Cardiovascular System: Diagnostic Tests - Labs - Medical-Surgical | @LevelUpRN

Summary

In this video, Cathy from Level Up RN provides an in-depth overview of diagnostic tests related to the cardiovascular system, focusing on key lab values like cardiac enzymes, cholesterol, blood pressure, and clotting factors. She explains important tests such as CK-MB, myoglobin, and troponin, highlighting their role in diagnosing heart issues like myocardial infarctions. Cathy also covers platelet counts, hemoglobin levels, and coagulation tests, offering mnemonics to aid in memorizing values. At the end of the video, a quiz reinforces learning with questions about specific lab values and their significance in diagnosing cardiovascular conditions.

Takeaways

• 😀 Cardiac enzymes such as CK-MB, myoglobin, troponin T, and troponin I are key diagnostic tests for heart ischemia and myocardial infarction.
• 😀 CK-MB is a cardiac enzyme that rises within 3-6 hours of heart damage and remains elevated for 2-3 days.
• 😀 Myoglobin is a protein found in heart and skeletal muscles, but its elevation can indicate damage to either, not just the heart.
• 😀 Troponin T and I are highly specific for heart muscle damage, with troponin T elevated for 2 weeks and troponin I for 1 week after an infarction.
• 😀 Cholesterol levels are essential for cardiovascular health, with total cholesterol ideally under 200, LDL under 130, and HDL higher than 45 for men and 55 for women.
• 😀 Blood pressure should ideally be under 120/80, and ranges for hypertension stages vary across sources, requiring a check with textbooks or professors.
• 😀 Common blood values like red blood cells, platelets, hemoglobin, and hematocrit are important in assessing cardiovascular and overall health.
• 😀 aPTT, PT, INR, and D-dimer are key tests for monitoring clotting and diagnosing conditions like DVT or pulmonary embolism.
• 😀 hBNP levels are elevated in heart failure due to fluid overload causing heart stretch, with values above 100 indicating possible heart failure.
• 😀 The quiz at the end helps reinforce key concepts: Troponin is the most specific enzyme for heart ischemia, platelets should range between 150,000 and 400,000, and D-dimer levels rise in the presence of a clot.

Q & A

What are cardiac enzymes, and why are they important?

Cardiac enzymes are proteins released into the bloodstream when there is damage to the heart muscle, such as during a myocardial infarction. These enzymes, including CK-MB, myoglobin, troponin T, and troponin I, help diagnose heart damage and ischemia.

What is the significance of CK-MB in diagnosing heart damage?

CK-MB is an enzyme found in cardiac muscle that is released when the heart muscle is damaged. Its levels typically rise within 3 to 6 hours after damage and can remain elevated for up to 2 to 3 days, making it a useful marker for recent heart muscle injury.

How is myoglobin used in diagnosing heart damage, and what are its limitations?

Myoglobin is a protein found in both heart and skeletal muscle, and it is released when these muscles are damaged. It can indicate heart damage, but since it is not specific to the heart, it can also be elevated in cases of skeletal muscle injury. It rises within 2 to 3 hours of damage and stays elevated for about 24 hours.

Why is troponin considered the gold standard for diagnosing myocardial infarction?

Troponin is a protein found in heart muscle fibers and is highly specific to heart muscle damage. It rises 2 to 3 hours after an infarction and can remain elevated for up to two weeks, making it the most reliable marker for diagnosing myocardial infarction.

What are the normal ranges for troponin T and troponin I?

Troponin T should be under 0.1, and troponin I should be under 0.03. Elevated levels of these markers indicate heart muscle damage.

What is the ideal cholesterol level for a patient, and what do LDL and HDL represent?

The total cholesterol level should be under 200 mg/dL. LDL (low-density lipoprotein) is the 'bad' cholesterol, ideally under 130 mg/dL (or under 100 mg/dL for high-risk patients), while HDL (high-density lipoprotein) is the 'good' cholesterol, ideally above 55 mg/dL for females and 45 mg/dL for males.

What blood pressure readings indicate normal levels versus hypertension?

Normal blood pressure is a systolic value under 120 and a diastolic value under 80. Hypertension stages vary, but blood pressure readings of 120-129 systolic and under 80 diastolic are considered elevated, while stage 1 hypertension starts at 130/80 and higher.

What is the purpose of monitoring aPTT in patients on heparin?

aPTT (activated partial thromboplastin time) is used to monitor clotting time and ensure that patients on heparin have appropriate anticoagulation. The normal range is 30 to 40 seconds, but for patients on heparin, this is expected to be extended to 45 to 80 seconds.

What are the normal values for red blood cells, platelets, hemoglobin, and hematocrit?

Red blood cells should be between 4.2-5.4 million/µL for females and 4.7-6.1 million/µL for males. Platelets should range between 150,000 and 400,000/µL. Hemoglobin levels should be between 12-16 g/dL for females and 14-18 g/dL for males. Hematocrit should be 37-47% for females and 42-52% for males.

What does an elevated D-dimer indicate?

An elevated D-dimer (usually under 0.4 µg/mL) indicates the presence of a clot, such as in deep vein thrombosis (DVT) or pulmonary embolism (PE), as it is a product of fibrin breakdown in clot formation.