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.

Prognostic value of pulmonary venous flow Doppler signal in left ventricular dysfunction: contribution of the difference in duration of pulmonary venous and mitral flow at atrial contraction.

OBJECTIVES: We assessed the contribution of difference in duration of pulmonary venous and mitral flow at atrial contraction (ARd-Ad) for prognostic stratification of patients with left ventricular (LV) systolic dysfunction. BACKGROUND: Although pulmonary venous flow (PVF) variables may supplement mitral flow patterns in evaluating left ventricular (LV) diastolic function, their value to the prognostic stratification of patients has not been investigated. METHODS: Pulsed wave Doppler mitral and PVF velocity curves were recorded in 145 patients (mean age: 70 years) with LV systolic dysfunction secondary to ischemic or nonischemic cardiomyopathy who were followed for 15 +/- 8 months. In 38% of patients, PVF signal was enhanced by the intravenous (IV) administration of a galactose-based echo-contrast agent. Based on E-wave deceleration time < or = or >130 ms and ARd-Ad, patients were grouped into restrictive (group 1, n = 40), nonrestrictive with ARd-Ad > or =30 ms (group 2, n = 55) and nonrestrictive with ARd-Ad <30 ms (group 3, n = 50). RESULTS: During follow-up, 29 patients died from cardiac causes and 28 were hospitalized for worsening heart failure (HF). On multivariate Cox model, ARd-Ad > or =30 ms provided important prognostic information with regard to cardiac mortality and emerged as the single best predictor of cardiac events (cardiac mortality, hospitalization). The 24-month cardiac event-free survival was best (86.3%) for group 3; it was intermediate (37.9%) for group 2; and it was worst (22.9%) for group 1 (p < 0.0002 group 1 vs. 3; p < 0.0005 group 2 vs. 3; p < 0.0003 group 1 vs. group 2). CONCLUSIONS: Assessment of ARd-Ad exhibited an independent value in the prognostic evaluation of patients with LV systolic dysfunction. Moreover, it contributed to identify patients at low, intermediate and high risk of cardiac events.

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.

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)

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.

Myocardial contrast echocardiography versus dobutamine echocardiography for predicting functional recovery after acute myocardial infarction treated with primary coronary angioplasty.

OBJECTIVES: We sought to compare myocardial contrast echocardiography with low dose dobutamine echocardiography for predicting 1-month recovery of ventricular function in acute myocardial infarction treated with primary coronary angioplasty. BACKGROUND: The relation between myocardial perfusion and contractile reserve in patients with acute myocardial infarction, in whom anterograde flow is fully restored without significant residual stenosis, is still unclear. METHODS: Thirty patients with acute myocardial infarction treated successfully with primary coronary angioplasty underwent intracoronary contrast echocardiography before and after angioplasty and dobutamine echocardiography 3 days after the index infarction. One month later, two-dimensional echocardiography and coronary angiography were repeated in all patients and contrast echocardiography in 18 patients. RESULTS: After coronary recanalization, 26 patients showed myocardial reperfusion within the risk area, although 4 did not. At 1-month follow-up, all patients had a patient infarct-related artery without significant restenosis. Both left ventricular ejection fraction and wall motion score index within the risk area significantly improved in the patients with reperfusion ([mean +/- SD] 38 +/- 8% vs. 48 +/- 12%, p < 0.005; and 2.35 +/- 0.5 vs. 2 +/- 0.6, p < 0.001, respectively), but not in those with no reflow. Of the 72 nonperfused segments before angioplasty, 27 showed functional improvement at follow-up. Myocardial contrast echocardiography had a sensitivity and a negative predictive value similar to dobutamine echocardiography in predicting late functional recovery (96% vs. 89% and 89% vs. 93%, respectively), but a lower specificity (18% vs. 91%, p < 0.001), positive predictive value (41% vs. 86%, p < 0.001) and overall accuracy (47% vs. 90%, p < 0.001). CONCLUSIONS: Microvascular integrity is a prerequisite for myocardial viability after acute myocardial infarction. However, contrast enhancement shortly after recanalization does not necessarily imply a late functional improvement. Thus, contractile reserve elicited by low dose dobutamine is a more accurate predictor of regional functional recovery after reperfused acute myocardial infarction than microvascular integrity.

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.

Trichinellosis outbreak caused by meat from a wild boar hunted in an Italian region considered to be at negligible risk for Trichinella.

The wild boar is an important source of trichinellosis for people in European countries as a large number of hunted animals escape veterinary control. In November 2012, uncooked sausages made with meat from wild boar were consumed by 38 persons in a village of the Lucca province (Tuscany region, Italy). Of them, 34 were serologically positive, 32 developed clinical signs and symptoms of trichinellosis, and two were asymptomatic. Trichinella britovi larvae were detected in vacuum-packed sausages made with the same batch of sausages consumed raw which had been prepared with meat from wild boar hunted in the Lucca province. As no case of trichinellosis had been reported in this region during the last 20 years, the regional public health authority considered the risk for this zoonosis to be negligible and put in place a surveillance programme on Trichinella spp. in indicator animals (mainly foxes and including wild boar for private consumption), by testing only a percentage of heads. The experience from this outbreak shows that the definition of a region with a negligible risk for Trichinella infection is not applicable to wild boar and stresses the need to test all Trichinella-susceptible wild animals intended for human consumption and to implement risk communication to consumers and hunters.

Detecting myocardial salvage after primary PTCA: early myocardial contrast echocardiography versus delayed sestamibi perfusion imaging.

UNLABELLED: The extent of myocardial salvage after primary percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI) is variable and cannot be predicted on the basis of either vessel patency or early regional wall motion assessment. The aim of this study was to evaluate the reliability of microvascular integrity, as shown by myocardial contrast echocardiography (MCE), as an indicator of tissue salvage and a predictor of late functional recovery, and to compare MCE with the quantification of tracer activity in sestamibi perfusion imaging. METHODS: Twenty-six patients with AMI who received successful treatment with primary PTCA were examined with MCE during cardiac catheterization immediately before and after vessel recanalization. Myocardial contrast effect was scored as 0 (absent), 0.5 (partial) or 1 (normal). Wall motion was assessed by two-dimensional echocardiography on admission and 1 mo later with a 16-segment model and 4-point score. Resting sestamibi SPECT was collected within 1 wk after AMI. The risk area was defined by MCE as the sum of the segments with no perfusion (score 0) before PTCA. Myocardial viability was defined by MCE as an increase in contrast score in the same segments after PTCA and by sestamibi SPECT as a preserved tracer activity (>60% of peak activity). The functional recovery after 1 mo detected by two-dimensional echocardiography was the reference standard for viability. RESULTS: A total of 50 segments showed perfusion defects before PTCA (risk area). Immediately after PTCA, the MCE score increased in 44 of 50 segments, whereas sestamibi SPECT showed preserved activity in 22 of 50 segments. After 1 mo, the wall motion score decreased in 22 of 50 segments (viable segments) and was unchanged in the remaining 28 segments. Thus, MCE showed a sensitivity of 91% and a specificity of 14% in detecting viable myocardium, whereas sestamibi SPECT showed a lower sensitivity (68%) but a significantly higher specificity (75%; P < 0.00001). The positive predictive values were 45% and 68% for MCE and SPECT (P < 0.005), respectively, and the negative predictive values were 67% and 71%, respectively. On a patient basis, SPECT was more specific (79% versus 21%; P < 0.01) and showed a higher overall predictive accuracy (88% versus 50%; P < 0.01) than MCE. CONCLUSION: The demonstration of microvascular integrity by MCE performed immediately after primary PTCA has a limited diagnostic value in predicting salvaged myocardium. Conversely, tracer activity quantification in resting sestamibi SPECT performed in a later stage is confirmed to be a reliable approach for recognizing myocardial stunning and predicting functional recovery.

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.

Impact of blunted pulmonary venous flow on the outcome of patients with left ventricular systolic dysfunction secondary to either ischemic or idiopathic dilated cardiomyopathy.

The intravenous administration of echo contrast agents enhances the Doppler signal and makes the study of pulmonary venous flow (PVF) easily achievable by transthoracic echocardiography. The aim of this study was to evaluate whether PVF patterns play a role in predicting the outcome of patients with left ventricular (LV) systolic dysfunction. Thus, 115 patients (79 men, mean age 69 years) with LV dysfunction (ejection fraction [EF] <45%) due to either ischemic or idiopathic dilated cardiomyopathy were studied and followed-up for 1 year. A quantitative interrogation of all components of PVF was feasible in 69% of patients at standard transthoracic examination; after contrast enhancement, anterograde and retrograde flow velocities were measurable in 100% and 92% of patients, respectively. A blunted PVF (defined by a systolic-to-diastolic peak velocity ratio <1) was identified in 48 patients (42%), who had a worse clinical status, a lower LVEF, and a more severe pulmonary hypertension. Thirty-six patients had cardiac events at follow-up: sudden death in 4, progressive heart failure in 12, and hospitalization for worsening heart failure in 20 patients. Multivariate Cox proportional-hazards analysis revealed that advanced New York Heart Association class, male gender, and older age were independent predictors of mortality. However, blunted PVF, reduced LVEF, older age, and increased heart rate in descending order of power were independent predictors of heart failure hospitalizations and deaths from end-stage heart failure. In conclusion, the assessments of PVF may effectively contribute to the characterization of patients with LV dysfunction and to the prediction of their outcome.

Cardiac cycle-dependent gray-level variation is not distorted by abnormal septal motion after cardiac surgery: a transesophageal videodensitometric study in humans.

Variation in cyclic (systolic-to-diastolic) echodensity has been demonstrated to be a reliable index of preserved myocardial function. Paradoxic septal motion can be observed frequently after cardiac surgery in the absence of any functional impairment. The aim of the study was to evaluate whether regional cycle-dependent gray-level variation in the septum is affected by abnormal septal motion after cardiac surgery. Ten patients undergoing cardiac surgery for coronary artery bypass grafting were evaluated by continuous transesophageal echocardiographic monitoring from the transgastric approach, both before and after surgery. In each patient septal motion was assessed qualitatively as normal or paradoxic. Images were digitized off-line and cyclic gray-level variation was measured in each patient by means of dedicated software. By selection, all patients exhibited normal septal motion and thickening at baseline. After surgery, five patients showed a paradoxic septal motion (group I), whereas in the remaining five patients (group II) septal motion remained normal. Percent area change, measured with the floating center-of-mass reference system, was similar in the two groups both before (I = 42% +/- 7% versus II = 44% +/- 13%; difference not significant) and after surgery (I = 39% +/- 8% versus II = 40% +/- 1%; difference not significant). Cyclic gray-level variation was also similar in the two groups, both at baseline (group I = 61% +/- 16% versus group II = 68% +/- 18%; difference not significant) and after surgery (50% +/- 13% versus 57% +/- 16%; difference not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of perfusion defects during coronary occlusion and myocardial reperfusion after thrombolysis by intravenous administration of the echo-enhancing agent BR1.

The purpose of this study was to detect myocardial perfusion defects as a result of coronary occlusion and myocardial reperfusion after thrombolysis with intravenous (i.v.) administration of the echo contrast agent BR1 (Bracco Research, Switzerland), which consists of microbubbles (median diameter 2.5 microm) containing sulfur exafluoride in a phospholipidic shell. To generate a coronary thrombosis, a copper coil was advanced into the left circumflex coronary artery in eight anesthetized dogs with opened chest cavities. Coronary occlusion occurred 18 +/- 10 minutes after the insertion of the coil and was documented both by an electromagnetic flow meter (as zero blood flow) and by radiolabeled microspheres (as myocardial perfusion defect). After 2 hours of occlusion, streptokinase was infused i.v.; reperfusion was documented by both the flow-meter and microspheres. Left ventricular cavity enhancement was apparent after all contrast injections. Peak cavity intensity did not increase with dose and was not affected by signal processing (suggesting signal saturation), whereas the duration of contrast effect significantly increased with the dose (from 26 +/- 16 to 147 +/- 74 seconds). Myocardial contrast intensity also increased after contrast (from 15 +/- 12 to 21 +/- 18 gray level/pixel, p < 0.001). Contrast echo detected myocardial perfusion defects (corresponding to 17% +/- 11% of LV cross-sectional area) in all the injections performed during coronary occlusion and detected myocardial reperfusion with a sensitivity of 50% versus microspheres. The extent of perfusion defects by contrast echo showed a good correlation with microspheres (r = 0.73). Myocardial reperfusion was not detected by changes in heart rate, aortic pressure, pulmonary arterial pressure, cardiac output, left ventricular fractional area change, or wall-motion score index. Hemodynamic parameters were not affected by contrast injections. Thus, the i.v. administration of BR1 allows us to accurately detect myocardial perfusion defects during coronary occlusion and, to a lesser extent, myocardial reperfusion after thrombolysis.

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)

Contrast echocardiography in the diagnosis of myocardial stunning.

The identification of viable myocardium within dysfunctional myocardium has important clinical implications. By using a microvascular tracer, myocardial contrast echocardiography may have the potential for prediction of myocardial viability in the acute and subacute phases of myocardial infarction. In the case presented, the normal myocardial perfusion observed after intravenous injection of the contrast agent, combined with severe wall motion abnormality following prolonged chest pain, suggested myocardial stunning. This was confirmed by normal coronary angiography and by restoration of normal left ventricular function at 1-month follow-up echocardiography.

Quantification methods.

Ultrasound contrast agents can be assimilated to intravascular flow tracers opening the field of myocardial blood flow (MBF) quantification. However, tracer theories are invalidated because of microbubble unstable structure and peripheral injection. In order to overcome these limitations, new models have been developed as destruction/refilling sequences allowing MBF assessment.