Search PubMed⌕ Search

Biomedical subjects

A N DeMaria

Publications and source records attributed to A N DeMaria.

At least 163 records · Page 9Linked to original sources
PubMed1985

Correlation of continuous wave Doppler velocities with cardiac catheterization gradients: an experimental model of aortic stenosis.

The purpose of this study was to use a canine preparation of experimental aortic stenosis to compare estimates of pressure gradient derived from continuous wave Doppler ultrasound with gradients measured directly by catheterization. Aortic stenosis was created in six mongrel dogs by placing an elastic band around the aorta. Eighty-eight different pressure gradients, ranging from 5 to 160 mm Hg, were produced by variable tightening of the aortic band. Pressure gradients were measured by micromanometer-tipped catheters placed in the left ventricle and aorta. Doppler spectral signals were simultaneously obtained using a 2.0 MHz nonimaging transducer placed directly on the surface of the ascending aorta. Doppler and pressure recordings were analyzed using a custom-designed software program to measure maximal instantaneous, mean and peak to peak gradients, as well as ejection and acceleration times. Maximal instantaneous Doppler gradient showed an excellent linear correlation with maximal instantaneous catheterization gradient (r = 0.98, SEE = 5.3 mm Hg). The correlation of Doppler-estimated maximal gradient to peak to peak catheterization gradient was also linear (r = 0.97, SEE = 6.2 mm Hg) but resulted in a systematic overestimation of pressure drop (mean overestimation = 9.0 mm Hg). Measurement of the Doppler gradient at mid-systole resulted in a more accurate correlation with the peak to peak catheterization gradient (r = 0.98, SEE = 6.1 mm Hg) and eliminated the problem of overestimation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Comparison of magnetic resonance imaging and echocardiography in determination of cardiac dimensions in normal subjects.

No data exist regarding the ability of magnetic resonance imaging to assess cardiac size and performance in human beings. Therefore, measurements of cardiac dimensions by magnetic resonance imaging were compared with those obtained by two-dimensional echocardiography in 21 normal subjects. Magnetic resonance transverse cardiac sections were obtained during electrocardiographic gating using a spin echo pulse sequence. In normal subjects, magnetic resonance imaging yielded a range of values for cardiac dimensions having a similar standard deviation as that of two-dimensional echocardiography. Diastolic measurements of the aorta, left atrium, left ventricle and septum obtained by magnetic resonance imaging correlated well with those obtained by two-dimensional echocardiography (r = 0.82, 0.78, 0.81 and 0.75, respectively). The correlation coefficient of r = 0.35 observed for the posterior wall thickness was not surprising in view of the narrow range of normal values. Only a general correlation (r = 0.53) existed for the right ventricular diastolic dimension; this was probably related to the difficulty in obtaining representative measurements due to the complex geometry of this chamber. Failure of systolic dimension measurements by magnetic resonance imaging to correlate with those obtained by echocardiography is probably related to limitations of electrocardiographic gating, especially of determining the exact end-systolic frame. Although technically complex at present, magnetic resonance imaging does provide an additional noninvasive technique for measurement of cardiac size.

Adult↗
PubMed1984

Electrocardiographic diagnosis of left ventricular hypertrophy in the presence of left bundle branch block.

The presence of left bundle branch block (LBBB) on 12-lead ECG may obscure the diagnosis of other ECG abnormalities including left ventricular hypertrophy (LVH). We retrospectively reviewed ECGs of patients with LBBB and LVH as determined by echocardiography to evaluate several ECG parameters as predictors of LVH. ECG evaluation included precordial voltage as measured by the sum of the S wave in leads V1 or V2 plus R wave in lead V6, QRS duration, mean frontal plane QRS axis, R wave amplitude in lead aVL, intrinsicoid deflection, and the presence or absence of criteria for left atrial enlargement. In the presence of LBBB and LVH, precordial voltage was significantly greater (p less than 0.001), QRS duration more prolonged (p less than 0.001), and left atrial enlargement more frequently present (p less than 0.001) than when LVH was not present. There was no difference in limb lead voltage, intrinsicoid deflection, or mean frontal plane QRS axis. Furthermore, the criterion of SV2 + RV6 greater than 4.5 mV demonstrated a sensitivity of 86% and a specificity of 100%. We conclude that a voltage criterion of SV2 + RV6 greater than 4.5 mV is diagnostic of LVH in the presence of LBBB; furthermore, QRS duration of greater than 160 msec plus left atrial enlargement strongly supports the diagnosis of LVH.

Bundle-Branch Block↗
PubMed1984

Arrhythmias in patients with mitral valve prolapse. Types, evaluation, and therapy.

A wide spectrum of cardiac rhythm and conduction disorders occur in patients with all types of valvular heart disease. However, certain types of valvular disease have a special predilection for arrhythmias, including atrial and ventricular tachyarrhythmias as well as bradyarrhythmias, inherent to the etiology of the condition itself. Most notable in this regard is mitral valve prolapse, in which cardiac dysrhythmia is now recognized as the complication of highest frequency. The principal purpose of this article is the delineation of the characteristics and management of rhythm disorders in the mitral valve prolapse syndrome.

Adult↗
PubMed1984

Superior intensity and reproducibility of SHU-454, a new right heart contrast agent.

Intravenous injection of a variety of fluids has been shown to produce right heart contrast by ultrasound, but the intensity and reproducibility achieved are variable. Thus, a new polysaccharide agent being developed for commercial distribution, SHU-454, was quantitatively compared for intensity and variability with agitated saline solution, indocyanine green, carbon dioxide and hydrogen peroxide. Videodensitometry was used to measure peak and total opacification of the right ventricle after peripheral intravenous contrast administration. One hundred eighty injections were performed in nine closed chest dogs while two-dimensional echograms were recorded. SHU-454 yielded the highest peak (p less than 0.001) and total (p less than 0.005) intensity values when compared with the standard agents. In addition, SHU-454 yielded the lowest coefficient of variation between injections (p less than 0.04) in producing this contrast effect. There were no biologically significant changes in heart rate, blood pressure or arterial blood gases during injection of any of the substances used. A newly developed agent, SHU-454, is superior to standard agents in the ability to reliably produce right heart contrast after venous injection in dogs.

Animals↗
PubMed1984

In vivo correlation of thermodilution cardiac output and videodensitometric indicator-dilution curves obtained from contrast two-dimensional echocardiograms.

In previous studies, indicator-dilution curves obtained by videodensitometry of contrast two-dimensional echocardiograms have shown close correlation with measurements of blood flow in vitro. In this study the technique was extended and contrast indicator-dilution curves obtained in vivo were correlated with simultaneous cardiac output measurements determined by thermodilution in eight dogs. Two-dimensional echocardiograms of the left ventricle were performed with the transducer on the myocardium during left atrial-pulmonary vein injection of 10 cc of a 1 X 10(-4) concentration of 30 mu diameter microballoons. A total of 148 injections were performed at 37 levels of cardiac output (1.70 to 7.90 liters/min) induced by alterations of left ventricular preload, isoproterenol and propranolol. Indicator-dilution curves were obtained from recordings of the analog signal of a linear videodensitometer focused on the left ventricle. Linear regression analysis between total area of the indicator-dilution curves and cardiac output yielded correlation coefficients (r) of 0.77 to 0.96 (mean 0.90) for individual dogs, and 0.65 for all cardiac output determinations in all dogs. Analysis of indicator-dilution curve area by the forward triangle-exponential decay method yielded enhanced individual coefficients of 0.90 to 0.97 (mean 0.94) with cardiac output and 0.61 for the group of animals. It is concluded that echographic indicator-dilution curves obtained from uniform size microballoons and videodensitometry may be obtained in vivo and correlate with cardiac output measurements.

Animals↗
PubMed1984

Accuracy of combined two-dimensional echocardiography and continuous wave Doppler recordings in the estimation of pressure gradient in right ventricular outlet obstruction.

Fifteen patients (median age 8.5 years) with fixed right ventricular outflow tract obstruction were evaluated by two-dimensional echocardiographically directed continuous wave Doppler ultrasound within 24 hours of cardiac catheterization. Pulmonary artery blood velocity measurements were determined from a real time spectral display of pulmonary artery flow profile and converted to pressure drop utilizing a modified Bernoulli equation. Use of both parasternal and subcostal imaging permitted more accurate detection of maximal flow velocity than did use of either approach alone. Gradients estimated from Doppler recordings correlated well with those measured at cardiac catheterization (correlation coefficient = 0.95, standard error of the estimate = 7.9 mm Hg) with a trend to slight underestimation of gradient in more severe obstruction. In three patients with combined valvular and subvalvular stenosis and one patient with right ventricular outlet obstruction due totally to a ventricular septal aneurysm, Doppler estimation of gradient provided an accurate assessment of total right ventricular-pulmonary artery gradient. Thus, continuous wave Doppler ultrasound combined with two-dimensional echocardiography provides a reliable noninvasive method of estimating pressure gradient in patients with right ventricular outflow tract obstruction.

Adolescent↗
PubMed1984

Treatment of ventricular tachycardia using an automatic scanning extrastimulus pacemaker.

A patient with recurrent sustained ventricular tachycardia that was resistant to both conventional and experimental antiarrhythmic agents was treated with a programmable automatic scanning extrastimulus pacemaker. The antitachycardia pacemaker was implanted only after many episodes of spontaneous and laboratory-induced ventricular tachycardia were reliably and reproducibly terminated with programmed ventricular extrastimuli. In the 6 months since implantation of the automatic scanning pacemaker, all episodes of ventricular tachycardia have been terminated successfully by the pacemaker. Acceleration of rate of ventricular tachycardia or induction of ventricular fibrillation did not occur at any time during attempted termination of ventricular tachycardia by the pacemaker. The advantages of the automatic scanning extrastimulus pacemaker over other antitachycardia pacemakers are discussed.

Electrocardiography↗
PubMed1983

Evaluation of left ventricular contractile pattern by intravenous digital subtraction ventriculography: comparison with cineangiography and assessment of interobserver variability.

The accuracy and reproducibility of measurements of left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF) and regional wall motion obtained by digital subtraction ventriculography (DSV) were compared with values of direct cineangiography in 40 patients, 21 of whom were ambulatory. DSV was performed with a 1-second, 30-ml contrast injection, which yielded real-time fluoroimages composed of 512 X 512 pixels at 30 frames/s. Single-plane right anterior oblique LV volumes were calculated by area-length methods for both DSV and cineangiography. Wall motion was assessed as percent area shortening for 12 equal myocardial segments, with results classified as abnormal if greater than 2 standard deviations below the mean of 20 normal values. DSV exhibited close correlation with angiography for EDV (r = 0.88), ESV (r = 0.92) and EF (r = 0.93). Intravenous DSV and direct cineangiography were concordant in classification of LV contractile pattern in 436 of 480 (91%) myocardial segments. Measurements of DSV obtained by 2 observers showed close correlations for EDV (r = 0.88), ESV (r = 0.95) and EF (r = 0.94), and wall motion classification was in agreement in 434 of 480 (90%) LV segments. Artifacts induced by respiratory motion, persistence of contrast in the right ventricle or left atrium, or low cardiac output may have contributed to the discrepancies observed. These data indicate that DSV is accurate in assessing LV volume and EF, correlates well with cineangiography and exhibits good interobserver reproducibility.

Analog-Digital Conversion↗
PubMed1983

Accuracy of various techniques in the measurement of the duration of the Q wave: a possible source of error in diagnosing myocardial infarction by electrocardiography.

The method of measuring the width of the Q wave on electrocardiogram is one of the variables contributing to conflicting findings regarding the accuracy of the ECG in the diagnosis of myocardial infarction. This study assesses the accuracy of a variety of methods of measuring the width of the Q wave recorded by direct-writing electrocardiographic instruments. The assessment was made by comparing the width of the Q wave as inscribed by thermal direct-writing electrocardiographs to the width of the Q wave as measured from an oscilloscopic display, the latter representing the "true" width of the Q wave. The measurement of the width as obtained from the upper edge of the tracing obtained with direct-writing electrocardiographs underestimated the true width of the Q wave, while the opposite was the case by measuring the width along the lower edge of the tracing. The most reliable ways to obtain the true width of the Q wave are: (1) to average the measurements as obtained along the upper and lower edge, (2) to measure the width along an ideal line in the middle of the tracing, or (3) to measure the width along the trailing edge of the deflection.

Diagnostic Errors↗
PubMed1983

Cor triatriatum in an adult with mitral regurgitation and massive left atrial enlargement.

An unusual case of cor triatriatum in a 52-year-old woman is described in which the preoperative diagnosis was obscured by the presence of mitral valvular regurgitation and massive left atrial enlargement; such massive left atrial enlargement has not been reported before in this entity. Only the right pulmonary veins drained into the accessory chamber. The abnormal septum dividing the left atrium was demonstrated by two-dimensional but not M-mode echocardiography.

Cardiomegaly↗
PubMed1982

The effects of calcium channel blocking agents on cardiovascular function.

The hemodynamic effects of calcium blocking agents are a composite of the various direct and indirect cardiac and peripheral vascular actions of these drugs on the individual determinants of left ventricular pump function. Calcium antagonists have been shown to have a direct negative inotropic effect, a direct negative chronotropic effect and a direct effect to produce relaxation of vascular smooth muscle and vasodilation. These agents may also elicit important indirect effects by an anti-ischemic action referable to both coronary arterial dilation and reduction in myocardial oxygen demand, as well as a baroreceptor-mediated reflex increase in beta adrenergic tone in response to vasodilation. The net result of these direct and indirect actions on cardiocirculatory dynamics is also dependent upon the individual calcium blocking agent administered, the dose and route of administration, and the underlying status of left ventricular function. Available data do not lead to a clear definition of the hemodynamic effects referable to calcium blocking agents that may be produced by the interaction of all variable factors. At present, however, it would appear that the direct negative inotropic and chronotropic actions of the calcium antagonists are offset by the reflex increase in beta adrenergic tone, in combination with the reduction in afterload produced by the peripheral vascular effects of these agents. Preliminary data suggest that certain calcium inhibiting agents may be useful in the vasodilator therapy of congestive heart failure. Nevertheless, the direct negative inotropic effects of these agents have resulted in clinically evident decompensation in cardiac performance in patients with advanced left ventricular dysfunction, and caution is warranted in the application of calcium blocking agents in this setting.

Angina Pectoris↗
PubMed1982

Efficacy of diltiazem in angina on effort: a multicenter trial.

During a multicenter study 57 patients with exercise-induced angina were evaluated with serial exercise testing to assess the efficacy of diltiazem, a calcium slow channel blocking agent, compared with a placebo. The study consisted of a 1 week single-blind placebo stabilization period followed by a double-blind triple crossover between diltiazem and placebo. Three dose levels were tested (120, 180 and 240 mg/day) in each patient. For the three time-related variables there was a significant dose-related response, with 240 mg/day being the most effective. The increases, over the washout placebo stabilization values, of the time-related variables for the 240 mg/day week compared with the corresponding placebo week were total duration of exercise 1.87 versus 1.05 minutes (p less than 0.002), time to onset of angina 1.81 versus 1.17 minutes (p less than 0.01) and time to appearance of 1 mm S-T segment depression 1.81 versus 1.01 minutes (p less than 0.002). Analysis of exercise variables indicated a significant reduction in heart rate, diastolic blood pressure, and pressure-rate product at submaximal exercise after administration of diltiazem. Diastolic blood pressure was significantly reduced at maximal exercise. Heart rate and pressure-rate product were unchanged at rest during submaximal or maximal exercise. Submaximal and maximal exercise S-T depression was not significantly altered by diltiazem. The reduction in pressure-rate product at submaximal exercise was a possible mechanism for the drug's beneficial effect in enhancing the three time-related variables.

Adult↗
PubMed1982

Importance of follow-up medical and surgical approaches to prevent reinfarction, reocclusion, and recurrent angina following intracoronary thrombolysis with streptokinase in acute myocardial infarction.

Thirty-four patients with acute myocardial infarction (mean age 55 years) who received intracoronary streptokinase for coronary thrombosis were followed for a mean of 9.4 months (longest 25 months) following the procedure of percutaneous transluminal coronary recanalization (PTCR). Twelve patients had undergone coronary artery bypass graft surgery (CABG), one had percutaneous transluminal coronary angioplasty (PTCA), and 21 received medical therapy. Among patients having CABG and PTCA, nearly 70% no longer had chest pain or reinfarction, and 62% were in New York functional class I status; there were no deaths, and there was only one reinfarction, in a patient who had graft closure. In contrast, 43% of medically treated patients had chest pain or reinfarction or had died on follow-up; only 32% of survivors were in class I functional status. Further, 71% of medically treated patients who were receiving warfarin had no chest pain and on reinfarction, whereas the majority (56%) of patients who did not receive either warfarin or antiplatelet agents either had chest pain or reinfarction or died. The importance of CABG/PTCA and anticoagulant therapy is stressed to prevent recurrent ischemia, reinfarction, and reocclusion following successful reperfusion by means of PTCR in acute myocardial infarction.

Angina Pectoris↗