TUESDAY MORNING, APRIL 19, 1977

8:30 A.M. Scientific Session Grand Ballroom

13. Management of the Pacemaker Recall

DAVID C. MACGREGOR*, EDWARD J. NOBLE*, JOHN D. MORROW*,

HUGH E. SCULLY*, H. DOMINIC COVVEY*

and BERNARD S. GOLDMAN, Toronto, Ontario, Canada

Rapid technological changes in the medical devices industry have led to an alarming deterioration in the reliability and safety of the cardiac pacemaker. During the past four years, we have been subjected to eight pacemaker recalls involving 469 pulse-generators (31.9% of our total of 1470 implants).

Upon notification of a pacemaker recall, it becomes the implanting physician's responsibility to verify the manufacturer's list of affected units and to make a frank disclosure in person to the patient and/or responsible relatives. Appropriate communications must also be established with government agencies, the news media, malpractice insurance carriers and local hospital boards. Although a pacemaker manufacturer may initiate a recall and make recommendations as to whether or not an individual pulse-generator should be replaced prophylactically or subjected to increased surveillance, these decisions rest primarily with the implanting physician.

To date, 138 (29,4%) of our recall pacemakers have been replaced because of unpredicted failure, premature rate drop or fear of catastrophic failure at a mean time of 10.6 months. Only 27 (5.8%) removed units have thus far demonstrated a rate drop with battery depletion and 19 (4.1%) units have been replaced for other reasons. Patient deaths have accounted for 69 (14.7%) units and 16 (3.4%) units have been lost to followup. The remaining 200 (42.6%) recall pacemakers are under increased surveillance by our pacemaker clinic. Transtelephone monitoring assumes a major role in the management of the pacemaker recall, not only to predict, but also to identify the failure of any individual unit. Schedules should be adapted to the expected performance of suspect units and should be revised as circumstances dictate.

The authors wish to emphasize the need for improved pacemaker standards and for more extensive biological testing of new pacemaker models prior to release for human implantation.

*By invitation

14. The Changing Spectrum of Pericardiectomy for Chronic Pericarditis: Occult Constrictive Pericarditis

JAMES W. KILMAN, CHARLES A. BUSH*, CHARLES F. WOLLEY*,

JOHN M. STANG*, JOSEPH TEPLY* and NOBUHISA BABA*,

Columbus, Ohio

During the past twenty-four years seventy patients have had a total pericardiectomy at our institution. Fifty-nine patients had the classic findings of constrictive pericarditis as the reason for their surgery and operative mortality was five percent in this group. During the past few years a new indication for total pericardiectomy has been found in twelve patients. These patients have fatigue, dyspnea and chronic chest pain without any of the other classic findings of chronic constriction. Coronary angiograms have been normal. Cardiac catheterization following administration of a fluid load of 1000 cc of warm normal saline during six to eight minutes resulted in diastolic equilibration of pressures, constrictive pulse pressure contours and loss of the normal right atrial response to inspiration in all of these patients with occult constrictive pericarditis but in none of the six normal controls. Total pericardiectomy has been done with ease in this group with no morbidity or mortality. Relief of the symptoms has been dramatic. Repeat cardiac catheterization following total pericardiectomy revealed normal hemodynamics prior to and following fluid load. Tissue examination of the removed pericardium revealed gross and/or microscopic changes of inflammatory disease without calcification. Occult constrictive pericarditis appears to be a new indication for total pericardiectomy and can only be defined by the hemodynamic response to a rapid saline load.

*By invitation

15. Preliminary Clinical Experience with Isotonic Hypo-thermic Potassium Arrest (KA)

G. FRANK O. TYERS, NORMAN J. MANLEY*, DENNIS R. WILLIAMS*

and MARK KURUSZ*, Hershey, Pennsylvania

The modalities of KA and 15°C perfusion hypothermia were combined and used exclusively for myocardial protection (MP) in 70 consecutive patients (pt(s). Following aortic cross-clamping (X) the arrest solution: 275 m0sm, pH 7.7, 2500 u heparin and in meq/L:Na 141, K 25, C1 101, Ca 1.1, Mg 3, was perfused through a DeBakey cannula continuously (up to 3L) during direct coronary surgery (ACB), intermittently during multiple valves (2VR, 3VR) and once (½ to 1L) prior to single valve replacement (AVR or MVR). Left ventricular wall temps fell to 16-17ºC. Mean X time was 65 min. Preop all pts were NYHA Class III or IV, over 60% had ejection fractions < 0.50, 7 had main left stenoses (2 with tight AS), 5 were redos, 20 had recent M infarction, 8 were emergent, 2 were Jehovah's Witnesses, age ranged from 6 to 76 yrs. 30 day mortality was 4/70, < 6%. No death was related to M depression. There were 14 AVRs, 5 MVRs, 6 2VRs, 1 3VR and 5 combined VR + ACB with 2 deaths, 6.6%, 1 due to right coronary injury in a triple redo AVR with collagen disease, 1 due to hemorrhage in a 2VR, double bypass pt with functional platelet abnormality. No primary, single or multiple valve pt died. There were 35 ACBs with a mean of 3 grafts, with 1 death, 2.9% in a post MI, CHB pt with ungraftable vessels. Although several pts required preop balloon assist, this was the only pt to require postop assist and to leave the OR alive who subsequently died. There were 4 congenital cases with 1 death due to poppet dysfunction in a tunnel AS with AVR and ascending aortic graft.

As evidence of excellent MP, postop pressors were used briefly in less than 11% of pts, a greater number required postop antihypertensives, over 50% defibrillated spontaneously immediately following X release, the rest required only a 5 watt sec shock. Both cardiac output, 5.6 ±.3 L/min and cardiac index, 2.7 ±.1 L/min/m² were immediately improved versus preop levels in the same pts while awake and anxious at cardiac cath (p <.05) and mean postop MB-CPKs were not significantly elevated at 12 (16 ± 3) and 24 hrs postop (15 ± 6 u/L). Respirator, ICU and hospital days, mean blood used/patient (3.6 + .3 u), and mean bypass time (94 min) were all equal or better than with coronary perfusion.

The significant advantages of 15°C KA are: 1) simplified high volume aortic root perfusion, effective even with 4 + AI, 2) the preclusion of the "calcium paradox", 3) minimization of defibrillator induced M injury, 4) operating conditions superior to normothermic ischemic arrest or topical hypothermia, 5) avoidance of coronary artery trauma and 6) extensive clinical and experimental evidence of superior MP.

*By invitation

16. Prolonged Safe Aortic Cross Clamping by Combining Membrane Stabilization, Multi-dose Cardioplegia and Physiologic Reperfusion

DAVID FOLLETTE*, KLAUS FEY*, DONALD G. MULDER,

JAMES V. MALONEY, JR. and GERALD BUCKBERG,

Los Angeles, California

We have shown that 1) continuous adequate perfusion of the beating heart, although cumbersome, prevents low output syndrome and 2) the superb operating conditions of arrest cannot be achieved safely with hypothermic (perfusion or topical) ischemic arrest; deleterious changes in LV flow, distribution, metabolism, compliance and function occur after only one hour of cross clamping. This study tests the hypothesis that prolonged (2 hours) of safe arrest is possible by combining membrane stabilization, cardioplegia, and physiologic reperfusion during cross clamping.

Methods: We studied 32 dogs using standard cardiopulmonary bypass. Ten dogs (control) underwent ischemic arrest with topical hypothermia (LV temperature 16°C) for 1 hour. To increase the safety of 1 hour of hypothermic arrest, we tested the effects of a) membrane stabilization (procaine HC1) (5 dogs), b) cardioplegia (500 cc of 4°C KC1, glucose, insulin, THAM, plasma, albumin) (6 dogs) and c) reperfusion (just before unclamping) with 500 cc blood buffered to pH 7.8 (5 dogs). In 6 dogs, we prolonged cross clamping to 2 hours by combining membrane stabilization, cardioplegia (replenishing 100ml each 20 min.) and pH 7.8 reperfusion. We measured regional coronary flow (microspheres), LV O₂ uptake, compliance (intraventricular balloon) and performance (isovolumetric curves) before and 30 minutes after arrest.

Results: The deleterious effects of 1 hour of ischemic arrest with topical hypothermia (LV compliance fell 53% ± 6*^ŧ, LV performance fell 43% ± 3*) were improved substantially by membrane stabilization alone, cardioplegia alone, and pH 7.8 reperfusion alone; postischemic values did not, however, return to normal. In contrast, 2 hours of cross clamping with combined membrane stabilization, cardioplegia and physiologic reperfusion resulted in 1) highest LV flows (150 ± 21 cc/100 gm/tnin*), 2) most favorable flow distribution (endo/epi 2.0 ± 0.3*), 3) greatest LV 02 uptake (0.06 ± 0.01cc/100 gm/beat*), 4) best LV compliance (87% ± 5 recovery*), and 5) normal (100% recovery*) post-ischemic function.

Conclusions: We conclude that combining membrane stabilization, multi-dose cardioplegia and physiologic reperfusion allows aortic cross clamping in the normal heart for up to 2 hours with as much safety as if the coronaries were perfused continually with oxygenated blood.

* = p<0.01 ŧ = ±SEM

INTERMISSION - VISIT EXHIBITS

*By invitation

17. Haemodynamic Evaluation of Left Ventricular Bypass Using a Homologous Cardiac Graft

JACQUES G. LOSMAN*, ALAN G. ROSE* and CHRISTIAAN BARNARD*,

Cape Town, South Africa,

Sponsored By: THOMAS D. HARTLEY, Gainesville, Florida

A valid criticism of orthotopic cardiac transplantation for irreversible left ventricle disease is that a normal or slightly diseased right ventricle is removed, and that a number of patients in terminal cardiac failure will not tolerate orthotopic transplantation due to excessively elevated pulmonary resistance.

To overcome problems due to severe pulmonary hypertension, an operation was devised in which the donor heart is used to bypass the right and left ventricle of the recipient heart left ‘in situ'. The functional efficacy of the donor heart was assessed in 50 baboons after inducing left ventricle failure by ligation of the left anterior descending coronary artery l ½ cm. from its origin and creating severe supra-aortic stenosis (peak systolic gradient of 80 to 100 mm Hg.). Haemodynamic studies were performed during selective fibrillation of the recipient heart and during synchronous and sequential pacing. It was found that volume load, ventricular compliance and contractility were the major determinants of the recipient and donor heart function. After-load changes played a lesser role.

It was found that the recipient heart ejection fraction and maximal total cardiac output were significantly improved by sequential pacing with optimalised delays. Low mortality, good donor heart function and prolonged survival were obtained despite lethal damage to the recipient heart (100% controls died).

Right and left ventricular bypass transplantation minimised recipient heart post-infarction arrhythmias, reduced myocardial necrosis area and allowed tolerance of severe supra-aortic stenosis. It is, therefore, a useful therapeutic variant of orthotopic cardiac transplantation and has been used successfully in seven human patients.

*By invitation

18. Prognostic Indices for Survival During Post-Cardiotomy IABP Pumping: A Simple Method of Scoring with Left Ventricular Assist Device Implications

JOHN C. NORMAN, DENTON A. COOLEY, STEPHEN R. IGO*,

C. WAYNE HIBBS*, J. GRAEME BENNETT* and

JOHN M. FUQUA*, Houston, Texas

Intraaortic balloon pumping has gained acceptance as a valuable adjunct in weaning patients from cardiopulmonary bypass. From Sept. 30, 1975 - Sept. 30, 1976, we have utilized IABP in 75 patients. Sixty-five (81%) were male. There were 33 (44%) survivors; 29 were male. The mean duration of IABP support was 55.4 ± 58hrs.

To clarify prognoses during IABP support, we have analyzed: 1) hemodynamics [cardiac index & mean pulmonary capillary wedge pressure]; 2) degree of pharmacologic support (reflected by systemic vascular resistance); & 3) renal blood flow (reflected by urinary output) in 25 surviving and nonsurviving patients during IABP support over a total of 54.6 days. Each data point was obtained each hour for each variable, stored, retrieved, analyzed, assigned a relative score of 0-4 & summed with a modified Hewlett-Packard 5690B computerized catheterization system with a video monitor and terminal.

Results: Survivors had IABP support for 103 i 28 hours; nonsurvivors had support for 25 ± 13 hours. During the initial 12 hours, survivor scores were 8.0 ± 1.9 and nonsurvivors were 5.4 ± 3.0 (N.S.). Survivors' scores increased from initial values of 8.0 ± 1.9 during the initial 12 hours to 11.6 ± 1.5 during the final 12 hours (p<0.01). During the final 12 hours, survivors' scores were significantly higher (11.6 ± 1.5) than nonsurvivors (4.8 ± 2.9), p

Serial monitoring and scoring of post-cardiotomy IABP patients allows prediction of the outcome. Patients with initial scores of 6.0 or less for 12 or more hours, appear unsalvageable, short of implantation of a left ventricular assist device. The latter has proven to be an order of magnitude more effective than IABP during early clinical evaluations.

11:15 A.M. Address of Honored Speaker

PROFESSOR CHARLES DUBOST

Paris, France

*By invitation