Closing the Digitalis Divide: Back to the Basics of Randomized Controlled Trials

PURPOSE

Publishe d decades after several randomized controlled trials (RCT) demonstrating decreased hospitalizations and no effect on all-cause mortality with digoxin use, a series of meta-analyses linking digoxin treatment and mortality have contributed to a narrower application of this medication for the management of heart failure (HF) and atrial fibrillation (AF). Given the conflicting data from the earlier RCTs and more recent meta-analyses, there is a growing polarization among providers for and against the use of digoxin in managing these conditions.

METHODS

To help close this divide, we provide a perspective on the literature with special attention to the quality of both older and more recent studies on this subject.

RESULTS

The data from the highest quality studies we have, RCTs, suggest that digoxin use in patients with HF and/or AF is associated with improvement in several areas of outcomes including functional capacity, symptom management, reduced hospitalizations, fewer deaths due to HF, and treatment of refractory chronic heart failure with rEF, and may even have overall mortality benefit when serum digoxin concentrations are within therapeutic range. These effects are more pronounced in patients with EF < 25% and NYHA Class II-IV and at highest risk for hospitalization.

CONCLUSION

As the risk of confounding factors was minimized by the study design, the likelihood that positive outcomes were identified with digoxin use increased. Clinicians and researchers need further adequately designed and powered RCTs exploring the connection between digoxin therapy and mortality, hospitalizations, and symptom management.

A digitális fonokardiográfia szerepe a kutyák szívhangjainak hallgatózásos vizsgálatának oktatásában

Absztrakt

Sok állatorvostanhallgatónak esik nehezére a szívhangok helyes értelmezése. Kutatásunk célja a digitális fonokardiogramokat felhasználó online, tanterven kívüli oktatás hatásának felmérése volt a hallgatók szívhangok felismerésével kapcsolatos diagnosztikai képességeire. Harminchat véletlenszerűen elosztott állatorvostanhallgató hallgatott meg és értelmezett 10 hangfelvételt élettani szívhangokról (2), szívzörejekről (4) és szívritmuszavarokról (4) egy négyhetes periódus elején és Végén. Huszonkét hallgató vett részt DPCG-ket felhasználó képzésben, egy önképző oldal (n = 12) és egy online webinar (n = 10) keretein belül. A két teszten elért eredményeiket egy kontrollcsoportéval vetettük össze (n = 14), akik nem vettek részt tanterven kívüli képzésben. Bár az elő- és utótesztek pontszámai nem különböztek szignifikánsan a csoportok között, mindkét oktatásban résztvevő csoport szignifikáns csoporton belüli javulást mutatott a két teszt között (p = 0,023, p = 0,037), míg a kontrollcsoport nem (p = 0,49). Bár egyik csoport sem ért el javulást az élettani szívhangok felismerésében és szívritmuszavaroktól való elkülönítésében, mindkét csoportban javulást láttunk a szívzörejek felismerésében és azonosításában, valamint az észlelt szívritmuszavarok azonosításában. Eredményeink alapján a hallgatók hallgatózásos vizsgálattal kapcsolatos diagnosztikai képességei javíthatóak tanterven kívüli oktatással, akár élő álatok igénybevétele nélkül is. További, nagyobb elemszámmal végzett, valamint DPCG-t nem használó oktatómódszereket alkalmazó kutatás szükséges a DPCG-k szerepének pontos meghatározásához. Egy emelt elemszámmal végzett kutatás lehetővé tenné továbbá egy kombinált oktatott csoport létrehozását, mérhetővé téve a két módszer kumulatív hatását.

This translation was provided by the authors. To view the original article visit: https://doi.org/10.3138/jvme-2021-0097

Continuous inbreeding affects genetic variation, phenology, and reproductive strategy in ex situ cultivated Digitalis lutea

PREMISE

Ex situ cultivation is important for plant conservation, but cultivation in small populations may result in genetic changes by drift, inbreeding, or unconscious selection. Repeated inbreeding potentially influences not only plant fitness, but also floral traits and interactions with pollinators, which has not yet been studied in an ex situ context.

METHODS

We studied the molecular genetic variation of Digitalis lutea from a botanic garden population cultivated for 30 years, a frozen seed bank conserving the original genetic structure, and two current wild populations including the source population. In a common garden, we studied the effects of experimental inbreeding and between-population crosses on performance, reproductive traits, and flower visitation of plants from the garden and a wild population.

RESULTS

Significant genetic differentiation was found between the garden population and the wild population from which the seeds had originally been gathered. After experimental selfing, inbreeding depression was only found for germination and leaf size of plants from the wild population, indicating a history of inbreeding in the smaller garden population. Moreover, garden plants flowered earlier and had floral traits related to selfing, whereas wild plants had traits related to attracting pollinators. Bumblebees visited more flowers of outbred than inbred plants and of wild than garden plants.

CONCLUSIONS

Our case study suggests that high levels of inbreeding during ex situ cultivation can influence reproductive traits and thus interactions with pollinators. Together with the effects of genetic erosion and unconscious selection, these changes may affect the success of reintroductions into natural habitats.

21-Hydroxypregnane 21-O-malonylation, a crucial step in cardenolide biosynthesis, can be achieved by substrate-promiscuous BAHD-type phenolic glucoside malonyltransferases from Arabidopsis thaliana and homolog proteins from Digitalis lanata

Three putative 21-hydroxypregnane 21-O-malonyltransferases (21MaT) from Digitalis lanata were partially purified. Two of them were supposed to be BAHD-type enzymes. We were unable to purify them in quantities necessary for reliable sequencing. We identified two genes in A. thaliana coding for substrate-promiscuous BAHD-type phenolic glucoside malonyltransferases (AtPMaT1, AtPMaT2) and docked various 21-hydroxypregnanes into the substrate-binding site of a homology model built on the BAHD template 2XR7 (NtMaT1 from N. tabacum). Recombinant forms of Atpmat1 and Atpmat2 were expressed in E. coli and the recombinant enzymes characterized with regard to their substrate preferences. They were shown to malonylate various 21-hydroxypregnanes. The Atpmat1 sequence was used to identify candidate genes in Digitalis lanata (Dlmat1 to Dlmat4). Dlmat1 and Dlmat2 were also expressed in E. coli and shown to possess 21-hydroxypregnane 21-O-malonyltransferase activity.

Aphidophagous hoverflies reduce foxglove aphid infestations and improve seed set and fruit yield in sweet pepper

BACKGROUND

Larvae of many hoverfly species prey upon aphids, whereas the adults, by relying on nectar and pollen, contribute to the pollination of many plant species. Despite their great potential for pest control and pollination, important gaps still exist regarding the efficacy of hoverflies in regulating infestations of major aphid pests in augmentative biological control programs. Here, we tested the potential of the commercially available hoverflies Eupeodes corollae and Sphaerophoria rueppellii to regulate populations of the foxglove aphid Aulacorthum solani in sweet pepper.

RESULTS

In a semi-field experiment, aphid numbers were 93.2% and 78.4% lower in the E. corollae and S. rueppellii treatments, respectively, compared to the control. Fruit yield was increased by 390% and 361% and seed set by 395% and 399% for E. corollae and S. rueppellii. In a separate laboratory trial, we found that under conditions of limited prey, hoverfly larvae did not complete development, but that larvae of S. rueppellii survived significantly longer than larvae of E. corollae.

CONCLUSION

We have shown for the first time that E. corollae and S. rueppellii can reduce infestations of foxglove aphid in sweet pepper. The limited amount of prey, related to the small size of the A. solani colonies, means that hoverfly larvae were often not able to complete development. In practice, repeated releases of hoverflies, possibly in combination with other natural enemies, might be used to achieve effective suppression of A. solani infestations. © 2021 Society of Chemical Industry.

[Optimization of digitalis therapy in clinical practice]

In recent years there has been a marked decrease in cardiac glycosides use in patients with heart failure in sinus rhythm and atrial fibrillation. The results of published studies contradict each other. Some of them doubt the favorable effect of digoxin in patients with heart failure; others refute the increase in the lethality and frequency of hospitalizations associated with the use of digoxin. In this regard, we found it important to analyze these reports impartially and reflect modern views on the mechanisms of cardiac glycosides, the pharmacokinetics and the possibility of optimizing digitalis therapy in cardiac practice.

A case report of near-fatal poisoning from Digitalis Purpurea accidentally confused with Borago Officinalis

A 58 years healthy old woman was admitted to the Emergency Department (ED) with cardiac arrest due to ventricular fibrillation (VF). Appropriate cardiopulmonary resuscitation (CPR), multiple DC shocks and oro-tracheal intubation (OTI) were effective to induce recovery of spontaneous circulation (ROSC). After ROSC was achieved, the electrocardiogram (ECG) showed an idio-ventricular rhythm with atrioventricular dissociation. A transcutaneous pacing was hence applied and the patient was administered with isoproterenol. Simultaneously, her husband was evaluated in the ED for gastrointestinal symptoms occurred after assumption of home-made "tortelli" (ravioli-like pasta) stuffed with cheese and leaves of a plant which they supposed to be borage two days before admission. Borage, during the non-flowering seasons, can be easily confused with foxglove (Digitalis spp.), and this was the main clue to suspect poisoning. Both patients were given DigiFab®, a sheep antibody fragment with high affinity for digoxin. The woman was then admitted in intensive care unit (ICU), where a rapid clinical  improvement occurred, thus allowing discharge in a few days. The husband was instead discharged from the ED after clinical observation and ECG monitoring. In both cases, a significant plasma concentration of digoxin could be measured.

Progesterone 5β-reductase genes of the Brassicaceae family as function-associated molecular markers

This study aimed to define progesterone 5β-reductases (P5βR, EC 1.3.99.6, enone 1,4-reductases) as function-associated molecular markers at the plant family level. Therefore cDNAs were isolated from 25 Brassicaceae species, including two species, Erysimum crepidifolium and Draba aizoides, known to produce cardiac glycosides. The sequences were used in a molecular phylogeny study. The cladogram created is congruent to the existing molecular analyses. Recombinant His-tagged forms of the P5βR cDNAs from Aethionema grandiflorum, Draba aizoides, Nasturtium officinale, Raphanus sativus and Sisymbrium officinale were expressed in E. coli. Enone 1,4-reductase activity was demonstrated in vitro using progesterone and 2-cyclohexen-1-one as substrates. Evidence is provided that functional P5βRs are ubiquitous in the Brassicaceae. The recombinant P5βR enzymes showed different substrate preferences towards progesterone and 2-cyclohexen-1-one. Sequence comparison of the catalytic pocket of the P5βR enzymes and homology modelling using Digitalis lanata P5βR (PDB ID: 2V6G) as template highlighted the importance of the hydrophobicity of the binding pocket for substrate discrimination. It is concluded that P5βR genes or P5βR proteins can be used as valuable function-associated molecular markers to infer taxonomic relationship and evolutionary diversification from a metabolic/catalytic perspective.

Rafael Méndez Martínez, pioneer in the pharmacological studies of digitalis and digitalis glycosides]

Since the end of the XVIII century, digitalis glycosides were employed in heart failure. They were considered initially as diuretics and later as cardiotonic agents or as positive inotropics. At the present time there are varied groups of positive inotropic agents, which have a beneficial action on the failing human myocardium. For example, the beta adrenergics, the phosphodiesterase III inhibitors such as milrinone, or the sensibilizers of myocardial proteins to Ca++ such as levosimendan and omecamtiv mecarbil. However, following the opinion of distinguished cardiologists, in the case of heart failure associated to atrial fibrillation, digitalis cannot be substituted.

A COMPARATIVE STUDY ON SOME PHARMACOLOGICAL EFFECTS OF DIGITOXIN, ACETYLDIGITOXIN AND GITALIN (AMORPHOUS) IN CATS

The lethal doses of digitoxin, acetyldigitoxin and gitalin were determined in cats. Electrocardiograms were recorded intermittently during the course of the repeated injections of these glycosides. Their relative lethal activities in cats were found to be similar to the reported relative therapeutic activities in man. Gitalin was found to be significantly more liable to cause cardiac arrhythmias than the other two glycosides.

Preliminary chemical examination of digitalis tissue cultures for cardenolides

Three Digitalis species were grown as callus or suspension tissue cultures, extracted and examined by paper chromatography. Kedde-positive substances (cardenolide glycosides) were found.

and of Allied Species

The total glycoside content and the nature of the individual glycosides in the leaves and inflorescences of Digitalis purpurea, D. lanata, D. lutea, D. thapsi and D. ambigua have been studied. A similarity in the chemical composition of the leaves and inflorescences of each species has been demonstrated. The yield of glycosides from D. purpurea and from D. thapsi would be increased by harvesting the entire aerial parts of the second year plants.

Digitalis: a dangerous drug in atrial fibrillation? An analysis of the SPORTIF III and V data

OBJECTIVE

In heart failure, digitalis increases exercise capacity and reduces morbidity, but has no effect on survival. This raises the suspicion that the inotropic benefits of digitalis may be counteracted by serious adverse effects. Patients with atrial fibrillation (AF) were studied to clarify this.

DESIGN

In the Stroke Prevention using an ORal Thrombin Inhibitor in atrial Fibrillation (SPORTIF) III and V studies, 7329 patients with AF at moderate-to-high risk were randomised to preventive treatment of thromboembolism, either with warfarin or the oral direct thrombin inhibitor ximelagatran. The survival of users and non-users of digitalis was investigated.

RESULTS

At baseline, 53.4% of the study population used digitalis, and these patients had a higher mortality than non-users (255/3911 (6.5%) vs 141/3418 (4.1%), p<0.001; hazard ratio (HR) = 1.58 (95% CI 1.29 to 1.94)). Digitalis users also had more baseline risk factors. After multivariate risk factor adjustment, the increased mortality persisted (p<0.001; HR = 1.53 (95% CI 1.22 to 1.92 vs 1.23 to 1.92)).

CONCLUSIONS

The results suggest that digitalis, like other inotropic drugs, may increase mortality. This may be concealed in heart failure, but be revealed in patients with AF, who need the rate-reducing effect of digitalis, but do not benefit much from an increased inotropy. Cautious interpretation of the data is mandatory since the patients were not randomised with respect to digitalis use.

Predictors of Mortality and Hospitalization in Women with Heart Failure in the Digitalis Investigation Group Trial

We performed a retrospective follow-up study of 1926 women with heart failure who participated in the Digitalis Investigation Group trial. Adjusted hazard ratios and 95% confidence intervals for covariates that were significant independent predictors of all-cause mortality were age in years (1.02; 1.01-1.03; P<0.001), NYHA class IH-IV (1.56; 1.31-1.87), diabetes (1.63; 1.36-1.95), glomerular filtration rate in mL/min/1.73 m(2) (0.99; 0.98-4).996; P=0.001), pulmonary congestion by chest x-ray (1.57; 1.22-2.02), left ventricular ejection fraction (LVEF) (0.99; 0.98-0.993; P<0.001), and use of digoxin (1.20; 1.02-1.42). Covariates that were significant independent predictors of hospitalization due to worsening heart failure were: nonwhite race (1.28; 1.03-1.58), NYHA class III-IV (1.55; 1.30-1.84), diabetes (1.75; 1.47-2.09), glomerular filtration rate as mL/min/1.73 m(2) (0.99; 0.986-0.996; P<0.001), pulmonary congestion by chest x-ray (1.42; 1.12-1.81), and use of ACE inhibitors (0.67; 0.49-0.91). Longer duration of heart failure, higher NYHA classes, diabetes, chronic kidney disease, pulmonary congestion, and lower LVEF were significant independent predictors of all-cause mortality, all-cause hospitalization, and hospitalization for heart failure in women with heart failure.

William Withering's legacy--for the good of the patient

The lessons that the physician William Withering learned from his studies of digitalis are still relevant today. This paper highlights four of these lessons and updates them using the tools of clinical pharmacology and pharmacoepidemiology. First, Withering learned that failure to prepare digitalis from the foxglove in a standard manner resulted in a product with unpredictable clinical effects. Preparation of medicines from plants since then has not followed similar good practice and medicines have often not been granted marketing authorisation because of variability in their quality. Second, differences in the response to digitalis were noted by Withering, but he had little idea of their basis. Clinical pharmacology has shown that for drugs such as digitalis differences are caused by variability both in receptor sensitivity and in drug disposition. Third, the dose-response characteristics of digitalis were well known to Withering. Modern techniques of measuring response, such as the use of biomarkers, have made such studies easier, although clinical observations remain the gold standard. Fourth, Withering documented many of the adverse effects of digitalis. The use of various modern databases has facilitated the analysis of clinical toxicology and thus of risk-benefit profiles.

Lunar Society and the discovery of digitalis

William Withering was an established member of the renowned Lunar Society as well as an accomplished physician and botanist. Withering was an obsessive note taker and had a compulsion to observe and record. At the time when bleeding was the most common form of treatment for "dropsy", Withering's discovery of the foxglove and his detailed description of its medicinal purposes represented a major advance in the treatment of patients with heart failure. Withering's scrupulous account of the foxglove's potential for treating conditions of the heart was derived from dedicated study, experimentation, and deep concern for detail. The publication of "An Account of the Foxglove, and Some of its Medical Uses: with practical remarks on dropsy, and other diseases" marks a defining moment in the history of medicine.