Hypertension And Heart Failure Flashcards
What is preload?
Pressure in the ventricles prior to contraction. The greater the pre-load, the greater the forcefulness of heart contraction.
What is afterload?
Peripheral resistance of the body that the heart must work against to contract in systole, altered by the tone of blood vessels.
What is end-diastolic volume?
Volume of blood left in the ventricles at the end of diastole before systole. The greater the EDV, the greater the pre-load.
What is stroke volume?
Volume of blood pumped out of the left ventricles of the heart during systole.
What is Frank-Starling relationship?
Relationship between pre-load and stroke volume.
Initially, increase in pre-load will lead to more forceful contraction and increase in stroke volume. However, excess increase in pre-load overstretches the muscle fibres and results in decrease in stroke volume. It is a disproportional relationship.
What happens when there is an increase in end diastolic volume?
Causes muscle contraction and increase in stroke volume.
What is cardiac output?
Cardiac output is the amount of blood pumped out of the heart, measured by the stroke volume (ml) x the heart rate (bpm) Normal cardiac output is 5L/min.
What are the types of heart failure?
Systolic heart failure and Diastolic heart failure.
What is ejection fraction?
The stroke volume as a proportion of the total volume of blood in the ventricles. Normal ejection fraction is 55-70% and is reduced in left sided heart failure.
What is systolic heart failure?
Typically affects the left ventricles, where the pumping function of the heart is insufficient, which results in a lower ejection fraction. It has 3 main causes:
Dilated cardiomyopathy
Ischaemic heart disease due to atherosclerotic plaque
Hypertension.
What is dilated cardiomyopathy?
Dilation/increase in the size of the heart chamber, which typically occurs after an infection.
This increases pre-load and stroke volume to a point, however the greater chamber size causes the thinning and weakening of the cardiac muscles that makes it unable to pump and causes systolic heart failure.
How does hypertension lead to heart failure?
Greater peripheral resistance and afterload means that the left ventricle must pump harder to overcome these forces, which leads to hypertrophy of the overworked muscles. This results in compression of the coronary arteries and a greater oxygen demand due to a larger size. The left ventricle will have weaker contraction and this will eventually result in systolic failure.
What is Left sided diastolic heart failure?
Issue with filling of the left ventricle, however the ejection fraction is preserved. It is caused by:
Aortic stenosis
Hypertension that reduces the space in the chamber
Restrictive cardiomyopathy
Kidney RAAS signalling
How does aortic stenosis lead to heart failure?
Narrowing of the aorta means there is reduced blood flow out of the heart so the left ventricle must pump harder, and this leads to hypertrophy of the left ventricle, reducing the space in the chamber for blood to fill and causes diastolic heart failure.
How does hypertension lead to diastolic heart failure?
There is concentric hypertrophy in the left ventricle, where the new sarcomere are parallel to existing sarcomeres that reduces the space in the chamber for blood to fill.
How does restrictive cardiomyopathy lead to heart failure?
Stiffened ventricles have reduced compliance that reduces the ability of the left ventricle to stretch and fill with blood, causing diastolic heart failure.
How does kidney disease lead to heart failure?
Reduced renal perfusion activates the RAAS system to cause more fluid retention and stimulate heart contractility and stroke volume.
However, this results in an excess fluid buildup which will leak out of blood vessels into tissues and cause oedema.
What is a consequence of left-sided heart failure?
Blood backs up into the pulmonary artery, which causes pulmonary artery hypertension and results in pulmonary oedema. Excess blood in the vessels reduces the rate of gas exchange between the alveoli and makes the vessels prone to rupture.
The blood that leaks is taken up by macrophages to form haemosiderin, brown as a result of iron accumulation.
What are the features of pulmonary oedema?
Dyspnoea
Orthopnoea
Paroxysmal nocturnal dyspnoea (intermittent SOB at night)
Crackles on auscultation.
How is pulmonary oedema treated?
Diuretics to remove the excess fluid build up from the body via urination
Oxygen supply, due to impaired gaseous exchange and ventilators support
Vasodilators such as:
—> Morphine: it reduces blood pressure by inducing vasodilation which also reduces pre-load
—>Nitrates
What is anarsca?
Severe generalised oedema of the body due to heart failure which develops over weeks and causes weight increase, ascites and pleural effusion.
What is the cause of right sided heart failure?
Right sided heart failure is also known as congestive heart failure, becauase blood will back up to the body and lead to oedema. It can occur due to:
Progression of left sided heart failure, where fluid will back up into the lungs and pulmonary artery
Arterial/ventricular septal defect
Chronic lung disease
Pulmonary embolism
What are causes of right sided heart failure unrelated to left-sided heart failure?
Atrial/ventricular septal defect, where high pressure blood from the Ieft moves to the right and results in pulmonary artery hypertension, concentric hypertrophy of the right side of the heart that causes ischaemia and reduced blood volume.
Lung disease creates state of hypoxia so the pulmonary artery compensates to take up more oxygenated blood via constriction, leading to right sided heart failure. This is cor pulmonale.
What does ascites indicate?
Fluid buildup in the peritoneal space due to oedema as a result of heart failure.
What is the consequence of right-sided heart failure?
Raised JVP
Fluid back up into the organs such as the spleen and liver, causing liver cirrhosis and oedema
Abdominal ascites
Pitting oedema
How is heart failure investigated?
Chest X-ray
Levels of pro-BNP
Echocardiogram