EXPERIMENTAL ATTEMPTS TO INCREASE THE BLOOD SUPPLY TO THE DOG'S HEART BY MEANS OF CORONARY SINUS OCCLUSION

[Coronary sinus reducer : Literature review and issues surrounding the France Reducer registry]

Coronary sinus Reducer implantation is a percutaneous technique used to treat patients suffering from refractory angina pectoris. The device narrows the coronary sinus, increases the back pressure in the myocardial venous system and forces redistribution of coronary blood flow from less ischemic subepicardium to the more ischemic subendocardium. Multiple clinical studies had proven its efficacy to alleviate myocardial ischemia and related symptoms, and to improve the quality of life of patients with refractory symptomatic chronic coronary artery disease for whom coronary revascularization is deemed unsuitable. This literature review aims to expose the device design, its mechanisms of action, and the clinical data supporting its use. Since November 2021 Reducer's reimbursement has been granted in France by the national health authority. It is the first device to be approved under a newly established reimbursement approval process. A transitional coverage is provided with opportunities for renewal before applying for full-time reimbursement. To fulfill the requirements of the National Commission for Evaluation of Medical Devices and Health Technologies, the French Society of Cardiology has been creating the France Reducer registry. This clinical registry has been collecting data from patients undergoing coronary sinus Reducer implantation regarding their clinical situation, periprocedural information, and one-year follow-up. It is crucial for the future of this emerging therapeutic option in France. To date, 215 patients from 28 centers have been included between June 2022 and September 2023.

Technical aspects in coronary sinus Reducer implantation

Refractory angina is a growing problem, predominantly due to advanced coronary artery disease, associated with a reduced quality of life and an increased hospitalisation rate with a corresponding impact on healthcare resources. There is an unmet clinical need to be addressed by novel therapeutic approaches. Over the last few years, a treatment approach causing a controlled coronary sinus narrowing by implantation of a balloon-expandable, hourglass-shaped, stainless steel mesh (i.e., the coronary sinus Reducer) has arisen with promising initial short-term and midterm results, in terms of reducing angina and ischaemia burden and improving quality of life. Guidance with proper implantation algorithms and knowledge on how to address potential complications will improve interventional outcomes and foster a wider application of this novel therapeutic approach. In this review, we summarise the implantation technique, the causes of potential complications, and algorithms focusing upon their practical management, based on the experience of the authors.

The Coronary Sinus Reducer – Clinical Evidence and New Perspectives On An Emerging Tool in the Treatment of Refractory Angina

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Coronary Sinus Rupture Repair: Patency Is Important

We report a case of coronary sinus (CS) injury with a retrograde cardioplegia catheter and repair that compromised CS patency. This resulted in acute global cardiac dysfunction shortly after weaning from bypass, which reversed after patch repair with confirmed CS patency. The case report shows that acute CS occlusion may not be tolerated in some humans.

Is Cardioprotection Dead?

For >4 decades, the holy grail in the treatment of acute myocardial infarction has been the mitigation of lethal injury. Despite promising initial results and decades of investigation by the cardiology research community, the only treatment with proven efficacy is early reperfusion of the occluded coronary artery. The remarkable record of failure has led us and others to wonder if cardioprotection is dead. The path to translation, like the ascent to Everest, is certainly littered with corpses. We do, however, highlight a therapeutic principle that provides a glimmer of hope: cellular postconditioning. Administration of cardiosphere-derived cells after reperfusion limits infarct size measured acutely, while providing long-term structural and functional benefits. The recognition that cell therapy may be cardioprotective, and not just regenerative, merits further exploration before we abandon the pursuit entirely.

Percutaneous Device to Narrow the Coronary Sinus: Shifting Paradigm in the Treatment of Refractory Angina? A Review of the Literature

Refractory angina pectoris is defined as a chronic debilitating condition characterized by the presence of chronic anginal symptoms due to a severe obstructive and/or diffuse coronary artery disease that cannot be controlled by the combination of medical therapy and/or revascularization (percutaneous or surgical). In addition, the presence of myocardial ischemia as a cause of the symptoms must have been documented. The coronary sinus reducer (CSR) is a recently introduced percutaneous device to treat patients with severe anginal symptoms refractory to optimal medical therapy and not amenable to conventional revascularization. The purpose of this review is to describe the current evidence from available studies measuring the clinical effect of the CSR implantation on the health and well-being of patients with refractory angina.

Safety and efficacy of a device to narrow the coronary sinus for the treatment of refractory angina: A single-centre real-world experience

Objective

The coronary sinus Reducer is a recently introduced device to treat patients with severe angina symptoms refractory to optimal medical therapy and not amenable for conventional revascularisation. We aimed to assess the safety and efficacy of the Reducer in a real-world cohort of patients with refractory angina.

Methods

This is a single-centre retrospective registry. Patients with severe angina symptoms, objective evidence of myocardial ischaemia using any adequate non-invasive modality and without options for conventional revascularisation were regarded eligible for Reducer implantation.

Results

Twenty-three patients (74 % male, mean age 70 ± 8 years, 91.3 % previous bypass surgery, 82.6 % previous percutaneous intervention, 47.8 % previous myocardial infarction, 52.2 % diabetes mellitus) underwent Reducer implantation. The safety endpoint (successful implantation of the first device without device-related adverse events) was met in all patients. After a median follow-up of 9 (8–14) months the efficacy (any reduction in Canadian Cardiovascular Society (CCS) class and revascularisation-free survival) was reached in 17 patients (74 %): 8 patients (34.8 %) improved by 1 CCS class, 7 (30.4 %) by 2 CCS classes and 2 (8.7 %) by 3 CCS classes. One patient died 4 months after implantation because of progressive heart failure (not associated with Reducer implantation).

Conclusion

In this single-centre real-world experience, Reducer implantation was safe and demonstrated excellent clinical efficacy in the treatment of refractory angina at mid-term follow-up.

Myocardial revascularization by coronary arterial bypass graft: past, present, and future

The history of coronary artery bypass graft surgery is an amazing story that evolved from a basic understanding of the etiology of coronary artery disease to highly sophisticated methods of restoring blood flow to the myocardium. Adjunctive techniques of anticoagulation, coronary artery imaging, and cardiopulmonary bypass contributed greatly to our ability to provide surgical revascularization. Today, coronary artery bypass graft surgery is the treatment of choice for many patients with complex coronary artery disease. The future will certainly bring improved results with better graft patency with less operative insult and morbidity as the final chapter in the story remains untold.

History of surgical treatment of ischemic heart disease--pre-'coronary bypass grafting' era

BACKGROUND AND AIM

To review the various concepts, surgical experiments, and actual procedures performed for the treatment of ischemic heart disease, which eventually led to the evolution of direct coronary artery bypass surgery.

METHODS

References were collected from original articles and through pubmed search.

RESULTS

Various concepts and procedures were introduced, all with the aim of increasing myocardial blood flow and relief of angina. These included creation of vascular adhesions, denervation, thyroidectomies, using other organs for providing blood supply, and intramyocardial implantation of bleeding systemic arteries.

CONCLUSION

Historically various innovative concepts existed and a variety of procedures were performed for treating ischemic myocardium, with variable results. These procedures continued till the evolution of direct coronary artery bypass grafting.

A novel strategy for increasing wall thickness of coronary venules prior to retroperfusion

The sudden exposure of veins to arterial pressures during coronary venous retroperfusion may cause rupture of small venules. Our rationale is to first occlude the coronary vein, which will cause an increase in pressure intermediate to arterial and venous values, and hence lead to remodeling and increased wall thickness of the veins prior to retroperfusion. To accomplish this objective, five pigs were subjected to left anterior descending (LAD) vein ligation while six pigs served as sham. Myocardial tissue samples were obtained from the area adjacent to the LAD vein at four transmural locations of the left ventricular free wall: epicardial surface, subepicardium, midmyocardium, and endocardium. Arterioles and venules from the experimental and sham control groups were photographed, and the following measurements were made: inner and outer circumferences, inner and outer areas, major and minor diameters, and intima-media thickness. Each vessel was categorized in four different orders according to lumen diameter. Our results show that intima-media thickness was larger in the experimental group in all four regions of the heart and in all four orders of the vessels, although venules from the epicardial region showed the largest increase in thickness. The intima-media thickness-to-radius ratio was also larger in the experimental group and decreased from epicardial to endocardial region of the heart and from order 1 to order 4 of the vessels. The present study provides a rationale for the development of coronary retroperfusion strategy that avoids vessel rupture and hemorrhage in the postcapillary venules.

Nonuniformity of axial and circumferential remodeling of large coronary veins in response to ligation

The pressure-induced remodeling of coronary veins is important in coronary venous retroperfusion. Our hypothesis is that the response of the large coronary veins to pressure overload will depend on the degree of myocardial support. Eleven normal Yorkshire swine from either sex, weighing 31–39 kg, were studied. Five pigs underwent ligation of the left anterior descending (LAD) vein, and six served as sham-operated controls. The ligation of the coronary vein caused an increase in pressure intermediate to arterial and venous values. After 2 wk of ligation, the animals were euthanized and the coronary vessels were perfusion-fixed with glutaraldehyde. The LAD vein was sectioned, and detailed morphometric measurements were made along its length from the point of ligation near the base down to the apex of the heart. The structural remodeling of the vein was circumferentially nonuniform because the vein is partially embedded in the myocardium; it was also axially nonuniform because it is tethered to the myocardium to different degrees along its axial length. The wall area was significantly larger in the experimental group, whereas luminal area in the proximal LAD vein was significantly smaller in the same group compared with sham-operated controls. The wall thickness-to-radius ratio was also significantly larger in the experimental group in proportion to the increase in pressure. The major conclusion of this study is that the response of the vein depends on the local wall stress, which is, in part, determined by the surrounding tissue. Furthermore, the geometric remodeling of the coronary vein restores the circumferential stress to the homeostatic value.

LV-powered coronary sinus retroperfusion reduces infarct size in acutely ischemic pigs

BACKGROUND

We developed a prosthetic left ventricle (LV) to coronary sinus (CS) shunt (LVCSS) that is autoregulating and provides LV-powered retrograde perfusion of the coronary sinus.

METHODS

Each of 20 Yorkshire pigs underwent 1 hour of left anterior descending diagonal artery occlusion followed by 3 hours of reperfusion. The controls (n = 5) did not have shunt treatment. The LVCSS group (n = 9) underwent shunt treatment during the ischemic period. The LVCSS with partial coronary sinus occlusion (PCSO) group (LVCSS+PCSO, n = 6) underwent shunt treatment and PCSO during the ischemic period. Vital staining and planimetry techniques were used to determine the area at risk for infarction and the area of necrosis.

RESULTS

The area at risk was not significantly different among groups. The area of necrosis was decreased by 53% in the LVCSS group and by 73% in the LVCSS+PCSO group when compared to controls (p<0.01 among all groups).

CONCLUSIONS

The LVCSS reduces infarct size in pigs after acute coronary artery occlusion. The addition of PCSO to LVCSS further improves myocardial salvage.

Feasibility of radiofrequency powered, thermal balloon ablation of atrioventricular bypass tracts via the coronary sinus: in vivo canine studies

Radiofrequency catheter ablation of left-sided accessory pathways is technically demanding and usually requires left heart catheterization. The feasibility of creating lesions from within the coronary sinus of sufficient size to ablate accessory pathways in humans using a thermal balloon catheter was studied in 20 dogs. In group 1 (n = 14), 17 thermal inflations were performed in 12 dogs at either 70 degrees, 80 degrees, or 90 degrees C each for 30 or 60 seconds (in 2 dogs two non-thermal control inflations were performed). Animals were sacrificed 6.3 +/- 1.6 days later. In group 2 (n = 6), seven thermal inflations were performed at 90 degrees C each for 180, 300, or 360 seconds. Group 2 animals received antiplatelet and anticoagulant therapy for 1 week and were sacrificed at 13 +/- 10.7 days. In both groups, hemodynamic, angiographic, and electrocardiographic studies were performed at baseline, 1 hour after inflation, and prior to sacrifice. All dogs remained clinically stable throughout the procedure and no complications were attributed to the effect of thermal inflation. Thermal lesions measured 14.4 +/- 4.4 mm in length and extended from the coronary sinus intima to a mean depth of 2.9 +/- 1.2 mm (range 1.4-6.5 mm). Group 2 lesions were significantly deeper than group 1 lesions (P = 0.03). Of the 24 thermal lesions created, atrial necrosis was present in 23 and ventricular necrosis in 11. In all lesions there was some degree of either atrial necrosis, ventricular necrosis, or both. A variable degree of coronary sinus thrombus was present in 18 dogs without clinical sequelae. It is concluded that radiofrequency balloon heating via the coronary sinus can create thermal lesions in the atrioventricular sulcus of dogs that may be of sufficient size to ablate accessory left-sided pathways in humans.

Intermittent coronary sinus occlusion after coronary arterial ligation results in venous retroperfusion

Coronary sinus occlusion retards necrosis of ischemic myocardium. To test the hypothesis that coronary sinus occlusion induces retrograde venoarterial flow, the coronary arteriovenous pressure gradient and the coronary arterial oxygen saturation were measured distal to a left anterior descending coronary artery ligature in dogs. In parallel, we constructed a mathematical model of known coronary physiology to characterize pressure and flow patterns during coronary sinus occlusion. In dogs, coronary sinus occlusion produced a systolic pressure gradient between the coronary artery and the coronary sinus of -20 +/- 9 mm Hg (higher venous pressure, p less than 0.0001) and a positive diastolic gradient of 3 +/- 5 mm Hg (lower venous pressure p less than 0.01). An average reduction in the oxygen saturation in the ligated coronary artery of 20 +/- 13% was also observed (p less than 0.005) consequent to admixture of venous (desaturated) blood. By graded inflation of the coronary sinus balloon, it was demonstrated that desaturation of arterial blood typically occurs above a coronary sinus systolic pressure of 40-50 mm Hg. The mathematical model indicates the possibility of venoarterial pressure gradients and reversal of flow at the microcirculatory level during coronary sinus occlusion. These studies provide evidence that retrograde flow into the ischemic zone occurs in association with intermittent coronary sinus occlusion. Thus, alternating flow over the ischemic territory may be the mechanism of myocardial salvage during intermittent coronary sinus occlusion.

Coronary sinus interventions during cardiac surgery

There is renewed interest in protecting jeopardized myocardium during regional and global ischemia by coronary sinus retroperfusion. Advances in catheter design and imaging techniques have made access to the coronary sinus easier and safer. Retrograde coronary sinus perfusion, aortovenous bypass, pressure-controlled intermittent coronary sinus occlusion, and synchronized retrograde perfusion have emerged as new techniques by which blood can be redirected through the coronary sinus to nourish ischemic myocardium beyond a coronary occlusion. The purpose of this review is to summarize the current results and applications of these coronary sinus interventions, and show how they can benefit the cardiac surgeon in clinical practice.

Paradoxical increase of ventricular fibrillation threshold in response to coronary sinus obstruction

We determined the ventricular fibrillation threshold (VFT) changes in response to graded coronary sinus (CS) obstruction in 13 chloralose-anesthetized dogs with fixed heart rate (150 min-1, mean systemic arterial pressure (80 mm Hg), and cardiac index (100 ml/min.kg-1 body weight). VFT in milliamperes (VFTmA) increased linearily with CS pressure (CSP) increases up to 41.2 +/- 1.4 mm Hg (VFTmA = 6.5 + 0.14 CSP mm Hg, p less than 0.01). Total coronary venous effluent (CBF) did not change significantly, suggesting compensatory coronary vasodilation. Myocardial O2 consumption also remained unchanged. At higher CSP, both CBF and VFT declined precipitously (VFTmA = 20.9 - 0.27 CSP mm Hg, p less than 0.02). With simultaneous increases of systemic arterial along with CSP, VFT increased again along with the CSP-induced reduction of gradient until it reached 42.8 +/- 3.2 mm Hg. We conclude that with coronary venous obstruction, despite coronary perfusion gradient reduction to about 40 mm Hg, CBF remains constant. This constant flow vasodilation is associated with substantial (82%) VFT increase. The mechanism may involve enhanced homogeneity of CBF distribution and increased extracellular fluid.

Coronary sinus retroperfusion and pressure-controlled intermittent coronary sinus occlusion (PICSO) for myocardial protection

This article provides an overview of the current status of coronary venous interventions for myocardial protection. It reviews the histories, principles, and techniques of the interventions as well as the challenges for the future.

The dynamics of the coronary venous system in the dog

The coronary vascular system is characterised by a small blood-volume, high resistance arterial system, in which flow is primarily diastolic, a capillary-venule exchange system and a large blood volume, low resistance venous system with predominantly systolic flow. In order to understand the venous component we measured intramyocardial pressure (IMP), peripheral (PVP) and central (CVP) coronary venous pressure, as well as phasic coronary sinus outflow. Based on the experimental data, a model is proposed to describe the hemodynamics of the coronary venous system. This model consists of an intramyocardial vascular storage region into which the arterial blood flows during diastole. During systole, the pressure in the storage vessels increases, pushing the peripheral and epicardial venous system. Blocking the inflow tends to empty the 'storage' and the peripheral regions, reducing venous pressures. Occlusion of the outflow increases the blood volume in these regions, elevating venous pressures. The observations of peak (IMP-PVP) vs peak venous flow during vagal, right abd left stellate stimulation conform satisfactorily with the model.

Selective retrograde coronary venous perfusion

The theoretical concept of delivering oxygenated blood to an ischemic myocardium by way of the coronary venous system antedated by many decades the present widespread utilization of coronary artery bypass grafting. Diffuse arterial atherosclerosis has limited the effectiveness of coronary artery bypass grafting in about 15% of patients seen with significant angina pectoris. Consequently, there has been renewed interest in selectively reversing the flow in certain coronary veins through coronary venous bypass grafts. This collective review details the physiology and anatomy of the coronary venous system. It then discusses the early attempts to globally retroperfuse the entire coronary venous system through the coronary sinus. Finally, the current experimental and clinical attempts to selectively retroperfuse just one region of the coronary venous system are presented and reviewed.

Demonstration of an inadvertently created aorto-coronary venous anastomosis: evidence against the clinical effectiveness of retrograde coronary venous perfusion

Arterilization of the coronary venous system has been suggested as a means of myocardial perfusion. We recently studied a patient with a saphenous vein aorto=coronary venous bypass graft created inadvertently during surgery intended to bypass the anterior descending artery. We selectively injected onctrast into this graft during balloon occlusion of the coronary sinus both before and after sublingual nitroglycerin. No arterial visualization was demonstrated from the vein and no evidence to suggest perfusion of the myocardium was found.

The cardiac veins and retrograde coronary venous perfusion

Study of retrograde coronary venous perfusion has been greatly overshadowed in the past decade by the advent and success of direct coronary artery revascularization. Recently there has been renewed interest in retrograde venous perfusion as a possible means of restoring myocardial circulation in selected patients. This paper reviews the anatomy and physiology of the cardiac venous system and the history of retrograde venous perfusion, with emphasis on recent experimental work and clinical trials involving retrograde coronary vein perfusion (RCVP).

The Effect of Arterialization of the Coronary Sinus in Dogs on Mortality Following Acute Coronary Occlusion

The mortality rates were determined in two groups of dogs following acute circumflex artery occlusion. Both groups were surgically prepared in the same manner. In a group of 20 dogs the coronary sinus was cannulated to divert the blood into the left jugular vein. Circumflex artery ligation resulted in 70 per cent mortality within one hour. In a second group of 10 dogs the coronary sinus was arterialized from the left subclavian artery and the sinus mean pressure was held at 50 mm. Hg. In this group circumflex artery ligation resulted in 100 per cent survival for one hour. Statistical analysis shows the results to be highly significant. The results strongly suggest that arterialization of the coronary sinus protects the hearts of dogs from ventricular fibrillation following coronary artery ligation.