzed to compute parameters of diastolic and systolic function. All groups demonstrated significant diastolic dysfunction on the RA AQ waveform as manifested by a reduced percentage of passive atrial emptying and increased dependence on active atrial emptying. Abnormalities of diastolic performance were noted in all subgroups on RV AQ analysis as evidenced by a reduction in the percentage of ventricular filling occurring during early diastole and an increased contribution from active atrial contraction. This study demonstrates the feasibility of using automated analysis of signal-averaged RA and RV area waveforms for the evaluation of RV systolic and diastolic performance. This technique identified significant systolic and diastolic dysfunction in four groups of commonly seen right heart pathologies including biventricular heart failure, pulmonary hypertension, pressure and volume overloaded RVs, and biventricular hypertrophy.

Comparison of measurement of left ventricular ejection fraction by Tc-99m sestamibi first-pass angiography with electron beam computed tomography in patients with anterior wall acute myocardial infarction

The goal of this study was to compare measurements of left ventricular (LV) ejection fraction (EF) by first-pass radionuclide angiography ("first-pass angiography") using technetium-99m (Tc-99m) sestamibi with those by contrast-enhanced electron beam computed tomography ("electron beam tomography") as a reference technique in patients with an anterior wall acute myocardial infarction (AMI). Twenty-five patients with first Q-wave anterior wall AMI underwent paired electron beam tomographic and first-pass angiographic studies (mean, 1 day apart). Fourteen patients had 2 sets of measurements of the LVEF obtained by both methods (separated by at least 6 weeks), for a total of 39 paired measurements. LVEF by electron beam tomography was calculated from absolute systolic and diastolic LV chamber volumes. LV volumes by electron beam tomography were 199 +/- 51 ml at end-diastole and 111 +/- 42 ml at end-systole. Mean LVEF was 45 +/- 11% by first-pass tomography and 46 +/- 9% by electron beam tomography. The linear correlation coefficient between both methods was 0.82 (p <0.0001), with slope = 1.0, y-intercept = -1.1, and SEE = 6.1. The mean difference between the 2 methods was -0.7 +/- 6.0 EF units (p = 0.75). The correlation between the differences and means of both methods was 0.34 (p = 0.04), indicating a trend for first-pass angiography to overestimate LVEF in the higher range. LVEFs measured by first-pass angiography in patients with abnormal LV geometry and contraction patterns caused by anterior wall AMI agree well with those measured by electron beam tomography in the clinically relevant range.

Measurement of myocardial infarct size by electron beam computed tomography: a comparison with 99mTc sestamibi

RATIONALE AND OBJECTIVES

The authors sought to determine, using a variety of regional left ventricular ejection fraction (EF) and wall thickening (WTh) criteria, the applicability to measure left ventricular (LV) infarct size using electron-beam CT (EBCT) in patients as compared with technetium 99m (99mTc) sestamibi scanning as reference standard.

METHODS

Twelve patients (age 57 +/- 11 years) underwent 99mTc sestamibi scanning and EBCT at hospital discharge after an acute index anterior myocardial infarction. Left ventricular infarct size was defined using standard 99mTc sestamibi scanning. Regional EF and WTh were analyzed on each EBCT scan with use of a floating epicardial centroid method. In five contiguous LV tomograms, the amount of infarcted myocardium was estimated using the following EF and WTh criteria: EF < or = 35%, 30%, 25%, 20%, and WTh < or = 2 mm, 1 mm, and 0 mm.

RESULTS

Infarct size measured with 99mTc sestamibi was 33.3% (+/- 18.3%) (mean +/- SD, range 6%-54%) of the LV. Using an EF < or = 35% or absolute WTh < or = 2 mm as criteria for infarcted myocardium, EBCT yielded 28% (+/- 17%) and 27% (+/- 16%), respectively (P = NS, paired Student's t test, versus 99mTc sestamibi). Although, with use of the other criteria, EBCT tended to underestimate infarct size compared with 99mTc sestamibi, a close correlation across the entire range of infarct size determinations (range, 0.72-0.82) regardless of the underlying criteria suggested an internal consistency of the data.

CONCLUSIONS

Quantitative analysis of regional myocardial function by EBCT allows an estimate of anterior infarct size when compared with 99mTc sestamibi. This suggests that in addition to previously established applications after acute myocardial infarction such as examination of cardiac volumes and mass, EBCT also may provide for infarct size determination.

Dissociation between changes in intramyocardial function and left ventricular volumes in the eight weeks after first anterior myocardial infarction

OBJECTIVES

We sought to examine the relation between regional changes in intramyocardial function and global left ventricular (LV) remodeling in the first 8 weeks after reperfused first anterior myocardial infarction (MI).

BACKGROUND

Because of limitations in imaging methods used to date, this relation has not been thoroughly evaluated.

METHODS

We studied 26 patients (21 men, 5 women; mean age 51 years) by magnetic resonance imaging (MRI) on day 5 +/- 2 (mean +/- SD) and week 8 +/- 1 after their first anterior MI. All patients had single-vessel left anterior descending coronary artery disease and although they had received reperfusion therapy, all had regional LV dysfunction and an initial ejection fraction (EF) < or = 50%. Short-axis magnetic resonance tagging was performed spanning the LV. Percent intramyocardial circumferential shortening (%S) on a topographic basis, LV mass index, LV end-diastolic volume index (LVEDVI), LV end-systolic volume index and LV ejection fraction (LVEF) were measured.

RESULTS

Left ventricular mass index tended to decrease, whereas the LVEDVI increased from 82 +/- 24 to 96 +/- 27 ml/m2 (p = 0.002). Left ventricular end-systolic volume index remained unchanged, whereas LVEF increased from 39 +/- 12% to 45 +/- 14% (p = 0.002). Apical %S improved from 9 +/- 6% to 13 +/- 5% (p < 0.0001), as it did in the midanterior (6 +/- 6% to 10 +/- 7%, p < 0.02) and midseptal regions (8 +/- 7% to 12 +/- 6%, p < 0.02). Early dysfunction in remote midinferior and basal lateral regions resolved by 8 weeks. By multivariate analysis, the only significant predictor of an increase in LVEDVI over the study period was peak creatine kinase (p = 0.04).

CONCLUSIONS

In the first 8 weeks after a large, reperfused anterior MI, %S improved in the apex, midanterior and midseptal regions and normalized in remote noninfarct-related regions, but LV end-diastolic volumes also increased. This increased LVEDVI correlated with infarct size by peak creatine kinase and was not related to changes in global and regional LV function.

Remote noninfarcted region dysfunction soon after first anterior myocardial infarction. A magnetic resonance tagging study

BACKGROUND

Previous studies have demonstrated hyperkinetic endocardial motion of noninfarcted myocardium early after myocardial infarction (MI). We wished to substantiate the findings of increased function of remote noninfarcted regions using magnetic resonance (MR) myocardial tagging in patients soon after anterior MI.

METHODS AND RESULTS

Twenty-eight patients (25 male; mean age, 52 years) were studied on day 5 +/- 2 after first anterior MI. All had single-vessel left anterior descending coronary artery (LAD) disease and had received reperfusion therapy but had evidence of regional left ventricular (LV) dysfunction and an ejection fraction (EF) < or = 50%. Breath-hold, segmented k-space, gradient-echo MR tagging was performed with short-axis imaging spanning the LV. Percent circumferential shortening (%S) on a topographic basis, LV mass, and EF were measured. Regional %S was compared with that in 10 normal subjects (7 male; mean age, 43 years). We found reduced intramyocardial %S throughout the LV in the patient group. Percent shortening was lower in patients compared with control subjects at all sites along the long axis of the ventricle (9 +/- 5% versus 23 +/- 3% at the apex, P < .0001; 11 +/- 5% versus 21 +/- 3% at the midventricle, P < .0001; 14 +/- 3% versus 17 +/- 5% at the base, P < .02). The basal lateral and midinferior regions, remote from LAD territory, demonstrated reduced %S and a strong trend toward reduced %S, respectively.

CONCLUSIONS

Patients on day 5 after first anterior MI with single-vessel disease demonstrate reduced intramyocardial circumferential shortening throughout the LV, including remote noninfarcted regions. Potential mechanisms include altered coronary vasodilatory properties, changes in regional mechanical load, or mechanical tethering to infarcted regions.

Regional left ventricular wall thickness and systolic function during the first year after index anterior wall myocardial infarction: serial effects of ventricular remodeling

There is controversy regarding changes in regional left ventricular systolic function and thickness during remodeling after infarction. To address this, electron beam computed tomography was done in 22 patients with an index anterior wall infarction at discharge, 6 weeks, 6 months and 1 year, and global ventricular chamber volumes and mass quantified. A mid-ventricular short-axis scan from each study was divided into 4, 90 degrees sectors (anterior, septal, lateral and posterior walls). Regional wall thickness, ejection fraction, and absolute and percent wall thickening were determined and compared with 10 normal adults. Global infarct size was estimated at 24.2%+/- 3.4% of the ventricle. In these subjects, the ventricular chamber enlarged steadily during the year, while global ventricular mass initially decreased during the first 6 weeks, but then increased by 1 year. Regional ejection fraction changed little during the year, apart from the lateral wall, which was less than normal. Absolute wall thickening was reduced in the anterior (infarct) and septal walls throughout the year, but was normal and unchanged in the posterior and lateral walls. Regional percent wall thickening was not different from normal individuals. The anterior wall was thinned at discharge and tended to thin further during the year. The lateral wall was thinner than normal 6 weeks after infarction, but remained unchanged thereafter. The posterior wall tended to thin for the first 6 months, but the values at any time were not above normal. There was little change in septal wall thickness throughout the year. It is concluded that, after a moderate size, uncomplicated index anterior infarction, regional systolic function remains generally unaffected by remodeling. However, regional walls tend to thin and/or remain at normal thickness. These data confirm differential regional patterns after anterior infarction for systolic function, muscle atrophy and/or minimal hypertrophy which accompany serial changes in global ventricular chamber volumes and mass.

Serial changes in regional right ventricular free wall and left ventricular septal wall lengths during the first 4 to 5 years after index anterior wall myocardial infarction

OBJECTIVES

This study investigated serial changes in regional right ventricular free wall and interventricular septal wall lengths during the first 4 to 5 years after an index anterior wall myocardial infarction.

BACKGROUND

We previously demonstrated that remodeling after anterior wall myocardial infarction was a biventricular process; however, regional changes in biventricular topology were not investigated.

METHODS

Serial electron beam computed tomographic scanning was performed in 19 patients at five times (hospital discharge and at 6 weeks, 6 months, 1 year and 4 to 5 years) after an index anterior wall myocardial infarction, and global and regional right ventricular free wall and interventricular septal wall lengths were quantified.

RESULTS

At a mean (+/- SD) of 1,642 +/- 171 days (4 to 5 years) after infarction, global end-diastolic and end-systolic right ventricular free wall and interventricular septal wall lengths increased in parallel by 13% to 23% as global left and right ventricular volumes increased 22% to 29% from hospital discharge to 4 to 5 years after infarction. When global right ventricular free wall was compared with interventricular septal wall lengths, percent increases at end-diastole and end-systole were not statistically different at any time during the study period. Distinct regional changes in both right ventricular free wall and interventricular septal wall lengths after infarction were most dramatic during the first 6 weeks and primarily confined to the most apical levels. However, further and significant increases in both were observed by 4 to 5 years after infarction.

CONCLUSIONS

Changes in both right ventricular free wall and interventricular septal wall lengths were apparent during the 4 to 5 years after the index anterior wall infarction, and the combination of both contributed to global increases in right and left ventricular chamber volumes. Regional changes in both right ventricular free wall and interventricular septal wall lengths were almost exclusively confined to their respective apices and progressed generally in parallel; however, the cause-and-effect relation remains speculative at the present time.