1:30 p.m. Scientific Session - Grand Ballroom

39. Surgical Management of Post-Myocardial Infarction Ventricular Tachyarrhythmia by Myocardial Revascularization, Debulking Procedure and Septal Isolation

HOOSHANG BOLOOKI, GEORGE M. PALATIANOS*,

LIAQAT ZAMAN*. RICHARD J. THURER*,

ROBERT J. MYERBURG* and RICHARD M. LUCERI*

Miami, Florida

Sustained ventricular tachycardia/fibrillation (VT/VF) early after myocardial infarction (up to 8 weeks) carries a high risk (>80% mortality in 6 months) when managed by conventional medical or surgical techniques. We have devised a more extensive procedure to be used as a last resort and have used it in 16 moribund pts (13 males, 3 females) with a mean age of 61 years. The procedure consisted of complete myocardial revascularization and debulking by extensive infarctectomy with unguided endocardial resection and septal isolation with support of its necrotic wall with a thick Teflon® patch (average size 10 cm²). Defibrillator patches were implanted in 4 pts. Perioperative myocardial preservation was with blood cardioplegia and intra-aortic balloon assist (12 pts). Postoperative (postop) studies in 3-10 days showed cardiac index rose from 2.1 ± 0.4 to 2.6 ± 0.6 L/min/m²* (mean ± SD), wedge pressure declined from 26.4 ± 3.8 to 13.3 ± 4.0 mmHg* and ejection fraction increased from 23 ± 5% to 35 ±7%.* Thirty day mortality was 12% (2 pts). During postop electrophysiologic testing VT was not inducible, in 8 of 10 pts (83%). During mean follow-up of 14 months 9 of 14 pts (64%) are alive. This procedure which aims at improving ventricular function and fibrillatory threshold and ablating the dysrhythmic foci seems effective in prevention of arrhythmic deaths and control of congestive failure.

*p<.002

1:40 a.m. Discussion

*By Invitation

1:50 p.m.

40. Improved Results in the Operative Management of Ventricular Tachycardia Related to Inferior Wall Infarction - Importance of the Annular Isthmus

W. CLARK HARGROVE*, JOHN M. MILLER*,

JOSEPH A. VASSALLO* and MARK E. JOSEPHSON*

Philadelphia, Pennsylvania

Sponsored by: L. HENRY EDMUNDS, JR

Philadelphia, Pennsylvania

Ventricular tachycardia (VT) associated with inferior wall myocardial infarction (IMI) has had a lower surgical cure rate with localized subendocardial resection (SER) then VT related to anterior infarction (AMI). Some investigators have advocated visually directed extensive SER including resection of the papillary muscles and mitral valve replacement even without documenting VT origin at these sites.

We have operated on 42 patients (39 men, 3 women) for VT associated with IMI. Thirty-one patients had standard localized SER without mitral valve replacement (Group I). Eleven consecutive recent patients (Group II) underwent SER plus focal endocardial cryoablation (3 minutes at -60°C) of the annular isthmus. The annular isthmus is defined as the ventricular muscle between the basal end of the ventriculotomy and the mitral valve annulus. In Group I there were 4 operative deaths (13%) and VT remained inducible in 12 patients (44%) at postoperative electrophysiologic studies (EPS). In Group II there was 1 operative death (9%) and nine of 10 survivors (90%) had no inducible VT at postoperative EPS (P<0.05 vs Group I). No Group II patient required mitral valve replacement. Five of the ten operative survivors in Group II had intraoperative activation maps consistent with macroreentry incorporating the annular isthmus. Group I and Group II were indistinguishable in preoperative hemodynamics, number of coronary arteries diseased and bypassed, or the presence of left ventricular aneurysm. These results suggest that SER with additional cryoablation of the annular isthmus results in improved VT control inpatients with VT associated with IMI and does not require mitral valve replacement. These data also suggests that the annular isthmus is a critical component of the reentrant circuit in these tachycardias.

2:00 p.m. Discussion

*By Invitation

2:10 p.m.

41. An Autologous Biologic Pump Motor: One Week Experience

MICHAEL ACKER *, ROBERT HAMMOND*,

JOHN MANNION *, STANLEY SALMONS*

and LARRY STEPHENSON

Philadelphia, Pennsylvania

One method to augment the failing heart would be to construct a ventricle of living, contracting, autologous tissue. Although theoretically appealing, skeletal muscle-powered cardiac assist devices have thus far been hindered by muscle fatigue. We have demonstrated that skeletal muscle ventricles (SMV), through a combination of vascular delay, chronic electrical conditioning and multi-layered construction can be made more fatigue-resistant. These SMVs, when connected to the canine systemic arterial circulation, are capable of generating systemic pressures and outputs of up to 20%of the animal's cardiac output for 8 hours.

In this experiment 5 dogs had SMVs constructed of multi-layered latissimus dorsi muscle. The SMVs first underwent a 3 week vascular delay rest period followed by 7-10 weeks of electrical conditioning via their motor nerve. The SMVs were then connected to a totally implantable mock circulation circuit. This system permitted control of the SMVs' preload and afterload as well as the ability to measure the SMVs' pressures and ejection flow. Except during daily measurements, no wires or tubes crossed the skin barrier. The SMVs were actuated via their motor nerve by an implantable pulse generator that delivered a burst pattern of 25 Hz for 312 msec on, 812 msec off.

Over a one week period of continuous pumping, 3 of 5 SMVs exhibited no fatigue. Of those 3, one 12 kg dog has generated continuous pressures of 90/25 with continuous flows of 230 ccs/min. The stroke volume of the SMV at 7 days was 5 cc and the ejection fraction 91%. By altering the preload and afterload conditions of the SMV at one week, this animal's SMV was capable of generating sustained pressures of 190/55.

This study indicates that it is possible to construct a non-fatiguing, biologic pump motor from skeletal muscle. This concept holds great promise for long-term augmentation of the failing heart.

2:20 p.m. Discussion

*By Invitation

2:40 p.m.

42. Mechanical Support of the Circulation Followed by Cardiac Transplantation

JOHN L. PENNOCK, WILLIAM S. PIERCE,

DAVID B. CAMPBELL *, DWIGHT DAVIS*,

FREDERICK A. HENSLEY*

and JOHN A. WALDHAUSEN

Hershey, Pennsylvania

Improvements in mechanical circulatory support (MCS) and immune therapy promise a wider use of sequential mechanical support followed by orthotopic cardiac transplantation (CTx). The intra-aortic balloon (IABP), left (L) and right (R) ventricular assist pumps (VAD), and the pneumatic artificial heart (TAH) represent the potential range of devices capable of keeping a patient alive who would otherwise die awaiting a potential donor organ. The major obstacle to circulatory support is the possibility of infection resulting from the required percutaneous tubes. It is speculated, though not proven, that cyclosporine combined with low dose steroids may provide the required degree of immune suppression but not eradicate resistance to infection, thus allowing graft and host survival following sequential cardiac procedures. We report here our experience utilizing mechanical circulatory support devices as a bridge to successful CTx.

Four patients in a series of 26 consecutive transplant procedures have required preeoperative MCS. Two patients required the use of IABP for two and 14 days pretransplant. Both patients are alive and well six months post-CTx. One patient required LVAD for 21 days pre-CTx. This patient is alive and well two months post-CTx. One patient required TAH support for 11 days pre-CTx and is presently two days from his transplant procedure. A fifth patient required L and R VAD support but died of sepsis after 14 days (no CTx).

Our early experience appears to indicate that partial or total mechanical support followed by CTx is therapeutic.

2:50 p.m. Discussion

*By Invitation

3:00 p.m.

43. Extracorporeal Membrane Oxygenation for Respiratory Failure

ROBERT M. ARENSMAN*, CLYDE R. REDMOND*,

KENNETH W. FALTERMAN* and JOHN L. OCHSNER

New Orleans, Louisiana

Extracorporeal membrane oxygenation (ECMO) has been used in our institution to treat 46 patients with cardiorespiratory failure. This includes 40 neonates and 6 pediatric patients. Venoarterial bypass is achieved by can-nulating the right atrium via the internal jugular vein and the aortic arch via the right common carotid artery. A 5-inch roller pump is used to circulate the blood through a 0.4 to 1.2m² silicone membrane lung. This not only oxygenates the blood but also acts as both a right and left ventricular assist device by decompressing the pulmonary circuit and supporting the systemic arterial blood pressure.

Indications for ECMO in neonates are well defined, and can be used to predict an 80%-90% mortality. Of the neonates, 27 (82%) of 33 patients with persistent fetal circulation survived and 2 (29%) of 7 patients with congenital diaphragmatic hernia survived. Of the 10 old enough to undergo Bayley Infant Developmental Testing, all are within normal limits for both the mental and psychomotor developmental indices.

In pediatric patients the indications for ECMO are not well defined, but in general can be divided into two large groups. In pediatric patients with ventricular failure following cardiac surgery, ECMO can be used as cardio-pulmonary support. We have treated three such patients with one survivor. ECMO can also be used to treat children with predictably fatal but potentially reversible pulmonary failure. In this category, we have also treated three patients, with one survivor.

Our experience shows that ECMO serves a useful role in the management of carefully selected neonatal and pediatric patients with cardiorespiratory failure refractory to conventional management.

3:10 p.m. Discussion

*By Invitation

3:20 p.m.

44. Penetrating Injuries of the Diaphragm: An Analysis of 154 Cases

ROBERT WIENCEK*, ROBERT F. WILSON, ZWI STEIGER

AND RAMESH CHERUKURI*

Detroit Michigan

Penetrating injuries to the diaphragm may present special problems in trauma management because of involvement of both thoracic and abdominal organs. To evaluate our management of these injuries and look for areas of potential improvement, we analyzed the records of 154 patients with penetrating diaphragm injury seen at Detroit Receiving Hospital from July, 1980, through May, 1985.

Etiology included 89 gun shot wounds and 65 stab wounds with a mortality rate of 19% and 5% respectively. Operations on these patients were laparotomy in 117 (76%), thoracotomy in 4 (3%), and both in 33 (24%). The mortality rate with these operations was 0%, 50% and 52% respectively.

Of the 37 patients who had a thoracotomy, five were done in the ED with three (60%) deaths. Of 32 who had OR thoracotomies, 15 were done for thoracic injuries with six (40%) deaths and 17 were done for CPR or aortic cross-clamping with ten (56%) deaths. The most frequent chest injuries repaired were lung (28) and heart (8).

Of 117 patients who had a laparotomy without a thoracotomy, 55 (47%) had chest tubes inserted in the emergency department (ED) prior to surgery for hemopneumothorax. The other 62 (53%) had their chest tubes inserted in the operating room after the diaphragmatic injury was recognized. No significant difference in complications between these two groups was noted.

Of the 19 deaths, 17 occurred within 48 hours from shock-related complications. Two others died later of sepsis. Of the 135 patients who survived, 36 (27%) required more than 14 days hospitalization because of pulmonary and/or septic complications.

Thus, diaphragmatic injuries requiring emergency thoracotomy have a significant mortality (52%) related primarily to severe bleeding. A more aggressive surgical approach seems necessary. In addition, postoperatively these patients should be treated aggressively to reduce pulmonary and septic complications.

3:30 p.m. Discussion

3:40 p.m. Adjourn

*By Invitation