Large Epicardial Coronary Arteries Research Articles

Prognostic Implications of Coronary Artery Sclerosis in Troponin-Positive Patients with Non-Obstructive Coronary Arteries.

Coronary sclerosis is a risk factor for the progression to obstructive coronary artery disease (CAD). However, understanding its impact on the outcomes of patients with myocardial infarction and non-obstructive coronary arteries is limited. This study aimed to explore the prognostic influence of coronary sclerosis on in- and out-of-hospital events in troponin-positive patients with non-obstructive coronary arteries. This study was a retrospective cohort analysis based on prospectively collected data. A total of 24,775 patients who underwent coronary angiography from 2010 to 2021 in a German university hospital were screened, resulting in a final study cohort of 373 troponin-positive patients with non-obstructive coronary arteries and a follow-up period of 6.2 ± 3.1years. Coronary sclerosis was defined as coronary plaques without angiographically detectable stenotic lesions of 50% or more in the large epicardial coronary arteries. The primary study endpoint was the occurrence of in-hospital events. Secondary endpoints included events during follow-up. Patients with coronary sclerosis were significantly older (70 ± 12 vs. 58 ± 16years, p < 0.001), had ST-segment elevation less frequently on electrocardiogram (9.4% vs. 18.7%, p = 0.013), and suffered more often from diabetes mellitus (23.3% vs. 13.1%, p = 0.009), arterial hypertension (79.6% vs. 59.8%, p < 0.001), chronic obstructive pulmonary disease (17.1% vs. 9.4%, p = 0.028), chronic kidney disease (22.2% vs. 8.4%, p < 0.001), atrial fibrillation (19.8% vs. 12.2%, p = 0.045), and valvular diseases than patients without CAD. Patients with coronary sclerosis were more likely to receive medication for primary/secondary prevention on admission and at discharge. The incidence of in- and out-of-hospital events was significantly higher in patients with coronary sclerosis (in-hospital: 42.8% vs. 29.9%, p = 0.010; out-of-hospital: 46.0% vs. 26.1%, p < 0.001). Mortality rates tended to be higher in the coronary sclerosis group (29.4% vs. 20.0%, p = 0.066). Patients diagnosed with coronary sclerosis presented a higher incidence of comorbidities and increased medication use, and experienced higher rates of both in-hospital and out-of-hospital events, primarily due to the clustering of cardiovascular risk factors.

Comparison of a coronary bypass surgery using a combination of both on-pump beating heart and cardioplegic arrest with conventional coronary bypass surgery using cardioplegic arrest on-pump.

Antegrade cardioplegia may cause maldistribution in patients with multivessel coronary artery disease. Surgically bypassing large epicardial vessels before the cross-clamp and then administering cardioplegia from both the aortic root and the anastomosed grafts significantly prevent maldistribution and provide better cardiac protection. This study included 80 patients, all older than 70years with an ejection fraction between 25 and 35%. Patients were equally divided into two groups. Distal anastomoses to some of large epicardial coronary arteries were performed before the cross-clamp was placed. Grafted veins were attached to multi-perfusion set ports. Then, cross-clamping was performed, and the multi-perfusion set was disconnected from the aortic cannula and attached to the cardioplegia route. Antegrade cardioplegia was administered to both the aortic root and saphenous vein grafts. After all distal anastomoses were completed, the cross-clamp was removed, and the multi-perfusion set was connected to the aortic cannula again. Conventional coronary bypass techniques were used in group 2 patients. Inotropic agents were administered in 12 patients in group 1 and 29 patients in group 2 (p < 0.001). The average troponin I value in coronary sinus blood was 1.05 ± 0.8ng/mL in group 1 and 3.12 ± 0.7ng/mL in group 2 (p < 0.001). The average lactate value in coronary sinus blood was 1.15 ± 0.55mmol/L in group 1 and 3.7 ± 2.4mmol/L in group 2 (p < 0.001). Six patients died in the early postoperative period in group 2 (p = 0.028). The current technique considerably reduces cross-clamping time and allows better distribution of the cardioplegic solution, preserving myocardium. Reduced coronary sinus lactate and troponin I levels also indicate better myocardial protection.

Linear epicardial cryoablation effects in a porcine model: Lesion characteristics and vascular risk.

Cryoablation in open-chest surgical interventions for ventricular arrhythmias has been reported with reasonable procedural outcomes. However, the characteristics of cryoablation lesions on the ventricular myocardium are not well defined. The purpose of the present study was to determine the tissue and vascular effects of a linear epicardial cryoablation probe in a porcine animal model. Five adult Yorkshire swine underwent median sternotomy and application of linear cryoablation lesions using a malleable aluminum linear cryoablation probe of varying duration (2, 3, 4, and 5 min), including one lesion placed intentionally over the left anterior descending coronary (LAD) artery. Histological analysis was performed. Maximum lesion depth was approximately 1.0 cm with 3 min freezes, with no significant increase in depth achieved with longer lesions. No transmural lesions were achieved. No large vessel epicardial coronary artery injuries were seen to the LAD; however, surprisingly, remote isolated interventricular septal injury was seen in all animals, suggestive of possible compromise of smaller coronary arterial vessels. Single application freezes with an aluminum linear cryoablation probe can create homogeneous ablative lesions over the ventricular myocardium with a maximum depth of approximately 1.0 cm. No large vessel injury occurred with direct lesion application of the LAD; however, small coronary vessels may be at risk.

Cardiac microcirculation assessment of diabetic patients according to the presence of peripheral microangiopathy, by MRI myocardial perfusion

Coronary flow reserve (CFR), ratio of maximal myocardial blood flow (MBF) during pharmacologically induced coronary vasodilation to resting MBF, is an integrated measure of flow through both the large epicardial coronary arteries and the microcirculation. CFR has been proposed as an indirect parameter to evaluate the function of the coronary microcirculation, and its impairment is a strong predictor of cardiovascular mortality. Rubidium PET-computed tomography scanner, the gold standard method to evaluate CFR is not available in France. We aimed to assess cardiac microcirculation using MRI myocardial perfusion in diabetic patients. Using semi-quantitative analysis by MRI, we estimated CFR by the Myocardial Perfusion Reserve Index (MPRI), ratio between perfusion signal (maximal upslope) with adenosine stress and rest of myocardial segments in 27 diabetic patients without coronary artery disease perfectly phenotype for microangiopathy (eye, kidney, nerve). MPRI was analyzed according to the presence of extra cardiac microangiopathy. This technique is feasible with routine MRI protocols. Reproducibility was very good: 99 myocardial segments analyzed by 2 independent observers: MPRI 2.2 ± 0.76 vs. 2.24 ± 0.8; mean of differences: − 0.033 IC95% [−0.13; 0.07]. MPRI was lower in the group of diabetic patients with extra-cardiac microangiopathy ( n = 11) as compared to the group without ( n = 16): 2.01 ± 0.78 vs. 2.31 ± 0.7, P = 0.51, not statistically significant because of the modest number of patients. CFR was significantly altered in myocardial segments analyzed in diabetics with microangiopathy ( n = 150) as compared to myocardial segments from diabetics without microangiopathy ( n = 192): 1,99 ± 0.83 vs. 2.35 ± 0.98 P < 0.002. Semi quantitative analysis of CFR is feasible in a daily routine after stress MRI. Preliminary result in diabetic patients suggests a strong link between microangiopathy and a decrease in CFR.

Exercise and pharmacologic stress-induced interlead T-wave heterogeneity analysis to detect clinically significant coronary artery stenosis

BackgroundDespite widespread use of ETT and vasodilator-stress with myocardial perfusion imaging (MPI) for noninvasive detection of flow-limiting coronary artery disease, there is continued need to improve diagnostic accuracy. We examined whether measurement of interlead T-wave heterogeneity (TWH) during exercise tolerance testing (ETT) or pharmacologic stress testing improves detection of stenoses in large epicardial coronary arteries. MethodsAll 137 patients at our institution who underwent diagnostic coronary angiography within 0 to 5 days after ETT (N = 81) or dipyridamole IV infusion (N = 58) in 2016 were studied, including 2 patients with both tests. Cases (N = 93) had angiographically significant stenosis (≥50% of left main or ≥ 70% of an epicardial coronary artery ≥2 mm in diameter); controls (N = 44) did not. TWH, i.e., interlead splay of T waves, was determined by second central moment analysis from precordial leads by an investigator blinded to angiographic results. ResultsAt rest, TWH levels were similar for cases and controls. ETT and dipyridamole stress testing increased TWH by 69% (p < 0.0001) and 27% (p < 0.0001), respectively, in cases. In controls, TWH did not change. Areas under the ROC curves for TWH increase for any flow-limiting coronary artery stenosis were 0.737 (p < 0.0001) for ETT and 0.818 (p < 0.0001) for dipyridamole stress testing. By contrast, neither ST-segment changes during ETT (p = 0.12) nor MPI during dipyridamole stress testing (p = 0.60) discriminated cases from controls. ConclusionsTWH measurement is a novel method that improves detection of angiographically confirmed flow-limiting stenoses in large epicardial coronary arteries during both ETT and MPI during pharmacologic stress testing with dipyridamole.

Usefulness of coronary flow reserve measured by transthoracic coronary Doppler ultrasound in the elderly.

The left anterior descending (LAD) coronary artery is the main vessel of human coronary circulation, and life-threatening consequences are seen when flow in this area is impaired.[1] Noninvasive measurement of coronary flow reserve (CFR), defined as the ratio of maximal to baseline coronary blood flow, has been repeatedly shown to be a feasible technique by ultrasound transthoracic Doppler (TTD) both in the LAD and, with some limitations, in the posterior descending (PD) coronary artery.[2]–[7] CFR by TTD offers two important pieces of information: information about patency and flow through the large epicardial coronary artery proximal to the site of CFR assessment and information about the functional integrity of coronary microcirculation distal to the site of CFR assessment.[4] CFR by TTD is a valuable research tool for investigating the pathophysiology of coronary circulation. However, CFR by TTD is also an important clinical decision-making instrument, enabling functional assessment of epicardial coronary stenosis, particularly in cases of anatomically borderline stenosis, i.e., 50%–70% of cases.[8] CFR by TTD enables insight downstream into coronary microvascular function that might be impaired due to primary coronary microvascular disease, as a consequence of myocardial diseases with extramural compression and microvascular remodeling and rarefaction (in left ventricular hypertrophy, dilated or hypertrophic cardiomyopathy, or aortic stenosis), or as a consequence of microvascular obstruction due to micro-embolization by plaque and thrombus debris during percutaneous coronary interventions.[9] Epicardial coronary artery patency and flow may be particularly jeopardized in the elderly as a result of advanced atherosclerosis (a disease of aging). Coronary microcirculatory function might also be impaired in the elderly even in the absence of obstructive epicardial atherosclerosis due to accumulated risk factors (e.g., hypertension, diabetes, obesity) and co-morbidities (e.g., chronic kidney, aortic stenosis).[10],[11] As a technique that is noninvasive, inexpensive, easily repeatable, and that does not require radiation, TTD CFR may be very useful in the fragile population of the elderly, offering a better understanding of coronary vascular aging as well as clinically important information regarding the diagnosis and prognosis of coronary artery disease.

Current perspectives in coronary microvascular dysfunction.

The coronary arterial system consists of large epicardial coronary arteries, pre-arterioles, and arterioles, which together closely regulate CBF. Structural, functional, and extravascular abnormalities of the microcirculation lead to CMD. CMD can present with symptoms suggestive of CAD, often in the absence of significant obstructive epicardial CAD. Conventional invasive angiography does not allow direct visualization of the microcirculation. Invasive indices, such as CBF and CFR, and non-invasive imaging modalities, such as CMR and PET, can be used to quantify absolute MBF and enable a direct and accurate assessment of coronary microvascular function. CMD appears to be more prevalent in women, typically presenting with symptoms of ischemia with unobstructed coronary arteries, and has a relatively unfavorable prognosis. CMD is classified clinically depending on the presence or absence of epicardial CAD, myocardial disease, or iatrogenic causes. Although invasive intracoronary techniques can be used to detect CMD, these cannot provide insight into the mechanisms involved in its pathogenesis. Imaging modalities such as CMR and cardiac PET are becoming indispensable tools in the evaluation of suspected CMD.

Letter by Mohri Regarding Article, “Clinical Usefulness, Angiographic Characteristics, and Safety Evaluation of Intracoronary Acetylcholine Provocation Testing Among 921 Consecutive White Patients With Unobstructed Coronary Arteries”

Angina caused by spasm of the large epicardial coronary artery has been extensively investigated for >50 years, and its risk factors, diagnostic procedures, treatments, and prognosis are well established. In 1998, we proposed coronary microvascular spasm as a possible pathogenic mechanism of myocardial ischemia in Japanese patients with chest pain and normal epicardial coronary arteries (microvascular angina),1 which was later confirmed by others.2 In the cardiac catheterization laboratory, the occurrence of coronary microvascular spasm is suspected when patient’s symptoms are reproduced in association with ischemic electrocardiographic changes after intracoronary injection of acetylcholine or ergonovine without large epicardial artery hyperconstriction/spasm. Coronary …

Cardiac manifestations in systemic sclerosis.

Primary cardiac involvement, which develops as a direct consequence of systemic sclerosis (SSc), may manifest as myocardial damage, fibrosis of the conduction system, pericardial and, less frequently, as valvular disease. In addition, cardiac complications in SSc may develop as a secondary phenomenon due to pulmonary arterial hypertension and kidney pathology. The prevalence of primary cardiac involvement in SSc is variable and difficult to determine because of the diversity of cardiac manifestations, the presence of subclinical periods, the type of diagnostic tools applied, and the diversity of patient populations. When clinically manifested, cardiac involvement is thought to be an important prognostic factor. Profound microvascular disease is a pathognomonic feature of SSc, as both vasospasm and structural alterations are present. Such alterations are thought to predict macrovascular atherosclerosis over time. There are contradictory reports regarding the prevalence of atherosclerosis in SSc. According to some authors, the prevalence of atherosclerosis of the large epicardial coronary arteries is similar to that of the general population, in contrast with other rheumatic diseases such as rheumatoid arthritis and systemic lupus erythematosus. However, the level of inflammation in SSc is inferior. Thus, the atherosclerotic process may not be as aggressive and not easily detectable in smaller studies. Echocardiography (especially tissue Doppler imaging), single-photon emission computed tomography, magnetic resonance imaging and cardiac computed tomography are sensitive techniques for earlier detection of both structural and functional scleroderma-related cardiac pathologies. Screening for subclinical cardiac involvement via modern, sensitive tools provides an opportunity for early diagnosis and treatment, which is of crucial importance for a positive outcome.

Role of adenosine as an adjunct therapy in the prevention and treatment of no-reflow phenomenon in acute myocardial infarction with ST segment elevation: review of the current data

Copyright © Polskie Towarzystwo Kardiologiczne INTRODUCTION Numerous clinical studies have indicated the beneficial effects of timely, optimal (without residual stenosis) and sustained patency of an occluded epicardial artery on infarct size reduction, left ventricular (LV) function and clinical outcomes. While these observations validate the experimental findings of time-dependent myocardial salvage, patients with large regions of ischaemia continue to exhibit significant morbidity and mortality. So it is clear that additional strategies are needed to improve outcomes. Emerging evidence suggests that maximising myocardial salvage not only involves restoring the full patency of large epicardial coronary arteries, but also maintains blood flow in microcirculation of the reperfused bed [1]. Experimental models convincingly document the concept of progressive microcirculatory failure (the ‘no-reflow phenomenon’) and no-reflow appears to be an important component of the potential deleterious effect of reperfusion — myocardial reperfusion injury. In animal models, abnormalities of tissue perfusion are associated with an increase of the infarct size, and agents that preserve microvascular flow result in a significant reduction of irreversible myocyte necrosis. Diagnostic techniques to measure tissue perfusion have validated this concept in humans and it is now clear that abnormal tissue perfusion occurs frequently in patients with acute coronary syndromes (ACS) undergoing reperfusion therapy [1–6].

Allergic myocardial infarction

Allergic myocardial infarction

Why Quantify Myocardial Perfusion?

Myocardial blood flow (MBF) and coronary flow reserve (CFR), the ratio of MBF during hyperemia to basal MBF, are integrated measures of flow through both the large epicardial coronary arteries and the microcirculation. To date, positron emission tomography (PET) offers the most robust and best investigated method for quantifying MBF in vivo. The potential of MBF quantification to improve detection of patients with high-risk coronary artery disease (CAD) or to identify patients with variable degrees of microvascular or endothelial dysfunction are promising new clinical avenues which await further evaluation in larger prospective trials. The current experience with MBF quantification also demonstrates potential benefits in other groups of patients. The present article summarizes the published literature on MBF quantification in CAD and other cardiac conditions and outlines in which fields MBF quantification could offer important value to improve the treatment and prognosis of patients. Novel PET perfusion compounds that are not bound to an onsite cyclotron will improve availability of MBF quantification, promote its use in the clinical setting, and facilitate further studies to establish its clinical value.

Relaxant effect of trans-resveratrol on isolated porcine coronary arteries.

Recent studies provided evidence that trans-resveratrol (3,4',5-trihydroxystilbene, found in high concentrations in some red wines, may possibly decrease the risk of coronary heart disease mortality. The aim of this study, performed with large epicardial porcine coronary arteries (PCA) strips, was to investigate the relaxant effect of trans-resveratrol on these main conductance vessels, which have been described to be pathologically prone for vasospastic contractions. The data show that the tonic component of the biphasic contractions induced by histamine, as well as the contractions induced by F- ions (10 mmol/l), which activate G proteins downstream of the receptors, could dose-dependently be inhibited by trans-resveratrol (0.1-100 mumol/l). The EC50 values of the dose-response curves established for the inhibition of the sustained component of histamine-induced contractions were very similar to those obtained for the relaxations of fluoride-induced contractions: 0.45 +/- 0.08 and 0.29 +/- 0.05 mumol/l, resp. (n = 6). Ouabain (10 mumol/l)-induced contractions and rhythmic contractions elicited by tetraethylammonium (12 mmol/l) were also strongly inhibited by trans-resveratrol (20 mumol/l). It may be inferred from the results obtained in this study, that the relaxation of the coronary conductance vessels induced by trans-resveratrol is possibly based on a nongenomic interaction with steroid-like receptors located on the cell membrane.

The coronary circulation and blood flow in left ventricular hypertrophy

Two distinct types of left ventricular hypertrophy (LVH) have been described: the so called "physiologic" hypertrophy, which is normally found in professional athletes, and "pathologic" LVH which is found in patients with inherited heart muscle disease such as hypertrophic cardiomyopathy (HCM) or patients with cardiac and systemic diseases characterized by pressure or volume overload. Patients with pathologic LVH have often symptoms and signs suggestive of myocardial ischemia despite normal coronary angiograms. Under these circumstances ischemia is due to coronary microvascular dysfunction (CMD). The abnormalities of the coronary microcirculation may be unrelated to the degree of LVH and cause a reduction in maximum myocardial blood flow which, in the absence of epicardial stenoses, is suggestive of CMD. There is no technique that enables direct visualization of coronary microcirculation in vivo in humans. Therefore, its assessment relies on the measurement of parameters which reflect its functional status, such as myocardial blood flow and coronary flow reserve which is an integrated measure of flow through both the large epicardial coronary arteries and the microcirculation. In this review article we discuss the pathophysiological mechanisms responsible for CMD in patients with primary and secondary LVH and how the recognition of this phenomenon is providing new important information on patient stratification and prognosis. Finally, we discuss how assessment of CMD may be used as a valuable surrogate marker to test the efficacy of old and new drugs. This article is part of a Special Issue entitled "Coronary Blood Flow".

No-Reflow Phenomenon: Maintaining Vascular Integrity

The no-reflow phenomenon relates to the inability to reperfuse regions of the myocardium after ischemia, despite removal of the large epicardial coronary artery occlusion. The mechanism involves microvascular obstruction. In experimental studies, using markers for flow (thioflavin S, carbon black, microspheres), perfusion defects associated with no-reflow demonstrated ultrastructural evidence of localized endothelial swelling and blebs that appeared to obstruct flow. In humans no-reflow is more complicated due to the microemboli of atherosclerotic debris and thrombi generated by percutaneous coronary intervention. The no-reflow zone expands during the first few hours of reperfusion suggesting an element of reperfusion injury. In animal models, extensive no-reflow was associated with worse infarct expansion. The phenomenon of no-reflow following reperfusion therapy for myocardial infarction in humans has been demonstrated by magnetic resonance imaging, echo contrast agents, thallium, technecium-99m-labeled albumin microspheres, Thrombolysis In Myocardial Infarction (TIMI) scores, and myocardial blush grade. Patients exhibiting no-reflow following reperfusion therapy for myocardial infarction have greater left ventricular dilation and remodeling, more congestive heart failure, shock, and reduced survival. Certain vasodilators (adenosine, nitroprusside, nicorandil, and calcium blockers) are used acutely in the catheterization laboratory and appear to improve no-reflow, but systematic studies on therapy for no-reflow are needed. There is now clinical evidence that no-reflow is a strong predictor of long-term mortality that is independent of and beyond that provided by infarct size. Identifying and treating no-reflow may have important benefits including enhancing delivery of nutrients and cells required for healing and reducing infarct expansion and ventricular remodeling, which ultimately may reduce congestive heart failure and mortality.

Diverse morphologic manifestations of cardiac allograft vasculopathy: A pathologic study of 64 allograft hearts

Cardiac allograft vasculopathy (CAV) is a major limitation to the long-term success of cardiac transplantation. Although there are published descriptions of the lesions, there have been no studies delineating the pathology of CAV in a large series of patients who underwent retransplantation for CAV. We reviewed archival records and microscopic sections of surgically explanted hearts from 64 patients who underwent cardiac retransplantation: 54 adults (18 to 70 years old) and 10 children (3 to 15 years old). Vascular lesions were categorized as showing intimal fibromuscular hyperplasia, atherosclerosis and/or inflammation. The degree of luminal narrowing was estimated from gross descriptions and microscopic sections. In total, 75% of hearts had evidence of acute cellular rejection, mostly mild. Intramyocardial arteries showed primarily intimal fibromuscular hyperplasia and inflammation with no atheromas present. Large and branch epicardial coronary arteries were narrowed in at least one artery of all hearts. Lesions in the epicardial coronary arteries were composed of intimal fibromuscular hyperplasia, atherosclerosis and/or inflammation affecting one or more vascular layers (intima, media and adventitia). Severe CAV with >75% luminal narrowing was seen in the LAD in 17% of hearts, the LCx in 17% and the RCA in 22% of hearts. Two hearts had severe narrowing of the left main coronary artery. Nineteen arteries had luminal thrombi. All hearts had narrowing of smaller epicardial branch coronary arteries that was often severe. Atheromas were present in arteries of adults and children; thus, not all atheromas could be considered pre-existing prior to transplantation. Both arteries and veins showed intimal hyperplasia and inflammation. CAV is a pathologically multifaceted disorder that affects large and small epicardial coronary arteries of adults and children, with different types of lesions: intimal fibromuscular hyperplasia; atherosclerosis; and/or inflammation (vasculitis). Therapies to address this disease must take into account the protean nature of the vascular lesions.

Effects of myocardial constraint on the passive mechanical behaviors of the coronary vessel wall

The large epicardial coronary arteries and veins span the surface of the heart and gradually penetrate into the myocardium. It has recently been shown that remodeling of the epicardial veins in response to pressure overload strongly depends on the degree of myocardial support. The nontethered regions of the vessel wall show significant intimal hyperplasia compared with the tethered regions. Our hypothesis is that such circumferentially nonuniform structural adaptation in the vessel wall is due to nonuniform wall stress and strain. Transmural stress and strain are significantly influenced by the support of the surrounding myocardial tissue, which significantly limits distension of the vessel. In this finite-element study, we modeled the nonuniform support by embedding the left anterior descending artery into the myocardium to different depths and analyzed deformation and strain in the vessel wall. Circumferential wall strain was much higher in the untethered than tethered region at physiological pressure. On the basis of the hypothesis that elevated wall strain is the stimulus for remodeling, the simulation results suggest that large epicardial coronary vessels have a greater tendency to become thicker in the absence of myocardial constraint. This study provides a mechanical basis for understanding the local growth and remodeling of vessels subjected to various degrees of surrounding tissue.

Capillary Perfusion and Wall Shear Stress Are Restored in the Coronary Circulation of Hypertrophic Right Ventricle

It has been shown that right ventricle (RV) hypertrophy involves significant compensatory vascular growth and remodeling. The objective of the present study was to determine the functional implications of the vascular growth and remodeling through a full flow analysis of arterial tree down to first capillary segments. A computer reconstruction of RV branches including the proximal right coronary artery to the posterior descending artery was established based on measured morphometric data in arrested, vasodilated porcine heart. The flows were computed throughout the reconstructed trees based on conservation of mass and momentum and appropriate pressure boundary conditions. It was found that the flow rate was significantly increased in large epicardial coronary arteries in hypertrophic as compared with control hearts but normalized in the intramyocardial coronary arteries and smaller vessels in RV hypertrophy primarily because of the significant increase in number of arterioles. Furthermore, the wall shear stress was restored to nearly homeostatic levels throughout most of the vasculature after 5 weeks of RV hypertrophy. The compensatory remodeling in RV hypertrophy functionally restores the perfusion at the arteriolar and capillary level and wall shear stress in most of larger vessels. This is the first full analysis of coronary arterial tree, with millions of vessels, in cardiac hypertrophy that reveals the compensatory adaptation of structure to function.

Variable Response of Conductance and Resistance Coronary Arteries to Endothelial Stimulation in Patients With Heart Failure Due to Nonischemic Dilated Cardiomyopathy

Attenuation of endothelial-dependent coronary vasodilation has been reported in idiopathic dilated cardiomyopathy and anatomically normal coronaries; however, data are insufficient for understanding the incidence and extent of this finding. The response of conductance and resistance coronary arteries to endothelial stimulation with acetylcholine was examined in 25 patients. Coronary blood flow had a variable response to acetylcholine and suggested coronary endothelial dysfunction in approximately half of the patients. Abnormal endothelial dysfunction involved the large conductance epicardial coronary arteries and the small resistance vessels. Abnormal endothelial response of coronary blood flow to acetylcholine could not be predicted by demographic and hemodynamic data. Coronary artery endothelial function is heterogeneous in patients with idiopathic dilated cardiomyopathy. Endothelial dysfunction is present in approximately half of the cases and involves both resistance as well as conductance coronary blood vessels. Furthermore, coronary endothelial function cannot be predicted by demographic and hemo-dynamic parameters or left ventricular ejection fraction.

Off-Pump Coronary Revascularization: Operative Technique

Off-pump coronary artery bypass grafting can be performed in most patients undergoing surgical myocardial revascularization. The selection of patients for off-pump surgery is dependent on the surgeon’s knowledge and comfort with the techniques of off-pump revascularization. Early in a surgeon’s experience with off-pump revascularization, it is best to select patients with normal left ventricular size and function, relatively large epicardial coronary arteries free of diffuse calcific atherosclerosis, and coronary artery disease limited to the left anterior descending and right coronary artery systems. As the surgeon gains experience and confidence with off-pump techniques, patients with decreased left ventricular function, enlarged hearts, and coronary artery disease of the circumflex system may be performed off-pump. When the surgeon has mastered the techniques of off-pump coronary surgery, nearly all patients presenting for coronary revascularization may be considered, including those with severe left main coronary artery stenosis, poor left ventricular function, and intramyocardial coronary arteries. Relative contraindications to off-pump myocardial revascularization include patients with severely enlarged and dysfunctional hearts, mitral insufficiency, or small and diffusely diseased coronary arteries. Patients with hemodynamic instability and those with chest anatomy that prevents rightward displacement of the heart, such as pectus excavatum or previous left pneumonectomy, should not be selected for off-pump revascularization. Similar to on-pump coronary artery bypass grafting, off-pump myocardial revascularization is a complex operation composed of many steps. The operative steps of off-pump coronary artery revascularization are (1) incision and conduit preparation; (2) patient positioning; (3) target vessel exposure; (4) target vessel stabilization; (5) target vessel hemostasis and ischemia prevention; (6) construction of anastomoses; and (7) closure. Off-pump myocardial revascularization has the potential benefit of lowering the risk of coronary surgery by eliminating cardiopulmonary bypass and ascending aortic manipulation. The use of in situ and composite arterial grafts for coronary revascularization avoids the need for ascending aorta manipulation to construct proximal anastomoses. In this article, the techniques used in off-pump, multivessel coronary artery bypass grafting with in situ and composite arterial grafts is illustrated. Using these techniques of coronary artery exposure and stabilization, off-pump coronary revascularization can be performed safely and accurately in the majority of patients presenting for surgical revascularization. Whether off-pump revascularization lowers the risk of surgical revascularization has been a highly debated and controversial issue in coronary surgery during the last decade. Off-pump revascularization has the potential for lowering the risk of coronary surgery by eliminating cardiopulmonary bypass, and all arterial off-pump revascularization using in situ and composite grafts has the potential to further reduce risk by eliminating the need for aortic manipulation.