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Related Concept Videos

Hypersensitivities01:30

Hypersensitivities

7.8K
Hypersensitivity, also known as a hypersensitivity reaction or allergic reaction, is a condition where the body's immune system reacts abnormally to a foreign substance. Such substances, that cause hypersensitivity are referred to as an allergen, could be something typically harmless to most people, like pollen or certain foods.
Types of Hypersensitivities
Hypersensitivity reactions are categorized into four types: Type 1, Type 2, Type 3, and Type 4. Each type has a distinct mechanism...
7.8K
Hypersensitivity Reactions: Delayed Hypersensitivity Reactions01:29

Hypersensitivity Reactions: Delayed Hypersensitivity Reactions

18
Delayed-Type Hypersensitivity (DTH), or Type IV hypersensitivity, is a cell-mediated immune response. It occurs when T cells, rather than antibodies, mediate a reaction to specific antigens. It is characterized by a delayed onset (1-2 days) and involves the recruitment of macrophages to the inflammation site.The initiation of a DTH response begins with the sensitization of T cells. During this phase, which lasts at least 1-2 weeks, antigen-specific T cells are activated, clonally expanded, and...
18
Hypersensitivity Reactions: Cytolytic Reactions01:01

Hypersensitivity Reactions: Cytolytic Reactions

18
Type II hypersensitivity involves IgG and IgM antibodies targeting cell surface antigens, leading to cell destruction. This can occur through complement activation, antibody-dependent cell-mediated cytotoxicity (ADCC), or acting as opsonins for phagocytosis. When excessive, these reactions cause significant tissue damage.Drug-induced hemolytic anemia is a common example, where drugs like penicillin or cephalosporins bind to red blood cells, forming drug-protein complexes. These complexes...
18
Hypersensitivity Reactions: Immune-Complex Reactions01:19

Hypersensitivity Reactions: Immune-Complex Reactions

18
Type III hypersensitivity reactions occur when antigen–antibody complexes form and activate the complement system. Normally, these complexes help the clearance of antigens by phagocytes and red blood cells. However, when large numbers of immune complexes are present, they can deposit in tissues—particularly in the walls of blood vessels—leading to inflammation and tissue injury. These deposits trigger complement activation and neutrophil recruitment, resulting in serum...
18
Block Diagram Reduction01:22

Block Diagram Reduction

574
The process of deriving the transfer function of a control system often involves reducing its block diagram to a single block. This simplification can be achieved through a series of strategic operations, including relocating branch points and comparators. These operations preserve the overall function of the system while allowing for easier manipulation and combination of blocks.
The first step in this process is the identification and relocation of a branch point. A branch point, where a...
574
Elements of Block Diagrams01:25

Elements of Block Diagrams

737
Block diagrams serve as a visual representation of the input-output relationships within a system. An illustrative example is a heating system, where the set temperature activates the furnace to warm the room to the desired level. Block diagrams are versatile, modeling linear systems through Laplace transform variables and nonlinear systems using time domain variables.
A block diagram typically includes essential elements such as comparators, blocks, and feedback loops. Each of these elements...
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Related Experiment Video

Updated: Feb 15, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
12:45

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

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Afterload Hypersensitivity in Patients With Left Bundle Branch Block.

John Aalen1, Petter Storsten1, Espen W Remme2

  • 1Institute for Surgical Research, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Center for Cardiological Innovation, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.

JACC. Cardiovascular Imaging
|January 24, 2018
PubMed
Summary

Patients with left bundle branch block (LBBB) show increased sensitivity to elevated afterload, leading to significant reductions in left ventricular ejection fraction (LVEF). This hypersensitivity is linked to impaired septal function in the dyssynchronous ventricle.

Keywords:
dyssynchronyheart failurehypertensionleft bundle branch blockmyocardial workstrain

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Area of Science:

  • Cardiology
  • Cardiovascular Physiology
  • Echocardiography

Background:

  • Epidemiological data link left bundle branch block (LBBB) to heart failure in hypertensive patients.
  • LBBB may predispose individuals to adverse cardiac remodeling and dysfunction.

Purpose of the Study:

  • To investigate the hypothesis that patients with LBBB exhibit hypersensitivity to elevated afterload.
  • To elucidate the mechanisms underlying the adverse effects of increased afterload in LBBB.

Main Methods:

  • Echocardiography (LVEF, GLS) in 11 LBBB patients and 11 controls.
  • Systolic arterial pressure increased via pneumatic constrictors and handgrip exercise.
  • LV pressure-dimension analysis in 8 anesthetized dogs with induced LBBB and aortic constriction.

Main Results:

  • Elevated afterload moderately reduced LVEF in controls (60% to 54%).
  • In LBBB patients, similar afterload increase caused a substantial LVEF reduction (56% to 42%).
  • Dog model showed abolished septal shortening and negative septal work during aortic constriction.

Conclusions:

  • Moderate afterload elevation markedly reduced LVEF and GLS in LBBB patients.
  • This reflects a cardiodepressive effect of afterload in dyssynchronous ventricles.
  • Loss of septal function contributes to impaired ventricular work during increased afterload.