A new method for the quantitative standardization of cross-sectional areas of the pulmonary arteries in congenital heart diseases with decreased pulmonary blood flow

A new angiographic method for quantitative standardization of cross-sectional area of bilateral pulmonary arteries, the PA-index, and retrospective analysis of the PA-index in different types of operative procedures are presented. This study included 40 subjects in the normal control group, 46 patients in the tetralogy group, 26 patients in the Rastelli group, and 15 patients in the Fontan group. The normal value of the PA-index was 330 +/- 30 mm2/BSA and was consistent in a wide range of body surface areas from infancy to adolescence. The PA-index in the tetralogy and Rastelli groups ranged from 100 to 400 mm2/BSA. There were no early deaths in the tetralogy group, but the incidence of low cardiac output was higher in patients with a smaller PA-index, especially when the PA-index was less than 150 mm2/BSA. Low cardiac output was more severe in the Rastelli group. The operative mortality was significantly affected by the PA-index. In the Rastelli group, all of the patients with a PA-index of less than 200 mm2/BSA died, whereas the mortality rate in patients with a PA-index of more than 200 was only 6% (p less than 0.01). The mortality rate was not influenced by any other factors, such as aortic cross-clamp time or age at operation. In the Fontan group, two patients with a PA-index of less than 250 mm2/BSA died of severe heart failure, and 12 of 13 patients with a PA-index of more than 250 survived (p less than 0.01). Our results indicated the validity of the PA-index in predicting the postoperative prognosis of the various entities. In tetralogy, all patients with a PA-index over 100 mm2/BSA can undergo correction safely; in Rastelli operation, those with a PA-index under 200 should have a palliative procedure first, whereas those with a PA-index over 250 can be considered good candidates for the Fontan procedure. The PA-index may also serve a useful guide in comparing surgical results from different institutions with patients having anomalies of varying severity.

[External conduit repair for congenital heart diseases]

Between January 1970 and March 1984, external conduit repair was performed in eighty-five consecutive patients for various complex anomalies. The age at operation ranged from 2 months to 47 years, and 41 patients were in an age group of 5 to 9 years. Among 85 complex anomalies, 20 cases of d-transposition with VSD + PS, 33 cases of Tetralogy of Fallot with pulmonary atresia, 11 cases of truncus arteriosus and 11 cases of 1-transposition were included. From January 1970 to December 1975, conduits used were aortic homograft in 1, formalin treated porcine valved conduits in 27, and valved conduits treated with 0.65% glutaraldehyde in 3 and from January 1976 to November 1982, 42 Hancock composite grafts were used. Since December 1982, valved conduits made of preserved pericardium treated with glutaraldehyde were employed. In sixty-one patients survived from operation, actuarial survival rate was calculated as 87% at five years, 82% at ten to fourteen years. However, systolic pressure of right ventricle after repair mostly affected actuarial survival rate which maintained 93% at twelve years in patients with systolic pressure lower than 80 mmHg, and reduced to 65% at fourteen years in patients with that higher than 80 mmHg. Although external conduit repair was valuable for surgical treatment in complex anomalies, proper selection of conduit material, prevention of infectious endocarditis, and pseudoendothelial proliferation in late stage were the problems to be solved in the future.

Long-term evaluation of pericardial substitutes

The development of postoperative pericardial adhesions increases the risk of cardiac reoperations because of the danger of damaging the heart, great vessels, or grafts. Several pericardial substitutes have been tested in the past in an attempt to facilitate reoperation, with inconclusive results. This study evaluated eight different materials as pericardial substitutes: six synthetic materials and two different preparations of bovine pericardium. In 32 dogs a 10 by 5 cm piece of pericardium was excised through a right thoracotomy and the defect closed with a measured patch. Each material tested was implanted in four dogs that were put to death at 3, 6, 9, and 12 months. At autopsy the development of adhesions and epicardial reaction were graded as none, minimal, moderate, and severe. Histologic studies of the patch, the epicardium, and the suture line were performed. Our results suggest that both types of bovine pericardium were an excellent substitute. Although minimal adhesions developed, these were easily dissected. The underlying anatomy was clearly recognizable because of the lack of epicardial reaction. Silicone rubber-coated polyester fabric was an acceptable material for the prevention of adhesions, but a severe fibrous epicardial reaction impeded the recognition of the coronary arteries. Both silicone-filled and high-porosity polytetrafluoroethylene (PTFE) films reduced adhesions but caused a severe epicardial reaction. The other synthetic materials were considered inferior because of severe epicardial reaction and/or structural deterioration.

Reduction of myocardial infarct size in swine: a comparative study of intraaortic balloon pumping and transapical left ventricular bypass

This study compared intraaortic balloon pumping (IABP) and transapical left ventricular (LV) bypass for their effectiveness in reducing infarct size in swine. In 28 pigs (25.4 +/- 4.7 kg) the left anterior descending coronary artery was ligated distal to the first diagonal branch. Nine animals served as controls. Nine animals were treated with IABP and the remaining 10, with transapical bypass. Ten animals-3 control, 3 IABP, and 4 transapical bypass--died prior to completion of the study, thereby resulting in 6 animals in each group. Both assist devices were begun 45 minutes after coronary ligation, this being as rapid as mechanical intervention could be accomplished in the patient after infarction. With transapical LV bypass, 70 to 100% bypass was accomplished and the LV systolic pressure remained in the range between mean aortic pressure and 30 mm Hg less than that. All animals were killed after 24 hours. The hearts were excised and stained with nitroblue tetrazolium, and infarct size was quantitated in grams of infarct per 100 gm of LV and septal mass. After 24 hours the mean aortic pressure was 73 +/- 12 mm Hg in controls, 105 +/- 20 mm Hg in animals with IABP (p less than 0.01), and 91 +/- 13 mm Hg in those with transapical LV bypass (p less than 0.05). The infarct size was 22.7 +/- 4.9 gm per 100 gm of LV and septal mass in control animals. With IABP, the infarct size was nonsignificantly changed to 19.4 +/-5.9 gm per 100 gm (p greater than 0.3). With transapical LV bypass, the infarct size was significantly reduced to 15.9 +/- 3.5 gm per 100 gm (p less than 0.025). This represented a 30% reduction of infarct size from controls. These results demonstrate that despite hemodynamic improvement with IABP, transapical LV bypass is necessary to markedly decrease myocardial work and significantly reduce infarct size.

Effect of coronary artery reperfusion on infarct size in swine

Several authors have reported a low mortality and salvage of ischemic myocardium in patients undergoing coronary revascularization after recent myocardial infarction. In this study, 20 surviving pigs with a coronary circulation similar to that of man were divided into two groups of 10 animals each. In the first group, the left anterior descending coronary artery (LAD) was ligated just beyond the first diagonal branch. Five animals were put to death at 24 hours and the remaining five animals, at 7 days. In the other group of 10 animals, the LAD was occluded just beyond the first diagonal branch and reperfused 3 hours after occlusion. Five of these animals were put to death at 24 hours and the remaining five animals, at 7 days. The left atrial pressure (LAP), heart rate, mean arterial pressure (MAP), and cardiac output were continuously monitored. Myocardial infarct size was determined planimetrically after the myocardium was sliced and stained with nitroblue tetrazolium. In five animals subjected to ligation for 24 hours, myocardial infarct size was 20.3 +/- 0.53 standard error mean (SEM) grams infarct per 100 gm left ventricular and septal mass (gm/100 gm LVS). In five animals subjected to occlusion, reperfusion in 3 hours, and death at 24 hours, the infarct size was 22.9 +/- 1.7 SEM gm/100 gm LVS. At 1 week in the ligated animals the infarction decreased to 15.5 +/- 1.7 SEM gm/100 gm LVS. In the reperfused animals at 1 week the infarction size was 14.5 +/- 1.7 SEM gm/100gm LVS. There was no significant difference in these values (Student's t test). Light and electron micrographs demonstrated hemorrhagic necrosis in every instance with reperfusion. Cardiac output, LAP, and MAP remained unchanged after reperfusion. These data suggest that in human beings without well-developed inherent collaterals sustaining myocardial infarction with coronary occlusion, that reperfusion as early as 3 hours after infarction would not be beneficial.

A silent period in sural muscle occurring prior to the voluntary forward inclination of the body

A silent period lasting for 300-500 msec was observed in triceps surae muscle when the subject inclined forward from the normal standing. This silent period preceded 100 msec or more the beginning of the body inclination and was terminated by an abrupt refiring in the midst of the body swing. The silence was not preceded by the increase in activity of the sural muscle itself or any other leg muscles studied. H-reflex in soleus was strongly inhibited or disappeared during the silent period, indicating that the excitability of the spinal motoneurons was greatly decreased during this period. These findings suggest that the silent period was not induced by some reflex activity in the spinal cord, but was caused by the inhibitory activity based on a central program on the spinal motoneurons.

Failure of intra-aortic balloon pumping to reduce experimental myocardial infarct size in swine

Although intra-aortic balloon pumping (IABP) is reported to reduce myocardial infarct size in dogs, this phenomenon may be due to pre-existing collaterals in this species. Pigs more closely approximate human coronary anatomy, having poor inherent collateralization. This study evaluates hemodynamic changes and quantitates myocardial infarct size 24 hours after coronary occlusion in swine, with and without IABP. Eighteen pigs underwent ligation of the left anterior descending coronary artery distal to the first diagonal branch: Nine were treated with IABP beginning 45 minutes after coronary occlusion and nine served as control subjects. Three in each group died prior to completion of the study. In both groups myocardial infarction resulted in a significant (p less than 0.05) decrease of cardiac output (28.5%) and mean aortic pressure (p less than 0.05) improvement of mean aortic pressure (4 to 7%) during the switch on period. After 24 hours, mean aortic pressure in IABP-treated animals (105 +/- 20 mm Hg) was significantly (p less than 0.01) higher than in control pigs (73 +/- 12 mm Hg). Myocardial infarct size as detected by staining with nitroblue tetrazolium was 22.7 +/- 4.9 gm infarct/100 gm left ventricular and septal mass in control pigs and 19.4 +/- 5.9 gm infarct/100 gm left ventricular and septal mass in treated animals (p less than 0.3). In conclusion, IABP, despite significantly improving circulatory parameters, does not significantly reduce the size of an acute myocardial infarction after coronary ligation in swine.