The implanted defibrillator: relation of defibrillating lead configuration and clinical variables to defibrillation threshold.

Forty-two defibrillating lead systems for the automatic implantable defibrillator were implanted and tested in 41 patients. Two basic lead configurations were used: 1) spring-patch, consisting of a transvenous superior vena cava spring electrode as the anode and an apical or left lateral ventricular patch electrode (either small [13.9 cm2] or large [27.9 cm2]) as the cathode; and 2) patch-patch, consisting of an anterior right ventricular patch as the anode and a posterior left ventricular patch as the cathode. Of the 42 lead systems, 10 were spring-patch and 32 were patch-patch combinations. The defibrillation threshold for the patch-patch combinations (9.8 +/- 6.5 J, mean +/- standard deviation) was significantly (p less than 0.01) lower than that for the spring-patch combinations (19.1 +/- 10.3 J). Subgroup analysis revealed the lowest defibrillation thresholds for patch-patch combinations with at least one large patch. Total surface area of defibrillating leads was strongly negatively correlated with the defibrillation threshold (p less than 0.005). Analysis of the relation of clinical variables to defibrillation threshold revealed that only amiodarone therapy was independently associated with a significantly (p less than 0.05) higher defibrillation threshold. Thus, surface area of the defibrillating leads is a critical determinant of the defibrillation threshold for the implanted defibrillator. Patch-patch lead systems with at least one large patch may provide an increased safety margin for defibrillation. Conversely, amiodarone therapy is associated with higher defibrillation thresholds and may decrease the margin of safety.

Hemodynamic and hormonal abnormalities in canine aortic coarctation at rest and during exercise.

This study was designed to determine the hemodynamic and hormonal consequences of aortic coarctation at rest and during treadmill exercise. Twelve normal adult dogs served as controls. In eight dogs coarctation was created within 1 week of birth by banding the aorta just proximal to the ductus ligament, thereby fixing luminal diameter at 1 to 2 mm. Studies were performed 18 months after operation. Vascular pressures were monitored proximal and distal to the coarctation, cardiac output and regional blood flow were evaluated with radioactive microspheres and blood samples were collected for determination of hormone levels and blood gases. At rest, systolic pressure in the proximal aorta was 130 +/- 12 mm Hg (mean +/- SD) in the control group and 167 +/- 16 mm Hg in dogs with coarctation (p less than 0.01). During exercise at a level that doubled heart rate and cardiac index, mean aortic pressure increased by 11 and 31% (p less than 0.01) in the control and the coarctation group, respectively. Mean distal aortic pressure increased by 8% during exercise in control dogs but decreased by 29% in dogs with coarctation. Exercise decreased flow to the kidneys and the large intestine in the coarctation group. Plasma norepinephrine concentrations were greater in the coarctation group than in control dogs at rest; during exercise, plasma norepinephrine, epinephrine and renin activity increased in both groups, but to a greater degree in the group with coarctation. These results confirm an abnormality in renal and gut perfusion in experimental coarctation and suggest that this may be related to a decline in perfusion pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Infected left atrial myxoma with bacteremia simulating infective endocarditis.

A 58-year-old man had intermittent fever of eight months' duration following a dental extraction. There were no abnormal cardiac auscultatory findings. Multiple blood cultures yielded Streptococcus mutans. Treatment for infective endocarditis was initiated; however, an echocardiogram suggested the presence of a left atrial myxoma. The diagnosis was confirmed by angiography and the infected tumor was removed successfully. Differentiating features between left atrial myxoma and mitral valve endocarditis may not be obvious clinically, and bacteremia does not preclude atrial myxoma as a diagnostic possibility. We therefore suggest that all cases of infective endocarditis be evaluated by echocardiography to elucidate lesions such as large vegetations or left atrial myxoma, both of which may require urgent operative intervention.

Mitral valve prolapse requiring surgery. Clinical and pathologic study.

The clinical, hemodynamic, surgical, and pathologic findings in 30 patients who required mitral valvular surgery and who had a preoperative diagnosis of mitral valve prolapse were reviewed. The mean age of the patients was 59.5 years; 28 patients were over 45 years of age and 10 were over 60 years. Surprisingly, 20 were males. A long history of systolic murmur was common, whereas symptoms of heart failure were of abrupt onset. At the time of surgery, a local holosystolic murmur typical of mitral regurgitation was present, although a mid- to late systolic click was not heard in any of the patients. Electrocardiographic abnormalities were present in all patients, with 13 patients demonstrating atrial fibrillation. Only four patients had a normal heart size radiographically. Echocardiography confirmed the radiographic findings, in that 27 patients demonstrated left atrial and ventricular enlargement. All 29 patients undergoing cardiac catheterization and angiography demonstrated a prolapsing mitral valve with severe regurgitation. Surgical and pathologic examination revealed findings characteristic of a myxomatous valve in all patients, with 19 also demonstrating ruptured chordae tendineae. This study demonstrates that heart failure requiring valvular surgery occurs in a subset of patients with mitral valve prolapse. In this subset, males predominate and most are over 50 years of age. These patients may be asymptomatic for many years, demonstrating mild to moderate mitral valvular regurgitation, before heart failure develops.

Aspirin or dipyridamole individually prevent lipid accumulation in primate vein bypass grafts.

Although platelet inhibition with both aspirin and dipyridamole is widely prescribed for patients with coronary artery bypass grafts, data are lacking to prove that combined drug therapy has greater efficacy in preserving graft integrity than either drug given independently. Thus, the ability of combined vs single drug therapy to reduce cholesterol and apolipoprotein-B accumulation were compared in autologous cephalic veins grafted into femoral arteries of 23 stump-tailed macaque monkeys. Ten monkeys were studied in 2 phases. They were treated with aspirin (80 mg/day) during 1 phase and with dipyridamole (50 mg/day) during the other phase. Five monkeys received aspirin plus dipyridamole in combination and 8 received no medication and served as controls. When grafts were removed 3 months after insertion cholesterol and apolipoprotein-B concentrations in grafts were similar for groups treated with aspirin, with dipyridamole, and with the drugs combined, and in each of the treated groups these concentrations were significantly reduced compared with grafts from untreated control monkeys. Cholesterol and apolipoprotein-B concentrations in grafts from the treated groups were similar to concentrations in normal ungrafted veins, whereas cholesterol and apolipoprotein-B levels in grafts from control monkeys were significantly greater than those in ungrafted veins (250% and 925% of normal, respectively). Our findings reaffirm the ameliorative effect of anti-platelet drugs in reducing the accumulation of lipid in vein bypass grafts and indicate that the efficacy of aspirin or dipyridamole given individually equals that of the combination of these drugs in this subhuman primate model. The relation of the lipid-lowering effect of these agents to their antithrombotic effect is uncertain.

An improved method of topical cardiac hypothermia.

Current methods of myocardial protection usually employ together with topical hypothermia by pericardial lavage. Pericardial lavage is inconvenient, inconsistent, and noisy: it wastes blood: it cannot cool the right ventricle effectively. We use a new myocardial protection jacket to cool the heart during operation other than simple coronary bypass procedures. Myocardial temperatures are maintained at 7 degrees to 14 degrees C indefinitely without reinfusion of cardioplegia solution. The jacket is a more convenient and much more effective method of obtaining profound topical hypothermia.

Intra-aortic balloon counterpulsation for cardiac support during noncardiac operations.

Major noncardiac surgery is a serious hazard to patients with advanced coronary disease. Perioperative infarction is common, and preliminary coronary bypass is often unwarranted. We suggest that the use of the intra-aortic balloon pump (IABP) for perioperative support of such patients makes perioperative infarction unlikely and permits otherwise hazardous operations. Three patients with advanced coronary disease (unstable angina in two) had major thoracotomies for lung masses without cardiac complications. This management plan has wider implications for other noncardiac surgical problems in such patients, particularly for mandatory operations wuch as relieving intestinal obstructions.

Trans--pulmonary artery repair of ventricular septal defect associated with congenitally corrected transposition of the great arteries.

This report documents successful trans-pulmonary artery repair of ventricular septal defect (VSD) in 2 patients with congenitally corrected transposition of the great arteries, one patient having associated subpulmonic stenosis. In selected cases, the method of repair that is described offers significant advantages over techniques employing transventricular or transatrial access to the VSD.

Effects of postischemic left ventricular pressure-volume unloading on contractile recovery and myocardial blood flow in the regionally stunned canine heart.

OBJECTIVE: Myocardial stunning remains a clinical problem without definitive therapy. This study tested the hypothesis that mechanical therapy with a ventricular assist device would accelerate recovery of contractility in stunned myocardium by increasing the postischemic myocardial blood flow. METHODS: Regional stunning was induced in dogs (25 kg) by 15 minutes of coronary occlusion and 180 minutes of reperfusion. One group (ventricular assist device; n = 10) was reperfused in conjunction with left ventricular unloading with a centrifugal-pump ventricular assist device. A second group (control; n = 8) underwent unmodified reperfusion. Hemodynamic and regional function data were acquired in all dogs with the heart in the working state before and during ischemia and after 180 minutes of reperfusion. Regional myocardial blood flow was measured at these same intervals and after 30 minutes of reperfusion, at which time the left ventricle was mechanically unloaded in animals with a ventricular assist device. RESULTS: Regional stunning was observed in all animals, but cardiogenic shock developed in none of them. After 180 minutes of reperfusion, animals with a ventricular assist device had greater systolic shortening in the risk segment than did control animals (11.5% +/- 2.8% vs 1.1% +/- 1.3%; P <.05) and had no differences in either the slope or x-axis intercept of regional preload recruitable stroke work relations compared with preischemic values. Differences in contractile recovery did not correlate, however, with postischemic myocardial blood flow. Hyperperfusion mediated by the ventricular assist device was not observed in either stunned or remote segments. CONCLUSIONS: Mechanical left ventricular unloading attenuates regional myocardial stunning within 3 hours in normotensive dogs, independent of effects on myocardial blood flow. The mechanism underlying this effect remains undefined, but these data support expanded use of mechanical therapy for stunned myocardium in clinical settings.

Mitral valve replacement in idiopathic hypereosinophilic syndrome.

Idiopathic hypereosinophilic syndrome is a rare systemic disease that can cause one form of endocardial fibrosis. Endocardial fibrous tissue with overlying thrombus formation in idiopathic hypereosinophilic syndrome leads to a restrictive cardiomyopathy that may produce mitral and/or tricuspid regurgitation. This report describes a patient with idiopathic hypereosinophilic syndrome who underwent mitral valve replacement and successful steroid therapy for an usually localized form of endocardial fibrosis.

Age-related changes in the ability of hypothermia and cardioplegia to protect ischemic rabbit myocardium.

Hypothermia combined with pharmacologic cardioplegia protects the globally ischemic adult heart, but this benefit may not extend to children; poor postischemic recovery of function and increased mortality may result when this method of myocardial protection is used in children. The relative susceptibilities to ischemia-induced injury modified by hypothermia alone and by hypothermia plus cardioplegia were assessed in isolated perfused immature (7- to 10-day-old) and mature (6- to 24-month-old) rabbit hearts. Hearts were perfused aerobically with Krebs-Henseleit buffer in the working mode for 30 minutes, and aortic flow was recorded. This was followed by 3 minutes of hypothermic (14 degrees C) coronary perfusion with either Krebs or St. Thomas' Hospital cardioplegic solution No. 2, followed by hypothermic (14 degrees C) global ischemia (mature hearts 2 and 4 hours; immature hearts 2, 4, and 6 hours). Hearts were reperfused for 15 minutes in the Langendorff mode and 30 minutes in the working mode, and recovery of postischemic function was measured. Hypothermia alone provided excellent protection of the ischemic immature rabbit heart, with recovery of aortic flow after 2 and 4 hours of ischemia at 97% +/- 3% and 93% +/- 4% (mean +/- standard deviation) of the preischemic value. Mature hearts protected with hypothermia alone recovered only minimally, with 22% +/- 16% recovery of preischemic aortic flow after 2 hours; none were able to generate flow at 4 hours. St. Thomas' Hospital solution No. 2 improved postischemic recovery of aortic flow after 2 hours of ischemia in mature hearts from 22% +/- 16% to 65% +/- 6% (p less than 0.05), but actually decreased postischemic aortic flow in immature hearts from 97% +/- 3% to 86% +/- 10% (p less than 0.05). To investigate any dose-dependency of this effect, we subjected hearts from both age groups to reperfusion with either Krebs solution or St. Thomas' Hospital solution No. 2 for 3 minutes every 30 minutes throughout a 2-hour period of ischemia. Reexposure to Krebs solution during ischemia did not affect postischemic function in either age group. Reexposure of immature hearts to St. Thomas' Hospital solution No. 2 caused a decremental loss of postischemic function in contrast to incremental protection with multidose cardioplegia in the mature heart. We conclude that immature rabbit hearts are significantly more tolerant of ischemic injury than mature rabbit hearts and that, unexpectedly, St. Thomas' Hospital solution No. 2 damages immature rabbit hearts.

Is protection of ischemic neonatal myocardium by cardioplegia species dependent?

Hypothermia combined with pharmacologic cardioplegia protects the globally ischemic adult heart, but this benefit may not extend to children, resulting in poor postischemic recovery of function and increased mortality. The relative susceptibilities to ischemia modified by hypothermia alone and by hypothermia plus cardioplegia were assessed in isolated perfused neonatal (3- to 4-day-old) rabbit and pig hearts. Hearts were perfused aerobically with Krebs buffer solution in the working mode for 30 minutes and aortic flow was recorded. This was followed by 3 minutes of hypothermic (14 degrees C) coronary perfusion with either Krebs or St. Thomas' Hospital cardioplegic solution No. 2 followed by hypothermic (14 degrees C) global ischemia (rabbits 2, 4, and 6 hours; pigs 2 and 4 hours). Hearts were reperfused for 15 minutes in the Langendorff mode and 30 minutes in the working mode, and recovery of postischemic aortic flow was measured. Hypothermia alone provided excellent protection of the ischemic neonatal rabbit heart, with recovery of aortic flow after 2 and 4 hours of ischemia at 91% +/- 4% and 87% +/- 5% (mean +/- standard deviation) of its preischemic value. Recovery after 6 hours of ischemia was depressed to 58% +/- 9% of its preischemic value. Ischemic neonatal pig hearts protected with hypothermia alone recovered 94% +/- 3% of preischemic aortic flow after 2 hours; none was able to generate flow after 4 hours. St. Thomas' Hospital solution No. 2 decreased postischemic aortic flow after 4 hours of ischemia in rabbit hearts from 87% +/- 5% to 70% +/- 7% (p less than 0.05, hypothermia alone versus hypothermia plus cardioplegia) but improved postischemic recovery of aortic flow in pig hearts after 4 hours of ischemia from 0 to 73% +/- 13% (p less than 0.0001, hypothermia alone versus hypothermia plus cardioplegia). This effect was dose related in both species. We conclude that the neonatal pig heart is more susceptible to ischemia modified by hypothermia alone than the neonatal rabbit and that St. Thomas' Hospital solution No. 2 improves postischemic recovery of function in the neonatal pig but decreases it in the neonatal rabbit. This species-dependent protection of the neonatal heart may be related to differences in the extent of myocardial maturity at the time of study.

Validity of cardiac output measurement by the thermodilution method in the presence of acute tricuspid regurgitation.

Evaluation of patients with acute tricuspid insufficiency may include assessment of cardiac output by the thermodilution method. The accuracy of estimates of thermodilution-derived cardiac output in the presence of tricuspid insufficiency has been questioned. This study was designed to determine the validity of the thermodilution technique in a canine model of acute reversible tricuspid insufficiency. Cardiac output as measured by thermodilution and electromagnetic flowmeter was compared at two grades of regurgitation. The relationship between these two methods (thermodilution/electromagnetic) changed significantly from a regression slope of 1.01 +/- 0.18 (mean +/- standard deviation) during control conditions to a slope of 0.86 +/- 0.23 (p < 0.02) during severe regurgitation. No significant change was observed between control and mild regurgitation or between the initial control value and a control measurement repeated after tricuspid insufficiency was reversed at the termination of the study. This study shows that in a canine model of severe acute tricuspid regurgitation the thermodilution method underestimates cardiac output by an amount that is proportional to the level of cardiac output and to the grade of regurgitation.

Atherogenic effect of barotrauma on in situ saphenous veins in monkeys.

The objectives of this study were to determine whether veins subjected to barotrauma in situ undergo lipid uptake and morphologic changes to the same extent as veins grafted into the arterial circulation. Saphenous veins in seven stump-tailed macaque monkeys were exposed bilaterally and were circumferentially dissected free from surrounding tissue only at isolated sites. Segments of the veins were distended for 1 minute at hydrostatic pressures of 125 or 350 mm Hg. An undistended segment served as control. A cephalic vein graft was interposed in the femoral artery for comparison with in situ veins. The animals were fed a diet that sustains plasma cholesterol levels of approximately 225 mg/dl. Saphenous veins and the cephalic vein grafts were explanted at 3 months for biochemical and histologic analyses. Cholesterol content in undistended saphenous veins was similar to that in veins distended at 125 or 350 mm Hg--105 +/- 15, 122 +/- 14, and 109 +/- 30 micrograms/100 mg wet tissue weight, respectively. Cholesterol content in cephalic vein grafts, 473 +/- 122 micrograms/100 mg, was greater (p less than 0.001) than in saphenous veins at all distention pressures studied. There was no difference among the distention pressures in the intimal fraction of saphenous vein wall, with the pooled value being 20% +/- 12%. This contrasted with the value of 59% +/- 11% in cephalic vein grafts (p less than 0.01). Endothelial coverage of the luminal surface in saphenous veins was similar among the levels of barotrauma, with the pooled value being 83% +/- 15%. Less of the lumen was covered with endothelium in cephalic vein grafts, 46% +/- 18% (p less than 0.01). Slightly more medial fibrosis was observed in cephalic vein grafts as compared with saphenous veins (p less than 0.05). These data demonstrate that barotrauma alone does not cause veins that remain in the venous system to undergo the lipid uptake or morphologic changes that occur in veins grafted into the arterial circulation in nonhuman primates.

Management of long-standing cardiocutaneous fistulas after resection of left ventricular aneurysms.

Cardiocutaneous fistulas arising from pledgets used in the closure of resected left ventricular aneurysms are rare but have serious implications. The case histories of four patients, each managed in a somewhat different manner, are presented. From this experience we recommend an aggressive approach to remove the infected pledgets once scar formation is complete and before erosion of the pledgets into the left ventricular cavity can occur.

Aspergillus terreus infective endocarditis on a porcine heterograft valve.

We present the first reported case of Aspergillus endocarditis occurring on a porcine heterograft prosthesis and discuss the literature regarding both Aspergillus endocarditis and endocarditis on a porcine valve. A 65-year-old man underwent aortic valve replacement with a porcine heterograft. Several weeks later he exhibited signs of infection and then of valve failure. Upon removal, the porcine valve substance was found to be grossly infiltrated and destroyed by the Aspergillus organism. The porcine valve has an excellent reputation of being resistant to infection and relatively easy to sterilize by medical management alone. Several surveys attest to the low incidence of endocarditis. Because of our experience with the destruction caused by Aspergillus, however, and because antimicrobials generally fail to eradicate this organism, we urge prompt operation to remove the heterograft valve involved with infection by this organism. The valve diseased with Aspergillus should be replaced with a mechanical prosthesis. In the aortic position, extra-anatomic replacement should be considered to facilitate eradication of periannular infection postoperatively.

The effect of ambient temperature on papaverine-induced relaxations in canine saphenous veins.

This study was designed to measure the effect of ambient temperature (25 degrees C) on papaverine-induced relaxations in canine saphenous veins. Segments of vein were suspended in water-jacketed tissue baths at 37 degrees C, and isometric tension was recorded. After equilibration, veins were preconstricted by a median effective dose of norepinephrine 2 x 10(-6) mol/L at either 25 degrees C or 37 degrees C. Consequent dose-dependent relaxations showed that papaverine (10(-7) to 10(-3) mol/L was three times more potent as a dilator at 37 degrees C than at 25 degrees C, with half-maximal relaxations occurring at 2.2 x 10(-5) mol/L and 6.4 x 10(-5) mol/L, respectively. A 10(-4) mol/L dose of papaverine completely relaxed veins at 37 degrees C, whereas veins at 25 degrees C never fully relaxed even at ten times the standard concentration. In addition, the time for half-maximal relaxation with a 10(-4) mol/L dose of papaverine averaged 40 minutes at 25 degrees C compared with 22 minutes at 37 degrees C; this is indicative of a reduced relaxation rate at the lower temperature. These data show that papaverine is a slower and less potent dilator of canine saphenous veins at 25 degrees C than at 37 degrees C. This may have implications for the use of papaverine in the operating room, where it is usually applied at ambient temperature to reduce vasospasm of the saphenous vein during coronary artery bypass procedures.

Depressed postoperative cardiac performance. Prevention by adequate myocardial protection during cardiopulmonary bypass.

Depressed postoperative myocardial performance (low output syndrome) requiring inotropic drugs or balloon counterpulsation is due to subendocardial ischemic damage. Before July, 1972, we needed inotropic drugs in 30 to 52 per cent of 189 patients undergoing coronary revascularization or aortic or mitral valve replacement in whom we used ischemic arrest, profound topical hypothermia, and ventricular fibrillation. The mortality rate ranged from 10 to 17 per cent. Our experimental studies show that morbidity and death in such cases are caused by ischemic injury to the heart resulting from inadequate myocardial protection during bypass. Based on these experimental studies, we have, since July, 1972, employed the following principles clinically: (1) Maintain beating empty heart whenever possible; (2) maintain adequate coronary perfusion pressure (less than 80 mm. Hg); (3) avoid extreme hemodilution; (4) avoid ventricular fibrillation; (5) avoid prolonged hypothermic arrest, limiting ischemic periods to less than 15 minutes; (6) repay myocardial ischemic oxygen debt with total (vented) bypass; and (7) optimize DPTI/TTI (supply/demand ratio) pre- and postoperatively. These principles were followed in 189 consecutive operations, and postoperative inotropic drugs were needed in only 12. The principles were violated in 4 of the 12 patients (6 per cent), and 5 others had identifiable causes of myocardial depression; low output syndrome was unexplained in only 3 patients (1.7 per cent).

Hyperkalemia in cardioplegic solutions causing increased cholesterol accumulation in vein grafts.

Hyperkalemic cardioplegic solutions are frequently infused through vein grafts during aorta-coronary bypass operations. Although some reports have suggested the potential for physical damage to grafts by such exposure, the effects of these solutions on graft atherogenesis have not been studied. We evaluated the influence of potassium and colloid content of cardioplegic solutions on graft cholesterol accumulation in our established animal model of graft atherogenesis. Fourteen cephalic vein grafts were interposed bilaterally in the femoral arteries of seven normolipemic stump-tailed macaque monkeys. Before grafting, each vein was distended at 350 torr for 1 minute with autologous blood. Half of each vein was then filled for 30 minutes with either balanced crystalloid solution or with balanced crystalloid plus albumin (5 mg/ml). The other half of the vein was filled with the same solution plus potassium chloride (27 mEq/L). Grafts were harvested at 12 weeks. Cholesterol content was significantly greater (p less than 0.01) in graft segments exposed to hyperkalemia than in their control counterparts. Onconicity had no effect on cholesterol content. In this animal model, prolonged exposure of vein grafts to hyperkalemic cardioplegic solutions caused increased lipid uptake. This finding may presage accelerated atheromatous degeneration.

Constrictive pericarditis associated with patch electrodes of the automatic implantable cardioverter-defibrillator.

A case of constrictive pericarditis intimately involving patch electrodes of the automatic implantable cardioverter-defibrillator is described. Typical clinical and hemodynamic findings for constrictive pericarditis were noted 15 months after lead installation. Additionally, chest x-ray examination revealed a severe crumpling deformity of the patch electrodes. Thoracotomy was performed and revealed marked fibrous reaction surrounding both surfaces of each patch electrode. Histologic examination revealed fibrous tissue with multinucleated giant cells, consistent with a foreign body reaction. The patient had complete resolution of signs and symptoms of constrictive pericarditis after removal of the patch electrodes and pericardial stripping. Constrictive pericarditis from implanted patch electrodes appears to be an uncommon complication of the automatic implantable cardioverter-defibrillator and should be considered in patients with one or more patch electrodes and other signs of constrictive pericarditis.