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

Impact of coronary collaterals on in-hospital and 5-year mortality after ST-elevation myocardial infarction in the contemporary percutaneous coronary intervention era: a prospective observational study

OBJECTIVES

To evaluate the short-term and long-term prognostic impacts of acute phase coronary collaterals to occluded infarct-related arteries (IRA) after ST-elevation myocardial infarction (STEMI) in the percutaneous coronary intervention (PCI) era.

DESIGN

A prospective observational study.

SETTING

Osaka Acute Coronary Insufficiency Study (OACIS) in Japan.

PARTICIPANTS

3340 patients with STEMI from the OACIS database who were admitted to hospitals within 24 hours from the onset and who had a completely occluded IRA.

INTERVENTIONS

Patients were divided into 4 groups according to the Rentrop collateral score (RCS) by angiography on admission (RCS-0, no visible collaterals; RCS-1, collaterals without IRA filling; RCS-2, collaterals with partial IRA filling; and RCS-3, collaterals with complete IRA filling).

PRIMARY OUTCOME MEASURES

In-hospital and 5-year mortality.

RESULTS

Patients with RCS-0/3 were older than patients with RCS-1/2, and the prevalence of previous myocardial infarction was highest in patients with RCS-3. Median peak creatinine phosphokinase levels decreased as RCS increases (p<0.001), suggesting the acute cardioprotective effects of collaterals. Although RCS-1 and RCS-2 collaterals were associated with better in-hospital mortality (adjusted OR 0.48, p=0.046 and 0.38, p=0.010 for RCS-1 and RCS-2, respectively) and 5-year mortality (adjusted HR 0.53, p=0.004 and 0.46, p<0.001 for RCS-1 and RCS-2, respectively) as compared with R-0, presence of RCS-3 collaterals was not associated with improved in-hospital (adjusted OR 1.35, p=0.331) and 5-year mortality (adjusted HR 0.98, p=0.920), possibly because worse clinical profiles in patients with RCS-3 may mask mortality benefit of coronary collaterals.

CONCLUSIONS

Presence of acute phase coronary collaterals such as RCS-1 and RCS-2 were associated with better in-hospital and 5-year mortality after STEMI in the contemporary PCI era.

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.

Quantitative assessment of microcollateral recruitment during coronary occlusion using real-time intravenous myocardial contrast echocardiography

BACKGROUND

Residual collateral-derived myocardial blood flow (MBF) (A x beta) is important to protect against myocardial ischemia after acute coronary occlusion.

METHODS

Recruitment of microcollateral was assessed in 22 dogs with left circumflex coronary artery occlusion by analysis of MBF and regional wall thickening (WT) using real-time myocardial contrast echocardiography.

RESULTS

Video intensity and WT at the center of risk area were significantly lower than those at the border of risk area. The video intensity, A value, beta value, and MBF correlated well with WT after left circumflex coronary artery occlusion. The WT of the area with above 25% of normal MBF was preserved and was higher than that at below 25%. However, the deterioration of WT was not distinguished according to A value.

CONCLUSION

Real-time myocardial contrast echocardiography is a useful noninvasive method to evaluate collateral-derived MBF, which can be a reliable index of protection against myocardial ischemia.

Myocardial contrast echocardiography assessment of acute changes in collateral perfusion of contralateral coronary artery with coronary flow reserve after coronary angioplasty

BACKGROUND

Coronary flow velocity reserve (CFVR) is used to evaluate the severity of epicardial and intramyocardial coronary artery disease. Collateral flow to an adjacent compromised myocardial territory may influence the CFVR of a specific artery.

METHODS

To assess the impact of collateral flow on CFVR, we measured CFVR and assessed perfusion area (PA) with myocardial contrast echocardiography in the right coronary arteries of 18 patients with total/subtotal occlusion of the left anterior descending coronary artery before and after angioplasty. A total of 10 patients had well-developed collaterals emerging from the right coronary artery (group I) and 8 patients did not (group II). Using a Doppler-tipped guidewire, we measured CFVR, which is defined as the ratio of papaverine-induced hyperemic average peak velocity of coronary flow to baseline.

RESULTS

Before angioplasty of the left anterior descending coronary artery, CFVR was significantly reduced in group I compared with group II (2.35 +/- 0.47 vs 3.26 +/- 0.54, P < .01). Baseline average peak velocity in group I before angioplasty was significantly greater than that after angioplasty (23.7 +/- 11.6 vs 19.2 +/- 9.7 cm/s, P < .05). After angioplasty, CFVR immediately increased in group I to 3.46 +/- 0.54 ( P < .001). The increase in CFVR was well correlated with the decrement in PA after angioplasty (r = 0.883, P < .001).

CONCLUSION

The CFVR of an artery that supplies extensive collaterals is limited because of an elevation in the baseline resting flow velocity. This restriction in CFVR improves proportionally with decreases in PA that occurs after angioplasty of the ipsilateral coronary artery. These data suggest that PA, in addition to coronary artery structure, influences CFVR.

Strain rate imaging after dynamic stress provides objective evidence of persistent regional myocardial dysfunction in ischaemic myocardium: regional stunning identified?

OBJECTIVE

To investigate whether persistent ischaemic dysfunction of the myocardium after dynamic stress can be diagnosed from changes in ultrasonic strain rate and strain.

DESIGN

Prospective observational study, with age matched controls.

SETTING

University hospital.

PATIENTS AND METHODS

26 patients (23 men, mean (SD) age 58.9 (8.1) years) with coronary artery disease but no infarction and 12 controls (9 men, aged 56.1 (8.8) years) with normal coronary arteriography and negative exercise test underwent treadmill exercise (Bruce protocol). Tissue Doppler echocardiography was performed at baseline, at peak exercise, and at intervals up to one hour. Systolic and diastolic velocity, strain, and strain rate were recorded in the basal anterior segment of 16 patients with proximal left anterior descending coronary artery disease.

RESULTS

Patients developed ischaemia, since they experienced angina, exercised for less time, and reached a lower workload than the control group, and had ST segment depression (-2.4 mm). Myocardial systolic velocity immediately after exercise increased by 31% and strain rate fell by 25% compared with increases of 92% and 62%, respectively, in the control group (p < 0.05). During recovery, myocardial systolic velocity and strain rate normalised quickly, whereas systolic strain remained depressed at 30 and 60 minutes after exercise, by 21% and 23%, respectively, compared with baseline (p < 0.05 versus controls). Myocardial diastolic velocities and strain rate normalised but early diastolic strain remained depressed by 32% compared with controls for 60 minutes (p < 0.05). Strain during atrial contraction was abnormal for 30 minutes.

CONCLUSIONS

Myocardial strain shows regional post-ischaemic dysfunction in systole and diastole and may become a useful diagnostic tool in patients presenting with chest pain with a normal ECG.

Intraoperative ischemia and long-term events after minimally invasive coronary surgery

BACKGROUND

Concern has been raised about the effects of prolonged left anterior descending (LAD) artery occlusion during minimally invasive direct coronary artery bypass graft surgery (MIDCABG). We sought to assess the impact of myocardial dysfunction during MIDCABG on long-term outcome and the protective role of collateral circulation on myocardial ischemia.

METHODS

Myocardial function was evaluated in 92 patients by intraoperative transesophageal echocardiography during MIDCABG.

RESULTS

Wall motion score index increased during LAD occlusion (p < 0.00l) and reverted after LAD reopening (p < 0.001 versus occlusion and p = not significant versus baseline). The change in wall motion score index (occlusion versus baseline) was higher in patients with multivessel disease (p < 0.05) and in patients with LAD Thrombolysis in Myocardial Infarction study classification flow grade 2 or less without collateral circulation (p < 0.05). Myocardial stunning was documented in 12 patients (13%). The 5-year adverse event rate (including death, myocardial infarction, and revascularization) was 12%. By multivariate Cox regression analysis, multivessel disease, but not perioperative ischemia or stunning, was the only predictor of event-free survival.

CONCLUSIONS

During MIDCABG anterior wall dysfunction is transient, with prompt recovery after completion of the anastamosis in most cases; myocardial stunning can be documented in a minority of patients. Flow either antegrade or retrograde in the LAD territory plays a protective role against the development of ischemia. Multivessel disease, but not perioperative ischemia or stunning, predicts long-term event-free survival.

Fate of collateral circulation after successful coronary angioplasty of total occlusion assessed by coronary angiography and myocardial contrast echocardiography

A well-developed collateral circulation is frequently observed in patients with total coronary occlusion. However, the fate of the collateral circulation after successful percutaneous transluminal coronary angioplasty (PTCA) has not been fully characterized. The purpose of this study was to compare the efficacy of coronary angiography and myocardial contrast echocardiography (MCE) in the evaluation of the collateral circulation after PTCA and to assess the temporal changes of the collateral circulation after successful PTCA of a totally occluded artery by using these 2 diagnostic methods. The study group was comprised of 20 consecutive patients (16 male, mean age 54 years) who underwent elective PTCA for total coronary occlusion. Coronary angiography was performed before, immediately after, and 24 hours after PTCA. MCE was also performed before, immediately after, and 24 hours after PTCA, by the intracoronary injection of sonicated radiographic contrast medium. According to the angiographic findings, the collateral circulation was graded on a scale of 0 to 3 as follows: 0 = no visible filling; 1 = collateral filling of side branches; 2 = partial collateral filling of the epicardial artery; 3 = complete filling of the epicardial artery. By MCE, myocardial perfusion by the collateral circulation was assessed by scoring the contrast pattern of collateral-dependent myocardial segments as follows: 0 = none; 0.5 = patchy or epicardial; 1 = homogeneous. The left anterior descending artery was occluded in 12 patients and the right coronary artery in 8 patients. Coronary angiographic collateral grades before PTCA were grade 2 in 5 patients and grade 3 in 15. PTCA with stenting was successfully performed in all patients without significant residual stenosis. Coronary angiography showed collateral circulation disappeared after PTCA in all patients. However, residual collateral perfusion was observed in 7 patients by MCE, performed immediately after PTCA (score 1 in 3 patients; score 0.5 in 4 patients). This residual collateral perfusion could be demonstrated even 24 hours after PTCA by MCE in 3 patients (all patients were 0.5 in myocardial perfusion score). In conclusion, successful PTCA with stenting of a totally occluded coronary artery leads to a disappearance of collateral vessels by coronary angiography in most of the patients. However, although angiographically not visible, coronary collateral circulation may persist even 24 hours after successful PTCA of a totally occluded artery demonstrated by MCE.

Acute changes in systolic and diastolic events during clinical coronary angioplasty: a comparison of regional velocity, strain rate, and strain measurement

Ultrasound-derived natural strain rate and strain are new Doppler myocardial imaging (DMI) parameters, which can measure local deformation independently of overall heart motion and thus could better characterize local contractility than DMI velocities alone. This study was undertaken to evaluate the relative benefits of regional velocity, strain rate, and strain measurements in detecting the range of acute changes in regional myocardial function in the "at-risk" zone during coronary angioplasty. Sixty-one patients (aged 63 +/- 12, 18 women) with stable angina pectoris were studied before, at the end of, and during recovery from a 60-second percutaneous transluminal coronary angioplasty (PTCA) balloon occlusion. High frame rate (147 fps) color DMI regional velocity data were derived from basal posterior (parasternal view) and mid, apical septal (apical view) "at-risk" segments as well as from the corresponding segments in healthy subjects and analyzed offline for velocity (VEL), strain rate (SR), and strain (epsilon) measurements. Coronary occlusion resulted in the reduction in VEL(SYS), SR(SYS), and epsilon(SYS) values for both radial (RCA/CX occlusion) and longitudinal data (LAD occlusion) in all segments analyzed. Velocity parameters alone failed to distinguish between baseline and occlusive measurements in the "at-risk" segments with visually abnormal baseline function. SR(SYS) and epsilon(SYS) had a higher diagnostic accuracy (sensitivity 75%, 80% and specificity 80%, 82%, respectively) than VEL(SYS) velocity alone (sensitivity 68%, specificity 65%,) for identifying acute ischemia in either baseline normal and abnormal segments. DMI-derived indexes can identify and quantify the spectrum of acute systolic and diastolic ischemic changes induced during clinical PTCA. The quantitation of regional deformation rather than motion would appear to be more appropriate in detecting and quantifying acute ischemic changes in myocardial function, especially in segments with pre-existing abnormal function.

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.

Characterization of contraction and perfusion in the lateral border zone between normal and ischemic myocardium following coronary occlusion by myocardial contrast echocardiography

We performed myocardial contrast echocardography with power Doppler imaging during left anterior descending occlusion in 10 dogs, and found that video intensity and dyssynergy in lateral border zones of ischemic myocardium were present, but the video intensity was significantly lower than adjacent nonischemic zones. The results of this study demonstrate that levels of perfusion and contraction, which are intermediate between normal and central ischemic zones, are observed in the border zone with coronary occlusion by myocardial contrast echocardography, and may have implications in identifying myocardium that will be spared necrosis and in measuring ultimate infarct size.

Update on myocardial contrast echocardiography: a surgeon's perspective

The ability to evaluate myocardial perfusion and microvascular structural integrity can help surgeons predict the necessity for surgical intervention, the sequence of intraoperative interventions, the risk of perioperative infarction, the likelihood of successful surgical recovery, and the degree of long-term clinical benefit. The ability to directly assess perfusion intraoperatively may allow surgeons to reliably evaluate a patient's myocardial perfusion at any time during the operative procedure. As this article will discuss, surgeons may use myocardial contrast echocardiography intraoperatively to evaluate myocardial function and integrity, to determine the order of graft placement, to determine the success of bypass graft patency, and to help predict those patients who will experience successful cardiac function after recovering from surgery.

[Quantification of myocardial ischemia in regions dependent on occluded coronary arteries in patients without previous infarction]

INTRODUCTION AND OBJECTIVES

The aim of this study is to assess myocardial ischemia in regions with no infarction dependent occluded coronary arteries.

PATIENTS AND METHODS

149 patients with proved coronary artery disease and without previous myocardial infarction were studied by 99mTc-MIBI SPECT (long protocol) and coronary angiography. The extent of the uptake reversibility was quantified in 3 regions (antero-septal, inferior and lateral) of the polar maps, assessing the percentage of each region that had a > 10% difference resulting from the rest uptake minus the stress uptake. The regions dependent on one occluded artery were compared to those dependent on non-occluded arteries. In the regions dependent on one occluded artery a comparison was also made between those which had a good collateral circulation and those which did not.

RESULTS

Fifty-four out of 149 patients (36%) had at least one occluded coronary artery (20 anterior descending, 22 right and 27 circumflex coronary arteries). In the visual analysis, reversible defects were observed in all patients with occlusion of the anterior descending and the right coronary artery, but only in half of the occlusions of the circumflex coronary artery. The extent of this reversibility was significantly higher in the regions dependent on occluded arteries and was highly variable, though lower when good collateral circulation was present.

CONCLUSIONS

Reversible defects were always observed in the occlusions of the left anterior descending and right coronary arteries, but only in half of those of the circumflex artery. The extent of the ischemia was higher in the regions dependent on one occluded coronary artery, mainly when there was an absence of good collateral circulation.

Different mechanisms of ischemic adaptation to repeated coronary occlusion in patients with and without recruitable collateral circulation

OBJECTIVES

The aim of this study was to investigate the interaction between ischemic preconditioning (IP) and collateral recruitment (CR) during ischemic adaptation in patients.

BACKGROUND

The mechanism of ischemic adaptation still remains controversial in humans.

METHODS

The clinical, electrocardiographic, hemodynamic and echocardiographic responses to three 150-s occlusions of the left anterior descending coronary artery were assessed in relation to CR in 18 patients with effort angina undergoing elective percutaneous transluminal coronary angioplasty.

RESULTS

During the first occlusion, recruitable collateral circulation (RCC) to the occluded myocardium was detected by myocardial contrast echocardiography in 6 patients (Group C) and was not seen in 12 (Group N). In Group N, all patients manifested signs of severe ischemia during each inflation. However, their symptoms and ST segment shift significantly decreased from the first to the third occlusions, suggesting the occurrence of IP. The elevation of mean pulmonary artery pressure and deterioration of anterior wall motion were comparable between the first and the third occlusions in Group N. In contrast, myocardial ischemia was significantly less marked during occlusion in Group C than in Group N, and no preconditioning effect was observed. The extent of RCC did not differ between the first and the third occlusions in each group.

CONCLUSIONS

Both IP and CR may play independent roles in ischemic adaptation in humans. With RCC, myocardial ischemia was greatly reduced. Without RCC, preconditioning clinically and electrocardiographically lessened myocardial ischemia but failed to preserve left ventricular function.

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.