Pregnancy-induced remodeling of heart valves.

Recent studies have demonstrated remodeling of aortic and mitral valves leaflets under the volume loading and cardiac expansion of pregnancy. Those valves' leaflets enlarge with altered collagen fiber architecture, content, and cross-linking and biphasic changes (decreases, then increases) in extensibility during gestation. This study extends our analyses to right-sided valves, with additional compositional measurements for all valves. Valve leaflets were harvested from nonpregnant heifers and pregnant cows. Leaflet structure was characterized by leaflet dimensions, and ECM composition was determined using standard biochemical assays. Histological studies assessed changes in cellular and ECM components. Leaflet mechanical properties were assessed using equibiaxial mechanical testing. Collagen thermal stability and cross-linking were assessed using denaturation and hydrothermal isometric tension tests. Pulmonary and tricuspid leaflet areas increased during pregnancy by 35 and 55%, respectively. Leaflet thickness increased by 20% only in the pulmonary valve and largely in the fibrosa (30% thickening). Collagen crimp length was reduced in both the tricuspid (61%) and pulmonary (42%) valves, with loss of crimped area in the pulmonary valve. Thermomechanics showed decreased collagen thermal stability with surprisingly maintained cross-link maturity. The pulmonary leaflet exhibited the biphasic change in extensibility seen in left side valves, whereas the tricuspid leaflet mechanics remained largely unchanged throughout pregnancy. The tricuspid valve exhibits a remodeling response during pregnancy that is significantly diminished from the other three valves. All valves of the heart remodel in pregnancy in a manner distinct from cardiac pathology, with much similarity valve to valve, but with interesting valve-specific responses in the aortic and tricuspid valves.

Physiological remodeling of the mitral valve during pregnancy.

There is growing evidence that heart valves are not passive structures but can remodel with left ventricular dysfunction. To determine if these tissues remodel under nonpathological conditions, we examined the mirtal valve anterior leaflet during the volume loading and cardiac expansion of pregnancy using a bovine model. We measured leaflet dimensions, chordal attachments, and biaxial mechanical properties of leaflets collected from never-pregnant heifers and pregnant cows (pregnancy duration estimated from fetal length). Hydrothermal isometric tension (HIT) tests were performed to assess the denaturation temperature (T(d)) associated with collagen molecular stability and the load decay half-time (t(1//2)) associated with intermolecular cross-linking. Histological changes were examined using Verhoeff-van Gieson and picrosirius red staining with polarized light. We observed striking changes to the structure and material properties of the mitral anterior leaflet during pregnancy. Leaflet area was increased 33%, with a surprising increase (nearly 25%) in chordae tendinae attachments. There was a biphasic change in leaflet extensibility: it rapidly decreased by 30% and then reversed to prepregnant values by late pregnancy. The 2°C decrease in T(d) in pregnancy was indicative of collagen remodeling, whereas the 70% increase in HIT t(1/2) indicated an increase in collagen cross-linking. Finally, histological results suggested transient increases in leaflet thickness and transient decreases in collagen crimp. This remodeling may compensate for the increased loading conditions associated with pregnancy by normalizing leaflet stress and maintaining coaptation. Understanding the mechanisms of mitral valve physiological remodeling in pregnancy could contribute to alternative treatments of pathological remodeling associated with left ventricular dysfunction.

Depiction of seizure first aid management in medical television dramas.

OBJECTIVES: The objective of this study was to investigate whether medical television dramas portray proper seizure first aid. METHODS: Episodes of the four highest-rated US medical dramas ("Grey's Anatomy," "House M.D.", "Private Practice," and "ER") were screened for the presence of seizures. "Patient" age, sex, semiology, and etiology were recorded. The appropriateness of seizure first aid management was determined by comparison to the Epilepsy Foundation of America (EFA) guidelines. RESULTS: Among 364 television programs, 65 seizures (in 59 individuals) were identified (30 males; 29 females). Seizures were primary or secondarily generalized tonic-clonic in 53 (81.5%) cases. Other seizure types included complex partial (5, 7.7%), simple partial (1, 1.5%), myoclonic (1, 1.5%), absence (1, 1.5%), and psychogenic (1, 1.5%). On 63 occasions (96.9%), first aid was performed by a health care professional. First aid management was judged appropriate in 21 (32.3%) seizures, inappropriate in 28 (43.1%), and indeterminate in 16 (24.6%). Inappropriate practices included holding the person down (17, 26.2%), trying to stop the involuntary movements (10, 15.4%) and putting something in the person's mouth (11, 16.9%). CONCLUSIONS: The first aid management of seizures performed by actors portraying health care professionals was inappropriate in nearly half of all cases. Inaccurate depiction of seizure first aid management may contribute to misinformation of the general public. The television industry could easily incorporate the simple first aid EFA seizure guidelines as a public service without sacrificing dramatic impact.

COVID-19 and Myocarditis: What Do We Know So Far?

COVID-19 has been declared a global pandemic by the World Health Organization and is responsible for hundreds of thousands of deaths worldwide. COVID-19 is caused by SARS-CoV-2, and common clinical symptoms include fever, cough, sore throat, headache, and fatigue. Myocardial injury is relatively common in patients with COVID-19, accounting for 7%-23% of cases, and is associated with a higher rate of morbidity and mortality. There is a discrepancy in the literature about myocarditis as the etiology of myocardial injury in patients with COVID-19; although many anecdotal reports of myocarditis have been noted, there are only a handful of case reports in the literature about myocarditis related to COVID-19. In this review we summarize the most up to date literature around the association between COVID-19 and myocarditis and provide clinicians a practical framework about the clinical manifestations, diagnostic tools, and treatment options currently available. Importantly, this review will heighten suspicion for myocarditis as an etiology of myocardial injury in COVID-19 patients, therefore improving clinical outcomes and encouraging shared clinical decision-making. This will also open the door for further research to build around this review. Emergent treatment options for COVID-19 are in clinical trials and might be of benefit to COVID-19 patients with myocarditis in addition to current guideline-based recommendations.

La COVID-19 a été déclarée pandémie mondiale par l'Organisation Mondiale de la Santé et elle est responsable de centaines de milliers de décès dans le monde. La COVID-19 est causée par le SARS-CoV-2, et les symptômes cliniques courants sont la fièvre, la toux, le mal de gorge, les maux de tête et la fatigue. Les lésions myocardiques sont relativement fréquentes chez les patients atteints de la COVID-19, représentant 7 à 23 % des cas, et sont associées à un taux de morbidité et de mortalité plus élevé. Il existe des divergences dans la littérature décrivant la myocardite en tant qu'étiologie de lésions myocardiques chez les patients atteints de la COVID-19; bien que de nombreux rapports anecdotiques de myocardite aient été rapportés, il n'y a qu'un nombre limité de rapports de cas dans la littérature concernant des myocardites liées à la COVID-19. Dans cette revue de littérature, nous résumons la bibliographie la plus récente sur l'association entre COVID-19 et myocardite et fournissons aux cliniciens un cadre pratique sur les signes cliniques, les outils de diagnostic et les options de traitement actuellement disponibles. Il est important de noter que cette revue augmentera la suspicion de myocardite comme étiologie de lésions myocardiques chez les patients atteints de la COVID-19, améliorant ainsi le pronostic clinique et encourageant une prise de décision clinique partagée. Cela ouvrira également la voie à d'autres recherches qui pourront s'appuyer sur cette étude. De nouvelles options de traitement de la COVID-19 sont en cours d'essais cliniques et pourraient être bénéfiques aux patients atteints de la COVID-19 qui présentent une myocardite, tout en étant considérées pour les recommandations actuelles basées sur les lignes directrices.

Biaxial Creep Resistance and Structural Remodeling of the Aortic and Mitral Valves in Pregnancy.

Pregnancy produces rapid, dramatic volume-overload changes to the maternal circulation. This paper examines pregnancy-induced structural-mechanical changes in bovine aortic and mitral heart valve leaflets. Valve leaflets were harvested from non-pregnant heifers and pregnant cows. Dimensions, biaxial extensibility and creep resistance were assessed and related to changes in the collagen network: histological leaflet and anatomic layer thicknesses plus collagen crimp, and biochemical collagen content. Collagen stability and crosslinking were assessed thermomechanically. Pregnancy altered both aortic and mitral valve leaflets. Both valves demonstrated biphasic changes in leaflet stretch, decreasing in early pregnancy and recovering by late pregnancy. Creep in leaflets from both valves was minimal and decreased even further with pregnancy in the mitral valve. There were valve-specific changes in preconditioning areal extension with pregnancy: increasing in the aortic valve and decreasing in the mitral valve. Leaflet area increased dramatically (84% aortic, 56% mitral), with thickening mainly in the fibrosa, accompanied by increases in collagen content (8% aortic, 16% mitral): together suggesting synthesis of new collagen. Collagen crimp was almost completely lost in pregnancy, with the denaturation temperature decreased by approximately 2 °C. Mature and total crosslinking increased, curiously without a significant increase in immature crosslinking. Mature aortic and mitral heart valve leaflets in the maternal cardiovascular system remodel substantially and similarly-despite their different embryological origins.