Otterbein/Grant CRNA A&p Midterm Review - Cardiac

Severe aortic stenosis is characterized by a narrow aortic valve area, which is less than 1 cm, and a high valvular gradient exceeding 40 mmHg. This means that the opening of the aortic valve is significantly restricted, leading to decreased blood flow from the heart to the rest of the body. Therefore, the statement is true.

The formula (SP+(2DP))/3 calculates the Mean Arterial Pressure (MAP). The systolic pressure (SP) represents the highest level of pressure in the arteries during a heartbeat, while the diastolic pressure (DP) represents the lowest level of pressure in the arteries between heartbeats. MAP is a measure of the average pressure in the arteries during a cardiac cycle and is an important indicator of overall cardiovascular health.

Contractility refers to the ability of muscles to contract and generate force. In the context of this question, the amount of intracellular calcium plays a crucial role in determining contractility. Calcium ions are essential for the interaction between actin and myosin, two proteins involved in muscle contraction. When calcium levels are low, the interaction between actin and myosin is inhibited, resulting in reduced contractility. Conversely, when calcium levels are high, the interaction between actin and myosin is enhanced, leading to increased contractility. Therefore, the correct answer is calcium.

Meaning the force of contractions will increase as the heart is filled with more blood

Increasing volume status is less taxing on the heart compared to increasing afterload.

Acidosis is not able to increase contractility because it is a condition characterized by an increase in acidity or a decrease in pH levels in the body. This acidic environment interferes with the normal functioning of the cardiac muscles, leading to a decrease in contractility. On the other hand, sympathetic stimulation, parasympathetic inhibition, and positive inotropic drugs all have the ability to increase contractility by enhancing the force of contraction of the heart muscles.

Ventricles will empty to the same volume despite ejecting more or less blood.

The statement is true because adenosine, K+ ions, CO2, bradykinin, and prostaglandin are indeed coronary vasodilator substances that are naturally released from the myocardium in response to decreased O2 levels. These substances help to dilate the coronary blood vessels, increasing blood flow to the heart muscle and ensuring an adequate oxygen supply.

Peripheral O2 use is not a determinant of diastolic function. Diastolic function refers to the ability of the heart to relax and fill with blood during diastole, the resting phase of the cardiac cycle. It is primarily influenced by factors such as myocardial relaxation, passive ventricular filling, and active ventricular filling. Peripheral O2 use, on the other hand, refers to the utilization of oxygen by the peripheral tissues and is not directly related to the diastolic function of the heart.

The four factors mentioned (heart rate/rhythm, preload, contractility, afterload) all contribute to the overall cardiac output. Heart rate and rhythm determine the number of times the heart contracts per minute, while preload refers to the amount of blood filling the heart before each contraction. Contractility refers to the force with which the heart muscle contracts, and afterload is the resistance the heart must overcome to pump blood out of the left ventricle. All of these factors directly influence the amount of blood pumped by the heart per minute, which is known as cardiac output.

The correct answer is LVEDP (Left Ventricular End-Diastolic Pressure). Coronary perfusion pressure is calculated by subtracting LV tension or LVEDP from Mean Arterial Pressure (MAP). This pressure is important as it represents the pressure gradient across the coronary arteries during diastole, which is essential for adequate blood flow to the heart muscle.

Local anesthetics work in phase 0 of the SA node to prevent spontaneous depolarization that occurs in phase 4 by preventing gated Na+ channels from opening. In phase 4, the SA node is at its resting membrane potential and slowly depolarizes until it reaches the threshold for action potential initiation. By blocking the opening of Na+ channels, local anesthetics prevent the influx of Na+ ions, which is necessary for depolarization and the generation of action potentials. This effectively inhibits the spontaneous depolarization of the SA node and slows down the heart rate.

The Valsalva maneuver involves a forced exhalation against a closed airway, which increases intrathoracic pressure. This leads to stimulation of the baroreceptors located near the carotid arteries and aortic arch. The baroreceptors detect changes in blood pressure and send signals to the brain, resulting in the inhibition of the sympathetic nervous system (SNS) and activation of the parasympathetic nervous system (PNS). This leads to a decrease in heart rate, decrease in contractility of the heart, vasodilation (widening of blood vessels), and ultimately a decrease in blood pressure (hypotension).

It is better to decrease resistance aka increase the radius.
Flow through a blood vessel is proportional to r^4.

The dicrotic notch on an A-line pressure waveform represents retrograde blood flow back into the LV before aortic valve closure. This notch occurs due to the closure of the aortic valve, causing a brief increase in pressure followed by a decrease. This retrograde flow occurs as a result of the elastic recoil of the aorta, which pushes blood back into the left ventricle. Therefore, the statement is true.

Calcium channel blockers work on phase 2 of the ventricular action potential and phase 4 of the SA node action potential.

You can tell you have entered the PA from the RV because in the PA the diastolic will be higher but the systolic will be about the same.

In the non-exercising person, venous blood leaving the heart is only 25% saturated with O2. O2 consumption increases as much as five-fold during exercise, the increased delivery of O2 during exercise can only be met by increasing coronary blood flow.

Poiseuille’s law - determines flow of fluid through a tube – Rate of a liquid through a pipe proportional to the 4th power of the pipe's radius.

Increased HR is the most important factor that negatively affects mVo2.
Even though increased HR increases 02 supply, it increases 02 demand even more. Tachycardia decreases diastolic time which is when 80-90% of coronary filling and myocardial perfusion occurs.

This describes capacitance.
Capacitance = compliance x volume