New device for closure of muscular ventricular septal defects in a canine model.

BACKGROUND: Repair of muscular ventricular septal defects (MVSDs) has always been challenging to the surgeon. Long-term morbidity and mortality are significantly increased if the defects are closed via left ventriculotomy or if they are associated with other complex congenital anomalies. The purpose of this study was to close MVSDs with the Amplatz ventricular septal defect device. This device is constructed from 0.004-in nitinol wire mesh filled with polyester fibers. It is retrievable, repositionable, self-centering, and of low profile. METHODS AND RESULTS: MVSDs were created with the help of a sharp punch in 10 dogs. The location of the defects was anterior muscular (n=3), midmuscular (n=3), apical (n=3), and inlet muscular (n=1). The diameter of the defects ranged from 6 to 14 mm. All defects were closed in the catheterization laboratory. The device was placed with the help of transesophageal echocardiography and fluoroscopy. A 7F sheath was used to deploy the device from the right ventricular side in 8 and the left ventricular side in 2 dogs. Placement was successful in all animals. The complete closure rate was 30% (3/10) immediately after placement and 100% at 1-week follow-up. Pathological examination of the heart revealed complete endothelialization of the device in dogs killed after 3 months. CONCLUSIONS: The Amplatz ventricular septal defect device appears highly efficacious in closing MVSDs. The advantages include a small delivery sheath, complete retrievability before release, and the fact that it is self-centering and self-expanding, thereby making it an attractive option in smaller children.

Plasma lipoproteins and coronary arteriography in subjects in the program on the surgical control of the hyperlipidemias. Preliminary report.

Coronary arteriographic findings, plasma lipid and lipoprotein levels, and cigarette smoking history are reported for the first 101 male post myocardial infarction survivors who have been entered into the POSCH clinical trial. Estimates of the extent of stenosis in the major coronary arteries were made using 4 models ranging from a simple determination of the number of the 3 major vessels having significant (i.e. 50% or greater stenosis) disease to more complex methods of determining overall extent of disease in 14 major segments of the coronary arteries. Age was shown to be an important factor in the extent of vessel disease. When controlling for age, plasma cholesterol and LDL-cholesterol levels were shown to be related to the extent of disease, especially in Type II hyperlipoproteinemia subjects. Multiple linear regression analysis demonstrated that age and LDL-cholesterol had positive associations and HDL-cholesterol had an inverse association with the coronary artery disease indices. In this comparatively "healthy" subgroup of the overall population of first MI survivors the major CHD risk factors are limited to plasma lipids and cigarette smoking. This preliminary report of 10% of the recruitment objective of the project supports the currently held views of the lipid--atherosclerosis hypothesis regarding the effects of age-total plasma cholesterol, LDL--cholesterol, and HDL--cholesterol on the extent of coronary atherosclerotic plaques, as determined by coronary arteriography.

Correlation of coronary with peripheral arterial stenosis. The POSCH Group.

Although it is known that patients with peripheral arterial disease are at high risk for coronary arterial stenosis, it is not known if, conversely, coronary artery disease correlates with peripheral arterial stenosis. In the Program on Surgical Control of the Hyperlipidemias (POSCH) coronary and aortic-iliac-femoral arteriograms were systematically analyzed. POSCH is a randomised, controlled secondary intervention clinical trial of hyperlipidemic subjects, ages 30-64 years with one myocardial infarction and angiographically demonstrable coronary arterial stenosis. Of the 838 subjects enrolled in the study, 436 had diagnostic visualization of both the coronary and aortic-iliac-femoral systems. The aortic-iliac-femoral arteries were normal in 44% (194/436) of the subjects. In contrast, only 9% (37/436) of the subjects had less than 50% stenosis of all 3 coronary arteries. However, there was a positive correlation between the severity of the stenosis, if present, in the aortic-iliac-femoral arteries and that in the coronary arteries (P less than 0.001). The subjects who did exhibit aortic-iliac-femoral arterial disease were significantly older and more frequently were cigarette smokers. We conclude that subjects with coronary arterial stenosis frequently are free of peripheral arterial disease.

Clinical angiographic regression of atherosclerosis after partial ileal bypass.

Clinical documentation of atherosclerotic plaque regression has been difficult to obtain. This is a report of a patient with severe and early atherosclerotic cardiovascular disease with regression of at least three major atherosclerotic lesions demonstrated by coronary arteriography 10 years after partial ileal bypass operation. The patient's total plasma cholesterol was reduced over these 10 years, ranging from 40% to 23%, from the preoperative level of 757 mg/dl. Sequential arteriograms were assessed independently by several arteriographers and blindly by the Arteriography Review Panel of the Program on Surgical Control of the Hyperlipidemias (POSCH). The readings were analyzed by 4 grading methods. Unanimously, marked regression was read in the proximal left circumflex artery (70% leads to 20%), middle segment of the right coronary artery (45% leads to 20%), and in the distal right coronary artery (80% leads to 50%). Thus, by any and all of the methods used, there was significant regression of arteriographically demonstrated atherosclerotic lesions.

Relation between Q-QS changes on the rest electrocardiogram and left ventricular function with healed myocardial infarction.

In the Program of Surgical Control of Hyperlipidemia, the relation of the Minnesota Q-QS codes for rest electrocardiograms to left ventricular (LV) function was studied in patients with healed myocardial infarction (MI). Of 838 subjects enrolled in the study, 477 (57%) had codable Q-QS patterns at the time of randomization. There was an extremely high correlation between the level of the Minnesota code and concurrent LV function, the latter being determined on left ventriculography by both ejection fraction and the number of segmental wall motion abnormalities. Subjects without a Q-QS code had less myocardial damage than did those with a code present in a single cardiac area. Extent of LV damage correlated with the level of significance of the Q-QS code, and when the code was present in only 1 cardiac location damage was greatest if the anteroseptal area was involved. Q-QS codes present in 2 rather than 1 cardiac area were associated with an even greater degree of LV damage. A previous study has shown a strong correlation between LV function and the Minnesota codes when the latter were recorded 0.5 to 5 years (mean 2.2) earlier at the time of the acute MI. The present data show that the relation between LV function and the Minnesota codes after an acute MI persists over time and is even stronger when both are determined in the healed state at a time remote from the acute event.

Comparison of exercise-positive with recovery-positive treadmill graded exercise tests.

A treadmill exercise test response may become positive because a diagnostic electrocardiographic ST-segment shift occurred during exercise, or, less often, because it occurred only during the recovery period after exercise had been completed. Factors that may be related to these 2 different responses in subjects enrolled in the Program of Surgical Control of Hyperlipidemia were investigated. No differences were found with regard to age, sex, level or location of Minnesota electrocardiographic Q-QS codes, number of narrowed coronary arteries, presence of collateral coronary artery circulation, ejection fraction, number of abnormally moving left ventricular wall segments, heart rate, systolic and diastolic blood pressure, double product, total exercise time, exercise-induced angina, or maximally achieved exercise heart rate or double product. Thus, the same significance should be attributed to a recovery-positive as to an exercise-positive treadmill test, and electrocardiographic, hemodynamic and angiocardiographic variables do not distinguish between subjects who exhibit these 2 different responses.

Aberrant left subclavian artery in tetralogy of Fallot.

The anatomy of the aberrant left subclavian artery in a right-sided aortic arch is different in patients with tetralogy of Fallot than in persons with a normal heart. In all eight patients with tetralogy of Fallot and aberrant left subclavian artery in this series, the left subclavian artery arose directly from the distal aortic arch. In contrast, normal persons with right aortic arch and aberrant left subclavian artery invariably have an aortic diverticulum from which the left subclavian artery and the left ductus arteriosus originate. The possible different embryologic events responsible for these two forms of aberrant left subclavian artery are discussed.

Vessel wall arachidonate metabolism after angioplasty: possible mediators of postangioplasty vasospasm.

The mechanism of postangioplasty vasospasm is uncertain. It was postulated that a reduction in vasodilator prostaglandin I2 (PGI2) or prostaglandin E2 (PGE2) or an increase in vasoconstrictor hydroperoxy acids might contribute to spasm of a dilated artery. Twelve mongrel dogs were anesthetized, intubated, and mechanically ventilated. Heart rate and aortic pressures were continuously monitored and arterial blood gases maintained within physiologic limits. A single carotid artery was dilated in each animal (4 atm X 1 minute X 3) using nonexpandable polyethylene balloon catheters with inflated balloon diameters 50 to 100% larger than the internal arterial lumen. The opposite carotid artery served as a control. In 4 animals, aspirin (10 mg/kg, intravenously) was injected 30 minutes before dilation. Sixty minutes after dilation, animals were heparinized and the carotid arteries carefully removed. The in vitro conversion of carbon-14(14C)-arachidonic acid (AA) to 6-keto PGF1 alpha (PGI2), PGE2, and 12L-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE) was determined using thin-layer radiochromatography. Angioplasty caused a 70% decrease in vessel wall PGI2 production and a 44% decrease in PGE2 production (n = 4, p less than 0.05). Reductions in in vitro conversion of 14C-AA to PGI2 and PGE2 induced by angioplasty were comparable to that produced by cyclooxygenase inhibition with aspirin. Angioplasty, in addition, caused a 104% increase in vessel wall HETE production (n = 4, p less than 0.05). Therefore, angioplasty results in a local derangement of AA metabolism characterized by decreases in vasodilator prostaglandins and increases in vasoconstrictor hydroperoxy acids. These local changes may contribute, in part, to sudden arterial occlusion after angioplasty.

Directional ST-segment deviation in graded exercise tests correlated with motion of the individual segments of the left ventricular wall.

An exercise test may be characterized as positive because of the production of either electrocardiographic ST-segment depression or elevation. The relationship of exercise-induced ST-segment deviation to the specific motion abnormalities of the individual segments of the left ventricular wall was investigated. The first 280 subjects to enter the Program of Surgical Control of Hyperlipidemia were studied by treadmill exercise testing and left ventriculography. The results showed that exercise-induced ST-segment elevation could occur without evidence in the resting subject of either dyskinesia or aneurysm of the left ventricle, that the area of left ventricular damage was much greater in subjects with exercise-induced ST-segment elevation than in those with ST-segment depression, and that wall motion abnormalities were concentrated in the inferoposterior area in the group with ST-segment elevation, but were generally scattered throughout the left ventricular wall in the group with ST-segment depression.

Concomitant pulmonary and cerebral arteriovenous fistulae.

The previously unreported occurrence of concomitant pulmonary and cerebral arteriovenous fistulae was found in an individual with severe neurologic complications. Both polycythemia and paradoxical embolization were implicated in the genesis of the cerebral symptoms while the cerebral fistulae were asymptomatic. An improved method of therapeutic embolization was used to treat the pulmonary lesions, avoiding surgical resection.

Pulmonary artery banding in infants with complete atrioventricular canal.

Management of symptomatic atrioventricular canal (AVC) in infancy may be difficult. Between July, 1969, and September, 1977, 31 infants with complete AVC presented in congestive heart failure (CHF) to the University of Minnesota Hospitals. Fifteen of these patients have responded to medical management and have been followed as outpatients. The other 16 patients remained in CHF. Six of them died of persistent heart failure within 4 months. The other 10 infants, aged 3 weeks to 1 year (mean 4 months), underwent pulmonary artery banding and seven survived operation. One of the survivors died with apparent pneumonia 1 month postoperatively. Each of the remaining six patients, who have been followed for 9 months to 9 years, had minimal mitral insufficiency and a large ventricular shunt. The three patients dying after banding had significant mitral insufficiency. We believe that pulmonary artery banding is an effective palliative procedure for infants with complete AVC and CHF who have large ventricular shunts and minimal mitral insufficiency.

Silent unilateral pulmonary venous obstruction. Occurrence after surgical correction of transposition of the great arteries.

An 11-year-old girl was found to have completely obstructed left pulmonary veins eight years following corrective surgery for transposition of the great arteries. The patient was acyanotic and asymptomatic. Retrograde flow of arterial blood from the affected left lung accounted for an angiographic appearance that mimicked occlusion of the left pulmonary artery and resulted from a failure of systemic venous development. Pulmonary venous anatomy could only be demonstrated by pulmonary arterial wedge angiographic studies. This experience emphasizes that complete unilateral pulmonary venous obstruction may occur in an asymptomatic patient and underlines the importance of investigating pulmonary venous anatomy in any patient with gross inequality of the distribution of pulmonary blood flow.

Accessory flaplike tissue causing ventricular outflow obstruction.

In three cases, two in children and one in a young adult, ventricular outflow obstruction was caused by a valvelike flap of accessory endocardial tissue. The angiocardiographic feature was that of a narrow radiolucent, crescent-shaped or linear filling defect corresponding to the site of obstruction. Resection of the accessory tissue was performed in each case at the time of correction of associated conditions. In one case (a woman 20 years of age) the obstructing membrane was in the outflow tract of the right ventricle, and a ventricular septal defect was associated. In each of the other two cases the outflow tract of the left ventricle was the site of obstruction. In one (a 14-month-old boy), an ostium primum type of atrial septal defect and cleft mitral valve were associated; in the remaining case (a 7-year-old boy) complete transposition and ventricular septal defect were also present. In the latter case a Mustard procedure was performed and was followed by death. Successful results were obtained in the first two patients.

Nonsurgical closure of patent ductus: an experimental study.

A technique is described for potential use in the nonsurgical closure of patent ductus arteriosus. Occlusion is accomplished with an Ivalon umbrella, inserted via a catheter placed percutaneously into the femoral artery. The technique was tested in thirteen dogs with surgically created shunts closely simulating patent ductus arteriosus. In two cases, the Ivalon plug was undersize; and incomplete occlusion occurred, but without embolization of the plug. In one case, the umbrella emoblized due to improper positioning. Several dogs with successfully occluded ductus were observed from two weeks to six months postoperative. In all cases, the ductus remained closed. The technique has potential application in patients with a small and long patent ductus.

Single barbed stainless steel coils for venous occlusion: a simple but useful modification.

Embolization of coils into the lungs has been reported following their use for the obliteration of large arteriovenous fistulas. So far, except for a recent report, they have not been used on the venous side of the circulation. Experimental studies at our institution demonstrated that the placement of coils on the venous side can result in embolization to the lungs, even when oversized coils are introduced. A simple, easy to perform modification of the standard stainless steel coils (Gianturco-Wallace-Chuang spring embolus and coilons) makes these devices safe embolic agents for used on the venous side of the circulation, as for example in the obliteration of spermatic veins.

In vitro metal fatigue testing of inferior vena cava filters.

RATIONALE AND OBJECTIVES: Inferior vena cava filter fractures have been described in vivo on several occasions. No studies have compared the fatigue life of the different filter types. Four different, frequently used filters (Vena-Tech filters [VTF], stainless-steel Greenfield filters [SSGF], Simon nitinol filters [SNF], and titanium Greenfield filters [TGF]) were, therefore, tested with regard to fatigue life. METHODS: Ten filters of each type were tested by compressing the filter legs repeatedly. A travel distance of 1.5 cm was used, setting minimal and maximal filter leg separations of 1.0 cm and 2.5 cm, respectively. The endpoint was filter fracture or 10,000,000 compressions. The test was then repeated on five of the filters from each group, but on a different filter leg pair. RESULTS: Seven of 10 VTFs fractured during the first part of the study, and all five VTFs fractured during the second part of the study. One SSGF fractured in each part of the study. None of the SNFs or the TGFs fractured. Significant difference in fracture frequency was found. CONCLUSION: The VTFs appear to have the shortest fatigue life. The TGF and the SNF have a fatigue life exceeding the test limits. The consequences of filter fracture are unknown.

Transcatheter occlusion of patent ductus arteriosus using a newly developed self-expanding device. Evaluation in a canine model.

RATIONALE AND OBJECTIVES: A new occlusion device designed for use in a patent ductus arteriosus was tested in an animal model. METHODS: The device consists of a self-expanding conical-shaped stainless steel mesh, with hooks encircling the expanding end acting to secure the device within the ductus. A screw thread at the apex allows attachment to a stylet, and a 6 F delivery system is used. Placement of the device was attempted in 20 canines that previously had a vascular graft surgically inserted between the descending thoracic aorta and main pulmonary artery, creating the patent ductus model. Angiographic follow-up at regular intervals was performed over a 3-month period. RESULTS: Early cases resulted in device misplacement and migration because of inaccurate assessment of ductus position and size. In 15 canines the device was placed within the ductus and regularly assessed over the 3-month placement period. Ductus occlusion occurred within 1 week in 12 of 13 dogs (92%) when device placement was considered ideal. In two dogs where significant protrusion of the device from the ductus was evident (either into the aorta or main pulmonary artery) ductus closure was delayed but present by 3 months, resulting in a 93% overall closure rate at this time. In one dog, the ductus remained partially opened. CONCLUSIONS: This self-expanding patent ductus arteriosus occlusion device is promising. The 6 F delivery system is advantageous over other devices currently available, making it more suited for use in the pediatric population. Accurate assessment of the ductus is imperative, however, to enable correct device sizing. The screw thread system allows the device to be repositioned if desired prior to deployment.

The inferior vena cava clip. The percutaneous approach.

Pulmonary embolism in high-risk patients may be minimized by surgical inferior vena cava (IVC) clipping or by the insertion of caval filters. A percutaneous clipping technique was developed that narrows the cava while allowing caval patency. The caval clip is inserted through a percutaneous translumbar approach under fluoroscopic control. Nine dogs underwent percutaneous translumbar caval clip placement without complications. Three of four dogs, followed-up for 5 to 19 weeks by angiography and caval pressure measurements, showed caval patency. This technique eliminates the risks of surgical IVC clip placement and risks from the insertion of intravascular foreign bodies such as filters.

Experimental myocardial infarction in the closed-chest dog: a new technique.

The reliable and safe production of myocardial infarction in closed-chest animals is of paramount research interest. To date, the injection of particulate matter and the introduction of occlusive solid plugs have been described. Because of the limited size of the catheter, only small branches could be occluded, which resulted in a high incidence of mortality. A new simple technique is described that allows occlusion of a major coronary artery at a preselected site. An Ivalon (polyvinyl alcohol) plug compressed around the tip of an introducing wire is advanced through a selectively placed catheter into the coronary artery. It is felt in place for 5 minutes and assumes its original size upon contact with blood. Once the plug is re-expanded, the wire is withdrawn. The new technique was carried out successfully on nine dogs with no immediate fatality and myocardial infarction as demonstrated by cine ventriculography and histopathologic examination.

Effects of dilating the canine pulmonary annulus with two balloons. Doppler ultrasound and postmortem findings.

Simultaneous inflation of two balloons may be necessary for balloon dilation valvuloplasty in patients with a large annulus. We examined the cardiovascular effects of dilating the pulmonary annulus with two balloons in 18 normal dogs using pulsed Doppler ultrasound and gross and microscopic examination. When the ratio of the cross-sectional area (CSA) during dilation to the CSA of the pulmonary annulus was between 1.04 and 1.28, there was valvar regurgitation in only one dog, in which catheter manipulation was complicated by heartworms, and damage was confined to intimal changes. (The dog was killed 24 hours after dilation.) With ratios between 1.67 and 1.76 (equal to the CSA of a single balloon with a diameter 33% greater than the annulus), there was trivial or mild tricuspid or pulmonary regurgitation, and anatomic changes were more prominent but still superficial. Two animals killed after nine days had resolution of valvar regurgitation and healing damage. With CSA ratios greater than 2.00 or with balloon rupture, myocardial damage and laceration of the pulmonary arteries resulted. Simultaneous inflation of two balloons within the right ventricular outflow tract with CSA ratios of up to 1.76 results in minimal cardiovascular trauma.