Cardiac Physiology Flashcards
Primary regulation of heart rate and blood pressure are controlled where?
Medulla
What effect do the following have on calcium? Volatile anesthetics Nitrous oxide Local anesthetics Acidosis Digitalis
Volatile anesthetics = decrease Nitrous oxide = decrease Local anesthetics = decrease Acidosis = decrease Digitalis = increase
Parasympathetic fibers primarily innervate what?
Atria and conducting tissues
Where do the cardiac Excelerator fibers originate?
Thoracic spinal cord T1 to T4
Merrill receptors in the lungs have what effect on the heart rate during inspiration?
Increase the heart rate
What are baroreceptors And where they located?
Pressure receptors in the wall of the carotid sinuses and aorta detect changes in atrial pressure in the circulation
What is usually the most important determinant of myocardial bloodflow?
Myocardial oxygen demand
The myocardium usually extracts what percentage of the oxygen in arterial blood compared with what percentage in most other tissues?
65% myocardium
25% other tissues
At what stage is the heart perfused?
Diastole
An increase in heart rate will do what to the time in diastole?
It will diminish it
How is coronary perfusion pressure measured?
CPP = Arterial diastolic pressure - LVEDP
What factor has the largest effect on oxygen supply in the CaO2 equation?
Hemoglobin concentration
What effect will aortic stenosis and regurgitation have on myocardial oxygen supply and why?
Both will decrease supply by worsening blood flow into the coronary arteries
Ventricular ____ function involves ventricular ejection whereas _____ function is related to ventricular filling
Systolic
diastolic
What is a normal cardiac index and how is it calculated?
Normal C.I. = 2.5 - 4.2 L/min/m2
C.I. = CO/BSA
What is a normal mixed venous O2 saturation?
65 to 73%
Wedge pressure is equivalent to ?
LA pressure
Cardiac output is generally directly proportional to what?
HR
Stroke volume is regulated primarily by what three factors?
Preload
Afterload
Contractility
What is preload and what is it equivalent to?
Pressure generated in the left ventricle at the end of diastole
CVP
What is afterload and what is equivalent to?
Resistance or impedance to ejection of blood from the ventricle
SVR
Atrial arrhythmias can reduce ventricular filling due to a loss of the atrial kick. why?
15 to 20% of the volume in the right ventricle comes from the atrial kick
What is a normal CVP?
2-8 mmHg
What effect do respiration and cardiac output have on CVP?
Respiration = increases CVP
Cardiac output = decreases CVP
What normally has the most important effect on contractility?
Sympathetic nervous system activity
What are some causes of myocardial contractility depression?
Anoxia
Acidosis
Depletion of catecholamine
Loss of functioning muscle mass
Stenosis of an AV valve reduces stroke volume by what mechanism?
By decreasing ventricular preload
Stenosis of a semilunar valve reduces stroke volume by what mechanism?
By increasing ventricular afterload
How is ejection fraction calculated and what is a normal value?
EF = (EDV-ESV) / EDV
