Retrograde coronary sinus perfusion prevents infarct extension during intraoperative global ischemic arrest

Transcatheter Coronary Sinus Interventions

The coronary sinus has become a popular route for an increasing number of innovative transcatheter interventions to treat coronary and structural heart diseases. However, interventional cardiologists have limited experience with the cardiac venous system and its highly variable anatomy. In this paper, we review the anatomy of the cardiac veins as it relates to transcatheter interventions. We also provide a contemporary overview of the emerging coronary sinus-based transcatheter therapies and their growing literature.

Retrograde Coronary Sinus Perfusion for Severe Left Main Stenosis

Between April 1996 through March 1999, 15 patients with severe (> 60%) left main coronary artery stenosis became hemodynamically unstable on induction of anesthesia, in spite of optimal pharmacological management. Retrograde coronary sinus perfusion was instituted soon after the median sternotomy to improve hemodynamics until the establishment of cardiopulmonary bypass after harvesting internal mammary artery and saphenous vein grafts.

Anatomy of the intramural venous sinuses of the right atrium and their tributaries

A precise knowledge of the mode of opening of the vv. on the anterior wall of the right ventricle, i.e., directly or by means of intramural venous sinuses in the right atrium, is of fundamental importance for cardiologic methods of examination and treatment. We dissected 32 hearts obtained from cadavers belonging to adult individuals of unknown age and sex, fixed and stored in formalin. A total of 151 veins were detected for the 32 cases. The following distribution was observed: 33 right marginal vv. (m) in 29/32, 59 anterior vv. of the right ventricle (a) in 29/32, 29 vv. of the arterial cone (c) in 26/32, 17 posterior vv. of the cone (p) in 17/32, and 13 Zuckerkandl vv. (z) in 13/32. Of these veins, a) 4 m emptied into the right atrium, with one of them forming a bifurcation and emptying twice; b) 4 m continued into a small cardiac v.; c) 6 collector vv. present in 4/32 cases emptied into the right atrium and received 2 m, 5 a, 2 c, 3 p and 2 z; d) 35 intramural venous sinuses were present in 30/32 or 94% of cases emptied into the right atrium and received 15 m, 26 a, 5 c, 4 p, 3 z and 32 collector vv., into which 8 m, 28 a, 22 c, 10 p and 8 z drained. In conclusion, these venous sinuses are normal and are very important for venous drainage.

The regional effect of retrograde cardioplegia in areas of evolving ischemia

Retrograde cardioplegia (RCP) is often used for myocardial protection during coronary bypass grafting, but the regional effect of RCP in areas of evolving ischemia is unknown. We examined the functional and metabolic indices of regional myocardial preservation following acute coronary occlusion with evolving ischemia in a canine model. Following the institution of 37 degrees C cardiopulmonary bypass in 14 dogs, the left anterior descending artery (LAD) was occluded for 15 min. The hearts were then subjected to 90 min of cardioplegic arrest (12 degrees C, 15 mL/kg every 30 min). Seven had antegrade cardioplegia (ACP) alone, while seven had ACP until arrest, then RCP. No topical cooling was used. The LAD occlusion was released after the first bolus of cardioplegia. Regional temperature and pH were measured in the LAD and circumflex (nonischemic) distributions. After 90 min of ischemia and 30 min of reperfusion, all dogs were weaned from bypass. Postischemic function was determined globally by the return of developed pressure (%dP/dt) and regionally by ultrasonic wall crystals. End-ischemic ATP preservation in the LAD distribution was assessed by HPLC (mm ATP/mg protein). Results show that regional functional and metabolic indices were better maintained with RCP in the ischemic LAD distribution. Although only moderate reduction of global function was seen with ACP, the severe reduction noted in LAD regional wall motion with ACP reflects poor regional protection that can be significantly improved in evolving ischemia with RCP.

Coronary sinus pressure and arterial venting do not affect retrograde cardioplegia distribution

Retrograde techniques for the administration of cardioplegia solutions are of interest because of their relative practical convenience, and because of the possibility that they provide better delivery to myocardial regions jeopardized by coronary stenosis than can be achieved with traditional antegrade techniques. This study was designed to test the following three hypotheses about how the distribution of cardioplegia by retrograde techniques might be optimized: (1) venting an occluded coronary artery improves the distribution of cardioplegia to the myocardial region originally supplied by it; (2) increasing the coronary sinus perfusion pressure makes the distribution of cardioplegia through the myocardium more uniform; and (3) increasing the driving pressure, as achieved by increasing the coronary sinus perfusion pressure or occluding a left coronary artery, improves the distribution of flow to the right ventricular free wall and interventricular septum. Tracer microspheres infused retrogradely with cardioplegia solution into canine hearts in vitro showed that the distribution of flow through the coronary sinus is consistently and significantly nonuniform, and is not significantly altered by coronary arterial occlusion and venting, or by increases in coronary sinus perfusion pressure.

Lack of protection of PBN in isolated heart during ischemia and reperfusion: implications for radical scavenging mechanism

We evaluated the ability of alpha-phenyl-tert-butyl nitrone (PBN) to trap free radicals and to protect the rat myocardium during ischemia and reperfusion. Isolated bicarbonate buffer-perfused hearts (n = 8) were subjected to 20 min global ischemia (37 degrees C) followed by reperfusion with 0.4 to 4.0 mM PBN. Coronary effluent containing the PBN adduct was extracted in toluene. Electron spin resonance analysis of the toluene extract revealed a PBN-hydroxyl adduct. To verify this assignment, a Fenton system was used to generate an authentic PBN-hydroxyl adduct (n = 8), which yielded the same ESR spectra as the reperfusion-derived adduct. The structure of the adduct formed in the Fenton system was confirmed by gas chromatography-mass spectrometry. The ESR parameters of the PBN-hydroxyl adduct were exquisitely sensitive to solvent polarity during extraction of the adduct. Extraction of an authentic PBN-hydroxyl adduct into chloroform, chloroform:methanol, and toluene closely matched the ESR parameters obtained during reperfusion of ischemic myocardium in other animal models. To determine whether PBN could confer any protective effect during ischemia or reperfusion, hearts (n = 8/group) were subjected to 35 min global ischemia at 37 degrees C with the St. Thomas' II cardioplegic solution followed by 30 min reperfusion. Percent recovery (mean +/- SEM) of developed pressure, rate pressure product, and leakage of lactate dehydrogenase during reperfusion in control hearts were 58 +/- 3%, 48 +/- 4% and 3.2 +/- 0.5 IU/15 min/g wet wt. PBN at a concentration of 0.4 mM or 4.0 mM when present either during ischemia alone or reperfusion alone did not exert any effect upon recovery of developed pressure, rate pressure product or post-ischemic enzyme leakage. We conclude that PBN fails to improve contractile recovery and reduce enzyme leakage during reperfusion of myocardium subjected to global ischemia.

Coronary sinus cardioplegia: clinical trial with only retrograde approach

The cases of 100 consecutive patients who underwent coronary artery bypass grafting with coronary sinus (retrograde) cardioplegia (group R) without the antegrade-retrograde approach were reviewed. To evaluate the safety and the efficacy of this technique, another 100 consecutive patients who underwent a similar procedure but with conventional aortic root (antegrade) cardioplegia (group A) were used as a comparison. The two groups were similar with respect to age, male to female ratio, associated medical problems, extent of coronary artery disease, mean preoperative ejection fraction (0.56 +/- 0.13 versus 0.53 +/- 0.18), pump time (113.1 +/- 43 versus 111.7 +/- 38 minutes), aortic cross-clamp time (57.4 +/- 20 versus 60.8 +/- 23 minutes), number of grafts per patient, level of hypothermia, complication rate, rate of postoperative myocardial infarction (4% versus 3%), and mortality rate (2% versus 2%). Hemodynamic measurements were made 6 hours after operation in 59 patients in group R and 47 patients in group A. The cardiac index, left ventricular stroke work index, and right ventricular stroke work index were better in group R but not significantly so (p greater than 0.05). However, only 27% of patients in group R required a temporary pacemaker, and only 9% needed inotropic agents after 6 hours of operation in contrast to 51% and 42%, respectively, in group A (p less than 0.05). There were no complications from catheter intubation. In group R, right ventricular wall temperature (11 degrees +/- 3.6 degrees C) was higher than the septal (10.8 degrees +/- 3.2 degrees C) and left ventricular wall temperatures (9.1 degrees +/- 2.8 degrees C) (p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The great cardiac vein

The great cardiac vein is the longest venous vessel of the heart; in the majority of our cases it originated at the lower third of the anterior interventricular sulcus (58%). The great and the middle cardiac veins merge at the apex of the heart, forming together with the coronary sinus into which they both empty, a complete venous ring around the left ventricle (13%). On reaching the area of the coronary sulcus, the great cardiac vein crosses the anterior interventricular branch and the circumflex branch of the left coronary artery forming the triangle of Brocq and Mouchet in which the vein is mainly superficial (61%). One, two or three anterior ventricular branches of the left coronary artery traverse this triangle; the relations of the vein and these arteries are very variable and practically unpredictable in 30% of the cases.

Cardioplegia by way of the coronary sinus for valvular and coronary surgery

Retrograde coronary sinus perfusion has recently reemerged as an attractive means of delivering cardioplegic solutions during open heart procedures. In patients undergoing aortic valve or aortic root surgery, there is no evidence that coronary sinus cardioplegia results in a better myocardial protection than that achieved with the use of standard methods of anterograde cardioplegia delivery. However, the retrograde approach provides distinct technical advantages that might favor its use as an alternative to direct coronary ostial cannulation. In select subgroups of patients undergoing coronary bypass procedures, there is a growing body of evidence that the coronary sinus route may be more effective than the anterograde route because of its superior capacity to ensure homogeneous distribution of cooling and cardioplegia in myocardial areas supplied occluded arteries. The well established safety of coronary sinus cardioplegia in the clinical setting further justifies its inclusion among techniques for ensuring adequate myocardial preservation during surgically induced ischemic arrest.

Does hypothermic fibrillatory arrest improve myocardial protection during emergency revascularization?

Hypothermic fibrillatory arrest (HFA) was compared with conventional hypothermic cardioplegic arrest (HCA) in a model of acute regional ischemia. In 20 pigs, the left anterior descending coronary artery was occluded for 30 minutes before cardiopulmonary bypass. In the HCA group (n = 10), the heart was arrested with a hyperkalemic cold crystalloid solution, whereas in HFA animals (n = 10), the heart was vented and allowed to fibrillate spontaneously without cross-clamping. Miniature pH probes monitored intramyocardial pH during 45 minutes of arrest (HCA or HFA, both with systemic and topical myocardial cooling) and during two hours of coronary reperfusion. Hypothermic fibrillatory arrest did not ameliorate the acidosis in the ischemic (left anterior descending) region; indeed, after two hours of coronary reperfusion, there was a trend toward more acidosis in the postischemic left anterior descending territory in the HFA group. However, HFA did prevent acidosis in the nonischemic (left circumflex) territory. Infarct size expressed as percent of region at risk was 18.1% +/- 3.2% (mean +/- standard error of the mean) in the HCA animals and 18.8% +/- 4.4% in the HFA animals. These results demonstrate that HFA offers no advantage over HCA in protection of regionally ischemic myocardium in a model with minimal collateral circulation.

Coronary artery bypass grafting for unstable angina pectoris: risk analysis

Unstable angina pectoris is a broad, nonspecific diagnosis encompassing a wide variety of clinical syndromes. The intravenous administration of nitroglycerin preoperatively is indicative of a more acute clinical situation, and allows for selection and analysis of a more homogeneous patient population. We reviewed the results of coronary artery bypass grafting for unstable angina defined as angina necessitating intravenous administration of nitroglycerin preoperatively. There were 129 patients (83 men and 46 women) with a mean age of 63.2 years (range, 36 to 86 years). Complications included operative death in 6.2%, postoperative low cardiac output in 11%, and perioperative myocardial infarction in 9%. Twenty perioperative variables were analyzed to identify risk factors for these end points. For operative death, age (p less than 0.05), cross-clamp time (p less than 0.05), and cardiopulmonary bypass time (p less than 0.001) were significant in the univariate analysis, but only age (p less than 0.05, F = 4.6) was an independent predictor using multivariate analysis (stepwise linear regression). For low cardiac output, univariate analysis demonstrated that cross-clamp time (p less than 0.01), preoperative use of an intraaortic balloon for angina (p less than 0.05), left ventricular score (p less than 0.05), number of diseased coronary vessels (p less than 0.05), and cardiopulmonary bypass time (p less than 0.001) were significant variables. However, only use of an intraaortic balloon for angina (p less than 0.0001, F = 14.3) and left ventricular score (p less than 0.005, F = 11.1) were significant independent predictors in the multivariate model. For perioperative myocardial infarction, only diabetes requiring insulin (p less than 0.005) was a significant predictor.

Dynamic evaluation of clotting phenomena in vitro and perfluorochemical oxygen transport across a membrane-bound thrombus model

Citrated platelet-rich plasma was used to occlude 3-microns and 10-microns poresize Nuclepore membranes after recalcification as a thrombus model. Morphologic studies, using both light microscopy and scanning electron microscopy, indicated that over 90 percent of the number of pores available for filtration in hydrophilic and hydrophobic membranes were occluded either partially or completely. Results of transient and steady state pressure drop measurements supported the morphologic studies. It was found that the percentage of oxygen transported across the occluded membranes was greater for filtration of red blood cell suspensions diluted with a perfluorochemical emulsion than that of those diluted with Ringers. The findings in this study suggested that perfluorochemical emulsions might transport oxygen across a thrombus to maintain tissue viability during acute ischemic events.

Efficacy of retrograde coronary sinus cardioplegia in patients undergoing myocardial revascularization: a prospective randomized trial

The efficacy of retrograde coronary sinus cardioplegia (RCSC) administered through the right atrium compared with aortic root cardioplegia (ARC) has not been examined critically in patients undergoing coronary artery bypass grafting (CABG). Twenty patients having elective CABG were randomized prospectively to receive cold blood ARC (Group I, 10 patients) or cold blood RCSC (Group II, 10 patients). Patient demographics were similar in both groups. Ventricular function was assessed preoperatively by radionuclide ventriculography and postoperatively by simultaneous hemodynamic and radionuclide ventriculographic studies with volume loading. There was no change in ejection fraction (EF) (preoperative versus postoperative value) in Group I (50 +/- 6% versus 53 +/- 6%) but in group II, at similar peak systolic pressure and similar left ventricular end-diastolic volume index (LVEDVI), LVEF improved significantly (49 +/- 6% versus 60 +/- 12%, p less than 0.05). Postoperative ventricular function (stroke work index versus EDVI) for the left ventricle and right ventricle were similar in both groups. Evaluation of postoperative LV systolic function (end-systolic blood pressure versus end-systolic volume index) and diastolic function (pulmonary capillary wedge pressure versus EDVI) were also similar in both groups. Retrograde coronary sinus cardioplegia is as effective as ARC for intraoperative myocardial protection, and provides excellent postoperative function in patients undergoing elective CABG.

Oxygen radicals in cardiac surgery

Most cardiac surgical procedures require the use of prolonged induced myocardial ischemia. Experimental models of global myocardial ischemia which mimic cardiac surgical techniques have been developed to investigate the possibility of oxygen free radical development during prolonged myocardial ischemia or upon reperfusion. In such experiments, various free radical scavenging agents, including superoxide dismutase, catalase, and mannitol, have been shown to improve the tolerance of the heart to protracted global ischemia. Use of these agents has improved cardiac functional recovery and has attenuated the biochemical and structural changes which occur due to prolonged ischemia and reflow. In a recently developed porcine experimental model, the effects of preexisting regional myocardial ischemia with superimposed global ischemia and reperfusion have been studied, with free radical scavenging agents administered in an attempt to reduce myocardial infarction and improve regional functional recovery. In most such studies completed to date, free radical scavenging agents have resulted in better myocardial preservation, suggesting, at least indirectly, that there may be an oxygen free radical-mediated component of the ischemia-reperfusion injury seen in such models. Techniques for directly measuring myocardial oxygen free radical levels may allow for early clarification of the development of such toxic species in the clinical cardiac surgical setting.