Use of echocardiography for predicting myocardial viability in patients with reperfused anterior wall myocardial infarction

Association between integrated backscatter and arrhythmia in patients with ischemic dilated cardiomyopathy

BACKGROUND

Ventricular scars due to myocardial infarction provide a substrate for ventricular arrhythmias, and cardiac magnetic resonance (CMR) is the golden standard for the quantification of scar tissue magnitude. CMR has still limitations with patients with ICD despite ICD's becoming MR-compatible. We investigated the association between calibrated integrated backscatter (cIBS) and arrhythmia frequency in patients with ICD.

METHODS

Thirty-two ischemic dilated cardiomyopathy (ICM) patients with VVI-ICD (mean age 66.56 ± 9.05, 28 male, and four female) were divided into three groups according to their arrhythmia frequency (ventricular arrhythmia-[VA -], VA + [VA +], and arrhythmia storm [AS]). Then with transthoracic echocardiography (TTE), all patients' cIBS values were calculated and these values were compared with the patients' arrhythmia frequency.

RESULTS

cIBS values of patients with VA + and AS were significantly higher in the apical-septal (0.66 ± 0.11 vs. 0.50 ± 0.16, p = .008) and apical-lateral (0.62 ± 0.19 vs. 0.46 ± 0.18, p = .041) segments compared to those of patients with VA -. The cIBS values of apical-septal (0.50 ± 0.16 vs. 0.65 ± 0.08 vs. 0.66 ± 0.13 respectively, p = .032) and apical-anterior (0.53 ± 0.22 vs. 0.48 ± 0.17 vs. 0.79 ± 0.23 respectively, p = .03) segments were significantly different between the groups. Furthermore, in the post hoc analysis, the difference was significantly higher in VA + than VA - in the apical-septal segment and higher in AS than VA + in apical-anterior segments.

CONCLUSION

Our findings suggest an association between the cIBS values and arrhythmia frequency in the study group.

Automated assessment of myocardial viability after acute myocardial infarction by global longitudinal peak strain on low-dose dobutamine stress echocardiography

BACKGROUND

Low-dose dobutamine stress echocardiography (DSE) assesses myocardial viability at the early stage of acute myocardial infarction (AMI), but its assessment is subjective and variable. Automated function image (AFI) determines global longitudinal peak strain (GLPS) based on tissue tracking technique. The ability of GLPS obtained by AFI during dobutamine stress to assess myocardial viability after AMI was investigated.

METHODS AND RESULTS

Low-dose DSE at day 3 in 23 consecutive patients with AMI was performed using Vivid 7 (GE Healthcare). Segmental longitudinal peak strain with AFI and obtained GLPS was analyzed. Wall motion score index (WMSI) by echocardiography 1 month later was determined. In 18 patients, left ventriculography was also performed at 3.2±1.5 months later to obtain left ventricular ejection fraction (LVEF) and regional wall motion (RWM, SD/chord). GLPS was improved during dobutamine infusion at 10 µg · kg(-1) · min(-1) (-12.9 ± 3.5% to -15.2 ± 3.6%, P=0.0004). GLPS during dobutamine stress showed good correlations with follow-up WMSI (R=0.47, P=0.02), with peak CK-MB (R = 0.52, P=0.01), with RWM (R = -0.48, P=0.04), and with LVEF (R = -0.54, P=0.02), whereas GLPS at baseline showed no correlations with them. Averaged segmental peak strain at baseline and during stress were correlated with follow-up WMSI (R = 0.50 and 0.43, respectively), but not with LVEF.

CONCLUSIONS

GLPS during dobutamine stress determined by AFI is a promising, objective index to assess myocardial viability on the early stage of AMI.

Comparison of two- versus three-dimensional myocardial contrast echocardiography for assessing subendocardial perfusion abnormality after percutaneous coronary intervention in patients with acute myocardial infarction

Myocardial contrast echocardiography (MCE) visualizes myocardial perfusion abnormalities after acute myocardial infarction. However, the limited view of 2-dimensional echocardiography reduces its ability to estimate perfusion abnormalities, especially in the subendocardial region. Three-dimensional echocardiography provides images of the left ventricular endocardium directly. This study was conducted to evaluate the ability of 3-dimensional MCE to assess abnormalities of subendocardial perfusion. Intracoronary 2- and 3-dimensional MCE was performed after primary percutaneous coronary intervention in 47 patients with acute myocardial infarction. Myocardial perfusion within the risk area was evaluated as good, poor, or no reflow on 2-dimensional MCE or as good, poor, or no myocardial opacification in endocardium on 3-dimensional MCE. The 2 methods showed different distributions of perfusion patterns: good, poor, and no reflow on 2-dimensional MCE in 31 (66%), 9 (19%), and 7 (15%) patients and good, poor, and no myocardial opacification in endocardium on 3-dimensional MCE in 17 (36%), 16 (34%), and 14 (20%) patients, respectively. Although only 19 patients (61%) with good reflow on 2-dimensional MCE showed myocardial perfusion grade 3 on angiography, 16 of 17 patients (94%) with good myocardial opacification in endocardium on 3-dimensional MCE showed myocardial perfusion grade 3. Although there were no significant differences in peak creatine kinase among the 3 subsets classified by 2-dimensional MCE, peak creatine kinase showed significant differences not only among the 3 groups but also among the subsets classified by 3-dimensional MCE. Classification by 3-dimensional MCE also predicted regional wall motion after 4.6 +/- 2.7 months, with significant differences between each pair of groups, whereas there was significant overlap of these values between the group with poor reflow and other 2 groups by 2-dimensional MCE. In conclusion, 3-dimensional MCE is a feasible way to assess subendocardial perfusion and predicts infarct size and functional recovery more precisely than 2-dimensional MCE.

Contrast-enhanced intravascular ultrasound: combining morphology with activity-based assessment of plaque vulnerability

Acute coronary syndromes are the result of coronary plaque rupture in the majority of cases. Available diagnostic techniques that focus on the early detection of plaques that are prone to rupture are still limited. Increased neovascularization in the vasa vasorum of the atherosclerotic plaque has been identified recently as a common feature of inflammation and plaque vulnerability. Microbubbles, which have been used for ultrasound imaging, can be used to trace neovascularization. We present recent advances in contrast agents and contrast-enhanced intravascular ultrasound that may be used for the detection of vasa vasorum, including fundamental and harmonic contrast imaging. Identification of vasa vasorum proliferation in atherosclerotic plaques presents important clinical implications; in particular it could provide a means to detect vulnerability in vivo, thereby guiding targeted treatments.

Integrated backscatter for the assessment of myocardial viability

PURPOSE OF REVIEW

Ultrasonic tissue characterization is a non-invasive diagnostic method that uses myocardial integrated backscatter analysis to determine contractile performance and myocardial viability independent of wall motion. This review discusses recent clinical findings regarding the application of ultrasonic tissue characterization for the assessment of myocardial viability.

RECENT FINDINGS

As this technique is non-invasive, ultrasonic tissue characterization can be used to predict the patency of infarct-related arteries in patients in the early stage of acute myocardial infarction. Several recent studies have shown that this technique is useful in identifying myocardial contractile reserve. The accuracy of ultrasonic tissue characterization for predicting functional recovery after coronary reperfusion is comparable to dobutamine echocardiography and radionuclide methods. Several studies have suggested that the cyclic variation of myocardial integrated backscatter reflects myocardial viability rather than contractile reserve. The cyclic variation of integrated backscatter is associated with myocardial viability confirmed by the integrity of the microvasculature identified by contrast echocardiography. In addition, the cyclic variation of integrated backscatter better reflects myocardial viability confirmed by the integrity of cellar metabolism than contractile reserve.

SUMMARY

Ultrasonic tissue characterization with integrated backscatter is a useful non-invasive method that can provide unique information for the assessment of myocardial viability.

Prediction of the no-reflow phenomenon with ultrasonic tissue characterization in patients with anterior wall acute myocardial infarction

The no-reflow phenomenon after acute myocardial infarction seems to be related to ischemic injury before reperfusion. Analyzing cardiac cycle-dependent variation of integrated backscatter (IBS) is a unique method to assess myocardial viability. In this study, the ability of ultrasonic tissue characterization with IBS to predict the no-reflow phenomenon was investigated in 90 patients with first anterior wall infarction who underwent successful primary percutaneous coronary intervention. IBS images were recorded on admission (before reperfusion), and the magnitude of the cyclic variation of IBS within the infarct zone was expressed as phase-corrected magnitude (PCM) by giving positive and negative values when it showed synchronous and asynchronous contraction, respectively. Myocardial contrast echocardiography was performed soon after reperfusion, and 21 patients showed substantial no-reflow. They had smaller PCM before reperfusion than patients without no-reflow (-1.6 +/- 1.9 vs 0.7 +/- 2.7 dB, respectively; p = 0.0002). Multivariate logistic regression analysis revealed that PCM before reperfusion and the number of Q waves were the independent predictors of no reflow. Using -1.0 dB as the cut-off point, PCM predicted no reflow with 66.7% sensitivity and 81.2% specificity. These results indicate that the analysis of myocardial IBS could predict the no-reflow phenomenon before reperfusion.

Pharmacological prevention of reperfusion injury in acute myocardial infarction. A potential role for adenosine as a therapeutic agent

The concept of reperfusion injury, although first recognized from animal studies, is now recognized as a clinical phenomenon that may result in microvascular damage, no-reflow phenomenon, myocardial stunning, myocardial hibernation and ischemic preconditioning. The final consequence of this event is left ventricular (LV) systolic dysfunction leading to increased morbidity and mortality. The typical clinical case of reperfusion injury occurs in acute myocardial infarction (MI) with ST segment elevation in which an occlusion of a major epicardial coronary artery is followed by recanalization of the artery. This may occur either spontaneously or by means of thrombolysis and/or by primary percutaneous coronary intervention (PCI) with efficient platelet inhibition by aspirin (acetylsalicylic acid), clopidogrel and glycoprotein IIb/IIIa inhibitors. Although the pathophysiology of reperfusion injury is complex, the major role that neutrophils play in this process is well known. Neutrophils generate free radicals, degranulation products, arachidonic acid metabolites and platelet-activating factors that interact with endothelial cells, inducing endothelial injury and neutralization of nitrous oxide vasodilator capacity. Adenosine, through its multi-targeted pharmacological actions, is able to inhibit some of the above-mentioned detrimental effects. The net protective of adenosine in in vivo models of reperfusion injury is the reduction of the infarct size, the improvement of the regional myocardial blood flow and of the regional function of the ischemic area. Additionally, adenosine preserves the post-ischemic coronary flow reserve, coronary blood flow and the post-ischemic regional contractility. In small-scale studies in patients with acute MI, treatment with adenosine has been associated with smaller infarcts, less no-reflow phenomenon and improved LV function. During elective PCI adenosine reduced ST segment shifts, lactate production and ischemic symptoms. During the last years, three relatively large placebo-controlled clinical trials have been conducted: Acute Myocardial Infarction Study of Adenosine Trial (AMISTAD) I and II and Attenuation by Adenosine of Cardiac Complications (ATTACC). In the AMISTAD trials, the final infarct size was reduced and the LV systolic function was improved by adenosine treatment, mainly in patients with anterior MI localization. However, morbidity and mortality were not affected. In the ATTACC study, the LV systolic function was not affected by adenosine, however, trends towards improved survival were observed in patients with anterior MI localization. The possibility of obtaining a Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow in the infarct-related artery in up to 95% of patients with acute MI (increasing the occurrence of reperfusion injury) has turned back the interest towards the protection of myocardial cells from the impending ischemic and reperfusion injury in which adenosine alone or together with other cardio-protective agents may exert important clinical effects.

Detection of TIMI-3 flow before mechanical reperfusion with ultrasonic tissue characterization in patients with anterior wall acute myocardial infarction

BACKGROUND

Spontaneous coronary reperfusion with TIMI-3 flow is associated with favorable clinical outcomes in patients with acute myocardial infarction (AMI). We investigated the ability of analyzing cardiac cycle-dependent variation of myocardial integrated backscatter (IBS) for predicting spontaneous reperfusion in anterior AMI.

METHODS AND RESULTS

We recorded IBS images on admission in 104 patients with first anterior wall AMI and subsequently performed coronary angiography and coronary intervention. We measured the cyclic variation of IBS within the infarct zone and expressed its magnitude as phase-corrected magnitude (PCM) by giving positive and negative values when it showed synchronous and asynchronous contraction, respectively. Twenty-three patients showing TIMI-3 flow at the initial coronary angiography had smaller peak creatine kinase value than 57 patients with initial TIMI-0/1 flow (864+/-961 versus 2358+/-1757 IU/L; P=0.0002) and better percent wall thickening within risk area (36.1+/-15.1%) than those with TIMI-2 (16.7+/-12.8%, P<0.0001) or TIMI-0/1 (5.1+/-11.6, P<0.0001). The patients with initial TIMI-3 had higher PCM (2.7+/-1.3 dB) than those with TIMI-2 (-0.3+/-2.2 dB, P<0.0001) or those with TIMI-0/1 (-1.1+/-2.4 dB, P<0.0001). Using PCM=1.0 dB as the cutoff point, PCM detected TIMI-3 flow with 95.7% sensitivity and 90.1% specificity. Multivariable logistic regression analysis revealed that only PCM is an independent predictor for spontaneous reperfusion among the hemodynamic, echocardiographic, and electrocardiographic variables.

CONCLUSIONS

Analysis of myocardial IBS could detect spontaneous reperfusion noninvasively in the emergent stage of anterior AMI.

Alterations of myocardial ultrasonic tissue characterization by coronary angioplasty in patients with chronic stable coronary artery disease

We conducted a study to delineate the alterations in the cyclic changes of myocardial ultrasonic integrated backscatter (IBS) in patients receiving angioplasty for chronic coronary artery disease. Ultrasonic tissue characterization (UTC) and dobutamine stress echocardiography were performed in 43 patients before and 24 h after angioplasty, as well as before the follow-up angiography 3 months later. For segments being normokinetic with ischemic burden, the blunted amplitude and increased nadir deviation of IBS cyclic modulation recovered soon after angioplasty. For dyssynergic segments with contractile reserve, the angioplasty rebuilt the amplitude before the wall motion recovered, but corrected the nadir deviation tardily. In both circumstances, the coronary restenosis abolished the initial restoration. Those nonviable segments persistently revealed large deviations and small weighted amplitudes irrelevant to coronary lesions. The progress of myocardial ischemia, the development of wall motion dyssynergy and, then, the loss of viability, show different patterns of alterations in UTC after alleviating coronary obstructions.

Recent advances in myocardial contrast echocardiography

Myocardial contrast echocardiography (MCE) has undergone many advances in the past several years through remarkable developments in contrast agent and ultrasound equipment technology. Microbubble ultrasound contrast agents can now safely transit the pulmonary circulation to provide opacification of the left ventricular cavity, improved endocardial border definition, and detection of myocardial perfusion. The role of contrast echocardiography in enhancing technically difficult images is now well established in clinical practice, and has proven especially useful in the stress and intensive care unit settings. Major progress has been made in the application of MCE for myocardial perfusion assessment in acute and chronic ischemic heart disease syndromes, and comprises the focus of this review. Advances in novel applications of contrast echocardiography, including targeted delivery of genetic and pharmaceutical materials, have also occurred, but remain in a preclinical phase. In summary, the combination of recent innovations in ultrasound equipment, and microbubble acoustics, allows for exciting exploration of the expanding role of contrast echocardiography in clinical practice.