Cardiovascular System Notes

Heart Valves and Backflow Prevention

Valves are crucial for preventing backflow of blood within the heart.
Understanding the function of each valve is essential.

Atrioventricular (AV) Valves

Function: Prevent backflow from the ventricles into the atria.

Aortic Valve

Function: Prevents backflow from the aorta into the left ventricle.

Pulmonic Valve

Function: Prevents backflow from the pulmonary artery into the right ventricle.

Valve Action During Heart Contraction

When ventricles pump (contract):
- Aortic and pulmonic valves open to allow blood ejection.
- AV valves shut to prevent backflow into the atria.
When atria contract:
- AV valves open to allow blood flow from atria to ventricles.
- Aortic & Pulmonic valves are closed to prevent backflow into the heart chambers.

Circulation of Blood to the Heart (Coronary Circulation)

All body tissues, including the heart muscle itself, require oxygen and glucose delivered via fresh blood supply.
The heart gets its own blood supply immediately after oxygenated blood is pumped into the aorta.
The first branches off the aorta are the coronary arteries.

Coronary Arteries

Function: Supply the heart muscle (myocardium) with oxygen and nutrient-rich blood.
Left ventricle pumps blood into the aorta.
Coronary arteries branch off the aorta to deliver oxygenated blood to heart tissues.

Blood Flow

Left ventricle pumps blood into the aorta.
Aorta directs blood into coronary arteries.
Coronary arteries deliver oxygenated blood to the heart tissues.
Tissues extract oxygen and glucose for energy.
Deoxygenated blood returns to the heart via coronary veins.
Coronary veins dump deoxygenated blood into the vena cava, which then enters the heart to get re-oxygenated in the lungs.

Coronary Arteries (Specifics)

Left coronary artery: Supplies oxygenated blood to the left side of the heart.
Right coronary artery: Supplies oxygenated blood to the right side of the heart.

Heart Rhythm and Electrical Conduction System

A consistent heart rhythm is crucial for proper function.
Normal sinus rhythm refers to the normal heart rate range for an adult human.

Normal Heart Rate Range

Normal range: 60-100 beats per minute (bpm).
Tachycardia: Heart rate above 100 bpm (at rest).
Bradycardia: Heart rate below 60 bpm (at rest).
These ranges refer to RESTING heart rate only.

Brain's Role in Heart Rate Regulation

The brain determines the necessary heart rate and sends signals to the heart via electrical impulses.
Intercalated discs facilitate the transmission of these electrical impulses.

Electrical Conduction System Components

Sinoatrial (SA) Node:
- Located in the right atrium near the coronary sinus.
- Known as the pacemaker of the heart.
- Initiates the electrical signal that sets the heart rate (60-100 bpm).
- If the SA node malfunctions, a pacemaker may be implanted.
Atrioventricular (AV) Node:
- Receives the signal from the SA node.
- Slows down the signal transmission.
Bundle of His (Atrioventricular Bundle):
- Transports the signal from the AV node.
Right and Left Bundle Branches:
- Carry the signal down to the respective ventricles.
Purkinje Fibers:
- Located at the end of the bundle branches in the ventricles.
- Stimulate the ventricular muscle, causing contraction.

Electrical Conduction Pathway Summary

SA node (pacemaker)
AV node
Bundle of His (Atrioventricular Bundle)
Right and left bundle branches
Purkinje fibers

Nursing Terminology: Heart Rate

Bradycardia: Heart rate less than 60 bpm.
Tachycardia: Heart rate greater than 100 bpm.
Resting heart rate range: 60-100 bpm.

Heart Rhythm: Normal Sinus Rhythm vs. Arrhythmia

Normal sinus rhythm: Heartbeats occur at a rate of 60-100 bpm with even spacing.
Arrhythmia: Irregular heart rhythm with unevenly spaced beats (longer or shorter pauses between beats).
Sinus arrhythmia: A specific type of arrhythmia where heart rhythm changes with breathing (e.g., longer pauses during chest expansion).

Premature Ventricular Contraction (PVC)

Ventricles contract too early, before they are full of blood.
Ineffective contraction.

Factors That Influence Heart Rate

Size
Gender
Age
Emotions (fight or flight, adrenaline)
Temperature
Thyroid function (basal metabolic rate)

Cardiac Output

Stroke volume: Amount of blood pumped by one heartbeat.
Cardiac output: Overall volume of blood pumped per minute. Calculated as: Cardiac\,Output = Heart\,Rate \times Stroke\,Volume

Cardiovascular Disease Risk Factors

Risk factors are categorized as modifiable (changeable) and non-modifiable (unchangeable).

Non-Modifiable Risk Factors (Cannot Change)

Age
Sex at birth, determined by chromosome (Male: XY, Female: XX); can't change chromosomes
Heredity (genetics, parents, grandparents)
Body type (e.g., mesomorph, pear shape)

Modifiable Risk Factors (Can Change)

Smoking/tobacco use
Inactivity
Overweight (difficult to change, but possible; medications and hormonal imbalances can affect this)
Saturated fat intake (animal fats, processed foods, fast foods)
Hypertension (high blood pressure; can be controlled with medication and exercise, diet) yes
Type 2 diabetes (can be controlled with medication, diet, and exercise)
Sleep apnea (can be managed with CPAP machines)

Coronary Artery Bypass Graft (CABG)

CABG is a surgical procedure to bypass blockages in the coronary arteries.
Veins from the leg are typically used to create a detour around the blocked artery segment.
This restores blood flow to the heart muscle.
If a patient had a triple bypass, it means has had three CABG

Effects of Aging on the Heart

Chambers get smaller and hold less blood.
Muscle atrophies (decreases in size and strength).
Valves become less flexible and may not function properly.
Increased risk of abnormal heart rhythms (arrhythmias).
The heart doesn't pump as hard, leading to decreased tissue oxygenation.
Cardiac output decreases.

Blood Oxygenation

Aorta contains oxygenated (red) blood.
The right atrium contains deoxygenated (blue) blood.