Biomedical subjects

F H Sheehan

Publications and source records attributed to F H Sheehan.

At least 19 recordsLinked to original sources

PubMed2000

Cardioprotective effects of the Na(+)/H(+) exchange inhibitor cariporide in patients with acute anterior myocardial infarction undergoing direct PTCA.

BACKGROUND: Activation of Na(+)/H(+) exchange in myocardial ischemia and/or reperfusion leads to calcium overload and myocardial injury. Experimental studies have shown that Na(+)/H(+) exchange inhibitors can attenuate Ca(2+) influx into cardiomyocytes. We therefore performed a multicenter, randomized, placebo-controlled clinical trial to test the hypothesis that inhibition of Na(+)/H(+) exchange limits infarct size and improves myocardial function in patients with acute anterior myocardial infarction (MI) treated with direct PTCA. METHODS AND RESULTS: One hundred patients were randomized to receive placebo (n=51) or a 40-mg intravenous bolus of the Na(+)/H(+) exchange inhibitor cariporide (HOE 642) (n=49) before reperfusion. Global and regional left ventricular functions were analyzed by use of paired contrast left ventriculograms performed before and 21 days after PTCA and myocardial enzymes (ie, creatine kinase ¿CK, CK-MB, and LDH) as markers for myocardial tissue injury were evaluated. At follow-up, the ejection fraction was higher (50% versus 40%; P<0.05) and the end-systolic volume was lower (69.0 versus 97.0 mL; P<0.05) in the cariporide group. Significant improvements in some indices of regional wall motion abnormalities were observed, such as the percentage of chords with hypokinesis < -2 SD (P=0.045) and the severity of hypokinesis in the border zone of the infarct region (P=0.052). In addition, CK, CK-MB, or LDH release was significantly reduced in the cariporide patients. CONCLUSIONS: Our findings suggest that inhibition of Na(+)/H(+) exchange by cariporide may attenuate reperfusion injury and thereby improve the recovery from left ventricular dysfunction after MI.

Adult↗

PubMed2000

Three-dimensional echocardiographic assessment of annular shape changes in the normal and regurgitant mitral valve.

OBJECTIVES: To compare mitral annular shape and motion throughout the cardiac cycle in patients with normal hearts versus those with functional mitral regurgitation (FMR). BACKGROUND: The causes of mitral regurgitation without valvular disease are unclear, but the condition is associated with changes in annular shape and dynamics. Three-dimensional (3D) imaging provides a more comprehensive view of annular structure and allows accurate reconstructions at high spatial and temporal resolution. METHODS: Nine normal subjects and 8 patients with FMR undergoing surgery underwent rotationally scanned transesophageal echocardiography. At every video frame of 1 sinus beat, the mitral annulus was manually traced and reconstructed in 3D by Fourier series. Annular projected area, nonplanarity, eccentricity, perimeter length, and interpeak and intervalley spans were determined at 10 time points in systole and 10 points in diastole. RESULTS: The mitral annulus in patients with FMR had a larger area, perimeter, and interpeak span than in normal subjects (P <.001 for all). At mid-systole in normal annuli, area and perimeter reach a minimum, nonplanarity is greatest, and projected shape is least circular. These cyclic variations were not significant in patients with FMR. Annular area change closely paralleled perimeter change in all patients (mean r = 0.96 +/- 0.07). CONCLUSIONS: FMR is associated with annular dilation and reduced cyclic variation in annular shape and area. Normal mitral valve function may depend on normal annular 3D shape and dimensions as well as annular plasticity. These observations may have implications for design and selection of mitral annular prostheses.

Adult↗

PubMed2000

Measurement of postsystolic shortening to assess viability and predict recovery of left ventricular function after acute myocardial infarction.

OBJECTIVES: We sought to determine whether left ventricular (LV) postsystolic shortening in the region of acute myocardial infarction (MI) predicts functional recovery after primary angioplasty. BACKGROUND: Previous studies in experimental animals have shown that postsystolic shortening during temporary coronary occlusion predicts functional recovery after reperfusion. METHODS: Contrast ventriculography was performed on 35 patients with acute MI before and immediately after angioplasty, and one day, one month, three months and one year later. The centerline method was used to measure regional LV wall motion at end systole from all six ventriculograms as well as motion during isovolumic relaxation (motion(iso)) and postsystolic shortening from end systole until the end of contraction. The ventriculograms of 23 patients with normal anatomy were similarly analyzed. RESULTS: Wall motion at end systole improved significantly from baseline to follow-up in the infarct region. Postsystolic shortening at baseline correlated most closely with the recovery of wall motion at three months in patients with anterior infarction (r = 0.69, n = 25, p = 0.0001) but also with recovery at one month and one year. The correlation was slightly less powerful for motion(iso). Functional recovery could not be predicted from assessment of motion(iso) and postsystolic shortening in patients with inferior infarction. CONCLUSIONS: In patients with acute anterior MI, analysis of postsystolic shortening in the infarct region predicts the recovery of systolic LV function after reperfusion. Postsystolic shortening represents active contraction and indicates viable myocardium.

Aged↗

PubMed1999

Effect of acute myocardial infarction on the angle between the mitral and aortic valve plane.

The present study shows that acute myocardial infarction affects the left ventricle at the base as well as in the infarct region by widening of the angle between the mitral and aortic valve planes. The valve plane angle did not change over time despite significant recovery of left ventricular function, suggesting that acute myocardial infarction causes irreversible structural changes in the left ventricular myocardium remote from the infarct region.

Aged↗

PubMed1999

Influence of echocardiographic scan plane location and number on the accuracy of three-dimensional left ventricular volume and shape determination.

Quantitative 3-dimensional (3-D) echocardiography provides accurate assessment of left ventricular (LV) volume, shape, and function, but depends on manual endocardial border tracing. This study determined the minimal number of borders that need to be traced to obtain an accurate analysis of not only the volume of the left ventricle but also its shape, using the integrated methods for quantitative 3-D echocardiography developed by our laboratory. Transthoracic 3-D echocardiographic studies were obtained in 9 normal subjects and 6 patients with heart disease by freehand scanning. The LV endocardium was manually traced in 17 +/- 5 imaging planes and reconstructed in 3 dimensions. The volume and shape of each reconstruction were compared with values measured from surfaces reconstructed from 8 subsets containing 2 to 7 borders; each subset was acquired from different combinations of spatially distributed parasternal and apical views. Accurate measurements were obtained from data sets having > or = 5 borders, regardless of whether the image planes were predominantly apical or parasternal views. In conclusion, the LV border should be traced in > or = 5 imaging planes to obtain accurate measurements of volume and shape. The piece-wise smooth reconstruction method and freehand scanning using a magnetic field tracing system allow the borders to be acquired from whatever combination of acoustic windows and views provides optimal image quality.

Adult↗

PubMed1999

Sodium-hydrogen exchange inhibition: novel strategy to prevent myocardial injury following ischemia and reperfusion.

Activation of Na+/H+ exchange and subsequent calcium overload in cardiac myocytes appear to play an important role in myocardial tissue injury following ischemia and reperfusion. Results of several in vitro studies in isolated myocytes and heart preparations and in vivo studies in pigs and rats have suggested that inhibition of Na+/H+ exchange is an effective means to prevent lethal reperfusion injury, arrhythmia, and improve myocardial contractile dysfunction. In patients with acute myocardial infarction (MI), any preventive agent is administered immediately before or shortly after reperfusion, rather than before the occurrence of coronary occlusion. The direct interventional approach to treating acute MI provides the opportunity to see if reperfusion has already occurred; if not, a protective agent prior to mechanical reperfusion by percutaneous transluminal coronary angioplasty (PTCA) can be administered to limit reperfusion injury. In a multicenter, randomized, placebo-controlled clinical trial, we tested the hypothesis that inhibition of Na+/H+ exchange with cariporide (HOE 642) could limit infarct size and improve myocardial function in patients with acute transmural MI treated with direct PTCA. Patients were randomized to receive placebo or cariporide given as a 40-mg intravenous bolus prior to reperfusion. Global and regional left ventricular function were analyzed via paired contrast left ventriculograms performed before direct PTCA and after 21 days. Myocardial enzymes (i.e., creatine kinase [CK], CK-MB, and lactate dehydrogenase) as markers for myocardial tissue injury were evaluated as well. The results of this pilot study suggested that the Na+/H+ exchange inhibition could be of benefit to prevent reperfusion injury in patients with acute anterior MI treated with direct angioplasty.

Angioplasty, Balloon, Coronary↗

PubMed1999

Accuracy of quantitative ventriculographic analysis at reduced frame rates.

OBJECTIVE: We measured the error in left ventricular (LV) volume and wall motion measurement from recording contrast ventriculograms at 15 frames/sec instead of 30 frames/sec. BACKGROUND: Angiograms are increasingly recorded at 15 frames/sec instead of 30 frames/sec to improve efficiency. However the resulting error in quantitative analysis has not been evaluated. METHODS: Contrast ventriculograms recorded at 30 frames/sec of 23 patients undergoing diagnostic studies were digitized from cine film. End diastolic volume (EDV), end systolic volume (ESV), ejection fraction, anterior wall motion, and inferior wall motion were measured from a full set recorded at 30 frames/sec and from two reduced data sets at 15 frames/sec generated from the even and odd numbered frames. Intraobserver variability was compared with the error due to frame rate reduction. RESULTS: The error due to frame rate reduction did not differ significantly from intraobserver variability (p > 0.1 for all), measuring 2.6 +/- 2.2 ml (r = 0.997) vs. 1.9 +/- 1.2 ml (r = 0.999), respectively for EDV, 2.4 +/- 1.8 ml (r = 0.991) vs. 2.1 +/- 1.7 ml (r = 0.994), respectively for ESV, and 0.2 +/- 0.2 percent (r = 0. 981) vs. 0.1 +/- 1.2 percent (r = 0.994), respectively for ejection fraction. The error and variability for wall motion were 0.3 +/- 0.3 SD (r = 0.928) vs. 0.2 +/- 0.1 SD (r = 0.946), respectively for the anterior wall and 0.2 +/- 0.2 SD (r = 0.963) vs. 0.2 +/- 0.1 SD (r = 0.968), respectively for the inferior wall. CONCLUSION: Imaging the LV at 15 frames/sec does not cause a significant error in measuring LV volume and function compared with imaging at 30 frames/sec. Cathet. Cardiovasc, Intervent. 48:18-21, 1999.

Adult↗

PubMed1999

Performance of a Fourier-based program for three-dimensional reconstruction of the mitral annulus on application to sparse, noisy data.

OBJECTIVES: We investigated the accuracy of mitral annular reconstruction from noisy, sparse data typical of three-dimensional (3D) transthoracic echocardiograms. BACKGROUND: Our Fourier-based method for reconstructing the annulus from dense, accurate 3D transesophageal echo (TEE) data has been validated in vitro with four harmonics in the x, y, and z coordinates (4,4,4). METHODS: Thirteen mitral annuli were reconstructed from 'complete' 3D TEE data using four harmonics (4,4,4) and used to measure area, eccentricity. height, perimeter, and interpeak and intervalley distances; these were the 'true values'. To simulate transthoracic echo data, the TEE data sets were reduced evenly and unevenly (randomly). The complete and reduced data sets were used to reconstruct the annuli using three sets of fitting parameters: (4,4,4), (1,1,3), and (1,1,4). The resulting size and shape measurements were compared with true values. RESULTS: Regardless of the fitting parameters used, area, 2D perimeter, and 3D perimeter measurements were more accurate using reconstructions from evenly-reduced than randomly-reduced data sets (p < 0.006), and depended significantly on both data density (p < 0.015 for all) and data distribution (p < 0.02 for all). Perimeter, height, and eccentricity of the reconstructed annuli were more accurately measured using four harmonics (4,4,4). CONCLUSIONS: Mitral annuli can be reconstructed from sparse, noisy data using the (4,4,4) fit if at least 25 points are obtained from evenly distributed imaging planes. These results suggest that detailed analysis of mitral annular size and shape can be made accurately from 3D transthoracic echocardiograms.

Case-Control Studies↗

PubMed1998

Estimation of the human liver volume and configuration using three-dimensional ultrasonography: effect of a high-caloric liquid meal.

The aim of this study was to investigate whether or not a magnetic position sensing system for free-hand acquisition of 3-D ultrasound images could be used to estimate liver volumes, and to study the effect of a high-caloric meal on these volumes in healthy subjects. In vitro accuracy was evaluated by scanning porcine and rabbit livers. Ten healthy subjects were examined fasting and 30 min after ingesting a high-caloric liquid meal. Portal and hepatic vein blood flow were measured by 2-D duplex sonography. The 3-D system yielded a strong correlation (r = 0.99) between true and estimated volumes in vitro. No significant increase in liver volume in response to the meal was seen. However, portal and hepatic vein flow volume increased significantly. Experience in human subjects suggests that a complete 3-D study of liver volumes can be obtained from multiple acoustic windows. In healthy subjects, no significant increase in liver volume was seen in response to ingestion of a high-caloric liquid meal.

Adult↗

PubMed1998

Left ventricular shape analysis from three-dimensional echocardiograms.

The objective of this study was to develop and validate a three-dimensional technique of left ventricular shape analysis. Geometric phantoms and left ventricles of excised calf hearts, normal human subjects, and one subject each with aortic stenosis and dilated cardiomyopathy were reconstructed from three-dimensional echocardiograms. The fit between the reconstructions and true surfaces of the geometric phantoms and excised ventricles was determined. To evaluate in vivo left ventricular shape, a center axis was constructed from the centroid of the mitral annulus to the furthest endocardial point. Regional shape was evaluated as the relative distances of 16 separate myocardial segments from the center axis compared with a population-derived mean value. Global shape was evaluated as the average standard deviation from the normal value over the 16 segments. The system precisely reproduced the shapes of the phantoms and excised left ventricles (root-mean-square error between true and reconstructed surface 1.0 0.2 mm and 1.2 0.8 mm, respectively). The in vivo shape analysis differentiated the pathological from normal left ventricles.

Adult↗

PubMed1998

Three-dimensional measurement of the mitral annulus by multiplane transesophageal echocardiography: in vitro validation and in vivo demonstration.

Ten phantoms were scanned with a multiplane transesophageal echocardiographic probe in a water bath to assess a new method for three-dimensional modeling of the mitral annulus. The annulus was reconstructed from manually outlined borders with Fourier series in each of the three spatial coordinates. Comparisons with direct measurements by least-squares linear regression gave coefficients of determination of 0.99 for annular height, area, and circumference. Expressed as a percentage of their true values, the mean +/- SD of the errors were -0.1% +/- 3.0% for annular height, -2.8% +/- 3.1% for area, and -0.2% +/- 1.7% for circumference. The mean residual error length for phantoms was 0.64 mm compared with 1.21 mm in nine patients studied during general anesthesia. This method gives accurate and precise measurements of the mitral annulus in vitro and should be valuable for studying its morphology and dynamics in vivo.

Adult↗

PubMed1998

Normal left ventricular volumes and ejection fraction: assessment with quantitative digital cardioangiography.

The aim of this study was to assess the accuracy and precision of a digital angiography system, the General Electric DX system, as compared to conventional left ventricular cineangiography. After a phantom study, sixty patients with normal coronary arteries and normal left ventricles (LV) were studied. The LV contours were manually traced from raw or subtracted digital runs and from the cine films in an independent manner. A regression formula was used to adjust the DX derived data to the cine film results (Vcorrected = 0.693 Vmeasured +8.65 ml). There was an excellent correlation between the two methods in the end-diastolic volume index (r = 0.97, sd = 4.2 ml/m2), the end-systolic volume index (r = 0.95, sd = 2.7 ml/m2), the stroke volume index (r = 0.93, sd = 4.1 ml/m2), and the ejection fraction (r = 0.85, sd = 3.45%). We conclude that manual tracing of LV contours from either raw or subtracted digital images provides reliable and accurate measurement of LV volume and ejection fraction.

Adult↗

PubMed1998

System for quantitative three-dimensional echocardiography of the left ventricle based on a magnetic-field position and orientation sensing system.

Accurate measurement of left-ventricular (LV) volume and function are important to monitor disease progression and assess prognosis in patients with heart disease. Existing methods of three-dimensional (3-D) imaging of the heart using ultrasound have shown the potential of this modality, but each suffers from inherent restrictions which limit its applicability to the full range of clinical situations. We have developed a technique for image acquisition using a magnetic-field system to track the 3-D echocardiographic imaging planes and 3-D image analysis software including the piecewise smooth subdivision method for surface reconstruction. The technique offers several advantages over existing methods of 3-D echocardiography. The results of validation using in vitro LV's show that the technique allows accurate measurement of LV volume and anatomically accurate 3-D reconstruction of LV shape and is, therefore, suitable for analysis of regional as well as global function.

Algorithms↗

PubMed1997

A general technique for automatic left ventricle boundary validation: relation between gray scale cardioangiograms and observed boundary errors.

This article presents an automatic left ventricle boundary validation technique using the gray scale cardioangiograms, the observed boundary errors, and the left ventricle boundaries from any source that needs to be validated. This validation technique is based on the gray scale information near the boundary of the left ventricle in the cardioangiograms. Using a mutually exclusive window of fixed size, which is centered on the left ventricle boundary vertex and along the left ventricle contour, we compute a difference in contrast value for areas of the window both inside and outside the left ventricle region. These contrast values then are regressed against the observed boundary errors. The observed boundary errors are computed using the polyline distance measure, by comparing two sets of boundaries: boundaries estimated from any boundary estimation algorithm, and the original ground truth boundaries as traced by the cardiologist. We performed our experiments on a database of 245 patient studies, each having two frames: end-diastole (ED) and end-systole (ES). The mean boundary error before running the validation system was 4.4 mm. Using our boundary validation system, by rejecting 5% to 10% of the patient studies, the validation system results in an error of 4.0 mm for the cross-validation case and 3.85 mm for the ideal case. We show the reliability curves of our validation system by computing the probability of false alarm, probability of mis-detection, and mean predicted errors when a total of n patients are rejected from the database of 245 studies.

Algorithms↗

PubMed1997

Quantitative three-dimensional echocardiography by rapid imaging from multiple transthoracic windows: in vitro validation and initial in vivo studies.

Three-dimensional echocardiography has demonstrated superiority over two-dimensional techniques in the determination of left ventricular mass and volumes. We describe a technique based on a magnetic tracking system which provides rapid three-dimensional image acquisition from multiple acoustic windows. Interactive three-dimensional border tracking and reconstruction with a piecewise smooth subdivision model accurately reproduced phantom volume (calculated volume = 1.00 true volume - 0.6 ml, r = 1.000, standard error of the estimate = 1.3 ml), in vitro heart volume (calculated volume = 1.02 true volume - 1.3 ml, r = 1.000, standard error of the estimate = 0.4 ml), in vitro heart mass (calculated mass = 0.98 true mass + 1.4 gm, r = 0.998, standard error of the estimate = 2.5 gm), and in vivo stroke volume (calculated stroke volume = 1.18 Doppler stroke volume - 17.9 ml, r = 0.990, standard error of the estimate = 2.8 ml). The three-dimensional in vivo data sets, which include views from three acoustic windows, were acquired in less than 90 seconds. We conclude that this method of three-dimensional echocardiographic data acquisition and analysis overcomes limitations inherent in currently available systems.

Animals↗

PubMed1997

The effect of normalization in reducing variability in regional wall thickening.

This study was performed to evaluate a new method for measuring regional left ventricular wall thickening in terms of its variability, normal range, and diagnostic sensitivity. Two-dimensional echocardiographic images in the parasternal short-axis view of 44 normal patients and 17 patients with recent myocardial infarction were analyzed. Regional wall thickness was measured according to the centerline method at 100 chords. Wall thickening at each chord i was calculated as the change in wall thickness between end diastole and end systole at chord i, normalized by the average end-diastolic thickness of the wall segment extending from chord (i - n) to chord (i + n). Five widths of the normalization segment, defined as (2n + 1), were tested: 1 (baseline method), 5, 11, 15, and 21 chords. Widening the normalization segment significantly reduced point-to-point variability by up to 20% (p = 0.0001) evenly over the entire left ventricular contour. The magnitude of reduction approached a plateau at a normalization segment width of 11 chords. The normal mean and standard deviation for regional wall thickening were also reduced slightly but significantly in a progressive and uniform manner. The apparent severity of hypokinesis worsened by up to 0.1 +/- 0.1 SD (p = 0.006) as the normalization segment was widened. The circumferential extent of hypokinesis was not lengthened significantly until the normalization segment was 21 chords wide. The magnitude of hyperkinesis was unchanged. Normalizing over a wider segment of the myocardium reduces variability in the measurement of wall thickening, widens the separation between normal patients and those with disease, and enhances the diagnostic accuracy of quantitative two-dimensional echocardiography. The optimal normalization segment width is 11 chords.

Echocardiography↗

PubMed1997

Variability in frame by frame analysis of left ventricular wall motion from contrast angiograms.

BACKGROUND: Measurement of the timing of left ventricular (LV) wall motion, of asynchrony, and of diastolic function from contrast angiograms requires delineation of the endocardial border frame by frame through the cardiac cycle. This study was performed to determine the magnitude of intraobserver and interobserver variability in manual border tracing, and to measure the impact of this variability on the derived functional parameters. METHODS: The contrast ventriculograms of 25 patients with coronary artery disease (CAD) or with normal coronary arteries were analyzed frame by frame, by two observers or twice by the same observer. Motion was measured using the centerline method at each twelfth of systole and of diastole. Variability was calculated as the absolute difference between repeated measurements of: wall motion, asynchrony, and the time at which each region of the LV reached 10%, 50%, and 100% of peak contraction, and 50% of filling. RESULTS: Intraobserver and interobserver variability in wall motion were similar, and varied with time in the cycle, and with location on the LV contour. Variability was highest at end systole, when it averaged 8% of the normal mean for wall motion. Variability in timing was highest at peak contraction; however, the variability in measuring asynchrony averaged only 18 msec. CONCLUSION: Analysis of the magnitude and synchrony of regional LV wall motion through the cardiac cycle from contrast ventriculograms can be performed with reproducibility comparable to that at end systole.

Aged↗

PubMed1997

Effect of myocardial viability assessed by technetium-99m-sestamibi SPECT and fluorine-18-FDG PET on clinical outcome in coronary artery disease.

UNLABELLED: PET imaging of myocardial perfusion and metabolism identifies regional viability as well as patients at high risk for future cardiac events. This study evaluated a combined "hybrid" imaging approach using 99mTc-sestamibi SPECT and [18F]fluoro-2-deoxy-D-glucose (FDG) PET with regard to reversibility of regional dysfunction and to patient clinical outcome during a 2-yr follow-up. METHODS: In this study, 161 consecutive patients underwent baseline viability imaging. All had regional wall motion (RWM) abnormalities and 88% had a history of previous myocardial infarction. Regions were classified by semiquantitative analysis of sestamibi and FDG uptake as normal, mild match, mismatch or scar. For clinical outcome, patients were divided into three groups: predominantly scar tissue (Group A, n = 90), mild match (Group B, n = 26) and mismatch (Group C, n = 45). Treatment was performed with the knowledge of nuclear results. Cardiac events during follow-up were defined as death, myocardial infarction, unstable angina requiring revascularization, heart transplantation and survived resuscitation. RESULTS: Patients were followed for 29 +/- 6 mo. Revascularization rate was 30% in Group A, 81% in Group B and 80% in Group C, whereas the other patients were treated by medication. Only Group C demonstrated a significant reduction of cardiac events after revascularization, whereas, particularly in Group A, revascularization did not influence the frequency of events. Subjective assessment of angina pectoris and heart failure revealed more patients with improvement after revascularization as compared with conservative treatment. Of the 84 revascularized patients, 61 underwent follow-up angiography at 5 +/- 2 mo with RWM analysis using the centerline method. RWM improved only in mismatch regions from -2.2 +/- 1.0 s.d. to -1.0 +/- 1.4 s.d. (p < 0.01), whereas regions with a mild match or scar did not change. CONCLUSION: Nuclear imaging using 99mTc-sestamibi SPECT and [18F]FDG PET allows diagnosis of viability in regions with reduced perfusion and function with prognostic implications for functional outcome as well as for identification of patients who benefit most from revascularization.

Angioplasty, Balloon, Coronary↗