Determinants of pulmonary hypertension in patients with end-stage kidney disease and arteriovenous access

BACKGROUND

Pulmonary Hypertension (PH) is a sequela of arteriovenous (AV) fistulas (AVF) or AV grafts (AVG) in patients with end-stage kidney disease (ESKD) due to the creation of shunt physiology and increased pulmonary blood flow. PH has been consistently associated with increased mortality but there is a paucity of data regarding management.

RESEARCH QUESTION

The objective of this study was to identify risk factors and outcomes in patients who develop PH after AVF or AVG creation for hemodialysis access.

METHODS

Using the United States Renal Data System, we identified all patients over age 18 initiated on dialysis from 2012-2019 who did not receive renal transplant. We identified a) the predictors of PH in patients with ESKD on hemodialysis; b) the independent mortality risk associated with development of PH.

RESULTS

We identified 478,896 patients initiated on dialysis from 2012-2019 of whom 27,787 (5.8 %) had a diagnosis of PH. The median age was 65 (IQR: 55-74) years and 59.1 % were male. Reduced ejection fraction, any congestive heart failure, obstructive sleep apnea, and female sex were the strongest predictors of PH diagnosis. Both AVG and AVF were also associated with an increased rate of PH diagnosis compared to catheter-based dialysis (p < 0.001). PH portended a poor prognosis and was associated with significantly increased mortality (p < 0.001).

CONCLUSIONS

Patients with AVF or AVG should be screened using echocardiography prior to creation and monitored with serial echocardiography for the development of PH, and if present, considered for revision of the AVA. This is also the first study to identify that AVG are a risk factor for PH in dialysis patients.

Post-Capillary Pulmonary Hypertension: Clinical Review

Pulmonary hypertension (PH) caused by left heart disease, also known as post-capillary PH, is the most common etiology of PH. Left heart disease due to systolic dysfunction or heart failure with preserved ejection fraction, valvular heart disease, and left atrial myopathy due to atrial fibrillation are causes of post-capillary PH. Elevated left-sided filling pressures cause pulmonary venous congestion due to backward transmission of pressures and post-capillary PH. In advanced left-sided heart disease or valvular heart disease, chronic uncontrolled venous congestion may lead to remodeling of the pulmonary arterial system, causing combined pre-capillary and post-capillary PH. The hemodynamic definition of post-capillary PH includes a mean pulmonary arterial pressure > 20 mmHg, pulmonary vascular resistance < 3 Wood units, and pulmonary capillary wedge pressure > 15 mmHg. Echocardiography is important in the identification and management of the underlying cause of post-capillary PH. Management of post-capillary PH is focused on the treatment of the underlying condition. Strategies are geared towards pharmacotherapy and guideline-directed medical therapy for heart failure, surgical or percutaneous management of valvular disorders, and control of modifiable risk factors and comorbid conditions. Referral to centers with advanced heart and pulmonary teams has shown to improve morbidity and mortality. There is emerging interest in the use of targeted agents classically used in pulmonary arterial hypertension, but current data remain limited and conflicting. This review aims to serve as a comprehensive summary of postcapillary PH and its etiologies, pathophysiology, diagnosis, and management, particularly as it pertains to advanced heart failure.

Transcatheter Edge-to-Edge Repair in Patients With End-Stage Renal Disease on Dialysis: A USRDS Registry Study

Transcatheter edge-to-edge repair (TEER) of the mitral valve has become standard of care for the treatment of high-risk patients with severe mitral regurgitation. Patients with end stage renal disease (ESRD) on hemodialysis were either excluded or severely underrepresented in all seminal trials proving the safety and efficacy of TEER. There have been few studies that evaluated the effectiveness or complications of TEER in ESRD patients. Using the United States Renal Data System (USRDS), we identified all ESRD patients who underwent TEER from October 2015 to December 31, 2019. Major comorbidities were recorded and Kaplan-Meier curves were generated for survival and freedom from hospitalization or death. The study population included 965 patients, of which 576 (59.7%) were male. The median age at the time of TEER was 72.5 (IQR: 64.4-79.1) years. There were 130 (13.2%) patients with heart failure with reduced ejection fraction (HFrEF), 110 (11.2%) with heart failure with preserved ejection fraction (HFpEF) and 745 (74.6%) with an indeterminate ejection fraction. During follow-up, strokes occurred in 61 (6.3%) patients, infective endocarditis in 42 (4.4%) patients, mitral stenosis in 13 (1.3%) and valve embolism in less than 11 patients. One-year survival was 56.9%, and 2-year survival was 33.9%. In patients with ESRD undergoing TEER, only a preserved ejection fraction (HR: 0.70, 95% CI: 0.50-0.99, P = 0.041) was a significant predictor of survival in a cox proportional hazards model. Despite favorable in-hospital outcomes one-year mortality rates surpass those reported in broader patient cohorts. The increased incidence of infective endocarditis and mitral stenosis is likely related to increased risk intrinsic to those with ESRD.

Trends in cardiovascular complications of pregnancy: A nationwide inpatient sample analysis

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of pregnancy-related mortality in the United States. Physiologic stress of pregnancy can induce several hemodynamic changes that contribute to an increased risk of cardiac complications in the peripartum period. There are ongoing efforts to improve cardiovascular mortality in pregnant patients. Understanding trends in cardiovascular complications during pregnancy may provide insight into improving care for high-risk pregnancies.

METHODS

We retrospectively analyzed data from the National Inpatient Sample (NIS) Database and identified all inpatient hospitalizations for pregnancy and delivery. We then analyzed trends in the rates of cardiac complications in the pregnant patient.

RESULTS

There are concerning increases in trends of cardiac complications and comorbidities in pregnant people including: acute coronary syndrome, spontaneous coronary artery dissection, cardiogenic shock, pulmonary hypertension, chronic congestive heart failure, heart transplant, aortic syndromes, stroke, and pulmonary embolism. While the rates of STEMI have decreased, the incidence of peripartum cardiomyopathy has remained stable.

CONCLUSION

There are concerning increases in certain cardiac complications during pregnancy. This is likely due to increasing age at the time of pregnancy and associated comorbidities.

Aortic Valve Replacement in Patients With ESRD and Heart Failure With Reduced Ejection Fraction

Transcatheter aortic valve replacement (TAVR) has become the standard of care for the treatment of all patients with calcific aortic stenosis. Patients with end-stage renal disease (ESRD) on hemodialysis were excluded from participation in many of the seminal trials proving the safety and efficacy of TAVR. The outcomes of TAVR in the ESRD population from a national registry showed significantly higher in-hospital and 1-year mortality compared with patients not on hemodialysis. Comparisons of outcomes for surgical versus transcatheter interventions in patients with ESRD and heart failure with reduced ejection fraction (HFrEF) are limited. Using the United States Renal Data System, we identified all ESRD patients with aortic stenosis and HFrEF who underwent TAVR, surgical aortic valve replacement (SAVR), or those with HFrEF and aortic stenosis initiated on dialysis after the year 2012 to compare survival. Propensity score matching was performed, and groups were compared using Kaplan-Meier curves. The study population consisted of 7,660 patients, of which 5,064 (66.1%) were male. The median age at initiation of dialysis was 73 years (interquartile range: 65 to 80). There were 1,108 (14.5%) who underwent TAVR and 695 (9.1%) who underwent SAVR. After matching, patients who underwent TAVR had increased survival relative to those who were medically managed. In-hospital outcomes favored TAVR with less mortality and fewer complications when compared with SAVR. TAVR had improved mortality relative to SAVR in the early period, but survival curves crossed at approximately 9 months and SAVR had better mortality in the long-term. TAVR is a safe and effective procedure and is associated with improved mortality when compared with medical management. In conclusion, TAVR and SAVR are both viable options for patients with ESRD and HF with TAVR having better short-term outcomes and SAVR better long-term outcomes.

Clinical Outcomes in Adult Patients With an Anomalous Right Coronary Artery from the Left Sinus of Valsalva

An anomalous origin of the right coronary artery from the opposite sinus of Valsalva with an intramural course (R-ACAOS-IM) may cause sudden cardiac death in children and adolescents. However, the natural history and management of patients in whom this anomaly is detected later during adulthood remains uncertain. The goals of this study were to assess the impact of an R-ACAOS-IM on the clinical outcomes in an adult population and to determine if adult patients with this anomaly who do not have significant coronary artery disease (CAD) can be managed safely without surgical intervention. A database review identified patients aged >35 years with anomalous coronary arteries diagnosed by cardiac catheterization or coronary computed tomography angiography. The outcomes of patients with R-ACAOS-IM were compared with patients with anomalous left circumflex coronary arteries with retroaortic course (LCx-RA) (an anomaly not associated with ischemic events). The primary outcome was all-cause mortality. The study population consisted of 185 patients aged 59 ± 12 years. Clinical characteristics were similar in the R-ACAOS-IM (n = 88) and LCx-RA (n = 97) groups. At a follow-up of 6.6 ± 4.5 years, there was no difference in mortality (hazard ratio 0.64, 95% confidence interval 0.32 to 1.28, p = 0.20) when adjusted for gender, age, and CAD. A subgroup analysis of 88 patients with no obstructive CAD managed nonoperatively found no difference between the LCx and R-ACAOS-IM groups in mortality (hazard ratio 2.45, 95% confidence interval 0.45 to 13.40, p = 0.30). There was no significant difference between the 2 groups in the composite outcome of death, nonfatal myocardial infarction, or survived cardiac arrest. The outcome of adult patients who have anomalous R-ACAOS-IM are similar to patients who have anomalous LCx-RA with a known benign course. In conclusion, these results suggest that most patients who survive this anomaly into adulthood may be managed conservatively without intervention.

PCI for acute myocardial infarction in patients with a pre‐existing LVAD , does it improve survival?

BACKGROUND

It is well established that percutaneous coronary intervention (PCI) is a life-saving procedure for acute myocardial infarction (AMI) in the general population and is guideline-recommended for both STEMI and NSTEMI. There is little literature regarding its use in patients with a pre-implanted Left Ventricular Assist Device (LVAD).

METHODS

We retrospectively analyzed data from the National Inpatient Sample (NIS) Database to select all US adult patients (>18 years) with an LVAD diagnosed with an AMI divided into two groups; those who received PCI during the hospitalization and those who did not.

RESULTS

A total of 3722 LVAD patients with AMI were identified, of these 17% of patients received PCI and 83% did not. After propensity matching of LVAD patients with AMI, there were 626 patients who received PCI and 623 who did not. Of patients receiving PCI, 37.5% had a STEMI while 29.7% of patients who did not receive PCI had STEMI. Rates of kidney injury (36.5% vs. 43.3%, OR 0.75, 95% CI 0.60-0.94, p = 0.016), sepsis (3.2% vs. 11.4%, OR 0.26, 95% CI 0.15-0.43, p < 0.001), cardiogenic shock (44.1% vs. 50.4%, OR 0.78, 95% CI 0.62-0.97, p = 0.03) and mortality (17.4% vs. 28.9%, OR 0.52, 95% CI 0.40-0.68, p < 0.001) were all better for patients receiving PCI. Vascular complications (1.4% vs. 0%, p = 0.008) and intracerebral hemorrhage (ICH) (1.6% vs. 0, p = 0.004) were both more common in the group receiving PCI.

CONCLUSIONS

In this study, patients supported by LVAD with AMI had an elevated risk of mortality compared to generally accepted mortality rates of patients without LVAD. In this analysis PCI was associated with a decreased risk of mortality, cardiogenic shock, and kidney injury while increasing the risk for vascular complications and intracranial hemorrhage.

Does the Size or Location of Lumbar Disc Herniation Predict the Need for Operative Treatment?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The goal of this study was to determine whether the absolute size (mm²), relative size (% canal compromise), or location of a single-level, lumbar disc herniation (LDH) on axial and sagittal cuts of magnetic resonance imaging (MRI) were predictive of eventual surgical intervention.

METHODS

MRIs of 89 patients were reviewed, and patients were split into groups based on type of management received (34 nonoperative vs 55 microdiscectomy). Radiographic characteristics-including size of disc herniation (mm²), size of spinal canal (mm²), location of herniation on axial (central, paracentral, foraminal) and sagittal (disc level, suprapedicle, pedicle, infrapedicle) planes, and type of herniation (bulge, protrusion, extrusion, sequestration)-were measured by 2 independent, orthopedic spine fellows and compared between groups via univariate and multivariate analyses.

RESULTS

The operative group showed a significantly higher percentage of canal compromise (39.5% vs 31.1%, P = .001) compared to the nonoperative group. Multiple logistic regression analysis showed higher odds of eventual operative intervention for a disc protrusion (odds ratio [OR] 6.30 [1.99, 19.86], P = .002) or disc extrusion (OR 11.5 [1.63, 81.2], P = .014) for Rater 1 and a higher odds of eventual surgical management for a paracentral location for both Rater 1 and Rater 2 (OR = 3.39 [1.25, 9.22], P = .017, and OR = 5.46 [1.77, 16.8], P = .003, respectively).

CONCLUSIONS

Disc herniations in a paracentral location were more likely to undergo operative treatment than those more centrally located, on axial MRI views.

Cardiac transplantation after heparin induced thrombocytopenia: A systematic review

PURPOSE

Heparin induced thrombocytopenia (HIT) presents a unique challenge in patients requiring orthotopic heart transplantation (OHT). We sought to pool the existing evidence in a systematic review.

METHODS

Electronic search was performed to identify all relevant studies on OHT in patients with HIT. Patient-level data for 33 patients from 21 studies were extracted for statistical analysis.

RESULTS

Median patient age was 51 [41, 55] years, with 75.8% (25/33) males. All patients had a clinical diagnosis of HIT, and anti PF4/Heparin antibodies were positive in 87.9% (29/33). Median lowest reported platelet count was 46 × 10⁹ /L [27.2, 73.5]. Intraoperatively, 61% (20/33) of patients were given unfractionated heparin (UFH), while 39% (13/33) were given alternative anticoagulants. The alternative agent subgroup required more antifibrinolytics [54% (7/13) vs. 10% (2/20), p = 0.02] and clotting factors [69.2% (9/13) vs. 15.0% (3/20) p<0.01]. Peri-operative thrombosis occurred more in [53.8% (7/13) vs 0% (0/20, p<0.01) alternate agent subgroup. More patients in the alternate agent subgroup required post-operative transfusions [54% (7/13) vs. 0% (0/20), p<0.01]. Thirty-day mortality of 15.2% (5/33) was comparable between the subgroups.

CONCLUSION

Heparin use during OHT may be associated with less adverse effects compared to use of other anticoagulants with no difference in 30-day mortality. This article is protected by copyright. All rights reserved.

Can Imaging Characteristics on Magnetic Resonance Imaging Predict the Acuity of a Lumbar Disc Herniation?

BACKGROUND

Currently, no authors of existing studies have attempted to classify the signal characteristics of disc herniation on magnetic resonance imaging (MRI) and their temporal relationship to symptoms of lumbar radiculopathy. The purpose of this study was to determine whether the MRI signal characteristics are predictive of acuity of symptoms in patients with lumbar disc herniation (LDH).

METHODS

A retrospective cohort study was conducted on patients treated at an academic center for LDH from 2015 to 2018. Patients were divided into 2 groups based on symptom duration (acute: ≤6 weeks; or chronic: >4 months). Two independent observers measured T1, T2 signal, and other MRI characteristics at the affected disc level. Univariate analysis was used to compare differences between groups. Multiple logistic regression was used to determine predictors of acuity.

RESULTS

Eighty-nine patients were included (33 acute, 56 chronic) with no significant baseline differences between groups. Rater 2 observed a higher proportion of disc bulges in the chronic group (P = .021) and a higher abnormal T1 herniation signal in the acute group (P = .048). Rater 1 found a higher Pfirrmann grade (P = .005) and a higher prevalence of vertebral body spurring (P = .007) in the chronic group. Interobserver agreement for T1 central and herniation signals demonstrated poor to fair agreement, whereas the remainder of the measurements showed moderate to substantial agreement (κ = 0.4-0.8). Multiple logistic regression showed that Pfirrmann Grade 5 (odds ratio = 0.12, 95% confidence interval [0.02, 0.74], P = .022) and anterior/posterior spurring (odds ratio = 0.053 [0.03, 0.85], P = .023) were not associated with acuity.

CONCLUSIONS

Other than Pfirrmann grade or vertebral body spurring, no MRI characteristics could be reliably identified that correlate with acuity of symptoms.

LEVEL OF EVIDENCE

3.

Clock Drawing Performance Slows for Older Adults After Total Knee Replacement Surgery

BACKGROUND

Clock drawing is a neurocognitive screening tool used in preoperative settings. This study examined hypothesized changes in clock drawing to command and copy test conditions 3 weeks and 3 months after total knee arthroplasty (TKA) with general anesthesia.

METHODS

Participants included 67 surgery and 66 nonsurgery individuals >60 years who completed the digital clock drawing test before TKA (or a pseudosurgery date), and 3 weeks and 3 months postsurgery. Generalized linear mixed models assessed digital clock drawing test latency (ie, total time to completion, seconds between digit placement) and graphomotor output (ie, total number of strokes, clock size). Reliable change analyses examined the percent of participants showing change beyond differences found in nonsurgery peers.

RESULTS

After adjusting for age, education, and baseline cognition, both digital clock drawing test latency measures were significantly different for surgery and nonsurgery groups, where the surgery group performed slower on both command and copy test conditions. Reliable change analyses 3 weeks after surgery found that total time to completion was slower among 25% of command and 21% of copy constructions in the surgery group. At 3 months, 18% of surgery participants were slower than nonsurgery peers. Neither graphomotor measure significantly changed over time.

CONCLUSIONS

Clock drawing construction slowed for nearly one-quarter of patients after TKA surgery, whereas nonsurgery peers showed the expected practice effect, ie, speed increased from baseline to follow-up time points. Future research should investigate the neurobiological basis for these changes after TKA.

BLEEDING TENDENCY AND PROTHROMBIN DEFICIENCY IN BILIARY FISTULA DOGS: EFFECT OF FEEDING BILE AND VITAMIN K

In biliary fistula dogs the plasma prothrombin falls eventually to low levels and bleeding commonly occurs. Faulty absorption of vitamin K from the intestine in these animals is an important causative factor. Feeding bile permits absorption of the traces of this vitamin normally present in mixed diets, and as a result a slow rise in prothrombin level is observed. If a standard diet is supplemented with large amounts of vitamin K concentrate the prothrombin rise is rapid, provided bile or bile salt is supplied to aid in the absorption. Variations in the rate of prothrombin depletion in biliary fistula dogs kept on constant diet indicate the existence of additional factors which require further study. Our experience indicates that vitamin A and vitamin D supplements do not correct the prothrombin deficiency in biliary fistula animals.

PLASMA PROTHROMBIN: EFFECT OF PARTIAL HEPATECTOMY

Extirpation of a large portion of the liver in rats results in a marked decrease in the plasma prothrombin. The plasma prothrombin level gradually returns to normal during the period required for restoration of the liver to its normal weight. The decrease in prothrombin incident to partial hepatectomy supports the thesis that the liver is concerned in the manufacture of plasma prothrombin.

PROTHROMBIN DEFICIENCY AND THE BLEEDING TENDENCY IN LIVER INJURY (CHLOROFORM INTOXICATION)

The bleeding tendency in acute chloroform intoxication is due to deficiency in both plasma fibrinogen and plasma prothrombin. If the disorder is mild, no bleeding occurs. However, the prothrombin falls to rather low levels, although the fibrinogen falls only moderately. A bleeding tendency may also be produced by giving small repeated doses of chloroform. In such experiments, the hemorrhagic tendency is due to a deficiency in prothrombin alone. The fibrinogen level is unaffected. The relation of the liver injury to the plasma prothrombin level indicates that the liver is concerned in the manufacture of prothrombin. Prothrombin formation appears to be more easily interfered with than does fibrinogen formation.

Extrapelvic endometriosis: diagnosis and treatment

BACKGROUND

Young women with nondescript abdominal pain can be difficult to diagnose. Although extrapelvic endometriosis is infrequent, we have treated 7 patients over the past 3 years with endometriosis in the abdominal wall, inguinal canal, or surgical incisions as the etiology of their symptoms.

PATIENTS AND METHODS

We reviewed the medical records of patients whose final pathology report confirmed a diagnosis of extrapelvic endometriosis. Seven women who were treated at the University of Rochester Strong Memorial Hospital from May 1, 1991 through April 30, 1994 were identified.

RESULTS

All patients were premenopausal with no history of pelvic endometriosis. In 4 patients, symptoms were cyclical. Surgical excision was initially curative in 5 patients. Two women required reexcision. The diagnosis of endometriosis was established at exploration by gross appearance and by frozen section.

CONCLUSIONS

Endometriosis should be included in the differential diagnosis of a symptomatic mass in a celiotomy scar, the abdominal wall, or the inguinal canal. Principles of management include obtaining an accurate diagnosis and performing an adequate excision to prevent recurrence.

Chondroid chordoma. Case report and literature review

A case of the chondroid variant of chordoma is presented. The differentiating features of this entity are discussed on a clinical and histopathologic basis. A review of the topic of chordoma is also provided.

The relation of hypercholesterolemic fatty streaks to intimal permeability changes shown by Evans blue

The aortic localization of diet-induced fatty streaks in relation to focal increases in intimal permeability was evaluated in cynomoglus monkeys. Animals fed a hypercholesterolemic diet and studied at 10, 15, and 100 days had increasing intensity of Evans blue dye uptake. The overlap of fatty streaks with areas of dye intake increased as the areas of dye uptake enlarged, but all hypercholesterolemic groups showed some fatty streaks not topographically related to areas of dye uptake or flow instability. Because the upper thoracic aorta tended to show more advanced fatty streak formation dissociated from evident permeability change or hydraulic instability, it is suggested that mechanical factors associated with the geometric configuration of the descending thoracic aorta may have a significant role in the localization of some hypercholesterolemic fatty streaks.

Myocardial injury from transthoracic defibrillator countershock

Myocardial damage resulting from transthoracic administration of direct current with cardiac defilbrillators present in clinical use was studied in 66 dogs. Electrodes were applied to the thoracic skin. All direct current discharges were delivered via a commercially available defilbrillator. Most of the animals received ten consecutive discharges with a dial setting of 400 watt-seconds. Animals were killed from 3 to 14 days after receiving the discharges. Myocarial necrosis was produced in most of the animals. The lesions were characterized by sharply localized areas of muscle necrosis that progressed to fibrous scars. Mineralization of damaged muscle and florid proliferation of large mononuclear cells were striking features of the lesions.

The CLUE test. A multiparameter coagulation and fibrinolysis screening test using the platelet aggregometer

Optical density measurements of plasma clot formation and lysis were recorded using a platelet aggregometer and strip chart recorder. It was discovered that, by adding standard solutions of ellagic acid-activated partial thromboplastin, urokinase, and CaCl2, and monitoring the reaction via the recorder, characteristic curves would be generated by normal human plasma. The curve segments were labeled Tc (clotting time), which correlated with the activated partial thromboplastin time, Fc (maximum optical density change), which paralleled fibrinogen concentration, and Tl (lysis time), which corresponded generally to plasminogen levels. Deviations from normal curve segments, observed in disseminated intravascular coagulation, hypo- and hyperfibrinogenemia, factor VIII deficiency, severe hepatocellular disease, juvenile rheumatoid arthritis, and neonates (normally low in plasminogen), indicated abnormalities which were substantiated by standard procedures. This new test, given the acronym "CLUE" for clotting and lysis, urokinase enzyme activated, appears to be sensitive, inexpensive and easily performed on a sample of 0.2 ml. of plasma in only 15 minutes.

Myocardial necrosis from direct current countershock. Effect of paddle electrode size and time interval between discharges

The effect of varying both paddle electrode size and the time interval between direct current countershock on myocardial necrosis was studied. Forty-two dogs were divided into seven groups of six dogs each. All dogs were given ten consecutive, 240 watt-second countershocks (delivered energy into a 50 ohm load). Three groups were shocked with paddle electrode diameters of 8.0 cm (standard electrodes), two groups with paddle electrode diameters of 12.8 cm (large electrodes), and two groups with paddle electrode diameters of 4.3 cm (small electrodes). The time intervals between discharges in the groups shocked with the standard electrodes were 15 seconds, one minute, and three minutes. The time interval between discharges in the groups shocked with small and large electrodes was 15 seconds and three minutes. Myocardial necrosis was quantitated by precordial electrocardiographic mapping recorded minutes after, and by gross and microscopic examination of the hearts four days after direct current countershock.

When the time interval between discharges was shorter, myocardial necrosis was greater. When the time interval between discharges was constant, more necrosis was produced with smaller-sized paddle electrodes. It is concluded that large paddle electrodes should be used for delivering direct current countershocks, and that during elective cardioversion, consecutive discharges should be delivered at time intervals greater than three minutes.

Intimal thickening in normocholesterolemic rhesus monkeys fed low supplements of dietary cholesterol

Rhesus monkeys were fed a high-fat diet containing either 0, 43, or 129 µg/kcal of cholesterol for 18 months. In the monkeys on the cholesterol-supplemented diets, changes in plasma cholesterol remained within the range found in monkeys fed the cholesterol-free diet. Monkeys on the cholesterol-supplemented diets were compared with monkeys given no dietary cholesterol with range-matched plasma cholesterol; intimal thickness of the aorta and branch arteries, distribution of lipoprotein cholesterol, and tissue content of cholesterol in aorta and liver were considered. The monkeys on the cholesterol-supplemented diets showed intimal thickening with more sudanophilia and increased aortic cholesterol, a decrease in plasma high-density lipoprotein cholesterol, and an increase in low-density lipoprotein cholesterol, and the monkeys fed the higher amount of dietary cholesterol showed an increase in hepatic cholesterol. No null point for the effect of dietary cholesterol on arterial intima was found even at an intake level far below that conventionally used for the induction of experimental atherosclerosis in the nonhuman primate. The intimal changes found in response to very low cholesterol intake imply that subtle qualitative alterations in lipoproteins are of critical importance to our understanding of lesion induction.

Utilization of long-chain free fatty acids by human platelets

There was a rapid net uptake of free fatty acid (FFA) by human platelets when long-chain FFA, bound to human serum albumin, were incubated with platelet suspensions. Results from experiments in which both palmitate and albumin were labeled indicated that the fatty acid dissociated from the protein during uptake. Much of the FFA taken up by the platelet in short-term incubations remained in unesterified form, i.e., it was recovered as platelet FFA. As the incubation continued, increasing amounts of FFA were oxidized to CO(2) and incorporated into platelet lipid esters, particularly lecithin. Essentially all of the fatty acid that was incorporated into the platelet FFA fraction was released rapidly from the cells when they were exposed to a medium containing FFA-free albumin. The magnitude of uptake into the platelet FFA fraction was similiar at 0 degrees and 37 degrees C. Likewise, the rate and magnitude of FFA release from the platelet were similar at 0 degrees and 37 degrees C. Therefore, it is likely that both FFA uptake and FFA release occur by energy-independent mechanisms. The major effect of increasing the FFA concentration of the incubation medium was increased fatty acid uptake into the platelet FFA fraction. Similar results occurred when platelets were incubated in human plasma containing increasing amounts of added palmitate. At a given extracellular FFA concentration, considerably more of the saturated fatty acids, palmitate and stearate, were taken up as platelet FFA than either oleate or linoleate.

Regression of coronary atheromatosis in rhesus monkeys

Rhesus monkeys subjected to the atherogenic stimulus of a high-fat, high-cholesterol diet showed significant coronary atheromatosis at the end of 17 months. Smaller fibrotic lesions with scant stainable lipid were found in animals that were subsequently fed either of two cholesterol-free diets for 40 months. The average cross-sectional area of the lumen was more than 80% greater in regression animals than in monkeys with baseline atherosclerosis. The data support the hypothesis that uncomplicated coronary atheromas may regress in primates in appropriate dietary settings.

Effects of triiodothyronine-induced hypermetabolism on factor 8 and fibrinogen in man

Triiodothyronine (liothyronine sodium) (400-500 mug/day for 14 days) was given to six normal subjects. Factor VIII (antihemophilic globulin) activity increased from 109 to 167% (P < 0.05); fibrinogen increased from 344 to 581 mg/100 ml (P < 0.01). To test whether the increases in factor VIII activity and fibrinogen were mediated by beta adrenergic receptors, propranolol (20 mg every 6 hr) was given orally to four other normal subjects in addition to triiodothyronine for 14 days. Factor VIII increased from 100 to 161%; fibrinogen increased from 374 to 564% (P < 0.01). Factor VIII activity did not change in a severe classical hemophiliac made hypermetabolic with triiodothyronine, but it increased from 39 to 82% in a patient with von Willebrand's disease. Triiodothyronine-induced hypermetabolism increased the incorporation of selenomethionine-(75)Se into plasma fibrinogen. These results suggest that the increases in clotting factor activity during triiodothyronine-induced hypermetabolism reflect an effect of increased protein synthesis rather than enhanced stimulation of beta adrenergic receptors.

Toxic effects of glucagon-induced acute lipid mobilization in geese

The toxic effects associated with rapid lipid mobilization and a high plasma free fatty acid (FFA) concentration produced by glucagon were evaluated. Glucagon (0.5 mg/kg of body wt) was injected intravenously into nonfasting geese. The geese developed rapid respirations and high plasma FFA levels within 15 min after the glucagon injection; three of eleven died. Control geese, injected with saline, did not exhibit toxic signs. Peak FFA concentrations developed 15 min after glucagon and high levels persisted for over 90 min. Geese injected with glucagon frequently developed electrocardiographic abnormalities that included supraventricular tachycardia, premature ventricular contractions, and signs of myocardial ischemia. Light and electron microscopy revealed acute myocardial degeneration and fatty infiltration of the liver. The increase in plasma FFA concentrations and toxic effects were not prevented by pretreatment with nicotinic acid or propranolol.

The coagulant and thrombogenic properties of human atheroma

Suspensions of gruel from severely atherosclerotic human aortas and coronary arteries were tested in several coagulation systems. The atheromatous material shortened the clotting time of normal whole blood and plasma and accelerated thrombus formation time in the Chandler apparatus. Normal human platelets in platelet-rich plasma were aggregated by the atheromatous gruel. Aggregation did not occur when the gruel was added to platelet-rich plasma from a patient with a severe factor XII (Hageman) deficiency. The intravenous injection of atheromatous plaque suspensions into rats caused thrombocytopenia, shortening of the whole blood clotting time, and thrombosis.

Coagulation of blood from patients with classical hemophilia, with Hageman factor deficiency, and with coumarin-induced anticoagulant effect was accelerated by the addition of the atheromatous gruel. Blood from patients given heparin, however, largely retained its anticoagulant activity.

Atheromatous material from both aortic and coronary arteries behaved similarly in the systems tested. The coagulant and platelet clumping properties of atheromatous plaques may be related to their content of fatty acids, phospholipids, collagen, or thromboplastin.

Platelets, fatty acids and thrombosis

The sodium salts of stearic, oleic, linoleic and linolenic acids were added to human washed platelet suspensions and platelet-rich citrated plasma. Aggregation of the platelets was measured microscopically and with a turbidimetric method. All of the fatty acids had the ability to produce aggregation when added to washed platelets, but stearic acid, a long-chain saturated fatty acid, was more potent than were the unsaturated acids when added to platelet-rich plasma. Aggregation of platelets by fatty acids required the presence of calcium ions and the aggregation was irreversible. The addition of albumin diminished the aggregating effects of fatty acids, but microscopic aggregates still formed in most instances. Subnormal aggregation was noted when sodium stearate was added to platelet-rich plasma from a patient with a severe deficiency of factor XII (Hageman factor). Thus, fatty acids are now known to have two potential thrombogenic effects: platelet aggregation and the activation of clotting factors involved in the early stages of blood coagulation.

Concept of a common protein moiety, containing disulfide bonds, in prothrombin, prothrombin derivative (autoprothrombin) and thrombin

With a recently devised argentometric amperometric method, disulfide was demonstrated in biothrombin, citrate thrombin and prothrombin derivative (autoprothrombin) in the same quantity (43 µm/100 mg N) as that present in prothrombin. Sulfhydryl groups were not detected in any of these clotting factors. Prolonged storage and denaturation by heating before disulfide could be detected in some samples of thrombin, as well as a difference in sensitivity to the inhibitory effect of sulfhydryl compounds, indicate a distinction between prothrombin and thrombin in the accessibility of their —S—S— bonds. The prothrombin derivative (autoprothrombin) on which the sulfhydryl and disulfide analyses were performed was shown to be deficient in prothrombin and thrombin activity, to exhibit pronounced factor VII activity and to be capable of conversion to thrombin by sodium citrate, but not by biological activators. The inhibition, amperometric and activator studies provide additional support for a monophyletic hypothesis of a single, but complex, glycoprotein, which possesses a protein moiety containing—S—S—bonds, and which by alteration of its side chains or end groups, may exhibit prothrombin, thrombin or accelerator activity. Such studies render the possibility that factor VII is a specific protein entity, increasingly doubtful.

Muscular dystrophy in biliary fistula dogs; possible relationship to vitamin E deficiency

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