Validation of local venous sampling within the at risk left anterior descending artery vascular bed in the canine left ventricle.

The validity of using blood sampled from the anterior interventricular vein (AIV), anatomically located within the myocardium perfused by the left anterior descending (LAD) coronary artery, to represent venous drainage originating from the LAD vascular territory was studied in eight anaesthetised, open chest dogs. The LAD was cannulated and perfused from a blood reservoir isolated from the systemic circulation. To determine the presence of blood from non-LAD sources that appears in the AIV sample, 51Cr-labelled red blood cells were injected into the left atrium and distributed in the systemic circulation while the LAD was perfused by non-radioactive blood. The percentage spillover of red blood cells from non-LAD sources into the AIV drainage was determined under control, reduced LAD flow, ischaemia, and reperfusion conditions as 100 X (AIV chromium content/arterial chromium content). Spillover of red blood cells into AIV blood samples averaged only 1.5(1.3)% under control conditions and increased insignificantly to 8.6(3.5)% during reduced LAD flow. During ischaemia red blood cells in AIV blood increased insignificantly to 98.3(5.0)% but decreased to 1.9(1.3)% after reperfusion. Studies in five dogs with microspheres showed that a portion of this admixture from non-LAD sources originated from precapillary nutritional collateral or overlapping blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal of dyskinesis by increased end diastolic segment length in ischaemic-reperfused myocardium.

Persistent dyskinesis is universally observed after reperfusion of a severely ischaemic segment. Although inotropic stimulation shows a latent contractile reserve, it is not known whether this reserve can be recruited by increasing end diastolic segment length (local length-tension relation). To investigate this, six anaesthetised open chest dogs were placed on right heart bypass to increase end diastolic segment length independently of mean arterial pressure. Instantaneous left ventricular pressure-segment length relations and fractional systolic shortening were determined by sonomicrometry in the centre of the region perfused by the left anterior descending coronary artery during sequential increases in end diastolic segment length. Measurements were made before occlusion of the left anterior descending coronary artery, during 1 h of occlusion, and after 2 h of reperfusion. Before ischaemia, segmental shortening increased from 11.0(SEM 1.6)% to 23.5(1.5)% (p less than 0.05) as end diastolic segment length increased. Dyskinesis developed during occlusion of the left anterior descending coronary artery [12.1(2.6)% control v -7.2(1.6)% occlusion, p less than 0.05] and was present over the entire range of end diastolic segment lengths. Following reperfusion, segmental dyskinesis [-2.5(2.4)%] persisted at the lower end of the range of end diastolic segment length, but was progressively replaced by active shortening, averaging 7.3(3.2)% (p less than 0.05) as end diastolic segment length was sequentially increased. We conclude that segmental function following reperfusion is sensitive to changes in end diastolic segment length, and that active shortening is recruited from an apparently dyskinetic segment as end diastolic segment length progressively increases.

Cardiac transplantation in a patient with muscular dystrophy and cardiomyopathy.

A 17-year-old boy with muscular dystrophy developed a cardiomyopathy. His brother died of a cardiomyopathy, and muscle enzyme levels were elevated in asymptomatic family members. Examination revealed cardiomegaly, hepatomegaly, proximal muscle atrophy and weakness, and calf hypertrophy. Skeletal muscle and endomyocardial biopsy specimens were consistent with Becker's muscular dystrophy. Because of intractable heart failure, orthotopic cardiac transplantation was performed. Two years after transplantation, the patient has returned to work and regained previous exercise tolerance. Heart transplantation can be an acceptable treatment of patients who have muscular dystrophy, with preserved ambulation and favorable life expectancy, and also life-threatening cardiomyopathy refractory to medical management.

Transient ischemic attacks: a prospective study of 225 patients.

Between the years 1964 and 1973, 225 patients with transient ischemic attacks (TIAs) due primarily to atherosclerosis were evaluated and treated. They have now been followed for from 3 to 14 years (average 5.5 years). As of 1976, 82 of the 225 patients were dead, 21 from cerebral infarction, 52 from heart disease and nine from other causes. Of the 56 untreated patients, 11 (19 percent) had cerebral infarctions, four (7 percent) of which were fatal; six (11 percent) were still having TIAs. Of the 45 patients medically treated, 10 (24 percent) had cerebral infarctions, three (7 percent) of which were fatal; 11(25 percent) still experienced TIAs. In the surgical group of 124, 27 (21 percent) had postoperative cerebral infarctions, seven (6 percent) of which were fatal; 23 (18 percent) had cerebral infarctions during follow-up, of which seven (6 percent) were fatal; and 15 (12 percent) were still having TIAs. No statistically significant differences (p less than 0.05) related to cerebral infarction or TIAs developed among the three groups. The majority (23 percent) eventually succumbed to myocardial infarction, leading us to conclude that great emphasis must be placed upon TIAs as a warning for cardiac as well as cerebrovascular disease.

Reperfusion injury after temporary coronary occlusion.

In 24 anesthetized open-chest dogs, we examined the time course of changes in contractile function, diastolic muscle stiffness (sonomicrometry), tissue water content, and ultrastructure after 1 hour of occlusion of the left anterior descending coronary artery and after 2 hours of unmodified reperfusion. One hour of occlusion of the left anterior descending artery replaced active shortening with passive bulging (21.4% +/- 2.9% versus -5.9% +/- 0.9%, p less than 0.05) in the involved segment. There was no increase in either subendocardial water content (78.6% +/- 0.1% versus 79.7% +/- 0.7%) or operative muscle stiffness (2.80 +/- 0.72 versus 2.36 +/- 0.42 mm Hg/mm) after the occlusion period. There were only mild to moderate ultrastructural alterations suggestive of reversible injury. In sharp contrast, reperfusion was associated with a 2.48% increase in subendocardial water content (p less than 0.05), a 42% increase in diastolic muscle stiffness (3.34 +/- 0.42 mm Hg/mm, p less than 0.05), and greater ultrastructural damage. We conclude that myocardial injury is significantly extended with unmodified blood reperfusion after temporary coronary occlusion.

Cerebrovascular and cerebral metabolic effects of alterations in perfusion flow rate during hypothermic cardiopulmonary bypass in man.

Recent experimental and clinical investigations provide conflicting evidence regarding the effects of changes in the systemic flow rate from the pump oxygenator on cerebral blood flow and the cerebral metabolic rate of oxygen consumption. However, the results of existing clinical studies are difficult to interpret because of the confounding effects of differences in management of arterial carbon dioxide tension and use of anesthetic and vasoactive agents during cardiopulmonary bypass. To clarify the relationship among perfusion flow rate, cerebral blood flow, and cerebral metabolic rate of oxygen consumption in man during hypothermic cardiopulmonary bypass, we varied perfusion flow rate in random order to either 1.75 or 2.25 L.min-1.m-2 and studied cerebral blood flow (measured by clearance of xenon 133) and cerebral metabolic rate of oxygen consumption (estimated as the product of cerebral blood flow and the cerebral arteriovenous oxygen content difference) in patients managed with both the alpha-stat (group 1) and the pH-stat (group 2) methods of pH and arterial carbon dioxide tension adjustment. We measured the cerebral arteriovenous oxygen content difference using radial arterial and jugular venous bulb blood samples. In each patient other variables known to exert effects on cerebral blood flow and cerebral metabolic rate of oxygen consumption, including temperature, arterial carbon dioxide tension, arterial oxygen tension, mean arterial pressure, and hematocrit, were maintained constant between measurements. In both groups, mean arterial pressure at both pump flow rates was similar because of spontaneous reciprocal alterations in systemic vascular resistance, that is, as perfusion flow rate declined, systemic vascular resistance increased; as perfusion flow rate increased, systemic vascular resistance declined. Under these tightly controlled conditions, pump flow variation per se exerted no effect on cerebral blood flow or cerebral metabolic rate of oxygen consumption in either group.

Is a left ventricular vent necessary for coronary artery bypass operations performed with cardioplegic arrest?

The need for ventricular venting with hypothermic cardioplegic arrest is controversial. We report an evaluation of the need for left ventricular venting in a canine model that closely simulates conditions during routine coronary artery bypass grafting (CABG). Thirty-five dogs were placed on cardiopulmonary bypass for 60 minutes of hypothermic cardioplegic arrest (18 vented, 17 nonvented) and then reperfused for 30 minutes. Myocardial temperature and left atrial pressure (LAP) were recorded continuously. Before and 30 minutes after hypothermic cardioplegic arrest, left ventricular function curves were generated (six vented, six nonvented), and biopsy specimens of the left ventricle were taken for adenosine triphosphate (ATP) determinations (11 vented, 10 nonvented) and semiquantitative grading of mitochondrial ultrastructure (six vented, six nonvented). LAP in nonvented dogs was 7.4 mm Hg during hypothermic cardioplegic arrest and 5.0 mm Hg during reperfusion. Temperature during hypothermic cardioplegic arrest was 12.3 degrees C in vented dogs and 11.3 degrees C in nonvented dogs (p = 0.5). There were no differences in left ventricular function or preservation of mitochondrial ultrastructure between vented and nonvented dogs. ATP after hypothermic cardioplegic arrest was 96.6% of control (4.30 microM/gm) in vented dogs and 94.6% (4.37 microM/gm) in nonvented dogs (p = 0.7). The absence of left ventricular venting did not lead to ventricular distention or more rapid rewarming. These data in vented dogs and nonvented dogs strongly support the belief that left ventricular venting is not necessary during routine CABG.

Clinical spectrum of blunt tracheobronchial disruption illustrated by seven cases.

Tracheobronchial disruption resulting from blunt trauma is unusual, but when it does occur it can have serious immediate and delayed consequences. A high index of suspicion for this injury and an awareness of the variety of clinical, radiographic, and bronchoscopic presentations are the key elements in diagnosis. Our experience with seven patients with blunt tracheobronchial trauma seen from 1972 through 1980 is reviewed. Emphasis is placed on the importance of early diagnosis to avoid the complications associated with delayed repair.

Malignant fibrous histiocytoma of the mediastinum and lung: a report of three cases.

One case of primary malignant fibrous histiocytoma of the lung and two cases of that tumor in the mediastinum are reported. Primary malignant fibrous histiocytoma is rare in those areas, appearing more commonly in deep fascia and skeletal muscles of the extremities and torso and in the retroperitoneum. Most of the tumors contain both fibroblast-like and histiocyte-like cells; some contain pleomorphic giant cells and inflammatory cells. They are often confused with other sarcomas, and their true biologic potential is not clearly defined. Radiation appears to be a very useful adjunct to surgical therapy and was used in the cases reported here.

Adjuvant N-(2-mercaptopropionyl)-glycine in blood cardioplegia does not improve myocardial protection in ischemically damaged hearts.

Oxyradicals potentially limit the myocardial protection provided by blood cardioplegia in ischemically damaged hearts. We tested the hypothesis that the addition to blood cardioplegic solution of a new oxyradical scavenger--N-(2-mercaptopropionyl)-glycine--would result in improved left ventricular performance and oxygen consumption compared to that resulting from the use of blood cardioplegia alone. Gauges and transducer-tipped catheters for left ventricular minor axis ultrasonic dimension were placed in 17 open-chest dogs, and instantaneous left ventricular pressure-diameter data were acquired by computer. The aorta was crossclamped for 30 minutes during total vented bypass to induce ischemic injury. The heart was reoxygenated and protected by multidose, hypothermic blood cardioplegic solution alone (n = 9) or enhanced with 0.0132 mmol N-(2-mercaptopropionyl)-glycine (n = 8) for 1 hour of cardioplegia-induced arrest. Preischemic and postischemic left ventricular performance was measured by slope changes in end-systolic pressure-diameter relations induced by gradual afterload reduction during right heart bypass. When blood cardioplegia alone was used, postischemic left ventricular systolic performance was depressed by 73.2% +/- 10.0% (166.8 +/- 56.1 mm Hg/mm versus 25.1 +/- 7.0 mm Hg/mm). N-(2-mercaptopropionyl)-glycine did not significantly attenuate this functional depression (62.7% +/- 9.0%, 146.6 +/- 67.6 mm Hg/mm versus 33.6 +/- 11.9 mm Hg/mm). The postischemic end-diastolic pressure-diameter relation was shifted to the right, whereas chamber stiffness was increased comparably, with or without N-(2-mercaptopropionyl)-glycine. Postischemic oxygen consumption in the beating working state, calculated from left ventricular blood flow (measured by microspheres) and arterial-coronary sinus oxygen extraction, averaged 7.8 +/- 0.9 ml O2/100 gm/min with blood cardioplegia alone and 7.5 +/- 1.0 ml O2/100 gm/min with N-(2-mercaptopropionyl)-glycine, and was unchanged from paired preischemic values in both groups. We conclude (1) that N-(2-mercaptopropionyl)-glycine added to blood cardioplegic solution in the dose and delivery regimen tested did not improve ventricular systolic and diastolic performance compared with blood cardioplegia alone and (2) that postischemic oxygen consumption may not parallel the extent of left ventricular functional recovery.

Coronary revascularization in patients with bilateral internal carotid occlusions.

Coronary revascularization that is neurologically uneventful in patients with bilateral totally occluded internal carotid arteries has not been previously reported. We performed saphenous vein coronary artery bypass grafting on three such patients and observed them for 6 to 23 months. Preoperatively two of our patients had chronic stable symptoms of cerebrovascular insufficiency, and one had received cerebral revascularization via a superficial temporal-to-middle cerebral artery bypass. Controversy exists regarding proper cerebral protective maneuvers during coronary revascularization for patients with advanced cerebrovascular disease. Cerebral protection for our patients during cardiopulmonary bypass included hypothermia and high perfusion flows and pressures. Two patients also received prophylactic sodium thiopental. None of these three patients had a stroke perioperatively or during the follow-up period. We believe that these case histories strongly suggest that the functional state of the cerebral collateral circulation, as judged by preoperative neurological symptoms, predicts neurological outcome after coronary revascularization better than the specific occlusive anatomy of the extracranial carotid arteries.

Heparin dosing and monitoring for cardiopulmonary bypass. A comparison of techniques with measurement of subclinical plasma coagulation.

Subclinical plasma coagulation during cardiopulmonary bypass has been associated with marked platelet and clotting factor consumption in monkeys. To better define subclinical coagulation in man, we measured plasma fibrinopeptide A concentrations before, during, and after cardiopulmonary bypass. Patients were assigned to one of three groups of heparin management: group 1 (n = 10)--initial heparin dose 300 IU/kg, with supplemental heparin if the activated coagulation time fell below 400 seconds; group 2 (n = 6)--initial heparin dose 250 IU/kg, with supplemental heparin if activated coagulation time was less than 400 seconds; and group 3 (n = 5)--initial heparin dose 350 to 400 IU/kg, with supplemental heparin if whole blood heparin concentration was less than or equal to 4.1 IU/ml. Activated coagulation time and heparin concentration were measured every 30 minutes during cardiopulmonary bypass, and fibrinopeptide A was measured at hypothermia, normothermia, and whenever activated coagulation time was less than 400 seconds. Quantitative and qualitative blood clotting competence was assessed after cardiopulmonary bypass, including mediastinal drainage for the first 24 hours. Fibrinopeptide A values were markedly elevated during cardiopulmonary bypass but were well below the levels present before and after cardiopulmonary bypass. Fibrinopeptide A correlated inversely with heparin concentration during cardiopulmonary bypass (r = -0.46, p = 0.03), but higher fibrinopeptide A levels during cardiopulmonary bypass did not correlate with post-cardiopulmonary bypass coagulopathy. Group 3 patients received the highest heparin doses (p less than 0.05) and had the greatest postoperative blood loss (p less than 0.05). Protamine dose and heparin concentration during cardiopulmonary bypass correlated best with postoperative mediastinal drainage. Our findings support the following conclusions: (1) compensated subclinical plasma coagulation activity occurs during cardiopulmonary bypass despite activated coagulation time greater than 400 seconds or heparin concentration greater than or equal to 4.1 IU/ml; (2) post-cardiopulmonary bypass mediastinal drainage correlates strongly with increased heparin concentration during cardiopulmonary bypass (p less than 0.05) and protamine dose (p less than 0.05); and (3) during cardiopulmonary bypass at both normothermia and hypothermia, activated coagulation times greater than 350 seconds result in acceptable fibrinopeptide A levels and post-cardiopulmonary bypass blood clotting.

Inhibition of platelet deposition on polytetrafluoroethylene grafts by antiplatelet agents.

The effects of ibuprofen (Motrin), dipyridamole (Persantine), and prostacyclin on the deposition of platelets on polytetrafluoroethylene grafts (5.5 cm long, 4 mm internal diameter implanted into both femoral arteries of 21 dogs) were studied by harvesting autologous platelets, labeling them with 51Cr, and reinjecting them 15 minutes before cross-clamping. Arterial flow was adjusted to 65 ml/min and monitored continuously. Ibuprofen (12.5 mg/kg) and dipyridamole (2.5 mg/kg) were each administered as a single intravenous injection in four dogs (eight grafts) and five dogs (10 grafts), respectively. Prostacyclin (50 ng/kg/min) was administered by continuous intravenous infusion in five dogs (10 grafts). Seven dogs (14 grafts) served as controls. Grafts were removed 2 hours after implantation, and radioactivity (counts per 10 minutes) was determined in four segments of each graft (including both anastomoses) with a gamma-counter. Counts were averaged for each group of dogs. Significance was calculated by the Student t test. Platelet deposition in control dogs averaged 10,033.9 +/- 1134.2 SE; that in prostacyclin-treated dogs averaged 2513.7 +/- 276 SE (p less than 0.001); that in ibuprofen-treated dogs averaged 5453.4 +/- 1336.3 SE (p = 0.02); that in dipyridamole-treated dogs averaged 11,213.7 +/- 1632.5 SE (p = 0.55). These data demonstrate the effectiveness of prostacyclin and ibuprofen in reducing platelet deposition on polytetrafluorethylene grafts in dogs.

Milestones in the development of cardioplegia.

Long before there was a possibility for the application of cardioplegia to clinical situations, physiologists and surgeons studied the influence of various cations on function of the myocardial cell. These monumental studies helped set the stage for the eventual practical application of various means of myocardial preservation once open cardiac surgical techniques became available. This presentation attempts to summarize early research effort from the work of Sidney Ringer in 1878 until the present time. The historical progression of myocardial protective strategies is reviewed in a sequential fashion, highlighting major contributions and practices of investigators at the time. It is hoped that such a review of the accomplishments of our colleagues past and present will improve our perspective regarding current applications of such knowledge and that it may stimulate further inquiry toward improving present-day myocardial preservation strategies.

An appraisal of blood salvage techniques in vascular and cardiac operations.

This study compares blood salvage and reinfusion with the use of homologous blood in three groups of patients undergoing coronary artery bypass graft replacement or other cardiac operation. In Group 1 (100 patients), homologous blood was used and no effort was made to salvage blood. In Group 2 (68 patients), blood was salvaged before and after bypass and mediastinal blood was salvaged for 24 hours postoperatively. In Group 3 (46 patients), blood was salvaged before and after bypass and postoperatively. The average patient in Groups 2 and 3 required approximately one-third the amount of whole blood and approximately one-fourth the amount of packed red blood cells (RBC) required by a Group 1 patient. The hospital stays, blood chemistry levels, and costs per patient were comparable for the three groups. RBC survival studies in Group 3 patients showed a mild decrease from normal values. This study shows that currently available equipment and techniques allow safe and practical blood salvage during cardiac and vascular operations.

Seminoma of the anterior mediastinum.

Primary pure cell seminoma of the mediastinum is a rare and potentially fatal lesion. Encroachment on or invasion of adjacent structures is common, as are distant metastases. The differentiation between pure cell seminomas and mixed germ cell tumors should be made since the extreme radiosensitivity of seminomas improves the prognosis. The presence of metastases from primary mediastinal seminomas, as with testicular germinomas, need not be a deterrent to long-term cure. Recommended therapy consists of total or subtotal removal, radiation therapy (2,500 to 3,500 rads delivered over 2 to 4 weeks), and, in some patients, chemotherapy. A patient who was successfully treated with subtotal removal and irradiation is presented.

Delayed left ventricular rupture secondary to transatrial left ventricular vent.

The cases of 2 patients with delayed ventricular rupture secondary to ventricular venting through the left atrium during myocardial revascularization are reported. Both patients were weaned from cardiopulmonary bypass without difficulty and were transported to the intensive care unit in good condition. Rupture occurred in one patient two hours later and in the other, approximately twelve hours postoperatively; both patients died. Both patients were short in stature, and it is possible that advancing the catheter to the first guide mark left the tip unusually close to the ventricular apex. As the catheter cooled and hardened and as the heart was retracted, the catheter may have been pushed against the apical endocardium, thereby producing undetectable subendocardial damage. Our experience with these 2 patients has led us to become more selective in venting for coronary bypass operations. When venting is necessary, we insert the catheter so that its tip barely enters the ventricle.

Successful operative management of struma cordis obstructing the left ventricular outflow tract.

Struma cordis, ectopic thyroid tissue located in the heart, is extremely rare. To our knowledge, this is the first report of struma cordis obstructing the left ventricular outflow tract. The tumor was removed successfully using cardiopulmonary bypass.

Stentless aortic valve replacement with Freestyle or Toronto SPV: an early comparison.

BACKGROUND: Stentless aortic xenograft valves have been developed to overcome the disadvantages of conventional stented prostheses. We have implanted two new aortic bioprostheses: the Medtronic Freestyle and the St. Jude Toronto SPV. Early results are compared. METHODS: Forty-four Freestyle valves were implanted using a freestanding total root technique. Fourteen subcoronary Toronto SPV bioprostheses were implanted. Sixty-four percent of both groups (28 of 44 Freestyle and 9 of 14 Toronto SPV) underwent concurrent procedures. RESULTS: Ischemic time was 117 +/- 21 minutes for Freestyle and 124 +/- 19 minutes for Toronto SPV. There were no operative deaths or valve-related reoperations. Aortic valve area was 1.83 +/- 0.51 cm2 for Freestyle and 1.80 +/- 0.51 cm2 (p = 0.89) for Toronto SPV. Transvalvular gradient was 8.03 +/- 4.09 mm Hg for Freestyle and 12.4 +/- 1.82 mm Hg (p = 0.002) for the Toronto SPV. Aortic regurgitation was not experienced in any Freestyle patients, while Toronto SPV patients were graded as none to trace 79% (11 of 14), mild 14% (2 of 14), and moderate 7% (1 of 14). CONCLUSIONS: Aortic valve replacement with the Freestyle and Toronto SPV required equal time for implantation and had equal effective orifice areas. Freestyle had lower transvalvular gradient and less aortic insufficiency without increasing morbidity or mortality.

Mitral valve operation via an extended transseptal approach.

The extended transseptal approach to the mitral valve has been used for 71 consecutive procedures. Four patients died; none had complications directly attributable to the exposure. Twenty underwent a primary reparative procedure; 30, a primary replacement procedure; and 21, a repeat procedure. Despite division of the sinus node artery, 26 of 32 patients with sinus rhythm preoperatively had sinus rhythm postoperatively; 4 had atrial fibrillation postoperatively. Twenty-seven of 37 patients with atrial fibrillation preoperatively had atrial fibrillation postoperatively; 8 had sinus rhythm postoperatively. Because the exposure provided by this extended transseptal approach is superior to that of standard approaches, we now use it routinely for mitral valve operations.