Reperfusion before Global Ischemic Arrest Improves the Salvage of Infarcting Myocardium

To study the effect of hypothermic global ischemic arrest on an evolving myocardial infarction and of perfusion of the ischemic zone or region at risk before global ischemia, 62 farm pigs underwent 15, 30, or 60 minutes of reversible coronary occlusion. Twenty-eight of these animals served as controls: reflow to the region at risk was established by removal of the coronary occluder without the addition of global ischemia. Another 26 animals had similar periods of coronary occlusion and then were placed on cardiopulmonary bypass; they underwent aortic cross-clamping and cardioplegia-induced global hypothermic arrest for 45 minutes. Eight additional pigs had two hours of reflow to the region at risk after removal of the occluder and before global ischemic arrest. When superimposed on regional ischemia, global ischemia resulted in a 6-fold increase in infarct size after 15 minutes of coronary occlusion (p < 0.05), a 2.2-fold increase after 30 minutes of coronary occlusion (p < 0.05), and no significant increase after 60 minutes of coronary occlusion. Reperfusion prior to global ischemia completely prevented infarct extension with 0.4% less infarction (not significant) in this group versus the controls without global ischemia.These results clearly demonstrate that infarct extension occurring when global ischemia is superimposed on regional ischemia is greatest early in infarct evolution but that reflow to the region at risk before global ischemic arrest prevents the additional infarction. These data suggest that ischemic myocardium must be supplied with oxygen and metabolic substrate prior to global ischemic arrest to obtain maximum myocardial salvage with surgical revascularization.     

Improved myocardial performance in postoperative cardiac surgical patients with sodium nitroprusside

Myocardial performance in the immediate postoperative period was studied 49 cardiac surgical patients treated with nitroprusside alone. With a thermodilution catheter positioned in the pulmonary artery, cardiac output was calculated and cardiac index, systemic vascular resistance index, and stroke work index were derived before after treatment with nitroprusside. The drug was a administered to all patients because of elevated systemic vascular resistance index. Based on their mean arterial pressure and cardiac index before treatment, the patients fell into two groups. Group I patients (N = 25) had elevated mean arterial pressure and normal cardiac index. Group II patients (N = 24) had normal mean arterial pressure and subnormal cardiac index. Nitroprusside administration resulted in a significant reduction of systemic vascular resistance index in all patients. In Group I the mean arterial pressure was lowered significantly while cardiac index increased only slightly. In Group II there was no change in arterial pressure, but cardiac index improved significantly. The results not only confirm that nitroprusside is effective in managing postoperative hypertension, but also demonstrate that in patients with postoperative left ventricular failure, the drug can improve cardiac output by reducing systemic vascular resistance without significantly lowering arterial blood pressure.     

Operative intervention for postinfarction angina

Thirty-four patients (26 men and 8 women) underwent myocardial revascularization following myocardial infarction (MI) at the Johns Hopkins Hospital during 1980 through 1982. Average age was 59 years. Of the 33 patients with unstable angina, 61% had ischemia in the infarct zone and 39% had "ischemia at a distance." Mean time from MI to operation was 16 days. The MIs were equally divided between a transmural and a subendocardial location. Eleven patients had a history of congestive heart failure. Intraaortic balloon pumping was used preoperatively for anginal stabilization in 14 patients. Mean ejection fraction for the group was 52%. There were 3 operative deaths, all 3 due to myocardial failure. Late follow-up (mean, 13.7 months; range, 6 to 35 months) is complete for 28 patients. There was 1 late death, secondary to cardiac failure. There were no late MIs. Angina had recurred in 5 patients, but only 2 were taking antianginal medication. At the time of follow-up, 52% of patients were in New York Heart Association Functional Class I. This experience suggests that operative intervention for postinfarction angina can be accomplished with an acceptable mortality and thereby increase survival, reduce the later occurrence of MI, and relieve angina in this high-risk group.     

The effect of cardiopulmonary bypass perfusion pressure on myocardial gas tensions in the presence of coronary stenosis.

Mass spectrometry was utilized to determine myocardial gas tensions in dogs subjected to cardiopulmonary bypass. Myocardial ischemia occurred in animals with normal coronary arteries when cardiopulmonary bypass perfusion pressure fell 40 to 60 mm Hg below the mean aortic pressure measured prior to bypass. Myocardial ischemia did not occur, or could be eliminated when present, if cardiopulmonary bypass perfusion pressure was maintained near prebypass mean aortic pressure. In animals with constricted circumflex coronary arteries, the adverse effect of low perfusion pressure on myocardial metabolism during cardiopulmonary bypass was found to be more severe in areas of myocardium supplied by the stenotic coronary artery. It is concluded that maintenance of cardiopulmonary bypass perfusion pressure near the level of preoperative mean aortic pressure will help prevent myocardial ischemia during operation; particularly in patients with coronary artery disease.     

The Harmful Effects of Ventricular Distention during Postischemic Reperfusion

To assess the effects of left ventricular distention during the early reperfusion period following ischemic arrest, 16 canine heart preparations were subjected to 45 minutes of hypothermic (27°C) cardioplegic arrest and normothermic reperfusion. Isovolumic left ventricular developed pressure and rate of rise of left ventricular pressure (dP/dt) were measured with an intraventricular balloon; endocardial/epicardial flow ratios were determined with microspheres; and myocardial gas tensions were monitored with mass spectrometry.During early reperfusion, Group 1 hearts (n = 8) were not distended (end-diastolic pressure = 0). Group 2 hearts (n = 8) were subjected to an end-diastolic pressure of 20 mm Hg for the initial 15 minutes of reperfusion. Group 2 hearts demonstrated impaired subendocardial blood flow after 5 minutes of reflow (0.75 ± 0.06 vs 0.96 ± 0.04, endocardial/epicardial flow rates, Group 2 vs Group 1) and persistent elevation of intramyocardial carbon dioxide (CO₂) tension (68 ± 4 vs 51 ± 4 mm Hg, Group 2 vs Group 1). In addition, postischemic ventricular function was significantly worse in Group 2 hearts (60 ± 7 vs 79 ± 3% of control dP/dt, Group 2 vs Group 1, and 53 ± 6 vs 81 ± 5% of control left ventricular developed pressure, Group 2 vs Group 1).These data demonstrate that even mild distention during early reperfusion can result in reduced subendocardial perfusion and delayed washout of tissue CO₂. Although myocardial blood flow and CO₂ tension subsequently returned to normal in the distended hearts, left ventricular performance remained significantly depressed. This injury can occur clinically in nonvented hearts prior to the resumption of effective ventricular contraction.     

Systemic-Pulmonary Shunts in Neonates and Infants Using Microporous Expanded Polytetrafluoroethylene: Immediate and Late Results

Thirty infants with various types of cyanotic congenital heart disease underwent systemic-pulmonary artery shunts with a microporous polytetrafluoroethylene (PTFE) graft between May, 1976, and July, 1979. Sixteen of them were less than 1 month old, and the average age of the neonates was 5.3 days. There were no operative deaths and 5 hospital deaths, 2 related directly to the shunt. Five patients required early revision of the shunt. Relief from cyanosis was achieved in each patient. Twenty-five patients have been followed up to three and one-half years. There have been 2 late deaths and one late occlusion of the shunt. One patient outgrew the shunt and required secondary shunting procedures. Three of 30 patients have evidenced mild congestive heart failure, which has responded to digitalis. Because of the reliability and excellent late patency of the PTFE prosthesis, we consider it to be superior to a central or Potts shunt for relief from cyanosis in the neonate and infant, and as reliable as a Blalock-Taussig shunt.     

Factors influencing survival following postinfarction ventricular septal defects.

Postinfarction ventricular septal defect (VSD) carries a grave prognosis. Surgical closure appears to improve survival. Eighteen patients with postinfarction VSD are reviewed. Nine died before operation could be performed and 9 underwent closure of the VSD; 4 patients are late survivors. Factors which appear to influence survival are: (1) time of surgical intervention after appearance of VSD, (2) presence or absence of cardiogenic shock, (3) location of the infarct, and (4) operative approach to the VSD. Based on these factors, a method of management for postinfarction VSD is outlined.     

Acute physiological changes following heart-lung allotransplantation in dogs

The feasibility of clinical heart-lung transplantation requires a better understanding of the physiological consequences of the operation, heart-lung denervation, and the quality of graft preservation. An acute canine model was used to evaluate heart-lung function during the first 24 hours after transplantation. Measurements of cardiopulmonary dynamics were performed in 5 donor animals and compared sequentially after transplantation in the respective recipients. Orthotopic allotransplantation was performed on cardiopulmonary bypass with moderate hypothermia after perfusion of both the heart and lung with a clinical cardioplegic solution (4 degrees C; potassium chloride, 30 mEq/L; mannitol, 20 gm/L). Postoperatively, the animals were ventilated continuously and anesthetized. Hemodynamic variables were monitored, and measurements were made of arterial and venous oxygen, carbon dioxide, saturation, and pulmonary mechanics. Cardiac output and a derived measurement of lung water were determined. Pulmonary vascular resistance, arteriovenous shunt, resistance, and compliance were calculated. At the termination of the experiment, significant differences were observed between donor and recipient lung-water levels (7.7 +/- 0.9 ml/kg versus 12.0 +/- 3.1 ml/kg, respectively; p less than 0.05); 100% arterial oxygen tension (509 +/- 37 mm/Hg versus 227 +/- 114 mm/Hg, respectively; p less than 0.01); and pulmonary compliance (38 +/- 18 ml/cm H2O versus 11 +/- 4 ml/cm H2O, respectively; p less than 0.05). Arteriovenous shunt increased from 12.2 +/- 4 to 16.5 +/- 5% (p = 0.2). This model evaluates the technique currently employed clinically and will be used in the future to compare methods of heart-lung preservation with the goal of allowing distant heart-lung procurement.     

Permanent Cardiac Pacemakers in Children: Technical Considerations

Placement of permanent cardiac pacemakers in children presents technical problems that are not encountered in the adult. Problems unique to pacemaker implantation in children are related to the patient's size, the relative bulkiness of pulse generators, the lack of subcutaneous tissue, and the child's growth and long life expectancy. Based on our experience with implantation of 27 permanent cardiac pacemakers in 13 children, we have found that the use of small pulse generators, placement of epicardial leads, insertion of properitoneal pulse generators, and use of rechargeable pacemakers are satisfactory methods in children.     

The Heparin-coated Vascular Shunt for Thoracic Aortic and Great Vessel Procedures: A Ten-Year Experience

From 1966 to 1976 a flexible, heparin-coated shunt was used for operative procedures on the thoracic aorta and great vessels in 25 patients aged 15 to 78 years. Twenty patients had resection of aneurysms of the descending thoracic aorta. There was 1 death in 15 patients undergoing elective resection and 2 deaths (both from rupturing aneurysms) in 5 patients having emergency resection. The shunt was used in 5 patients who had procedures involving the great vessels.There have been no complications attributable to the shunt in either group. The advantages of this shunt include elimination of the need for systemic heparin, avoidance of hypertension during cross-clamping, and adequate perfusion of the distal circulation without an interposed pump. Because of the ease of handling, low risk, and versatility, we consider the use of this shunt the preferred method for support in elective procedures of the thoracic aorta and great vessels.     

Surgical management of lung bud anomalies: lobar emphysema, bronchogenic cyst, cystic adenomatoid malformation, and intralobar pulmonary sequestration.

Recently we saw 9 infants with life-threatening respiratory distress. Four patients had bronchogenic cyst, 2 had cystic adenomatoid malformation, and 9 had congenital lobar emphysema. Another group of 14 older children had recurrent infection and hemodynamic abnormalities, which responded to operative intervention. Each child required an appropriate resection following definitive diagnosis. These lesions represent a spectrum of closely related anomalies that arise during an early stage of embryonic lung bud maturation. Bronchoscopy is rarely useful, but special roentgenographic studies, including perfusion scans and arteriography, are usually diagnostic. Our operative experience is used to emphasize the urgency of precise diagnosis and surgical management of this poorly recognized clinical syndrome.     

A Simple Model of the Hemodynamic Effects of a Proximal Coronary Artery Narrowing

A simple mathematical model of the hemodynamic effects of a discrete proximal coronary artery obstruction is presented. The model demonstrates that resting myocardial flow demands fail to be met when the vessel diameter is decreased by 75% or greater. More strikingly, it shows that the maximum flow obtainable for increased myocardial oxygen demand begins to fall significantly with a lesion causing a 40 to 50% obstruction. The implications of these findings in relation to stress-induced angina are discussed.     

Selective nonoperative management of contained intrathoracic esophageal disruptions.

Eight patients with intrathoracic esophageal disruptions were managed nonoperatively and without pleural drainage. Criteria for nonoperative treatment included the following: disruption contained in the mediastinum or between the mediastinum and visceral lung pleura; drainage of the cavity back into the esophagus; minimal symptoms; and minimal signs of clinical sepsis. Cause of the esophageal perforation was pneumostatic dilatation (1 patient), vomiting (2), and a leak following esophageal operation (5). Antibiotics were administered intravenously to all patients; hyperalimentation was accomplished intravenously in 5, and nasogastric suction was used in only 1. The cavities contracted and the esophageal leaks sealed in all instances. Time before oral intake was resumed ranged from 7 to 38 days (average, 18 days). Days until discharge ranged from 15 to 52 days (average, 28 days).     

Routine use of autotransfusion following cardiac surgery: experience in 700 patients.

An autotransfusion technique has been developed for collection and reinfusion of shed mediastinal blood. This system has been routinely applied in the postoperative management of 592 consecutive adult and 108 pediatric cardiac surgical patients. Two hundred seventy-one adult patients (46%) and thirty-six pediatric patients (33%) actually received autologous blood. Autotransfusion volume ranged from 50 to 21,350 ml per patient. In 1976 at our institution, homologous transfusion requirements averaged 8.4 +/- 0.7 units per adult patient. During 1978, with the routine use of postoperative autotransfusion, bank blood transfusions were lowered to 4.2 +/- 0.3 units per patient (p less than 0.001). In contrast to perioperative autotransfusion techniques, collection and reinfusion of shed mediastinal blood is particularly useful for intravascular volume replacement in patients with serious postoperative bleeding.     

A New Instrument for Measurements in Cardiovascular Surgery

An instrument for performing measurements in cardiac and vascular operations is described. This device is a modification of a vascular clamp that provides an accurate and simple method for making intracardiac measurements. The instrument is constructed to provide easy readout of even extremely small measurements.     

Surgical management of congenital pulmonary valve dysplasia.

Pulmonary valvular stenosis secondary to congenital valve dysplasia differs markedly from the classic variety of pulmonary stenosis. The reported mortality of patients treated by standard commissurotomy is 38 to 66%. The clinical features and operative management of 14 patients with dysplastic pulmonary valves are reviewed. Three groups of patients were studied. Group 1 consisted of 5 patients treated by commissurotomy. Group 2 comprised 3 patients treated by partial excision of the valve. In neither group were there operative deaths, but 5 of the 8 patients developed recurrent stenosis; 3 required reoperation. In 1975, because of the high incidence of recurrent stenosis, total valvectomy was begun. Ten patients (Group 3) have undergone valvectomy with 1 death. Nine patients were doing well at 3 to 15 months of follow-up. Based on the reported mortality and present findings, total excision of the valve is recommended for relief of stenosis in pulmonary valve dysplasia.     

Cardiovascular and Respiratory Manifestations of Pulmonary Sequestration in Childhood

Intralobar pulmonary sequestration was diagnosed in 14 patients, 12 of whom were under 10 years of age, including 2 infants aged 2 weeks. Half of the patients had respiratory problems when first seen. “Classic” purulent bronchiectatic disease was present in only 2; 5 had mild pneumonitis, asthma, or bronchitis. A second group had cardiovascular problems. Two children had severe congenital heart disease, and 4 had significant arteriovenous shunts in the sequestration, including an infant with cardiac failure. All the shunts were characterized by a continuous murmur in the back or axilla on the affected side. Early operation can prevent more severe respiratory problems and obviate the hemodynamic sequelae of the A-V fistula. Segmental resection of the sequestration was performed in 2 children, which suggests that lobectomy may not always be necessary.     

Mediastinal infection after cardiac surgery

Mediastinitis is an uncommon complication after cardiac surgery; however, its associated morbidity and mortality demand early recognition and emergency therapy. This review is intended to emphasize certain features of the incidence, pathogenesis, and bacteriology of this complication in patients undergoing cardiopulmonary bypass through a median sternotomy. The diagnosis and treatment of mediastinitis after cardiac surgical procedures, as well as methods of prevention, are also reviewed.     

Late false aneurysm following replacement of ascending aorta: the problem of the teflon graft in combination with a silk suture anastomosis

Two patients underwent resection and replacement of the ascending aorta using a low-porosity Teflon graft anastomosed with silk suture. In both patients false aneurysms developed that required operation 13 and 23 years postoperatively. The clinical courses of these patients, along with data from the literature, suggest that the combination of a low-porosity Teflon graft and a silk suture anastomosis presents a major potential hazard for the development of anastomotic false aneurysm.     

Hemodynamic determinations in the assessment of distal coronary artery disease

Both the animal experiments and the theoretical calculations were used to assess the effect of a partial obstruction of a coronary artery. These studies were undertaken in the hope of finding hemodynamic parameters measurable at operation which could indicate the severity of diffuse distal coronary artery disease.Measured parameters included mean coronary artery flow, systolic flow, diastolic flow, peak-to-peak flow amplitude and maximum reactive hyperemic flow. The amplitude of the flow, the diastolic/ systolic flow ratio and the maximum reactive hyperemic flow were all found to be more sensitive indicators of the degree of vessel obstruction than the mean flow. Theoretical calculations based on Poiseuille's Law give close agreement with the experimental findings.It is hoped that measurement of these sensitive parameters at operation will be of prognostic value in determining the patency rate of aorto-coronary bypass grafts.