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D Rovai

Publications and source records attributed to D Rovai.

At least 37 records · Page 2Linked to original sources
PubMed1995

Myocardial contrast echo effect: the dilemma of coronary blood flow and volume.

Despite the useful information provided by myocardial contrast echocardiography, the meaning of myocardial contrast intensity remains elusive. This review is meant to define the contribution of physical and biologic factors in producing myocardial contrast and to elucidate the relative roles of coronary blood flow and intramyocardial blood volume in determining contrast effect. The main physical factors influencing the contrast echo effect include the properties of microbubbles as scattering elements (mainly their radius, compressibility, stability and concentration), electronic signal processing, instrument setting and contrast-induced signal attenuation. The effect of these factors can be limited by an appropriate experimental or clinical setup. Biologic factors are less easily controllable, and changes in coronary blood flow and alterations in myocardial blood volume appear to be the main determinants of myocardial contrast intensity. Moreover, these factors influence contrast intensity in opposite directions. Both the area under the time-intensity curve and the mean transit time of myocardial contrast are inversely related to coronary blood flow but directly related to myocardial vascularity and blood volume. Therefore, an increase in coronary flow not accompanied by an increase in myocardial vascularity and volume is accompanied by a decrease in the area under the curve and mean transit time of contrast. Conversely, an increase in coronary flow mediated by augmented myocardial vascularity and volume will produce an increase in the area under the curve and mean transit time. A better understanding of the physical and biologic determinants of contrast echo intensity will be fundamental in the clinical application of new agents and technologies.

Blood Flow Velocity↗
PubMed1995

Quantitative aspects in myocardial contrast echocardiography.

Myocardial tissue perfusion is not currently quantified in the clinical setting. Thus the aim of this paper is to review the quantitative information on myocardial perfusion provided by contrast echocardiography. In a circulatory model-without the capillary network interposed between injection and sampling point of contrast-the transit time of microbubbles (source of the echo contrast effect) is inversely related to absolute flow, thus providing accurate quantitation. A similar situation is represented by blood flow inside a vessel or a cardiac cavity, where, if the prerequisites for quantitation are respected, it is possible to measure blood flow by contrast echocardiography. In the coronary circulation, the transit time of contrast microbubbles varies according to their interaction with coronary microcirculation, and to the characteristics of contrast agents as flow tracers. Echo contrast agents with small microbubbles have been injected into the coronary branches of experimental animals, under both coronary autoregulation and maximal coronary dilation, providing good estimates of coronary blood flow. The accuracy of these measurements might improve when new contrast agents, with characteristics closer to those of a flow tracer, are available. If a tracer is injected before a bifurcation, and provided it mixes adequately, the amount of tracer distributed to each branch is proportional to the corresponding blood flow. A similar situation is encountered when an echo contrast agent is injected into the aortic root or into the left main coronary artery. Here, the ratio between myocardial signal intensity in the different perfusion territories reflects the corresponding ratio of blood flows. The validity of this approach has been previously demonstrated in experimental animals and validated in patients with coronary stenoses. The injection of contrast agents into the coronary circulation at baseline and under coronary hyperaemia has the potential for measuring coronary blood flow reserve. However, what is still unclear is whether contrast echo changes reflect changes in coronary blood flow (i.e. flow reserve), coronary blood volume (i.e. coronary recruitment) or both, and also whether they influence the different types of contrast agent. Finally, myocardial contrast echocardiography can provide information on the spatial distribution of myocardial perfusion, i.e. the presence, site and extent of perfused myocardium. Thus, in models where myocardial perfusion may be either present or absent, contrast echo can provide an accurate estimate of perfusion abnormalities.

Blood Flow Velocity↗
PubMed1994

Clinical features and prognostic implications of myocardial ischemia at rest in patients with exertional angina pectoris.

The prognosis of patients with coronary artery disease (CAD) is mainly influenced by organic factors such as cardiac muscle loss and extent of CAD. The aim of this study was to investigate whether a functional factor--reversible myocardial ischemia at rest--plays an independent prognostic role. Thus, 2 groups of patients were studied and followed up for 46 +/- 32 months: 1 group (483 patients) had ischemic electrocardiographic changes only on effort and another group (224 patients) both on effort and at rest. The 2 groups did not differ significantly as to age, gender, coronary risk factors, baseline electrocardiographic abnormalities, incidence of previous myocardial infarction, angiographic left ventricular dysfunction, and extent of coronary stenoses (> or = 50% diameter reduction). There were 65 deaths (40 of which were from cardiac causes) during the 5-year follow-up. Despite the similar incidence of known predictors of prognosis, Kaplan-Meier survival analysis revealed a significantly lower 5-year survival rate in patients with mixed (84.4%) rather than exertional (92.1%) ischemia (p < 0.05 by Mantel-Haenszel test). If only cardiac causes of deaths were considered, the 5-year survival rate was still lower in patients with mixed (89.6%) rather than exertional (93.9%) ischemia. Finally, reversible ischemia at rest was an independent predictor of survival by Cox multivariate regression analysis, preceded only by the extent of CAD and left ventricular dysfunction. Thus, reversible ischemia at rest plays an independent negative role in the long-term clinical outcome of patients with CAD and positive exercise stress test results.

Aged↗
PubMed1993

Flow quantitation by radio frequency analysis of contrast echocardiography.

Contrast echocardiography has the potential for measuring cardiac output and regional blood flow. However, accurate quantitation is limited both by the use of non-standard contrast agents and by the electronic signal distortion inherent to the echocardiographic instruments. Thus, the aim of this study is to quantify flow by combining a stable contrast agent and a modified echo equipment, able to sample the radio frequency (RF) signal from a region of interest (ROI) in the echo image. The contrast agent SHU-454 (0.8 ml) was bolus injected into an in vitro calf vein, at 23 flow rates (ranging from 376 to 3620 ml/min) but constant volume and pressure. The ROI was placed in the centre of the vein, the RF signal was processed in real time and transferred to a personal computer to generate time-intensity curves. In the absence of recirculation, contrast washout slope and mean transit time (MTT) of curves (1.11-8.52 seconds) yielded excellent correlations with flow: r = 0.93 and 0.95, respectively. To compare the accuracy of RF analysis with that of conventional image processing as to flow quantitation, conventional images were collected in the same flow model by two different scanners: a) the mechanical sector scanner used for RF analysis, and b) a conventional electronic sector scanner. These images were digitized off-line, mean videodensity inside an identical ROI was measured and time-intensity curves were built. MTT by RF was shorter than by videodensitometric analysis of the images generated by the same scanner (p < 0.001). In contrast, MTT by RF was longer than by the conventional scanner (p < 0.001). Significant differences in MTT were also found with changes in the gain setting controls of the conventional scanner. To study the stability of the contrast effect, 6 contrast injections (20 ml) were performed at a constant flow rate during recirculation: the spontaneous decay in RF signal intensity (t1/2 = 64 +/- 8 seconds) was too long to affect MTT significantly. In conclusion, the combination of a stable contrast agent and a modified echocardiographic instrument provides accurate quantitation of flow in an in vitro model; RF analysis is more accurate than conventional processing as to flow quantitation by contrast echocardiography.

Animals↗
PubMed1993

Flow quantitation by contrast echocardiography. Effects of intervening tissue and of the angle of incidence between flow and ultrasonic beam.

The combination of a standardized echographic contrast agent with the analysis of the ultrasonic radio frequency (RF) signal allowed in vitro flow quantitation in a circulation model. The purpose of this study was to investigate both the effects of biological tissues, intervening between probe and insonated structure, and the effects of the angle of incidence between flow and ultrasonic beam on RF flow quantitation. Thus, the contrast agent SHU 454 was intravenously injected (0.4 ml) as a bolus into a circulation model, at variable flow rates, while keeping the pressure and volume of the vessel constant. Injections were performed with saline interposed between probe and vessel and after the addition of the subcutaneous tissue of a pig; injections were also performed using the probe normal to the flow and with an angle of incidence of 45 degrees. Echographic data were recorded by a mechanical sector scanner, capable of sampling the RF signal from a region of interest positioned in the center of the vein. Contrast echo time-intensity curves were generated. As expected, both peak intensity and the area under the curves decreased with intervening tissue (-58 and -70% of baseline values, respectively, p < 0.001). Surprisingly, mean transit time also decreased with intervening tissue (from 1.12 +/- 0.25 seconds with saline, to 0.92 +/- 0.13 seconds with tissue, p < 0.001), thus producing a systematic overestimation of flow (21% on the average). To compensate for signal attenuation, contrast injections were repeated in the presence of tissue after increasing the electronic signal amplification (10 dB), and transit time did not significantly differ from control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Intracoronary air-filled albumin microspheres for myocardial blood flow measurement.

OBJECTIVES: The aim of this study was to explore the possibility of quantifying coronary blood flow by myocardial contrast echocardiography with air-filled serum albumin microspheres (Albunex). BACKGROUND: Air-filled albumin microspheres have been proposed as an intravascular tracer for the study of myocardial perfusion by contrast echocardiography. METHODS: In six anesthetized open chest dogs, the left circumflex coronary artery was cannulated and perfused by a roller pump with blood from the femoral artery. Both air-filled albumin microspheres (0.4 ml, 2 x 10(8) spheres/ml) and technetium-99m-labeled albumin were injected as a bolus into the coronary cannula at baseline and after treatment with dipyridamole (0.56 mg/kg body weight intravenously for 4 min). Two-dimensional echographic images of the left ventricular short axis were digitized to generate myocardial time-intensity curves; myocardial radioactivity was measured by an external detector to generate radionuclide time-activity curves. RESULTS: After dipyridamole, left circumflex coronary artery blood flow (as measured by both the pump and an electromagnetic flow meter) significantly increased (from 1.06 +/- 0.28 to 3.61 +/- 1.43 ml/min per g of myocardium). Peak intensity and rise time of contrast echo curves were able to differentiate baseline myocardial perfusion from coronary hyperemia but did not show any significant correlation with coronary blood flow. A weak inverse correlation with coronary blood flow was provided by myocardial mean transit time of air-filled albumin microspheres (r = 0.33). Conversely, a close inverse correlation with coronary blood flow was obtained by myocardial mean transit time of technetium-99m-labeled albumin (r = 0.95). Myocardial transit time of air-filled albumin microspheres (1.95 +/- 0.60 s) was also markedly shorter than that of labeled albumin (5.35 +/- 3.43 s, p < 0.001) and the measurements were less reproducible. CONCLUSIONS: In this experimental study, coronary blood flow was not adequately quantified by myocardial contrast echocardiography with intracoronary injection of air-filled albumin microspheres.

Albumins↗
PubMed1993

Effects of coronary blood flow on myocardial grey level amplitude in two dimensional echocardiography: an experimental study.

OBJECTIVE: The aims were: (1) to evaluate whether differences in absolute and cyclic echocardiographic image amplitude exist in different layers (subendocardium and subepicardium) and regions (septal, anterior, lateral, inferior wall) of the canine left ventricle; (2) to assess the dependence of these variables upon local variations of coronary blood flow. METHODS: In six anaesthetised open chest dogs the circumflex coronary artery was cannulated and perfused by a roller pump with blood from their own femoral artery. Maximum coronary vasodilatation was obtained by continuous adenosine infusion. The absolute values and the transmural distribution of coronary blood flow were measured by radionuclide labelled microspheres. Echo images were obtained in short axis view by a commercially available electronic sector scanner with a 5.0 MHz transducer directly placed on the epicardial surface of the right ventricle, and digitised off-line into a matrix of 256 x 256 pixels with 25% grey level per pixel. The average grey level was calculated for each region of interest. RESULTS: In 32 different conditions, circumflex flow ranged from 0.80 to 12.89 ml.min-1.g-1 and the endocardial/epicardial ratio of flow from 0.53 to 1.73. In the circumflex region (subjected to flow changes) segmental amplitude varied from 76(SD 20) (end diastole) to 56(18) (end systole), p < 0.001. In all regions, a consistent cyclic variation was found, ranging from 9(14) to 28(16)%. For all levels of flow, subendocardial and subepicardial regions showed similar values of both absolute amplitude and cyclic variation. No significant relationship was found between transmural distribution of blood flow and either segmental amplitude (r = 0.26) or cyclic variation (r = 0.04). CONCLUSIONS: (1) a consistent cyclic grey level variation is present in all regions of the canine left ventricle, but subendocardial and subepicardial layers show similar values of both absolute amplitude and cyclic variation; (2) in the absence of severe underperfusion and echocardiographically detectable dyssynergy, absolute amplitude and cyclic variation are totally unrelated to changes in coronary blood flow.

Animals↗
PubMed1993

Myocardial washout of sonicated iopamidol does not reflect the transmural distribution of coronary blood flow.

It has been shown in previous studies that myocardial contrast echocardiography provides quantitative information on coronary blood flow. However, the ability of contrast echo to assess the transmural (endo/epicardial) distribution of blood flow is still debated. To test this hypothesis, the left circumflex coronary arteries of six anaesthetized open-chested dogs were cannulated and perfused with blood from the femoral artery. At different rates of coronary blood flow, during adenosine-induced coronary vasodilation, sonicated iopamidol and radionuclide labelled microspheres were injected into the coronary cannula, immediately proximal to a mixing chamber. Two-D echo images were digitized and myocardial time-intensity curves were obtained for the endocardial, mid- and epicardial layers. A good correlation existed between contrast washout of the entire ventricular wall and coronary flow (r = 0.85). However, the washout rate from the endo-, mid- and epicardial layers showed weak correlations with corresponding regional blood flows measured by microspheres (r = 0.56, 0.71 and 0.58, respectively). No significant relationship was found between the endo/epicardial washout ratio and the corresponding flow ratio by microspheres. Thus, measurement of the transmural distribution of coronary blood flow by myocardial contrast echocardiography remains an elusive goal.

Animals↗
PubMed1993

Hyperventilation-echocardiography test for the diagnosis of myocardial ischaemia at rest.

The purpose of this study was to assess the feasibility, safety, specificity and sensitivity of the hyperventilation test performed under echocardiographic monitoring for the provocation of vasospastic ischaemia. Hyperventilation (approximately 30 cycles.min-1 for 5 min) was performed in 104 hospitalized patients, referred for pain typical of angina at rest, under 2-D echocardiographic and 12-lead electrocardiographic monitoring. All the tests were completed and no significant side effect was observed. In-hospital documentation of spontaneous myocardial ischaemia and/or ergonovine-induced ischaemia was achieved in 38 patients (group I). A positive hyperventilation-echocardiography test (occurrence of new transient asynergies or worsening of basal ones) was obtained in 32/38 patients. Among the group I patients, only 23 had diagnostic ST-T changes and only 16 experienced chest pain during the hyperventilation-echo test. Of the 66 patients without evidence of myocardial ischaemia at rest (negative ECG monitoring during hospitalization and/or negative ergonovine maleate-echo test)--Group II, none showed echocardiographic changes, seven presented ST-T changes and six complained of typical chest pain during the test. Thus, in relation to in-hospital documentation of myocardial ischaemia at rest, both spontaneous and/or ergonovine-induced episodes, the hyperventilation-echo test showed a specificity of 100%, a sensitivity of 84%, a positive predictive value of 100% and a negative predictive value of 92%. In conclusion, hyperventilation performed under echocardiographic monitoring is feasible and safe; it can be proposed as a screening test to unmask vasospastic myocardial ischaemia in patients with angina at rest, in whom documentation of spontaneous episodes is not available.

Adult↗
PubMed1992

Myocardial washout of sonicated iopamidol reflects coronary blood flow in the absence of autoregulation.

OBJECTIVES: The aim of the study was to evaluate the relation between measurements derived from myocardial contrast echocardiography and coronary blood flow. BACKGROUND: Contrast echocardiography has the potential for measuring blood flow. METHODS: In six open chest anesthetized dogs, the left circumflex coronary artery was cannulated and perfused with blood drawn from the left femoral artery. While adenosine was infused into the circuit, circumflex flow was generated by a calibrated roller pump to the point of abolishing coronary autoregulation. At each of 25 levels of coronary blood flow, paired bolus injections of sonicated iopamidol were performed proximal to a mixing chamber. The perfused area of the left circumflex coronary artery was labeled by radioactive microspheres injected into the perfusion line. Two-dimensional echocardiographic images of the left ventricular short axis were digitized off-line, and myocardial videodensity was measured in the area perfused by the left circumflex coronary artery to generate time-intensity curves. RESULTS: The washout slope of curves showed a good correlation with coronary blood flow, ranging from 0.5 to 12.5 ml/min per g of tissue. This correlation was good both in individual dogs (correlation coefficient [r] ranging from 0.78 to 0.96) and in the group of animals as a whole (r = 0.85). Washout slope also showed a good correlation with coronary diastolic pressure (r = 0.80), which ranged from 23 to 114 mm Hg, suggesting a possible primary effect of pressure on contrast washout. However, coronary blood flow appeared to be a stronger predictor of washout slope (partial F = 26.5, p < 0.001) than did perfusion pressure (partial F = 5.9, p < 0.05 by multiple regression). The injection to injection variability in myocardial washout slope appeared to be high (24%). The gamma variate fitting of curves did not improve the correlation with coronary flow (r = 0.78). CONCLUSIONS: Myocardial washout of sonicated iopamidol reflects coronary blood flow in a model in which coronary autoregulation is abolished.

Adenosine↗
PubMed1992

Discordance between responses of contrast echo intensity to increased flow rate in human coronary circulation and in vitro.

According to the Stewart-Hamilton equation flow is inversely related to the area under the time-concentration curve produced by the transit of a detectable indicator. To verify the applicability of this principle for contrast echocardiography, we bolus injected a saccharide echo contrast agent (0.8 ml) into an in vitro circulatory model at variable flow rates. Two-dimensional echo images were digitized, and curves demonstrating the ratio of videointensity over time were derived. As expected, flow was inversely related to the area under the curves (r = 0.93). To apply this principle to human coronary circulation, we bolus injected sonicated iopamidol (4 ml) into the normal left coronary artery of six patients at baseline and after intravenous administration of dipyridamole (0.84 mg/kg in 10 minutes). Echo images were digitized, and myocardial time-intensity curves were derived. The area under the curve after dipyridamole administration (210 +/- 128 gray level.sec) did not appear significantly different from that at baseline (177 +/- 80 gray level.sec). Thus a mismatch exists between contrast echo data obtained in vitro and in human coronary circulation.

Aged↗
PubMed1991

Myocardial perfusion by contrast echocardiography. From off-line processing to radio frequency analysis.

In the last decade, many efforts have been made to study myocardial perfusion by contrast echocardiography. The possibility of differentiating normal from nonperfused myocardium and measuring the extent of the area at risk and myocardial infarction size has already been demonstrated. The aim of this paper is to review the approaches to quantitation of coronary blood flow by contrast echocardiography. In a series of studies, echocardiographic contrast agents have been treated like "deposit tracers." After an upstream contrast injection, myocardial contrast intensity (according to the partition principle) hypothetically reflects the fraction of contrast, and consequently of flow, distributed to the myocardium. A good correlation was found between changes in peak myocardial contrast intensity and corresponding changes in coronary blood flow (r = 0.83). However, this approach is limited by electronic signal distortion and attenuation artifacts. In other studies contrast agents have been treated as intravascular "free-passing" tracers, and (according to the dilution principle) their myocardial transit times hypothetically reflect coronary blood flow. A prolonged myocardial washout halftime with coronary underperfusion has been documented in animal experiments and patients with severe coronary stenosis. However, the majority of contrast agents have intermediate characteristics and do not belong to either category of tracers; furthermore, signal distortion and attenuation phenomena affect the washout phase. The time of myocardial contrast appearance, which is independent of tracer characteristics, permitted the differentiation of baseline conditions from coronary underperfusion but seemed inaccurate in the quantitation of coronary blood flow (r = 0.60).(ABSTRACT TRUNCATED AT 250 WORDS)

Contrast Media↗
PubMed1989

Frequency domain analysis of contrast echocardiographic images.

Sequences of echocontrastographic images of the dog's myocardium are analysed in the frequency domain for the identification of underperfused areas. Owing to the fact that echo images are contaminated by noise and artifacts, we have applied filtering techniques based on Fourier's methods in sequences of raw frames recorded during perfusion with a contrast agent. Thus we have been able to assess correctly the spatial and temporal distribution of the contrast, i.e. the agent kinetics which parallel the distribution of coronary blood flow, in terms of the time necessary for the flow gradient to reach its maximum value, and to describe such a distribution by a functional image obtained by means of an original procedure.

Algorithms↗
PubMed1989

Nonuniformity of the transmural distribution of coronary blood flow during the cardiac cycle. In vivo documentation by contrast echocardiography.

This study was performed to examine the transmural (endocardial vs. epicardial) heterogeneity of myocardial blood flow during the cardiac cycle (systole vs. diastole). Twenty-four contrast echocardiographic injections were performed in seven open-chest anesthetized dogs either into left anterior descending or circumflex coronary artery or into the aortic root. Two-dimensional echocardiography in short-axis view was performed and was digitized off-line into a 256 x 256 pixel matrix with 256 gray levels/pixel. All end-diastolic and end-systolic frames before and to peak contrast were analyzed. A region of interest corresponding to the most intensely opacified myocardial segment was traced, the mean videodensity measured, and the frame of initial contrast appearance detected. The region of interest was divided into three equal parallel layers corresponding to the endocardial, midcardial, and epicardial myocardium. When the echocardiographic contrast effect initially appeared in diastole, the increment in videodensity was greater for the endocardium (131 +/- 48%) than for the epicardium (71 +/- 37% of the increment in videodensity of the entire wall) (p less than 0.05). This inhomogeneity subsequently disappeared in the following end-systolic frame. When the initial echocardiographic contrast effect appeared in systole, intensity was higher in epicardium (136 +/- 83%) than in endocardium (60 +/- 60%) (p less than 0.05). However, in the following diastole, intensity was not significantly different for the two layers. Thus, myocardial contrast echocardiography demonstrates that coronary blood flow is primarily subendocardial in distribution during diastole and subepicardial during systole.

Animals↗
PubMed1987

Limitations of digital subtraction contrast echocardiography in enhancing left ventricular endocardial definition.

The purpose of this study was to evaluate whether the digital subtraction technique, applied to contrast echocardiography of the left ventricle (LV), might improve endocardial edge identification by two-dimensional echocardiography. Injections of the polysaccharide agent SHU-454 were made into the LV of five closed-chest dogs. Data were obtained at different levels of ejection fraction (EF) induced by pharmacologic or mechanical interventions and were documented by left ventriculography (VGRAM) in the right anterior oblique projection. Contrast echocardiography was recorded in the apical four-chamber view. The echocardiographic images were digitized off-line into a 256 X 256 pixel matrix with 256 gray levels/pixel. Two end-diastolic frames prior to contrast appearance were averaged to obtain a mask that was subtracted from end-diastolic contrast frames corresponding to the two beats of peak intensity. The same procedure was repeated for the systolic frames. LV edges from echocardiographic images prior to contrast appearance, from digitally subtracted echo-contrast images, and from VGRAM were traced on two occasions by two different observers. LV volumes were calculated by single-plane Simpson's rule and EF was derived by the classical equation. The intra- and interobserver reproducibility in the measurement of EF was excellent for VGRAM (r = 0.95 and 0.94, respectively), it was good for two-dimensional echocardiography (r = 0.87 and 0.73), and was fair for contrast-echo (r = 0.79 and 0.68).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1987

Contrast echo washout curves from the left ventricle: application of basic principles of indicator-dilution theory and calculation of ejection fraction.

Time-intensity curves can be obtained from contrast echocardiography of the left ventricle. The purposes of this study were: 1) to verify whether these curves conform to the basic principles of indicator-dilution theory; and 2) to derive indexes of left ventricular ejection fraction from curve analysis. In seven closed chest dogs, 31 doses of the polysaccharide agent SHU-454 were injected into the left ventricular cavity during apical four chamber two-dimensional echocardiography. Data were obtained at different levels of ejection fraction, which were induced by changes in preload, afterload and contractility, and measured by single plane Simpson's rule analysis of digital subtraction left ventriculograms. In a subset of two dogs, eight incremental doses (from 1 to 8 ml) of SHU were injected in the basal state. Contrast echocardiograms were digitized off-line, the mean gray level/pixel of a region of interest inside the left ventricular cavity was measured, and the average value for three systolic frames of each beat was used to obtain time-intensity curves. A good correlation was observed between the peak of the time-intensity curve and the quantity of contrast injected (correlation coefficient r = 0.91 by a logarithmic fit). The echo intensities observed in each animal were subsequently transformed in quantity of contrast according to these functions and their natural logarithm was calculated both with and without background subtraction. All curves relating time and the natural logarithm of the corrected intensity exhibited a descending rectilinear portion (washout) in which the correlation was very good (r = 0.97 +/- 0.02 = mean +/- SD) and which was not significantly affected by background subtraction. The validity of this fit was also unaffected by heart rate (55 to 158 beats/min) and angiographic ejection fraction (22 to 74%), and only minimally influenced by duration of contrast washout (3.3 to 14.6 seconds). Ejection fraction was calculated by an algorithm derived from indicator-dilution theory: ejection fraction = [1 - e(-bd)] X 100, where b = slope of the curve and d = cardiac cycle duration. Linear regression analysis between values of ejection fraction derived by angiography and contrast echo yielded r = 0.73. A second index, based on b and d, was derived by multiple regression analysis. Linear regression analysis of this index and angiographic ejection fraction yielded a correlation of r = 0.87.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Echocardiography in the study of myocardial ischemia in man: the clinical model of Prinzmetal's angina.

Standard echocardiography was employed to study the clinical model of myocardial ischemia with ST-segment elevation, well known as Prinzmetal's angina. Ultrasonic monitoring was performed during the appearance of ST-segment elevation, from onset of pain, during an ergonovine maleate test, hemodynamic monitoring, radioisotopic studies and, occasionally, during routine examinations, when spontaneous episodes occurred. Reliability of findings was supported by two important conditions: each patient acted as his own control, since recording was carried out from basal state to basal state, throughout ischemia, or from ischemia to basal state; behaviour of ischemic walls was compared with that of non-ischemic ones. Echocardiographic findings in acute myocardial ischemia were similar both in spontaneous and in induced episodes and were mainly characterized by: decrease in contractility indices of the ischemic segment, such as wall motion and percent systolic thickening; increase in left ventricular end-systolic and end-diastolic diameter, with a decrease in percent fractional shortening; distorted shape of ventricular cavity, transiently deformed as in a "functional" aneurysm; a sharp demarcation between ischemic and non-ischemic adjacent segment, "step sign", was present only in severe cases. Taking ST-segment elevation as a reference the time sequence of events was studied, correlating mechanical, electric and clinical markers of ischemia. At least three different echocardiographic phases were identified in the evolution of ischemic attacks: Pre-electrocardiographic phase, when mechanical impairment is detected by ultrasounds in the absence of both ST-segment changes and pain; Electrocardiographic phase, when echocardiographic signs of ischemia co-exist with obvious electrocardiographic signs.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris, Variant↗