General Introduction and Physiology Flashcards
What are the components of the heart? What are some associated diseases?
Myocardium, endocardium, pericardium, valves, large vessels, fat tissue (in the pericardium and surrounding the main coronary arteries), coronary arteries, generation and
conduction system.
Pericarditis affecting the pericardium, endocarditis affecting the endocardium and valves, aortic dissection and dissection affecting large vessels, arrhythmias related to the conduction system, valve disease affecting the valves, cardiomyopathies affecting the myocardium.
What is the definition of heart failure?
It is the inability of the heart to provide the needed amount of oxygen and metabolites according to the changing body needs. It is defined as congestive HF because of a clinical manifestation. It’s caused by work overload, which can occur as a consequence of : pulmonary hypertension, valve disease, MI, CDM, severe systemic diseases, arrhythmia’s, endocarditis.
What are some systemic causes of heart failure?
Chronic kidney disease, hemochromatosis, amyloidosis, thyroid dysfunction, anorexia, systemic infection. All metabolic disturbances such as diabetes can also cause HF.
Where does most of the cardiac output go?
The kidneys take up 20-22% of cardiac output, so heart and kidneys are strictly correlated functionally. The kidney communicates an increased need of blood through the RAAS. Heart disease in most of the cases is a systemic disease. In case of a failing heart, the kidney could go into prerenal failure (insufficient amount of blood reaching the kidney).
The brain receives 14% of cardiac output. Brain natriuretic peptide (BNP) was originally isolated from the brain but is produced in large amounts by the left ventricle. BNP is a very important marker of cardiac function and high levels could indicate heart failure.
What is the main important function of the heart valves?
Valve function guarantees unidirectional flow, therefore, if valves are impaired, the unidirectional function is impaired as well. In presence of regurgitation there will be back flow, while stenosis causes an insufficient flow.
What is the pathway of the cardiac conduction system?
Starts in the SA node then the AV node followed by the bundle of His which divides in right and left bundle, lastly the purkinje fibers reach each single cell.
What is hypertrophy and what are the two types?
Hypertrophy is an increase in volume of myocytes, there are two types: concentric hypertrophy (due to pressure overload, with “in parallel” myocytes), resulting in a wall thickening; and eccentric hypertrophy (due to volume overload, with “in series” myocytes), resulting in dilation of the chamber.
Why does the septum contract before the free walls?
Thickness of RV is 2-3mm (3-4 in an adult), so very thin and
producing low blood pressure; if the septum was
not standing still and contracted in the middle,
the LV would push the right one. Therefore the
septum separates the two chambers in terms of
pressure (to sum up: septum is activated, stands
still, while the other two walls contract at their
own pressures, without interference).
What happens in a left bundle block?
In case of a left bundle branch block (left bundle
not conducting) in order for the heart to keep
beating, the impulse goes down and activates the
left side by continuity, with a sort of delay. Therefore, in presence of a failing heart, the occurrence of a left bundle branch block decreases the cardiac output. So, the correct activation of the conduction system is crucial for the performance of the heart.
What is cardiac resynchronization therapy?
For patients with severe heart failure who develop a left branch block, CRT is used as a effecting strategy which by means of several electrodes (one in the atrium, one stimulating the RV, and another one stimulating the LV ) recreates the synchrony.
Why is a pacemaker inserted in the right ventricle if the left is the most important?
Pressure in a vein is a couple of mmHg (few more if there’s
a vein congestion), while the pressure in an artery is much greater. Indeed, if you puncture an artery the patient will die due to bleeding. This is the reason why in order to pace the LV you must go from right to left.
What is an ECG?
It examines how depolarization events occur in the heart. The electrical activity is measured by means of the ECG. The average signal recorded in the ECG is 1.5 millivolt. That’s the reason why the patient must stay still during an ECG, because a very tiny current is recorded, therefore skeletal muscle current and interferences must be avoided.
How is the cardiac output measured?
Heart rate (beats/min) x stroke volume. To measure HR take the radial/carotid pulse, to measure stroke volume : end diastolic volume - end systolic volume which can be measured with an echocardiogram.
What is the ejection fraction and how is it measured?
It is the measurement, in percentage, of how much blood the LV ejects in each systole. Normal ejection fraction is between 55% and 65%.
You could have patients with a normal EF and heart failure. This is because both the EDV and ESV could be lower causing a seemingly normal EF but a very low stroke volume and cardiac output.
What is the rate pressure product?
It is a way to calculate the physical stress a heart is under. It is given by BP x HR. Ex. 120 x 60 = 7200
