ILA3 Flashcards
What is cardiac output and
Cardiac output = stroke volume x heart rate
what variables contribute to CARDIAC output?
heart rate and stroke volume
what affects heart rate
- the firing rate of the sino atrial node (5 liters at rest and can be up to 25 liters).
- Which its self can be affected by normal responses e.g. adrenalin in the blood which act on beta 1- adrenalreceptors or nervous stimulation by the vagus nerve (para sympathetic) or sympathetic nerves which cause the release of hormones which affect the SAN. - Sympathetic Nervous System: Increases heart rate via noradrenalin (adrenalergic beta 1 receptor) acting on beta-1 adrenoreceptors found on the cells of the sinoatrial and atrioventricular node.
- There can also be hyper-excitability on the SAN caused by high extracellular potassium levels making the resting potential less negative so a lower stimulation is required to start an action potential. This is called an ion imbalance.
- Parasympathetic (usually muscarinic receptors) Nervous System: Decreases heart rate via acetylcholine acting on muscarinic receptors found on the cells of the sinoatrial and atrioventricular node.
- Other hormones such as adrenalin can also effect.
what affects stroke volume
t is affected by preload (the pressure of the blood on the ventricles at the end of diastole load before ventricular contraction) and after load (the pressure against which the heart is pumping) the formula is end diastolic volume- end systolic volume.
What factors affect blood pressure and how does this relate to cardiac output and the patient’s symptoms?
Factors that effect blood pressure are Smoking- increases heart rate, increase Genetic factors-family history Stress Age Ethnic Weight/diet (too much salt) Lack of exercise Chronic kidney disease
what is stroke volume
stroke volume is the amount of blood pumped out of the heart with each contraction. I
what is blood pressure
Blood pressure is the pressure of the blood in the circulatory system against the walls of the vessels, often measured for diagnosis since it is closely related to the force and rate of the heartbeat and the diameter and elasticity of the arterial walls. expressed in terms of the systolic (maximum) pressure over diastolic (minimum) pressure.
The hearts role is to maintain the pressure so that blood can be pumped around the body and supply nutrients to cells.
BP= CO x total peripheral resistance (how constricted arteries and arterioles are) as blood viscosity can change BP
Sympathetic→ constriction
parasympathetic → dilation on only smooth muscle.
Describe Starling’s law of the heart and relate this to heart failure. How does this link to this
man’s symptoms? What is the relevance of the left ventricular end diastolic volume?
Starlings law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart.
This is due to more blood in the ventricles causes an increase in stretch on the ventricle walls meaning cardiac myocytes contract with a greater force. Heart failure arises when the cardiac myocytes are to weak to increase contractibility when blood volume in the ventricles increase.
Therefore causing not enough blood to leave the heart and a constant problem
End diastolic volume is the pre load. It makes up 30% of the stroke volume. Without it the heart goes in to ventricular fibrillation. Increase in scar tissue after an MI would reduce contractibility as it does not stretch as well.
The ejection fraction is = SV end diastolic volume anything below 70 contractibility is not good enough.
Starlings law is that contraction pressure is directly proportional to stretch.
Describe the cardiac cycle in terms of atrial, ventricular and aortic pressures. When is the
myocardium perfused in a normal person?
It is all coordinated by the wave of excitation and also calcium calcium ions which travels down t-tubules and into the myocytes where they activate the sarcoplasmic reticulum which releases more calcium.
This calcium binds to troponin C which causes troponin I and T to move opening the active site allowing cross bridge formation.
Starts at point of maximum ejection. pressure rapidly decreases as ventricular diastole as pressure in aorta greater due to elastic recoil of the arteries, aortic valve shuts. Iso-volumetric relaxation.
The mitral valves open when pressure in ventricle is lower and blood fills via suction. It fills until the diastasis is reached where the pressure is equal so there is no net flow. The atrial boost fills the ventricle. Then from the apex upwards the ventricles iso-volumetric contraction. Rapid rise in pressure force open the aortic valve reaching maximum ejection.
The heart is perfused at the heart diastole. This is because blood always has to travel from a high to a low pressure. Ventricular systole is a high pressure.
What are the consequences of (a) an occlusion of the LAD and (b)
In general, the LAD artery and its branches supply most of the interventricular septum; the anterior, lateral, and apical wall of the left ventricle, most of the right and left bundle branches, and the anterior papillary muscle of the bicuspid valve (left ventricle). It also provides collateral circulation to the anterior right ventricle, the posterior part of the interventricular septum, and the posterior descending artery.
Importance in cardiovascular diseases:
The LAD artery is the most commonly occluded of the coronary arteries. It provides the major blood supply to the interventricular septum, and thus bundle branches of the conducting system. Hence, blockage of this artery due to coronary artery disease can lead to impairment or death (infarction) of the conducting system. The result is a “block” of impulse conduction between the atria and the ventricles known as “right/left bundle branch block.
What are the consequences of (b) an occlusion of right coronary artery, in terms of the territory affected, symptoms and effects on conduction?
Occlusion of the right coronary artery-
The coronary arteries supply blood to the posterior myocardium (heart tissue) itself; that is, coronary capillaries deliver oxygenated blood (nutrients) to all of the heart’s cells. Numerous clinically relevant arterial branches arise from the right coronary artery, including those that supply the conduction system.
Importance in cardiovascular diseases of occlusions:
Notably, the right coronary artery branches supply the sinus and atrioventricular nodes; hence, blockage in these vessels can lead to conduction abnormalities.
Coronary artery disease is generally defined as the gradual narrowing of the lumen of the coronary arteries due to atherosclerosis.
Atherosclerosis is a condition that involves thickening of the arterial walls via cholesterol and fat deposits that build up along the endoluminal surface of the arteries.
With severe disease, these plaques may become calcified, increase in size, and eventually cause significant stenosis; a stenotic vessel has an increased vascular resistance relative to that of healthy vessels.
A steady decrease in arterial cross-sectional area can eventually lead to complete blockage of the artery.
As a result, oxygen and nutrient supply to the myocardium decreases below the level of demand. As the disease progresses, the myocardium downstream from the occluded artery can become ischemic.
You now have this gentleman in clinic and you have to counsel him on some of the lifestyle changes he must make in order to reduce his future risk of having heart problems. What would you advise him?
the following life style changes would help reduce the risk;
• reduce smoking. Quit if possible.
• increase exercise amount and regular.
• Keep your total cholesterol level below 4 mmol/l.
• Keep your blood pressure below 140/90 mmHg.
• Keep to a healthy weight and body shape.
• Eat a healthy, well-balanced diet.
• Drink alcohol within recommended limits.
• Learn ways to manage stressful situations.
• Avoid recreational drug use.
• stick to medication prescribed
• up-to date immunizations
Medication used to treat heart attacks may include:
Beta-blockers - these are designed to reduce pressure on the heart by decreasing the amount of work the heart has to do. Beta-blockers lower the blood pressure and can also be used to treat angina and to prevent further heart attacks in patients who have previously suffered a heart attack. Beta-blockers can also be used to treat patients with an irregular heart rhythm.
Angiotensin-converting enzyme (ACE) inhibitors - these drugs lower blood pressure and help to relieve strain on the heart.
Nitrates - these drugs help to ease pain and relax the blood vessels.
Anticoagulants - these drugs help to prevent clotting by thinning the blood.
Antiplatelet medication - these drugs help to prevent platelets clustering together to create clots and are administered to people who have experienced a heart attack and those who have had an angioplasty and experience angina.
Glycoprotein llb-llla - these are very strong antiplatelet medications given intravenously.
Pain-relief medication.
Medication to reduce anxiety.
Oxygen therapy.
Medication to treat irregular heart rhythms
