Chem 6 Flashcards
(40 cards)
What are cardiovascular diseases considered in developed countries?
Leading cause of mortality
Rising tendency in developing countries; accounts for approximately 50% of all deaths in modern western societies.
What is the significance of biochemical markers in diagnosing acute cardiac ischaemia?
Used alongside history of chest pain and ECG changes
Role commenced in the 1950s; established markers include AST, CK, CK-MB, LD-1, and Myoglobin.
What is a cardiac biomarker?
Protein molecules released into the bloodstream from damaged heart muscles
List the characteristics of an ideal cardiac marker of myocardial infarction (MI).
- Abundant in myocytes and low in blood
- Released rapidly during myocardial injury
- Direct relationship between plasma level and myocardial injury extent
- Persistent in blood for sufficient diagnosis time
- Easy, inexpensive, and rapid measurement
- Heart-specific and sensitive
- Differentiate irreversible from reversible damage
- Detect re-occlusion and reinfarction
- Monitor reperfusion therapy
What are the functions of cardiac biomarkers?
- Risk stratification
- Detection of reinfarction
- Diagnosis
- Prognosis
- Monitoring response to therapy
Define myocardial infarction (MI).
Combination of typical symptoms, rise in biochemical marker levels, and typical ECG pattern involving Q waves
What is the recommended protocol for diagnosing MI using cardiac markers?
Serial sampling at presentation, 6-9 hours, and again at 12-24 hours if earlier samples are negative
What is the time sequence for the rise in plasma cardiac markers after acute myocardial infarction?
- Creatine Kinase (total): 4-6 hours, peaks at 24-48 hours, lasts 3-5 days
- Aspartate aminotransferase: 6-8 hours, peaks at 24-48 hours, lasts 4-6 days
- Lactate dehydrogenase: 12-24 hours, peaks at 48-72 hours, lasts 7-12 days
- Myoglobin: 2-4 hours, peaks at 12-24 hours, lasts 2-4 days
- Troponin: 4-6 hours, peaks at 12-24 hours, lasts 7-10 days
What are the classifications of cardiac biomarkers?
- Biomarkers of myocardial injury
- Biomarkers of haemodynamic stress
- Inflammatory and prognostic biomarkers
What is the clinical utility of aspartate transaminase (AST)?
First cardiac marker, used in hepatocellular disorders and skeletal involvement; not useful for diagnosing AMI
When does myoglobin rise in relation to myocardial infarction?
Detectable in blood as early as 1 to 2 hours after onset of symptoms
What is the function of creatine kinase (CK)?
Catalyzes conversion of creatine to phosphocreatine, degrading ATP to ADP
What are cardiac troponins?
Complex of three regulatory proteins integral to muscle contraction; includes Troponin-C, Troponin-T, and Troponin-I
What conditions are associated with elevated cardiac troponin levels?
- Arrhythmias
- Congestive heart failure
- Coronary vasospasm
- Systemic and pulmonary hypertension
- Myocarditis and Pericarditis
- Pulmonary embolism
- Renal failure
- Sepsis/septic shock
- Hypothyroidism
What is Ischemia Modified Albumin (IMA)?
A novel marker produced when serum albumin contacts ischemic heart tissues, rises within 6 hours and remains elevated for 12 hours
What are the functions of natriuretic peptides (NP)?
Regulate diuresis and natriuresis, responsible for salt and water homeostasis and blood pressure
What is the difference between ANP and BNP?
- ANP: released in response to atrial wall stretching
- BNP: secreted by the ventricles
What causes elevated levels of natriuretic peptides?
Volume expansion and pressure overload of the heart
What are physiological antagonists of the effects of Angiotensin II?
• Vascular tone
• Aldosterone secretion
• Renal-tubule sodium reabsorption
• Vascular-cell growth
Angiotensin II is a hormone that increases blood pressure and fluid retention.
What is Brain Natriuretic Peptide (BNP) originally isolated from?
Porcine brain
BNP is now also discovered in the human heart.
In which conditions are circulating levels of BNP raised?
• Cardiovascular disease
• Renal disease
BNP is more important than ANP in heart failure.
What is the greatest proportion of circulating BNP thought to come from?
The ventricles
This indicates the heart’s role in BNP production.
List cardiac causes for elevated natriuretic peptide levels.
• Heart failure (including RV syndromes)
• Acute coronary syndrome
• Heart muscle disease (including LVH)
• Valvular heart disease
• Pericardial disease
• Atrial fibrillation
• Myocarditis
• Cardiac surgery
• Cardioversion
• Restrictive cardiomyopathy
Elevated BNP can indicate various cardiac conditions.
List noncardiac causes for elevated natriuretic peptide levels.
• Advancing age
• Anemia
• Renal failure
• Pulmonary causes (obstructive sleep apnea, severe pneumonia, pulmonary hypertension)
• Critical illness
• Bacterial sepsis
• Severe burns
• Toxic-metabolic insults (including cancer chemotherapy and envenomation)
Noncardiac factors can also significantly elevate BNP levels.
