2:00 p.m. Scientific Session - Grand Ballroom

8. Hypothermic Circulatory Arrest and Posterolateral Exposure for Aortic Operation

E. STANLEY CRAWFORD, JOSEPH S. COSELLI*

and HAZIM J. SAFI*

Houston, Texas

Hypothermic circulatory arrest using total cardiopulmonary bypass has proven useful for cerebral protection during operation for disease of the heart and great vessels performed through anterior incisions. Hypothermic arrest using partial femoro-femoral bypass and postero-lateral incisions in the treatment of arch and descending thoracic aortic problems has been generally overlooked. The purpose of this report is to present its application in 17 patients either electively or for unexpected events or findings occurring during operations in the posterolateral position. These include (group 1) aneurysms of the transverse arch and thoraco-abdominal aorta for reasons of exposure, 2; (group 2) to avoid distal cross clamping to prevent lacerations and cerebral emboli in patients with atherosclerotic disease, 6; (group 3) inability to isolate distal arch or proximal descending thoracic aorta for clamping, 4; (group 4) accidental entry into pulmonary artery or aorta at site of clamping, 3; (group 5), descending thoracic aneurysm too large for proximal exposure needed for clamping, 1; (group 6), unusual congenital malfunctions of aorta, 1. There were 14 survivors (82%). One death from hemorrhage occurred in group 3. Two patients in group 2 died, one from heart failure and one from pulmonary embolus. The method has proved protective of neurologic function, was life-saving in some instances, and permitted operation in others that would have been inoperable by other methods.

*By Invitation

9. Surgical Treatment of Coarctation of the Aorta Following Balloon Angioplasty

BERKELEY BRANDT, III, WILLIAM J. MARVIN, JR.*

and EARL F. ROSE*

Iowa City, Iowa

This study was designed to assess the long-term effects of balloon angioplasty (BDA) for coarctation of the aorta. Eleven asymptomatic children, age four to six years, underwent BDA. Mean peak gradient fell from 50.5 ± 4.7 mm. Hg. prior to BDA to 21.7 ± 3.1 immediately post BDA. Children were then followed at three to six month intervals and were recatheterized five to fourteen months post BDA. Based on this catherization, patients were divided into three groups: Group I - four patients, residual gradient less than 10 and minor anatomic abnormalities; Group II - three patients, the gradient had increased to near pre-angioplasty level, mean 43 mm. Hg; Group III - four patients, developed aneurysmal dilatation in the area of the BDA.

The seven patients in Group II and III underwent elective resection of their coarctation at seven to twenty-eight months following BDA with end-to-end anastomosis. Spinal cord evoked potentials were monitored during operation. There were no operative deaths and all patients had no gradient between arm and leg pressures postoperatively. One patient had mild paresis of the lower extremities. Pathological examination of the specimens revealed an absence of muscle and elastic lamella in the area of the aneurysms. This finding was present in all specimens regardless of whether there was aneurysmal dilatation. Neofibroelastic proliferation at the site of the tear was responsible for persistent gradients.

BDA may result in aneurysmal formation and/or recurrent stenosis in the area of the tear requiring elective surgical repair. Surgical treatment is the same as for native coarctation when done early following BDA, but may be associated with increased risk because of the lack of collateral circulation. Continued follow-up of these lesions is necessary.

*By Invitation

10. Pathogenesis of Aneurysm Formation Opposite Prosthetic Patches Used for Coarctation Repair: An Experimental Study (Forum)

ANNEMARIE P. DESANTO*, RANDALL BILLS*,

HAROLD KING and JOHN W. BROWN

Indianapolis, Indiana

Patch graft angioplasty for coarctation repair has been associated with late aneurysm formation opposite the prosthetic patch in a high percentage of patients. The etiologic possibilities include congenital abnormality of the aortic wall, surgical interruption of the vasa vasorum, intimal disruption secondary to extensive excision of the coarctation web and rigidity of the prosthetic patch. To assess the effect of extensive intimal excision on the development of aneurysms, twelve dogs underwent a left thoracotomy and patch aortoplasty with either Dacron (n = 6) or PTFE (n = 6) and concomittant intimal excision opposite the patch. Ten dogs underwent patch angioplasty with Dacron (n = 5) and PTFE (n = 5) without excision of the in-tima and served as controls. All animals were studied with serial aortograms which demonstrated aneurysmal formation of the aorta opposite the patch in seven of the twelve dogs undergoing intimal excision. In contrast, no aneurysms developed in the control dogs (p<.003). An additional five dogs underwent longitudinal aortotomy, intimal excision and primary closure. One dog in this group demonstrated an aneurysm angiography (p<.05). Histologic analysis of the aneurysms and the control aortas is in progress.

We conclude that the extensive resection of the intima with or without patch angioplasty predisposes to aneurysm formation opposite the aortotomy and should be avoided when performing coarctation repair.

*By Invitation

11. Treatment of Extensive Aortic Aneurysms by a New Multiple-Stage Approach (Forum)

HANS G. BORST, GUNTER FRANK*

and DAGMAR SCHAPS*

Hannover, West Germany

Aortic replacement in polyaneurysmatic disease may pose considerable technical difficulties and can exceed the physical tolerance of older and/or debilitated patients. We therefore devised a multiple-stage approach whereby during primary replacement of the arch or the descending aorta subsequent procedures are prepared and thereby simplified. Briefly, instead of performing a conventional distal anastomosis between graft and aorta the downstream portion of the graft is sutured into the aortic lumen in such a manner as to allow it to float freely in the distal aneurysm in "elephant trunk" fashion. During the subsequent replacement procedure, only one (distal) graft-to-aorta anastomosis is required and aortic cross-clamp time thus is reduced.

Since 1982, 15 such operations were completed in 7 patients without fatality. In 4, the primary procedures involved the aortic arch, in 3 patients the proximal descending thoracic aorta. Simple cross-clamping of the descending aorta was employed throughout. The "elephant trunk" technique is considered a helpful variant for dealing with aneurysmatic disease involving extensive or multiple sections of the aorta.

*By Invitation

12. Implantable Extra-Aortic Balloon Assist Powered by Transformed Fatigue Resistant Skeletal Muscle (Forum)

RAY C.-J. CHIU, GARRETT L. WALSH*,

MICHAEL L. DEWAR*, JEAN H. DESIMON*,

AIDA S. KHALAFALLA* and DAVID IANUZZO*

Montreal, Quebec

The hypothesis tested in this study was whether a skeletal muscle could be transformed to be fatigue resistant, and used to power an implantable extra-aortic balloon assist (EABA) device, achieving hemodynamically significant cardiac assist.

Eight dogs underwent implantation of Itrel pacemaker to stimulate thoraco-dorsal nerves over 8-18 weeks in order to transform their latissimus dorsi muscles (LDM). Biopsies of these muscles confirmed near complete (up to 98%) transformation into fatigue resistant Type I muscle fibers, identified by the ATPase histochemical technique. Biochemical assays showed successful conversion of myosin isoforms to that of myocardial V₃ genotype, decreased anaerobic glycolytic (phosphofructokinase) and increased aerobic (citrate sythase) enzyme markers, all indicating greater resemblance of such muscle to the myocardial fibers. Then, using a force transducer and a burst "pulse-train" stimulator, the latter designed to synchronize and optimize skeletal muscle contraction for cardiac assist, we identified in 4 dogs the optimal stimulation parameters for the transformed LDM as follows: Pulse-train duration 250 msec., pulse width 230 msec., frequency 50 Hertz. Fatigue tests over 45 minutes with 3,600 repetitive contractions resulted in 65% force reduction in non-transformed LDM, while transformed LDM lost less than 5% of force.

In the remaining 4 dogs, a 100 ml. balloon, made of thrombo-resistant Biomer, was placed beneath the transformed LDM. A 1 cm. Dacron graft was anastomosed end-to-side to the thoracic aorta, then connected to the balloon. Using our burst stimulator and the stimulation parameters listed above, the LDM was stimulated to contract during diastole, compressing the balloon to achieve diastolic augmentation. The balloon filled during systole. Using the pressure tracings obtained from the ascending aorta, we calculated the subendocardial viability index (SEVI = DPTI/TTI). In a series of on-off studies, we observed a significant 39.5 ± 4.2 (SEM) % (p<0.001) increase in SEVI when EABA was activated. Chronic sheep studies with Theologically improved, totally implantable device is in progress.

We conclude that the skeletal muscle can be transformed to resemble myocardium, and it can be used as an endogenous energy source to provide hemodynamically significant cardiac assist.

*By Invitation

13. Oxygen Consumption of Fatigue-Resistant Muscle (Forum)

MICHAEL A. ACKER*, WILLIAM A. ANDERSON*,

ROBERT L. HAMMOND*, MICHAEL VELCHIK*,

STANLEY SALMONS* and LARRY W. STEPHENSON

Philadelphia, Pennsylvania

Skeletal muscle can be made fatigue-resistant by chronic electrical conditioning. We have constructed non-fatiguing pump motors from such muscle which augment cardiac function and by P-NMR spectroscopy showed high energy phosphate metabolism similar to cardiac muscle.

This study examines directly O₂ consumption for this muscle during exercise. The latissimus dorsi (LD) muscles of 5 dogs were electrically conditioned for eight weeks using the same type of electrical burst stimulation needed for activation of cardiac work. Isometric tension, blood flow (radioactive micro-spheres) and O₂ consumption were then measured for each dog's conditioned and contra-lateral control LD during rest and two successive 11 minute periods of stimulation - 25 Hz burst for 300 msec and then 800 msec (1100 msec duty cycle).

Histologically, the muscle was transformed to fatigue-resistant Type I fibers. Fatigue rates were 54 and then 60% for control vs. 18 and then 27°/o for conditioned. The ratio of the developed time-tension product to O₂ consumed for the control muscle at 300 msec and 800 msec respectively was 27 ± 2.2 (S.E.M.) and 18.6 ± 2.3. In contrast, the ratio for the conditioned muscle was 38.4 ± 5.8 and 50.5 ± 2.1.

Results, depicted graphically below, indicate fatigue resistance of conditioned muscle is related to increased efficiency of O₂ utilization, thus making transformed muscle capable of cardiac-type work.

*By Invitation

14. Dramatic Recovery of the Failing Canine Heart with Biventricular Support in a Previously Fatal Experimental Model (Forum)

GEORGE J. MAGOVERN, JR.*, RACE L. KAO*,

IGNACIO Y. CHRISTLIEB*, GEORGE LIEBLER*,

SANG PARK*, JOHN BURKHOLDER,

THOMAS MAHER*, DANIEL BENCKART*

and GEORGE J. MAGOVERN

Pittsburgh, Pennsylvania

The clinical use of the vortex pump (Bio-Medicus) for cardiogenic shock following open heart surgery has led to dramatic functional recovery. The present study was undertaken to elucidate the mechanisms and time course of ventricular recovery following prolonged global ischemia.

Ten dogs underwent 45 minutes of normothermic aortic cross-clamping followed by 24 hours of biventricular support. No heparin was given. Developed pressure (DP), dp/dt, ATP, and electron microscopic biopsies were obtained at control and serially measured at end ischemia, at 20 minutes of reperfusion, and after 12 and 24 hours of biventricular support. Results are expressed as mean ± SEM.

Time	EKG	DP (mmHg)	+ dp/dt	ATP*	LV Biopsy
Control	NSR	90.4 ± 6.4	4264 ± 366	3 1.47 ± 0.77	Normal
45 Min	VF	0**	0**	14. 63 ± 0.91**	Moderate
20Min	VF	0**	0**	17.72 ± 1.18**	Severe
12Hrs	NSR	68.0 ± 10.1	2649 ± 412**	25.21 ± 1.73**	Moderate
24Hrs	NSR	76.3 ± 8.9	4282 ± 585	31.48± 1.74	Mild
(*mmoles/g heart protein, **p<.01 vs control)

After 45 min of normothermic ischemia, none of the hearts were able to generate a pressure or sustain a stable rhythm. This hemodynamic instability correlated with significantly lower ATP levels and with marked ultrastruc-tural swelling and organelle disruption. Importantly, after 24 hours of biventricular support, ATP levels returned to control levels, ultrastructural changes were reversed, and left ventricular function significantly improved. Six of ten hearts were successfully weaned from biventricular support, and all hearts were weaned from left heart assist without pressor support. Thus, temporary circulatory support with left and right heart assist can permit recovery of ventricular function from profound normothermic ischemia.

*By Invitation

15. In Vivo Evaluation of a New Thromboresistant Polyurethane for Artificial Heart Blood Pumps (Forum)

DAVID J. FARRAR*, PHILIP LITWAK*,

JOHN H. LAWSON*, ROBERTS. WARD*,

KATHLEEN A. WHITE*, A. J. ROBINSON*

and J. DONALD HILL

Berkeley and San Francisco, California

To reduce the risk from thromboembolic complications in prosthetic blood pumps we have developed a new segmented polyurethaneurea elastomer (BPS-215M). This material is unique because its bulk properties, for proven long term durability, and surface properties, for biocompatibility, have been separated and developed in two distinct materials. Blending of the two components resulted in a single material incorporating the properties of each.

To evaluate this material in vivo, we performed 10 calf implants of the Pierce-Donachy prosthetic ventricle with blood pumping sacs fabricated from BPS-215M, and four control implants with blood sacs fabricated from Biomer® which is the present clinical standard. The blood pumps were connected from the apex of the left ventricle to the descending aorta in 82-108 kg male Holstein calves, and they were driven pneumatically in the full-to-empty mode with flows averaging 5 to 6 1/min. Each calf was medicated with aspirin and persantine throughout the study period and electively sacrificed after 4 weeks for evaluation of explanted blood sacs and for renal infarction.

All ten BPS-215M blood sacs were shiny and completely free of any thrombus. Two of the four explanted Biomer blood sacs showed visible moderate sized areas of red thrombus, and one showed very minor white thrombus. Use of a quantitative scale to assess renal infarction demonstrated that three animals with Biomer blood sacs had the greatest number and size of infarcts ranging from 1 to 20 mm, while one Biomer animal and all ten BPS-215M animals showed little infarction. Based on these experiments, we conclude that for use in artificial heart blood pumps BPS-215M is superior to Biomer in blood compatibility and in freedom from thromboembolic risk. BPS-215M is now ready for clinical evaluation.

3:40 p.m. Intermission - Visit Exhibits - Wacker Hall

Complimentary coffee available

*By Invitation

4:15 p.m. Scientific Session - Grand Ballroom

16. A Prospective Study Comparing Magnetic Resonance Imaging Computed Tomography in the Preoperative Evaluation of Mediastinal Node Status in Patients with Lung Cancer

ALEC G. PATTERSON*, ROBERT J. GINSBERG,

PETER POON* PAUL F. WATERS*, MELVYN GOLDBERG,

FREDERICK G. PEARSON, THOMAS R. TODD,

JOEL D. COOPER and DONALD P. JONES*

Toronto, Ontario

We have carried out a prospective study in 124 patients to compare the accuracy of computed tomography (CT) to magnetic resonance imaging (MR) in the detection of mediastinal lymphadenopathy in patients with potentially resectable bronchogenic carcinoma. A prototype 0.15 Tesslar resistive imager provided the MRI scans. CT scanning utilized a fourth generation machine. Following these non-invasive procedures, all patients had mediastinal node status surgically assessed by mediastinoscopy (and anterior mediastinotomy for left upper lobe tumours). In 23 patients, despite negative mediatinoscopy, no thoracotomy was performed. Since the "negative" mediastinoscopy was not confirmed at thoractotomy, these patients were eliminated from further analysis. Seventy-six "negative" mediastinoscopy patients and 6 of 25 "positive mediastinoscopy patients had further nodal staging at the time of resectional surgery. In these 101 patients, with absolute confirmation of nodal status, the efficacy of CT and MRI are demonstrated in the following results:

	Sensitivity	Specificity	Accuracy
CT	72	93	86
MRI	72	94	87

Mediastinoscopy had a higher sensitivity (86%), specificity (100%) and accuracy (96%), than either non-invasive modality.

Our results suggest that in preoperatively assessing mediastinal node status, fourth generation CT scans offer the same sensitivity, specificity and accuracy as a prototype 0.15 T resistive imager. Higher Tesslar imagers are not anticipated to improve the accuracy unless innovative developments occur to improve tissue specificity, allowing one to distinguish malignant from benign lymphadenopathy and to detect microscopic tumour in normal sized nodes.

CT scans offer the same sensitivity, specificity and accuracy as magnetic resonance imaging. Both non-invasive techniques continue to have a significant error rate when compared to invasive surgical staging.

*By Invitation

17. Extended Cervical Mediastinoscopy - The Best Procedure for Staging Left Upper Lobe Tumours

ROBERT J. GINSBERG, THOMAS RICE*,

MELVYN GOLDBERG, PAUL F. WATERS

and BARBARA J. SCHOMOCKER*

Toronto, Ontario and Cleveland, Ohio

Despite a common misconception, left upper node carcinoma frequently metastasizes lymph nodes not only in the anterior mediastinum (paraaortic and subaortic) but also to the superior mediastinum. Anterior medi-astinotomy can only assess the former compartment. This procedure alone, if not done in conjunction with standard cervical mediastinoscopy, will fail to recognize technically unresectable left upper lobe N₂ disease involving the superior mediastinum. We have developed a technique to explore both regions by extending a standard cervical mediastinoscopy, eliminating the need for a second incision when this compartment requires assessment.

At the time of mediastinoscopy, the window between the left carotid and right innominate arteries, bounded anteriorly by the left innominate vein and posteriorly by the aorta, is opened by blunt digital dissection, producing a subpleural tunnel anterolateral to the aortic arch. The mediastinscopy was passed through this tunnel allowing full inspection and nodal biopsies of the paraaortic and aortopulmonary window nodes. On completion of this procedure, both the superior mediastinum and anterior mediastinum draining the left upper lobe have been completely staged.

Over 125 extended cervical mediastinoscopies have now been performed. We have found the procedure to be exceptionally safe with one superficial wound infection as the only complication.

Anterior mediastinotomy has many disadvantages including: poor visualization, difficulty obtaining nodal biopsies, injury to internal mammary vessels, wound complications including pain and infection, and the necessity of a second incision for complete staging of left upper lobe tumors. All of these problems are obviated with the use of the extended cervical mediastinoscopy. The sensitivity (74%) specificity (100%) positive predictive value (100%) and negative predictive value (89%) of extended cervical mediastinoscopy is far superior to that found with anterior mediastinotomy alone.

*By Invitation

18. Mediastinal Node Evaluation by Computed Tomography in Lung Cancer: An Analysis of 345 Patients Grouped by TNM Staging, Tumor Size, and Tumor Location

BENEDICT D. T. DALY, L. JACK PALING*,

GUNARS BITE*, M. ELON GALE*,

MARK S. BANKOFF*, YUNGJA JUNG-LEGG*,

AMIEL G. COOPER* and GORDON L. SNIDER*

Boston, Massachusetts

The precise role of computed tomography (CT) in staging the mediastinal lymph nodes of patients with lung cancer remains controversial. In order to more clearly define its value, we analyzed chest CT and surgical findings in 345 consecutive patients who underwent operative staging. Patients were grouped according to: (1) the TNM staging system of the American Joint Commission, (2) maximum tumor diameter as determined by CT or gross pathologic examination, and (3) central or peripheral location of the tumor. Tumors visible bronchoscopically or within the central !/3 of the plain chest x-ray were classified as central. Seven patients, in whom the status of the mediastinal lymph nodes could not be determined, were excluded. The incidence of mediastinal metastases, i.e., percent true-positive scans (T + ) plus false-negative scans (F -) as well as the predictive value of a negative scan (NPI) and positive scan (PPI) are presented in the following table:

CENTRAL TUMORS						PERIPHERAL TUMORS
	T1	T2	T3	Tx	S		T1	T2	T3	Tx		≤2cm	≥2cm
#Pts.	13	76	36	22	147	#Pts.	84	77	26	4	191	64	108
T+ (%)	23	20	20	91	31	T+ (%)	6	0	12	100	10	0	5
F- (%)	0	4	20	0	7	F- (%)	6	3	0	0	4	3	4
NPI (<%)	100	93	72	100	88	NPI (%)	93	97	100	100	96	97	96
PPI (%)	75	48	64	100	68	PPI (%)	63	67	43	100	0	0	42

These data demonstrate a significant incidence of mediastinal metastases in patients with central tumors (38%). The predictive value of a negative CT for central tumors was high (93-100%), except in the T₃ group (72%). The PPI was relatively low (68%). The incidence of mediastinal metastases in patients with peripheral tumors was 14%. Twenty of 191 (10%) were identified by CT, and the NPI was high (93-100%). The PPI was relatively low (66%). However, there were no T + scans for lesions ≤2 cm in size. These data demonstrate CT is useful for staging the mediastinum in all potentially operable patients with lung cancer except those with small peripheral lesions ≤2 cm in size. Invasive staging is indicated for patients with positive scans and all patients with central T₃ lesions.

*By Invitation