Evaluation of Clinical Practices Related to Variants of Uncertain Significance Results in Inherited Cardiac Arrhythmia and Inherited Cardiomyopathy Genes

Background:

Increasing use of genetic tests have identified many variants of uncertain significance (VUS) in genes associated with inherited arrhythmias and cardiomyopathies. Evaluation of clinical practices, including medical management recommendations for VUS patients and their families, is important to prevent over- or under-treatment that may result in morbidity or mortality. The purpose of this study is to describe practices related to VUS results including information and medical management recommendations providers give patients and their families.

Methods:

An anonymous online survey was distributed to genetic counselors (GCs) and cardiologists who have seen at least one patient for inherited arrhythmias or cardiomyopathies. The survey explored providers’ confidence in counseling, explanation of VUSs, topics covered before and after genetic testing, and clinical recommendations using a hypothetical scenario maximizing uncertainty with an unclear clinical and molecular diagnosis. Descriptive statistics were calculated, and median confidence and likelihood of making various medical recommendations were compared across provider type.

Results:

Providers (N=102) who completed the survey included 29 cardiovascular GCs, 50 GCs from other specialties, and 23 cardiologists. GCs feel more confident than cardiologists counseling about VUS results ( P <0.001); while both cardiovascular GCs and cardiologists feel more confident than other GCs in providing input regarding medical management recommendations ( P =0.001 and P =0.01, respectively). Cardiologists were more likely than cardiac GCs to recommend clinical testing for family members even though testing in the scenario is expected to be uninformative.

Conclusions:

These findings illustrate how the expertise of different providers may impact decision processes, suggesting the need for interdisciplinary clinics to optimize care for challenging cases.

Cretaceous vertical motion of australia and the australian- antarctic discordance

A three-dimensional model of mantle convection in which the known history of plate tectonics is imposed predicts the anomalous Cretaceous vertical motion of Australia and the present-day distinctive geochemistry and geophysics of the Australian-Antarctic Discordance. The dynamic models infer that a subducted slab associated with the long-lived Gondwanaland-Pacific converging margin passed beneath Australia during the Cretaceous, partially stagnated in the mantle transition zone, and is presently being drawn up by the Southeast Indian Ridge.

Effect of monensin on the performance of cattle on pasture or fed harvested forages in confinement

Three series of trials were conducted to evaluate the effect of monensin on the growth performance of cattle. Twenty-four trials were conducted to evaluate the addition of monensin at 200 mg/d to limited quantities of supplemental concentrate for growing cattle grazing pastures. The pastures ranged from dormant end-of-the-season grasses and crop residues to lush green pastures, and were located in several different states. Pasture plus supplement supported gains of control cattle (without monensin) of .24 to .96 kg, with an average of .56 kg/d. The addition of 200 mg monensin to the supplement increased daily gain in all 24 trials by an average of .09 kg daily (+16.3%). Eleven trials were conducted with monensin and energy supplements fed at .907 kg.- head-1 X d-1 to growing cattle grazing growing, nondormant pastures for an average period of 117 d. Each trial was designed to compare the performance of unsupplemented cattle, cattle fed a supplement and cattle fed a supplement with monensin. Cattle on pasture gained .50 kg daily. Supplement feeding increased average daily gain by .09 kg and the addition of monensin to the supplement further increased gain by .09 kg, for a total increase of .18 kg (34.2%). The efficiencies with which supplemental feed was converted to extra gain (kg supplement/kg gain) for the supplement-only and the monensin treatment groups were 10.1:1 and 5.0:1, respectively. In a series of 12 trials, monensin was added at a level of 33 mg/kg air-dry diet to limited quantities of supplemental feed for cattle fed harvested forages in confinement. All trials compared monensin feeding with a nonmedicated control treatment. Hay was fed in 8 of the 12 trials, fresh-cut green-chop in two trials and ensiled corn stover and ensiled milo stover in one trial each. Monensin reduced feed intake by -3.1%, improved average daily gain by .09 kg (+14.4%) and improved feed efficiency by 15.3%.

Administration of monensin in self-fed (salt limiting) dry supplements or on an alternate-day feeding schedule

Two series of trials were conducted to evaluate alternative methods of administering monensin to pasture cattle. In a series of five trials, monensin was incorporated into supplements at 440 mg/kg to provide an average intake of 200 mg X head-1 X d-1 for growing cattle on pasture. Comparisons were made between daily and alternate-day feeding of the supplements. A control treatment consisting of unmedicated supplement fed daily also was included. Monensin at 200 mg/d and 400 mg on alternate days increased gain by .077 (P less than .01) and .082 (P less than .01) kg/d above control-cattle gains (.54 kg daily). Nine pasture trials were conducted to compare the effectiveness of monensin in increasing the daily gain of growing cattle when hand-fed daily in a supplement or self-fed in supplements that contained salt to regulate supplement intake. Desired supplement intakes were approximately .454 kg X head-1 X d-1 in six trials, .68 kg/d in one trial and 1.81 kg/d in two trials. Monensin produced gain increases of .09 kg daily (P less than .01) with both feeding systems. The daily gains of cattle that were hand-fed and self-fed were equal (P greater than .10). Self-fed treatments containing monensin required fewer changes in salt level than self-fed treatments not containing monensin, and the salt levels required to limit intake were generally 25 to 50% lower when monensin was in the supplement.

Effect of monensin and tylosin on average daily gain, feed efficiency and liver abscess incidence in feedlot cattle

Fourteen trials were conducted to evaluate the effects of feeding monensin at 33 ppm alone, tylosin at 11 ppm alone and the two feed additives in combination on the average daily gain, average daily feed intake, feed:gain ratio and the incidence of liver abscesses in feedlot cattle. Monensin reduced feed intake and improved feed efficiency (P less than .05), and had no effect on average daily gain. Tylosin improved average daily gain (P less than .05) and had no effect on daily feed intake. The effect of tylosin on feed efficiency approached significance. The interaction of monensin and tylosin was nonsignificant for daily gain, daily feed intake and feed:gain ratio. Monensin had no effect on liver abscess incidence, while tylosin reduced abscess incidence from 27 to 9%.

Leucine imbalance in corn-soybean meal diets for laying hens

Three experiments were conducted to study leucine X isoleucine X valine interactions in hens fed low-protein, corn-soybean meal diets. Addition of 0.75% L-leucine to diets containing 10 to 12% protein resulted in less feed intake and lowered production that could be overcome only by the addition of both 0.175% L-isoleucine and 0.35% DL-valine. Hens fed diets containing 16% and 19% protein were unaffected by the addition of as much as 2.25% L-leucine. Reduction of protein by dextrose dilution of high-protein diets resulted in improved performance when compared with regular low-protein diets because of the better amino acid balance in the diluted diets. This response was not correlated with the leucine content of the low-protein diets. It was concluded that the possibility of a leucine X isoleucine X valine interaction impairing the performance of hens fed low-protein corn-soymeal diets is very remote.