Myocardial salvage: its assessment and prediction by the analysis of serial myocardial contrast echocardiograms in patients with acute myocardial infarction

Effect of Intravenous Administration of Liposomal Prostaglandin E1 on Microcirculation in Patients with ST Elevation Myocardial Infarction Undergoing Primary Percutaneous Intervention

Background:

Several studies have demonstrated that primary percutaneous coronary intervention (PCI) can result in reperfusion injury. This study aims to investigate the effectiveness of liposomal prostaglandin E1 (Lipo-PGE1, Alprostadil, Beijing Tide Pharmaceutical Co., Ltd.) for enhancing microcirculation in reperfusion injury. In addition, this study determined the optimal administration method for acute ST elevation myocardial infarction (STEMI) patients undergoing primary PCI.

Methods:

Totally, 68 patients with STEMI were randomly assigned to two groups: intravenous administration of Lipo-PGE1 (Group A), and no Lipo-PGE1 administration (Group B). The corrected thrombolysis in myocardial infarction (TIMI) frame count (cTFC) and myocardial blush grade (MBG) were calculated. Patients were followed up for 6 months. Major adverse cardiac events (MACE) were also measured.

Results:

There was no significant difference in the baseline characteristics between the two groups. The cTFC parameter in Group A was significantly lower than Group B (18.06 ± 2.06 vs. 25.31 ± 2.59, P < 0.01). The ratio of final MBG grade-3 was significantly higher (P < 0.05) in Group A (87.9%) relative to Group B (65.7%). There was no significant difference between the two groups in final TIMI-3 flow and no-reflow. Patients were followed up for 6 months, and the occurrence of MACE in Group A was significantly lower than that in Group B (6.1% vs. 25.9% respectively, P < 0.05).

Conclusions:

Myocardial microcirculation of reperfusion injury in patients with STEMI, after primary PCI, can be improved by administering Lipo-PGE1.

Effect of microvascular obstruction and intramyocardial hemorrhage by CMR on LV remodeling and outcomes after myocardial infarction: a systematic review and meta-analysis

The goal of this systematic analysis is to provide a comprehensive review of the current cardiac magnetic resonance data on microvascular obstruction (MVO) and intramyocardial hemorrhage (IMH). Data related to the association of MVO and IMH in patients with acute myocardial infarction (MI) with left ventricular (LV) function, volumes, adverse LV remodeling, and major adverse cardiac events (MACE) were critically analyzed. MVO is associated with a lower ejection fraction, increased ventricular volumes and infarct size, and a greater risk of MACE. Late MVO is shown to be a stronger prognostic marker for MACE and cardiac death, recurrent MI, congestive heart failure/heart failure hospitalization, and follow-up LV end-systolic volumes than early MVO. IMH is associated with LV remodeling and MACE on pooled analysis, but because of limited data and heterogeneity in study methodology, the effects of IMH on remodeling require further investigation.

Nicorandil in patients with acute myocardial infarction undergoing primary percutaneous coronary intervention: a systematic review and meta-analysis

Background

Nicorandil, as an adjunctive therapy with primary percutaneous coronary intervention (PCI), had controversial benefits in cardioprotection in patients with acute myocardial infarction (AMI).

Methods and Results

We performed a systematic review of randomized controlled trials (RCTs) comparing treatment with nicorandil prior to reperfusion therapy with control (placebo or no nicorandil) in patients who suffered from AMI and performed primary PCI. PubMed, EMBASE and CENTRAL databases and other sources were searched without language and publication restriction. 14 trials involving 1680 patients were included into this meta-analysis. Nicorandil significantly reduced the incidence of thrombolysis in myocardial infarction (TIMI) flow grade ≤2 (risk ratio [RR], 0.57; 95% confidence interval [CI]: 0.42 to 0.79), the Timi frame count (TFC) (mean difference [MD], -5.19; 95% CI: -7.13 to -3.26), increased left ventricular ejection fraction (LVEF) (%) (MD, 3.08; 95% CI: 0.79 to 5.36), and reduced the incidence of ventricular arrhythmia (RR, 0.53; 95% CI: 0.37 to 0.76) and congestive heart failure (CHF) (RR, 0.41; 95% CI: 0.22 to 0.75). No difference in the pear creatine kinase (CK) value (MD, -290.19; 95% CI: -793.75 to 213.36) or cardiac death (RR, 0.39; 95% CI: 0.09 to 1.67) was observed.

Conclusions

Nicorandil prior to reperfusion is associated with improvement of coronary reflow as well as suppression of ventricular arrhythmia, and further improves left ventricular function in patients who suffered from AMI and underwent primary PCI. But the definite clinical benefits of nicorandil were not found, which may be due to the small sample size of the selected studies.

Preservation of myocardial viability within the risk area by intravenous nicorandil before primary coronary intervention in patients with acute myocardial infarction

OBJECTIVE

To investigate the cardioprotective effect of intravenous nicorandil before primary percutaneous coronary intervention (PCI) on preservation of myocardial viability, we studied 199 consecutive patients with acute myocardial infarction.

METHODS

Nicorandil was given intravenously on admission (before primary PCI). Echocardiography and technetium-99m tetrofosmin perfusion imaging were performed before and 1 month after primary PCI. Echocardiographic asynergic score before primary PCI was used to define the size of risk area, whereas the sum of scintigraphic defect grade before primary PCI was used to estimate myocardial viability within the area at risk. The change (before primary PCI and 1 month after primary PCI) in asynergic score and scintigraphic salvage index were calculated.

RESULTS

Patients were divided into nicorandil (n=101) and control (n=98) groups. Although asynergic score before primary PCI was not different between the two groups (nicorandil=3.5+/-2.1 and control=3.9+/-1.5), myocardial viability was preserved in nicorandil group (defect score=11.0+/-4.0) than that in control group (defect score=14.0+/-4.7, P<0.0001). Multivariate analysis revealed that the presence of antegrade flow (P=0.015) and nicorandil (P<0.0001) were independently associated with preserved myocardial viability before primary PCI. Moreover, the greater reduction in asynergic score (66+/-41 vs. 49+/-23%, P=0.0006) and larger salvage index (65+/-25 vs. 53+/-26%, P=0.0015) were observed in nicorandil group compared with the control group.

CONCLUSION

Intravenous administration of nicorandil before primary PCI preserved myocardial viability within the risk area, which leads to greater myocardial salvage and better functional recovery after primary PCI.

Current role of contrast echocardiography in the diagnosis of cardiovascular diseases

The use of contrast echocardiography (CE) in cardiovascular medicine has grown significantly over the last 15 years. Depending on the site of injection, contrast enhancement of the right- or left-sided cardiac chambers or myocardium now can be achieved. Contrast echocardiography can improve the evaluation of patients with valvular heart disease by enhancing the Doppler signal; CE also improves detection of intracardiac or intrapulmonary shunts. In patients with coronary artery disease, enhancement of the endocardial blood-tissue boundary allows for improved visualization of endocardial wall motion, assessment of wall thickening, and calculation of ejection fraction. Contrast echocardiography promises to delineate myocardial perfusion and has the potential for quantitating coronary flow and assessing myocardial viability. These applications may add important physiologic information to the anatomic information readily available from noncontrast echocardiography. Because it can be rapidly performed at the bedside, CE may be a valuable tool for use with inpatients with acute myocardial ischemia. When CE has been used after recanalization of occluded coronary arteries, the assessment of myocardial salvage conveys information concerning reflow, stunning, and prognosis, and in the case of an angioplasty it provides immediate information regarding the success of the procedure. Contrast echocardiography can also assess myocardial areas at risk of irreversible damage and the presence or absence of collateral flow. When performed with transesophageal or epicardial echocardiography in the operating room, CE is emerging as a valuable tool in the assessment of cardioplegia distribution and graft patency as well as in the delineation of the regional supply of each graft. With the continued development of newer contrast agents and refinement of ultrasound imaging equipment, the applications of CE will continue to grow.

Impact of Nicorandil to Prevent Reperfusion Injury in Patients With Acute Myocardial Infarction Sigmart Multicenter Angioplasty Revascularization Trial (SMART)

BACKGROUND

Nicorandil in conjunction with percutaneous coronary intervention (PCI) has been reported to reduce reperfusion injury events and improve cardiac function in patients with acute myocardial infarction (AMI). This multicenter study was undertaken to determine the effectiveness and optimal administration of nicorandil in AMI patients.

METHODS AND RESULTS

Ninety-two patients with first AMI were randomly assigned to 1 of 3 groups: intracoronary administration of nicorandil (Group A), combined intravenous and intracoronary administration of nicorandil (Group B), and no nicorandil administration (Group C). The primary endpoint was a composite of the incidence of reperfusion-induced arrhythmia, chest pain, and no-reflow/slow-reflow. The secondary endpoint was the combined rate of improvement in the Thrombolysis in Myocardial Infarction frame count (cTFC) and ST resolution (STR). A significant difference was observed in the primary endpoint for Group B as compared with Group C (p<0.05). In the meantime, a significant improvement was shown in the secondary endpoint for Group B compared with Group C (p=0.04 and 0.006 for cTFC and STR, respectively).

CONCLUSIONS

Combined intravenous and intracoronary administration of nicorandil reduces reperfusion injury during PCI and improves the cTFC and STR in AMI, and appears to be preferable to intracoronary administration alone.

Nicorandil improves cardiac function and clinical outcome in patients with acute myocardial infarction undergoing primary percutaneous coronary intervention: role of inhibitory effect on reactive oxygen species formation

BACKGROUND

Early reperfusion therapy improves the clinical outcomes of patients with acute myocardial infarction (AMI), but benefits are limited by reperfusion injury in some patients. We examined the effect of nicorandil, a hybrid of K(ATP) channel opener and nicotinamide nitrate, on reactive oxygen species (ROS) formation and clinical outcomes after primary percutaneous coronary intervention (PCI) for AMI.

METHODS

Fifty-eight patients with AMI were randomized into control (n = 25) and nicorandil pretreatment groups (n = 33). In the nicorandil group, nicorandil (4 mg as a bolus injection followed by constant infusion at 8 mg/hour for 24 hours) was administered just after admission. ROS formation was assessed by measuring urinary excretion of 8-epi-prostaglandin F2alpha (PGF2alpha) and compared between the 2 groups. Cardiac function and the incidence of reperfusion injury and cardiac events were also compared.

RESULTS

Urinary 8-epi-PGF2alpha excretion was increased 2-fold at 60 to 90 minutes after PCI in the control group, whereas it was unchanged after PCI in the nicorandil group (P <.0001 between the 2 groups). The incidence of no-reflow phenomenon was lower in the nicorandil group than in the control group. Left ventricular ejection fraction and cardiac index at 6 months were greater in the nicorandil group than in controls. Plasma brain natriuretic peptide level at 6 months was lower in the nicorandil group. Incidences of inhospital cardiac events and rehospitalization were lower in the nicorandil group than in controls.

CONCLUSIONS

Nicorandil improves cardiac function and clinical outcomes in patients with AMI. Suppression of ROS formation may be involved in the mechanism.

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

Akinesia after acute myocardial infarction (MI) may be reversible, secondary to stunning, or irreversible, as a result of extensive myocyte necrosis. Distinguishing these 2 entities soon after MI is difficult, but has important clinical implications. The current study assessed the use of intravenous myocardial contrast echocardiography (MCE) in this setting. A total of 35 patients were studied 2 (+/- 1) days after an acute MI. Of these, 31 (91%) underwent myocardial revascularization. Perfusion was assessed using real-time MCE and an intravenous infusion of octafluoropropane microbubbles. Repeated echocardiograms were obtained 56 (+/- 29) days later. Normal perfusion predicted functional recovery with a positive predictive value of 66% and a negative predictive value of 81%. The accuracy of the technique was superior in myocardial segments supplied by the left anterior descending coronary artery (positive and negative predictive value: 70% and 90%, respectively). In multivariable analysis, the mean MCE perfusion score in akinetic segments was the most powerful independent predictor of functional recovery (odds ratio 8.6, P =.02). These data suggest that real-time intravenous MCE is a useful predictor of functional recovery of akinetic myocardium after acute MI.

Quantitative estimation of myocardial salvage after primary percutaneous transluminal coronary angioplasty in patients with angiographic no reflow

Angiographic Thrombolysis in Myocardial Infarction (TIMI) flow grade <or=2 after primary percutaneous transluminal coronary angioplasty (PTCA), defined as angiographic no reflow, predicts poor left ventricular functional recovery and survival in patients with acute myocardial infarction (MI). To determine the relation between angiographic coronary flow and myocardial salvage in the acute phase of MI, serial technetium-99m tetrofosmin imaging was performed before, immediately after and 1 month after PTCA in 117 patients. Angiographic no reflow was observed in 23 patients (20%; group 1), while 94 patients did not have angiographic no reflow (group 2). Although there was no significant difference in the defect score before PTCA between the two groups (group 1, 14.4+/-5.7; group 2, 13.5+/-4.6), the defect score immediately after PTCA in group 1 was significantly higher than that in group 2 (group 1, 12.8+/-5.1; group 2, 8.9+/-4.6; P<0.0001). A significantly smaller change in the defect score after PTCA (before minus immediately after PTCA) was observed in group 1 as compared with group 2 (group 1, 1.7+/-2.0; group 2, 4.5+/-2.9; P<0.0001). Twenty patients in group 1 (87%) had impaired myocardial reperfusion (<4 change in the defect score immediately after PTCA), as compared with 36 patients (38%) in group 2; this difference was significant (chi(2)=17.5, P<0.0001). The sensitivity, specificity and accuracy of angiographic no reflow in estimating impaired myocardial reperfusion were 36%, 95% and 67%, respectively. Thus, angiographic no reflow is a highly specific, although not sensitive, marker of impaired myocardial reperfusion immediately after primary PTCA.

[Prognostic value of persistent ST-segment elevation after successful primary angioplasty]

INTRODUCTION AND OBJECTIVES

A variable percentage of patients with myocardial infarction treated with successful primary angioplasty and restoration of coronary flow show persistent ST-segment elevation, probably due to inadequate cellular reperfusion. We studied if persistent ST-segment elevation was a predictor of worse prognosis.

PATIENTS AND METHODS

We comparatively studied the clinical and angiographic results of 116 acute myocardial infarction patients after successful primary angioplasty, which were classified into two groups depending on the persistence (> 50%) or reduction (</= 50%) of ST-segment elevation between the electrocardiograms recorded before and after coronary angioplasty.

RESULTS

In 96 patients (Group I) the ST-segment elevation improved after angioplasty and in 20 patients (Group II) there was no improvement. Baseline characteristics were similar in both groups except for Killip class 4, which was more prevalent in group II (7.2 vs. 25%; p = 0.01). There were no differences in the characteristics or results of the procedure. There was more myocardial damage in group II (CK 3,149 1,636 vs. 2,185 2,010 U/l; p = 0.02), associated with a more impaired left ventricular ejection fraction in the late angiographic control (47 16 vs 55 16%; p = 0.05). At a one-year follow-up the mortality was 8.3% in group I and 30% in group II (p = 0.01).

CONCLUSIONS

The persistence of ST-segment elevation after successful primary angioplasty identifies a group of patients that may suffer an increased risk of adverse events in spite of good epicardial flow.

Dynamic change in collateral flow associated with myocardial ischemia in humans

BACKGROUND

This study sought to investigate how collateral flow changes during myocardial ischemia in patients.

METHODS

Myocardial contrast echocardiography (MCE) and rapid atrial pacing were performed in 20 patients with angiographically evidenced coronary collaterals from the right coronary artery (RCA) to the occluded left anterior descending coronary artery. Sonicated contrast medium was injected into the RCA before and immediately after atrial pacing to determine the peak background-subtracted contrast intensity (PI) in the collateral territory (PIA) and its ratio to PI in the control territory (PI ratio) as parameters of collateral blood flow. Lactate production in the coronary circulation during pacing was determined to assess myocardial ischemia in the collateral territory.

RESULTS

PIA showed a significant correlation with regional wall motion either before (r(squared)=-0.64, P<0.01) or after pacing (r(squared)=-0.65, P<0.01). Similarly, PI ratio was significantly correlated with regional wall motion either before (r(squared)=-0.54, P<0.05) or after pacing (r(squared)=-0.64, P<0.01). Rapid atrial pacing decreased both PIA and PI ratio significantly greater in patients with lactate production than in those without (PIA: -67+/-53 vs. -15+/-34%, P<0.05; PI ratio: -68+/-49 vs. -8.2+/-32%, P<0.05, respectively), while neither PIA nor PI ratio differ between the two groups of patients before pacing (PIA: 13.8+/-19. vs. 16.2+/-13.3U, P=0.75; PI ratio: 0.70+/-0.71 vs. 0.87+/-0.65, P=0.58, respectively).

CONCLUSIONS

We concluded that (1) collateral flow determined by MCE was closely associated with regional cardiac function, and (2) not the amount of collateral flow at rest, but pacing-induced change of collateral flow seemed to be a determinant of regional ischemia in patients with coronary collaterals.

Coronary flow reserve is reflective of myocardial perfusion status in acute anterior myocardial infarction

Our objective was to determine whether coronary vasodilatory reserve (CVR) correlates with the perfusion state of infarct zone in early recovery phase of acute anterior myocardial infarction (AMI). We studied 14 patients (11 males; mean age, 46 years) who had AMI and 6 control subjects who had chest pain but normal coronary angiograms. All patients underwent successful percutaneous revascularization of left anterior descending (LAD) coronary artery. Coronary flow velocity was measured using intracoronary (IC) Doppler at baseline and following IC injection of 18 microg of adenosine. Myocardial perfusion was evaluated by myocardial contrast echocardiography (MCE). CVR was higher in patients without a perfusion defect on MCE than in those with (2.48 +/- 0.21 vs. 1.66 +/- 0.13, P = 0.001). Subjects with a perfusion defect had a lower CVR than controls (1.66 +/- 0.13 vs.2.40 +/- 0.18, P < 0.05). CVR was > 2.0 in all subjects without a perfusion defect. There was a strong correlation between the magnitude of myocardial opacification in the LAD territory and CVR (r = 0.80, P < 0.01). Increase in peak diastolic flow velocity after adenosine infusion, but not systolic flow velocity, correlated with myocardial opacification index (r = 0.63, P = 0.016). CVR of infarct-related artery correlated closely with the perfusion status of the myocardium in infarct zone and those with a CVR > 2.0 had normal myocardial perfusion. These data suggest that CVR may be used to determine the perfusion state of the myocardium in the infarct zone, which is a known predictor of myocardial viability. Cathet. Cardiovasc. Intervent. 51:281-286, 2000.

In vitro flow quantification with contrast power Doppler imaging

To evaluate the effectiveness of contrast harmonic (power Doppler imaging) as an ultrasonic modality to quantify flow, an in vitro model of perfusion was studied using Optison, a second-generation ultrasound (US) contrast agent. The in vitro model was made of two dialysis cartridges placed parallel and allowed absolute and relative flow quantification on both tube (entry lines) and tissue (cartridges) simulations. Video intensity curves were generated using intermittent harmonic power Doppler imaging after bolus injection of contrast. Correlation between flow and different parameters extracted from time-intensity curves and previously defined as indicators of flow was established for both tissue and entry lines, for flow rates ranging from 0 to 400 mL/min. Single-compartment equations were also tested on the model. A good correlation for the tissue model was observed between absolute flow and onset time (O), time to maximal enhancement (TME), peak intensity (P), area under the curve (AUC), and maximal ascending slope (S) parameters, with a r = 0.94, 0.94, 0.91, 0.92 and 0.92, respectively. The correlation for O, TME, P and AUC parameters was r = 0.86, 0.90, 0.78 and 0.82, respectively for entry lines. The correlation for tissue model and entry line was slightly improved when comparing flow ratios with peak ratios (P1/P2) and slope ratios (S1/S2) (r = 0.95 and 0.94). Flow calculation using the gradient-relationship method also showed a good correlation (r = 0.88) with the experimental flow. The results obtained indicated that absolute and relative quantification of flow using PDI is feasible in tube and tissue models. Several clinical applications, namely in myocardial, hepatic and renal artery studies, could be derived from these results.

The significance of persistent ST elevation versus early resolution of ST segment elevation after primary PTCA

OBJECTIVES

To determine the prevalence and clinical significance of early ST segment elevation resolution after primary percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction (AMI).

BACKGROUND

Despite angiographically successful restoration of coronary flow early during AMI, adequate myocardial reperfusion might not occur in a substantial portion of the jeopardized myocardium due to microvascular damage. This phenomenon comprises the potentially beneficial effect of early recanalization of the infarct related artery (IRA).

METHODS

Included in the study were 117 consecutive patients who underwent angiographically successful [Thrombolysis in Myocardial Infarction (TIMI III)] primary PTCA. The patients were classified based on the presence or absence of reduction > or =50% in ST segment elevation in an ECG performed immediately upon return to the intensive cardiac care unit after the PTCA in comparison with ECG before the intervention.

RESULTS

Eighty-nine patients (76%) had early ST segment elevation resolution (Group A) and 28 patients (24%) did not (Group B). Group A and B had similar clinical and hemodynamic features before referring to primary PTCA, as well as similar angiographic results. Despite this, ST segment elevation resolution was associated with better predischarge left ventricular ejection fraction (LVEF) (44.7 +/- 8.0 vs. 38.2 +/- 8.5, p < 0.01). Group B patients, as compared with those of Group A, had a higher incidence of in-hospital mortality (11% vs. 2%, p = 0.088), congestive heart failure (CHF) [28% vs. 19%, odds ratio (OR) = 4, 95% confidence interval (CI) 1 to 15, p = 0.04], higher long-term mortality (OR = 7.3, 95% CI 1.9 to 28, p = 0.004 with Cox proportional hazard regression analysis) and long-term CHF rate (OR = 6.5, 95% CI 1.3 to 33, p = 0.016 with logistic regression).

CONCLUSIONS

Absence of early ST segment elevation resolution after angiographically successful primary PTCA identifies patients who are less likely to benefit from the early restoration of flow in the IRA, probably because of microvascular damage and subsequently less myocardial salvage.

Microvascular integrity after reperfusion therapy

Several perfusion techniques have definitively shown that microvascular dysfunction plays a crucial role in patients with acute myocardial infarction. In those patients, despite a rapid and sustained restoration of flow throughout a previously occluded epicardial coronary artery, microvascular damage still may be observed. Duration of ischemia and/or time to recanalization are the most powerful determinants of microvascular dysfunction. However, the amount of tissue perfusion in infarcted patients is dependent on many other complex interrelated factors including extent of collateral circulation before recanalization, residual stenosis severity of the culprit artery, vasodilator reserve in the infarct territory, extent of reperfusion injury, and loading conditions. Because microvascular dysfunction is associated with progressive left ventricular dilation and a high frequency of postinfarction complications, all of the efforts to improve the relation between coronary reflow and microvascular perfusion are justified.

Early changes in myocardial perfusion patterns after myocardial infarction: relation with contractile reserve and functional recovery

OBJECTIVES

The purpose of this study was to assess early temporal changes in myocardial perfusion pattern by myocardial contrast echocardiography (MCE) and their relation to myocardial viability in patients with reperfused acute myocardial infarction (AMI).

BACKGROUND

Myocardial contrast echocardiography no-reflow is associated with poor contractile recovery after AMI. However, little is known regarding early reversibility of microvascular dysfunction and its relation to myocardial viability.

METHODS

Intracoronary MCE was performed immediately after reflow and 9 days later in 28 patients with a first AMI and successful coronary recanalization (Thrombolysis in Myocardial Infarction trial grade 3 flow). Semiquantitative contrast score and wall motion score (WMS) were assessed in each initially asynergic segment at initial and repeat MCE study. Low dose dobutamine echocardiography (DE) was performed at day 10, and follow-up (FU) rest echocardiography was performed 6 weeks later.

RESULTS

Among 200 initially asynergic segments, 49% exhibited no or heterogeneous contrast enhancement at initial MCE versus 24% at restudy (p < 0.001). Three groups of segments were defined according to early changes in contrast pattern: group A, "sustained no-reflow" (n = 17); group B, improved contrast score (n = 68), and group C, "sustained reflow" (n = 112). Group A segments showed no improvement in WMS at FU. In contrast, group B segments showed significant improvement in WMS at FU (p < 0.0001), and exhibited more frequently contractile reserve at DE (36% vs. 6%, p = 0.02) and contractile recovery at FU (34% vs. 7%, p = 0.03) than group A segments. Group C segments exhibited contractile reserve and contractile recovery in 47% and 51% of segments respectively.

CONCLUSIONS

Improvement in MCE perfusion pattern may occur after initial no-reflow in the days following reperfused AMI and is associated with preservation of contractile reserve and gradual regional functional recovery.

Relation between ST-segment changes and myocardial perfusion evaluated by myocardial contrast echocardiography in patients with acute myocardial infarction treated with direct angioplasty

The aim of this study was to evaluate the relation between myocardial perfusion and ST-segment changes in patients with acute myocardial infarction treated with successful direct angioplasty. Thirty-seven patients, successfully treated with direct angioplasty, underwent myocardial contrast echocardiography before and after angioplasty. The sum of ST-segment elevation divided by the number of the leads involved (ST-segment elevation index) was calculated at 1, 5, 10, 20, and 30 minutes after restoration of a Thrombolysis In Myocardial Infarction trial grade 3 flow. After recanalization, myocardial reperfusion within the risk area was observed in 26 patients, whereas a no-reflow phenomenon occurred in 11. In patients with myocardial reperfusion, the ST-segment elevation index progressively declined, whereas in patients with no reflow, no significant change was observed. Reduction of > or = 50% in the ST-segment elevation index occurred in 20 of the 26 patients with reflow and in 1 of the 11 with no reflow (p = 0.0002). An additional increase of > or = 30% in the ST-segment elevation index occurred in 3 patients with reflow and in 7 with no reflow (p = 0.003). Sensitivity, specificity, positive and negative predictive values, and accuracy of the reduction in the ST-segment elevation index for predicting microvascular reflow were 77%, 91%, 95%, 62%, and 81%, respectively. The corresponding values of the increase in ST-segment elevation index for predicting no reflow were 64%, 88%, 70%, 85%, and 81%, respectively. In conclusion, after successful angioplasty, different patterns of myocardial perfusion are associated with different ST-segment changes. Analysis of ST-segment changes predicts the degree of myocardial reperfusion.

Evaluation of dynamic changes in microvascular flow during ischemia-reperfusion by myocardial contrast echocardiography

BACKGROUND

Dynamic changes of myocardial blood flow have been observed after reperfusion of an occluded coronary artery. MCE performed by intracoronary contrast injection can provide an estimate of microvascular flow. We hypothesized that MCE performed using intravenous infusion of a new generation contrast agent and electrocardiogram-gated harmonic imaging would be able to assess serial changes of microvascular perfusion.

OBJECTIVE

To study the potential of myocardial contrast echocardiography (MCE) to assess serial changes of microvascular flow during ischemia-reperfusion.

METHODS

Sixteen dogs underwent 90 or 180 min of left anterior descending coronary occlusion, followed by 180 min of reperfusion. Regional blood flow (RBF) was measured with fluorescent microspheres at baseline, during coronary occlusion, and at 5, 30, 90, and 180 min during reperfusion. At the same time points, MCE was performed with intravenous infusion of AF0150 (4 mg/min). Gated end-systolic images in short axis were acquired in harmonic mode and digitized on-line. Background-subtracted videointensity measured from MCE and RBF obtained from fluorescent microspheres were calculated for the risk area and for a control area, and were expressed as the ratio of the two areas.

RESULTS

After initial hyperemia, a progressive reduction in flow was observed during reperfusion. MCE correctly detected the time course of changes in flow during occlusion-reperfusion. Videointensity ratio significantly correlated with RBF data (r=0.79; p < 0.0001).

CONCLUSIONS

The progressive reduction in blood flow occurring within the postischemic microcirculation was accurately detected by MCE. This approach has potential application in the evaluation and management of postischemic reperfusion in humans.

Three-dimensional myocardial contrast echocardiography: validation of in vivo risk and infarct volumes

OBJECTIVES

The aim of this study was to determine whether three-dimensional (3D) myocardial contrast echocardiography (MCE) could provide an accurate in vivo assessment of risk and infarct volumes.

BACKGROUND

MCE has been shown to accurately define risk area and infarct size in single tomographic slices. The ability of this technique to measure risk and infarct volumes by using three-dimensional echocardiography (3DE) has not been determined.

METHODS

Fifteen open chest dogs underwent variable durations of coronary artery occlusion followed by reperfusion. At each stage, MCE was performed by using left atrial injection of AIP201, a deposit microbubble with a mean diameter of 10 +/- 4 microm and a mean concentration of 1.5 x 10(7) x ml(-1). Images were obtained over a 180 degree arc with use of an automated rotational device and were stored in computer as a 3D data set. Postmortem risk area and infarct size were measured in six to eight left ventricular short-axis slices of equal thickness using technetium-99m autoradiography and tissue staining, respectively. MCE images corresponding to these planes were reconstructed off-line.

RESULTS

A close linear relation was noted between the volume of myocardium not showing contrast enhancement on 3D MCE during coronary occlusion and postmortem risk volume (y = 1.2x - 3.0, r = 0.83, SEE = 5.1, n = 15). The volume of myocardium not showing contrast enhancement on 3D MCE after reperfusion also closely correlated with postmortem infarct volume (y = 1.1x - 3.9, r = 0.88, SEE = 4.8, n = 11). No changes in systemic hemodynamic variables were noted with injections of AIP201.

CONCLUSIONS

When combined with AIP201, a deposit microbubble, 3D MCE can be used to accurately determine both risk and infarct volumes in vivo. This method could be used to assess the effects of interventions that attempt to alter the infarct/risk volume ratio.

Relationship between progressive microvascular damage and intramyocardial hemorrhage in patients with reperfused anterior myocardial infarction: myocardial contrast echocardiographic study

BACKGROUND

Recent studies indicated that ischemic microvascular damage may be reversible or progressive after coronary reflow. Intramyocardial hemorrhage is a phenomenon that reflects severe microvascular injury. We examined the relationship between temporal changes in microvascular perfusion patterns detected by myocardial contrast echocardiography (MCE) and intramyocardial hemorrhage detected by magnetic resonance imaging (MRI) in patients with acute myocardial infarction (AMI).

METHODS AND RESULTS

The study population consisted of 24 patients with anterior AMI. All patients underwent MCE shortly after reflow and in the chronic stage (a mean of 31 days after reflow). Wall motion score (WMS) was determined as the sum of 16 segmental scores (dyskinetic/akinetic=3 to normal=0) at days 1 and 31. Gradient-echo acquisition and gadolinium-DTPA-enhanced spin-echo MRI were performed within 10 days after reflow. In MCE shortly after reflow, 16 patients (67%) showed contrast enhancement and the other 8 patients (33%) showed a sizable contrast defect. In the chronic stage, a persistent contrast defect was observed in 7 of 8 patients with a contrast defect shortly after reflow. Consistent contrast enhancement was observed in 12 of 16 patients (75%) with contrast enhancement shortly after reflow, indicating that a contrast defect newly appeared in 4 patients (25%). Intramyocardial hemorrhage was detected in 9 patients (38%): 5 of 7 patients with a persistent contrast defect and in all 4 patients with a new appearance of a contrast defect during the chronic stage. The patients without hemorrhage showed a significant improvement in WMS compared with patients with hemorrhage at day 31 (5+/-5 versus 19+/-6, P<.0005).

CONCLUSIONS

These results suggest that irreversible microvascular damage to the ischemic myocardium may cause intramyocardial hemorrhage after reflow, associated with impaired recovery of left ventricular function. Contrast enhancement within the risk area shortly after reflow does not necessarily indicate long-term microvascular salvage.

Salutary effect of adjunctive intracoronary nicorandil administration on restoration of myocardial blood flow and functional improvement in patients with acute myocardial infarction

Salutary effect of nicorandil, a K+ adenosine triphosphate channel opener, on restoration of myocardial blood flow and functional improvement after coronary revascularization was investigated in 20 patients with first anterior acute myocardial infarction. Ten patients received intracoronary administration of nicorandil (2 mg) after coronary revascularization; the other 10 patients received coronary revascularization only and served as control subjects. Myocardial contrast echocardiography and two-dimensional echocardiography were performed to assess microvascular integrity and regional function in the infarcted area. Nicorandil improved peak contrast intensity ratio (p < 0.001), calculated as the ratio of peak contrast intensity in the infarcted and noninfarcted areas, indicating the restoration of myocardial blood flow to the infarcted myocardium. Regional wall motion improved more significantly in 1 month in patients who received nicorandil (p < 0.01). Thus our results suggested the usefulness of intracoronary nicorandil administration after coronary revascularization for restoring blood flow and functional improvement in patients with acute myocardial infarction.

Comparison of myocardial contrast echocardiography and coronary angiography for assessing the acute protective effects of collateral recruitment during occlusion of the left anterior descending coronary artery at the time of elective angioplasty

To assess the immediate change in collateral flow distribution within the occluded myocardium and the acute protective effects on myocardial ischemia after coronary occlusion, myocardial contrast echocardiography (MCE) was performed in 15 patients with normal left ventricular function undergoing elective coronary angioplasty of the left anterior descending artery, and the results were compared with those obtained from coronary angiography (CA). The sonicated or nonsonicated contrast material was injected into the right coronary artery before and during coronary occlusion and collaterals were graded on a 4-point scale (none = 0 to good = 3). Development of subjective anginal symptoms, ST-segment shift and wall motion abnormality during coronary occlusion were graded on a 4-point scale (none = 0 to severe = 3). Both MCE and CA detected a significant development in collateral flow during coronary occlusion. There was no significant correlation between MCE and CA collateral grades before or during coronary occlusion. The collateral flow assessed with MCE was inversely but significantly correlated with development of subjective anginal symptoms (r(s) = -0.70, p <0.01), ST-segment shift (r(s) = -0.78, p < 0.005) or wall motion abnormality (r(s) = -0.91, p < 0.001) during coronary occlusion. In contrast, the angiographic collateral flow was not correlated with development of anginal symptoms (r(s) = -0.46, p = 0.10), ST-segment shift (r(s) = -0.41, p = 0.14), or wall motion abnormality (r(s) = -0.26, p = 0.35). The present study suggested that the acute protective effects of coronary collaterals during coronary occlusion were closely associated with myocardial perfusion rather than the angiographic epicardial collateral vessel filling, and thus MCE was useful in assessing the acute protective effects of coronary collaterals during coronary occlusion.

Disappearance of the 'no-reflow' phenomenon after adjunctive intracoronary administration of nicorandil in a patient with acute myocardial infarction

Adjunctive intracoronary administration of nicorandil, an ATP-sensitive potassium channel opener, after successful coronary revascularization was performed in a 54-year-old patient with acute myocardial infarction. The 'no-reflow' phenomenon disappeared after nicorandil administration and significant functional recovery of the infarcted myocardium was achieved. This suggests that nicorandil could eliminate the 'no-reflow' phenomenon after successful coronary revascularization.

Combination of dobutamine and myocardial contrast echocardiography to differentiate postischemic from infarcted myocardium

OBJECTIVES

This study tested whether the combination of dobutamine echocardiography (DE) and myocardial contrast echocardiography (MCE) was superior to either technique alone in identifying postischemic myocardium and in differentiating it from necrotic myocardium.

BACKGROUND

Wall motion abnormalities at rest occur in postischemic myocardium in the presence of infarction, stunning or hibernation, alone or in combination. Various investigators have suggested that either DE or MCE can be used to identify the presence of myocardial viability.

METHODS

We studied a total of 53 mongrel dogs in an open chest model of coronary occlusion of various durations followed by reperfusion and dobutamine administration (10 microg/kg body weight per min). MCE with aortic root injections of Albunex (area under the curve) and DE (percent thickening fraction) were performed at the different stages. Postmortem triphenyltetrazolium chloride (TTC) staining was used to identify myocardial necrosis.

RESULTS

Thirteen dogs underwent brief (15 min) occlusions and developed no necrosis (Group I). Of 40 dogs that underwent prolonged (30 to 360 min) occlusions, 14 had no infarction (Group II), whereas 26 did (Group III: 12 papillary muscle, 7 subendocardial, 7 transmural). MCE (expressed as percent change from baseline) demonstrated changes that paralleled the blood flow changes observed by radiolabeled microspheres at all interventions (r = 0.67, p < 0.0001). Regional ventricular function improved with dobutamine administration in the ischemic region in all three groups. The sensitivity (88%) for detecting myocardial viability was superior when the two techniques were combined; however, a poor specificity (61%) was observed.

CONCLUSIONS

Contractile reserve and perfusion data are complementary when assessing regional wall motion abnormalities in postischemic myocardium. DE alone cannot differentiate postischemic from infarcted myocardium; simultaneous data on myocardial perfusion are required. The combination of DE and MCE is superior to either technique alone for identifying the absence of myocardial necrosis.

Reperfusion Injury: Does It Exist and Does It Have Clinical Relevance?

Although reperfusion is an absolute prerequisite for the survival of ischemic tissue, it is not necessarily without hazard. Many (but not all) cardiologists are of the opinion that some components of reperfusion may be detrimental and able to inflict injury over and above that attributable to the ischemia. In this article we define four sequelae of reperfusion that might be designated as "reperfusion injury." We identify possible underlying mechanisms and consider whether any of these forms of reperfusion injury are of clinical relevance.

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.

Usefulness of myocardial contrast echocardiography for the assessment of serial changes in risk area in patients with acute myocardial infarction

Serial myocardial contrast echocardiograms were recorded to investigate the time course of microvascular integrity in the risk area for first acute myocardial infarction. Serial changes in the risk area were categorized into 4 main types according to the potential for recovery from microvascular impairment.

Left ventricular papillary muscle perfusion assessed with myocardial contrast echocardiography

This myocardial contrast echocardiographic study shows that left ventricular posteromedial papillary muscle is supplied by either the right or left coronary artery in most subjects, but may be supplied by both coronary arteries. The posteromedial papillary muscle and its adjacent area may be supplied by a different coronary artery.

Contractile versus microvascular reserve for the determination of the extent of myocardial salvage after reperfusion. The effect of residual coronary stenosis

BACKGROUND

We hypothesized that microvascular reserve is a better indicator of the extent of viable myocardium postinfarction than contractile reserve, especially in the presence of a residual stenosis of the infarct-related artery.

METHODS AND RESULTS

Fifteen dogs with various infarct sizes were studied after reperfusion. Contractile reserve, studied by use of dobutamine echocardiography, and microvascular reserve, studied by use of myocardial contrast echocardiography, were measured both before and after creation of a stenosis. In the absence of a stenosis, the relation between infarct size, expressed as percent of risk area, and wall thickening improved with increasing doses of dobutamine (r = .41, .71, and .90 for 5, 10, and 15 micrograms.kg-1.min-1, respectively; P < .01 for dobutamine 15 micrograms.kg-1.min-1). In the presence of a stenosis, however, the relation was poor for all doses of dobutamine (r = .22, .57, and .32 for 5, 10, and 15 micrograms.kg-1.min-1, respectively; P < .01 for 15 micrograms.kg-1.min-1 dobutamine in the absence of a stenosis). There was a fair correlation between infarct size and perfusion defect size on myocardial contrast echocardiography after reperfusion (r = .82), with the defect size underestimating infarct size by approximately 20%. This relationship improved (P < .01) during infusions of both adenosine (r = .99) and dobutamine (r = .94) in the absence of a stenosis. The correlations between infarct size and perfusion defect on myocardial contrast echocardiography also remained good in the presence of a stenosis (r = .95 and .81 for adenosine and dobutamine, respectively; P = NS compared with stenosis).

CONCLUSIONS

Microvascular reserve is superior to contractile reserve for definition of the spatial topography of necrosis and hence the extent of viable myocardium within the infarct bed after reperfusion, particularly when a residual stenosis is present in the infarct-related artery.

Potential clinical implications of abnormal myocardial perfusion patterns immediately after reperfusion in a canine model: a myocardial contrast echocardiography study

During myocardial infarction, lack of myocardial opacification after reperfusion has been associated with poor or no recovery of function. We have previously documented the presence of perfusion abnormalities after brief coronary occlusions without infarction and the absence of perfusion abnormalities after prolonged occlusions with infarction. To characterize myocardial perfusion patterns immediately after reperfusion, we studied 53 animals in two groups in a coronary occlusion-reperfusion model. Temporary occlusions (group 1, 15 minutes; group 2, 30 to 360 minutes) were performed, followed by reperfusion with and without dobutamine. Myocardial contrast echocardiography was performed with aortic root injections of sonicated 5% serum human albumin (Albunex) during each intervention. Group 1 dogs showed no evidence of myocardial infarction. In group 2, 26 of 40 dogs had infarctions. After reperfusion, no perfusion abnormalities were seen in 13 of 26 group 2 dogs with infarctions; perfusion abnormalities were identified after reperfusion in 2 of 13 group 1 and in 8 of 14 group 2 dogs without infarctions. In animals subjected to prolonged ischemia, the absence of perfusion abnormalities after reperfusion did not rule out the presence of necrosis. Similarly, in animals without infarction subjected to ischemia, the presence of a perfusion defect after reperfusion did not represent the presence of necrosis but an abnormal microvascular reserve. These results suggest that early after reperfusion, assessment of perfusion by myocardial contrast echocardiography has significant limitations in the evaluation of myocardial viability and salvage.

Myocardial integrated ultrasonic backscatter in patients with old myocardial infarction: comparison with radionuclide evaluation

The purpose of our study was to clarify whether the abnormalities in integrated backscatter may be used to assess myocardial viability in patients with old myocardial infarction by comparing these integrated backscatter parameters with conventional radionuclide and echocardiographic estimates of myocardial viability. Two myocardial integrated backscatter parameters, the magnitude of cyclic variation in integrated backscatter and the myocardial integrated backscatter calibrated with the power of Doppler signals from the blood along the same ultrasound beam (calibrated myocardial integrated backscatter), were measured in 21 normal persons and 33 patients with old anteroseptal myocardial infarction. Calibrated myocardial integrated backscatter was higher and the magnitude of cyclic variation in integrated backscatter was lower in the infarct septum compared with the septum of normal subjects. Percent thallium uptake, as assessed in scintigraphic images taken at rest or after reinjection, correlated well with the calibrated myocardial integrated backscatter (r = -0.72, p < 0.01) and more weakly but significantly with the magnitude of cyclic variation in integrated backscatter (r = 0.55, p < 0.05) in 16 of 33 patients. The measurement of calibrated myocardial integrated backscatter, in addition to the magnitude of cyclic variation of integrated backscatter, may likely be valuable in the noninvasive assessment of myocardial viability.