OVERVIEW OF THE HEARTANATOMY

And ARRHYTHMIAS

Presented by Linda and Livia

www.vancouverhearthealth.com

ANATOMY

The size of a fist

Weighs between 250 and 350 grams

It has 4 chambers

Two superior chambers called AtriaRight Atrium (RA) and Left Atrium (LA)

Two inferior chambers called VentriclesRight Ventricle (RV) and Left Ventricle (LV)

Sulci define the boundaries of the 4 chambers

Coronary sulcus separates the atria from the ventricles

Interventricular sulcus separates the left and right ventricles

Sulci contain major arteries and veins for heart circulation

The heart has 3 layers:

Pericardium – tough membranous sac that encloses and protects the heart (outermost layer of the heart)

A thin layer of clear pericardial fluid inside the pericardium lubricates the external surface of the heart as it beats

Inflammation of the pericardium - PericarditisPericarditis

Myocardium – thickest layer of the heart made ofpure muscle and it gets damaged during a heart attack. It is responsible for contraction and relaxation of the atria and ventricles.

Epicardium – covers the outside of the myocardium. It is a thin layer made of connective tissue and fat.

Endocardium – innermost thin layer of tissue that lines the heart's chambers and valves. The cardiac conduction system is located in this layer of the heart.

Overview of Valves and Blood Flow

Heart Chambers, Valves, and Blood Flow

The heart is a two pump system

The right side of the heart collects blood from the periphery and pumps it through the lungs – called Pulmonary circuitPulmonary circuit

The left side of the heart collects blood from the lungs and pumps it throughout the body – called Systemic circuitSystemic circuit

The left ventricle pumps the blood against the greater resistance to the body (more muscular)

The right ventricle pumps the blood a relative short distance through the pulmonary circuit

(less muscular)

Valves The heart has 4 valves

Atrioventricular valves:Tricuspid valve – controls the blood flow from RA to RV

Bicuspid valve – controls the blood flow from LA to LVThese valves prevent the retrograde blood flow during ventricular contraction

Semilunar valves:Pulmonary valve – lies between the RV and the

pulmonary arteryAortic valve – lies between the LV and the aorta

The cusps of the semilunar valves prevent the back-flow of blood from the arteries to the ventricles

Blood Flow

Venous blood flows into the RA via the superior and inferior vena cava, coronary sinus, and anterior cardiac veins

The RA free wall contracts, and blood flow moves through the tricuspid valve into the RV

The RV free wall contracts, the tricuspid valve closes, and blood flows through the pulmonary valve into the pulmonary artery and the branches of that system

Blood ultimately reaches the alveolar capillaries, where gas exchange occurs

Blood flows back to the LA via the pulmonary veins

The LA free wall contracts, and blood flows through the bicuspid valve and into the LV

The LV free wall contracts, the bicuspid valve closes, and blood flows through the aortic valve into the aorta and its branches, where it is distributed to the coronary circulation and the systemic circulation

Heart Blood Supply

Only the endocardium gets direct blood supply

The myocardium is too thick to permit adequate diffusion of nutrients and oxygen to the cardiac muscle cells and epicardium

Coronary arteries originate from the aortic sinus at the base of the aorta

Left coronary artery (LCA)

Right coronary artery (RCA)

LCA goes towards the left side of the heart before branching into

Left anterior descending (LAD) coronary artery

Circumflex artery (CxA)

The LAD artery supplies blood to the interventricular septum and anterior walls of both ventricles

The CxA branches toward the left margin of the heart in the coronary sulcus and supplies blood to the laterodorsal walls of the LA and LV

Both the LAD and CxA curve around the left ventricular wall and supply small branches that interconnect with the RCA

The RCA supplies blood to the right side of the heart as it follows the AV (atrio-ventricular) groove

It then curves to the back of the heart giving off a posterior interventricular artery (posterior descending artery - PDA)

The RCA and PDA have numerous branches that supply blood to the anterior, posterior, and lateral surfaces of the RV and to the RA

After circulating through the coronary artery system and the myocardial capillaries, it is collected by the cardiac veins

The blood then travels a path similar to that of the coronary arteries but in the opposite direction

On the posterior side of the heart, the cardiac veins form an enlarged vessel → coronary sinus, which empties the blood into the RA

The smaller anterior cardiac veins also empty directly into the RA

Conduction System of the Heart

Cardiac muscle has intrinsic properties → no need for neural stimulation

Cardiac cells interconnect end to end and form intercalated discs

these discs allow electrical impulses to spread from cell to cell and cause the myocardium to act as a single unit

Components of the Conduction System:

Sinoatrial node (SA node)

Atrioventricular node (AV node)

AV bundle (Bundle of His)

Right and Left bundle branches

Purkinje Fibers

The electrical impulse starts at the SA node (intrinsic pacemaker)

The cells depolarize spontaneously at 60 to 80 beats per minute at rest

Electrical activity goes rapidly to AV node via internodal pathways through both atria

Depolarization spreads more slowly across atria. Conduction slows through AV node to allow the atria to contract and fill the ventricles

Depolarization moves rapidly through ventricular conducting system to the apex of the heart

Depolarization wave spreads upward from the apex

Sympathetic nerves and hormones (neropinephrine and epinephrine) stimulate the atria and ventricles of the heart to beat faster → chronotropic effectchronotropic effect

and more forcefully → inotropic effectinotropic effect

Parasympathetic nerves control the atria and slow the heart rate

ECG changes during electrical events in the heart

The SA node initiates a depolarization wave at regular intervals in the atria which is represented by a P wave on an ECG

The P wave represents both depolarization and contraction of atria

When the wave of atrial depolarization enters the AV node, depolarization slows producing

a brief pause – time it takes for the blood to enter the ventricles

Depolarization conducts rapidly through the Bundle of His and its subdivisions and into Purkinje fibers

Depolarization of the ventricular myocardium records as a QRX complex

The horizontal segment of baseline that follows the QRS complex is the ST segment

ST segment is horizontal, flat, and most importantly, it is normally level with other areas of the baseline

If the ST segment is elevated or depressed beyond the normal baseline level, this is usually a sign of serious pathology that may indicate imminent problems

ST segment represents the initial phase of ventricular repolarization

The final T wave represents the final “rapid” phase of ventricular repolarization

What Is Arrhythmia?

Abnormal rhythm of the heart It can feel like a temporary pause and be so

brief that it doesn't change your overall heart rate

Or it can cause the heart rate to be too slow or too fast

What are the signs of Arrhythmia?

If brief it can have almost no symptoms → it can feel like a skipped heart beat that you barely notice

Or it can feel like a fluttering in the chest or neck

If it lasts long enough the heart may not be able to pump enough blood to the body → it can cause tiredness and light-headedness, or the person may pass out

Tachycardia can lead to decreased cardiac out (heart is not able to pump blood effectively) → can lead to shortness of breath, chest pain, light-headedness or loss of consciousness. In severe cases it can cause heart attack and death.

Different Types of Arrhythmias Pacemaker of the heart → SA node → initiates

depolarization of the myocardium

Beats at its own inherent rate of 60 bpm to 100 bpm BradycardiaBradycardia → slow heart rate < 60 bpm

Common in athletes → ↑ stroke volume, ↓ heart rate

Increased vagal stimulation → release of hormones that slow down the heart rate

Patients who receive drugs to slow down the heart rate

Individuals who have disease of the sinus node

SymptomsSymptoms: tiredness, dizziness, light-headedness or fainting

TreatmentTreatment: electronic pacemaker

Types of Bradycardias:

Sick Sinus Syndrome:“malfunction” in the SA node → it fires too slowly due to increasing age or disease

some medications can slow your heartbeat

SolutionSolution:treatment with medication or with an electronic pacemaker

Heart Block:Interruption of the electrical signal to the lower chambers of the heart

It may develop as a side effect of certain heart medications

It may be idiopathic in nature

Or may be due to other forms of circulatory diseases:coronary artery disease

cardiomyopathy

rheumatic heart disease

uncontrolled or untreated high blood pressure

primary conduction system disease

Complete AV block (3rd degree block) is usually due to a complication of a heart attack, but may the result of a heart surgery or infections of the heart muscle

SymptomsSymptoms:Llight-headedness, fatigue, or fainting

DiagnosisDiagnosis:By ECG

Treatment:Implanting an electronic pacemaker

TachycardiaTachycardia → fast heart rate → > 100 bpm Causes:

stimulation of the heart by sympathetic nerves

increased body temperature or toxic conditions of the heart

Factors that affect SNS stimulation of the heart:

blood loss that results in a shock or semishock weakening of the myocardium

Supraventricular Tachycardia (above the ventricle)

rapid heartbeat in the atria or AV node

Atrial flutter

Atrial fibrilation

Paroxysmal supraventricular tachycardia

Wolf-Parkinson-White Syndrome

Atrial Flutter → 250 to 350 atrial depolarization per minute

Due to back-to-back identical atrial depolarization waves

Usually not life threatening

Can cause chest pain, faintness, or others more serious problems

Atrial Fibrillation → multiple foci discharge rapidly at 350-450/min

Very common dysrhythmia

Results in ↓ cardiac output

Usually not life threatening

Causes light-headedness or palpitations

It increases the risk of stroke

SymptomsSymptoms of Atrial fibrillation:

Irregular and fast heart beat

Heart palpitations and rapid thumping in the chest

Chest discomfort, chest pain or pressure

Shortness of breath, particularly with exertion or anxiety

Fatigue

Dizziness, sweating, or nausea

Light-headedness or fainting

Causes Causes of Atrial fibrillation:

In most cases idiopathic in nature

Age

High blood pressure

Infection or inflammation of the heart

Valvular heart disease

Ischemic heart disease

Cardiomyopathy

Conduction system disease

Overactive thyroid

Pulmonary embolism

Hypoxia

Holiday heart syndrome

TreatmentTreatment of Atrial fibrillation

Blood thinners to decrease the risk of stroke

Rhythm control therapy:medication to prevent atrial fibrillation from occurring

electrical cardioversion

ablation

maze procedure

Rate control therapy:medication to slow down the heart rate:

DigitalisCalcium channel blockers (diltiazem and verapamil) Beta-blockers

TreatmentTreatment of Atrial fibrillation

Blood thinners to decrease the risk of stroke

Rhythm control therapy:medication to prevent atrial fibrillation from occurring

electrical cardioversion

ablation

maze procedure

Rate control therapy:medication to slow down the heart rate:

DigitalisCalcium channel blockers (diltiazem and verapamil) Beta-blockers

Paroxysmal supraventricular tachycardia → 140-250/minute

Involves atria or AV node

Usually occurs in young, healthy people

May be distressing and can cause weakness during the paroxysm

Rarely life threatening

Can occur with digitalis toxicity and Wolf- Parkinson-White Syndrome

The following increases your chance for PSVT:Alcohol use

Caffeine use

Illicit drug use

Smoking

SymptomsSymptoms:Anxiety

Chest tightness

Palpitations and rapid pulse

Shortness of breath

Dizziness and fainting

TreatmentTreatment:

Valsalva maneuver

Cough while sitting with your upper body bent forward

Splashing ice water on face

Ablation

Cardioversion

Medications

PacemakerWolf-Parkinson-White syndrome

Ventricular Arrhythmias

Premature Ventricular Contractions

Ventricular Tachycardia

Ventricular Fibrillation

Long QT syndrome

Premature ventricular contractions → a site in the ventricle fires before the next wave of depolarization from the sinus node reaches the ventricle

These are bizarre looking complexes

Relatively benign → often occurs in healthy hearts during rest and exercise → occasional PVC's

Causes:Causes: cigarettes, excessive coffee intake, lack of sleep, various mild toxic states, and emotional irritability

Many PVC's may be markers of underlying cardiac disease such as infarcted or ischemic areas of the heart and can develop into lethal ventricular fibrillation

Ventricular tachycardia → three or more consecutive ventricular beats at 100 bpm or faster

Non-sustained ventricular tachycardia lasts less than 30 seconds

Sustained ventricular tachycardia lasts more than 30 seconds

Wide QRS complex, AV dissociation

A serious condition → occurs due to considerable ischemic damage that is present in the ventricles

→ initiates the lethal condition of ventricular fibrillation

TreatmentTreatment: ICD, ablation, medications - quinidine

Ventricular fibrillation → 250-350/minute

Serious of all cardiac arrhythmias

If not stopped within 1 to 3 minutes it is fatal

It's not a coordinate contraction of all the ventricular muscle at once

The ventricular chambers neither enlarge nor contract but remain in an indeterminate stage of partial contraction → loss of consciousness within 4 to 5 seconds due to lack of blood flow to the brain

CausesCauses:

Sudden electrical shock of the heart

Ischemia of the heart muscle

Treatment:Treatment:CPR

Defibrillation

Long QT syndrome

Normal QT interval is less than half of the R-to-R interval at normal rates

Usually hereditary due to mutations of sodium or potassium channel genes

Acquired forms include hypomagnesemia, hypokalemia, or hypocalcemia, or excess amounts of antiarrhythmic drugs such as quinidine or some antibiotics

SymptomsSymptoms: no major symptoms present

fainting and ventricular arrhythmias due to exercise, intense emotions, or when startled by a noise

TreatmentTreatment: magnesium sulfate for acute LQTS

beta blockers, or ICD for long term LQTS

Long QT syndrome

Delayed repolarization of ventricular muscle can lead to ventricular arrhythmia called Torsades de pointes → if unresolved, it can lead to a deadly arrhythmia

What to do if you think you have What to do if you think you have an undiagnosed Arrhythmia?an undiagnosed Arrhythmia?

Check your heart rate and blood pressure on regular basis

Check your family history Screening → looking for disease before there

are symptoms Seek medical help → your family doctor Your doctor will review your medical history

including a physical exam He/she may send you for further testing

including:

An electrocardiogram (ECG)

Exercise electrocardiogram (Stress test)

Holter monitor

How is Arrhythmia Treated? Life-style changesLife-style changes

Avoiding stress, cutting out alcohol and caffeine, eating healthy diet, being more physically active

MedicationsMedications

Digitalis/digoxin, beta blockers, calcium channel blockers

Surgery or other non-surgical techniquesSurgery or other non-surgical techniques

Ablation

Cardioversion therapy

Implantable pacemaker

Ventricular resection or remodeling

THE ENDTHE END