N201 Wk2

Function of the heart

• pumps oxygenated blood and nutrients to the rest of the body

• receives deoxygenated blood and pumps away unwanted waste products

• maintains heart rate and blood pressure

Point of maximal impulse

• aka apical pulse

• 5th intercostal space, midclavicular line

Layers of the heart

• endocardium

• myocardium

• epicardium

Endocardium

• lining of heart and heart valves

• inner layer

Myocardium

• muscle for pumping

• middle layer

Epicardium

• serous layer; protects the heart

• outer layer

Pericardium

sac surrounding the heart

Flow of blood through the heart

1. Deoxygenated blood flows through inferior/superior vena cava into right atrium

2. Right atrium delivers blood to right ventricle through tricuspid valve

3. Right ventricle delivers blood to pulmonary arteries through pulmonary valve into lungs

4. Lungs receive blood and oxygenate them

5. Oxygenated blood returns to the heart through pulmonary veins and into the left atrium

6. Left atrium delivers blood to left ventricle through mitral valve

7. Left ventricle delivers blood to aorta through aortic valve

8. Aorta transports the blood to rest of the body

Arteries

• high pressure blood is transported from the heart to arteries and arterioles

• delivers blood away from the heart

Veins

• acts as a reservoir of blood and carries low-pressure blood to the heart from venules

• delivers blood to the heart

Capillaries

permits gas exchange, transfer of nutrients, and removal of waste between blood and fluid of tissues

Sinoatrial (SA) node

• cardiac impulses start at SA node

• located in right atrium

• considered heart’s natural pacemaker because it sets the rate and rhythm of heart

Atrioventricular (AV) node

• impulse received by AV node from SA node

• slight delay of impulse in AV node allows atria to fully contract and empty into ventricles

Heart’s conduction system

1. SA node

2. Impulse travels through atria (causing it to contract) and then travels to AV node

3. AV node has slight delay of impulse to allow atria to fully contract

4. Impulse travels to the Bundle of His

5. Impulse continues along Purkinjie fibers reaching terminal point and ventricular contraction

Systole

• contraction phase

• “lub”

Diastole

• relaxation phase

• “dub”

Cardiac output

• total amount of blood ejected from one ventricle of the heart in L/min

• to calculate: Stroke volume x Heart rate

Normal cardiac output

5-6 L/min

Factors that affect cardiac output

• vasoconstriction

• compliance of arteries

• arterial pressure

• amount of volume of blood entering the heart from veins

• exercise

Stroke volume

volume of blood ejected by one ventricle per heartbeat

Three factors determining stroke volume

• preload

• afterload

• contractility

Preload

• volume of blood in the ventricle at the end of diastole

• volume of blood is highest in the ventricle at end of diastole (meaning stretch of muscle fibers is greatest)

Afterload

• resistance directly related to arterial blood pressure and diameter of the blood

• the resistance the heart must overcome to push blood out

Contractility

• can be affected by multiple factors

• sympathetic stimulation or positive inotropic medications may cause contractions to increase

• hypoxia or negative inotropic medications may cause contractions to decrease

Atrioventricular valves

• tricuspid

• mitral

Semilunar valves

• aortic

• pulmonic

S1

• first heart sound heard indicating the closure of atrioventricular valves (mitral and tricuspid)

• “Lub”

S2

• second heart sound signifies closure of semilunar valves (aortic and pulmonic)

• “Dub”

S3 and S4

• abnormal heart sounds

• best heard with bell of stethoscope

• can be normal in children and adults up to age 40

S3

• in adults older than 40, could indicate heart failure and decreased ventricular compliance

• ventricular gallop

• heard as a loud “dub” following S2

S4

• due to decreased ventricular compliance caused by hypertension, aortic stenosis, coronary artery disease or cardiomyopathy

• atrial gallop

• heard as a loud “lub” immediately before S1

Murmurs

• indicate turbulent blood flow through normal or abnormal valves

• whooshing sound

• classified according to timing in cardiac cycle

Systolic murmurs

occurs between S1 and S2

Diastolic murmurs

occurs between S2 and S1

Pericardial friction rub

• abnormal heart sound that is typically heard over left sternal

• grating sound

• occurs due to inflammation, infection, or infiltration in the pericardial sac

Electrocardiogram

records cardiac electrical activity

Depolarization

transmission of electrical impulse that activates contraction of the heart

Repolarization

• occurs when the heart relaxes and prepares to receive the next electrical impulse

• allows chambers to refill with blood

P wave

atrial depolarization (contraction)

PR interval

• related to the rate of cardiac impulse transmitted from the SA node to the AV node

• should be between 0.12-0.20 seconds

QRS complex

• ventricular depolarization (contraction) and atrial repolarization (relaxation)

• should be less than 0.12 seconds

ST segment

• follows ventricular depolarization and occurs prior to start of ventricular repolarization

• elevation indicates myocardial ischemia (MI)

T wave

ventricular repolarization (relaxation) is occurring

QT interval

time for ventricular repolarization to complete

ECG strip

• ECG grid is used to measure components of the ECG impulses

• typical strip is 6 seconds in length and would have total of 30 large blocks

• one large square is equal to 0.20 seconds

• 5 small squares located within one large square

  • 1 small square is equal to 0.04 seconds

Identify the heart rhythm on ECG strip

normal sinus rhythm

Identify the heart rhythm on ECG strip

sinus bradycardia

Sinus bradycardia

occurs when SA node sends an electrical impulse slower than 60 bpm

Causes for sinus bradycardia

• genetics

• sleep apnea

• increased intracranial pressure

• decrease in metabolic needs

• increased exercise tolerance

• hypothyroidism

• medications

• vagus nerve stimulation

• normal aging

• prolonged hypoxia

Medications that can cause sinus bradycardia

• parasympathomimetics (acetylcholine)

• beta blockers (metoprolol)

• digitalis glycosides (digoxin)

• calcium channel blockers (diltiazem)

• antiarrhythmics (amiodarone)

• chemotherapy agents

• lithium

Sinus bradycardia signs and symptoms

• may be asymptomatic or symptomatic

• symptoms include

  • fatigue

  • increased SOB

  • dizziness

Sinus bradycardia (role of the nurse)

• fall precautions for symptomatic bradycardia

• identify cause of bradycardia

• instruct client on lifestyle changes that decrease potential for injury

Sinus bradycardia treatment

• observe asymptomatic clients

• unstable clients

  • IV atropine 1 mg repeat every 3-5 minutes; not to exceed total of 3 mg

  • monitor for changes in HR

  • temporary transcutaneous pacemaker if client continues to remain unstable and symptomatic

Identify the heart rhythm on ECG strip

sinus tachycardia

Sinus tachycardia

• occurs when the SA node sends a faster electrical impulse, greater than 100 BPM

• excessive excitability of the sympathetic nervous system and under stimulation of parasympathetic nervous system can trigger increased electrical impulses fired from SA node

• prolonged tachycardia can lead to decrease in cardiac output which affects amount of oxygenated blood being pumped throughout body

Sinus tachycardia causes

• fluid volume loss

• fluid volume excess

• pain

• fever

• shock

• hyperthyroidism

• stress

• medications

Medications that can cause sinus tachycardia

• atropine

• catecholamines

• theophylline

• illicit drugs (cocaine, amphetamines)

• caffeine

• nicotine

Sinus tachycardia signs and symptoms

• may be asymptomatic or symptomatic

• symptoms include

  • palpitations

  • dizziness

  • lightheadedness

  • elevated temperature

  • chest pain

  • difficulty breathing

Sinus tachycardia (role of the nurse)

• fall precautions

• identify precipitating factors (infection or illness, chronic health condition, stress, pain, anxiety, medications)

• client education

  • stress management

  • discontinue or reduce substances that can increase heart rate

  • change positions slowly

  • decrease physical intensity or activities

Sinus tachycardia treatment

• interventions to decrease fever, pain, stress, fear, or anxiety

• administer medications as ordered (adenosine, beta blockers)

• catheter ablation

Catheter ablation

• performed to destroy abnormally excited cardiac cells responsible for increased heart rate

  • considered minimally invasive and is performed using sedation

  • cardiac catheter tube is inserted into femoral vein or artery, and tube is advanced to heart. areas identified as causing excitability are then heated or frozen to eliminate blood supply to those cells

  • continuous cardiac monitoring detects early arrhythmias post-ablation and assessing pulses ensure adequate circulation and early identification of vascular complications

Identify the heart rhythm on ECG strip

Premature ventricular contraction (PVCs)

Premature ventricular contractions (PVCs)

• occur when early electrical impulses, originating from irritated ventricular cells, are transmitted before the next normal impulse is expected from the SA node

• the QRS complexes identified as PVCs occur early in cardiac cycle and appear much wider than QRS complexes seen in normal sinus

• can be normal and may occur often in healthy clients

• PVCs that occur without identification of abnormal heart structures are considered benign and medically insignificant

Premature ventricular contraction (PVCs) causes

may result from

• cardiac muscle damage

• chronic lung conditions

• electrolyte imbalance (hypokalemia)

• caffeine or alcohol consumption

Bigeminy

every normal heartbeat is followed by a premature beat

Trigeminy

every two normal heartbeats is followed by a premature beat

Premature ventricular contractions risk factors

• inactivity

• poor sleep

• tobacco use

• obesity

• lipid levels

• hypertension

• diabetes

• stress

• hyperlipidemia

• depression

• joint pain

• gout

• osteoarthritis

• cancer

Premature ventricular contractions signs and symptoms

• may be asymptomatic or symptomatic

• symptoms include

  • palpitations

  • lightheadedness

  • chest pain

  • shortness of breath

Premature ventricular contractions (role of the nurse)

• assess for contributing factors that increase likelihood and frequency of PVCs

• ask client to provide timeline of manifestations of PVCs

• obtain a list of medications and chronic health conditions

• analyze ECG (identify frequency and pattern of PVCs)

• client teaching to minimize or prevent PVCs

  • smoking and alcohol cessation

  • eliminate illicit drug use

  • reduce caffeine intake

Premature ventricular contractions treatment

• medications

  • beta blockers (atenolol, bisoprolol, carvedilol, metoprolol, propranolol)

  • antiarrhythmic medications (flecainide, propafenone, amiodarone)

• catheter ablation

  • if medications aren’t effective after 30 days

Identify the heart rhythm on the ECG strip

premature atrial contractions

Premature atrial contractions

• are benign cardiac rhythm occurrences that cause the heart’s electrical conduction system to activate an early heartbeat or impulse from one of the two atrial chambers

• occurs when irritated atrial tissue fires an early electrical impulse before the next normal impulse is expected from the SA node

• seen most often in infants and older individuals

• frequently asymptomatic and do not pose a safety risk to client

Premature atrial contractions (role of the nurse)

• identify lifestyle conditions that are known to precipitate development of PACs

• provide reassurance to client

• lifestyle modifications

• contact health care provider if palpitations or SOB interfere with activities of daily living

Identify the heart rhythm on the ECG strip

First-degree heart block

First-degree heart block

• occurs when the cardiac conduction system is delayed in transmitting an electrical signal through the right atrium to the AV node

• signal is not actually blocked from being sent but the process is slowed down

  • when conduction through the AV node is abnormally slow or prolonged, this results in a PR interval greater than 0.20 seconds

Causes of slow AV node conduction

• increasing of age

• history of cardiac disease (MI)

• electrolyte imbalances (hypokalemia, hypomagnesemia)

• antiarrhythmic medications

• infection

• athletes

• male over 60

First-degree heart block (role of the nurse)

• identify factors that contribute to first degree heart block

  • diets high in sodium, cholesterol or triglycerides

• fall precautions

• assess vital signs and ECG

• provide education on lifestyle modifications

  • eliminate or limit smoking and alcohol consujmption

  • eat a healthy low-cholesterol diet

  • avoid excessive fatigue

Identify the heart rhythm on the ECG strip

Atrial fibrillation

Atrial fibrillation

• common cardiac arrhythmia that occurs when the normal pacemaker of the heart SA node is not firing appropriately; electrical stimuli are being sent from multiple areas in the atria and are transmitting electrical impulses that are rapid, chaotic, and irregular

• irregular impulses do not allow the atria to effectively contract and send blood into the ventricles

• cardiac output decreased due to ineffective and irregular contractions of the heart

• blood clots can form due to irregularity of the blood flow out of ventricles and can cause damage to the brain, lungs, kidneys, or other body organs

Atrial fibrillation risk factors

• history of uncontrolled blood glucose levels

• hyperthyroidism

• obstructive sleep apnea

• smoking

• excessive alcohol intake

• sedentary lifestyle

• age over 60

• obesity

• chronic health conditions (hypertension, chronic heart failure, diabetes, COPD, kidney disease)

Atrial fibrillation signs and symptoms

• may be symptomatic or asymptomatic

• symptoms include

  • irregular pulse

  • hypotension

  • heart palpitations

  • increased heart rate

  • chest discomfort

  • shortness of breath (at rest or activity)

  • exertional fatigue

  • anxiety

  • dizziness

  • lightheadedness

  • syncope

  • weight gain

  • decreased urination

Atrial fibrillation ECG interpretation

• ECG is key diagnostic test to confirm A-fib

• irregular rhythm, HR 100-175 BPM (or even higher)

• P waves replaced by atrial activities between QRS complexes

  • p waves not present before QRS

Atrial fibrillation (role of the nurse)

• Bleeding precautions for clients on anticoagulant therapy

  • falls

  • shaving (electric razor)

  • avoid vigorous teeth brushing and flossing (use of soft bristle toothbrush)

  • avoid participation in contact sports

• Client education

  • report any manifestations of A-fib to provider

  • take medications as prescribed

  • healthy lifestyle modifications

  • avoid stimulants

  • avoid herbal supplements

Atrial fibrillation treatment

• electrocardioversion

• catheter ablation

• anticoagulants

• diet modification

Electrocardioversion

• procedure used to return an abnormal heartbeat to a normal rhythm

• delivers a timed, low-energy electrical shock to the heart to help restore normal rhythm

Identify the heart rhythm on the ECG strip

Atrial flutter

Atrial flutter

• common supraventricular (occurring before the ventricles) cardiac arrhythmia that occurs when the atria are beating in a regular rhythm and increased rate

• less common than AF

• atrial rate can range from 240-400 BPM which is caused by multiple rapid electrical impulses being sent from the atrial too quickly for the AV node to process before transmission to ventricles

• P waves are replaced (no P waves) by multiple sawtooth or flutter waves between QRS complexes

Atrial flutter risk factors

• recent MI or postoperative cardiac surgery

• antiarrhythmic medications (beta blockers, calcium channel blockers, amiodarone, dioginx)

• hypertension

• heart failure

• diabetes

• COPD

• obesity

• thyroid disease

• kidney disease

• stroke

Atrial flutter signs and symptoms

• lightheadedness

• palpitations

• hypotension

• dizziness

• chest discomfort

• shortness of breath

Identify the heart rhythm on the ECG strip

supraventricular tachycardia

Supraventricular tachycardia

• is in a category of cardiac dysrhythmias also known as narrow complex tachycardia

• also called AV nodal reentrant tachycardia and occurs without precipitating factors

• often occurs abruptly and suddenly ends without warning

• originates in AV node and can cause excessive excitability of the atrial tissue resulting in an increased heart rate

Supraventricular tachycardia ECG interpretation

• regular rhythm

• heart rate of 100-220 BPM

• narrow QRS complex less than 0.12 seconds

• undiscernible P wave

Supraventricular tachycardia risk factors

• increased stress levels

• smoking or alcohol intake

• caffeine and other stimulants

• history of heart disease

• Wolff-Parkinson-white syndrome

• pregnancy

• chronic lung disease

• coronary artery disease

• hypertension

• diabetes

• cardiomyopathy

Supraventricular tachycardia signs and symptoms

• symptoms may present suddenly

  • dizziness

  • lightheadedness

  • syncopal episodes

  • fainting

  • hypotension

  • shortness of breath

  • palpitations

Supraventricular tachycardia treatment

• vagal maneuvers

• IV adenosine

• calcium channel blockers (IV diltiazem)

• beta blockers (IV esmolol, IV metoprolol)

Vagal maneuvers

• simple, non-invasive physical techniques that help stimulate the vagus nerve to slow down abnormally fast heart rates

• types include:

  • Valsalva maneuver

  • modified Valsalva maneuver

  • cold water immersion

  • coughing

  • carotid sinus massage

Coronary artery disease

• occurs with a build up of plaque within the coronary arteries

• can cause

  • stable or unstable angina

  • ST elevation myocardial infarction (STEMI)

  • Non-ST elevated myocardial infarction (NSTEMI)

Atherosclerosis

• causes narrowing or occlusion of arteries

• narrowed or occluded arteries cause decreased blood from which leads to decreased oxygenation and perfusion to myocardium

Angina pectoris

term used to describe chest pain and often occurs when the heart has decreased perfusion that can be caused by narrowing of the blood vessels (atherosclerosis)

Types of anginas

• stable (exertional)

• unstable (preinfarction)

• variant (Prinzmetal/vasoplastic)