Malalignment-type ventricular septal defect in double-chambered right ventricle

Double-chambered right ventricle (DCRV) is commonly associated with ventricular septal defect (VSD). In this study, an assessment was made of the relevance of a malalignment-type VSD to hemodynamic and morphologic features in DCRV. During an 8.5-year period, 53 patients with DCRV were enrolled after study with echocardiography, catheterization, and angiography. Patients were divided into 2 groups: group I included 40 patients, aged 3.7 +/- 3.2 years, with a malalignment-type VSD; group II consisted of 13 patients, aged 8.6 +/- 2.7 years, without a malalignment-type VSD. History of congestive heart failure in infancy was present in 21 group I and 2 group II patients (53% vs 15%, respectively, p <0.05). The mean pulmonary-to-systemic flow ratio was significantly higher in group I than in group II (1.89 +/- 0.74 vs 1.14 +/- 0.21, respectively, p <0.05). The mean pressure gradient across the right ventricular outflow tract was lower in group I than in group II (41 +/- 16 vs, 73 +/- 33 mm Hg, respectively, p <0.05). Among 42 patients who had a series of echocardiograms recorded, progression of pressure gradient was evident in 35: 28 in group I and 7 in group II. A subaortic ridge was present exclusively in 29 group I patients (73%). Prolapse of the aortic valve was present in 26 (49%): 20 group I (50%) and 6 group II (46%) patients. Aneurysm formation of the septal defect was found in 17 (43%) and 7 (54%) group I and II patients, respectively. It can be concluded that a history of congestive heart failure was more common in DCRV patients with a malalignment-type VSD. Malalignment-type VSD is significantly associated with a larger pulmonary-to-systemic flow ratio and subaortic ridge.

Continuous monitoring of venous oxygen saturation in critically-ill infants

A 4-French gauge Opticath catheter, inserted into a neonate's right atrium through the right internal jugular vein, can be used to continuously monitor venous blood oxygen saturation in the right atrium. This method instantly detects subtle changes in cardiopulmonary function in small infants and neonates and enables the appropriate treatment to be given in cases of critical infantile and neonatal cardiopulmonary deterioration. This report discusses four neonatal and infantile patients who underwent continuous monitoring of venous blood oxygen saturation in the right atrium. Continuous monitoring allowed appropriate treatment to be given earlier compared to conventional monitoring methods of blood pressure and heart rate.

Color Doppler sonogrphy in differentiation between testicular torsion and epididymoorchitis: report of three cases

Clinical assessment of the testicular torsion and epididymoorchitis is inherently difficult. Inadequate clinical information may prevent differentiation testicular torsion from non-surgical condition. We reported 3 cases with symptoms of acute scrotal condition who had received color Doppler sonography. One man had epididymoorchitis and color Doppler sonography showed profusely increased blood flow in the region of epididymis and testis. Symptoms subsided with one week of medical treatment. Sonography correctly detected absence of testicular perfusion in 2 boys who had sugical exploration of the scrotum. Testicular torsions were confirmed by surgical findings. Absence or markedly decreased testicular blood flow which indicated testicular ischemia or infarction was easily identified. Conversely, hyperemia of the testis and/or epididymis is usually associated with inflammation However, incomplete torsion or detorsion may demonstrate normal testicular flow on color Doppler sonography. Color Doppler sonography provides early diagnosis of acute testicular torsion, and prevents unnecessary scrotal exploration.

Efficacy of ultrafiltration in removing inflammatory mediators during pediatric cardiac operations

BACKGROUND

Conventional and modified ultrafiltration was used in pediatric cardiac operations to reduce volume overload and total body water. The purpose of this study was to compare the efficacy of these techniques in removing inflammatory mediators during cardiopulmonary bypass.

METHODS

Fifty pediatric patients undergoing cardiac operations were randomized into a modified or conventional ultrafiltration group. Blood samples were obtained before and after ultrafiltration to assess the plasma concentrations of leukocyte elastase, tumor necrosis factor-alpha, interleukin-6, and interleukin-8.

RESULTS

Except for plasma concentrations of tumor necrosis factor-alpha in the modified ultrafiltration group, the plasma concentrations of all the mediators measured increased after ultrafiltration in both groups of patients. The volume of ultrafiltrate and the total amounts of tumor necrosis factor-alpha and interleukin-6 removed by ultrafiltration were significantly greater in the modified group. The concentrations of mediators in the ultrafiltrate and the ratio of ultrafiltrate to plasma concentrations of the mediators did not differ between the groups. Ultrafiltration was more efficient in removing tumor necrosis factor-alpha than the other mediators.

CONCLUSIONS

The efficacy in removing the inflammatory mediators generated during cardiopulmonary bypass did not differ between modified and conventional ultrafiltration.

Atrial compartment surgery for chronic atrial fibrillation associated with congenital heart defects

In three adult patients, two with atrial septal defect and one with Ebstein's anomaly, chronic atrial fibrillation was documented for 13, 21, and 3 years, respectively. Atrial compartment surgery was performed for ablation of the atrial fibrillation concomitant with repair of the cardiac defects. The operation was performed with traditional cardiopulmonary bypass and crystalloid cardioplegia myocardial protection. A U-shaped incision was made in the right atrium: a longitudinal incision 1 cm lateral and parallel to the sulcus terminalis, extending along the borders of the atrial septum to 3 cm (upper margin) and 1 cm (lower margin) distant to the tricuspid anulus. Cryolesions of the atrial isthmus between the upper incision margin and the tricuspid valve anulus were created at -60 degrees C for 180 seconds at a time. After the operation, all three patients had restored and maintained normal sinus rhythm during follow-up periods of 32, 16, and 3 months. Doppler echocardiography detected the recovery of atrial contractility in all three patients. Atrial compartment surgery is a simple and effective method for elimination of chronic atrial fibrillation associated with congenital heart defects.

Haematological variations of experimental pigs during biventricular assistance with impeller total heart

The impeller total heart was developed and published several years ago but its in-vivo evaluations could only be made recently. Originally, the device was designed for long-term implantation. As the first step, however, it was used this time in acute biventricular assistance, to demonstrate the blood compatibility of the pumps, and to demonstrate the feasibility of an impeller type centrifugal total heart. The haematological measurements made during the experiments indicated that no remarkable blood damage occurred and that all the biochemical datums remained relatively unchanged. Because the centrifugal pump has been considered, until now, to be able only to produce a nonpulsatile flow, its applications have been limited mainly to assist the heart. This first assessment of an impeller total heart reported here will open the application area of centrifugal pumps to include cardiovascular surgery.

[The first successful case or Norwood operation for hypoplastic left heart syndrome in Taiwan]

Hypoplastic left heart syndrome is not infrequently seen in Taiwan, but all died previously. An 8 day-old-male baby suffering from hypoplastic left heart syndrome was transferred to our hospital after cardiopulmonary resuscitation. Oral prostaglandin E2 was used to maintain ductal patency and carbon dioxide was used through a respirator to control his pulmonary blood flow. He underwent Norwood operation at age 15 days under deep hypothermia and circulatory arrest. The postoperative course was smooth and occasional tachypnea was controlled by carbon dioxide inhalation through a mask. A follow up echocardiogram showed patent shunt and neoaortic pathway, good interatrial communication and mild tricuspid regurgitation. The baby survived and has fared well 2 years postoperatively.

CONCLUSION

We recommend carbon dioxide manipulation before and after the Norwood operation for hypoplastic left heart syndrome with increased pulmonary blood flow uncontrollable by the respirator.

Color Doppler ultrasound used for screening varicocele: the clinical significance as compared to physical examination

The Acuson 128 XP color Doppler ultrasound (CDUS) unit has been applied to cases of infertility in the Chang Gung Memorial Hospital infertility clinic since November 1992. Seventy-four infertile males (group I) and 82 fertile cases (group II) with clinical obvious varicocele (detected by physical examination) were enrolled in this retrospective analysis. Subclinical varicocele (27%) may account for large group of the infertile men. It occurs almost bilaterally and can only be detected by CDUS. On the contrary, 26.8% of the cases with clinical obvious varicocele can be objectively ruled out by CDUS. Color Doppler ultrasound proved to be an easy, effective, convenient and noninvasive instrument for determining subclinical varicocele. It also helped to avoid unnecessary varicocelectomy in cases as judged by physical examination alone.

Simultaneous Bentall's procedure and sternal turnover in a patient with Marfan syndrome

A patient with Marfan syndrome with ascending aortic aneurysm, aortic regurgitation and pectus excavatum was treated with simultaneous Bentall's procedure and sternal turnover. Partial sternal necrosis and mediastinitis developed 12 days after surgery. After debridement of about one-third of turnovered sterno-costal complex (SC), successful salvage of the remaining two-thirds of SC and sterilization of the infected aortic Dacron graft were accomplished with pedicled omental flap. The 7 previously published cases of simultaneous Bentall's procedure and sternal turnover are reviewed.

Unusual form of total anomalous pulmonary venous connection with double drainage

A patient with complex congenital heart disease was diagnosed by two-dimensional echocardiography. Total anomalous pulmonary venous connection (TAPVC) was suspected because of the results of two-dimensional echocardiography, but the exact anatomy was delineated by cineangiocardiography as an unusual form of TAPVC with double drainage or connections to the left superior vena cava at nearly the same level. The clinical implications and possible embryogenesis for such a condition are discussed.

Flow pattern of four pulmonary veins in a case with prolapsing left atrial myxoma. A case report

The authors report the flow pattern of the four pulmonary veins in a case with prolapsing left atrial myxoma. The early systolic flow was reversed, midsystolic forward flow was diminished, and diastolic forward flow was augmented and decelerated rapidly in all four pulmonary veins. This phenomenon is attributed to the dynamic movement of the myxoma.

Monitoring of two hearts in one chest

A 32 year old patient with end-stage cardiomyopathy underwent heterotopic heart transplantation with a small donor heart. Monitoring of this unusual clinical setting of two hearts beating independently in one chest required special technique and scrutinous interpretation so one can differentiate donor heart from recipient heart immediately.

Effect of triiodothyronine administration in experimental myocardial injury

Twelve healthy pigs were subjected to a 20-min, period of regional myocardial ischemia by snaring the left anterior descending coronary artery (LAD) between its first and second diagonal branches. The resulting myocardial injury caused significant acute hemodynamic impairments. Cardiac index declined significantly during reperfusion interval and returned to preischemic level by postoperative day 7. Plasma total triiodothyronine (TT3), free triiodothyronine (FT3) and free fatty acid (FFA) decreased gradually and reached the nadir at 6 h after LAD occlusion. In contrast, plasma reverse triiodothyronine (rT3) increased progressively after LAD occlusion and reperfusion. To investigate the effect of T3 on ischemic myocardium, T3 (0.2 microgram/kg/dose; n = 5) or saline (placebo; n = 6) was administered immediately, 30 min, 60 min, 90 min, and 120 min after reperfusion. Plasma TT3 and FT3 increased dramatically after triiodothyronine supplement but declined to presichemic level at six h after LAD occlusion. The pigs treated with T3 demonstrated a rapid improvement in cardiac index over the reperfusion interval, whereas cardiac index in the placebo group remained depressed. Myocardial oxygen consumption estimated by rate pressure product showed no difference between placebo and T3-treated groups. Oxygen extraction as O2 saturation difference between aorta and coronary sinus was less in T3-treated group. Nine pigs (four in the T3-treated group and five in the placebo group) were subjected to euthanasia with hypertonic KCl solution on postoperative day 7. Myocardial infarct size determined by triphenyltetrazolium chloride (TTC) tissue enzyme staining technique was not significantly different between T3-treated and placebo groups. We concluded that this animal model is a useful model of myocardial injury simulating "euthyroid sick syndrome" as seen in patients with cardiopulmonary bypass, and T3 supplementation after reperfusion significantly enhanced postischemic left ventricular functional recovery but did not affect myocardial oxygen consumption and myocardial infarct size.

Direct delivery of cardioplegia to the coronary arteries during arterial switch operation

A DLP pediatric cardioplegia cannula was used to deliver cardioplegic solution to the coronary arteries: it seals on the artery button. The technique has been used in consecutive 37 patients during arterial switch operation without complication. This way of delivering cardioplegia solution is simple and effective.

In vivo testing of a pulsatile implantable impeller pump as a left ventricular assist device used in calves

A pulsatile implantable impeller pump was tested as a left ventricular assist device in five calves. The experiments lasted for 4-11 days. Death or termination was mainly due to respiratory complications or bleeding, irrelevant to the pump itself. As indicators of haemolysis, thrombogenesis, renal and hepatic functions, free haemoglobin (FHb), haematocrit (Hct), platelet number (Plt), lactate dehydrogenase (LDH), blood urea nitrogen (BUN), creatinine, serum glutamic oxalacetic transaminase (GOT) and total bilirubin were measured preoperatively, at the beginning of the pumping (pump on), six hours later and every day thereafter. The data indicated that the pump caused no severe blood damage or organ dysfunction. Thus, the feasibility of a pulsatile centrifugal pump was demonstrated. The pump with its driver weighs 110 g and is capable of delivering a blood flow up to 8 l/min against 100 mmHg mean pressure.

Evolution of coronary artery pattern according to short-axis aortopulmonary rotation: a new categorization for complete transposition of the great arteries

OBJECTIVES

We studied the correlation between coronary artery pattern and aortopulmonary rotation in complete transposition of the great arteries.

BACKGROUND

Classifications of the coronary arteries in complete transposition are puzzling and incomplete.

METHODS

Coronary artery anatomy and relation of the great arteries were identified at angiography, echocardiography, surgical intervention or autopsy in 76 patients with complete transposition from 1988 to 1993. Five main types (type 0 and Shaher types 1,2,4 and 9) and their similar variants of epicardial configuration were categorized into five patterns (O, I, II, IV and IX). In addition, data from 568 cases from published reports were collected for analysis.

RESULTS

As the aorta rotated from a left anterior to a directly anterior location relative to the pulmonary trunk, the left anterior descending coronary artery arose from the left-hand sinus together with the right coronary artery (type 0, one case decreased to no cases); then it gradually shifted to the left to have the same origin as the left circumflex coronary artery from the right-hand sinus (type 1, 10 cases increased to 146, p < 0.0003). When the aorta rotated farther clockwise from directly anterior to right anterior (type 1, 146 cases increased to 235; type 2, 9 cases increased to 50, p < 0.0006) or from right anterior to right lateral (type 1, 235 cases decreased to 6 cases; type 2, 50 cases decreased to 20, p < 0.00000), the left circumflex coronary artery tended to move retropulmonically and originated from the left-hand sinus with the right coronary artery (type 2). When the aorta moved from right anterior to right lateral (type 2, 50 cases decreased to 20; type 4, 13 cases increased to 14, p < 0.031) or from right lateral to right posterior (type 2, 20 cases decreased to 1; type 4, 14 cases increased to 16, p < 0.0003), the right coronary artery shifted to the right-hand sinus anteaortically to join the left anterior descending coronary artery (type 4). Finally, the left anterior descending coronary artery combined with the left circumflex coronary artery (type 9, 12 cases increased to 21, p = 0.407) to become the usual pattern for normally related great arteries. Eta-square analysis showed that the evolution from pattern O to IX was dependent on clockwise aortopulmonary rotation.

CONCLUSIONS

The coronary arteries in complete transposition of the great arteries can be classified into five patterns and their evolution deduced on the basis of aortopulmonary rotation. Dependence of coronary artery type on aortopulmonary rotation made it possible to anticipate the coronary pattern from the relation of the great arteries in transposition.

Resistance to 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine derivatives is generated by mutations at multiple sites in the HIV-1 reverse transcriptase

Virus isolates resistant to 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) and a highly potent HEPT derivative, [1-benzyloxymethyl-5-ethyl-6-(alpha-pyridylthio)uracil] (NSC 648400, E-BPTU), were selected in cell culture. Cross-resistance evaluation indicated that the two drug-resistant virus isolates were phenotypically distinct from one another although each of the virus isolates was resistant to both of the HEPT derivatives. The virus isolate resistant to NSC 648400 had a single amino acid change in the reverse transcriptase (Y181C) which resulted in cross-resistance to all of the nonnucleoside reverse transcriptase inhibitors evaluated, with the exception of calanolide A. The NSC 648400-resistant virus isolate exhibited 15-fold enhanced sensitivity to calanolide A. The virus isolate selected in the presence of HEPT exhibited a single amino acid change (P236L) which was not cross-resistant to other nonnucleoside RT inhibitors tested with the exception of the two HEPT derivatives. This HEPT-resistant virus isolate exhibited enhanced sensitivity (5- to 10-fold) to thiazolobenzimidazole. We have used both virus isolates with defined single amino acid changes in the RT and bacterially expressed RTs with site-directed amino acid substitutions to test the effects of a wide variety of mutations on the activity of NSC 648400. Single mutations at amino acids 101, 103, 106, 181, or 236 yielded virus with high resistance (> 20-fold) to NSC 648400, while lower levels of resistance were seen with mutations at amino acids 98, 100, or 108. These results suggest that several changes in the conformation of the nonnucleoside inhibitor binding site of the HIV-1 reverse transcriptase can affect the inhibitory activity of the HEPT class of compounds.

Urologic cancers in uremic patients

From 1981 through 1990, 21 urologic cancer cases were discovered in 21 uremic patients at our hospital. This constituted 55% (11 of 20) of the total malignancies in nondialyzed uremic patients, 41% (nine of 22) of the total in chronic hemodialysis patients, and 50% (one of two) of those in patients on continuous ambulatory peritoneal dialysis. No cases of urologic cancer were found in kidney transplant recipients. When compared with the general population, the standardized incidence ratio of kidney cancer in chronic hemodialysis patients was found to be 24.1 (P < 0.01) and that of bladder cancer was found to be 16.4 (P < 0.01). Multiple underlying renal diseases contributed to the development of the urologic cancer cases, including four analgesic nephropathy-associated transitional cell carcinoma cases, two acquired cystic kidney disease-associated renal cell carcinoma cases, two chronic pyelonephritis-associated (stone and tuberculosis) squamous cell carcinoma cases, and one xanthogranulomatous pyelonephritis-associated transitional cell carcinoma case. Uremia per se may be an important promoting factor. Hematuria (17 of 21 cases) was the most common presenting feature despite the fact that most of the patients were anuric. The clinical diagnosis of renal parenchymal tumors was based on ultrasonography (five of five cases), whereas most urothelial tumors were detected by cystoscopy or retrograde pyelography (14 of 16 cases). The survival rate of the 17 aggressively treated patients was 82% at 2 years and 45% at 5 years. We conclude that uremic patients are at greater risk of developing urologic cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Epididymal sperm aspiration with assisted reproductive techniques: difference between congenital and acquired obstructive azoospermia?

From July 1992 to May 1994, 31 cases of obstructive azoospermia-induced infertility underwent 35 epididymal sperm aspiration procedures and assisted reproductive techniques. These included in-vitro fertilization (IVF), zygote intra-Fallopian transfer (ZIFT), subzonal insemination (SUZI) and intracytoplasmic sperm injection (ICSI) with embryo transfer or tubal embryos transfer. The motile spermatozoa were retrieved using a gauge 24 Medicut cannula and flush medium. Total oocyte fertilization rate was 23.4% and the clinical pregnancy rate was 12.5% (four out of 32 treatment cycles). Congenital absence of the vas deferens was found in 16 cases (51.6%) and secondary genital duct obstruction was present in 15 cases (48.4%). In all, 29 aspirations were retrieved from the caput of the epididymis and six from the epididymal body or tail. The fertilization rate for the caput spermatozoa was much less than that for other areas of the epididymis (P < 0.05). Though there were no predictable differences in fertilization rates between the congenital and acquired groups, by using epididymal spermatozoa for assisted reproduction, the congenital group seemed to have a stronger tendency to achieve pregnancy (20 versus 5.9%).

Changes of white blood cells, immunosuppressive acidic protein, and interleukin-2 receptor after open heart surgery

There are a lot of immunological changes after major surgery, especially in open heart surgery when blood flows through a cardiopulmonary bypass system. We monitored leukocyte count, lymphocyte subpopulation count, soluble IL- 2 receptor (sIL-2r) and serum IL-2 levels, and an immunosuppressive acidic protein (IAP) level before and on the 1st, 7th, and 14th day after open heart surgery. It was noted that there were significant increases of total leukocyte and granulocyte counts for more than two weeks. But total lymphocyte, T-lymphocyte, b-lymphocyte, natural killer cell, suppressor T-cell, and helper T-cell all showed significant decreases in absolute numbers for more than one week as compared to the preoperative values. Serum IAP level was elevated for more than two weeks after operation. Serum IL-2 decreased but serum sIL-2R increased in the postoperative period. It is concluded that there is a period of immunosuppression after open heart surgery which lasts for at least one week and perhaps more than two weeks.

In vivo studies of pulsatile implantable impeller assist and total hearts

A pulsatile impeller assist heart and a total heart were tested as a chronic left ventricular assist device in 5 calves and an acute biventricular assist device in 4 pigs respectively, to evaluate their blood compatibility. During the left ventricular assist experiments, the indicators for hemolysis, thrombogenesis, renal dysfunction, and hepatic dysfunction were measured preoperatively, at the beginning of the pumping, 6 h postoperatively, and every following day. The results demonstrated that the impeller assist heart causes no severe blood damage nor organ dysfunction in the experiments lasting up to 11 days. In biventricular assist experiments, the number of red blood cells, white blood cells, platelets, and the hematocrit, hemoglobin, free hemoglobin, and lactate dehydrogenase levels were tested preoperatively at the beginning of the pumping and every 2 h postoperatively. The data remained in acceptable ranges during experiments lasting 6 h. It is confirmed that the authors' impeller assist heart and total heart have the advantages of simplicity, implantability, and pulsatility with good blood compatibility.

Clinical use of pentastarch in cardiac surgery without homologous blood transfusion

In an attempt to avoid the use of homologous blood transfusion, we used pentastarch 6% or 10% in a consecutive series of open heart surgery. After induction of anesthesia, whole blood 500 cc was withdrawn from the patient via an artery line, and 6% or 10% pentastarch 500 cc was infused simultaneously via a central venous line. A further 500 cc pentastarch was placed in the heart-lung machine as a priming solution. After the operation the autologous blood was transfused. Pentastarch 500cc was also infused in the intensive care unit as a plasma expander. Significant improvements in cardiac output with decrease in hematocrit, plasma viscosity, systemic and pulmonary vascular resistance were noted after pentastarch infusion, due to its hemodiluting effects. Patients treated with pentastarch did not require transfusion of homologous blood, and they also displayed no abnormal coagulopathy, or increased amounts of postoperative bleeding during hospitalization. All patients were discharged without additional hospital stay. With the aid of pentastarch, acute normovolemic hemodilution can be performed safely in cardiac surgery with the advantages of saving stored blood, reducing the risks associated with homologous blood transfusion and profiting from hemodilution. It is therefore concluded that cardiac surgery can be performed safely with 6% or 10% pentastarch without any homologous blood transfusion.

Surgical treatment of complete atrioventricular septal defect associated with tetralogy of Fallot

The combination of complete atrioventricular septal defect (AVSD) and tetralogy of Fallot (TF) was reported to occur in less than 2% of patients undergoing repair of TF. From September 1981 to November 1989, five consecutive patients with such combination underwent total correction at National Taiwan University Hospital. Their age ranged from 3.8 years to 6.3 years. Two cases were associated with Down's syndrome. All interventricular communications were repaired by combined transatrial and transventricular approach and a separate pericardial patch was used to repair the interatrial communication. The transannular patch (TAP) was not used in one case; of the four cases with TAP, a pericardial monocusp was mounted in one of them. There was one hospital mortality, and one late death. Both were related to intractable right heart failure. We conclude that total repair of this anomaly could be accomplished after 3 years of age provided there is thorough awareness of anatomical features and avoidance of right heart failure.

[Comparison of UW solution and UR (a modified Collins) solution for renal preservation in renal transplantation]

For the storage of human transplanted organs, the benefit of "UW solution" has been proven especially in keeping a longer preservation time for the liver and pancrease; however, the value for kidney preservation was still debated. A total of 293 cases of renal transplantation were performed over 12 years in our hospital and 206 cases were cadaveric transplants. The latter ones were further divided into 3 groups, according to the immunosuppressive medication and preservation solution used. In the CsA treated groups, the ATN rates significantly decreased in those preserved with the UW solution than with the UR solution. Although the UW solution did not improve the graft survival in our series, it did save the cost for postoperative hemodialysis and shorten the hospital stay which made it cost effective.

Action of uracil analogs on human immunodeficiency virus type 1 and its reverse transcriptase

Three structural analogs of 5-ethyl-1-benzyloxymethyl-6-(phenylthio)uracil (E-BPU) inhibited human immunodeficiency virus type 1 (HIV-1) replication without cytotoxicity in vitro and were more potent than azidothymidine and were as potent as E-BPU. The target of these compounds is HIV-1 reverse transcriptase. Reverse transcriptases resistant to nevirapine (tyrosine at position 181 to cysteine) and TIBO R82150 (leucine at position 100 to isoleucine) are cross resistant to E-BPU analogs. Nevirapine- or TIBO R82150-resistant HIV-1 were cross resistant to E-BPU analogs but were inhibited at concentrations 11- to 135-fold lower than the cytotoxic doses.