Cardiac & Skeletal Muscle Diseases

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Questions and Answers

What type of muscle is characterized as involuntary and contains nonstriated cells with a centrally located nucleus?

Cardiac muscle

Cartilage muscle

Skeletal muscle

Smooth muscle (correct)

Which condition is specifically associated with a temporary reduction of blood supply leading to reversible myocardial cell injury?

Heart attack

Acute Coronary Syndrome

Ischemic Heart Disease (correct)

Congestive Heart Failure

Which of the following statements about skeletal muscle contraction is accurate?

Skeletal muscle contraction is myogenic.

Skeletal muscle fibers are striated and cylindrical. (correct)

Skeletal muscle fibers can contract without nerve impulses.

Skeletal muscle does not contain actin and myosin.

In the context of cardiac disorders, what does CHF primarily indicate?

Decreased ability to pump blood Signup and view all the answers

What is the most common underlying cause of ischemia in ischemic heart disease?

Atherosclerosis Signup and view all the answers

What type of muscle activity is under voluntary control?

Skeletal muscle Signup and view all the answers

Which therapy is commonly indicated for managing Congestive Heart Failure (CHF)?

Angiotensin-converting enzyme (ACE) inhibitors Signup and view all the answers

Which of the following describes the contraction mechanism of cardiac muscle?

Termed myogenic Signup and view all the answers

What does acute coronary syndrome (ACS) encompass?

Conditions causing reduced blood flow to the heart Signup and view all the answers

Which type of muscle can be further classified into fast-twitch and slow-twitch fibers?

Skeletal muscle Signup and view all the answers

What is the primary characteristic of cardiomyopathy?

Inadequate muscle contraction due to direct damage to myocardium cells Signup and view all the answers

Which of the following is NOT a category of muscle disorder?

Genetic muscular syndromes Signup and view all the answers

What is a key characteristic of muscular dystrophy?

Progressive weakness and degeneration of skeletal muscle Signup and view all the answers

Which genetic change is primarily associated with Duchenne's muscular dystrophy?

Deletion of the dystrophin gene Signup and view all the answers

What defines an ideal cardiac marker for myocardial infarction (MI)?

Abundant in myocytes, low in blood, and persists for diagnosis Signup and view all the answers

What happens to cardiac myocytes during necrosis?

They lose membrane integrity and release intracellular components into blood circulation Signup and view all the answers

What is a common feature of cardiac biomarkers?

They should be minimal in concentration in blood under normal conditions Signup and view all the answers

Why is gene therapy considered for Duchenne's muscular dystrophy?

It is a prime candidate for targeting the dystrophin gene defect Signup and view all the answers

In what way are cardiac biomarkers monitored post-injury?

To establish a high rate of diagnosis based on plasma levels Signup and view all the answers

What is the primary characteristic of a myocardial infarction (MI)?

It causes irreversible ischemic injury resulting in cell death. Signup and view all the answers

What role do cTnT and cTnI play in the diagnosis of myocardial infarction?

They serve as the cornerstone for MI detection. Signup and view all the answers

In which time frame do CK-MB or troponin levels typically become elevated after chest pain onset?

4 to 6 hours after onset. Signup and view all the answers

What is the sampling sequence recommended for blood analysis after MI is suspected?

2 to 4 hours, 6 to 8 hours, and 12 hours after suspected MI. Signup and view all the answers

Which of the following statements about CK-MB is accurate?

It is one of three isoenzymes that include CK-MM and CK-BB. Signup and view all the answers

What distinguishes troponin from CK-MB in terms of diagnostic capabilities?

Troponin is more sensitive and specific for cardiac injury than CK-MB. Signup and view all the answers

What is a potential diagnostic challenge when analyzing CK levels during MI?

CK levels may rise and fall without exceeding normal limits. Signup and view all the answers

How do cardiac biomarkers like troponins assist specifically in acute coronary syndrome (ACS)?

Troponins assist in diagnosing and risk assessing ACS. Signup and view all the answers

Which characteristic makes CK-MB particularly useful in diagnosing myocardial infarction?

It is found in high concentrations in myocardium. Signup and view all the answers

What does an initial elevation of CK-MB and normal total CK indicate during an MI?

The presence of myocardial damage. Signup and view all the answers

What is the primary advantage of cTnI compared to CK-MB in clinical applications?

cTnI remains elevated longer in blood. Signup and view all the answers

Which statement about cTnT after myocardial infarction (MI) is accurate?

cTnT increases in serum after 4 hours. Signup and view all the answers

What is a key characteristic of myoglobin as a biomarker for myocardial infarction?

Myoglobin levels can rise within 1 to 2 hours after symptoms start. Signup and view all the answers

Compared to CK-MB, how does the cardiac specificity of cTnI impact its diagnostic use?

cTnI is less affected by skeletal muscle injury. Signup and view all the answers

What is the duration of elevation for cTnI and cTnT after an acute myocardial infarction?

cTnI for 3 to 7 days; cTnT for 1 to 6 days. Signup and view all the answers

Why might elevated CK-MB not be a reliable diagnostic indicator in all patients?

CK-MB can increase due to skeletal muscle injury. Signup and view all the answers

Which of the following correctly outlines the release kinetics of troponins after myocardial infarction?

Troponin levels can remain elevated significantly longer than CK-MB. Signup and view all the answers

What condition would NOT lead to elevated cTnI levels?

Chronic renal failure requiring dialysis. Signup and view all the answers

After how many hours can cTnT peaks typically be observed post-MI?

Between 1 to 6 days. Signup and view all the answers

Study Notes

Cardiac & Skeletal Muscle Disease, and Muscle Biomarkers

Presentation date: 17-18/12/2024
Presenter: Dr. Halil Resmi

Muscle Anatomy and Function

Three types of muscle: skeletal, cardiac, smooth
Skeletal muscle: unbranched, cylindrical cells arranged in parallel bundles
Skeletal muscle fibers: run the entire length of the muscle
Skeletal muscle contraction: neurogenic (initiated by nerve impulses)
Two skeletal muscle types: fast-twitch, slow-twitch (differ in biochemical nature)
Cardiac muscle: found exclusively in the heart
Cardiac muscle: contains actin and myosin filaments
Cardiac muscle contraction: myogenic (involuntary control)

Cardiac Disorders

Ischemia: inadequate blood supply to an organ
Atherosclerosis: most common cause of ischemia
Atherosclerosis: cholesterol deposits in arterial walls, occluding the artery
Ischemic diseases: range from unstable angina (reversible myocardial cell injury) to frank myocardial infarction (large areas of necrosis).
Acute Coronary Syndrome (ACS): block or severe reduction of blood flow to the heart muscle. Damages the heart muscle. Heart attack and unstable angina are types of ACS.
Congestive Heart Failure (CHF): disease related to decreased blood pumping capability.
CHF: spectrum of diseases from left ventricular dysfunction (LVD) to overt CHF.
CHF therapy: angiotensin-converting enzyme (ACE) inhibitors.

Cardiomyopathy

Cardiomyopathy: characterized by inadequate muscle contraction due to myocardial cell damage, resulting in heart failure.
Cardiomyopathy manifestation: enlargement of all four heart chambers and heart failure.

Skeletal Muscle Disorders

Skeletal muscle diseases: characterized by motor function issues like muscular weakness.
Muscle disorders categories: neurogenic muscular atrophies, muscle fiber disorders (myopathies), disturbances of neuromuscular junctions.

Disorders of Muscle Fibers: Muscular Dystrophies

Muscular dystrophy: group of genetic, chronic muscle diseases.
Muscular dystrophy characteristics: progressive weakness and skeletal muscle degeneration without neural degeneration.
Muscular dystrophy inheritance: varies among types.
Muscular dystrophy factors: age of onset, disease course, fiber type effects vary among individual types.

Pseudohypertrophic Muscular Dystrophy (DMD)

DMD: most common muscular dystrophy.
DMD genetic defect: deletion in the dystrophin gene resulting in a defective dystrophin protein.
DMD serum CK enzyme: greatly elevated even before symptoms appear.
DMD treatment: currently no effective treatment, considered a prime candidate for gene therapy.

Changes of Analytes in Disease

Myocardiocyte Biomarkers

Necrotic cardiac myocytes: lose membrane integrity, intracellular components enter the bloodstream.
Cardiac biomarkers: collectively known molecules detectable in peripheral circulation
Ideal cardiac biomarker: abundant in myocytes, low in blood, released early after injury, absent in nonmyocardial tissues.
Direct relation: between plasma level of cardiac marker and myocardial injury effect.
Marker persistence: sufficient length in blood for high-rate diagnosis, easy, inexpensive, and rapid measurement.

Definition of Myocardial Infarction (MI)

MI: damaging process where ischemic injury is irreversible, leading to cell death and necrosis.
MI diagnosis: clinical history, ECG interpretation, serum cardiac-specific biomarker measurement (cTnT and cTnI now cornerstone for MI detection).

Cardiac Biomarkers in MI

CK-MB or troponin: elevated in blood 4 to 6 hours post-chest pain onset
Biomarkers diagnostic value: 8 to 12 hours post-presentation
Temporal pattern of CK-MB changes: helpful to distinguish uncomplicated MI from extension/reinfarction.

Creatine Kinase (CK) & Creatine Kinase MB (CK-MB)

CK-MB: first cardiac biomarker to meet many criteria.
CK-MB: one of three isoenzymes arising from total creatine kinase (CK).
Total CK: dimeric enzyme composed of two subunits (“M” for muscle, “B” for brain).
CK isoenzymes: CK-MM, CK-BB, CK-MB.
CK-MB: high concentration in myocardium

Cardiac Biomarkers in MI (cont.)

MI diagnosis: requires blood sample analysis at specific intervals (2-4 hours, 6-8 hours, 12 hours).
Sampling intervals adjustments permitted: if early samples were negative and clinical suspicion index was high.
Elevated CK-MB (normal total CK): possible in initial MI course.
CK values rise and fall: in some cases, do not exceed the upper limit.

Cardiac Biomarkers in Coronary Disease

Troponin (T&I): noticeably more sensitive and specific for cardiac injury than CK-MB.
Troponins: preferred biomarker for cardiac disease.

Diagnostic Use of Cardiac Troponins

Troponin: plays a vital role in diagnosis and risk assessment in ACS.
Troponin release kinetics: similar to CK-MB after MI.
Troponin: remains elevated in blood for 4 to 10 days after MI.
Low troponin values (without cardiac disease): permit use of lower discriminatory values to determine MI.
Troponin cardiac specificity: helps eliminate diagnostic uncertainty caused by increased CK-MB due to skeletal muscle injury.

Cardiac Troponin I (cTnI)

cTnI: lower molecular weight than cTnT and CK-MB, similar release kinetics and early MI indicator.
Clinical applications: similar to cTnT, measurement offers advantage over CK-MB.
cTnI elevation duration: 3 to 7 days after acute MI.
Diagnostic comparison (with CK-MB): comparable diagnostic sensitivity for initial (48-72 hours), cTnI improved sensitivity from 72 to 96 hours post MI.
cTnI: not elevated in patients with extreme skeletal muscle injury.

Cardiac Troponin T (cTnT)

cTnT: increases in serum after 4 hours of MI.
cTnT peak/plateau: 1 to 6 days, with a second peak possible ("bound fraction").
cTnT clinical sensitivity: similar to CK-MB in first 48 hours post-chest pain onset.
cTnT extended life in serum: provides information on recent myocardial dysfunction history.

Sensitivity & Specificity of Cardiac Markers

Chart of marker characteristics (first detection, duration of detection, sensitivities, specificities for Myocyte Necrosis.)
Myoglobin: presence in both cardiac and skeletal muscle, limiting diagnostic specificity, early marker for MI, rise detectable 1 to 2 hours post-symptom onset.
Myoglobin: not cardiac-specific (renal failure, injury, skeletal muscle disease); presence of myoglobinuria confirms muscle cell damage.

CK & CK Isoenzymes in Non-MI Conditions

CK isoenzyme pattern (non-MI conditions): not a rise and fall pattern, but rather chronically elevated levels;
Specific examples: Duchenne muscular dystrophy, polymyositis, rhabdomyositis demonstrate increased CK-MB levels in serum.
Total CK levels in skeletal muscle: 5-10 fold higher than cardiac muscle, leading to significantly higher total CK levels in conditions other than MI compared to those observed in MI. Chart demonstrating CK value increases in various muscular pathology conditions.

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Description

This quiz covers the anatomy and function of skeletal and cardiac muscles, as well as common disorders associated with these muscle types. It also delves into muscle biomarkers and the implications of conditions like ischemia and atherosclerosis. Test your knowledge on how these diseases affect muscle physiology.