Cardiac Fundamentals for the Professional RT PDF Handout 2015/Enriquez/Cardiac4WCEC20… · • Cardiovascular Accident (CVA) = 1 in 18 deaths in the U.S. –610,000 Americans have

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Cardiac Fundamentalsfor the Professional RT

Mike Enriquez, MPA, BSRT(R)(CT)

2015

Lecture outline

• Thank You Becki Keith!

– Assistant Professor, Virginia Commonwealth University

• The Cardiac Cycle

• The Electrical conduction system

• The Electrocardiogram

• Cardiac events, aka, “what happens when”

• Prospective & Retrospective Cardiac Gating

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• Cardiovascular disease accounts for 34.3% of deaths in U.S.

• Types of cardiovascular disease:– Coronary Heart Disease – caused by Coronary Artery Disease

– Cardiovascular Accident – ischemic and hemorrhagic• Ischemic: blood clot etiology or atheroma (stenosis, occlusion)

• Hemorrhagic: Uncontrolled Hypertension etiology (burst aneurysm)

– Heart failure, aka CHF- inefficient pump

– Arrhythmia leading to Prospective/Retrospective Gating-repeated MI?

– Heart valve problems- Regurgitation (Mitral Valve Prolapse)Statistics from the Centers for Disease Control and Prevention

and American Heart Association - Heart Disease and Stroke Statistics—2013 Update

• 600,000 deaths from Heart Disease every year (1 in 2.9)

• 385,000 deaths from Coronary Heart Disease every year– Leading cause of death

• 785, 000 Americans have new Myocardial Infarction – 470,000 – recurrent

– Every 34 seconds, an American has a coronary event

– Every 1 minute, an American will die of coronary event

• Cardiovascular Accident (CVA) = 1 in 18 deaths in the U.S.– 610,000 Americans have new CVA

• 185,000 - recurrent

– Every 40 seconds, an American has a CVA

– Every 4 minutes, an American dies of CVA

Statistics from the American Heart Association - Heart Disease and Stroke Statistics—2013 Update

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• Billions of medical imaging tests

per year

– > 1/3 are cardiovascular

procedures

– Low appropriateness

– Little awareness of costs, dose,

and risks

– Litigious society

– 2009: estimated cost of CVD = $475.3 billon

• Estimated cost of all cancer & benign neoplasms = $228 billion

Information From “Economic and Biological Costs of Cardiac Imaging” and the Informed Medical Decisions Foundation

Our Patients…

Angina Pectoris- Chest pain radiating to the left arm

Coronary Artery Disease (CAD)

Myocardial Infarction (MI)

Congestive Heart Failure (CHF)

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Heart Attack Symptoms vs Signs

Technologist Realities…

Observable Symptoms1. sweating- perfuse, cold,

pale, diaphoretic2. SOB- can’t converse

normally, breathlessness3. Dizziness- sometimes to

the point of syncope4. Chest Pain- mild to severe,

breastbone, shoulders, back

5. Other Area Pain-discomfort, tingling in one or both arms; stomach, back, jaw, neck

History questions

6. Restricted, suffocated feeling involving the upper back, torso?

7. Fatigue, days or weeks prior?

8. GI, Flu-like Symptoms including bloating days or weeks prior?

9. Anxiety feeling of impending doom brought on by severe stress?

10. Insomnia prior to event? 50% of patients complain, primarily women

Documenting the Heartbeat/CARDIAC CYCLE

• The ELECTROCARDIOGRAM

– A record of the electrical impulses that travel around and through the various anatomical structures of the heart

– Five Waves: P, Q, R, S, T

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The ElectrocardiogramP-Wave: Depolarization of atria in response to SA node triggering

PR Interval: Delay of AV Node to allow filling of Ventricles

Q-R-S Complex: Depolarization of Ventricles triggers main pumping contractions.

ST Segment: Beginning of Ventricle repolarization

T-Wave: Ventricular repolarization

• Systole- the heart contracts and ejects a large volume of blood from the ventricles

– The top number when reading/acquiring blood pressure measurements

– AtrioVentricular Valves are CLOSED (Lub); SemiLunar Valves are OPEN

• Diastole- the heart relaxes and blood from the atria fill the ventricles

– The lower number when reading/acquiring blood pressure measurements

– AtrioVentricular Valves are OPEN; SemiLunar Valves are CLOSED (Dub)

Documenting the Heartbeat/CARDIAC CYCLE

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SYSTOLEAV Valves CLOSED; SL Valves OPEN

“LUB” – AV Valves CLOSE

DIASTOLEAV Valves OPEN; SL Valves CLOSED

“DUB” – SL Valves CLOSE

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Blood Pressure Numbers at REST

• NORMAL– Less than 120/80

• PREHYPERTENSION– At risk for high blood

pressure

– Between 120/80 and 140/90

• HIGH BLOOD PRESSURE– Diagnosed when…

• SYSTOLE is 140 or higher

• DIASTOLE is 90 and above

Taking a Blood Pressure

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ATTENTION: Diabetics & Chronic Nephropathy Patients

• HIGH BP meds may be prescribed for kidney perfusion– Ie. Enalapril

• SYSTOLE is 130 or higher• DIASTOLE is 80 or higher

Let’s Study This…

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Tachy-, Brady- & the ECG

• Tachycardia- ECG

– Resting heart rate of greater than or equal to 100 beats per minute

Tachy-, Brady- & the ECG

• Bradycardia- ECG

– Resting heart rate of under 60 beats per minute

– Usually not symptomatic until 50 beats per minute or less

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The Big Picture

The RIGHT SIDE controls the PULMONARY CIRCULATION; The LEFT SIDE controls the SYSTEMIC CIRCULATION

• Blood travels to and from heart via the great vessels

• KNOW THESE:

– Aorta

– Pulmonary Trunk/Arteries

– Pulmonary Veins

– Superior Vena Cava

– Inferior Vena Cava

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SYSTOLE is DEMONSTRATED- the AV VALVES are CLOSED; the SEMILUNAR VALVES are OPEN.Also, “LUB” occurs when the AV Valves CLOSE. “DUB” occurs when the SEMILUNAR VALVES CLOSE.

The RIGHT Heart is responsible for the PULMONARY CIRCULATIONPulmonary artery – arteriole – capillary – venule – Pulmonary vein to the

LEFT ATRIUM

The LEFT Heart is responsible for the SYSTEMIC CIRCULATIONSystemic artery – arteriole – capillary – venule – vein to the SVC/IVC

and back to the RIGHT ATRIUM

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Info and Images from EMS World

• Blood is ejected INTO THE pulmonary artery FROM THE

Right Ventricle; and,

• INTO THE Ascending aorta FROM THE Left Ventricle

during ventricular contraction (systole)

• Followed by ventricular relaxation and movement of

blood from the left and right atria into the ventricles

(diastole)• During diastole, the pulmonary and aortic valves close and the coronary

arteries are perfused with oxygenated blood

1st Heart Sound: “LUB”- AV VALVES CLOSE, 2nd Heart Sound: “DUB”- SEMILUNAR VALVES CLOSE

Mitral or Bicuspid Valve closes on the left side;Tricuspid Valve closes on the right sideThese are the Atrio-ventricular or AV valves

Aortic Valve closes on the left side;Pulmonary Valve closes on the right sideThese are the Semi-lunar valves

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CARDIOMEGALY is a Radiologic FINDING NOT A DISEASE!

• 5 inches (12 cm) long

• 3.5 inches (8-9 cm) wide

• 2.5 inches (6 cm) from front to back

• Female = 9 oz

• Male = 10.5 oz

12 cm long

8 cm wide

19 cm long

12 cm wide

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• Heart lies at a 45° angle within the

thorax- the RV is the most anterior

chamber

LV

LA

RV

RA

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• BASE– Broad, superior portion

– Major blood vessels enter

– Mainly formed by left atrium

• APEX

– Inferior - projects anteriorly and

left of midline

– Formed by inferolateral left ventricle

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• Encloses heart, proximal great vessels

• Fixes position in mediastinum

• Protection from infections

• Prevents excessive dilation of heart

• Lubrication

• “Critical fat” between pericardium and heart wall

– More prominent near ventricularoutflow tracts and coronary vessels

– Protection

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• 3 layers:

– Epicardium = thin outer layer, in contact with pericardium

– Myocardium = thick middle layer, strong cardiac muscle

– Endocardium = thin layer lining the inner surface

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HEART CHAMBERS

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– VENTRICLES

• 2 inferior pumping chambers

• Divided by interventricularseptum

– ATRIA

• 2 superior collecting chambers

• Divided by the interatrial septum (patent foramen ovale)

RV

LV

RA

LA

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• One-way directional blood flow through heart

• Can be divided into 2 groups:

– Atrioventricular Valves- M & T

– Semilunar Valves- A & P

Image from Dr. Matthews

A = AorticP= PulmonicM= MitralT= Tricuspid

• Atrioventricular Valves

–Prevent backflow of blood between Atria and Ventricles

1. Right AV valve Tricuspid Valve

2. Left AV valve Mitral (Bicuspid) Valve

R

L

Interventricular

Septum

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• Papillary muscles

– Cone-shaped projections of cardiac muscle

– Anchor cusps of valves to ventricles

• Chordae Tendinae (“Heart Strings”)

– Cord-like tendons - connect papillary muscles to valves

• Semilunar Valves = junction whereventricles meet the great vessels1.Pulmonary Semilunar Valve right ventricle and

pulmonary artery

2.Aortic Semilunar Valve left ventricle and ascending aorta

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REGURGITATIONThe abnormal backflow of blood into a

chamber where it shouldn’t go

REGURGITATION

http://mykentuckyheart.com/images/pictures/mitral_regurgitation.gif

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Mitral Valve Prolapse

resulting in REGURGITATION-

where blood from the LV

wrongfully fills the LA instead of all going through

the Ao Valve!

• Cardiac muscle requires continuous supply of oxygen and nutrients Coronary Circulation:

1. Arteries that supply blood to the heart

2. Cardiac veins that provide venous drainage

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Info from “Coronary CT Angiography” by John D. Grizzard, MD, VCU Health System

• Coronary arteries are 2-4 mm in diameter and move constantly during the cardiac cycle

• High spatial / temporal resolution

▪ Increases in detector rows / slices

▴ More coverage– shorter breath-hold

▪ Decrease in detector size

▴ Increase in spatial resolution

• Able to differentiate plaques on basis of their

composition,

▪ Calcified, lipid, fibrous material or combinations

– Arises from right aortic sinus

– Courses anteriorly between pulmonary trunk and right atrium - descend in coronary (atrioventricular) groove

– At diaphragmatic surface, gives off right marginal branch that runs toward apex of heart

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– Turns to left and enters posterior interventricular groove,

– Gives off posterior descending artery (PDA)

• Joins with left anterior descending artery

LAD

Marginal

Branch

RCA

PDA

Rt Auricle

– Arises from left aortic sinus

– Extends transversely between pulmonary trunk and left atrium to reach coronary groove

– Divides: circumflex & left anterior descending arteries

LAD

LCX

LCA

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• Left anterior descending artery (LAD)

▪ Descends in anterior interventricular

groove toward heart apex

▪ At diaphragmatic surface, joins with PDA

▪ “Widow maker”

• Left circumflex artery (LCX)

▪ Extends into AV groove and extendsaround the base of the heart

▪ Branches termed obtuse marginals

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From Phillips Healthcare

Normal Heart

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• Coronary Sinus

– Main vein of the heart

– Runs along posterior section of coronary sulcus

– Terminates in right atrium; left of IVC

• Tributaries of Coronary Sinus:

– Great Cardiac Vein

– Small Cardiac Vein

– Middle Cardiac Vein

– Lt Posterior Ventricular Vein

– Oblique Vein of left atrium

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Cardiac Conduction

• The heartbeat is generated from the generation and conduction of electrical impulses

• Cardiac conduction is the rate at which the heart conducts electrical impulses

• The impulses cause the heart to contract and relax• The constant cycle of contraction and relaxation

causes blood to be pumped throughout the body

The Four Steps of Cardiac Conduction

Step 1: Pacemaker impulse generation

* SA node generates nerve impulses leading to atrial contraction

Step 2: AV node impulse conduction

* one-tenth second delay allows atria to empty

Step 3: AV bundle impulse conduction

* Impulses carried to right and left ventricle

Step 4: Purkinje fibers impulse conduction

* Ventricular contraction

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• Sinoatrial (SA) node - intrinsic rhythm

• Initiates and propagates each heartbeat

• Atrioventricular (AV) node - base of RA

• Electrical impulse discharged by SA node & transmitted to AV node causing atria to contract

• Bundle of His (AV bundle) - contraction fibers

• Purkinje fibers - transmit impulse to ventricles to make contract and force blood out of heart

CAD, MI, “widow maker”

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• Cardiac Output (CO) = amount of blood pumped

by the left ventricle in one minute• Normal = 5000 to 6000cc

• Ejection Fraction (EF) = % of left ventricular

volume pumped per beat

• Stroke Volume (SV) = amount of blood pumped

by the left ventricle with each contraction (heart

beat)• Normal = approximately 70cc

• Ventricular Rate (VR) = number of times the left

ventricle contracts in one minute• Normal rate = 60 to 100

• CO = SV x VR

CHEST

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Cardiomegaly- documenting the Cardio-Thoracic ratio

Orange: Cardiophrenic angle to cardiophrenic angle

Blue: Costophrenic angle to Costophrenic angle

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Cardiomegaly- documenting the Cardio-Thoracic ratio

Orange: Cardiophrenic angle to cardiophrenic angle

Blue: Costophrenic angle to Costophrenic angle

When the measurement of the Orange line is 51% of the measurement of the Blue line CARDIOMEGALY EXISTS

Cardiomegaly

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Cardiac Hypertrophy

CARDIOMEGALY

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Findings?

Mismarked?

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WHAT HAPPENS & WHEN…

The ELECTROCARDIOGRAM

The Electrocardiogram

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The Electrocardiogram: documenting electrical conduction

• During the…

• P Wave- blood from the atria begins to fill the ventricles

• PR Interval- the ventricles fill completely

• QRS Complex- the main pumping contraction of the ventricles is triggered

The Electrocardiogram: documenting electrical conduction

• During the…

• ST Segment- the ventricles begin to repolarize; also, time during which ventricles are contracting & emptying

• T Wave- complete repolarization of the ventricles

• TP Segment- time during which ventricles are relaxing & filling

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The Timing of Electrical Conduction

Why Gating?• Retrospective or prospective ECG gating

assists in minimizing artifact from cardiac motion

• Use of gating enables coronary artery & aortic valve evaluation

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Retrospective (continuous) vs. Prospective (discrete)

Cardiac GatingProspective (discrete)

• A signal from the R-wave triggers scanning at a set point in the R-R interval

• In this way only a portion of the cardiac cycle is used

Retrospective (continuous)

• Continuous acquisition throughout the cardiac cycle with simultaneous recording of the ECG.

• Data can be reconstructed at any point in the R-R interval.

• Cine loops can be generated

• Higher radiation dose

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GATING

Retrospective GatingContinuous acquisition (mostly)

• At higher Heart Rates:

– Pitch is higher (.3 vs .2) dose is lower

– R-R width determines dose, Fishman recommends 55-75% of the R-R interval

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Prospective GatingDiscrete acquisition

• Pitch is not relative– Data acquisition occurs at a set point during one heart beat

– Moves to the next position on the second beat and then scans the second position

• Scanner matters– FLASH: distance covered per beat approximates 4 cm (64 x 0.6 or

38.4 cm)

– Takes 6-8 beats to scan a heart (12-15 cm)

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Prospective Gating Factors

• Heart rate

• Consistency of heart rate

• Patient compliance

• Patient physical size

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Some Facts RegardingProspectively Gated Cardiac CTA

• mA maximized only during a portion of the R-R interval

• Usual focus is 70-80% of R-R interval

• Up to 70% dose reduction compared with retrospective

• Used routinely for calcium scoring

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Prospective Cardiac CTA Limitations

• Technique should not be used when:

– Heart rates are high- Tachycardia

– Heart beat is irregular- Arrythmia

• Images are acquired during select phrase of R-R interval

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Fall SUNRISE in the CENTRAL VALLEY, California