PBL 5 Flashcards
What type of drug is Ramipril? In basic terms, what does it do?
Ramipril is an ACE inhibitor. It lowers blood pressure by inhibiting Angiotensin Converting Enzyme
What type of drug is Atenolol? What does it do?
Atenolol is a selective beta1 receptor antogonist - a beta blocker. This makes the heart resistant to sympathetic stimulation, thereby avoiding a high heart rate that could cause a cardiovascular event.
What type of drug is Atorvastatin? What does it do?
Atorvastatin is a Statin. It is used for lowering cholesterol. Atorvastatin in a competitive inhibitor of HMG Co-A reductase, the rate-determining enzyme in cholesterol biosynthesis.
What types of food and drink should you have/not have with Atorvastatin?
- Avoid alcohol
- Avoid taking grapefruit/grapefruit juice throughout the treatment. Grapefruit can significantly increase serum levels of this product.
- Take with a low fat meal
- Avoid drastic changes in dietary habit
What is automaticity?
Automaticity: this describes the property of cardiac muscle, which can contract on its own in the absence of neural or hormonal stimulation.
What is the electrical system of the heart called?
The conducting system: aka cardiac conduction system or nodal system: a network of specialised cardiac muschle cells that initiate and distribute electrical impulses.
What elements does the conducting system of the heart contain? (7)
- The sinoatrial node (SA node) located in the wall of the right atrium
- The atrioventricular node (AV node) located at the junction between the atria and the ventricles
- Conducting cells, which interconnect the two nodes and distribute the contractile stimulus through the myocardium
- Internodal pathways: distribute the contractile stimulus to atrial muscle cells as the impulse travels from the SA to the AV node
- The AV bundle, the bundle branches and the Purkinje fibres are the ventricular conducting cells which distribute the stimulus to the ventricular myocardium.
What special characteristic do cells of the AV node and cells of the SA node share?
Conduciting cells of the SA and AV node: their excitable membranes cannot maintain a stable resting potential. After each repolarisation, their membranes gradually depolarise. This is called prepotential or pacemaker potential.
How does the heart beat if the SA node is damaged? How does the heart beat if both the SA node and the AV node are damaged?
If any of the atrial pathways or the SA node become damaged, the heart will continue to beat, but at a slower rate, usually 40-60bpm, as dictated by the AV node.
Certain cells in the Purkinje fibre network depolarise spontaneously at an even slower rate, and if the rest of the conducting system is damaged, they can stimulate the heart rate if 20-40bpm.
At what point does the rate of an electrical impulse slow down in a healthy heart?
The rate of propagation of the impulse slows as it leaves the internodal pathway and enters the AV node, becasue the nodal cells are smaller in diameter than the conducting cells.
After the AV node, which structures does the electrical impulse of the heart move through?
After the AV node, the impulse is conducted along the interventricular bundle and bundle branches to the Purkinje fibres and the papillary muscles. The Purkinje fibres then distribute the impulse to the ventricular myocardium, and ventricular contraction begins.
What is the maximum heart rate and why? Why is this limitation important?
230bpm. This is the maximum rate that cells of the AV node can conduct impulses. Because each impulse in a ventricular contraction, this value is the maximum normal heart rate. Even if the SA node generates impulses at a faster rate, the ventricles will still contract at 230bpm. This limitation is important, becasue mecanical factors begin to decrease the pumping efficiency of the heart at rates above approx 180bpm.
What is the difference between the two bundle branches?
The left bundle branch, which supplies the massive left ventricle, is much larger than the right bundle branch.
What is the ST segment?
The ST segment represents the period when the ventricles are depolarized.
What can ST elevation indicate?
ST elevation may indicate myocaridal infarction.
On an ECG which are the anterior leads?
V1-V4, which are pre-cordial leads, electrodes directly attached to the chest.
What is the guideline for diagnosing ST elevation type MI by ECG?
The current guidelines for the ECG diagnosis of the ST segment elevation type of acute MI require at least 1mm (0.1mV) of ST segment elevation in the limb leads, and at least 2mm elevation in the precordial leads.
What is Clopidogrel?
Clopidogrel is an antiplatelet agent and is used to reduce aterosclerotic events
What is the very basic MOA of a tissue plasminogen activator?
It activates plasminogen and converts it into Plasmin, which is a serine protease that acts to dissolve fibrin blood clots.
What ratio of blood lipids is a good predictor of coronary artery disease?
The total cholesterol to HDL-C ratio is a strong predictor of coronary artery disease and high ratios are associated with higher risk of disease. Increased levels of HDL-C are associated with lower cardiovascular risk
What blood lipid measurements are associated with increased risk of atherosclerosis and cardiovascular disease?
High LDL-C, low HDL-C and high TG concentrations in the plasma are associated with increased risk of atherosclerosis and cardiovascular disease
Where does atorvastatin primarily work? What happens here?
Atorvastatin acts primarily in the liver.
Decreased hepatic cholesterol levels increases uptake of cholesterol by the liver and reduces plasma cholesterol levels.
When is atorvastatin a primary measure, when a secondary measure?
Atorvastatin may be used as
- primary prevention in individuals with multiple risk factors for coronary heart disease (CHD) and
- secondary prevention in individuals with CHD to reduce the risk of myocardial infarction (MI), stroke, angina, and the need for revascularization procedures (bypass, angioplasty)
How does atorvastatin interact with HMG-coA Reductase?
Atorvastatin selectively and competitively inhibits the hepatic enzyme HMG-CoA reductase
