Coronary Blood Flow Assessment After Successful Angioplasty for Acute Myocardial Infarction Predicts the Risk of Long-Term Cardiac Events

Time course of coronary flow capacity impairment in ST-segment elevation myocardial infarction

BACKGROUND

Microvascular dysfunction in the setting of ST-elevated myocardial infarction (STEMI) plays an important role in long-term poor clinical outcome. Coronary flow reserve (CFR) is a well-established physiological parameter to interrogate the coronary microcirculation. Together with hyperaemic average peak flow velocity, CFR constitutes the coronary flow capacity (CFC), a validated risk stratification tool in ischaemic heart disease with significant prognostic value. This mechanistic study aims to elucidate the time course of the microcirculation as reflected by alterations in microcirculatory physiological parameters in the acute phase and during follow-up in STEMI patients.

METHODS

We assessed CFR and CFC in the culprit and non-culprit vessel in consecutive STEMI patients at baseline (n = 98) and after one-week (n = 64) and six-month follow-up (n = 65).

RESULTS

A significant trend for culprit CFC in infarct size as determined by peak troponin T (p = 0.004), time to reperfusion (p = 0.038), the incidence of final Thrombolysis In Myocardial Infarction 3 flow (p = 0.019) and systolic retrograde flow (p = 0.043) was observed. Non-culprit CFC linear contrast analysis revealed a significant trend in C-reactive protein (p = 0.027), peak troponin T (p < 0.001) and heart rate (p = 0.049). CFC improved both in the culprit and the non-culprit vessel at one-week (both p < 0.001) and six-month follow-up (p = 0.0013 and p < 0.001) compared with baseline.

CONCLUSION

This study demonstrates the importance of microcirculatory disturbances in the setting of STEMI, which is relevant for the interpretation of intracoronary diagnostic techniques which are influenced by both culprit and non-culprit vascular territories. Assessment of non-culprit vessel CFC in the setting of STEMI might improve risk stratification of these patients following coronary reperfusion of the culprit vessel.

Ticagrelor and preconditioning in patients with stable coronary artery disease (TAPER-S): a randomized pilot clinical trial

Background

Ticagrelor is a reversibly binding, direct-acting, oral, P₂Y₁₂ antagonist used for the prevention of atherothrombotic events in patients with coronary artery disease (CAD). Ticagrelor blocks adenosine reuptake through the inhibition of equilibrative nucleoside transporter 1 (ENT-1) on erythrocytes and platelets, thereby facilitating adenosine-induced physiological responses such as an increase in coronary blood flow velocity. Meanwhile, adenosine plays an important role in triggering ischemic preconditioning through the activation of the A1 receptor. Therefore, an increase in ticagrelor-enhanced adenosine bioavailability may confer beneficial effects through mechanisms related to preconditioning activation and improvement of coronary microvascular dysfunction.

Methods

To determine whether ticagrelor can trigger ischemic preconditioning and influence microvascular function, we designed this prospective, open-label, pilot study that enrolled patients with stable multivessel CAD requiring staged, fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI). Participants will be randomized in 1:1 ratios either to ticagrelor (loading dose (LD) 180 mg, maintenance dose (MD) 90 mg bid) or to clopidogrel (LD 600 mg, MD 75 mg) from 3 to 1 days before the scheduled PCI. The PCI operators will be blinded to the randomization arm. The primary endpoint is the delta (difference) between ST segment elevations (in millimeters, mm) as assessed by intracoronary electrocardiogram (ECG) during the two-step sequential coronary balloon inflation in the culprit vessel. Secondary endpoints are 1) changes in coronary flow reserve (CFR), index of microvascular resistance (IMR), and FFR measured in the culprit vessel and reference vessel at the end of PCI, and 2) angina score during inflations. This study started in 2018 with the aim of enrolling 100 patients. Based on the rate of negative FFR up to 30% and a drop-out rate up to 10%, we expect to detect an absolute difference of 4 mm among the study arms in the mean change of ST elevation following repeated balloon inflations. All study procedures were reviewed and approved by the Ethical Committee of the Catholic University of Sacred Heart.

Discussion

Ticagrelor might improve ischemia tolerance and microvascular function compared to clopidogrel, and these effects might translate to better long-term clinical outcomes.

Trial registration

EudraCT No. 2016–004746-28. No. NCT02701140. 

Trial status

Information provided in this manuscript refers to the definitive version (n. 3.0) of the study protocol, dated 31 October 2017, and includes all protocol amendments. Recruitment started on 18 September 2018 and is currently ongoing. The enrollment is expected to be completed by the end of 2019.

Trial sponsor

Fondazione Policlinico Universitario A. Gemelli – Roma, Polo di Scienze Cardiovascolari e Toraciche, Largo Agostino Gemelli 8, 00168 Rome, Italy.

Invasive Assessment of the Coronary Microcirculation in Reperfused ST-Segment-Elevation Myocardial Infarction Patients: Where Do We Stand?

For patients presenting with an acute ST-segment-elevation myocardial infarction, the most effective therapy for reducing myocardial infarct size and preserving left ventricular systolic function is primary percutaneous coronary intervention (PPCI). However, mortality and morbidity remain significant. This is partly attributed to the development of microvascular obstruction, which occurs in around 50% of ST-segment-elevation myocardial infarction patients post-PPCI, and it is associated with adverse left ventricular remodeling and worse clinical outcomes. Although microvascular obstruction can be detected by cardiac imaging techniques several hours post-PPCI, it may be too late to intervene at that time. Therefore, being able to predict the development of microvascular obstruction at the time of PPCI may identify high-risk patients who might benefit from further adjuvant intracoronary therapies, such as thrombolysis, vasodilators, glycoprotein IIb/IIIa inhibitors, and anti-inflammatory agents that may reduce microvascular obstruction. Recent studies have shown that invasive coronary physiology measurements performed during PPCI can be used to assess the coronary microcirculation. In this article, we provide an overview of the various invasive methods currently available to assess the coronary microcirculation in the setting of ST-segment-elevation myocardial infarction, and how they could potentially be used in the future for tailoring therapies to those most at risk.

Wave intensity analysis and its application to the coronary circulation

Wave intensity analysis (WIA) is a technique developed from the field of gas dynamics that is now being applied to assess cardiovascular physiology. It allows quantification of the forces acting to alter flow and pressure within a fluid system, and as such it is highly insightful in ascribing cause to dynamic blood pressure or velocity changes. When co-incident waves arrive at the same spatial location they exert either counteracting or summative effects on flow and pressure. WIA however allows waves of different origins to be measured uninfluenced by other simultaneously arriving waves. It therefore has found particular applicability within the coronary circulation where both proximal (aortic) and distal (myocardial) ends of the coronary artery can markedly influence blood flow. Using these concepts, a repeating pattern of 6 waves has been consistently identified within the coronary arteries, 3 originating proximally and 3 distally. Each has been associated with a particular part of the cardiac cycle. The most clinically relevant wave to date is the backward decompression wave, which causes the marked increase in coronary flow velocity observed at the start of the diastole. It has been proposed that this wave is generated by the elastic re-expansion of the intra-myocardial blood vessels that are compressed during systolic contraction. Particularly by quantifying this wave, WIA has been used to provide mechanistic and prognostic insight into a number of conditions including aortic stenosis, left ventricular hypertrophy, coronary artery disease and heart failure. It has proven itself to be highly sensitive and as such a number of novel research directions are encouraged where further insights would be beneficial.

Role of endothelin in microvascular dysfunction following percutaneous coronary intervention for non-ST elevation acute coronary syndromes: a single-centre randomised controlled trial

OBJECTIVES

Percutaneous coronary intervention (PCI) for acute coronary syndromes frequently fails to restore myocardial perfusion despite establishing epicardial vessel patency. Endothelin-1 (ET-1) is a potent vasoconstrictor, and its expression is increased in atherosclerosis and after PCI. In this study, we aim to define the role of endothelin in regulating coronary microvascular blood flow and myocardial perfusion following PCI in patients with non-ST elevation acute coronary syndromes (NSTACS), by assessing whether adjunctive therapy with a selective endothelin A (ETA) receptor antagonist acutely improves postprocedural coronary microvascular blood flow.

METHODS

In a randomised, double-blinded, placebo-controlled trial, 23 NSTACS patients were enrolled to receive an intracoronary infusion of placebo (n=11) or BQ-123 (n=12) immediately before PCI. Post-PCI coronary microvascular blood flow and myocardial perfusion were assessed by measuring Doppler-derived average peak velocity (APV), and cardiac biomarker levels were quantified.

RESULTS

Compared with the placebo group, APV was significantly higher in the drug group immediately after PCI (30 (20, 37) vs 19 (9, 26) cm/s; p=0.03). Hyperaemic APV, measured post-adenosine administration, was higher in the BQ-123 group, but the difference did not achieve statistical significance (56 (48, 72) vs 46 (34, 64) cm/s; p=0.090). Maximum coronary flow reserve postprocedure was not different between the two groups (2.1 (1.6, 2.3) vs 2.5 (1.8, 3.0)). Per cent change in creatine kinase isoenzyme MB from the time of PCI to 8 and 16 hours post-PCI was significantly lower in the drug group compared with the placebo group (-17 (-26, -10) vs 26 (-15, 134); p=0.02 and -17 (-38, 14) vs 107 (2, 446); p=0.007, respectively).

CONCLUSIONS

Endothelin is a mediator of microvascular dysfunction during PCI in NSTACS, and adjunctive selective ETA antagonist may augment myocardial perfusion during PCI.

TRIAL REGISTRATION NUMBER

NCT00586820; Results.

Effect of Levosimendan on Diastolic Function in Patients Undergoing Coronary Artery Bypass Grafting: A Comparative Study

PURPOSE

To compare the efficacy of levosimendan with nitroglycerin in patients with isolated diastolic dysfunction undergoing coronary artery bypass grafting.

PROCEDURE

Thirty patients with isolated diastolic dysfunction undergoing on-pump coronary artery bypass grafting were randomized into 2 groups receiving levosimendan or nitroglycerin infusion. The infusion was started before sternotomy and continued in the postoperative period. Perioperatively, diastolic function was serially evaluated at 3 different time points using echocardiography. N-terminal fragment of pro-B-natriuretic peptide (NT-proBNP) levels were measured in both the groups.

RESULTS

There was a significant improvement in diastolic function as measured by isovolumic relaxation time (P = 0.0001, P = 0.001) and deceleration time (P = 0.0001, P = 0.0001) in the levosimendan group from the baseline in patients with impaired relaxation. Similarly, tissue Doppler imaging also revealed an improvement from the baseline in patients with a pseudonormal pattern (P = 0.018, P = 0.001). Furthermore, there was a significant improvement in the above parameters when compared with the nitroglycerin group. The NT-proBNP levels also demonstrated a similar pattern between the 2 groups (P = 0.03, P = 0.02) when levosimendan was compared with nitroglycerin in patients with a pseudonormal pattern on echocardiography.

CONCLUSIONS

Levosimendan is superior to nitroglycerin in improving diastolic function irrespective of coronary revascularization.

Influence of isoflurane on the diastolic pressure-flow relationship and critical occlusion pressure during arterial CABG surgery: a randomized controlled trial

The effects of isoflurane on the determinants of blood flow during Coronary Artery Bypass Graft (CABG) surgery are not completely understood. This study characterized the influence of isoflurane on the diastolic Pressure-Flow (P-F) relationship and Critical Occlusion Pressure (COP) during CABG surgery. Twenty patients undergoing CABG surgery were studied. Patients were assigned to an isoflurane or control group. Hemodynamic and flow measurements during CABG surgery were performed twice (15 minutes after the discontinuation of extracorporeal circulation (T15) and again 15 minutes later (T30)). The zero flow pressure intercept (a measure of COP) was extrapolated from a linear regression analysis of the instantaneous diastolic P-F relationship. In the isoflurane group, the application of isoflurane significantly increased the slope of the diastolic P-F relationship by 215% indicating a mean reduction of Coronary Vascular Resistance (CVR) by 46%. Simultaneously, the Mean Diastolic Aortic Pressure (MDAP) decreased by 19% mainly due to a decrease in the systemic vascular resistance index by 21%. The COP, cardiac index, heart rate, Left Ventricular End-Diastolic Pressure (LVEDP) and Coronary Sinus Pressure (CSP) did not change significantly. In the control group, the parameters remained unchanged. In both groups, COP significantly exceeded the CSP and LVEDP at both time points. We conclude that short-term application of isoflurane at a sedative concentration markedly increases the slope of the instantaneous diastolic P-F relationship during CABG surgery implying a distinct decrease with CVR in patients undergoing CABG surgery.

Evaluation of Microvascular Disease and Clinical Outcomes

Although coronary microcirculatory dysfunction occurs in numerous cardiac conditions and influences prognosis, it has been largely ignored in clinical practice due to the lack of adequate methods for its assessment. Microcirculatory dysfuntion may result from a variety of causes, including structural remodelling (arterioles or capillaries), dysregulation (paradoxical arteriolar vasoconstriction), hypersensitivity to vasoactive factors or adrenergic drive, and extravascular compression of collapsable elements. Thus, the selection of a method to interrogate coronary microcirculation should be based on the suspected cause of dysfunction. This article reviews such assessment tools and their prognostic information.

Usefulness of Hyperemic Microvascular Resistance Index as a Predictor of Clinical Outcomes in Patients with ST-Segment Elevation Myocardial Infarction

BACKGROUND AND OBJECTIVES

Microvascular function is a useful predictor of left ventricular functional changes in patients with ST-segment elevation myocardial infarction (STEMI). We evaluated the usefulness of the hyperemic microvascular resistance index (hMVRI) for predicting long-term major adverse cardiovascular events (MACEs) in patients with STEMI assessed immediately after primary percutaneous coronary intervention (PCI).

SUBJECTS AND METHODS

hMVRI were evaluated in 145 patients with first acute STEMI treated with primary PCI using an intracoronary Doppler wire. hMVRI was defined as the ratio of mean aortic pressure over hyperemic averaged peak velocity of infarct-related artery. Major adverse cardiovascular events (MACEs) included cardiac death and re-hospitalization for congestive heart failure.

RESULTS

During the mean follow-up of 85±43 months, MACEs occurred in 17.2% of patients. Using a receiver-operating characteristics analysis, hMVRI >2.82 mm Hg·cm-1·sec (sensitivity: 87%; specificity: 69%; and area under curve: 0.818) was the best cut-off values for predicting future cardiac events. The Cox proportional hazard analysis showed that hMVRI was an independent predictor for long-term MACEs (hazard ratio 1.741, 95% confidence interval 1.348-2.264, p<0.001). The Kaplan-Meier survival analysis showed a higher incidence of MACEs in patients with hMVRI >2.82 mm Hg·cm-1·sec (p<0.001).

CONCLUSION

hMVRI was a strong predictor of long-term MACEs in patients with STEMI treated with primary PCI.

Primary PCI: time to change focus from epicardial reperfusion towards protection of the microvasculature

Myocardial tissue perfusion remains compromised in 30-40% of patients with ST-segment elevation myocardial infarction (STEMI) despite restored epicardial patency after primary percutaneous coronary intervention (pPCI). This phenomenon is attributed to microvascular dysfunction secondary to numerous pathophysiological mechanisms, including distal embolisation of plaque and thrombus material. Its association with larger post-infarction myocardial necrosis, impaired left ventricular recovery, and worse clinical outcome illustrates the pertinence of a comprehensive armamentarium for the diagnosis, protection and treatment of microvascular dysfunction in STEMI patients. Current strategies to protect the microvasculature during pPCI are based on the assumption that distal embolisation of thrombotic and atheromatous debris is the main mechanism precipitating impaired myocardial tissue perfusion. However, recent findings suggest that this assumption is only true for the border zone of the ischaemic myocardium, whereas the infarct core consists of intramyocardial haemorrhage secondary to microvascular destruction, rather than obstruction. This observation has pertinent implications for contemporary and future adjuvant treatment strategies in STEMI patients. In this review, we provide an overview of the currently available armamentarium to assess the microvasculature, review contemporary strategies in pPCI to protect the myocardium, and discuss novel insights into microvascular pathophysiology that may help guide our focus from the coronary arteries to the microvasculature.

Numerical modelling of the physical factors that affect mass transport in the vasculature at early time periods

Coronary artery disease results in blockages or narrowing of the artery lumen. Drug eluting stents were developed to replace bare metal stents in an effort to combat re-blocking of the lumen. A key element in determining the therapeutic success of a drug eluting stent is an in-depth understanding of the physical factors that affect mass transport of the drug into the arterial wall, over early time periods. The numerical models developed within this study focus on assessing the influence of a host of physical factors that either facilitate or impede therapeutic drug delivery into the arterial wall from the unit cell of an idealised stent. This study demonstrates that model reduction strategies to 2D and 1D can still adequately represent a 3D curved arterial wall and strut polymer coating, respectively, using an idealistic stent geometry. It was shown that the level of strut compression can have a significant impact on therapeutic drug delivery in the arterial wall.

[Usefulness of diastolic deceleration time assessed by transthoracic Doppler measurement in the detection of sustained microvascular obstruction in STEMI patients treated by primary PTCA]

AIMS

To assess the value of coronary flow measurement by transthoracic Doppler technique in the detection of "no-reflow" phenomenon.

METHODS

Fourteen patients with first anterior wall infarction treated by successful (TIMI3) primary percutaneous angioplasty and left descending coronary artery stenting were investigated. Myocardial perfusion following PCI was assessed by (i) ST-segment resolution, (ii) MRI-detected microvascular obstruction (early hypoenhancement), (iii) coronary flow pattern measurement by transthoracic Doppler technique.

RESULTS

Sustained impairment of myocardial perfusion following PCI was observed in a large proportion of the cohort (36% by MRI, 43% by ST regression analysis). Patients with a diastolic deceleration time inferior to 482 ms had higher troponin and CK peak value, higher wall motion index score, lower ST resolution and lower LVEF assessed by MRI. The concordance of the three methods was 80%.

CONCLUSION

The measurement of diastolic deceleration time by transthoracic Doppler technique is a reliable technique to identify microvascular obstruction following PCI in acute anterior STEMI. A DDT inferior to 482 ms is associated with sustained "no-reflow" phenomenon.

Microvascular obstruction: underlying pathophysiology and clinical diagnosis

Successful restoration of epicardial coronary artery patency after prolonged occlusion might result in microvascular obstruction (MVO) and is observed both experimentally as well as clinically. In reperfused myocardium, myocytes appear edematous and swollen from osmotic overload. Endothelial cell changes usually accompany the alterations seen in myocytes but lag behind myocardial cell injury. Endothelial cells become voluminous, with large intraluminal endothelial protrusions into the vascular lumen, and together with swollen surrounding myocytes occlude capillaries. The infiltration and activation of neutrophils and platelets and the deposition of fibrin also play an important role in reperfusion-induced microvascular damage and obstruction. In addition to these ischemia-reperfusion-related events, coronary microembolization of atherosclerotic debris after percutaneous coronary intervention is responsible for a substantial part of clinically observed MVO. Microvascular flow after reperfusion is spatially and temporally complex. Regions of hyperemia, impaired vasodilatory flow reserve and very low flow coexist and these perfusion patterns vary over time as a result of reperfusion injury. The MVO first appears centrally in the infarct core extending toward the epicardium over time. Accurate detection of MVO is crucial, because it is independently associated with adverse ventricular remodeling and patient prognosis. Several techniques (coronary angiography, myocardial contrast echocardiography, cardiovascular magnetic resonance imaging, electrocardiography) measuring slightly different biological and functional parameters are used clinically and experimentally. Currently there is no consensus as to how and when MVO should be evaluated after acute myocardial infarction.

Coronary reserve impairment prevents the improvement of left ventricular dysfunction and adversely affects the long-term outcome of patients with hypertensive dilated cardiomyopathy

In hypertension, left ventricular (LV) hypertrophy develops as an adaptive mechanism to compensate for increased afterload and thus preserve systolic function. Associated structural changes such as microvascular disease might potentially interfere with this mechanism, producing pathological hypertrophy. A poorer outcome is expected to occur when LV function is put in jeopardy by impaired coronary reserve. The aim of this study was to evaluate the role of coronary reserve in the long-term outcome of patients with hypertensive dilated cardiomyopathy. Between 1996 and 2000, 45 patients, 30 of them male, with 52+/-11 years and LV fractional shortening <30% were enrolled and followed until 2006. Coronary flow velocity reserve was assessed by transesophageal Doppler of the left anterior descending coronary artery. Sixteen patients showed >/=10% improvement in LV fractional shortening after 17+/-6 months. Coronary reserve was the only variable independently related to this improvement. Total mortality was 38% in 10 years. The Cox model identified coronary reserve (hazard ratio=0.814; 95% CI=0.72-0.92), LV mass, low diastolic blood pressure, and male gender as independent predictors of mortality. In hypertensive dilated cardiomyopathy, coronary reserve impairment adversely affects survival, possibly by interfering with the improvement of LV dysfunction.

Concordant improvements in coronary flow reserve and ST-segment resolution during percutaneous coronary intervention for acute myocardial infarction: a benefit of postconditioning

OBJECTIVE

To assess the effect of ischemic postconditioning on indices of coronary microvascular function during percutaneous coronary intervention (PCI) for acute ST segment elevation myocardial infarction (STEMI).

BACKGROUND

Myocardial tissue level perfusion remains suboptimal in many patients with STEMI despite restoration of antegrade flow in the epicardial coronary artery.

METHODS

Twenty-four patients with an evolving anterior STEMI were randomized to undergo a previously-validated ischemic postconditioning protocol or usual care during PCI. The extent of resolution of ST segment elevation along with Doppler-tip catheter velocimetry was used as indices of myocardial reperfusion and microvascular function, respectively.

RESULTS

Postconditioned patients exhibited a greater, and therefore more rapid, extent of ST segment resolution (postconditioning, 70% +/- 15%; control, 48% +/- 16%; P = 0.0002) by the end of the procedure. Postconditioned patients also exhibited a greater hyperemic coronary vasodilator response at the completion of the procedure (coronary flow velocity reserve, CFVR: postconditioning, 2.2 +/- 0.1; control, 1.5 +/- 0.1; P < 0.0001). The end-procedure CFVR was directly related to the extent of the ST segment resolution (r = 0.85) but inversely related to the absolute magnitude of ST segment elevation at end procedure (r = -0.76). Peak serum creatine kinase was significantly lower in postconditioned patients (postconditioning, 1,524 +/- 435 IU/l; control, 1,862 +/- 561 IU/l; P = 0.03).

CONCLUSIONS

Ischemic postconditioning, as described, can be expeditiously performed during PCI for STEMI. Concordant changes in coronary flow reserve and ST segment resolution, measures of microcirculatory function, and myocardial perfusion, were greater in postconditioned patients.

Intraoperative coronary artery pulse Doppler patterns in patients with complete transposition of the great arteries undergoing the arterial switch operation

BACKGROUND

Arterial switch operation is standard repair for complete transposition of the great arteries (TGA). Coronary artery abnormalities are the most common cause of morbidity and mortality in the acute postoperative phase. This study was designed to determine whether coronary artery pulse Doppler flow patterns obtained by transesophageal echocardiography during the arterial switch operation are correlated with acute postoperative outcomes.

METHODS

A retrospective review of all patients with TGA undergoing the arterial switch operation between 2004 and 2006 was performed. Intraoperative coronary artery pulse Doppler flow patterns were analyzed by 2 blinded investigators. Associations of coronary artery pulse Doppler flow patterns with clinical outcomes were sought using multivariable linear and logistic regression analysis.

RESULTS

Sixty-three patients (48 male, gestational age 38 +/- 2 weeks, birth weight 3,514 +/- 613 g) were analyzed. Three patients needed mechanical support (2 died), 19 had delayed sternal closure, 17 had arrhythmias, and 9 had ST changes. The most common coronary artery pulse Doppler flow pattern consisted of a late systolic peak followed by low-velocity flow throughout diastole. A left main coronary artery (LMCA) velocity time integral >0.14 (P = .01) and an LMCA peak systolic velocity >0.6 cm/s (P = .05) were associated with need for surgical revision.

CONCLUSION

Abnormalities in LMCA flow were associated with the need for surgical revision in patients with TGA undergoing the arterial switch operation. Normal coronary artery pulse Doppler flow patterns after the arterial switch operation consisted of a late systolic peak followed by low-velocity flow throughout diastole.

Comparison of accuracy in the prediction of left ventricular wall motion changes between invasively assessed microvascular integrity indexes and fluorine-18 fluorodeoxyglucose positron emission tomography in patients with ST-elevation myocardial infarction

We compared the accuracy in predicting regional wall motion score index (RWMSI) changes between microvascular integrity indexes measured during primary percutaneous coronary intervention (PCI) and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in ST-elevation myocardial infarction (STEMI). Fifty patients with STEMI were enrolled. Microvascular integrity indexes were measured using an intracoronary Doppler wire and a pressure wire after primary PCI. We performed FDG-PET 7 days after PCI. RWMSI on follow-up echocardiogram (5.8 +/- 1.7 months) revealed good correlations with coronary flow reserve (r = -0.442, p = 0.002), diastolic deceleration time (r = -0.511, p <0.001), microvascular resistance index (r = 0.443, p = 0.002), coronary wedge pressure (r = 0.474, p <0.001), and FDG uptake rate (r = -0.571, p <0.001). There were no significant differences in areas under the curve for predicting RWMSI changes between microvascular integrity indexes and FDG-PET (coronary flow reserve 0.696, diastolic deceleration time 0.731, microvascular resistance index 0.748, coronary wedge pressure 0.694, Thrombolysis In Myocardial Infarction myocardial perfusion grade 0.702, and FDG-PET 0.755). In conclusion, microvascular integrity indexes assessed during primary PCI are useful and comparable to FDG-PET in predicting left ventricular functional changes in STEMI.

Relation between the assessment of microvascular injury by cardiovascular magnetic resonance and coronary Doppler flow velocity measurements in patients with acute anterior wall myocardial infarction

OBJECTIVES

We studied the relation between presence and severity of microvascular obstruction (MO), measured by cardiovascular magnetic resonance (CMR) and intracoronary Doppler flow measurements, for assessment of myocardial reperfusion in patients with acute anterior myocardial infarction (MI) treated by primary percutaneous coronary intervention (PCI).

BACKGROUND

Cardiovascular magnetic resonance has been used to detect and quantify MO in patients after acute MI but has never been compared with coronary blood flow velocity patterns.

METHODS

Twenty-seven patients with first anterior ST-segment elevation MI successfully treated with primary PCI were included. Coronary blood flow velocity was measured during recatheterization 4 to 8 days after primary PCI. These measurements were related to MO determined by late gadolinium-enhanced (LGE) CMR performed the day before recatheterization.

RESULTS

Early systolic retrograde flow was observed in 0 of 8 patients without MO on LGE CMR and in 10 (53%) of 19 patients with MO (p = 0.01). The extent of MO correlated with the diastolic-systolic velocity ratio (r = 0.44; p = 0.02), diastolic deceleration time (r = -0.61; p = 0.001), diastolic deceleration rate (r = 0.75; p < 0.0001), and coronary flow velocity reserve of the infarct-related artery (r = -0.44; p = 0.02). Furthermore, multivariate regression analyses, including extent of MO, infarct size, and transmural necrosis on LGE CMR, revealed that extent of MO was the only independent factor related to early systolic retrograde flow and diastolic deceleration rate.

CONCLUSIONS

Assessment of microvascular injury by LGE CMR corresponds well to evaluation by intracoronary Doppler flow measurements. By means of CMR, quantification of myocardial function, infarct size, and microvascular injury can accurately be performed with a single noninvasive technique in patients with acute MI.

Effects of levosimendan on coronary artery flow and cardiac performance in patients with advanced heart failure

BACKGROUND

Levosimendan has inotropic and vasodilatory effects. We investigated the effects of levosimendan on coronary flow and associated changes in neurohormonal activation and cardiac performance in patients with advanced heart failure.

METHODS

Forty-two patients with NYHA III-IV and a left ventricular ejection fraction (EF) 25+/-6%, were randomised to levosimendan 0.1 microg/kg/min (n=21) or placebo for 24 h. Before and 24 h after each treatment, we assessed: the maximal velocity (Vmax), time integral (VTI) and deceleration time (DT) of the diastolic coronary flow wave (CF) in LAD using transthoracic Doppler echocardiography, pulmonary artery systolic pressure by Doppler echocardiography, E/E' ratio using Doppler imaging of mitral inflow velocity, tissue Doppler imaging of the mitral annulus and B-type natriuretic peptide (BNP) levels.

RESULTS

By ANOVA, there was a greater increase in CF-Vmax (43+/-23 vs.25+/-8 cm/s), CF-DT (904+/-250 vs. 667+/-151 ms), and EF and a greater decrease in BNP, pulmonary artery systolic pressure and E/E? after levosimendan than after placebo (p<0.05). Compared to baseline, the percent changes in CF-VTI were related to the concomitant changes in EF, E/E?, and BNP after treatment with levosimendan (r=0.69, r=?0.51 and r=?0.80, p<0.05 respectively).

CONCLUSION

Treatment with levosimendan improves coronary flow and microcirculation in parallel with an improvement in cardiac performance and neurohormonal activation in patients with advanced heart failure.

Usefulness of coronary flow reserve immediately after primary coronary angioplasty for acute myocardial infarction in predicting long-term adverse cardiac events

Coronary flow reserve (CFR) evaluated immediately after reperfusion is thought to reflect the degree of microvascular injury and predict left ventricular (LV) functional recovery after acute myocardial infarction. It was hypothesized that CFR immediately after reperfusion would be predictive of the occurrence of long-term adverse cardiac events. Using a Doppler guidewire, CFR was evaluated immediately after primary coronary angioplasty in 118 consecutive patients with first anterior acute myocardial infarctions. Adverse cardiac events combining cardiac death, recurrent myocardial infarction, and congestive heart failure were recorded during an average follow-up period of 62 +/- 32 months. Using receiver-operating characteristic analysis, CFR </=1.3 was the best predictor of future cardiac events (sensitivity 86%, specificity 70%). Accordingly, patients were divided into 2 groups: those with CFR </=1.3 (n = 50) and those with CFR >1.3 (n = 68). Patients with CFR </=1.3 had significantly higher peak creatine kinase concentrations, lower LV ejection fractions, and higher LV volumes compared with patients with CFR >1.3. CFR was significantly correlated with the LV ejection fraction at 4 weeks (r = 0.50, p <0.0001) and LV end-diastolic volume at 4 weeks (r = -0.43, p <0.0001). Kaplan-Meier survival analysis showed a higher incidence of adverse cardiac events in patients with CFR </=1.3 (p <0.0001). In conclusion, CFR evaluated immediately after primary coronary angioplasty is a strong predictor of long-term adverse cardiac events after reperfused acute myocardial infarction.

Effects of Diffusion Coefficients and Struts Apposition Using Numerical Simulations for Drug Eluting Coronary Stents

In the context of drug eluting stent, we present two-dimensional numerical models of mass transport of the drug in the wall and in the lumen to study the effect of the drug diffusion coefficients in the three principal media (blood, vascular wall, and polymer coating treated as a three-compartment problem) and the impact of different strut apposition configurations (fully embedded, half embedded, and not embedded). The different conditions were analyzed in terms of their consequence on the drug concentration distribution in the arterial wall. We apply the concept of the therapeutic window to the targeted vascular wall region and derive simple metrics to assess the efficiency of the various stent configurations. Although most of the drug is dispersed in the lumen, variations in the blood flow rate within the physiological range of coronary blood flow and the diffusivity of the drug molecule in the blood were shown to have a negligible effect on the amount of drug in the wall. Our results reveal that the amount of drug cumulated in the wall depends essentially on the relative values of the diffusion coefficients in the polymer coating and in the wall. Concerning the strut apposition, it is shown that the fully embedded strut configuration would provide a better concentration distribution.

Coronary flow velocity pattern assessed by transthoracic Doppler echocardiography predicts adverse clinical events and myocardial recovery after successful primary angioplasty

BACKGROUND

Doppler guidewire studies demonstrated that specific velocity patterns in the left anterior descending coronary artery (LAD) after primary percutaneous coronary intervention (PCI) predict myocardial recovery and clinical outcome. The present study assessed whether similar results can be achieved by transthoracic Doppler echocardiography (TTDE).

METHODS

Coronary flow velocities of LAD were evaluated by TTDE in 35 consecutive patients with anterior acute myocardial infarction who were treated with successful primary PCI plus stenting, performed within 6 h after the onset of symptoms or within 6-12 h if there was evidence of continuing ischaemia. Coronary-flow velocity of the LAD was achieved after 12 h and within 48 h after the PCI; TTDE standard examination was repeated after 2 months of follow-up.

RESULTS

Three patterns were found: (i) 'pattern A' with good antegrade systolic flow and slow diastolic deceleration rate (63.7%); (ii) 'pattern B' with reduced or absent systolic flow and rapid diastolic deceleration rate (9.1%); and (iii) 'pattern C' with protosystolic retrograde flow and rapid diastolic deceleration rate (27.2%). The clinical characteristics and echocardiographic data were compared: wall-motion-score-index (WMSI), ejection fraction, end-diastolic volume (EDV) after PCI (T1) and after 2 months (T2). Patients with pattern A demonstrated recovery of contractile function (WMSI-T1 1.48 + or - 0.42/WMSI-T2 1.29 + or - 0.29, P < 0.05) and better clinical outcome; patients with patterns B and C ran into ventricular remodelling (EDV-T1 89 + or - 6.3 ml/EDV-T2 123 + or - 25 ml, P = 0.002) and more early and late complications.

CONCLUSIONS

TTDE is a reliable method to achieve coronary flow velocities in LAD after an anterior acute myocardial infarction and it could be useful to evaluate no-reflow phenomenon at bedside and thus clinical outcome.

Coronary flow velocity pattern and coronary flow reserve by contrast-enhanced transthoracic echocardiography predict long-term outcome in heart transplantation

BACKGROUND

We assessed coronary flow velocity pattern and coronary flow reserve (CFR) by contrast-enhanced transthoracic echocardiography (CE-TTE) as markers of major adverse cardiac events (MACE) related to cardiac allograft vasculopathy (CAV) after heart transplantation (HT).

METHODS AND RESULTS

Deceleration time of diastolic flow velocity (DDT) and CFR were measured in the left anterior descending coronary artery (LAD) by CE-TTE in 66 consecutive HT patients (follow-up 19+/-5 months). CFR was calculated as the ratio of hyperemic to basal diastolic flow velocity. Angiographies were analyzed by a qualitative grading system; CAV was defined as changes grade II or higher. MACE were cardiac death, stent implantation, and heart failure. Patients with MACE had higher CAV incidence (P=0.004) and grade (P=0.008), shorter DDT (P=0.006), and lower CFR (P=0.008). A receiver-operating characteristic-derived DDT cutpoint < or = 840 ms (area under the curve 0.793; P=0.01) was 75% specific and 86% sensitive for predicting MACE, with positive predictive value (PPV) and negative predictive value (NPV) of 33% and 97%, respectively (P=0.002). A CFR cutpoint of < or =2.6 (area under the curve 0.746; P=0.01) was 62% specific and 91% sensitive for predicting MACE (PPV =32%, NPV =97%) (P=0.001). Patients with CFR < or = 2.6 and patients with DDT < or = 840 ms had a lower survival free from MACE (P=0.006 and P=0.009, respectively). By Cox regression, only a lower CFR predicted the risk of MACE (relative risk 3.1; 95% CI, 1.26 to 7.9; P=0.01).

CONCLUSIONS

In HT patients, shorter DDT and lower CFR by CE-TTE are reliable markers for CAV-related MACE. CFR is the main independent predictor of MACE.

Microvascular obstruction after successful fibrinolytic therapy in acute myocardial infarction. Comparison of reteplase vs reteplase+abciximab: A cardiovascular magnetic resonance study

BACKGROUND.: About one third of patients with TIMI 3 after reperfusion have evidence of microvascular obstruction (MO) which represents an independent predictor of myocardial wall rupture. This explains all efforts made to prevent MO. Magnetic resonance imaging (MRI) has proved to be particularly useful in detecting MO. The aim of this study was to evaluate with MRI if different fibrinolytic regimens in acute myocardial infarction display different effects on left ventricle (LV) volumes and ejection fraction (EF), as well as on myocardial infarct size (MIsz) and MO. METHODS.: Twenty male patients, mean age 58 years, affected by acute myocardial infarction, ten anterior and ten inferior, were treated with: full dose reteplase in ten, and half dose reteplase plus full dose abciximab (R+Abcx) in the other ten patients. In the fourth day after hospital admission, MRI STIR T2 images were used to quantify MIsz, while 2dflash cineloops were used after the injection of gadolinium, to quantify LV volumes, EF and to detect MO. RESULTS.: LV EF was higher in R+Abcx 51±10 than in reteplase 41±8. MIsz was similar in both treatment groups: however a close relationship was present between MIsz and EF in the reteplase group indicating that the greater the MIsz the lower the EF. In R+Abcx this relationship was no longer present, suggesting a protective effect of the drug on microcirculation. In fact extensive MO was present in 25% of all cases, 80% of which in the reteplase group while only 20% in R+Abcx. CONCLUSION.: R+Abcx prevents MO: compared to traditional fibrinolytic therapy it allows better LV function and most likely improved long term survival.

Instantaneous diastolic pressure–flow relationship in arterial coronary bypass grafts

OBJECTIVE

The objective of this study was to describe the diastolic pressure-flow relationship and to assess critical occlusion pressure in arterial coronary bypass grafts in human beings.

METHODS AND RESULTS

Fifteen patients were studied following elective surgical coronary artery bypass grafting. Flow in the left internal mammary artery bypass to the left anterior descending artery was measured and simultaneously, aortic pressure, coronary sinus pressure and left ventricular end-diastolic pressure were recorded. The zero-flow pressure intercept as a measure of critical occlusion pressure was extrapolated from the linear regression analysis of the instantaneous diastolic pressure-flow relationship. Mean diastolic flow was 46 +/- 17 mL min(-1), mean diastolic aortic pressure was 60.5 +/- 10.0 mmHg. Diastolic blood flow was linearly related to the respective aortic pressure in all patients (R-values 0.7-0.99). The regression lines had a mean slope of 2.1 +/- 1.2 mL min(-1) mmHg(-1). Mean critical occlusion pressure was 32.3 +/- 9.9 mmHg and exceeded mean coronary sinus pressure and mean left ventricular end-diastolic pressure by factors of 3.1 and 2.6, respectively.

CONCLUSIONS

Our data demonstrate the presence of a vascular waterfall phenomenon in the coronary circulation after internal mammary artery bypass grafting. Critical occlusion pressure in arterial grafts considerably exceeds coronary sinus pressure as well as left ventricular end-diastolic pressure and should thus be used as the effective downstream pressure when calculating coronary perfusion pressure. Our data further suggest that the slope of diastolic pressure-flow relationships provides a more rational approach to assess regional coronary vascular resistance than conventional calculations of coronary vascular resistance.