Emergency pulmonary autograft mitral valve replacement in a child.

Mitral valve replacement in small children imposes significant clinical difficulties because of the relatively small mechanical prosthetic valves required and the need for lifelong anticoagulation therapy. A child weighing 10.4 kg presented with thrombosis of her 19-mm mechanical mitral prosthesis 4 weeks after implantation despite appropriate oral anticoagulation therapy. An emergency mitral valve replacement with a pulmonary autograft was successfully performed with encouraging short-term results.

Reoperative homograft right ventricular outflow tract reconstruction.

BACKGROUND: Homografts are implanted in the right ventricular outflow tract (RVOT) of children, with the knowledge that reoperation might be required. We reviewed 14 years of homograft RVOT reconstruction to assess the feasibility of homograft replacement and to determine risk factors for homograft survival. METHODS: From February 1985 through March 1999, 223 children (age 5 days to 16.9 years) underwent primary RVOT reconstruction with an aortic or pulmonary homograft. Of these, 35 patients underwent homograft explant at the implanting hospital with insertion of a second homograft from 2 months to 13.3 years after the first implantation. The primary operation and reoperation patient groups were compared with regard to incidence of early death, late death, homograft-related intervention without explant, and homograft explant. RESULTS: Actuarial survival and event-free curves for initial and replacement homografts were not significantly different. Univariable analysis was performed for the following risk factors: weight (p < 0.0001), age (p < 0.003), homograft diameter (p < 0.0001), homograft type (p < 0.01), surgery date (not significant [NS]), gender (NS), Blood Group match (NS), and type of distal anastomosis (NS). Multivariable analysis of significant univariable risks revealed small homograft diameter to be a significant risk factor (p < 0.001) for replacement. CONCLUSIONS: The RVOT homografts eventually require replacement. Patient and homograft survival for replacement homografts is similar to primary homografts. Reoperative homograft RVOT reconstruction is possible, with reasonably low morbidity and mortality.

Utility of extracorporeal membrane oxygenation for early graft failure following heart transplantation in infancy.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) is widely used for postcardiotomy cardiogenic shock in children. However, the efficacy of ECMO for early post-heart transplant graft failure in infants has not been reported. Our aims were to determine: (1) the utility of ECMO in infants with severe donor-heart dysfunction, (2) predictors for requiring ECMO, and (3) the long-term outcome of surviving ECMO patients. METHODS: All infants (age < 6 months at listing) undergoing heart transplantation were reviewed. Diagnostic categories were hypoplastic left heart syndrome (HLHS) and non-HLHS (complex congenital heart disease and cardiomyopathies). Continuous and categorical comparisons were by Wilcoxon's rank sum test and Fisher's exact test respectively. RESULTS: 14 (12 HLHS, 2 non-HLHS) of 63 (46 HLHS, 17 non-HLHS) infants were placed on ECMO. Ten patients (71%) were successfully weaned from ECMO and 8 (57%) were discharged alive. All ECMO hospital survivors remain alive (mean follow-up 36.2 +/- 21.4 months, range 13.1-77.6 months). Mean duration of ECMO support was 68 hours in weaned patients vs 144 hours (p = 0.19) in nonweaned patients, and 64 hours in survivors vs 123 hours (p = 0.35) in nonsurvivors. ECMO deaths were due to sepsis (n = 3), intractable pulmonary hypertension (n = 2), and intracranial bleed (n = 1). Neurologic deficits occurred in 2 survivors. Median ICU and hospital stays for ECMO survivors were 29 and 33 days vs 7 (p = 0.0003) and 9 (p = 0.0004) days for non-ECMO patients. Age listed, age transplanted, wait time, body weight, donor/recipient weight ratio, total ischemia time, and diagnosis did not predict the need for ECMO. CONCLUSIONS: (1) ECMO is useful for post-heart transplant circulatory support in infants with early graft failure. (2) All survivors were weaned in fewer than 4 days. (3) Three-year survival of ECMO hospital survivors has been high, but neurologic complications are prevalent.

Early and late morbidity in patients undergoing pulmonary resection with low diffusion capacity.

BACKGROUND: We sought to determine whether low diffusion capacity of the lung to carbon monoxide (DLCO) is a predictor of high postoperative mortality and morbidity after major pulmonary resection and whether major pulmonary resection in patients with low DLCO results in substantial long-term morbidity. METHODS: Sixty-two major pulmonary resections were performed in 61 patients with low DLCO (DLCO < or = 60% predicted for pneumonectomy or bilobectomy; < or = 50% predicted for lobectomy). Contemporaneously, 262 other patients underwent 263 major pulmonary resections (group II). Long-term morbidity was assessed in subsets of patients with low (n = 24) and high (n = 22; DLCO > 60% predicted) DLCO. RESULTS: The hospital mortality rates were equivalent (4.8% low DLCO versus 4.9% group II), whereas respiratory complications were more frequent in patients with low DLCO (18% versus 9.5%; p = 0.05). In the subgroup analyses, patients with low DLCO had more hospitalizations for respiratory compromise and worse median dyspnea scores. Analysis of patients with substantial dyspnea revealed an association with extended pulmonary resection and postoperative radiation therapy in patients with low DLCO. CONCLUSIONS: Patients with low DLCO underwent major pulmonary resection with a low mortality rate and an acceptable, but increased, respiratory complication rate. Long-term respiratory morbidity was increased in patients with low DLCO; however, the extent of pulmonary resection and the use of postoperative radiation therapy may have contributed to the development of dyspnea in these patients.

Systolic arterial pressure recovery after ventricular fibrillation/flutter in humans.

Although the elective induction of cardiac arrest for implantable defibrillator insertion under general anesthesia is widely used, the hemodynamics of recovery of arterial blood pressure after cardiac arrest is not well-defined. Accordingly, the time course of recovery of systolic arterial pressure was studied in seven patients during the repetitive induction of ventricular fibrillation (n = 6) or ventricular flutter (n = 1). The mean number of episodes of cardiac arrest was 7 +/- 2, and the mean drop in systolic pressure was 84 +/- 16 mmHg. The mean recovery time for systolic pressure was 10 +/- 6 seconds, the average systolic pressure recovery rate was 13 +/- 14 mmHg/sec, and the mean percent systolic pressure recovery was 94% +/- 9%. A negative logarithmic relation was found to exist between the rate of systolic arterial pressure recovery and the duration of ventricular fibrillation or flutter with a correlation coefficient of 0.68 to 0.97 (P < 0.05) in five of the seven patients. A linear relation between the time for systolic pressure recovery and duration of asystole was also defined. These results are consistent with the view that prolongation of ventricular fibrillation or flutter increases the duration of arterial pressure recovery through a negative effect on left ventricular contractility. Increased understanding of these relations may lead to increased safety of implantable defibrillator insertion.

Thoracoscopic placement of implantable cardioverter-defibrillator patch leads in sheep.

BACKGROUND: A thoracoscopic technique was developed for the placement of commercially available implantable cardioverter-defibrillator (ICD) patch leads in sheep. METHODS AND RESULTS: Small ICD patch leads (13.5 cm2, A-67) were placed thoracoscopically in sheep (n = 5) that had survived coronary artery ligation from a previous experiment. The technique used three small incisions in the left chest. After lysis of adhesions, the ICD patch lead was introduced through a mediastinoscope. The ICD patch lead was secured in the extrapericardial position with surgical clips placed in the four corners of the ICD patch lead. After 2 weeks, a median sternotomy was performed, and ICD patch leads were reexamined for positioning. Extensive fibrosis was noted to adhere the ICD patch lead to the pericardium. The surgical clips were found intact in all animals without noticeable migration of patch lead position. There was no mortality related to ICD patch lead placement, and estimated blood loss was less than 30 mL without use of cautery. CONCLUSIONS: Commercially available ICD patch leads may be reliably and safely placed with minimal patch migration in sheep using thoracoscopic techniques.

Prevention of acute regional ischemia with endocardial laser channels.

Laser myocardial revascularization has been shown to reduce mortality and infarct size after left anterior descending coronary artery (LAD) ligation in dogs. It has not been shown to improve myocardial contractility in acute ischemia. In this study a holmium-yttrium-aluminum garnet laser (wavelength, 2.14 microns) was used to create nontransmural myocardial channels from the endocardial surface in the ischemic regions of the canine left ventricle. Twelve mongrel dogs (6 controls, 6 laser myocardial revascularizations) underwent 90 minutes of LAD ligation followed by 6 hours of reperfusion. The ischemic region was determined by methylene blue injection during brief LAD occlusion. Laser myocardial revascularization averaged three channels per square centimeter in the ischemic region created using 12 J/channel (600 mJ/pulse, 10 Hz) before LAD ligation. Contractility was assessed from regional preload recruitable stroke work (RPRSW), using pairs of segment length ultrasonic transducers in the ischemic and the nonischemic regions. Two-dimensional echocardiography corroborated with segmental length findings. In control dogs, the ischemic region was dyskinetic during LAD ligation and reperfusion. Dyskinesis of the ischemic region during systole produced negative values for regional stroke work, and RPRSW was considered zero. In 4 of 6 laser-revascularized dogs, RPRSW remained positive in the ischemic region. Two dogs had intermittent dyskinesis. The difference between laser-revascularized and control dogs in ischemic region RPRSW was significant (p < 0.01 by Fischer's exact test).(ABSTRACT TRUNCATED AT 250 WORDS)

Factors confounding impedance catheter volume measurements in vitro.

The impedance catheter allows continuous measurement of ventricular volume. External influences have been described as causing parallel shifts in impedance-measured volumes; however, factors affecting impedance measurements in a nonparallel manner have not been fully characterized. Accordingly, an impedance catheter was placed inside a latex balloon into which known volumes of normal saline solution were injected. Conductive and nonconductive materials were individually placed within the balloon. Impedance was measured with materials touching (T) or not touching (NT) the catheter. Impedance-measured volumes were plotted versus actual volumes. Compared with the line of identity (LID), a statistical difference (p < 0.05) was found in the slopes in the presence of metallic objects only. These included a pacing lead (T, NT) (mT = 1.32m mNT = 1.29 versus mLID = 1.00), titanium (T) (mT = 1.68 versus mLID = 1.00), and aluminum (NT) (mNT = 0.72 versus mLID = 1.00). These changes in slope indicate nonparallel effects on impedance that confound the ability of the impedance catheter to determine volumes in vitro. These observations imply that serial calibration of both the slope constant (alpha) and the intercept (parallel conductance) of impedance may be necessary for in vivo measurements of ventricular volume based on impedance in the presence of metallic objects.

The implantable defibrillator: an electronic bridge to cardiac transplantation.

BACKGROUND: Sudden cardiac death (SCD) is common among patients awaiting heart transplantation. Medical management of SCD may fail due to lack of efficacy or adverse side effects. The implantable cardioverter-defibrillator (ICD) may extend patient survival until a donor heart is available. METHODS AND RESULTS: We reviewed 16 patients listed for transplantation between November 1988 and October 1991 who underwent ICD implantation for ventricular arrhythmias refractory to medical management. Mean age was 51.4 +/- 11.4 years (range, 19-66 years), mean ejection fraction was 15.4 +/- 3.0% (range, 10-21%), and underlying cardiomyopathy was ischemic (12 patients), valvular (one patient), or dilated (three patients). There was no mortality from ICD insertion. Fourteen patients were discharged before transplantation, and two patients remained in the hospital until transplantation. Twelve patients underwent transplantation after a mean of 155.7 +/- 113.7 days (range, 3-319) on the transplant list. The ICD delivered shocks for tachyarrhythmia associated with near syncope in 15 of 16 patients. ICD shocks numbered > 10 in five patients, 5-9 in three patients, and 1-4 in seven patients. There was no morbidity or mortality attributed to patch electrode removal. CONCLUSIONS: We conclude that the ICD can be implanted with minimal morbidity in transplant candidates, allowing the patients to be ambulatory and to leave the hospital while awaiting heart transplantation. In patients at risk of SCD, the ICD is an effective electronic bridge to transplantation.

Effect of AICD patch electrodes on the diastolic pressure-volume curve in pigs.

Although the automatic implantable cardioverter defibrillator (AICD) is effective against malignant ventricular arrhythmias, the effects of AICD patches on left ventricular diastolic properties have not been defined. Accordingly, extrapericardial (group E, n = 5) or intrapericardial (group I, n = 6) AICD patches were implanted through a median sternotomy in 11 anesthetized pigs. Six weeks later, using a left thoracotomy, the hearts were arrested with hypothermic cardioplegia. A balloon catheter was inserted into the left ventricle through the aortic root, and pressure-volume curves were measured before and after sequential removal of patches and pericardium. A dense intrapericardial fibrotic reaction in group I was not present in group E. Normalized left ventricular filling volumes in group E were significantly larger at pressures of 5.1 to 10, 15.1 to 20, and 20.1 to 28 mm Hg compared with group I (p less than 0.05). We conclude that intrapericardial AICD patches adversely affect left ventricular diastolic pressure-volume relations and recommend that AICD patches be placed in the extrapericardial location clinically whenever possible.