Time course of impaired coronary flow reserve after reperfusion in patients with acute myocardial infarction

Impact of cardiac history and myocardial scar on increase of myocardial perfusion after revascularization

PURPOSE

We sought to assess the impact of coronary revascularization on myocardial perfusion and fractional flow reserve (FFR) in patients without a cardiac history, with prior myocardial infarction (MI) or non-MI percutaneous coronary intervention (PCI). Furthermore, we studied the impact of scar tissue.

METHODS

Symptomatic patients underwent [15O]H2O positron emission tomography (PET) and FFR before and after revascularization. Patients with prior CAD, defined as prior MI or PCI, underwent scar quantification by magnetic resonance imaging late gadolinium enhancement.

RESULTS

Among 137 patients (87% male, age 62.2 ± 9.5 years) 84 (61%) had a prior MI or PCI. The increase in FFR and hyperemic myocardial blood flow (hMBF) was less in patients with prior MI or non-MI PCI compared to those without a cardiac history (FFR: 0.23 ± 0.14 vs. 0.20 ± 0.12 vs. 0.31 ± 0.18, p = 0.02; hMBF: 0.54 ± 0.75 vs. 0.62 ± 0.97 vs. 0.91 ± 0.96 ml/min/g, p = 0.04). Post-revascularization FFR and hMBF were similar across patients without a cardiac history or with prior MI or non-MI PCI. An increase in FFR was strongly associated to hMBF increase in patients without a cardiac history or with prior MI/non-MI PCI (r = 0.60 and r = 0.60, p < 0.01 for both). Similar results were found for coronary flow reserve. In patients with prior MI scar was negatively correlated to hMBF increase and independently predictive of an attenuated CFR increase.

CONCLUSIONS

Post revascularization FFR and perfusion were similar among patients without a cardiac history, with prior MI or non-MI PCI. In patients with prior MI scar burden was associated to an attenuated perfusion increase.

Coronary Microcirculation: The Next Frontier in the Management of STEMI

Although the widespread adoption of timely invasive reperfusion strategies over the last two decades has significantly improved the prognosis of patients with ST-segment elevation myocardial infarction (STEMI), up to half of patients after angiographically successful primary percutaneous coronary intervention (PCI) still have signs of inadequate reperfusion at the level of coronary microcirculation. This phenomenon, termed coronary microvascular dysfunction (CMD), has been associated with impaired prognosis. The aim of the present review is to describe the collected evidence on the occurrence of CMD following primary PCI, means of assessment and its association with the infarct size and clinical outcomes. Therefore, the practical role of invasive assessment of CMD in the catheterization laboratory, at the end of primary PCI, is emphasized, with an overview of available technologies including thermodilution- and Doppler-based methods, as well as recently developing functional coronary angiography. In this regard, we review the conceptual background and the prognostic value of coronary flow reserve (CFR), index of microcirculatory resistance (IMR), hyperemic microvascular resistance (HMR), pressure at zero flow (PzF) and angiography-derived IMR. Finally, the so-far investigated therapeutic strategies targeting coronary microcirculation after STEMI are revisited.

The Role of Coronary Physiology in Contemporary Percutaneous Coronary Interventions

Invasive assessment of coronary physiology has radically changed the paradigm of myocardial revascularization in patients with coronary artery disease. Despite the prognostic improvement associated with ischemia-driven revascularization strategy, functional assessment of angiographic intermediate epicardial stenosis remains largely underused in clinical practice. Multiple tools have been developed or are under development in order to reduce the invasiveness, cost, and extra procedural time associated with the invasive assessment of coronary physiology. Besides epicardial stenosis, a growing body of evidence highlights the role of coronary microcirculation in regulating coronary flow with consequent pathophysiological and clinical and prognostic implications. Adequate assessment of coronary microcirculation function and integrity has then become another component of the decision-making algorithm for optimal diagnosis and treatment of coronary syndromes. This review aims at providing a comprehensive description of tools and techniques currently available in the catheterization laboratory to obtain a thorough and complete functional assessment of the entire coronary tree (both for the epicardial and microvascular compartments).

The temporal recovery of fractional flow reserve, coronary flow reserve and index of microcirculatory resistance following myocardial infarction

PURPOSE OF REVIEW

The purpose of this review was to summarize the healing processes after myocardial infarction (MI) and to relate these temporal changes to data from serial imaging obtained by cardiac magnetic resonance, and then to relate these findings to the invasive measures of the indices of coronary physiology (e.g., fractional flow reserve, coronary flow reserve and index of microcirculatory resistance).

RECENT FINDINGS

Indices of coronary physiology measured with an intracoronary wire represent an easily and readily available diagnostic tool for the management of coronary artery disease. Additionally, they give insight into the functional status of the coronary microvasculature. Recent evidence has confirmed initial observations that microvascular recovery occurs after MI and that this is reflected by a progressive improvement of all the indices of coronary physiology over time. More importantly, it has been clarified that this process is variable, but probably predictable as it is affected by the degree of microvascular injury occurring in the acute phase of MI.

SUMMARY

Microvascular recovery after acute MI affects the measurement of the indices of coronary physiology. Use of fractional flow reserve, coronary flow reserve and index of microcirculatory resistance requires an understanding of how microvasculature evolves after MI. This understanding allows appropriate application of intracoronary physiology both clinically and in research settings.

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

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

Estimation of infarct size using transthoracic Doppler echocardiographic measurement of coronary flow reserve in infarct related and reference coronary artery

BACKGROUND

Patients in chronic phase of myocardial infarction (MI) have decreased coronary flow reserve (CFR) in infarct related artery (IRA) that is proportional to the extent of microvascular/myocardial damage. We proposed a novel model for the assessment of microvascular damage and infarct size using Doppler echocardiography evaluation of CFRs of the IRA (LAD) and reference artery (RCA).

METHODS

Our study included 34 consecutive patients (28 men, mean age 50 ± 11 years) with first anterior STEMI and single vessel disease successfully treated with primary PCI. All patients underwent SPECT MPI for the assessment of infarct size (expressed as a percentage of myocardium with fixed perfusion abnormalities) and CFR evaluation of LAD and RCA. CFR derived percentage of microvascular damage (CFR PMD) was calculated as: CFR PMD=(CFR RCA-CFR LAD)/(CFR RCA-1)×100 (%).

RESULTS

CFR PMD correlated significantly with all parameters evaluating the severity of myocardial damage including: peak CK activity (r=0.632, p<0.001), WMSI (r=0.857, p<0.001), ejection fraction (r=-0.820, p<0.001), left ventricular end diastolic (r=0.757, p<0.001) and end systolic volume (r=0.794, p<0.001). Most importantly, CFR PMD (22 ± 17%) correlated significantly with infarct size by SPECT MPI (21 ± 17%) (r=0.874, p<0.001).

CONCLUSIONS

CFR PMD derived from the proposed model was significantly related to echocardiographic and enzymatic parameters of infarct size, as well as to myocardial damage assessed by SPECT MPI in patients with successfully reperfused first anterior STEMI.

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.

Concurrent Microvascular and Infarct Remodeling After Successful Reperfusion of ST-Elevation Acute Myocardial Infarction

Background—

Connection between the course of microvascular and infarct remodeling processes over time after reperfused ST-elevation acute myocardial infarction has not been fully elucidated. The aim of this study is to investigate the association of temporal changes in hemodynamics of microcirculation in the infarcted territory and infarct size (IS) after primary percutaneous coronary intervention in patients with ST-elevation acute myocardial infarction.

Methods and Results—

Thirty-five patients admitted with ST-elevation acute myocardial infarction undergoing primary percutaneous coronary intervention were enrolled in the study. Coronary flow reserve (CFR), index of microvascular resistance (IMR), and IS were assessed 2 days after primary percutaneous coronary intervention and at the 5-month follow-up. The predictors of the 5-month IS were the baseline values of IS (β=0.6, P <0.001), IMR (β=0.280, P =0.013), and CFR (β=−0.276, P =0.017). There were significant correlations between relative change in IS and relative change in measures of microvascular function (IS and CFR [ r =−0.51, P =0.002]); IS and IMR ([ r =0.55, P =0.001]). In multivariate model, relative changes in IMR (β=0.552, P =0.001) and CFR (β=−0.511, P =0.002) were the only predictors of relative change in IS. In patients with an improvement in IMR >33%, the mean IS decreased from 32.3±16.9% to 19.3±14% ( P =0.001) in the follow-up. Similarly, in patients with an improvement in CFR >41%, the mean IS significantly decreased from 29.9±20% to 15.8±12.4% ( P =0.003). But in patients with an improvement in IMR and CFR, which were below than the mean values, IS did not significantly decrease during the follow-up.

Conclusions—

Improvement in microvascular function in the infarcted territory is associated with reduction in IS after reperfused ST-elevation acute myocardial infarction. This link suggests that further investigations are warranted to determine whether therapeutic protection of microvascular integrity results in augmentation of infarct healing.

Predictive value of the index of microcirculatory resistance in patients with ST-segment elevation myocardial infarction

OBJECTIVES

The objective of this study is to evaluate the predictive value of the index of microcirculatory resistance (IMR) in patients undergoing primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

Despite adequate epicardial artery reperfusion, a number of patients with STEMI have a poor prognosis because of microvascular damage. Assessing the status of the microvasculature in this setting remains challenging.

METHODS

In 29 patients after primary PCI for STEMI, IMR was measured with a pressure sensor/thermistor-tipped guidewire. The Thrombolysis In Myocardial Infarction (TIMI) myocardial perfusion grade, TIMI frame count, coronary flow reserve, and ST-segment resolution were also recorded.

RESULTS

The IMR correlated significantly with the peak creatinine kinase (CK) (R = 0.61, p = 0.0005) while the other measures of microvascular dysfunction did not. In patients with an IMR greater than the median value of 32 U, the peak CK was significantly higher compared with those having values <or=32 U (3,128 +/- 1,634 ng/ml vs. 1,201 +/- 911 ng/ml, p = 0.002). The IMR correlated significantly with 3-month echocardiographic wall motion score (WMS) (R = 0.59, p = 0.002) while the other measures of microvascular function did not. The WMS at 3-month follow-up was significantly worse in the group with an IMR >32 U compared with <or=32 U (28 +/- 7 vs. 20 +/- 4, p = 0.001). On multivariate analysis, IMR was the strongest predictor of peak CK and 3-month WMS. The IMR was the only significant predictor of recovery of left ventricular function on the basis of the percent change in WMS (R = 0.50, p < 0.01).

CONCLUSIONS

Compared to standard measures, IMR appears to be a better predictor of microvascular damage after STEMI, both acutely and in short term follow-up.

Nitrate-enhanced gated SPECT in patients with primary angioplasty for acute myocardial infarction: evidence of a reversible and nitrate-sensitive impairment of myocardial perfusion

PURPOSE

Reperfusion of myocardial infarction (MI) leads to a reversible dysfunction of coronary vessels. We hypothesised that vasodilating drugs such as nitrates might improve sestamibi uptake within viable areas of recently reperfused MI, thereby enhancing prediction of subsequent improvements in perfusion and contractility. This study was aimed at assessing nitrate-enhanced sestamibi gated SPECT after MI reperfusion.

METHODS

Twenty-nine patients underwent rest followed by nitrate sestamibi gated SPECT at 9 +/- 3 days after primary angioplasty for acute MI and at follow-up, 4-10 months later. Four MBq/kg of (99m)Tc-sestamibi was injected at rest, and 12 MBq/kg after nitroglycerin spray.

RESULTS

Follow-up improvements were documented for both perfusion (P+) and contractility (C+) in 18% of the 180 initially abnormal segments, in neither perfusion (P-) nor contractility (C-) in 44%, in contractility only (C+P-) in 16% and in perfusion only (C-P+) in 22%. Perfusion improvement was related to lower sestamibi uptake on baseline rest SPECT (P+: 42 +/- 15% vs P-: 50 +/- 15%, p = 0.001) and, moreover, to a higher increase between rest and nitrate uptake (P+: +9.5 +/- 6.5% vs P-: +2.0 +/- 5.9%, p < 0.001). Contractility improvement was related to sestamibi uptake on baseline nitrate SPECT (C+: 58 +/- 15% vs C-: 38 +/- 16%, p < 0.001), a variable enhancing the prediction provided by sestamibi uptake at rest (p < 0.05).

CONCLUSION

The improvement in perfusion which is documented in the months following MI reperfusion is predicted by initial nitrate enhancement of sestamibi uptake, suggesting a mechanism of reversible vascular injury. In this particular setting, sestamibi uptake is a better predictor of contractility recovery when determined after nitrate administration rather than under conventional resting conditions.

Restoration of microvascular function in the infarct-related artery by intracoronary transplantation of bone marrow progenitor cells in patients with acute myocardial infarction: the Doppler Substudy of the Reinfusion of Enriched Progenitor Cells and Infarct Remodeling in Acute Myocardial Infarction (REPAIR-AMI) trial

BACKGROUND

The Doppler Substudy of the randomized, double-blind, placebo-controlled Reinfusion of Enriched Progenitor Cells and Infarct Remodeling in Acute Myocardial Infarction (REPAIR-AMI) trial aimed to investigate the effects of intracoronary infusion of bone marrow-derived progenitor cells (BMCs) on coronary blood flow regulation in patients with reperfused acute myocardial infarction.

METHODS AND RESULTS

In a total of 58 patients (BMC group, n=30; placebo group, n=28), coronary flow reserve (CFR) in the infarct artery and a reference vessel was assessed by intracoronary Doppler at the time of study therapy (4.2+/-0.1 days after acute myocardial infarction) and at the 4-month follow-up. Initial CFR was reduced in the infarct artery compared with the reference vessel in both groups (BMC: 2.0+/-0.1 versus 2.9+/-0.2, P<0.05; placebo: 1.9+/-0.1 versus 2.8+/-0.2; P<0.05). At the 4-month follow-up, CFR in the infarct artery had slightly improved in the placebo group (+0.88+/-0.18; P<0.001 versus initial) but was markedly increased by 90% (+1.80+/-0.25; P=0.005 versus placebo) in BMC-treated patients, resulting in a normalization of CFR (3.8+/-0.2; P<0.001 versus initial and placebo at 4 months). In the infarct vessel, adenosine-induced minimal vascular resistance index declined slightly in the placebo group (from 1.77+/-0.12 to 1.52+/-0.15 mm Hg x s/cm; P<0.05) but considerably decreased by -29+/-6% in the BMC group (from 1.86+/-0.19 to 1.20+/-0.12 mm Hg x s/cm; P<0.05 versus initial and placebo at 4 months).

CONCLUSIONS

Intracoronary BMC therapy after acute myocardial infarction restores microvascular function of the infarct-related artery, which is associated with a significant improvement in maximal vascular conductance capacity. These data provide clinical proof of concept that progenitor cell transplantation promotes vascular repair.

Normalization of coronary blood flow in the infarct-related artery after intracoronary progenitor cell therapy: intracoronary Doppler substudy of the TOPCARE-AMI trial

BACKGROUND

Coronary microvascular dysfunction contributes to infarct extension and poor prognosis after an acute myocardial infarction (AMI). Recently, progenitor cell application has been demonstrated to improve neovascularization and myocardial function after experimental myocardial infarction. Therefore, we investigate coronary blood flow regulation in patients after AMI treated with intracoronary progenitor cell therapy.

METHODS AND RESULTS

In the TOPCARE-AMI trial, patients received either bone marrow-derived or circulating progenitor cells into the infarct-related artery 3-7 days after AMI. The present substudy investigates in 40 patients coronary blood flow regulation at the time of progenitor cell therapy and at 4-month follow-up by i.c. Doppler in the infarct artery as well as a reference vessel. At the initial measurement, coronary flow reserve (CFR) was reduced in the infarct artery compared to the reference vessel (median 2.5 vs. 3.4, p<0.001). At 4-month follow-up, intracoronary progenitor cell therapy was associated with a normalization of CFR in the infarct artery (median 3.9 vs. reference vessel 3.8, p=0.15). CFR also improved in the reference vessel, but mechanisms were different: reference vessel increase in CFR was secondary to an increased basal vascular resistance, probably due to reduced need for hypercontractility. In contrast, in the infarct artery, adenosine-induced minimal vascular resistance profoundly decreased, indicating an increased maximal coronary vascular conductance capacity. In addition, in a non-randomized matched control group (n=8), minimal vascular resistance in the infarct artery was significantly elevated compared to progenitor cell treated patients 4 months after AMI (p=0.012).

CONCLUSIONS

Intracoronary progenitor cell therapy after AMI is associated with complete restoration of coronary flow reserve due to a substantial improvement of maximal coronary vascular conductance capacity. The clinical importance of improved microcirculation by progenitor cell therapy in patients after AMI has to be established in further randomized trials.

Time course of microvascular resistance of the infarct and noninfarct coronary artery following an anterior wall acute myocardial infarction

Previous studies have suggested that coronary flow velocity reserve (CFVR) in the early phase of acute myocardial infarction (AMI) is abnormal in infarcted and remote regions. This study determined the coronary microvascular resistance of infarct-related arteries (IRAs) and non-IRAs during AMI and at follow-up in patients who were treated with primary percutaneous intervention. In 73 patients with a first anterior wall AMI, baseline and minimal microvascular resistance in IRAs and non-IRAs immediately after reperfusion and at 1-week and 6-month follow-up were calculated as the ratio of mean transvascular pressure gradient to mean baseline and to adenosine-induced hyperemic blood flow velocity, respectively. CFVR in IRAs increased from 1.6 +/- 0.4 after reperfusion to 1.9 +/- 0.5 at 1 week and to 3.0 +/- 0.8 at 6 months (p <0.0001) and in non-IRAs from 2.4 +/- 0.5 to 2.7 +/- 0.6 at 1 week to 3.3 +/- 0.6 at 6 months (p <0.0001). Minimal microvascular resistance in IRAs and non-IRAs (3.2 +/- 1.7 and 2.2 +/- 0.6 mm Hg/second/cm, respectively) decreased significantly at follow-up (2.0 +/- 0.6 and 1.7 +/- 0.6 mm Hg/second/cm at 1 week and 1.8 +/- 0.6 and 1.8 +/- 0.7 mm Hg/second/cm at 6 months, respectively). After correction for rate-pressure product, baseline microvascular resistance after reperfusion and at 6 months did not significantly differ between IRAs and non-IRAs. In conclusion, minimal microvascular resistance is higher in infarcted and noninfarcted regions during AMI than at follow-up. The low CFVR in remote regions during AMI is probably due more to disturbed autoregulation than to increased myocardial workload.

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.

Usefulness of coronary flow reserve immediately after primary coronary stenting in predicting wall motion recovery in patients with anterior wall acute myocardial infarction

This study examined whether coronary flow reserve (CFR) measured immediately after primary coronary stenting could predict wall motion recovery in patients who have acute myocardial infarction. CFR significantly correlated with the change of wall motion score (r = 0.68, p <0.0001), and the optimal cut-off value of CFR for predicting wall motion recovery was 1.4 (sensitivity 85%, specificity 94%).

Convalescent stage coronary flow reserve and late myocardial morphologic outcomes in patients with first anterior acute myocardial infarction

BACKGROUND

Microvascular damage immediately after reperfusion therapy is an independent predictor of left ventricular function in patients with acute myocardial infarction (AMI). However, its recovery may vary among individuals and the relationship between convalescent stage microvasculature and late myocardial morphologic change is unclear.

METHODS AND RESULTS

Patients treated with coronary angioplasty within 12 h of their first anterior AMI were enrolled in this study. Coronary flow reserve (CFR) was measured 3 weeks post AMI, in both branches of the left coronary artery: culprit (left anterior descending artery: LAD) and non-culprit (left circumflex artery: LCX). Left ventriculography was performed at 3 weeks and 6 months post AMI and compared. Seventeen patients showed abnormal CFR in the LAD (Group 1: CFR<2), whereas 20 patients showed normal CFR (Group 2: CFR >/=2). Percent changes of end-diastolic volume tended to be higher in Group 1 than in Group 2 (11.8+/-21.6% vs -1.3+/-14.4%, p=0.056), and %changes of end-systolic volume was significantly smaller in Group 2 (11.8+/-22.1% vs -8.7+/-25.1%, p<0.05). A statistically significant correlation was found between absolute and relative CFR in the LAD and %change of end-systolic volume (r=-0.58: p<0.001, and r=0.40: p<0.05, respectively).

CONCLUSIONS

Microvascular function in the convalescent stage may be related to these favorable changes.

Coronary Flow Reserve after Coronary Intervention is Similar in Patients with Preserved Viability in Previous Myocardial Infarction and in Those with Angina Pectoris

The relationship between coronary flow reserve (CFR) and viability in the infarcted myocardium has not been fully clarified. We measured coronary blood flow velocity immediately after coronary intervention (with percutaneous transluminal coronary angioplasty [PTCA] or stenting) in 38 patients with previous myocardial infarction and preserved viability and 48 with angina pectoris. CFR was calculated and was similar between the two patient groups. No differences in the incidence of post-intervention CFR > 2.0 were detected; there were no differences in postintervention CFR between patients with preserved myocardial viability and those with angina pectoris who underwent PTCA. Coronary stenting reduced the percentage diameter stenosis in both groups compared with PTCA and slightly increased the post-intervention CFR. No differences were, however, detected in postintervention CFR between patients with preserved myocardial viability and those with angina pectoris who underwent additional stenting. These results reveal that in patients with preserved myocardial viability, post-intervention CFR was restored to values similar to those in patients with angina pectoris.

[Late recovery of coronary flow reserve in patients successfully treated with a percutaneous procedure]

INTRODUCTION AND OBJECTIVES

Coronary angiograms are of limited value for the assessment of the results of percutaneous interventions. Intracoronary Doppler studies have been used to overcome these difficulties. The achievement of a coronary flow reserve (CFR) > 2-2.5 after the procedure is considered a good result and further optimization is generally not required. However, coronary flow reserve may not recover immediately, despite optimal procedural results. The aim of this study is to assess the temporal course of the recovery of coronary flow reserve after successful revascularization.

PATIENTS AND METHOD

We studied 34 patients with coronary heart disease who were successfully treated by balloon angioplasty (n = 8) or stent implantation (n = 26). In all patients, serial observations were made by quantitative angiography and intracoronary Doppler (0.014 = flow-wire). Patients were studied: a) before treatment; b) immediately after, and c) 8 3 months later.

RESULTS

The baseline coronary flow reserve was 1.3 0.4 and increased to 2.4 0.8 after the procedure (p < 0.01). At 8 months follow-up there was a significant increase (3 0.8; p < 0.01). This late improvement in coronary flow reserve was associated with a decline in average peak velocity at follow-up. Patients with impaired CFR immediately after treatment had a greater increase in CFR during followup than those with CFR > 2 after treatment (1.4 0.9 vs 0.4 0.6; p < 0.01).

CONCLUSIONS

After a successful coronary intervention, CFR increases immediately, but some patients may experience additional improvement during follow-up. This increase was greater in patients who showed less improvement in coronary flow reserve immediately after treatment. Our findings suggest that the use of Doppler parameters in the immediate assessment of percutaneous coronary intervention results have limitations.

Myocardial viability, coronary flow reserve, and in-hospital predictors of late recovery of contractility following successful primary stenting for acute myocardial infarction

OBJECTIVE

To assess the relation between myocardial viability, coronary flow reserve, and recovery of myocardial contractility after stenting for acute myocardial infarction.

DESIGN

Consecutive sample prospective study.

SETTING

University hospital.

PATIENTS

41 patients with single vessel disease and successful primary stenting for a first acute myocardial infarction.

INTERVENTIONS

(201)Tl single photon emission computed tomography, contrast ventriculography, and intracoronary Doppler performed 7 (1) days after primary stenting.

MAIN OUTCOME MEASURES

Regional contractility recovery assessed by contrast ventriculography at 6 (1) months' follow up.

RESULTS

On univariate analysis, contractility recovery was correlated to prereperfusion anterograde and collateral flow grades (r = 0.41, p = 0.03 and r = 0.55, p = 0.0004), viability index (r = 0.55, p = 0.04), peak creatine kinase concentrations (r = -0.55, p = 0.0005), left ventricular ejection fraction (r = 0.45, p = 0.005), end diastolic pressure (r = -0.62, p < 0.0001), end systolic volume index (r = -0.47, p = 0.01), and the extent of hypokinetic area (r = -0.48, p = 0.003), but not the coronary flow reserve. On multivariate analysis, independent predictors of late contractility recovery were prereperfusion anterograde and collateral flow grades and viability index. Relative coronary flow reserve, reflecting the culprit vessel's microvascular function, was correlated only to the extent of the infarct risk area (r = -0.45, p = 0.003).

CONCLUSIONS

Independent predictors of contractility recovery between the seventh day and the sixth month after successful stenting for acute myocardial infarction are prereperfusion anterograde and collateral flows and myocardial viability. The culprit vessel's microvascular dysfunction is independent of myocardial viability and contractility and correlated to the extent of "jeopardised microvasculature".

Assessment of myocardial viability using coronary zero flow pressure after successful angioplasty in patients with acute anterior myocardial infarction

OBJECTIVES

To investigate the relation between coronary flow reserve (CFR), coronary zero flow pressure (Pzf), and residual myocardial viability in patients with acute myocardial infarction.

DESIGNS

Prospective study.

SETTING

Primary care hospital.

PATIENTS

27 consecutive patients with acute anterior myocardial infarction.

MAIN OUTCOME MEASURES

F-fluorodeoxyglucose (FDG) positron emission tomography (PET) was used in 27 patients who underwent successful intervention within 12 hours of onset of a first acute anterior myocardial infarction. Within three days before discharge they had < 25% stenosis in the culprit lesion as determined by angiography 24 (3) days after acute myocardial infarction. Pzf and the slope index of the flow-pressure relation (SIFP) were calculated from the simultaneously recorded aortic pressure and coronary flow velocity signals at peak hyperaemia.%FDG was quantified by comparing FDG uptake in the infarct myocardium with FDG uptake in the normal myocardium.

RESULTS

There was a correlation between %FDG and CFR, where y = -1.477x + 62.517, r = -0.072 (NS). There was also a correlation between %FDG and SIFP, where y = -0.975x + 60.542, r = -0.045 (NS), and a significant correlation between %FDG and Pzf, where y = -0.98x + 85.108, r = -0.696 (p < 0.001).

CONCLUSIONS

CFR does not correlate with FDG-PET at the time of postreperfusion evaluation of residual myocardial viability. The parameter that correlates best with residual myocardial viability is Pzf and this may be a useful index for predicting patient prognosis.

Coronary vasodilator reserve: a clue to the explanation of (201)Tl redistribution patterns early after successful primary stenting for acute myocardial infarction

OBJECTIVES

We sought to assess the mechanism and significance of different (201)Tl redistribution patterns after successful primary stenting following acute myocardial infarction (AMI).

BACKGROUND

The mechanism of (201)Tl reverse redistribution and the impact of different redistribution patterns on the recovery of contractility after successful reperfusion therapy for AMI remain unclear.

METHODS

We studied 41 consecutive patients with successful primary stenting for a first AMI. Patients underwent predischarge and six-month follow-up dipyridamole stress-reinjection single photon emission tomography (SPECT), coronary and left ventricular angiography. Intracoronary Doppler assessment of coronary flow reserve (CFR) was performed before discharge.

RESULTS

Four patient groups were identified according to predischarge SPECT: patients with I: nonreversible defects (n = 8), II: redistribution (n = 7), III: reverse redistribution (n = 21), IV: no defect (n = 5). At follow-up contractility recovery increased in a stepwise fashion from groups I to IV (19 +/- 41%, 40 +/- 53%, 70 +/- 28%, 78 +/- 33%, p = 0.01). Compared with patients with redistribution, those with reverse redistribution had lower infarct-related artery (IRA) CFR (2.2 +/- 0.5 vs. 2.8 +/- 0.9, p = 0.03) but higher contractility recovery.

CONCLUSIONS

Variable (201)Tl redistribution patterns, early after successful stenting for AMI, may predict different degrees of late contractility recovery. The lower IRA CFR and the higher contractility recovery in areas with reverse redistribution suggest more severe microvascular dysfunction and less severe myocardial injury in such areas compared with those with redistribution.

Early dysfunction and long-term improvement in endothelium-dependent vasodilation in the infarct-related artery after thrombolysis

OBJECTIVES

This study assessed the degree of endothelial dysfunction in post-acute myocardial infarction (AMI) and its subsequent status in the infarct-related artery (IRA) in patients treated with thrombolysis.

BACKGROUND

Coronary flow reserve alterations in the IRA after thrombolysis have been described, but the endothelium-dependent vasomotion has not been investigated, to date.

METHODS

Endothelial function in patients after thrombolysis was assessed by infusion of acetylcholine (ACh) at increasing doses in the IRA. Diameter changes in the distal segments were evaluated using quantitative coronary angiography. Patients with coronary atherosclerosis constituted the control group. Clinical variables, electrocardiography and biochemical markers were used to determine the timing of reperfusion and the extent of the infarct. Patients in the AMI group were re-evaluated one year later.

RESULTS

In the initial assessment, 16 patients showed a vasoconstriction response to ACh in the IRA compared to the control group (-20 +/- 21% vs. 4 +/- 4%; p < 0.01). Significant correlations between the degree of vasoconstriction and maximum value of the creatine kinase-MB fraction and number of new Q waves were observed. Of the 12 patients re-evaluated, 4 had complete occlusion of the IRA. In the remaining eight patients with patent artery, an improvement in response to ACh was observed relative to the initial study (+3 +/- 11%, vs. -19 +/- 15%, p < 0.05).

CONCLUSIONS

In patients with AMI treated with thrombolysis, severe endothelial dysfunction in the IRA is observed early. In patients who retain patency of the IRA, the endothelial dysfunction improves during the follow-up and suggests a component of stunned endothelium in the first few days post-AMI.

Relationship between extent of residual myocardial viability and coronary flow reserve in patients with recent myocardial infarction

BACKGROUND

The presence of viability in an infarct zone implies an intact microvasculature. We hypothesized that coronary flow reserve (CFR), which assesses the microcirculation, would correlate with the extent of viability in infarction zones.

METHODS

CFR was measured after stenting in 17 patients with single vessel disease >48 hours from infarction. Viability was determined with use of single-photon emission computed tomography sestamibi imaging.

RESULTS

Sestamibi uptake in the infarct zone correlated with CFR in the infarct artery (r = 0.62, P =.008) and sestamibi uptake in the infarct zone was greater in patients with normal CFR than in patients with abnormal CFR (61.9 +/- 9.1% vs 46.3 +/- 9.6%, P =.004). In addition, CFR was greater in patients with viability compared with patients without viability (2.4 +/- 1.3 vs 1.4 +/- 0.4, P =.015).

CONCLUSIONS

CFR correlates with the extent of viability after infarction. Preserved CFR in an infarct-related artery implies preserved viability.

Comparative efficacy of primary angioplasty with stent implantation and thrombolysis in restoring basal coronary artery flow in acute ST segment elevation myocardial infarction: quantitative assessment using the corrected TIMI frame count

Following thrombolysis and primary percutaneous transluminal coronary angioplasty (PTCA) for acute ST segment elevation myocardial infarction, basal flow in the culprit artery is known to influence prognosis. The purpose of this study was to determine if differences exist in basal flow in culprit and nonculprit coronary arteries in patients with acute ST segment elevation myocardial infarction who were treated with thrombolysis or primary PTCA with stent implantation. Twenty patients were randomized to thrombolysis (with recombinant tissue plasminogen activator) and 24 to primary PTCA with stent implantation within 3 hours of onset of acute ST segment elevation myocardial infarction. Coronary angiography was performed 90-120 minutes after thrombolysis or immediately after PTCA with stent implantation and again at 18-36 hours after intervention in both groups. Patients who failed to achieve thrombolysis in myocardial infarction (TIMI) grade 2 or 3 flow were excluded. The corrected TIMI frame count was used as the index of basal coronary artery flow. Early after intervention the mean corrected TIMI frame count in the culprit coronary artery was significantly lower in the primary PTCA with stent group (27.4 +/- 7.7 frames) than in the thrombolysis group (39.8 +/- 10 frames, p < 0.001). Eight thrombolysis patients (40%) and 20 primary PTCA patients (83%, p < 0.01) achieved TIMI grade 3 flow early after intervention. By 18-36 hours after intervention there were no significant differences in the mean correct TIMI frame count between the thrombolysis and primary PTCA with stent groups. There were no significant differences in the mean corrected TIMI frame count between these two groups in the nonculprit coronary artery, either early after intervention or at 18-36 hours. In successfully reperfused coronary arteries following acute ST segment elevation myocardial infarction, primary angioplasty with stent implantation reestablished TIMI grade 2 or 3 flow faster and more effectively than thrombolysis did.

Coronary flow velocity immediately after primary coronary stenting as a predictor of ventricular wall motion recovery in acute myocardial infarction

OBJECTIVES

The purpose of this study was to examine the relationship between the pattern of coronary blood flow velocity immediately after successful primary stenting and the recovery of left ventricular (LV) wall motion in patients with acute myocardial infarction (AMI).

BACKGROUND

It is difficult to predict the recovery of LV wall motion immediately after direct angioplasty in AMI. Recent reports indicate that dysfunctional coronary microcirculation is an important determinant of prognosis for AMI patients after successful reperfusion.

METHODS

We measured left anterior descending coronary flow velocity variables using a Doppler guide wire immediately after successful primary stenting in 31 patients with their first anterior AMI. The patients were divided into two groups: those with and those without early systolic reverse flow (ESRF). Changes in LV regional wall motion (RWM) and ejection fraction (EF) at admission and at discharge were compared between the two groups. Coronary flow velocity variables immediately after primary stenting were compared with changes in left ventriculographic indexes.

RESULTS

The change in RWM was significantly greater in the non-ESRF group than it was in the ESRF group (0.9 +/- 0.7 vs. -0.1 +/- 0.3 standard deviation/chord, respectively, p < 0.001). The change in EF was also significantly greater in the non-ESRF group than it was in the ESRF group (10 +/- 10 vs. 1 +/- 6%, respectively, p < 0.05). In the non-ESRF group (diastolic to systolic velocity ratio [DSVR] <3.0), the DSVR correlated positively with the change in RWM (r = 0.60, p < 0.005, n = 24) and the change in EF (r = 0.52, p < 0.01).

CONCLUSIONS

The coronary flow velocity pattern measured immediately after successful primary stenting is predictive of the recovery of regional and global LV function in patients with AMI.

Recanalization versus reperfusion for myocardial survival and preservation of ventricular geometry

This article reviews the factors affecting myocardial ischemia and necrosis beyond coronary obstruction and in particular those related to the function of microcirculation and to the vulnerability of myocardial cells to deprivation as well as to restoration of blood flow. An effort has been spent to distinguish microcirculatory alterations during ischemia, after reversible ischemia, after irreversible ischemia, and in the presence of coronary atherosclerosis, independent of ischemia. Results show that the microcirculation plays a significant role in the production of ischemia and necrosis as well as in the modulation of the effect of large-vessel recanalization. The mechanisms, nature, and reversibility of microcirculatory changes cannot be generalized. They differ under different conditions and are poorly understood. The links of the chain plaque-microcirculation-myocardial cells cannot be separated; an integrated approach is needed to better understand and treat ischemic heart disease.

Effects of various doses of intracoronary verapamil on coronary resistance vessels in humans

To investigate the vasodilatory effect of various doses of intracoronary verapamil on coronary resistance vessels, we studied 13 patients with normal angiograms. A coronary Doppler guide wire was inserted into the left anterior descending coronary artery, and coronary blood flow velocity (CBFV) was measured. Verapamil was injected into the left coronary artery at doses of 0.1 mg, 0.5 mg, 1.0 mg, and 2.0 mg at 10-min intervals. Nitroglycerin was also injected into the same artery to avoid changes in cross-sectional area. As a measure of coronary vascular resistance, coronary vascular resistance index (CVRI) was calculated as the quotient of mean aortic pressure/CBFV. An injection of verapamil produced a dose-dependent increase in CBFV: 79 +/- 38% with 0.1 mg, 131 +/- 56% with 0.5 mg, 143 +/- 46% with 1.0 mg, and 128 +/- 47% with 2.0 mg of verapamil. The percent peak decreases in CVRI were dose dependent: -42 +/- 13% with 0.1 mg, -50 +/- 17% with 0.5 mg, -62 +/- 14% with 1.0 mg, and -60 +/- 9% with 2.0 mg of verapamil. Thus, intracoronary verapamil produces a dose-dependent dilation of coronary resistance vessels, and the optimal effect is produced with an injection of verapamil at a dose of 1.0 mg into the left coronary artery. At this dose, verapamil did not affect atrioventricular conduction.