Atrial Fibrillation and Mitral Regurgitation: Clinical Performance of Direct Oral Anticoagulants in a Real-World Setting

BACKGROUND

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is frequently present in patients with mitral regurgitation (MR). Currently, there is a lack of real-world evidence specifically addressing the clinical performance of direct oral anticoagulants (DOACs) in patients with AF and concomitant MR. Therefore, the aim of the present study was to assess the efficacy and safety profile of DOACs therapy in patients with AF and MR.

METHODS

Data for this study were sourced from the Atrial Fibrillation Research Database in the Department of Cardiology at Monaldi Hospital. The database was queried for AF patients with MR who were prescribed DOACs therapy. The primary safety outcome was defined as the annual incidence rate of major bleeding events and the primary effectiveness outcome as the annual incidence rate of all events classified as ischemic stroke, transient ischemic attacks, and systemic embolisms.

RESULTS

Consecutive AF patients with concomitant mild to severe MR who received DOACs therapy (n = 259) were included. Patients were dichotomized in 2 groups according to MR severity: a mild-to-moderate group (MR 1-2+; n = 151) and a moderate-to-severe group (MR 3-4+; n = 108). The incidence rate of major bleedings was significantly higher in MR 3-4+ group (3.92%) compared with the MR 1-2+ group (1.18%; hazard ratio [HR]: 3.2; 95% CI: 1.4-7.3; P = .0059). The incidence rate of thromboembolic events between MR 3-4+ group (0.66%) and MR 1-2+ group (0.62%) was not significantly different (HR: 0.75; P = .823).

CONCLUSIONS

In the present study, there was no difference in the efficacy profile of DOACs between AF patients with mild-to-moderate and moderate-to-severe MR. Considering the increased bleeding risk, a close and careful follow-up should be warranted for patients with moderate-to-severe MR.

Evolving concepts in the pathophysiology of biliary lipid secretion

Secretion of biliary cholesterol and phosphatidylcholine is a complex process essentially involving lipid supply to the canalicular membrane from either preformed or neosynthetic hepatic sources, and the detergent action of bile salts. Previous research has shown that an altered secretion of biliary lipids and/or bile salts firmly disposes to gallstone formation, and may also be involved in the pathogenesis of cholestasis. Recently, attention has been turned to the molecular and genetic factors underlying biliary lipid secretion, and this approach has provided a significant body of new data among which: 1. The biochemical and genetic characterization of glycoproteins sP-gp and mdr2-Pgp functioning in the canalicular transport of bile salts and phosphatidylcholine, and the evaluation of their role in experimental and human cholestasis; 2. The identification of genetic patterns determining susceptibility to gallstone formation via an increased secretion of biliary lipids. It is likely that an expansion of these research lines and methodology will contribute to a better biochemical characterization of bile lipid secretion with expected benefits upon the diagnosis and treatment of related diseases; 3. A more defined appreciation of the coordinate roles played by the hepatocyte lipid synthesis and canalicular transport in the activation of the biliary lipid secretion pathway.

Enhancement of mdr2 gene transcription mediates the biliary transfer of phosphatidylcholine supplied by an increased biosynthesis in the pravastatin-treated rat

An increase of biliary lipid secretion is known to occur in the rat under sustained administration of statin-type 3-hydroxy-3-methylglutaryl (HMG) coenzyme A (CoA) reductase inhibitors. The present study has addressed critical mechanisms of hepatic lipid synthesis and phosphatidylcholine (PC) biliary transport in the rat fed with a 0.075% pravastatin diet for 3 weeks. After treatment, biliary secretion of PC and cholesterol increased to 233% and 249% of controls, while that of bile salts was unchanged. Activity of cytidylyltransferase (CT), a major regulatory enzyme in the CDP-choline pathway of PC synthesis, was raised in both microsomal and cytosolic fractions (226% and 150% of controls), and there was an increase to 187% in the mass of active enzyme as determined by Western blot of microsomal protein using an antibody specific to CT. Cytosolic activity of choline kinase, another enzyme of the CDP-choline pathway, also increased to 175% of controls. In addition, there was an over eightfold increase in the HMG CoA reductase activity and mRNA. Thus, an increased PC and cholesterol synthetic supply to hepatocytes appeared as a basic mechanism for the biliary hypersecretion of these lipids. Notwithstanding the increased synthesis, hepatic PC content was unchanged, suggesting an enhanced transfer of this lipid into bile. Indeed, there was a sevenfold increase of multidrug resistance gene 2 (mdr2) gene mRNA coding for a main PC canalicular translocase. Thus, hypersecretion of biliary PC in the model studied can be explained by an up-regulation of mdr2 gene transcription and its P-glycoprotein product mediating the biliary transfer of PC supplied by an increased biosynthesis.

Enhancement of fatty acid and cholesterol synthesis accompanied by enhanced biliary but not very-low-density lipoprotein lipid secretion following sustained pravastatin blockade of hydroxymethyl glutaryl coenzyme A reductase in rat liver

A 3-week treatment of rats with pravastatin (PV) augmented biliary cholesterol and phospholipid output 3.6- and 2.2-fold over controls, while bile acid (BA) output and kinetics were unchanged. No major changes were detected in hepatic and serum cholesterol concentrations despite the PV inhibitory property on hydroxymethyl glutaryl coenzyme A (HMG CoA) reductase. To evaluate the mechanisms of this adaptive phenomenon, several parameters of hepatic lipid homeostasis were assessed. Biliary cholesterol changes could not be attributed to an increased influx of lipoprotein cholesterol to the liver and bile. Hepatic low-density lipoprotein (LDL) receptor content, as inferred from Western blot analysis, was unchanged, as was the biliary excretion of labeled cholesterol derived from chylomicron remnants. In vivo 3H2O-incorporation studies showed an 80% increase in hepatic cholesterol synthesis, evidence for bypass of the PV block. Remarkably, fatty acid synthesis was also stimulated twofold, providing substrate for hepatic triglycerides, which were slightly enhanced. However, serum triglycerides decreased 52% associated with a 22% decrease in hepatic very-low-density lipoprotein (VLDL) secretion. Thus, the biochemical adaptation following PV treatment produces complex alterations in hepatic lipid metabolism. An enhanced supply of newly synthesized cholesterol and fatty acids in association with a limited VLDL secretion rate augments the biliary lipid secretion pathway in this experimental model.

Biliary excretion of chylomicron remnant cholesterol in the rat: responses to the expansion of their plasma pool and promoting role of stimulated bile-acid synthesis

1. Chylomicron remnants, the intermediate intestinal lipoproteins carrying the bulk of dietary cholesterol, are actively taken up and degraded in the hepatocytes, releasing cholesterol which can be excreted in bile. To study this pathway, a mass of remnants, leading to a consistent rise in hepatic cholesterol, was administered as an intravenous bolus in rats with chronic bile fistula equilibrated by water, electrolyte and taurocholate infusions, and changes in biliary lipids and bile acids were evaluated for up to 24 h in comparison with baseline. 2. A mean 16% increase in the net output of bile acids was observed at each time interval after lipoprotein injection, accounting for a 24h cumulative excretion of approximately one-third of the administered cholesterol mass. These changes did not reach statistical significance however. The cholesterol output and concentrations of all biliary lipids did not vary either. Without taurocholate replacement, remnants injection was followed by a 15-20% decrease in bile acid and bile lipid secretion, presumably due to an insufficient hepatic bile-acid flux. 3. When [3H]cholesterol-labelled remnants were administered at the same mass in the chronic equilibrated bile fistula model, 21% of injected radioactivity was excreted in 24h, distributing mostly in acidic rather than neutral sterols (20.02 +/- 1.85 compared with 1.07 +/- 0.04), with an acidic to neutral sterol mean ratio of 16. 4. To exclude interfering effects from the administered cholesterol mass and chronic bile fistula, 3H-labelled remnants were also studied as a cholesterol trace injected in rats with acute bile fistula.(ABSTRACT TRUNCATED AT 250 WORDS)

Capillary blood flow to the skin of forearm in cirrhosis

In liver cirrhosis a hyperkinetic circulatory state is frequently observed as a consequence of an arterial or even a venous peripheral vasodilatation with secondary increase in cardiac output. Indirect evidence suggests that, in liver disease, the manifestation of warm hands, capillary pulsation, or palmar erythema may also relate to such a state by way of an increased skin blood flow. The purpose of the present study has been to directly assess capillary skin blood flow in liver disease through the clearance of a locally injected radioactive substance. The study was performed in 24 patients with different liver diseases, including 14 Child class II cirrhotics, and in 9 control subjects. A small volume of Na 131I solution was injected at the volar surface of the forearm, and radioactive counts were recorded continuously for ten seconds every minute for up to twenty minutes. The best fit line of the disappearance rate was determined by the least square method, and both its T/2 and an estimated blood flow parameter were calculated. The T/2 of isotope disappearance rate was 4.54 +/- 0.71 and 4.38 +/- 0.68 minutes in cirrhotics and controls, respectively. Similarly, estimates of skin blood flow (mL/min/100 g tissue) were 7.82 +/- 1.28 in the cirrhotic patients, not significantly different from those in both patients with mixed liver diseases (7.6 +/- 2.86) and control subjects (8.06 +/- 1.04). Parameters of skin blood flow were also invariant in respect to the various etiologies of liver disease. Thus, the present findings indicate that capillary skin blood flow is not affected by the hyperdynamic circulatory changes occurring in liver cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cholestyramine treatment on biliary lipid secretion rates in normolipidaemic men

This study was designed to clarify the effect of bile acid sequestrant treatment on the total biliary output rates of cholesterol, phospholipids and bile acids in man, and to correlate these changes with the alterations in plasma lipoprotein levels. For this purpose nine healthy, normolipidaemic men were treated with 16 g of cholestyramine daily over a period of 4 weeks, and the biliary secretion rates were measured by a duodenal perfusion technique. Resin therapy, which profoundly increases de novo synthesis of bile acids, resulted in a lowering of total plasma cholesterol levels, mainly due to a 35% reduction in low density lipoprotein (LDL) cholesterol, and in a 33% increase in plasma triglyceride levels, reflecting enhanced very low density lipoprotein (VLDL) triglyceride concentrations; high density lipoprotein (HDL) levels did not change. However, these lipoprotein changes did not correlate with any alterations in biliary lipid output. Total hepatic secretion rates of the biliary lipids remained generally unchanged during treatment, with a tendency towards lower cholesterol output, resulting in a lower molar percentage of cholesterol in hepatic bile, 3.4 +/- 0.4 vs. 2.9 +/- 0.2 mol %. This is probably due to an increased rate of conversion of cholesterol to bile acids in the hepatocyte. It is concluded that, in man, the liver may adapt well to changes in the enterohepatic circulation of bile acids, thereby maintaining output rates of biliary lipids at a relatively constant level.

Modulation of biliary lipid secretion by forskolin and cyclic AMP analogues

Exposure of isolated perfused rat livers to either 100 microM-forskolin, a potent activator of adenylate cyclase, or to 0.5 mM-concentrations of the cAMP analogues chlorophenylthio cAMP (CPTcAMP), dibutyryl cAMP (dbcAMP) and 8-bromo cAMP (8BrcAMP), to provoke increases in intracellular concentrations of cAMP, resulted in marked changes in bile volume and composition. Bile flow reached a peak after 10 min, before declining towards control levels, and an increase in several secretory parameters was also observed at this time. At 20 min, a substantial decrease in the output of both phospholipid and cholesterol was evident, and this suppression of secretion was maintained throughout the remainder of the experiment. The order of effectiveness of the cAMP-elevating agents at decreasing biliary lipid output was CPTcAMP greater than forskolin greater than dbcAMP greater than 8BrcAMP. Biliary output of bile acids was essentially unaltered compared with controls; similarly, no decrease in the secretion of protein and triacylglycerols into the perfusion medium was observed. This suggests that the elevation of intracellular levels of cAMP may cause a selective inhibition of biliary lipid output rather than a more general inhibition of hepatic secretion.

[Physiopathology of iron metabolism and hemochromatosis: interrelationships, assessment and pathogenesis of iron overload, screening]

Fundamental aspects of iron metabolism relate to the dynamic processes of metal plasma transport as well as cell storage and efflux. Transferrin not only carries iron in the plasma but also delivers it to the various cells by binding to a diffuse specific cell receptor; it also acts by chelating cell iron. Ferritin co-operates by storing iron in the cell. By a still unknown regulatory mechanism, iron, from the ferritin pool, is redistributed in the cell to a cytosolic, easily chelatable, "transit" pool or to a degradative lysosomal hemosiderin pool from which it is slowly released outside the cell. Iron overload, such as that typical of hyperhemolysis or hemochromatosis, profoundly impairs its metabolism by saturating and/or altering transferrin and ferritin, by freeing iron from any regulated transport, thus allowing parenchymal deposition and damage. An important aspect still awaiting clarification relates to the different storage of excess iron in the parenchymal cells, as in hemochromatosis, or in the reticuloendothelial system such as in hemosiderosis. Studies using cellular models attempt to evaluate such differences in terms of altered properties of the iron proteins or their cell receptors, and of the different cell responsivity to non-transferrin iron. In the expectation of better knowledge, attention should be concentrated, from a clinical standpoint, on precise assessment of iron deposits in the tissues with the aim of preventing its excessive accumulation and parenchymal damage. In hemochromatosis, the risk of iron overload is evaluated by HLA typing.

Pulse-chase studies of the synthesis of apolipoprotein B in a human hepatoma cell line, Hep G2

We have used pulse-chase methodology to study the synthesis of apolipoprotein B in a human hepatoma-derived cell line, the Hep G2 cells. A 2-min pulse with [35S]methionine was followed by a chase period varying from 5-90 min. A protein of large molecular mass (estimated molecular mass: 312 +/- 41 kDa, mean +/- SD, n = 8) could be immunoprecipitated from the cells at all chase periods between 5 min and 60 min with both monoclonal antibodies to a narrow density cut of the low density lipoprotein LDL-2 (density: 1.030-1.055 g/ml) and polyclonal antibodies to the apolipoprotein B apo B 100 or to a narrow density cut of LDL-2 (density: 1.030-1.055 g/ml). In addition to this large molecular mass protein, nascent polypeptides could be precipitated after 5, 10 and 15 min of chase. The apolipoprotein B molecules that had been labelled during the pulse disappeared from the cells after 60-90 min of chase, while they started to appear in the medium after 30-35 min of chase. The results obtained indicate (a) that apolipoprotein B is synthesized as one polypeptide with a large molecular mass, (b) that newly synthesized apolipoprotein B molecules are secreted after a delay of 30-35 min, (c) that no intracellular accumulation of apolipoprotein B occurs, and (d) that apolipoprotein B is recovered in the density fraction less than 1.21 g/ml of the medium suggesting that it is secreted in lipoprotein form.

A high recovery method for concentrating microgram quantities of protein from large volumes of solution

A method is presented for the recovery of 40-80% of the protein from a 1 microgram/ml solution. The final protein pellet is free of detergent and other ionic compounds and is thus compatible with any denaturing solution. The primary structure of the protein is unaffected by the procedure, making the final pellet an ideal sample for any analytical procedure to determine protein structure.

High affinity binding of chylomicron remnants to rat liver plasma membranes

The binding of chylomicron remnants rat liver plasma membranes was studied. Liver membranes bound up to 8 times more remnants than they bound chylomicrons. The remnant particle appeared to bind to the membrane as a unit. Remnant binding was greatest to liver plasma membrane; only one third as much binding was observed with whole liver homogenate, and virtually no binding occurred to erythrocyte membranes or glass. Binding was saturable and had kinetics compatible with the existence of a high affinity site. Half-maximal binding occurred at 27 micron. Competitive binding studies revealed no competition with albumin, a triglyceride dispersion, cholesterol/lecithin vesicles, very low density lipoprotein, or low density lipoprotein. Some displacement of remnant binding was observed with chylomicrons and high density lipoprotein. Binding was decreased by treatment of the membranes with trypsin or the presence of heparin in the incubation medium. These studies suggest that there is a high affinity receptor for the chylomicron remnant on the surface of the hepatocyte.

Urinary excretion of D-glucaric acid, total glucuronic acid and total porphyrins in porphyria cutanea tarda

The urinary levels of D-glucaric acid, which is an index of hepatic microsome induction, and the excretion of glucuronic acid and porphyrins were measured in nine patients with Porphyria Cutanea Tarda (PCT) and twelve normal controls. The excretion of D-glucaric acid and glucuronic acid were respectively 3.5 and two times higher in PCT patients compared to controls. A statistical correlation could be demonstrated between urinary excretion of total porphyrins with that of glucaric and glucuronic acids. These findings indicate that microsomal function and porphyrin metabolic derangement are strictly related in PCT.

Comparison of the effects of cholic acid and chenic acid feeding on rates of cholesterol synthesis in the liver of the rat

To compare the ability of cholic acid and chenic acid to suppress cholesterol synthesis in the liver, these two bile acids were fed in varying amounts to rats for either 66 hr or 6 weeks. In both instances there were significant changes in the bile acid pool in the small intestine and suppression of the rate of cholesterol synthesis in the liver. The administration of cholic acid, however, consistently produced greater suppression of the rate of cholesterol synthesis from octanoate or of microsomal HMG CoA reductase activity than did the administration of a similar amount of chenic acid. Furthermore, this difference was present whether the rates of cholesterogenesis were measured at high-substrate concentrations, ie, under conditions where Vmax was apparently achieved, or under circumstances where there was essentially no extracellular substrate present. These findings do not support the view that the superiority of chenic acid for dissolution of gallstones is secondary to its greater effect as an inhibitor of hepatic cholesterol synthesis.

Influence of fructose feeding on individual enzymic reactions in the formation and metabolism of bile acids in rat liver homogenates

1. Rats were maintained for 10 d on a semi-synthetic diet containing 700 g glucose or 700 g fructose/kg. Individual enzymic reactions in bile acid synthesis and metabolism were studied by measuring the 7alpha-hydroxylation of [4-14C]cholesterol, and 12alpha-hydroxylation of 7alpha-[6beta-3H]hydroxy-4-cholesten-3-one, the 26-hydroxylation of 5beta-[7beta-3H]cholestane-3alpha,7alpha-diol and the 6beta-hydroxylation of [3H]lithocholic acid in liver homogenates. 2. The serum cholesterol level was approximately the same in both groups of animals, but the serum triglyceride level was almost twice as high in the fructose-fed rats compared to the glucose-fed rats. 3. The 6beta-hydroxylation of [3H]ithocholic acid was increased by about 20% in the fructose-fed rats compared to the glucose-fed animals. The activities of the other enzymic reactions studied did not differ significantly between the two groups of animals. The findings are discussed in relation to previous knowledge concerning mechanisms regulating triglyceride, pre-beta-lipoprotein and bile acid synthesis.

The metabolism of steroids in the fatty liver induced by orotic acid feeding

1. The metabolism of 4-[4-14C]androstene-3,17-dione, 4-[4-14C]pregnene-3,20-dione, 5alpha-[4-14C]androstane-3alpha,17beta-diol, [4-14C]cholesterol, 7alpha-hydroxy-4-[6beta-3H]cholesten-3-one, 5beta-[7beta-3H]cholestane-3alpha,7alpha-diol and [3H]lithocholic acid was studied in the microsomal fraction of livers from control and orotic acid-treated male rats. 2. As a result of the treatment the orotic acid-fed rats had fatty livers and subnormal concentrations of cholesterol and triglycerides in serum. 3. The 6beta- and 7alpha-hydroxylation of 4-androstene3,17-dione, and the 2alpha-, 2beta- and 18-hydroxylation of 5alpha-androstane-3alpha,17beta-diol, and the 5alpha-reduction of 4-androstene-3,17-dione and 4-pregnene-3,20-dione were decreased by 40--50% in orotic acid-fed rats. Other oxidative and reductive reactions of the steroid hormones were not significantly affected. 4. The 12alpha-hydroxylation of 7alpha-hydroxy-4-cholesten-3-one was decreased by about 50%, whereas the 7alpha-hydroxylation of cholesterol and the 26-hydroxylation of 5beta-cholestane-3alpha,7alpha-diol were not significantly decreased. The 6beta-hydroxylation of lithocholic acid was stimulated by 40%. 5. The results are discussed in relation to present knowledge of the heapatic drug-metabolizing enzymes and to the recent findings of an abnormal bile acid metabolism in liver disease.

Dissociation of beta-hydroxy-beta-methylglutaryl-CoA reductase activity from the overall rate of cholesterol synthesis in the liver following the intravenous administration of lipid

After the intravenous administration to the intact rat of triglyceride carried in either intestinal lipoproteins or in an artificial fat emulsion, the enzymatic activities of microsomal beta-hydroxy-beta-methylglutaryl-CoA reductase activity in the liver assayed in vitro became markedly elevated. This elevation of enzyme activity was not associated with a corresponding change in the overall rate of cholesterol synthesis in the rat liver slice as measured by the incorporation of either [3H]water or [1-14C]octanoate into nonsaponifiable lipids or into digitonin-precipitable sterols. The degree of dissociation of hydroxymethylglutaryl-CoA reductase activity from the overall rate of cholesterol synthesis correlated closely with the amount of lipid administered to the animal, the level of circulating lipids, and the level of ketone synthesis manifest in the liver cell suggesting that this phenomenon might be the consequence of a detergent effect of elevated cellular levels of fatty acids. In any event, under these experimental circumstances hydroxymethylglutaryl-CoA redutase activity no longer reflects the rate at which the liver cell is synthesizing cholesterol.

ABO blood groups and serum gastrin

Serum gastrin concentrations were measured in 75 subjects of blood group O and in 75 subjects of other blood groups. Gastrinaemia both basally and following stimulation by glycine drink or by insulin hypoglycaemia did not show any statistically significant differenc in blood group O people as compared to subjects of other blood groups. It is concluded that the claimed relationship between blood group O and parietal cell hyperplasia cannot be considered as secondary to a relationship between blood group O and increased gastrin-producting G cell mass.

Effect of phenobarbital on MHV-3 viral hepatitis of the mouse

The effects of oral phenobarbital (PB) administration on MHV-3 viral hepatitis in the mouse were studied. PB was effective in increasing liver cytochrome P-450 level in infected animals at 72 h after virus inoculation, but did not affect the disease process of the liver viral infection as judged by changes in mortality rate, serum GOT, GPT and MDH levels and liver virus content.

Plasma disappearance and cerebral effects of chlorpromazine in cirrhosis

1. The plasma disappearance and cerebral effects of chlorpromazine were studied in twenty-four patients with compensated cirrhosis and in matched controls using a sensitive gas-liquid chromatography (g.l.c) technique to measure chlorpromazine. Plasma disappearance followed a double-exponential decay curve. No difference could be detected between cirrhotic and control groups, even when the effect of prior treatment with inducing drugs was considered, and only minor differences were observed when the elimination rate constants (kel) were calculated.

2. Chlorpromazine caused drowsiness in all subjects, together with slowing of EEG activity. The slowest activity, which was accompanied by impaired cerebration, occurred in those patients with a past history of encephalopathy in whom the value for the pretreatment skew mean-dominant-frequency was abnormally low.

3. The susceptibility of some patients with cirrhosis to chlorpromazine is probably due to increased sensitivity of cerebral neurones, rather than impaired hepatic drug metabolism.

Australia antigen in chronic liver disease

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The Australia (hepatitis-associated) antigen amongst heroin addicts attending a London addiction clinic

Thirty-three of 72 heroin addicts attending a recognized clinic for drug addition had a history of jaundice, but in only five was the serum positive for hepatitis-associated antigen (HAA) when examined by immunodiffusion, immunoelectro-osmophoresis and complement fixation. Two of these were repeatedly positive over an 8-12 month follow-up period and liver biopsy showed chronic persistent hepatitis. A third later developed acute hepatitis. A study of the injection habits suggested that the present low incidence of HAA and the decrease in number of cases with jaundice was probably related to the provision of free disposable syringes by the clinic since it was opened in 1968.