Evolution of a Non-Invasive Method for Providing Assistance to the Heart

The primary function of the ventricular chambers of the heart is to provide the proper volume of blood to the entire body that fulfills its energy requirements under a wide variety of normal and pathologic settings. If the ventricles are unable to perform this task properly, and the functions of the body deteriorates despite optimal medical management, mechanical methods are utilized to either complement or replace the pumping function of the cardiac ventricles. This presentation will describe the evolution of a non-invasive method of assisting the circulation called “counterpulsation,” and the current state of the development of an “External Left Ventricular Assist Device” (XLVAV). In this method, in the first part of the cardiac cycle, when the heart is relaxed, cardiac diastole, the device exerts a positive pressure external to the lower extremities. This increases coronary artery blood flow and cardiac output. Then when the ventricle contracts, cardiac systole, the device exerts a negative pressure, thus drawing blood away from the heart into the lower extremities, resulting in a reduction of the work and energy requirement of the left ventricle. Experimental and clinical data will be presented that describe the following successive stages of development: 1. The initial experience of Osborn in 1962 using a pressure suit and air actuation was tested in a canine model and in normal volunteers, but was not successful since sufficient pressure was not exerted on the vascular bed of the lower extremities. 2. The initial experimental experience of Birtwell and Soroff in a canine model in 1962 using water as the actuating medium. 3. The construction of a device by Birtwell with cuff-type actuators around the legs, thighs and buttocks that were inflated with water. The cuffs had rigid shells to allow pressure to be exerted to the limbs. The device was successful in increasing diastolic pressure and coronary blood flow and was used successfully in a multicenter study as an initial treatment of patients with acute myocardial infarctions. However, since the device could only apply positive pressure, it could not be used to reduce systolic pressure. 4. The device was then modified to also apply negative pressure during cardiac systole, a major step forward, and tested in a multicenter study in patients with cardiogenic shock following myocardial infacrtions with an impressive increase in the survival rate from 15% to 45%. However, the device presented logistical and patient movement problems. 5. The next evolution in the device design was the use of air to inflate the actuator cuffs. This represented a significant breakthrough, and has been successfully used in the treatment of angina pectoris by increasing coronary blood flow and the promotion or creation of collateral circulation in the myocardium. The serious shortcoming of this device is that is cannot produce negative pressure during cardiac systole, i.e., the only means of assisting the left ventricle in patients with Congestive Heart Failure. 6. The device to be described can apply negative as well as positive pressure to the lower extremities using air as the actuating medium. The device is mobile and compact, and should be effective in the treatment of patients with Congestive Heart Failure both in the hospital setting and in the home, Acute Myocardial Infarction as well as Angina Pectoris.

Enhanced external counterpulsation as an adjunct to revascularization in unstable angina

Enhanced external counterpulsation (EECP) is an effective noninvasive treatment for chronic stable angina. Despite intensive risk factor modification, a patient required two surgical coronary revascularizations and seven multivessel angioplasties over a 26-month period, demonstrating recurrent unstable angina and persistent thallium perfusion defects despite revascularization. Post EECP, angina was relieved, thallium defects were resolved and the patient has remained asymptomatic for 36 months.

Can angiographic findings predict which coronary patients will benefit from enhanced external counterpulsation?

Enhanced external counterpulsation is an effective treatment for chronic angina. Theoretical considerations predict greatest benefit in patients with at least 1 patent conduit in this group of 50 patients (all of whom improved clinically). Improvement in radionuclide stress perfusion imaging was seen in 80% of treated patients and was inversely related to extent of coronary disease.

Improved sternal closure using steel bands: early experience with three-year follow-up

BACKGROUND

Use of stainless steel wires in median sternotomy closure is at times associated with serious complications. In view of this, the efficacy and safety of a stainless steel band designed for fixation and approximation of the sternum in cardiothoracic procedures was evaluated in a prospective, randomized study.

METHODS

Forty-eight patients undergoing open heart operations that involved a median sternotomy were studied. Group I (n = 21) was closed with four to six steel bands, and group II (n = 27) with six to eight standard stainless steel wires. The average age of the patients and the risk factors predisposing to dehiscence were similar in both groups.

RESULTS

One postoperative death occurred in each group due to cardiac failure. In group I, the mean length of the postoperative hospital stay was 10.2 +/- 1.76 days (+/- 2 standard errors), whereas in group II the mean was 13.9 +/- 3.4 days (+/- 2 standard errors). Banded patients complained less of postoperative pain, although statistical significance was not achieved. No problems arose in either group during the 3-year follow-up.

CONCLUSIONS

The steel bands, compared with wires, provided not only effective fixation, but a reduction in both postoperative pain and postoperative hospital stay. The band is now being studied in a larger group of patients to evaluate the incidence and type of complications associated with its use, as well as length of postoperative hospital stay.

Collagenase ointment and polymyxin B sulfate/bacitracin spray versus silver sulfadiazine cream in partial-thickness burns: a pilot study

A multifaceted approach that involves early debridement and control of infection is critical to successful and rapid burn wound healing. This pilot study was conducted in 15 adult patients with burns to assess the usefulness of early enzymatic debridement with a combination of collagenase ointment and polymyxin B sulfate/bacitracin spray versus silver sulfadiazine cream in partial-thickness burns. Combination treatment with collagenase and polymyxin B sulfate/bacitracin resulted in significantly shorter time to achieve a clean wound bed than silver sulfadiazine (median 6 vs 12 days; p = 0.0012) and significantly more rapid wound healing than silver sulfadiazine (median 10 vs 15 days; p = 0.0007). These results are encouraging and justify implementation of a larger, multicenter, comparative study.

Hospital reported complications of laparoscopic cholecystectomy among Medicare and Medicaid patients

The purpose of this study was to initiate a hospital-based case review of all laparoscopic cholecystectomies performed on Medicare and Medicaid patients in New York State in 1991 where there were one or more complications. Another purpose was to facilitate efforts by hospitals to monitor the performance of laparoscopic cholecystectomy through an educational process of data-sharing. There were 2,940 Medicare and 1,108 Medicaid cholecystectomies in New York State in 1991. Of these, 351 (11.9%) Medicare and 107 (9.7%) Medicaid patients were reported as having complications. The complication rate for Medicare patients was slightly lower than that observed (15.8%) in an epidemiologic study of Medicare patients in New York State who underwent laparoscopic cholecystectomy during the period January 1, 1990-June 30, 1991. Both of these observed rates for Medicare patients are higher than the mean 6.0% complication rate reported for open cholecystectomy in the literature. These increased rates may in part be due to age related risk factors present among Medicare patients. The absence of age related risk factors may also largely account for the lower laparoscopic cholecystectomy complication rate (9.7%) observed among Medicaid patients. The complication rate of 9.7% for Medicaid patients is similar to rates reported in other recent studies. The 11.9% complication rate for Medicare patients is higher than that reported in other recent studies. However, careful patient selection, the absence of age related risk factors, and greater surgical experience may account for the lower complication rates reported in some published series. Overall, the coding of complications was found to be accurate. The coding of laparoscopic cholecystectomy was found to be slightly flawed.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of enhanced external counterpulsation in the treatment of angina pectoris

Eighteen patients with chronic angina despite surgical and medical therapy were treated with an improved system of enhanced external counterpulsation (EECP) (1 hour daily for a total of 36 hours). Patients underwent a baseline treadmill thallium-201 stress test. After EECP treatment, a thallium stress test was repeated for the same exercise duration. One week after treatment, patients also underwent a maximal stress test. All patients improved in anginal symptoms and generally decreased antianginal medications, with 16 obtaining complete relief from angina. Pre- and post-thallium stress testing performed for the same duration showed complete resolution of ischemic defects in 12 patients (67%), reduction in the area of ischemia in 2 (11%), and no change in 4 (22%). Thus, a decrease in myocardial ischemia was observed in 14 patients (78%; p less than 0.01). The exercise duration of maximal stress testing after EECP significantly improved from 8.14 +/- 0.71 to 9.72 +/- 0.77 minutes (p less than 0.005), although the double product did not change significantly. Analysis of these 2 tests in the subgroup of 14 patients with improvement in thallium studies showed significant increases in both exercise duration (8.58 +/- 0.66 to 10.44 +/- 0.59 minutes; p less than 0.001) and double product (21,827 +/- 2,044 to 24,842 +/- 1,707 mm Hg.beats/min; p less than 0.01). The improvement in reperfusion defects and increase in exercise duration are reflections of improved perfusion to ischemic regions of the myocardium. EECP uses additional thigh balloons and sequenced balloon inflation, effecting a significant increase in diastolic augmentation over previously available methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Single dose cephalosporin prophylaxis in high-risk patients undergoing surgical treatment of the biliary tract

During June 1985 through October 1986, 292 patients considered to be at high risk for having postoperative complications develop underwent cholecystectomy and were evaluated in a multicenter, randomized, prospective, double-blind study. Risk factors included age greater than 70 years, acute cholecystitis within the previous six months, obstructive jaundice, obesity and diabetes mellitus. One gram of cefamandole was administered intravenously to 144 patients and 148 patients received 1 gram of cefotaxime intravenously 30 minutes prior to skin incision. Culture-proved bactibilia was found in 55 patients and 11 of the patients had choledocholithiasis. Of the risk factors considered to place patients at high risk for postoperative infectious complications, obesity and acute cholecystitis proved to be the more common. However, age greater than 70 years, diabetes mellitus and obstructive jaundice were more significant risk factors predisposing to bactibilia. The most common organisms isolated from the bile and gallbladder intraoperatively were Staphylococcus, Streptococcus and Klebsiella species along with enterococcus, Escherichia coli and diphtheroids. Clinically significant postoperative infections occurred in eight patients, including six patients in the cefamandole group and two patients in the cefotaxime group. Antibiotic concentrations were measured in the serum, muscle, subcutaneous fat, gallbladder and bile, with cefamandole showing statistically significant greater concentrations in bile, gallbladder and muscle tissue. There was no statistical significance between the postoperative infection rates, total period of hospitalization or total hospital charges for each group. Therefore, there is no significant advantage between a single prophylactic dose of cefamandole versus cefotaxime for high-risk patients undergoing biliary tract operation.

Inguinal herniorrhaphy. Reduced morbidity by service standardization

To ascertain if service specialization and procedure standardization would improve the complication rate of inguinal herniorrhaphy, the results of all inguinal herniorrhaphies performed during a 3-year period by board-certified general surgeons who also performed a variety of other procedures common to the field of general surgery, assisted by general surgical residents (group B, 390 patients), were compared in the same institution with the results of inguinal herniorrhaphy when performed during 3 years under protocol by a Hernia Service directed by a senior faculty member assisted by junior surgical residents (group C, 442 patients). Group B patients had essentially no follow-up until they reappeared for care at the Hernia Service, whereas patients in group C achieved an 82% 7-year follow-up. The infection and recurrence rates of group C patients (0.45% and 0.9%, respectively) were significantly better than those of group B patients (5.9% and 4.6%, respectively). These results suggest that in our institution, the concentration of patients with hernias in a hernia service, manned by a specialized surgeon, produced better short- and long-term results than those obtained by general surgeons not dedicated to the field of hernia repair. Further studies will be necessary to confirm these findings.

The effect of trifluoperazine, a calmodulin antagonist, on the growth of normal and malignant epidermal keratinocytes in culture

Calmodulin, a cytoplasmic calcium binding protein, is present in concentrations two- to four-fold higher in malignant cells compared to normal cells. In an effort to learn the significance of these elevated levels, we examined the effect of calmodulin blockage on the growth of normal and malignant keratinocytes in vitro. The level of calmodulin in SCC12.B2, a line of keratinocytes derived from an epidermal squamous cell carcinoma (SCC), was about 3.5 times greater than in normal, human newborn foreskin keratinocytes. When exposed to trifluoperazine (TFP), an inhibitor of calmodulin, cell growth was reduced primarily in the cultures of normal keratinocytes. This growth inhibition resulted from two changes in the replicating population of cells, namely an increase in cell cycle length and an increase in rate of cell cycle withdrawal. Cell cycle withdrawal is the irreversible arrest of the cell cycle and is an early event in keratinocyte terminal differentiation. There was no measurable effect on the cell cycle time or withdrawal rate in SCC12.B2. The increased resistance to growth arrest in SCC cells may be a consequence of the elevated level of calmodulin in these cells.

The effect of growth-promoting agents on replication and cell cycle withdrawal in cultures of epidermal keratinocytes

Epidermal keratinocytes grow in culture to form a stratified squamous epithelium. These cultures contain a replicating as well as a terminally differentiating population and undergo surface desquamation. Epidermal growth factor (EGF) and cholera toxin are usually employed as growth-promoting agents because they reduce the population doubling time; that is, the period required to increase the total cell number twofold. There are three ways in which this reduction in population doubling time could be achieved: (a) the time for one cell cycle or the cell cycle length may be shortened; (b) the number of cells that withdraw from the cell cycle and terminally differentiate may be reduced; or (c) the number of cells that desquamate into the medium over a set period of time may be reduced. We have explored these possibilities in growing cultures of epidermal keratinocytes using a newly developed double-label assay. This assay gives a measure of both cell length and cell cycle withdrawal. Results show that the growth enhancement induced by EGF and cholera toxin can be attributed primarily to a reduction in cell cycle withdrawal and, to a lesser degree, to a reduction in cell cycle length. EGF and cholera toxin have no significant effect on the rate of desquamation. A linear correlation was noted between cell cycle lengths and withdrawal, suggesting an interconnection between the rate of cell renewal and the likelihood of undergoing terminal differentiation.

The treatment of generalized peritonitis by closed postoperative peritoneal lavage. A critical review of the literature

Thirty-nine studies of closed postoperative peritoneal lavage were reviewed, including four prospective, randomized studies, eight nonrandomized comparative studies, and 27 noncomparative studies. Mortality rates and abscess rates were determined for various subsets of patients. Despite the large number of studies performed, the therapeutic value of this procedure remains unknown. It is unlikely that further noncomparative or nonrandomized studies will yield useful information. There remains a need for a large-scale, prospective, randomized study to evaluate closed postoperative peritoneal lavage. Smaller prospective, randomized studies can contribute meaningfully if data on the specific causes of peritonitis, severity of disease, and patient age and chronic health status are provided in the form of widely used and well-validated stratification systems.

Herniorrhaphy in the elderly. Benefits of a clinic for the treatment of external abdominal wall hernias

Elective abdominal herniorrhaphy carries morbidity and mortality rates of 26 percent and 1.5 percent, respectively, in patients over 65 years of age. These figures climb to 55 percent and 15 percent during emergent surgery. Our purpose was to investigate if standardization of treatment could improve such results. Our program stressed centralization of care in a hernia clinic; early operation of patients at risk of incarceration; optimization of underlying systemic disorders by consultative services; operation under local anesthesia; preoperative, operative, and postoperative protocol; and continuity of care by senior personnel. Over a 4 year period, we have performed 241 abdominal herniorrhaphies in patients over 65 years of age (median age 71.5 years old) who exhibited an 84 percent incidence of significant preoperative systemic disorders. Since the inception of our program, our rate of emergent operation has decreased significantly from 7 percent to 2 percent (chi-square less than or equal to 0.05). Our rate of systemic complications after elective operation was 1.2 percent and 0 after emergent operation. These data are statistically better than those reported in the literature (chi-square less than or equal to 0.05). These results suggest that the creation of a hernia clinic significantly improves the care of herniated patients.

Current status of external counterpulsation

This article traces the development of external counterpulsation from its beginnings to the present. Initially, counterpulsation was carried out by cannulating the femoral artery. The hemodynamic goals were to reduce the afterload of the left ventricle, and to raise or augment the diastolic pressure. This gave rise to the term "counterpulsation." The intra-aortic balloon is capable of producing these salutary effects because of its proximity to the outlet of the left ventricle. The same hemodynamic effects can be obtained by external counterpulsation. However, one must produce a negative pressure during cardiac systole, and ensure that this is applied to the lower extremities. The only clinical study in which this was done was in the treatment of patients in cardiogenic shock by Soroff and colleagues. The results of the clinical studies reviewed are all suggestive of benefits derived from external counterpulsation in a variety of clinical settings. These studies suggest the following avenues for improvement in the equipment used to carry out external counterpulsation: 1. Inclusion of the vascular bed of the buttocks to be subjected to the external pressures, as advocated by Zheng. 2. Inclusion of a negative pressure blanket, as advocated by Soroff. 3. Further investigation of graded-sequential external counterpulsation, using the buttocks and negative pressure. 4. Application of external counterpulsation earlier in cardiogenic shock and for at least 4 hours in acute myocardial infarction. Our evaluation is that this method has not been studied in a way that demonstrates its full potential. We feel that it is on the threshold of being shown to be useful in all of the clinical settings reviewed, and we hope that the necessary equipment will be created to allow investigators to establish its proper place in our therapeutic armamentarium.

Unusual extraperitoneal presentations of diverticulitis

Extraperitoneal presentations of complicated diverticular disease are unusual. The initial clinical presentations of these extraperitoneal manifestations have been described in the perineum, scrotum, buttock, hip, joints, thigh, lower extremities, mediastinum, and neck. These presentations render the diagnosis difficult and may lead to the delay of the proper therapy. The purpose of this report is to call attention to these unusual extraperitoneal presentations of complicated diverticular disease to describe the routes of spread and to present a case in point. Reviewing the literature, we have concluded that these unusual presentations occur more commonly in women and the elderly, that a delayed diagnosis significantly increases the mortality rate, and that the most common site of an extraperitoneal presentation is in the area of the hip.

Successful fibrinolytic therapy for superior vena cava thrombosis secondary to long-term total parenteral nutrition

Thrombosis of the superior vena cava and other major central veins is an unusual and infrequent complication of total parenteral nutrition. When it does occur, it may be life threatening and prompt therapy is indicated. A case of superior vena cava thrombosis secondary to an indwelling Broviac catheter for long-term parenteral nutrition is presented, which was successfully treated with Streptokinase with reestablishment of flow through the catheter and veins.

Randomized prospective study of the comparative efficacy of spectinomycin and gentamicin in urinary tract infections

A prospective, randomized study was undertaken in 32 hospitalized patients with urinary tract infections to compare the efficacy of spectinomycin versus gentamicin. Spectinomycin was found to be of equal efficacy if not more efficacious in eradicating Escherichia coli, Klebsiella and Proteus mirabilis in our patient population. No significant side-effects were noted. A review of the literature with emphasis on the use of spectinomycin in infections other than anogenital gonorrhea is made.

Choice of route for central venous cannulation: subclavian or internal jugular vein? A prospective randomized study

The clinical need for central venous cannulation has been well established. The usual route for catheter placement is by either the subclavian or internal jugular vein. No randomized, prospective evaluation has been yet conducted to determine which of these approaches, if either, is better with respect to reliability, placement, and frequency of nonseptic complications. One hundred consecutive patients requiring elective central venous cannulation were randomized to either the subclavian or internal jugular route. Successful venipuncture and catheter passage were significantly more common with the subclavian route, and in the absence of special clinical situations, it appears to be the route of choice.

An analytical approach to the determination of optimal phasing for external counterpulsation

An inhomogeneous linear one-dimensional mathematical model is constructed as a conceptual approach to the study of the effects of External Counterpulsation (ECP) on the pressure and flow at the root of the aorta. The optimal operation of ECP is defined by two conditions: (1) minimization of the mean systolic pressure; and (b) maximization of the ratio of diastolic area over systolic area under the total pressure curve. The phase shift of the external pressure is determined so as to satisfy these two requirements. It is demonstrated within our approximation that with a given magnitude of external pressure, the phase shifts that satisfy these two requirements are the same. These phase shifts are linear functions of the systolic fraction of the total cardiac period, and depend on the time for the external wave to travel from the site of application up the vascular bed to the root of the aorta, plus the reflection contributions. Even though these results are derived from a simple model far from the complexity of the actual vasculature, the basic concepts would remain valid even if more complex mathematical treatments would have been used.

The evolution of counterpulsation techniques

Assisted circulation techniques are an outgrowth of extracorporeal pump oxygenator systems developed in the mid 1950s. But the differences in physiology of total perfusions and of parital perfusions for assisting circulation delayed the clinical application of the intra-aortic balloon. The problems and risks in providing circulation assistance and the approaches used to overcome them are discussed. The various counterpulsation techniques are described and data presented to demonstrate the increased survival in patients with myocardial infarction and cardiogenic shock.

Computer analysis of external counterpulsation by use of a nonlinear mathematical model of the cardiovascular system

A pressure system externally applied to the limbs of a patient has been proven effective in assisting circulation in animal and clinical studies. In this study a nonlinear mathematical model of the cardiovascular system is utilized to determine the effectiveness of high-frequency components in the external pressure waveform. The development of the model, the method of analysis, and the results acquired with the model are presented in this report, demonstrating its suitability for the study of external counterpulsation.

Efficacy of intravenous clindamycin and methicillin in gram-positive soft tissue infections

In a comparative study on a general surgical service, intravenous clindamycin phosphate or methicillin was used to treat a variety of soft tissue infections due to gram-positive organisms, chiefly staphylococci. The infections were rated according to severity, responsible organisms, and site of the infection. Excellent or good clinical and bacteriologic responses were obtained with both clindamycin and methicillin as adjuncts to basic surgical therapy in these soft tissue infections. The adverse effects of each drug were detailed, and were comparable. Clindamycin phosphate is a satisfactory substitute for methicillin in soft tissue infections secondary to gram-positive organisms.