Precision Incision: Robotic Coronary Revascularization via 3.9-cm Minithoracotomy

ABSTRACT: Coronary artery bypass grafting remains the treatment choice for coronary artery disease; but sternotomy, the most commonly used approach, compromises its benefits with postoperative morbidity, higher complication rates, and prolonged length of hospital stay. Despite this, minimally invasive and robotic-assisted technology has not been adopted or widely embraced because supporting literature on robotic-assisted coronary artery bypass grafting is extremely limited. Since 2005, the cardiothoracic surgical team at our institution has been developing and maturing an effective method using robotic harvesting of the left internal mammary artery (LIMA) and beating heart surgery through a minithoracotomy for coronary revascularization. This surgical technique involves precisely placing the robotic endoscopic port immediately over the left anterior descending (LAD) artery target site. The robotically harvested LIMA is secured to the epicardium at the LAD target, the robotic instruments are removed, and the endoscopic port site is enlarged slightly greater than 1 cm to become the minithoracotomy and allow for LIMA-to-LAD anastomosis. The other two robotic ports are used to complete the procedure without a need for additional incisions. This standardized method has been used in more than 750 patients, and since 2009, the last 377 consecutive non-rib-spreading minithoracotomy incisions measured a median of 3.9 cm (mean [SD], 4.16 [1.2748] cm; range, 2.3-12.0 cm). This "How I Do It" article describes our methods in detail and associated robotic nuances.     

Evaluation of a Novel Laser-assisted Coronary Anastomotic Connector - the Trinity Clip - in a Porcine Off-pump Bypass Model

To simplify and facilitate beating heart (i.e., off-pump), minimally invasive coronary artery bypass surgery, a new coronary anastomotic connector, the Trinity Clip, is developed based on the excimer laser-assisted nonocclusive anastomosis technique. The Trinity Clip connector enables simplified, sutureless, and nonocclusive connection of the graft to the coronary artery, and an excimer laser catheter laser-punches the opening of the anastomosis. Consequently, owing to the complete nonocclusive anastomosis construction, coronary conditioning (i.e., occluding or shunting) is not necessary, in contrast to the conventional anastomotic technique, hence simplifying the off-pump bypass procedure. Prior to clinical application in coronary artery bypass grafting, the safety and quality of this novel connector will be evaluated in a long-term experimental porcine off-pump coronary artery bypass (OPCAB) study. In this paper, we describe how to evaluate the coronary anastomosis in the porcine OPCAB model using various techniques to assess its quality. Representative results are summarized and visually demonstrated.     

A technique for measurement of retrograde coronary blood flow in intact anesthetized dogs.

A technique for measurement of retrograde coronary blood flow in intact anesthetized dogs is described. Occlusion of the coronary artery is produced by the inflation of a small rubber balloon at the tip of a no. 9 cardiac catheter placed under fluorescopy in a branch of the left coronary artery. Blood which bleeds back from the occluded coronary artery through the no. 9 catheter is diverted into a small reservoir of 1-ml capacity. The time to fill this reservoir is recorded electrically. Retrograde coronary blood flow is calculated from the time required to fill this reservoir. Results indicate good repeatability of meadurements. The technique seems to be a simple, adequate, and convenient means for assessing agents for possible vasodilator action on the collateral circulation in intact animals.     

Bilateral internal thoracic artery grafting: current state of the art

The purpose of this article is to review the key literature and assess the current status of bilateral internal thoracic artery grafting. Numerous retrospective studies have demonstrated a benefit of bilateral internal thoracic artery grafting over single internal thoracic artery grafting in terms of the long-term risk of all-cause death, cardiac-related death, and cardiac events. The survival benefit of bilateral internal thoracic artery grafting manifests relatively early after operation for high-risk patients. The skeletonization technique reduces the risk of sternal wound complications in all patients and particularly in those with diabetes. Both the left and right internal thoracic arteries have better patency when grated to the left coronary territory than saphenous vein. However, the right internal thoracic artery does not always have good patency when grafted to the right coronary artery. Bilateral internal thoracic artery grafting using the skeletonization technique is recommended for revascularization of the left coronary territory.     

Construction and evaluation of a coronary catheter for chronic implantation in dogs

Construction of a Silastic catheter and the procedure for chronic implantation in a coronary artery in dogs is described. In addition, studies designed to evaluate whether chronic coronary artery catheterization altered coronary vascular reactivity and myocardial function are presented. The results of these studies indicate that chronic implantation of the catheter in a coronary artery of conscious dogs does not significantly interfere with the normal reactivity of the coronary vascular bed, does not compromise regional or global left ventricular function, and does not induce collateral vessel development. This technique will be useful in studies involving the neural and metabolic regulation of the coronary circulation in animals subjected to exercise and/or exercise training.     

Coronary artery anomalies detected by MSCT-coronary angiography in the adult

Background. Before coronary evaluation by modern imaging techniques was feasible, premorbid diagnoses of coronary artery anomalies (CAAs) were usually made fortuitously by invasive coronary angiography (ICA). However, this technique is limited by its invasive and projectional nature. Coronary magnetic resonance angiography (CMRA) and multi-slice computed tomography (MSCT) broadened clinical information by enabling visualisation of the coronary arteries in their anatomical environment. Methods. This case series visualises and reviews anomalous coronary artery from the opposite sinus (ACAOS) and coronary artery fistulae. All CAAs were detected by means of 64-slice dual source computed tomography after 1000 cardiac scans at the Erasmus MC, Rotterdam, the Netherlands. Results. Eight ACAOS cases, one anomalous left coronary artery from the pulmonary artery (ALCAPA) and one congenital aneurysm of an aortic sinus were found. Seven out often detected CAAs were considered malignant whereas three CAAs of the ACAOS type (retroaortic path) were considered benign. Significant coronary artery disease was found in three out of eight ACAOS cases. In one of the ACAOS cases complete evaluation of the anomalous coronary artery was limited by motion artifacts. All five cases of right ACAOS were referred for MSCT because the right coronary artery could not be located by invasive angiography. Conclusion. All CAAs were easy to diagnose because of 3D imaging and high temporal and spatial resolution. High resolution made it possible to not only depict coronary artery abnormalities, but also to quantify luminal and vessel properties such as stenosis grade, aspects of plaque, anomalous vessel length, luminal area ratio and the asymmetry ratio. Because of its comprehensiveness, MSCT can be an effective imaging modality in patients suspected of coronary artery abnormalities caused by coronary artery disease, CAAs, or a combination of both. (Neth Heart J 2008;16:369-75.)     

Intraoperative in situ radial artery conduit flow assessment

A technique is described for simple flow assessment of the in situ radial artery conduit during coronary bypass via a small incision. This technique allows morphologic and physiologic direct intraoperative assessment of radial artery quality and expands the use of radial artery during coronary artery surgery.     

Blood Supply to the Interventricular Septum of the Heart in Rodents with Intramyocardial Coronary Arteries

The blood supply to the interventricular septum of the heart was studied in a sample of 1634 specimens belonging to four rodent families, Cricetidae, Arvicolidae, Gliridae, and Muridae. Most specimens (n = 1604) were examined using a corrosion-cast technique, while the remaining 30 were studied by histological techniques. In 1417 cases the coronary artery pattern was normal, and the interventricular septum was fundamentally supplied by one or rarely two septal arteries arising from the right and/or left coronary arteries. In 72 specimens the right and left coronary arteries were normal, while the septal artery arose from a separate ostium in the aorta, behaving as a third coronary artery. The remaining 145 animals possessed anomalies in the origin of the coronary arteries, and the septum was also principally irrigated by a septal artery. In 5 of these 145 anomalous cases the septal artery originated from a separate ostium in the aorta. In all specimens examined a less important vascularization of the septum was established through thinner penetrating vessels originating from the right and/or left coronary arteries. Existence of one or rarely two septal arteries is the most constant feature of the coronary artery arrangement in rodents with intramyocardial coronary arteries.     

Robotically assisted coronary endarterectomy

Robotic assistance has enabled coronary artery bypass surgery to be performed safely in a completely endoscopic fashion, but diffusely diseased target vessels may pose a technical challenge. We present a case in which coronary endarterectomy was performed on the left anterior descending coronary artery during a two-vessel totally endoscopic coronary artery bypass procedure. A 52-year-old woman presented with intermittent substernal pain. Preoperative studies showed diffuse disease in the left coronary artery system. Bilateral internal mammary arteries were harvested robotically using a skeletonized technique in a completely endoscopic fashion. Cardiopulmonary bypass was achieved via peripheral cannulation, and the heart was arrested with intermittent cold antegrade hyperkalemic blood cardioplegia delivered via an ascending aortic occlusion balloon catheter. The first obtuse marginal anastomosis was performed. The left anterior descending coronary artery was diffusely diseased and heavily calcified. An end-to-side anastomosis was attempted to the right internal mammary artery with unsatisfactory results. A localized coronary endarterectomy was performed, and an extended anastomosis was completed using the right internal mammary artery. The patient recovered uneventfully and was discharged home on postoperative day 6. Diffuse coronary artery disease was once thought to be a prohibitive challenge for minimally invasive coronary bypass procedures. This case demonstrates that local coronary endarterectomy is feasible and safe in robotic totally endoscopic coronary artery bypass surgery.     

Velocity and wall shear stress patterns in the human right coronary artery.

Blood flow dynamics in the human right coronary artery have not been adequately quantified despite the clinical significance of coronary atherosclerosis. In this study, a technique was developed to construct a rigid flow model from a cast of a human right coronary artery. A laser photochromic method was used to characterize the velocity and wall shear stress patterns. The flow conditions include steady flow at Reynolds numbers of 500 and 1000 as well as unsteady flow with Womersley parameter and peak Reynolds number of 1.82 and 750, respectively. Characterization of the three-dimensional geometry of the artery revealed that the largest spatial variation in curvature occurred within the almost branch-free proximal region, with the greatest curvature existing along the acute margin of the heart. In the proximal segment, high shear stresses were observed on the outer wall and lower, but not negative, stresses along the inner wall. Low shear stress on the inner wall may be related to the preferential localization of atherosclerosis in the proximal segment of the right coronary artery. However, it is possible that the large difference between the outer and inner wall shear stresses may also be involved.     

Tissue Doppler imaging during dipyridamole and dobutamine stress echocardiography in the diagnosis of coronary heart disease

The aim of the study was to determine the sensitivity and specificity of combined high-dose dipyridamole and dobutamine stress echocardiography (stress EchoCG) in the diagnosis of coronary artery stenotic lesions in coronary heart disease in a group of patients who were unable to perform physical exercise, by using different assessment criteria (local contractile impairments and systolic velocity changes during tissue Doppler imaging). The study enrolled 68 men who had undergone dipyridamole and dobutamine stress EchoCG, longitudinal tissue Doppler imaging, and coronary angiography. Stress EchoCG could bring up to diagnostic criteria in all the patients. Coronary angiography revealed no coronary artery lesion in 18 patients, but showed single and multiple vascular lesions in 31 and 19 patients, respectively. The sensitivity and specificity of combined stress EchoCG were significantly higher than those of stress EchoCG examination. The results of combined stress EchoCG allow one to judge to a greater validity (96% sensitivity and 100% specificity) local contractile impairments corresponding to the blood supply area in the atherosclerosis-afflicted coronary artery. Analysis of systolic velocity parameters during tissue Doppler imaging permits the diagnostic value of the technique to be insignificantly improved particularly when the test results are controversial.     

Predictive value of the ear-crease sign in coronary artery disease.

The value of the ear-crease sign in predicting the presence of coronary artery disease was studied in 340 consecutive patients who underwent coronary arteriography. In this selected population, 75.6% of whom had coronary artery disease, the sensitivity of the sign was 59.5%, the specificity 81.9% and the positive predictive value 91.1%. The sign was associated with increasing age but was also independently associated with obstructive coronary artery disease. No significant correlation was found between the sign and the presence of risk factors or other signs of such disease, except for corneal arcus. In symptomatic patients the sign suggested the presence of more extensive coronary artery disease. In an asymptomatic population with a low prevalence of coronary artery disease it appears to be of limited value in predicting obstructive coronary artery disease. However, it may identify a subset of patients prone to early ageing and to the early development of coronary artery disease, whose prognosis might be improved by early preventive measures.     

A new method for the visualization of subepicardial coronary arteries in small isolated mammalian hearts

A model is described which permits direct visualization of large coronary arteries in a supported modified perfused heart preparation, using a perfluorochemical (FC-43) as perfusate. Filling of a large coronary artery with Patent Blue Dye is recorded by gated photography (color arteriography). The technique is applicable to the study of reactivity (spasm) of coronary arteries in hearts of small and large animals (rats, rabbits, dogs). The technique has the following advantages: preservation of vascular endothelium, adequate oxygenation, avoidance of major surgical intervention to implant sensors for the detection of changes in coronary diameter, quantitative evaluation of time dependent changes in geometry of large coronary arteries and simultaneous measurement of large coronary vessel and total coronary vascular resistance.     

Impact of Coronary Artery Curvature on the Longitudinal Stent Foreshortening: Real-World Observations

Longitudinal stent foreshortening is a known phenomenon, however, the impact of coronary artery curvature on longitudinal stent foreshortening remains unclear. The aim of this study is to determine the impact of coronary artery curvature on the longitudinal stent foreshortening in the real-world scenarios. A total of 86 consecutive patients underwent coronary stent implantation were included in the present study. The degree of coronary artery curvature was defined as the length of the coronary artery curvature divided by the straight length. Longitudinal stent foreshortening was defined as the stent length after implantation divided by the stent length before implantation. The mean longitudinal foreshortening rate of coronary stents was about 94% in curved coronary arteries. Longitudinal stent foreshortening rate was positively correlated with the degree of coronary artery curvature (r = –0.86, P < 0.01). Coronary artery curvature is associated with significant longitudinal foreshortening of coronary stents, thus longitudinal foreshortening should be considered on deciding the stent length in curved coronary artery and a longer stent is usually needed in curved coronary artery.     

Ultrasound Based Assessment of Coronary Artery Flow and Coronary Flow Reserve Using the Pressure Overload Model in Mice

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow reserve (CFR) in humans. Reduced CFR is accompanied by marked intramyocardial and pericoronary fibrosis and is used as an indication of the severity of dysfunction. This study explores, step-by-step, the real-time changes measured in the coronary flow velocity, CFR and systolic to diastolic peak velocity (S/D) ratio in the setting of an aortic banding model in mice. By using a Doppler transthoracic imaging technique that yields reproducible and reliable data, the method assesses changes in flow in the septal coronary artery (SCA), for a period of over two weeks in mice, that previously either underwent aortic banding or thoracotomy. During imaging, hyperemia in all mice was induced by isoflurane, an anesthetic that increased coronary flow velocity when compared with resting flow. All images were acquired by a single imager. Two ratios, (1) CFR, the ratio between hyperemic and baseline flow velocities, and (2) systolic (S) to diastolic (D) flow were determined, using a proprietary software and by two independent observers. Importantly, the observed changes in coronary flow preceded LV dysfunction as evidenced by normal LV mass and fractional shortening (FS). The method was benchmarked against the current gold standard of coronary assessment, histopathology. The latter technique showed clear pathologic changes in the coronary artery in the form of peri-coronary fibrosis that correlated to the flow changes as assessed by echocardiography. The study underscores the value of using a non-invasive technique to monitor coronary circulation in mouse hearts. The method minimizes redundant use of research animals and demonstrates that advanced ultrasound-based indices, such as CFR and S/D ratios, can serve as viable diagnostic tools in a variety of investigational protocols including drug studies and the study of genetically modified strains.     

Ultrasound Assessment of Endothelial-Dependent Flow-Mediated Vasodilation of the Brachial Artery in Clinical Research

The vascular endothelium is a monolayer of cells that cover the interior of blood vessels and provide both structural and functional roles. The endothelium acts as a barrier, preventing leukocyte adhesion and aggregation, as well as controlling permeability to plasma components. Functionally, the endothelium affects vessel tone.Endothelial dysfunction is an imbalance between the chemical species which regulate vessel tone, thombroresistance, cellular proliferation and mitosis. It is the first step in atherosclerosis and is associated with coronary artery disease, peripheral artery disease, heart failure, hypertension, and hyperlipidemia.The first demonstration of endothelial dysfunction involved direct infusion of acetylcholine and quantitative coronary angiography. Acetylcholine binds to muscarinic receptors on the endothelial cell surface, leading to an increase of intracellular calcium and increased nitric oxide (NO) production. In subjects with an intact endothelium, vasodilation was observed while subjects with endothelial damage experienced paradoxical vasoconstriction.There exists a non-invasive, in vivo method for measuring endothelial function in peripheral arteries using high-resolution B-mode ultrasound. The endothelial function of peripheral arteries is closely related to coronary artery function. This technique measures the percent diameter change in the brachial artery during a period of reactive hyperemia following limb ischemia.This technique, known as endothelium-dependent, flow-mediated vasodilation (FMD) has value in clinical research settings. However, a number of physiological and technical issues can affect the accuracy of the results and appropriate guidelines for the technique have been published. Despite the guidelines, FMD remains heavily operator dependent and presents a steep learning curve. This article presents a standardized method for measuring FMD in the brachial artery on the upper arm and offers suggestions to reduce intra-operator variability.     

Imaging of all three coronary arteries by transthoracic echocardiography. an illustrated guide

Background

Improvements in ultrasound technology has enabled direct, transthoracic visualization of long portions of coronary arteries : the left anterior descending (LAD), circumflex (Cx) and right coronary artery (RCA). Transthoracic measurements of coronary flow velocity were proved to be highly reproducible and correlated with invasive measurements. While clinical applications of transthoracic echocardiography (TTE) of principal coronary arteries are still very limited they will likely grow. The echocardiographers may therefore be interested to know the ultrasonic views, technique of examination and be aware where to look for coronary arteries and how to optimize the images.

Methods

A step-by-step approach to direct, transthoracic visualization of the LAD, Cx and RCA is presented. The technique of examination is discussed, correlations with basic coronary angiography views and heart anatomy are shown and extensively illustrated with photographs and movie-pictures. Hints concerning optimization of ultrasound images are presented and artifacts of imaging are discussed.

Conclusions

Direct, transthoracic examination of the LAD, Cx and RCA in adults is possible and may become a useful adjunct to other methods of coronary artery examination but studies are needed to establish its role.     

Exploration par tomodensitométrie multidétecteur du cœur et des artères coronaires

Due to its excellent spatial and temporal resolution, multislice computerized tomography (MSCT) allows visualizing the heart and coronary arteries. Although the indications of MSCT did not reach a consensus level yet, some trends can be stated. The advantages and limitations of MSCT in cardiac exploration are summarized in this article. The indications are mainly based on the excellent negative predictive value of MSCT regarding coronary artery disease. Hence, patients at low to moderate risk of coronary artery disease (CAD) mostly benefit of the technique. MSCT can be an alternate examination in case of non feasible or non contributive stress test. MSCT is highly contributive in the ostial analysis, in detecting abnormal coronary implantation or course, in assessing a reimplanted artery or in analysing bypass grafts. MSCT remains limited in patients with heavily calcified coronary arteries, and in patients with stented distal arteries.     

Dynamics of coronary circulation in rats]

The blood flow velocities in left anterior descending coronary artery and ascending aorta have been measured in anesthetized rats by high frequency Doppler technique. The measurement of coronary blood flow velocity by miniature ultrasonic probe (2.0 x 1.5 mm) was performed through myocardial surface. Two different forms of coronary blood flow curves were recorded. These forms of the curves depend on the value of the coronary blood flow velocity and are connected with the ascending aorta blood flow velocity. The dynamics of the coronary blood flow reactions under coronary artery occlusion and asphyxia in the rat is similar to the one in the cat and the dog, but less expressive. In experiments with vasodilators the direct dependence between linear and volume coronary artery velocities under the measurement through myocardial surface was found.     

Use of a Hanging Weight System for Coronary Artery Occlusion in Mice

Murine studies of acute injury are an area of intense investigation, as knockout mice for different genes are becoming increasingly available ^1-38. Cardioprotection by ischemic preconditioning (IP) remains an area of intense investigation. To further elucidate its molecular basis, the use of knockout mouse studies is particularly important ^{7, 14, 30, 39}. Despite the fact that previous studies have already successfully performed cardiac ischemia and reperfusion in mice, this model is technically very challenging. Particularly, visual identification of the coronary artery, placement of the suture around the vessel and coronary occlusion by tying off the vessel with a supported knot is technically difficult. In addition, re-opening the knot for intermittent reperfusion of the coronary artery during IP without causing surgical trauma adds additional challenge. Moreover, if the knot is not tied down strong enough, inadvertent reperfusion due to imperfect occlusion of the coronary may affect the results. In fact, this can easily occur due to the movement of the beating heart.Based on potential problems associated with using a knotted coronary occlusion system, we adopted a previously published model of chronic cardiomyopathy based on a hanging weight system for intermittent coronary artery occlusion during IP ³⁹. In fact, coronary artery occlusion can thus be achieved without having to occlude the coronary by a knot. Moreover, reperfusion of the vessel can be easily achieved by supporting the hanging weights which are in a remote localization from cardiac tissues.We tested this system systematically, including variation of ischemia and reperfusion times, preconditioning regiments, body temperature and genetic backgrounds³⁹. In addition to infarct staining, we tested cardiac troponin I (cTnI) as a marker of myocardial infarction in this model. In fact, plasma levels of cTnI correlated with infarct sizes (R2=0.8). Finally, we could show in several studies that this technique yields highly reproducible infarct sizes during murine IP and myocardial infarction^{6, 8, 30, 40, 41}. Therefore, this technique may be helpful for researchers who pursue molecular mechanisms involved in cardioprotection by IP using a genetic approach in mice with targeted gene deletion. Further studies on cardiac IP using transgenic mice may consider this technique.