Contrast echocardiography using intravenous octafluoropropane and real-time perfusion imaging predicts functional recovery after acute myocardial infarction

Clinical practice of contrast echocardiography: recommendation by the European Association of Cardiovascular Imaging (EACVI) 2017

Contrast echocardiography is widely used in cardiology. It is applied to improve image quality, reader confidence and reproducibility both for assessing left ventricular (LV) structure and function at rest and for assessing global and regional function in stress echocardiography. The use of contrast in echocardiography has now extended beyond cardiac structure and function assessment to evaluation of perfusion both of the myocardium and of the intracardiac structures. Safety of contrast agents have now been addressed in large patient population and these studies clearly established its excellent safety profile. This document, based on clinical trials, randomized and multicentre studies and published clinical experience, has established clear recommendations for the use of contrast in various clinical conditions with evidence-based protocols.

The value of real-time myocardial contrast echocardiography for detecting coronary microcirculation function in coronary artery disease patients

Objective:

The aim of this study was to evaluate the value of real-time myocardial contrast echocardiography (RT-MCE) for detecting coronary microcirculation (CM) function in coronary artery disease (CAD) patients.

Methods:

Sixty-five consecutive patients were divided into CAD (n=52) and no-CAD (n=13) groups using coronary angiography (CAG). All patients underwent RT-MCE at rest and CAG within 1 week after RT-MCE. The ventricular segments in CAD patients were divided semi-quantitatively into ischemic and non-ischemic myocardial groups based on RT-MCE images. Myocardial blood volume (A), myocardial blood flow velocity (β), and mean myocardial blood flow (A×β) were obtained. The Gensini scores were calculated for CAD patients. The receiver operating characteristic (ROC) curve areas of A, β, and A×β were calculated to assess CM function in CAD patients.

Results:

A total of 798 and 204 segments were investigated in the CAD and non-CAD groups, respectively. In CAD patients, 332 ischemic and 466 non-ischemic segments were identified. The values of A, β, and A×β were significantly different among non-CAD, CAD, ischemic, and non-ischemic groups. ROC curve areas of A, β, and A×β were 0.85, 0.79, and 0.83, respectively, and significant differences were observed in these values among three Gensini score groups of the CAD patients.

Conclusion:

Varying degrees of CM function deterioration was observed in CAD patients both in ischemic and non-ischemic areas, with the deterioration being more sever in the former.

Prognostic Value of Real Time Myocardial Contrast Echocardiography after Percutaneous Coronary Intervention

Real time myocardial contrast echocardiography (RTMCE) is a cost-effective and simple method to quantify coronary flow reserve (CFR). We aimed to determine the value of RTMCE to predict cardiac events after percutaneous coronary intervention (PCI). We have studied myocardial blood volume (A), velocity (β), flow indexes (MBF, A × β), and vasodilator reserve (stress-to-rest ratios) in 36 patients with acute coronary syndrome (ACS) who underwent PCI. CFR (MBF at stress/MBF at rest) was calculated for each patient. Perfusion scores were used for visual interpretation by MCE and correlation with TIMI flow grade. In qualitative RTMCE assessment, post-PCI visual perfusion scores were higher than pre-PCI (Z = -7.26, P < 0.01). Among 271 arteries with TIMI flow grade 3 post-PCI, 72 (36%) did not reach visual perfusion score 1. The β- and A × β-reserve of the abnormal segments supplied by obstructed arteries increased after PCI comparing to pre-PCI values (P < 0.01). Patients with adverse cardiac events had significantly lower β- and lower A × β-reserve than patients without adverse cardiac events. In the former group, the CFR was ≥ 1.5 both pre- and post-PCI. CFR estimation by RTMCE can quantify myocardial perfusion in patients with ACS who underwent PCI. The parameters β-reserve and CFR combined might predict cardiac events on the follow-up.

The myocardial ischemia evaluated by real-time contrast echocardiography may predict the response to cardiac resynchronization therapy: a large animal study

Evidence-based criteria for applying cardiac resynchronization therapy (CRT) in patients with ischemic cardiomyopathy are still scarce. The aim of the present study was to evaluate the predictive value of real-time myocardial contrast echocardiography (RT-MCE) in a preclinical canine model of ischemic cardiomyopathy who received CRT. Ischemic cardiomyopathy was produced by ligating the first diagonal branch in 20 beagles. Dogs were subsequently divided into two groups that were either treated with bi-ventricular pacing (CRT group) or left untreated (control group). RT-MCE was performed at baseline, before CRT, and 4 weeks after CRT. Two-dimensional speckle tracking imaging was used to evaluate the standard deviation of circumferential (Cir12SD), radial (R12SD), and longitudinal (L12SD) strains of left ventricular segments at basal as well as middle levels. Four weeks later, the Cir12SD, R12SD, and myocardial blood flow (MBF) of the treated group were significantly improved compared to their non-CRT counterparts. Furthermore, MBF values measured before CRT were significantly higher in responders than in non-responders to bi-ventricular pacing. Meanwhile, no significant differences were observed between the responder and non-responder groups in terms of Cir12SD, R12SD, and L12SD. A high degree of correlation was found between MBF values before CRT and LVEF after CRT. When MBF value>24.9 dB/s was defined as a cut-off point before CRT, the sensitivity and specificity of RT-MCE in predicting the response to CRT were 83.3% and 100%, respectively. Besides, MBF values increased significantly in the CRT group compared with the control group after 4 weeks of pacing (49.8±15.5 dB/s vs. 28.5±4.6 dB/s, p<0.05). Therefore, we considered that myocardial perfusion may be superior to standard metrics of LV synchrony in selecting appropriate candidates for CRT. In addition, CRT can improve myocardial perfusion in addition to cardiac synchrony, especially in the setting of ischemic cardiomyopathy.

Clinical usefulness of low-dose dobutamine stress real-time myocardial contrast echocardiography for detection of viable myocardium

OBJECTIVES

To evaluate and compare the diagnostic accuracy of semi-quantitative and quantitative real-time myocardial contrast echocardiography (RT-MCE) with low-dose dobutamine stress echocardiography (LD-DSE) in detecting viable myocardium.

METHODS

Thirty in-patients with coronary artery disease and regional wall motion abnormalities underwent RT-MCE without and with LD-DSE. Percutaneous coronary intervention was performed within 1 week after RT-MCE in all patients. Myocardial perfusion was evaluated from A, β, and A × β indices from microbubble replenishment curves. The motion of each myocardium segment was observed by routine echocardiography 1, 3, and 6 months after percutaneous coronary intervention and its improvement over time was the criterion of viable myocardium.

RESULTS

RT-MCE sensitivity and specificity for the assessment of viable myocardium were 71.7% and 69.8%, rising to 81.3% and 76.7% (p < 0.05) when combined with LD-DSE. Using quantitative RT-MCE with cutoff values of A, β, and A × β, the sensitivity and specificity were 75.6%, 78.8%, 82.1%, and 82.4%, 77.9%, 78.6%, respectively. When combined with LD-DSE, the sensitivity and specificity were 86.0%, 83.2%; 88.9% and 84.1%; 89.6%, 79.9%, respectively.

CONCLUSIONS

Quantitative RT-MCE analysis yielded higher sensitivity and specificity than semi-quantitative RT-MCE with or without LD-DSE for the detection of viable myocardium.

Myocardial perfusion imaging with contrast ultrasound

This report reviews the development and clinical application of myocardial perfusion imaging with myocardial contrast echocardiography (MCE). This includes the development of microbubble formulations that permit the detection of left ventricular contrast from venous injection and the imaging techniques that have been invented to detect the transit of these microbubbles through the microcirculation. The methods used to quantify myocardial perfusion during a continuous infusion of microbubbles are described. A review of the clinical studies that have examined the clinical utility of myocardial perfusion imaging with MCE during rest and stress echocardiography is then presented. The limitations of MCE are also discussed.

Identification of hibernating myocardium with myocardial contrast echocardiography

Very little is known about the accuracy of intravenous myocardial contrast echocadiography (MCE) in the detection of myocardial hibernation. There are also currently no data on the comparison of MCE to late gadolinium-enhanced magnetic resonance (LGE-MR) in this clinical setting. The aim of this pilot study was to predict recovery of regional function in patients with ischemic LV dysfunction undergoing bypass surgery and to compare the accuracy of MCE with LGE-MR in this clinical setting. The sensitivity of preserved myocardial perfusion during MCE for segmental function recovery (hibernating myocardium) of akinetic segments was 78% and was similar to LGE-MR (87%, p--NS). Specificity of MCE was higher than for LGE-CMR (72%, and 52%, respectively; p<0.01). This pilot study has showed good diagnostic accuracy of MCE for prediction of function recovery after bypass surgery, which is comparable to "gold standard" in assessing myocardial viability--LGE-MR.

Prognostic Value of Longitudinal Strain After Primary Reperfusion Therapy in Patients with Anterior-wall Acute Myocardial Infarction

OBJECTIVES

We sought to test whether longitudinal strain (LS) can be a useful predictor of left ventricular (LV) remodeling after reperfusion therapy in acute myocardial infarction.

BACKGROUND

Predicting LV remodeling based on quantification of regional contractility remains an elusive goal of echocardiography.

METHODS

In 50 patients with anterior-wall acute myocardial infarction, the peak systolic velocity and LS were measured by Doppler tissue imaging (LS(DTI)) and speckle tracking imaging (LS(2D)) at 7 LV segments of left anterior descending coronary artery territory after primary reperfusion therapy. LV remodeling was defined as an increase in LV end-diastolic volume of greater than or equal to 15% at follow-up echocardiography.

RESULTS

A total of 22 patients showed LV remodeling, who had significantly lower baseline ejection fraction, LS(DTI), and LS(2D), and higher wall-motion score index and peak creatine kinase-MB with shorter deceleration time of early diastolic mitral inflow than those without LV remodeling. LS(2D) (odds ratio [OR] = 1.307, 95% confidence interval [CI] = 1.082-1.579, P = .005) and LS(DTI) (OR = 1.430, 95% CI = 1.152-1.776, P = .001) were independent predictors of LV remodeling. During clinical follow-up of 18.3 +/- 9.0 months, death or congestive heart failure developed in 11 patients (22%); LS(2D) (OR = 1.455, 95% CI = 1.142-1.852, P = .002) and LS(DTI) (OR = 1.436, 95% CI = 1.093-1.888, P = .009) were independent predictors.

CONCLUSIONS

LS immediately after primary reperfusion therapy is an excellent predictor of LV remodeling and adverse events in patients with anterior-wall acute myocardial infarction.

Determination of size and transmural extent of acute myocardial infarction by real-time myocardial perfusion echocardiography: a comparison with magnetic resonance imaging

OBJECTIVE

The exact determination of acute myocardial infarction (AMI) extent is still a challenging issue. Quantitative myocardial perfusion echocardiography (MPE) with parametric imaging (PI) and gray scale (GS) has been shown to accurately measure infarcted area in animals, but not in human beings. We sought to validate MPE quantification of transmural extent and size of AMI using magnetic resonance imaging (MRI) as a gold standard.

METHODS

Twenty patients (12 men, 64 +/- 13 years) underwent MPE and MRI between the second and fifth day post-AMI. Infarct area and location, number of involved segments, and transmural extent in each segment were determined by PI using beta value and GS. Results were compared with late enhanced MRI.

RESULTS

There was 99% agreement between both methods regarding the segmental location. The correlation between infarct area by MRI and GS was 0.82 (P < .001) whereas MRI and beta PI was 0.92 (P < .001). The correlation between transmural extent by MRI and GS was 0.77 (P < .001), and between MRI and beta PI was 0.93 (P < .001).

CONCLUSION

There was a good correlation between MPE, in special beta PI, with MRI in measuring infarcted area and its transmural extent in patients with AMI.

Contrast echocardiography for the assessment of myocardial viability

PURPOSE OF REVIEW

The availability of an accurate, non-invasive method for distinguishing viable from irreversibly damaged myocardium, after acute myocardial infarction or in chronic coronary artery disease, is important in clinical decision making. Such a tool would enable physicians to identify patients most likely to benefit from revascularization strategies in patients with coronary artery disease and left ventricular dysfunction. Myocardial contrast echocardiography is a new technique that utilizes acoustically active gas-filled microspheres (microbubbles), which remain exclusively in the intravascular space and allow the simultaneous assessment of global and regional myocardial structure, function, and perfusion. An increasing body of data supports its role in assessing myocardial viability and predicting the recovery of function.

RECENT FINDINGS

Myocardial contrast echocardiography accurately differentiates 'stunning' from necrosis, delineates transmural extent of infarction, predicts recovery of regional and global left ventricular systolic function in the recuperative phase, identifies patients at high risk of left ventricular remodelling, and provides incremental viability data when performed in conjunction with low-dose dobutamine echocardiography.

SUMMARY

Technological advances have positioned myocardial contrast echocardiography as a safe, practical bedside technique for the evaluation of myocardial viability. It has comparable accuracy with other non-invasive imaging techniques, such as dobutamine stress echocardiography, radionuclide scintigraphy and cardiac magnetic resonance imaging.

Myocardial Contrast Echocardiography Evolving as a Clinically Feasible Technique for Accurate, Rapid, and Safe Assessment of Myocardial Perfusion

Intravenous myocardial contrast echocardiography (MCE) is a recently developed technique for assessment of myocardial perfusion. Up to now, many studies have demonstrated that the sensitivity and specificity of qualitative assessment of myocardial perfusion by MCE in patients with acute and chronic ischemic heart disease are comparable with other techniques such as cardiac scintigraphy and dobutamine stress echocardiography. Furthermore, quantitative parameters of myocardial perfusion derived from MCE correlate well with the current clinical standard for this purpose, positron emission tomography. Myocardial contrast echocardiography provides a promising and valuable tool for assessment of myocardial perfusion. Although MCE has been primarily performed for medical research, its implementation in routine clinical care is evolving. This article is intended to give an overview of the current status of MCE.

Lower myocardial perfusion reserve is associated with decreased regional left ventricular function in asymptomatic participants of the multi-ethnic study of atherosclerosis

BACKGROUND

Myocardial ischemia is an important determinant of regional left ventricular systolic function. Myocardial blood flow reserve may be impaired by cardiovascular disease before alterations of myocardial perfusion at rest become manifest. Nevertheless, the relation between flow reserve and regional myocardial function has not been studied in individuals without a history of clinical heart disease.

METHODS AND RESULTS

Seventy-four participants (66+/-9 years, mean+/-SD) of the Multi-Ethnic Study of Atherosclerosis (MESA) underwent myocardial magnetic resonance tagging and contrast-enhanced perfusion studies. Regional myocardial function was evaluated as peak systolic circumferential strain (Ecc) in the three main coronary territories (left anterior descending [LAD], left circumflex, and right coronary artery [RCA]). Myocardial blood flow at rest and during adenosine-induced hyperemia was quantified by contrast-enhanced magnetic resonance imaging, to study the relation between regional flow and function after multivariable adjustment for age, gender, body mass index, left ventricular mass, and traditional risk factors. Lower regional myocardial blood flow during hyperemia was associated with reduced regional left ventricular function expressed as lower Ecc in the RCA (P<0.01) and left circumflex regions (P<0.05) measured in the subendocardium, mid-wall, and subepicardium. In contrast, no significant association was seen in the LAD territory (P=0.16). In addition, segmental function in LAD and RCA regions was reduced when individuals in the lowest 10th percentile for regional myocardial flow reserve were compared with the other participants. Absolute decreases in mid-wall Ecc LAD and RCA and global Ecc were 3.0%, 3.4%, and 2.8%, respectively (P<0.05 for all regions).

CONCLUSIONS

Lower myocardial flow reserve is related to reduced regional function in asymptomatic individuals.

Usefulness of Myocardial Contrast Echocardiography Early After Acute Myocardial Infarction

OBJECTIVES

(1) Evaluate wall motion and perfusion abnormalities after reperfusion therapy of the culprit lesion, (2) delineate the ability of myocardial contrast echocardiography (MCE) to evaluate the microvasculature after reperfusion, in order to distinguish between stunning and necrosis in the risk area.

METHODS

We analyzed 446 segments from 28 patients, 10 normal controls (160 segments), and 18 with a first AMI (286 segments). MCE was obtained with Optison and a two-dimensional echocardiography was performed at 3 months post acute myocardial infarction (AMI).

RESULTS

In the group with AMI, we analyzed 286 segments, of which 107 had wall motion abnormalities (WMA) related to the culprit artery. Two subgroups were identified: Group I with WMA and normal perfusion (50 segments, 47%) and Group II with WMA and perfusion defects (57 segments, 53%). According to the 2D echocardiogram at 3 months, they were further subdivided into: Group IA: with wall motion improvement (stunning): 18 segments, 36%, Group IB: without wall motion improvement: 32 segments, 64%, Group IIA: with wall motion improvement: 12 segments, 21%, Group IIB: without wall motion improvement (necrosis): 45 segments, 79%.

CONCLUSIONS

(1) The presence of myocardial perfusion in segments with WMA immediately after AMI reperfusion therapy predicts viability in most patients. Conversely, the lack of perfusion is not an absolute indicator of the presence of necrosis. (2) Perfusion defects allow to detect patients with thrombolysis in myocardial infarction (TIMI) 3 flow and "no-reflow" phenomenon who will not show improved wall motion in the 2D echocardiogram. However, some patients with initial no-reflow could have microvascular stunning and their regional contractile function will normalize after a recovery period.

Correlation between ECG and myocardial perfusion after mechanical reperfusion of acute myocardial infarction

The identification of viable myocardium after myocardial infarction (MI) carries major prognostic impact. Due to myocardial stunning early after successful mechanical reperfusion of acute myocardial infarction, analysis of myocardial perfusion but not of contractile function can be used to differentiate between necrotic and viable myocardium. Although being widely regarded as an indicator of infarct transmurality, the relation between post-infarct Q-wave formation and the amount of viable myocardium has not been studied. We hypothesized that there was a correlation between the extent of Q-wave formation and the extent of perfusion abnormalities on myocardial contrast echocardiography early after successful mechanical reperfusion of first acute myocardial infarction and that the extent of post-infarct Q-wave formation might therefore be used as a simple estimate of the amount of viable myocardium.

METHODS AND RESULTS

47 patients with first MI and treated by direct PCI were enrolled. Patients were divided into 3 groups according the presence and number of abnormal Q waves (group A-no abnormal Q wave; group B-< or =2 abnormal Q waves, group C-> or =3 abnormal Q waves). Left ventricular pump function was defined by ejection fraction (EF) on ventriculography and wall motion score index (WMSI) on echocardiography. Myocardial perfusion was defined by perfusion score index (PSI) on myocardial contrast echocardiography. Patients in group A had significantly better LV function than patients in other groups [EF 57+/-5 vs. 48+/-11% (group B) and 47+/-10% (group C); p<0.05], also WMSI was the best in this group [1.34+/-0.22 vs. 1.67+/-0.39 (group B) and 1.68+/-0.31 (group C); p<0.01]. Myocardial perfusion assessed by PSI was best in group A (1.2+/-0.3, p<0.05). With respect to PSI, there was a significant difference between group B and C (1.41+/-0.21 vs. 1.56+/-0.29; p<0.05), even though EF and WMSI did not differ in these groups. The amount of perfused segments with severe wall motion abnormality was higher in group B compared to group C (47% vs. 25%; p<0.05).

CONCLUSION

In patients after successful mechanical reperfusion of first MI, the extent of Q-wave formation on ECG may be regarded as a corollary of the amount of myocardial microvascular damage and may, therefore, be used to estimate the amount of viable myocardium post-infarct.

Usefulness of real-time intravenous myocardial contrast echocardiography in predicting left ventricular dilation after successfully reperfused acute myocardial infarction

The ability of real-time intravenous myocardial contrast echocardiography to predict left ventricular remodeling after reperfused acute myocardial infarction was assessed in 47 patients. Intravenous myocardial contrast echocardiography was an independent predictor of left ventricular dilation after acute myocardial infarction. In particular, normal contrast opacification within dyssynergic segments indicated a very low risk of remodeling.

Value of myocardial contrast echocardiography for predicting left ventricular remodeling and segmental functional recovery after anterior wall acute myocardial infarction

OBJECTIVE

We sought to study the value of microvascular perfusion assessed by myocardial contrast echocardiography in predicting left ventricular remodeling after anterior wall acute myocardial infarction.

METHODS

In 31 patients myocardial contrast echocardiography was performed up to 48 hours after acute myocardial infarction with determination of end-diastolic and end-systolic volumes, wall-motion score index, and myocardial perfusion score index (MPSI) at rest and under dobutamine stress at 6 months. Patients were classified into remodeling group (RG) (n = 19) and non-RG (n = 12), and, according to number of segments without opacification, reflow (< or =2 segments, n = 15) and no-reflow (>2 segments, n = 16) groups.

RESULTS

Wall-motion score index (1.84 +/- 0.22 vs 1.64 +/- 0.3; P =.049), MPSI (1.53 +/- 0.25 vs 1.26 +/- 0.17; P =.006), and number of segments without contrast (3.11 +/- 2.23 vs 1.08 +/- 1.38; P =.018) were higher in RG than in non-RG. End-diastolic and end-systolic volumes, and wall-motion score index, increased significantly in RG at 6 months and decreased in non-RG. MPSI increased in RG (1.53 +/- 0.25-1.66 +/- 0.21; P =.011) and was the only independent predictor of left ventricular remodeling (odds ratio = 1.8; 95% confidence interval = 1.15-2.82; P =.010). No-reflow group presented 27.8 +/- 19.9% of segments with resting functional recovery or contractile reserve, and reflow group presented 69.9 +/- 31.2% (P <.001).

CONCLUSION

MPSI obtained 48 hours after acute myocardial infarction is an independent predictor of left ventricular remodeling. Patients with two or fewer segments without opacification revealed a better prognosis of resting ventricular function and contractile reserve.

Comparison of intravenous myocardial contrast echocardiography and low-dose dobutamine echocardiography for predicting left ventricular functional recovery following acute myocardial infarction

Akinesia after acute myocardial infarction (AMI) may be reversible or irreversible. Distinguishing these 2 entities early after AMI is difficult, but clinically important. Previous studies have shown that myocardial contrast echocardiography (MCE) and low-dose dobutamine echocardiography (DE) may both be useful in this setting. However, there are few data regarding the relative and combined value of these techniques. The aim of this study was to compare the utility of real-time intravenous MCE and low-dose DE in the early prediction of functional recovery of akinetic myocardium after AMI. Thirty-seven patients were studied 3 +/- 2 days after an AMI. Each subject underwent real-time MCE using an intravenous infusion of perflutren microbubbles. Immediately after this, low-dose DE was performed. Contrast opacification and wall motion were determined by experienced observers blinded to clinical data. Repeat echocardiograms were obtained 51 +/- 19 days later and wall motion at rest was scored by an observer blinded to clinical data. Normal contrast opacification predicted functional recovery with a positive predictive value of 63%, a negative predictive value of 73%, and an accuracy of 66%. Residual contractility during low-dose DE had a positive predictive value of 82%, a negative predictive value of 72%, and a predictive accuracy of 76%. When the 2 tests were concordant (64%), they had a positive predictive value of 81%, a negative predictive value of 85%, and a predictive accuracy of 83%. Low-dose DE was superior to intravenous MCE in the prediction of functional recovery of akinetic myocardium after AMI, but the combination of both maximizes predictive accuracy.

Myocardial contrast echocardiography in acute myocardial infarction

PURPOSE OF REVIEW

Myocardial contrast echocardiography (MCE) has evolved into an important clinical tool for imaging coronary microcirculation. It can be used to delineate the spectrum of perfusion derangements that characterize acute myocardial infarction.

RECENT FINDINGS

Presently, MCE uses microcirculatory perfusion as the basis to distinguish myocardial necrosis and viability in the post-infarct stage. Its future role may expand to image cellular integrity, inflammation, and angiogenesis, all of which contribute to the pathophysiology of the myocardial infarction.

SUMMARY

This review provides an update of the current role and future clinical applications of MCE in acute myocardial infarction.