Single-clamp technique does not protect against cerebrovascular accident in coronary artery bypass grafting.

OBJECTIVES: By potentially avoiding the embolic consequences of a side-biting aortic clamp, the single-clamp technique may decrease cerebrovascular accidents in coronary artery bypass grafting. However, this theoretical superiority in stroke prevention has not been conclusively demonstrated and use of this technique may lead to adverse myocardial effects due to longer cross-clamp times. In this study, we sought to determine if the single-clamp technique prevents postoperative stroke in clinical practice. METHODS: Of 607 consecutive isolated coronary bypass operations completed over a 3 year period, 301 (50%) were performed by one surgeon using exclusively the single-clamp technique and 306 (50%) were performed by a second surgeon using exclusively the two-clamp technique. Postoperative adverse events were retrospectively compared between these two groups. RESULTS: There were no differences between groups in terms of postoperative stroke (1.7% single-clamp vs. 2.0% two-clamp, P=0.78), hospital mortality (2.7% single-clamp vs. 1.6% two-clamp, P=0.38), or perioperative myocardial infarction (2.6% single-clamp vs. 0.7% two-clamp, P=0.052). The two-clamp technique was not a significant predictor of stroke by logistic regression analysis (P=0.72). CONCLUSIONS: We conclude that there are no statistically significant differences between clamp techniques with regard to stroke prevention or myocardial protection. We find no compelling evidence for surgeons successfully utilizing one technique to change to the other.

Free radial artery grafts: surgical technique and results.

In the search for alternative conduits, the use of radial artery (RA) grafts has found renewed interest. This study sought to evaluate prospectively the perioperative morbidity, including the postoperative complications in the donor forearm, and mortality in the routine use of RA grafts in coronary artery bypass surgery. Data were obtained prospectively on 200 consecutive patients who underwent coronary revascularization using at least one RA graft from January 1995 to April 1997. The mean age of the patents was 61.9+/-10.5 years (mean+/-standard deviation [SD]). The RA was obtained from one forearm in 197 patients and both forearms in 3 patients. Two patients (1%) required exploration for donor site hematomas, 4 patients (2%) had temporary perioperative dysesthesias in the region of the lateral cutaneous nerve of the forearm, and none had donor site wound infection. Two patients (1%) had a myocardial infarction with electrocardiographic changes in the areas grafted by the RA in the immediate postoperative period, indicating graft failure. The two deaths in the series were due to comorbid factors. Our data suggest that the RA is a safe and suitable conduit for coronary revascularization, and it provides good clinical results. Long-term follow-up of these patients is necessary to confirm the patency of RA conduits. Free RA grafts have the potential for use in other areas of surgery where a conduit is necessary for revascularization procedures.

Reoperative mitral valve surgery via right thoracotomy: decreased blood loss and improved hemodynamics.

BACKGROUND AND AIMS OF THE STUDY: Reoperative mitral surgery via sternotomy can be associated with significant complications, including excessive blood loss and injuries to the heart, great vessels and patent coronary artery grafts. The right antero-lateral thoracotomy offers excellent exposure with less risk from re-entry. MATERIALS AND METHODS: Between 1982 and 1992, 221 patients had repeat mitral valve procedures at our institution. Fifteen of these 221 underwent mitral valve replacement via right thoracotomy. Indications for surgery in each group included bioprosthetic valve failure, paravalvular leak and bacterial endocarditis. Fifteen patients having reoperative mitral valve surgery via right thoracotomy approach were compared with a control group of 33 patient who underwent surgery via repeat sternotomy. All thoracotomy patients underwent mitral replacement or repair with ventricular fibrillation without aortic cross-clamping. Operative time, cardiopulmonary bypass time, requirement for inotropic support, blood loss within the first six postoperative hours, number of blood units transfused, length of ICU stay, days to discharge, and 30-day survival were compared between the two groups. In addition, the preoperative PaO2/FiO2 (P/F) ratio was evaluated as a prognostic indicator. RESULTS: Bypass time (162 +/- 43 min thoracotomy group vs. 131 +/- 34 min sternotomy group), operative time (389 +/- 100 min thoracotomy group vs. 450 +/- 25 min sternotomy group), ICU stay (6 +/- 8 days thoracotomy group vs. 5 +/- 6 days sternotomy group), P/F ratio (352 +/- 142 thoracotomy group vs. 423 +/- 108 sternotomy group), and 30-day survival (93% thoracotomy group vs. 91% sternotomy group) were not found to be significantly different between groups. Of great significance was the reduction in blood loss (277 +/- 152 ml thoracotomy vs. 651 +/- 504 ml sternotomy, p < 0.05) and blood transfused (2.0 +/- 1.7 units thoracotomy vs. 6.5 +/- 3.3 units sternotomy, p < 0.01) with the thoracotomy approach. Also of significance was a reduction in frequency with which significant inotropic support was needed to separate from cardiopulmonary bypass (26% vs. 63%, p < 0.05). Despite decreased access to the heart for de-airing maneuvers, no cerebrovascular events whatsoever were noted with the thoracotomy approach. CONCLUSION: The right thoracotomy approach is recommended for redo mitral valve surgery. Despite these advantages, severe pulmonary dysfunction (as indicated by a P/F ratio less than 300) correlated with a prolonged hospital course in four thoracotomy patients; such patients should have repeat sternotomy.

Neonatal correction of transposition of the great arteries: the Connecticut experience.

The treatment of transposition of the great arteries, a common congenital cardiac defect, has undergone significant development. Prior to 1989 a surgical approach which repaired the transposition at the atrial level (Senning's operation), but did not restore normal anatomy, was the procedure of choice. Since 1989 a surgical approach that restores normal anatomy (Jatene's arterial switch) has been followed. Forty-four patients have been corrected since 1979 (N = 26 Senning's operation, N = 18 arterial switch). The arterial switch patients are corrected at an earlier age, have a longer, more complex operation without a significant increase in operative mortality, intensive care, or duration of hospitalization. The prevalence or frequency of normal ventricular function and normal sinus rhythm is significantly increased over the repair at the atrial level. The frequency of pulmonary stenosis is increased. The duration of follow-up for these patients is significantly shorter than for those with atrial level repair.

Comparison of 180-degree and 360-degree skeletal muscle nerve cuff electrodes.

Use of skeletal muscle for cardiac augmentation is a promising technique for treatment of end-stage cardiac failure. An electrode woven through the latissimus dorsi that recruits nearby nerve fibers is commonly used to pace skeletal muscles both in clinical practice and in the laboratory. A proximally placed nerve cuff electrode offers potential advantages in improved recruitment of muscle fibers and low threshold for stimulation. We tested the effectiveness of a nerve cuff electrode passed directly about the proximal thoracodorsal nerve. Our report looks at the efficacy of nerve cuff electrode stimulation and compares electrical and histologic characteristics of a 180-degree wrap of the thoracodorsal nerve to a 360-degree wrap in dogs over 3 months. Threshold voltage at the commonly used pulse width of 200 microseconds was typically in the range of 400 to 600 mV for each electrode after 3 months. Statistical analysis revealed no significant difference (p < 0.05) in threshold voltage or current between the 180-degree and 360-degree nerve cuff electrode either at acute evaluation or after 3 months. Even contraction of latissimus dorsi was achieved with all implants. Adenosine triphosphatase staining revealed 100% conversion of type II to type I fibers in all stimulated muscles. Histologic examination of the thoracodorsal nerve and latissimus dorsi muscle revealed no abnormalities grossly or by light microscopy. Thus, a carefully applied nerve cuff electrode is an atraumatic, effective method for skeletal muscle stimulation. The 180-degree and 360-degree nerve cuff configurations are equally effective.

Fenestrated Fontan operation with delayed transcatheter closure of atrial septal defect. Improved results in high-risk patients.

Ten patients, each with two or more risk factors for morbidity and death, underwent a fenestrated Fontan procedure in which a 4 to 6 mm circular fenestration was left between the systemic and pulmonary venous chambers. None died; a similar group of high-risk patients without fenestration had a mortality rate of 2 of 8. Patients with fenestration had significantly less drainage from the chest tube, less need for inotropic support, and shorter intensive care and hospital stays than did patients without fenestration. Comparison with a group of low-risk patients undergoing the Fontan operation showed no statistical difference in these postoperative parameters. Fenestrations were closed in all 10 patients at from 9 days to 6 months after operation by means of the transcatheter clamshell occluder device. Two patients had left pulmonary artery balloon angioplasty and three patients had other atrial communications closed with additional clamshell devices. During short-term follow-up periods averaging 18 months, all patients were clinically well; however, one patient with mitral atresia required reoperation for obstruction between the left atrium and the tricuspid valve, not related to the clamshell device. These data indicate that fenestration may be one method of achieving lower morbidity and mortality rates among high-risk patients undergoing the Fontan procedure.

Mechanical circulatory support decreases neurologic complications in the treatment of traumatic injuries of the thoracic aorta.

The surgical treatment of traumatic injuries of the thoracic aorta is controversial because a number of technical approaches have been recommended. Despite the technique employed, spinal cord ischemia continues to be a persistent problem. Nineteen patients with confirmed aortic injuries secondary to blunt trauma were treated at the Yale-New Haven (Conn) Medical Center from 1984 to 1991. The patients were analyzed in two groups: group 1 (n = 10) underwent repair using mechanical circulatory support and group 2 (n = 9) underwent repair without mechanical circulatory support. Sixteen patients survived. Three patients died of complications of multiple trauma. The groups were comparable with respect to aortic cross-clamp time, preoperative systolic blood pressure, and Injury Severity Score. Three patients in the nonmechanical support group developed neurologic complications (P less than .05). No patient in the mechanical support group had a neurologic complication. We believe that mechanical circulatory support reduces the incidence of neurologic complications following traumatic injuries of the thoracic aorta and should be used whenever clinically feasible.

Anomalous left coronary artery from the main pulmonary trunk: physiologic and clinical importance of its association with persistent ductus arteriosus.

Anomalous left coronary artery (ALCA) from the pulmonary trunk presents in early infancy with a clinical picture of failure to thrive, congestive heart failure (CHF), angina-like episodes, and mitral insufficiency. These manifestations which are due to myocardial ischemia may change in the presence of an associated lesion. We present a case and review two previous reports of a patent ductus arteriosus (PDA) associated with this anomaly. Although signs and symptoms are not as clear due to the less impaired coronary perfusion and the presence of a PDA, the presence of mitral insufficiency should raise the possibility of an anomalous coronary artery and, therefore, a cardiac catheterization and angiocardiography are recommended in anticipation of reparative surgery.

Heart-lung transplantation: initial experience in New England.

Between May 1988 and June 1989, five combined heart-lung transplants were performed. There were two males, age 16 and 19 years, and three females age 33, 34, and 19 years. Three patients had primary pulmonary hypertension, one had cystic fibrosis, and the fifth had doxorubicin-induced cardiomyopathy with associated pulmonary hypertension. All patients were severely restricted in functional capacity and were oxygen-dependent. Four grafts were distantly procured (ischemic times 1:15, 2:35, 2:45, 3:45); one was procured on-site (ischemic time 0:58). Four of five grafts functioned well (PO2 on FIO2 30% postoperatively: 102, 120, 180, and 129 torr). One graft (distantly procured with an ischemic time of 1:15) showed total failure of oxygenation secondary to fluid overload during donor surgery; the recipient could not be weaned from cardiopulmonary bypass. All patients were extubated 24 to 30 hours postoperatively. Rejection episodes have been infrequent and all have been successfully treated with pulse steroids. Four of the five patients are alive and well with normal cardiopulmonary function and normal functional capacity 15, 12, 8, and 6 months after surgery. Heart-lung transplantation is an effective therapy for properly selected patients with end-stage cardiopulmonary disease resulting from a variety of primary disorders.

Atrial natriuretic factor: response to cardiac operation.

Patients who undergo cardiopulmonary bypass experience derangements of complement activation, prostaglandin metabolism, and catecholamine secretion, which have all been posited to explain postoperative fluid retention and paroxysmal hypertension. Atrial natriuretic factor, a hormonal peptide released by the cardiac atria, regulates vascular volume by increasing sodium excretion and decreasing vasomotor tone and catecholamine synthesis. We examined its possible response to cardiopulmonary bypass in 23 patients (18 having cardiopulmonary bypass and, as a control group, five having thoracotomy) who underwent serial blood sampling to measure plasma atrial natriuretic factor levels before, during, and after operation. Thoracotomy alone had no effect on atrial natriuretic factor levels before, during, and after operation. Patients with cardiac valve lesions who had a higher incidence of arrhythmias and congestive heart failure showed elevated preoperative atrial natriuretic factor values (p less than 0.05). Normally, atrial natriuretic factor release is directly related to atrial filling pressure, but all patients having cardiopulmonary bypass revealed a paradoxical rise of atrial natriuretic factor during cardiopulmonary bypass (p less than 0.01) and a lack of correlation between atrial filling pressure and atrial natriuretic factor secretion in the early postoperative period. The atrial natriuretic factor response to pulmonary wedge pressure began to normalize 24 hours after operation. The unique reaction of this recently discovered cardiac hormone to cardiopulmonary bypass suggests its possible role in the pathophysiologic response to cardiac operation.

Implantable extra-aortic balloon assist powered by transformed fatigue-resistant skeletal muscle.

The hypothesis tested in this study was whether a skeletal muscle could be transformed to be fatigue resistant, to be used to power an implantable extra-aortic balloon assist device, and therefore to provide dynamically significant cardiac assistance. Eight dogs underwent implantation of an Itrel pacemaker to stimulate the thoracodorsal nerve over 8 to 18 weeks and transform the latissimus dorsi muscle. Biopsies of these muscles confirmed near complete (up to 98%) transformation into fatigue-resistance type I muscle fibers, identified by the adenosinetriphosphatase histochemical stains. Biochemical assays showed conversion of myosin isoforms to that of myocardial V3 phenotype, decreased activity of anaerobic glycolytic marker, and increased activity of aerobic enzyme marker, which indicated greater resemblance of such muscle to the myocardial fibers. In four dogs, the optimal stimulation parameters of such muscles in response to a burst stimulator, which synchronizes and summates the muscle contraction, were studied and compared with the contralateral, nontransformed muscle. Fatigue tests confirmed the marked fatigue resistance of the transformed muscle. In four dogs, a 100 ml balloon was placed beneath the transformed latissimus dorsi muscle and connected to the thoracic aorta with a Dacron graft. By means of the optimal burst-stimulating parameters identified above, the latissimus dorsi muscle was stimulated to contract during diastole, compressing the balloon to achieve diastolic augmentation while allowing the balloon to fill during systole. A 39% increase (p less than 0.001) in the "subendocardial viability index" (diastolic pressure-time index/tension-time index) was obtained as calculated from the left ventricular and ascending aortic pressure tracings. We conclude that the skeletal muscle can be transformed to resemble myocardium, which can generate sufficient force to provide hemodynamically significant and clinically relevant counterpulsation.

Perioperative Holter monitoring and computer analysis of dysrhythmias in cardiac surgery.

In order to increase the accuracy and efficiency of studying perioperative dysrhythmias, 52 patients undergoing cardiac surgery were fitted preoperatively with a Holter monitor adapted for intraoperative recording, and the preoperative, intraoperative and early postoperative cardiac electrical activities were classified with a digital computer. Forty patients underwent coronary artery bypass grafting (CABG), eight had valve replacements, and four had combined procedures. The results showed the following: (1) high incidence of various dysrhythmias occurring during anesthesia induction and thoracotomy prior to aortic cross-clamp; (2) high incidence of continued atrial activity during cardioplegia; (3) lack of correlation between peak serum CPK-MB levels and dysrhythmias; and (4) a higher overall incidence of dysrhythmias in valve patients. Adapting the Holter monitor technique for cardiac surgery can solve the problem of observer vigilance inherent to such a study using a human "monitor watcher," and facilitate the accurate analysis of the vast amount of data obtained. This is important in quantitating the electrophysiologic effects of various perioperative interventions, such as the anesthetic agents, beta-blockers, calcium antagonists, and cardioplegic solutions.

Effects of abdominal aneurysmectomy, aortoiliac bypass grafting and angioplasty on male sexual potency: a prospective study.

The preoperative frequency and postoperative status of male sexual potency was studied prospectively in 46 patients who underwent abdominal aortic aneurysmectomy, aortoiliac and aortofemoral bypass grafting, or percutaneous transluminal angioplasty of the iliac artery. The patients with aortic aneurysms were older; approximately half of them were potent. The frequency of impotence was highest in patients who underwent aortoiliac bypass, and correlated well with their low penile to brachial pressure index. Patients who had angioplasty had more localized lesions, a higher penile to brachial pressure index and the lowest rate of impotence. Postoperatively, 13% of the patients regained nocturnal erection and 10% became functionally potent (defined as the ability to achieve penetration). The improvements were similar in bypass and angioplasty patients. No patient experienced deterioration in sexual potency and all showed a markedly improved thigh to brachial pressure index postoperatively. Routine aortoiliofemoral artery angiograms were of limited value in predicting the status and outcome of sexual potency in this series of patients.

Myocardial protection: heparin-induced free fatty acid elevation during cardiopulmonary bypass and its prevention.

Elevated serum free fatty acids (FFA) adversely affect the hypoxic or ischemic myocardium by impairing cardiac function, decreasing contractility, and increasing arrhythmogenicity . Heparin, an anticoagulant used routinely in cardiac surgery, elevates circulating FFA. The purpose of this study was to determine the magnitude of FFA elevation in cardiac surgery patients and to establish, in dogs, a dose-response of FFA to heparin and to test whether glucose-insulin-potassium (GIK) solution could prevent heparin-induced rise in FFA. In 52 patients undergoing cardiopulmonary bypass (CPB), serial blood samples were obtained for FFA determination before and after heparin (300 IU/kg) administration. Then in seven normal dogs, heparin at a dose of 80 or 300 IU/kg was given. In another group of five dogs either GIK solution or NaCl were infused, while intravenous heparin (300 IU/Kg) injection was given. Each dog acted as its own control. It was found that there was a twofold increase in circulating serum FFA after heparin administration during cardiac surgery in patients, reaching the toxicity level of greater than 0.80 meq/liter. One-third of these patients had elevations of FFA level above the arrhythmogenic threshold of greater than 1.20 meq/liter. In the canine experiments low-dose heparin (80 IU/Kg) resulted in milder elevations of FFA for a shorter duration. Dogs given saline and high-dose heparin (300 IU/Kg) had responses similar to those seen in human patients undergoing cardiac surgery, while GIK abolished the elevation of serum FFA in response to high-dose heparin, eventually reducing FFA to below preheparin levels.

Synchronously stimulated skeletal muscle graft for myocardial repair. An experimental study.

We studied the feasibility of augmentation of impaired myocardium with synchronously paced skeletal muscle grafts. The short contractile period of skeletal muscle required development of a new stimulator to ensure that the pedicle graft contraction would simulate that of the myocardium. In four dogs each, rectus and diaphragmatic muscles were wrapped around a balloon and electrically stimulated in synchrony with the electrocardiogram, varying stimulation currents and frequency of discharge during systole. For this purpose, a prototype hybrid stimulator was developed which senses the cardiac R wave and modulates the electrical output to the skeletal muscle by delivering a train of impulses of varying frequencies within the systolic intervals. The contraction characteristics in response to such stimulation were similar in rectus and diaphragmatic muscles, but the former developed higher maximum tensions because of the greater muscle bulk. Square-wave output was found to be more effective than sine-wave stimulation, and a single stimulating electrical pulse of 40 msec duration produced a maximum tension of 60 mm Hg lasting for 120 msec, whereas a train of 4 pulses within a 320 msec period was able to achieve a maximum tension of 100 mm Hg lasting nearly 400 msec, the latter approximating that of the myocardium. In six other dogs, the rectus muscle pedicle graft was used to replace a segment of the left ventricle (25.5% +/- 2.1% of left ventricular mass) excised under cardiopulmonary bypass. Left ventricular isometric contraction was studied using a left ventricular balloon with stimulators turned on and off. Significant augmentations of left ventricular maximum tension (+19.3% +/- 2.5%, p less than 0.001, paired t test) and left ventricular contractility (+38.3% +/- 9.4%, p less than 0.001) were achieved when the skeletal muscle grafts were stimulated. Thus, in this preliminary study, skeletal muscle graft properly oriented and stimulated is able to augment the left ventricular isometric contractile function after significant loss of left ventricular myocardial mass.