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

Coronary flow reserve is related to the extension and transmurality of myocardial necrosis and predicts functional recovery after acute myocardial infarction

BACKGROUND

Few studies have examined the effect of transmurality of myocardial necrosis on coronary microcirculation. The aim of this study was to examine the influence of cardiac magnetic resonance-derived (GE-MRI) structural determinants of coronary flow reserve (CFR) after anterior myocardial infarction (STEMI), and their predictive value on regional functional recovery.

METHODS

Noninvasive CFR and GE-MRI were studied in 37 anterior STEMI patients after primary coronary angioplasty. The wall motion score index in the left descending anterior coronary artery territory (A-WMSI) was calculated at admission and follow-up (FU). Recovery of regional left ventricular (LV) function was defined as the difference in A-WMSI at admission and FU. The necrosis score index (NSI) and transmurality score index (TSI) by GE-MRI were calculated in the risk area. Baseline (BMR) and hyperemic (HMR) microvascular resistance, arteriolar resistance index (ARI), and coronary resistance reserve (CRR) were calculated at the Doppler echocardiography.

RESULTS

Bivariate analysis indicated that the CPK and troponin I peak, heart rate, NSI, TSI, BMR, the ARI, and CRR were related to CFR. Multivariable analysis revealed that TSI was the only independent determinant of CFR. The CFR value of >2.27, identified as optimal by ROC analysis, was 77% specific and 73% sensitive with accuracy of 76% in identifying patients with functional recovery.

CONCLUSIONS

Preservation of microvascular function after AMI is related to the extent of transmurality of myocardial necrosis, is an important factor influencing regional LV recovery, and can be monitored by noninvasive CFR.

Assessment of Coronary Flow Reserve by Adenosine Stress Myocardial Perfusion Imaging in Patients with Hypertension

In this study, our aim was to assess the coronary flow reserve (CFR) by performing the adenosine stress (99m)Tc-MIBI single-photon computed tomographic (SPECT) myocardial perfusion imaging in patients with hypertension. 47 hypertensive patients with normal coronary angiography were divided into 2 groups, defined by the presence (LVH, n = 22) and absence (non-LVH, n = 25) of left ventricular hypertrophy with 17 normal cases as controls. All patients were administered the adenosine stress-rest (99m)Tc-MIBI scintigraphy. 0.14 mg/kg/min adenosine was administered by continuous infusion for 6 min. We found that adenosine-induced myocardial ischemia was present in 26 cases (55.3 %) with 87 segments (20.6 %) showing abnormal distribution in the hypertensive group versus a single case (5.9 %) (χ (2) = 31.12, P < 0.001) and segment (0.7 %) (χ (2) = 32.90, P < 0.001) in the control group by SPECT perfusion. In the LVH group, 17 cases (77.3 %) and 67 segments (33.8 %) of myocardial ischemia were present. In the non-LVH group, there were 9 cases (36.0 %) (χ (2) = 8.06, P < 0.001), 20 segments (8.9 %) (χ (2) = 40.13, P < 0.001). There was a significant decrease in coronary reserve in the hypertensive groups following adenosine infusion with a fourfold decrease in cases and a sixfold decrease in segments (P < 0.001). Our study suggests that assessing CFR by the (99m)Tc-MIBI adenosine stress by SPECT imaging is a relatively easy, safe, and non-invasive test in patients with hypertension. We noted a decrease in CFR in patients with hypertension. This decrease was especially remarkable for hypertensive patients with LVH. This study shows that administering the (99m)Tc-MIBI adenosine stress by SPECT imaging is a safe, simple, and non-invasive test for detecting CFR in patients with hypertension.

Non-invasive evaluation of myocardial reperfusion by transthoracic Doppler echocardiography and single-photon emission computed tomography in patients with anterior acute myocardial infarction

BACKGROUND

The study was designed to evaluate whether the preserved coronary flow reserve (CFR) 72 hours after reperfused acute myocardial infarction (AMI) is associated with less microvascular dysfunction and is predictive of left ventricular (LV) functional recovery and the final infarct size at follow-up.

METHODS

In our study, CFR was assessed by transthoracic Doppler echocardiography (TDE) in 44 patients after the successful percutaneous coronary intervention during the acute AMI phase. CFR was correlated with contractile reserve assessed by low-dose dobutamine echocardiography and with the total perfusion defect measured by single-photon emission computed tomography 72 hours after reperfusion and at 5 months follow-up. The ROC analysis was performed to determine test sensitivity and specificity based on CFR. Categorical data were compared by an χ² analysis, continuous variables were analysed with the independent Student's t test. In order to analyse correlation between CFR and the parameters of LV function and perfusion, the Pearson correlation analysis was conducted. The linear regression analysis was used to assess the relationship between CFR and myocardial contractility as well as the final infarct size.

RESULTS

We estimated the CFR cut-off value of 1.75 as providing the maximal accuracy to distinguish between patients with preserved and impaired CFR during the acute AMI phase (sensitivity 91.7%, specificity 75%). Wall motion score index was better in the subgroup with preserved CFR as compared to the subgroup with reduced CFR: 1.74 (0.29) vs. 1.89 (0.17) (p < 0.001) during the acute phase and 1.47 (0.30) vs. 1.81 (0.20) (p < 0.001) at follow-up, respectively. LV ejection fraction was 47.78% (8.99) in preserved CFR group vs. 40.79% (7.25) in impaired CFR group (p = 0.007) 72 hours after reperfusion and 49.78% (8.70) vs. 40.36% (7.90) (p = 0.001) after 5 months at follow-up, respectively. The final infarct size was smaller in patients with preserved as compared to patients with reduced CFR: 5.26% (6.14) vs. 23.28% (12.19) (p < 0.001) at follow-up.

CONCLUSION

The early measurement of CFR by TDE can be of high value for the assessment of successful reperfusion in AMI and can be used to predict LV functional recovery, myocardial viability and the final infarct size.

Predicting myocardial functional recovery after acute myocardial infarction: relationship between myocardial strain and coronary flow reserve

Background and Objectives

The purpose of this study was to evaluate the relationship between myocardial strain and coronary flow reserve (CFR) in the prediction of myocardial functional recovery after acute myocardial infarction (AMI).

Subjects and Methods

Consecutive patients with anterior ST elevation AMI were analyzed. Left ventricular (LV) strain, determined by 2-dimensional speckle tracking imaging and CFR, determined by intracoronary flow measurement, were obtained on the same day, 3-5 days after primary percutaneous coronary intervention. A-strain was defined as the mean systolic longitudinal strain of 11 LV segments (out of 18) assumed to be supplied by the left anterior descending coronary artery (LAD). Functional recovery was defined as improved wall motion >1 grade seen in at least 2 contiguous dysfunctional segments by echocardiography at the 6-month follow-up.

Results

Of 20 patients, 8 patients had preserved CFR (>2.0) and 12 patients had impaired CFR (≤2.0). There were no differences between the 2 CFR groups in LV ejection fractions and wall motion score indices in the LAD territory. However, A-strain was greater in patients with preserved CFR than in patients with impaired CFR (-6.4±2.0% vs. -4.6±1.4%, p=0.03). A-strain and CFR correlated well with each other (r=-0.49, p=0.03). Ten of 20 patients showed functional recovery at 6 months. Of clinical and echocardiographic parameters, A-strain was the only predictor of recovery (odds ratio 2.02, 95% confidence interval=1.03-3.97, p=0.04). For predicting recovery, the sensitivity and specificity were 80.0% and 80.0%, respectively, for CFR (cutoff=1.60), and 60.0% and 90.0%, respectively, for A-strain (cutoff=-6.13%).

Conclusion

Myocardial strain correlates well with the extent of microvascular integrity and can be used as a noninvasive method for predicting recovery after AMI.

Proximal coronary hemodynamic changes evaluated by intracardiac echocardiography during myocardial ischemia and reperfusion in a canine model

BACKGROUND

The purpose of this study was to assess whether the dynamic changes in coronary flow velocity and coronary flow velocity reserve (CFVR) by intracardiac echocardiography (ICE) within proximal coronary arteries are related to myocardial perfusion status and infarct size in a myocardial ischemia-reperfusion injury model.

METHODS

In 14 dogs, left anterior descending coronary artery (LAD) was ligated for 2 hours followed by 2 hours reperfusion. Coronary flow velocity was obtained by ICE within coronary arteries at baseline, and at the end of both occlusion and reperfusion period. The CFVR was calculated as the ratio of hyperemic to resting peak diastolic velocity (PDV). Myocardial perfusion was evaluated by real time myocardial contrast echocardiography (MCE). The infarct area was detected by triphenyltetrazolium chloride (TTC) staining and expressed as the percentage of the whole left ventricular (LV) area.

RESULTS

CFVR significantly decreased both in proximal LAD and left circumflex (LCx) artery at the end of occlusion, and did not recover at the end of reperfusion. However, no significant difference in flow parameters was observed between dogs with myocardial perfusion defect and those without. CFVR in LAD at the end of reperfusion did not correlate with the infarct size (r =-0.182, P = NS) either.

CONCLUSIONS

Decreased CFVR detected by ICE occurs both in ischemic and in nonischemic proximal arteries during myocardial ischemia and early stage of reperfusion. This change in CFVR has poor correlation with the extent of microvascular impairment and cannot be used to predict infarct size.

Transthoracic Doppler Echocardiographic Assessment of Left Anterior Descending Coronary Artery and Intramyocardial Artery Predicts Left Ventricular Remodeling and Wall-motion Recovery After Acute Myocardial Infarction

BACKGROUND

Previous studies reported that a coronary flow velocity (FV) pattern with a rapid diastolic deceleration time (DDT) immediately after percutaneous coronary intervention implies advanced microvascular damage in patients who have experienced an acute myocardial infarction (AMI).

METHODS

Using transthoracic echocardiography, we recorded the coronary FV in the left anterior descending coronary artery (LAD) and the FV in the intramyocardial artery 2 days after successful percutaneous coronary intervention in 24 patients who had experienced an anterior AMI. We measured the DDT of the LAD and the intramyocardial artery. DDT of the LAD and the intramyocardial artery was detected in the anteroseptal lesion, the wall motion of which revealed severe hypokinesis or akinesis. We performed echocardiography during both the acute phase and 6 months after the AMI.

RESULTS

Patients were divided into two groups (group A: DDT of the LAD < or = 600 milliseconds [n = 10], group B: DDT of the LAD > or = 600 milliseconds [n = 14]). DDT of the LAD and the intramyocardial artery was significantly shorter for group A than group B (373 +/- 223 vs 786 +/- 105 milliseconds, P < .0001). In the acute phase, there were no significant differences in left ventricular (LV) wall-motion score index (WMSI), LV end-diastolic volume (EDV), or ejection fraction (WMSI: 2.38 +/- 0.24 vs 2.08 +/- 0.58, P = .20; LV EDV: 160 +/- 41 vs 154 +/- 34 mL; ejection fraction: 45 +/- 11 vs 46 +/- 5%). However, WMSI and LV EDV in group A were significantly greater than in group B (WMSI: 2.47 +/- 0.16 vs 1.84 +/- 0.57, P = .01; LV EDV: 198 +/- 28 vs 132 +/- 37 mL, P = .0004) and the ejection fraction in group A was significantly lower than in group B (38 +/- 9 vs 55 +/- 10%, P = .001) during the chronic phase.

CONCLUSIONS

In patients who had experienced an anterior AMI, we could predict wall-motion recovery of the infarcted area by using the coronary FV of the LAD and FV of the intramyocardial artery.

Non-invasive coronary flow reserve is correlated with microvascular integrity and myocardial viability after primary angioplasty in acute myocardial infarction

OBJECTIVE

To test whether preserved coronary flow reserve (CFR) two days after reperfused acute myocardial infarction (AMI) is associated with less microvascular dysfunction (" no-reflow" phenomenon) and is predictive of myocardial viability.

DESIGN

24 patients with anterior AMI underwent CFR assessment in the left anterior descending coronary artery (LAD) with transthoracic echocardiography and myocardial contrast echocardiography (MCE) 48 h after primary angioplasty in the LAD (mean 4 (SD 2) and 3 (1) days, respectively). Low-dose dobutamine echocardiography was performed 6 (3) days after AMI and follow-up echocardiography at three months.

RESULTS

No-reflow extent was greater in patients with impaired CFR (< 2.5) than in those with preserved CFR (> 2.5) (55 (35)% v 11 (25)%, p < 0.001). MCE reflow was more common in patients with preserved CFR (8/12) than in those with reduced CFR (1/12, p < 0.05). Wall motion score index in the LAD territory (A-WMSI) was similar at the first echocardiography (2.14 (0.39) v 2.32 (0.47), NS), although it was better in patients with preserved CFR at dobutamine (1.38 (0.45) v 1.97 (0.67), p < 0.05) and follow-up echocardiography (1.36 (0.40) v 1.97 (0.64), p < 0.05). An inverse correlation was found between CFR and A-WMSI at dobutamine and follow-up echocardiography (r = -0.49, p = 0.016 and r = -0.55, p = 0.005) and between MCE and A-WMSI at dobutamine and follow-up echocardiography (r = -0.75, p < 0.001 and r = -0.75, p < 0.001). By multivariate analysis MCE reflow remained the only predictor of recovery at both dobutamine and follow-up echocardiography (odds ratio 1.06, 95% CI 1 to 1.1, p = 0.009).

CONCLUSION

CFR is inversely correlated with the extent of microvascular dysfunction at MCE two days after reperfused AMI. CFR and MCE reflow early after AMI are correlated with myocardial viability at follow up.

Levosimendan improves hemodynamics and coronary flow reserve after percutaneous coronary intervention in patients with acute myocardial infarction and left ventricular dysfunction

BACKGROUND

Positive inotropic agents may be associated with increasing myocardial ischemia or malignant arrhythmias. Levosimendan, a new calcium sensitizer, with its little effect on myocardial oxygen demand is better tolerated by patients with acute coronary syndromes. We evaluated the acute effects of levosimendan on hemodynamics and coronary flow velocities in patients with left ventricular (LV) dysfunction undergoing percutaneous coronary interventions (PCIs) for an acute myocardial infarction (AMI).

METHODS

Patients with AMI and LV dysfunction undergoing primary PCI were randomized to intravenous infusion of levosimendan (10 minutes bolus with 12 microg/kg followed by 0.1 microg/kg per minute for 24 hours) or placebo, 10 minutes after a primary PCI. Evaluation of hemodynamics and of coronary flow reserve (CFR) were performed at baseline and after bolus.

RESULTS

Twenty-six consecutive patients (mean age 57 +/- 5.4 years, 18 males) were included into the study. At baseline, mean values of hemodynamics and coronary flow velocities were comparable between groups. After bolus, patients with levosimendan (n = 12) showed a significant decrease of pulmonary capillary wedge pressure (from 24 to 19 mm Hg) and a significant increase of cardiac index (from 1.8 to 2.4 L/m2 per minute) resulting in a significant decrease of systemic vascular resistance (from 1366 to 1075 [dyne . s]/cm2). Moreover, CFR on infarct-related artery and on reference vessel significantly improved in patients treated with levosimendan (from 1.6 to 2.0 and from 2.1 to 2.4, respectively). On the other hand, no statistically significant changes have been observed in the placebo group (n = 14).

CONCLUSIONS

Levosimendan, given intravenously after a PCI procedure in patients with AMI and LV dysfunction, significantly improves hemodynamics and CFR, compared with placebo.

Quantitative assessment of harmonic power doppler myocardial perfusion imaging with intravenous Levovist in patients with myocardial infarction: comparison with myocardial viability evaluated by coronary flow reserve and coronary flow pattern of infarct-related artery

Background

Myocardial contrast echocardiography and coronary flow velocity pattern with a rapid diastolic deceleration time after percutaneous coronary intervention has been reported to be useful in assessing microvascular damage in patients with acute myocardial infarction.

Aim

To evaluate myocardial contrast echocardiography with harmonic power Doppler imaging, coronary flow velocity reserve and coronary artery flow pattern in predicting functional recovery by using transthoracic echocardiography.

Methods

Thirty patients with anterior acute myocardial infarction underwent myocardial contrast echocardiography at rest and during hyperemia and were quantitatively analyzed by the peak color pixel intensity ratio of the risk area to the control area (PIR). Coronary flow pattern was measured using transthoracic echocardiography in the distal portion of left anterior descending artery within 24 hours after recanalization and we assessed deceleration time of diastolic flow velocity. Coronary flow velocity reserve was calculated two weeks after acute myocardial infarction. Left ventricular end-diastolic volumes and ejection fraction by angiography were computed.

Results

Pts were divided into 2 groups according to the deceleration time of coronary artery flow pattern (Group A; 20 pts with deceleration time ≧ 600 msec, Group B; 10 pts with deceleration time < 600 msec). In acute phase, there were no significant differences in left ventricular end-diastolic volume and ejection fraction (Left ventricular end-diastolic volume 112 ± 33 vs. 146 ± 38 ml, ejection fraction 50 ± 7 vs. 45 ± 9 %; group A vs. B). However, left ventricular end-diastolic volume in Group B was significantly larger than that in Group A (192 ± 39 vs. 114 ± 30 ml, p < 0.01), and ejection fraction in Group B was significantly lower than that in Group A (39 ± 9 vs. 52 ± 7%, p < 0.01) at 6 months. PIR and coronary flow velocity reserve of Group A were higher than Group B (PIR, at rest: 0.668 ± 0.178 vs. 0.248 ± 0.015, p < 0.0001: during hyperemia 0.725 ± 0.194 vs. 0.295 ± 0.107, p < 0.0001; coronary flow velocity reserve, 2.60 ± 0.80 vs. 1.31 ± 0.29, p = 0.0002, respectively).

Conclusion

The preserved microvasculature detecting by myocardial contrast echocardiography and coronary flow velocity reserve is related to functional recovery after acute myocardial infarction.

Effect of acute myocardial infarction on the utility of fractional flow reserve for the physiologic assessment of the severity of coronary artery narrowing

Fractional flow reserve (FFR) has been shown to be a useful physiologic index of coronary lesion severity in myocardial beds of patients without prior infarction and in those with remote infarction. Acute myocardial infarction (AMI) causes myocardial necrosis and microvascular stunning, embolization, and damage. Whether FFR remains a useful index of epicardial flow in the setting of recent myocardial infarction is not established. Cardiac risk factors, serum troponin I, angiographic minimal lumen diameter (MLD), percent diameter stenosis (DS), lesion length, vessel reference diameter, hyperemic central aortic pressure, hyperemic pressure distal to stenosis, and FFR were compared in 43 vessels subtending recent AMI beds to 25 control vessels, matched by lesion length and MLD, in patients without AMI. There were no differences in DS, MLD, lesion length, or reference diameter between AMI and non-AMI groups. Patients with AMI had mean troponin I levels of 91.8 +/- 162 ng/ml. Left ventricular ejection fraction was significantly lower in patients with than without AMI (55 +/- 9% vs 62 +/- 8%, p <0.05). There were no significant differences in hyperemic central aortic pressure (92 +/- 13 vs 99 +/- 15 mm Hg, p = NS), hyperemic pressure distal to the stenosis (62 +/- 17 vs 66 +/- 19 mm Hg, p = NS), or FFR (0.67 +/- 17 vs 0.68 +/- 17, p = NS) between recent AMI and non-AMI control patients. There was a significant correlation between DS and FFR for both patients with (p <0.001) and without (p = 0.003) infarctions. Thus, FFR and the relation between FFR and DS of lesions subtending AMI was not significantly different from FFR of angiographically matched lesions in patients without AMI.

Frame count reserve

BACKGROUND

The Doppler wire-derived (relative) coronary flow velocity reserve (CVR) that is used to evaluate functional significance of a coronary stenosis is a method performed only by interventional cardiologists. An angiographic method would be useful in the diagnostic catheterization laboratory. For this purpose, we investigated the relation between TIMI frame count reserve (FCR) and CVR.

METHODS AND RESULTS

In 38 patients, (relative) FCR of left anterior descending (LAD) and left circumflex coronary artery (LCx) was calculated by using manual, synchronized contrast agent injections and compared with (relative) CVR. In addition, vessel length was measured with an intracoronary guidewire and frame count flow velocity was calculated and compared with average peak velocity. There was a strong correlation between FCR and CVR (r=0.62, P<0.001) and between relative FCR and relative CVR (r=0.84, P<0.001). The LAD was significantly longer than the LCx (mean, 14.3+/-1.6 cm versus 11.4+/-1.8 cm, P<0.001), and, therefore, TIMI frame count of LAD was significantly higher than of LCx (mean basal 32.5+/-15.1 versus 23.6+/-9.1 and hyperemic 12.1+/-6.6 versus 8.7+/-3.2, both P<0.02). However, all flow velocity measurements and estimations of volume flow were not different for LAD compared with LCx. There were also no differences between mean FCR and CVR of LAD or LCx, of both vessels compared with each other and between mean relative FCR and relative CVR.

CONCLUSIONS

The (relative) frame count reserve can be used to estimate (relative) coronary flow velocity reserve.