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Biomedical subjects

A N DeMaria

Publications and source records attributed to A N DeMaria.

At least 109 records · Page 6Linked to original sources
PubMed1990

Determination of coronary flow reserve by digital angiography: validation of a practical method not requiring power injection or electrocardiographic gating.

Although coronary flow reserve is a well established measure of the physiologic significance of atherosclerotic stenosis, cumbersome methodology has prevented its widespread clinical application. This study evaluated a new simplified method of measuring coronary flow reserve based on indicator-dilution analysis of hand-injected digital coronary arteriograms. In five dogs, the circumflex artery was instrumented with an angiographic catheter, an electromagnetic flow probe and a pneumatic occluder. For each of 18 stenoses of varying severity, arteriograms were obtained under basal conditions and during papaverine-induced hyperemia. A pair of background-corrected arterial time-density curves was generated for each stenosis by off-line computer analysis of the circumflex artery arteriograms. Coronary flow reserve was calculated from the measured areas of the time-density curves and the known volume of contrast medium used to produce each curve. Angiographic flow reserve ranged from 0.9 to 6.1 (mean 2.99), whereas electromagnetic flow reserve ranged from 0.7 to 6.9 (mean 3.02). Angiographic and electromagnetic measurements of coronary flow reserve correlated well (r = 0.86). This study establishes that indicator-dilution analysis of 30 frames/s digital coronary arteriography permits the accurate determination of coronary flow reserve. The technique described employs hand injection of small doses of radiographic contrast medium using conventional catheters, and should be readily applicable to the study of human coronary artery disease.

Angiography, Digital Subtraction↗
PubMed1990

Optimal utilization of thrombolytic therapy for acute myocardial infarction: concepts and controversies.

Timely administration of thrombolytic therapy decreases myocardial infarct size, lessens the incidence of congestive heart failure and improves survival. However, available data suggest that only 10% of patients with acute infarction in the United States receive thrombolytic drugs. Given the benefits of thrombolytic therapy, all patients with myocardial infarction would likely be treated were it not for associated risks. Several groups exist in which the risk/benefit ratio of thrombolytic therapy continues to be controversial, including those with inferior infarction, absence of ST segment elevation or presentation greater than 6 h from symptom onset, elderly patients and those with hypertension. Three recent thrombolytic trials reported a reduction in mortality that was entirely independent of infarct location. Pooled data from trials involving 12,000 patients with inferior infarction have demonstrated a reduction in mortality rate (6.8% versus 8.7%, p less than 0.0001). Furthermore, improvement in regional and global left ventricular function occurred after reperfusion therapy of inferior infarction. Pooled data indicate that patients treated between 6 and 24 h after symptom onset have a lower mortality rate than do those who receive placebo (11.1% versus 13.1%, p less than 0.001). Improved survival occurs after thrombolytic therapy in patients with ST segment elevation or left bundle branch block, but not in those with isolated ST depression or a normal electrocardiogram. Age should not be considered an absolute contraindication because the lifesaving potential of thrombolytic therapy in the elderly may be two to three times that of the overall group of patients with myocardial infarction. Finally, recent studies demonstrated that patients who present with hypotension or hypertension or who have undergone cardiopulmonary resuscitation may also benefit.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1990

Negative inotropic effect of intravenous nifedipine in coronary artery disease: relation to plasma levels.

The relative extent of the vasodilator versus direct negative inotropic effects of nifedipine was studied in 15 male patients with documented coronary artery disease and normal left ventricular function. At the time of diagnostic cardiac catheterization, three groups of five patients received dose of 1, 2, and 3 mg intravenous nifedipine at a rate of 0.33 mg/min. Hemodynamic measurements and blood collections were made before, during, and every 5 minutes for 30 minutes after infusion of nifedipine. Heart rate increased and mean arterial pressure decreased significantly after the 2 and 3 mg doses of nifedipine. Systemic vascular resistance was significantly decreased and cardiac index increased after all doses of nifedipine. Maximal left ventricular dp/dt (dp/dtmax) was significantly decreased after the 3 mg infusion. The reduction in dp/dtmax was most consistent with a reduction in left ventricular contractility as opposed to changes in loading conditions. Plasma concentrations of nifedipine were significantly correlated with bidirectional changes in dp/dtmax (r = 0.86). Nifedipine concentrations below 28.2 ng/ml were associated with a rise in dp/dtmax, whereas concentrations above that level were associated with a reduction in dp/dtmax. These data indicate that intravenous nifedipine produces dose- and concentration-dependent depression of myocardial contractility in patients with coronary artery disease. Nifedipine concentrations associated with negative inotropic effects are readily achievable with common oral and sublingual doses.

Adult↗
PubMed1990

Relation of echocardiographic morphology of the mitral apparatus to mitral regurgitation in mitral valve prolapse: assessment by Doppler color flow imaging.

Few data exist regarding the relationship of valvular anatomy and coaptation to the presence of mitral regurgitation (MR) in patients with mitral valve prolapse (MVP). Therefore this study was undertaken to assess the ability of two-dimensional echocardiographic features of mitral valve morphology to predict the presence, direction, and magnitude of MR as assessed by color Doppler flow imaging. MR was present in 21 of 46 patients with MVP on two-dimensional echocardiography. Echocardiograms were specifically evaluated for leaflet apposition, leaflet morphology, and mitral anulus diameter. Color flow images were analyzed for presence of MR, direction of the regurgitant jet, and area encompassing the largest jet visible in any view. Abnormal mitral leaflet coaptation on two-dimensional echocardiography was strongly associated with the presence of MR (p = 0.003), being present in 15 of 21 patients with as compared with 5 of 25 patients without MR. Similarly, mitral leaflet thickness and MR were closely associated (p = 0.0035), with the latter being present in 9 of 30 patients with normal and 12 of 16 patients with excessive leaflet thickness. MR jet direction tended to be anterior to central with posterior leaflet prolapse and posterior or central with anterior leaflet prolapse (p = 0.02). Maximal jet area of MR tended to be larger in patients with compared with those without mitral annular dilatation (5.4 +/- 2.3 versus 2.1 +/- 1.9 cm2, p = 0.001), and in those with abnormal rather than normal leaflet thickness (4.5 +/- 2.7 versus 2.0 +/- 1.6 cm2, p = 0.009). Thus the presence, direction, and size of MR jets in MVP are related to structural abnormality of the mitral apparatus on echocardiography.

Adolescent↗
PubMed1990

Relation of left ventricular filling dynamics to alterations in load and compliance in patients with and without pressure-overload hypertrophy.

A large atrial contribution to left ventricular (LV) filling (%A) in patients with LV hypertrophy has been assumed by some to indicate abnormal LV compliance. We tested this assumption by examining the influence of short- and long-term changes in load on compliance and filling dynamics using nitroprusside to decrease load in 11 patients with severe aortic stenosis (AS) and ergonovine to increase load in nine normal subjects. LV angiographic volume was analyzed frame-by-frame simultaneous with micromanometer pressure recordings. Operative LV chamber compliance (dV/VdP) and a time constant for isovolumic relaxation rate were computed using three-constant exponential equations fit to the data. Compared with normal subjects, resting left ventricular end-diastolic pressure was increased and dV/VdP was reduced in AS, but %A was not different. %A was inversely related to left ventricular end-diastolic pressure (r = -0.48, p = 0.02) and positively correlated with dV/VdP (r = 0.90, p less than 0.001) within the AS group. Nitroprusside infusion reduced LV peak systolic pressure by 11%, end-diastolic pressure by 38%, and end-diastolic volume by 12% (p less than or equal to 0.004 for each) and tended to increase dV/VdP by 26% (p = 0.23). These alterations in load resulted in a 21% decrease (-16 ml) in the early filling volume (p less than 0.05) and variable increases (mean, +7 ml; p = NS) in the late atrial filling volume and in the percent atrial contribution to ventricular filling (26 +/- 19% to 35 +/- 25% for the AS group, p = NS) that were related to changes in compliance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Application of a new phased-array ultrasound imaging catheter in the assessment of vascular dimensions. In vivo comparison to cineangiography.

Tomographic imaging techniques such as ultrasound can provide important information in the evaluation of vascular anatomy. Recent technical advances have permitted fabrication of a small (1.83 mm), phased-array, intravascular ultrasonic imaging catheter capable of continuous real-time, cross-sectional imaging of blood vessels. We used this imaging catheter to compare intraluminal ultrasound with cineangiography in the measurement of vascular dimensions in animals and to assess the intraobserver and interobserver variability of the technique. Segmental deformation of vessel anatomy was produced by stenoses created with a tissue ligature or by balloon dilation. The mean value for measurements of vessel diameter was 5.6 mm by cineangiography and 5.7 mm by intravascular ultrasound. The correlation between cineangiography and ultrasound was close (r = 0.98). Mean cross-sectional area by angiography was 28.8 mm2 and 29.6 mm2 (r = 0.96) by ultrasound. Percent diameter reduction produced by the stenoses averaged 48.4% by cineangiography and 40.1% by ultrasound, and the two methods correlated closely (r = 0.89). Correlation between cineangiography and ultrasound for vessel diameter and area before balloon dilation was closer (r = 0.92 and 0.88) than after balloon dilation (r = 0.86 and 0.81). This difference reflected an increase in measured vessel eccentricity following balloon dilation. These data demonstrate that intravascular ultrasound is an accurate and reproducible method for measurement of vascular diameter and cross-sectional area in vivo. Intravascular ultrasound is capable of accurately identifying and quantifying segmental deformation of vascular dimensions produced by either stenoses or balloon dilation.

Angioplasty, Balloon↗
PubMed1990

Assessment of abnormal systolic intraventricular flow patterns by Doppler imaging in patients with left ventricular dyssynergy.

Few data exist regarding the consequences of abnormalities of segmental contraction on intraventricular flow patterns. The development of color Doppler flow imaging has now permitted the visualization of intraventricular blood flow patterns. Therefore, we performed Doppler flow mapping in 41 patients (12 with normal left ventricular contraction, eight with hypokinesis or akinesis, and 21 with dyskinesis) and compared these findings with left ventriculography. Systolic blood flow by Doppler mapping in subjects with normal ventricular contraction was characterized primarily by flow through the left ventricular outflow tract and into the aorta. In patients with dyskinesis, paradoxical systolic flow toward the abnormal segment was present, and persisted for at least 50% of systole in 18 of 21 patients. Mean duration of paradoxical flow in dyskinetic patients was 77% of systole. Paradoxical flow was also observed in two of five patients with akinesis but in no patients with hypokinesis. A good correlation was observed between the duration of paradoxical systolic flow and indexes of regional wall motion (radian shortening of the involved myocardium) (r = 0.77) and global ejection fraction derived from cineangiography (r = 0.79). Correlations between the area of the paradoxical systolic flow stream in midsystole and indexes of left ventricular function were less close, with r equaling 0.57 for both regional wall motion and ejection fraction. Thus, paradoxical systolic flow can be detected in most patients with left ventricular dyskinesis, and correlates with the magnitude of regional and global left ventricular dysfunction by cineangiography.

Adult↗
PubMed1989

Effect of blood pressure and afterload on Doppler echocardiographic measurements of left ventricular systolic function in normal subjects.

Doppler echocardiographic measurements of blood flow velocity and acceleration in the ascending aorta have been shown to be useful descriptors of left ventricular (LV) systolic function. Few data exist, however, regarding the influence of loading conditions, particularly afterload, on these Doppler measurements in human subjects. Therefore, 14 normal volunteers (mean age 28 years) were studied using continuous wave Doppler echocardiography performed from the suprasternal notch both at baseline and during a controlled infusion of methoxamine. LV peak systolic (delta pk) and end-systolic (delta ES) wall stresses were calculated noninvasively using blood pressure and echocardiographic dimensions. Heart rate was kept constant by transesophageal atrial pacing. Methoxamine resulted in significant increases in mean systolic (163 +/- 8 vs 129 +/- 10 mm Hg) and diastolic (93 +/- 7 vs 71 +/- 12 mm Hg) blood pressure, as well as delta pk (277 +/- 25 vs 222 +/- 40 g/cm2 x 10(3] and delta ES (97 +/- 26 vs 77 +/- 19 g/cm2 x 10(3] (p less than or equal to 0.0004 for all). Conversely, peak velocity decreased from 0.91 +/- 0.18 m/s at baseline to 0.8 +/- 0.18 m/s (p less than or equal to 0.002) and peak acceleration decreased from 22 +/- 5 m/s2 at baseline to 19 +/- 5 m/s2 (p less than or equal to 0.006) during methoxamine infusion. Flow velocity integral and LV end-diastolic dimension remained unchanged. Thus, aortic flow velocity and peak acceleration are inversely related to afterload. This relation should be considered when using serial determinations of these Doppler parameters for patients in whom changing levels of afterload might occur.

Adult↗
PubMed1989

Usefulness of color Doppler flow imaging to distinguish ventricular septal defect from acute mitral regurgitation complicating acute myocardial infarction.

Several studies have found 2-dimensional echocardiography and conventional spectral Doppler ultrasound useful in the assessment of ventricular septal defect (VSD), but few data exist regarding the usefulness of color Doppler flow imaging in evaluating this problem. Thus, the results of color flow imaging performed in 14 patients who presented with a recent acute myocardial infarction (AMI), hemodynamic instability and a new systolic murmur were evaluated. All patients underwent cardiac catheterization for definitive diagnosis, which proved to be VSD in 7 and acute mitral regurgitation in 7. VSD, identified by turbulent flow traversing the ventricular septum during ventricular systole, was correctly identified in all 7 patients with septal rupture. In the remaining 7 patients with a new murmur after AMI, mitral regurgitation was demonstrated as turbulent systolic flow in the left atrium by both color flow imaging and cine ventriculography. In all 14 patients with new murmurs, color flow imaging was 100% accurate for the presence or absence of VSD. Color flow imaging localized the septal defect to the apical septum (3), inferior septum (3) or both inferior and apical septal regions (1), and was 100% concordant for location compared with cineangiography, surgery and conventional Doppler echocardiographic techniques. Color flow imaging was accurate in identifying the presence and location of VSD complicating AMI, and accurately differentiated VSD from mitral regurgitation. Color flow imaging provides safe, rapid diagnosis of VSD complicating AMI, and may alleviate the need for diagnostic right-sided heart catheterization and preoperative cine ventriculography in these seriously ill patients.

Aged↗
PubMed1989

Quantitative assessment of mitral regurgitation by Doppler color flow imaging: angiographic and hemodynamic correlations.

This study was performed to test the hypothesis that measurements of jet area by Doppler color flow imaging can predict the angiographic severity and hemodynamic consequences of mitral regurgitation. Doppler color flow imaging was performed in 47 patients undergoing cardiac catheterization and left ventriculography. The jet area was measured as the largest clearly definable flow disturbance in the parasternal and apical views, and expressed as the maximal jet area, the mean of the largest jet area (average jet area) in two views or as the ratio of these measures to left atrial area. Correlation of all Doppler color flow measurements with angiographic grades of mitral regurgitation were comparable, maximal jet area being closest at r = 0.76. A maximal jet area greater than 8 cm2 predicted severe mitral regurgitation with a sensitivity of 82% and specificity of 94%, whereas a maximal jet area less than 4 cm2 predicted mild mitral regurgitation with a sensitivity and specificity of 85% and 75%, respectively. All patients with an average jet area greater than 8 cm2 manifested severe mitral regurgitation. However, jet area measurements showed limited correlation with regurgitant volume and fraction (r = 0.55 and 0.62, respectively) for maximal jet area, and were not predictive of hemodynamic abnormalities, including those of pulmonary wedge pressure, stroke volume or ventricular volumes. Thus, in patients with mitral regurgitation, maximal jet area from Doppler color flow imaging provides a simple measurement that predicts angiographic grade, but manifests a weak correlation with regurgitant volume and does not predict hemodynamic dysfunction.

Adult↗
PubMed1989

A new thrombolytic regimen for acute myocardial infarction using combination half dose tissue-type plasminogen activator with full dose streptokinase: a pilot study. KAMIT Study Group.

Because a previous study utilizing a combination of recombinant tissue-type plasminogen activator (rt-PA) and urokinase demonstrated reduced reocclusion rates compared with rates obtained with rt-PA alone, this study was conducted to determine whether the combination of rt-PA and streptokinase might achieve similar results at reduced cost. Forty patients with acute myocardial infarction were treated with a 1 h infusion of rt-PA (50 mg) and streptokinase (1.5 million U) administered within 6 h (mean 3.6 +/- 1.2) of symptom onset. Emergency coronary arteriography revealed patency of the infarct-related artery in 30 (75%) of 40 patients. With the addition of coronary angioplasty in those who had unsuccessful thrombolytic reperfusion, the early patency rate was increased to 98%. In-hospital mortality rate (2.5%) and the incidence of significant bleeding requiring transfusion (15%) were low. Angiographically documented reocclusion of the infarct vessel occurred in 3 (8%) of 37 patients by day 7. Regional wall motion of the infarct zone improved by 0.9 +/- 0.9 SD/chord (p less than 0.0005), and ejection fraction increased 3.6 +/- 8% units (p less than 0.05) between immediate and day 7 studies. In contrast to the price of full dose rt-PA ($2,300) or rt-PA with urokinase ($3,500), the cost of this regimen was $1,230. This pilot study demonstrates that at half the cost, a combination of half dose rt-PA with full dose streptokinase offers high infarct vessel patency, recovery of ventricular function, a low rate of reocclusion and few bleeding complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Left heart opacification with peripheral venous injection of a new saccharide echo contrast agent in dogs.

Opacification of the left heart chambers after venous injection of echo contrast agents with transpulmonary capabilities has been difficult to achieve because of a lack of availability of a biodegradable nontoxic agent that produces uniformly small microbubbles. SHU-508 is a new saccharide echo contrast agent that produces bubble sizes from 2 to 8 microns in diameter, capable of traversing the pulmonary capillary bed and resulting in left heart contrast. The echo intensity produced by this agent was compared with that of agitated saline solution, indocyanine green and SHU-454 (another experimental saccharide agent for right-sided contrast) during 136 injections in eight dogs. Videotaped two-dimensional echographic images were digitized and analyzed with the use of videodensitometry for peak right and left ventricular intensity, pulmonary transit times and time of persistence of contrast. The highest right ventricular intensity value (3,594 +/- 1,393) was achieved with SHU-508 (p less than 0.05 compared with the other agents). The right ventricular contrast seen with SHU-508 also persisted for a longer period (22.8 +/- 12 s) than with the standard agents (p less than 0.001). Left ventricular contrast with SHU-508 was visually evident in all 42 injections, whereas the peak left ventricular intensity was 35% as bright as that produced in the right ventricle by the same agent. Peak left ventricular intensity values from SHU-508 were compared with those from agitated saline solution injected from the pulmonary capillary wedge position in four dogs. SHU-508 produced brighter left ventricular intensity (1,281 +/- 607) compared with that obtained with the saline-wedge technique (p les than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗