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Related Concept Videos

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The human heart is a complex organ with an intricate system of valves that regulate blood flow. There are two main types of valves: atrioventricular (AV) valves and semilunar valves.
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An experiment is a planned activity carried out under controlled conditions. The purpose of an experiment is to investigate the relationship between two variables. When one variable causes change in another, we call the first variable the explanatory or independent variable. The affected variable is called the response or dependent variable. In a randomized experiment, the researcher manipulates values of the explanatory variable and measures the resulting changes in the response variable. The...
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When conducting an experiment, it is crucial to have control to reduce bias and accurately measure the dependent variables. It also marks the results more reliable. Controls are elements in an experiment that have the same characteristics as the treatment groups but are not affected by the independent variable. By sorting these data into control and experimental conditions, the relationship between the dependent and independent variables can be drawn. A randomized experiment always includes a...
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Randomized Experiments01:13

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Related Experiment Video

Updated: Feb 3, 2026

Biaxial Mechanical Characterizations of Atrioventricular Heart Valves
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Thirty-year experience with a bileaflet mechanical valve prosthesis.

Scott Johnson1, Martha R Stroud1, John M Kratz1

  • 1Division of Cardiothoracic Surgery, Medical University of South Carolina, Charleston, SC.

The Journal of Thoracic and Cardiovascular Surgery
|October 22, 2018
PubMed
Summary

Long-term follow-up of St. Jude mechanical valve prostheses shows reliable outcomes. Annual monitoring identified valve-related issues, confirming prosthesis durability over three decades.

Keywords:
St Jude Medicalaortic valvemechanical valve prosthesismitral valvevalve replacement

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Area of Science:

  • Cardiovascular Surgery
  • Biomaterials Science
  • Medical Device Evaluation

Background:

  • The St. Jude Medical mechanical valve prosthesis has been implanted since 1979.
  • Evaluating long-term patient outcomes is crucial for understanding device performance.

Purpose of the Study:

  • To assess the long-term clinical outcomes of St. Jude Medical mechanical valve prosthesis implantation.
  • To determine the durability and complication rates associated with this prosthetic valve over an extended period.

Main Methods:

  • A cohort of 1023 patients receiving St. Jude mechanical valves between 1979 and 2014 were followed annually.
  • Data collected included operative mortality, late survival, and freedom from reoperation, thromboembolism, valve thrombosis, bleeding, and endocarditis.

Main Results:

  • Thirty-year actuarial survival rates were 14% ± 3% for both aortic and mitral valve replacements.
  • Thirty-year freedom from reoperation was 92% ± 2% (aortic) and 85% ± 5% (mitral).
  • Incidence of bleeding and thromboembolism were reported per patient-year for both valve positions.

Conclusions:

  • Annual follow-up facilitated the identification of valve-related issues and events.
  • The St. Jude Medical mechanical valve prosthesis demonstrates reliability over three decades of clinical observation.