Diagnostic Investigations of Cardiovascular SystemA presentation by Tejaswini M

Introduction

•Diagnostic investigations in cardiology are methods of identifying heart conditions associated with unhealthy, pathologic, heart function.

Types•Many•Invasive or Non

invasive

• Mainly dealing with:▫Electrocardiography▫Echocardiography/

Ultrasound▫Cardiac Angiography▫Intravascular

Ultrasound▫Nuclear Heart Scan▫Chest X Ray▫Sphygmomanometer▫CT Scan▫MRI

Electrocardiography

• The recording produced by this procedure is termed an electrocardiogram (ECG or EKG from the German Elektrokardiogramm).

Electrocardiography (ECG / EKG) is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body(electrocardiograph).

Working:• The ECG device detects and amplifies the tiny

electrical changes on the skin that are caused when the heart muscle depolarizes [ contracts ]during each heartbeat.

• This depolarization is detected as tiny rises and falls in the voltage between two electrodes placed on either side of the heart which is displayed as a wavy line either on a screen or on paper.

Lead System• Consists of electrodes used in pairs

▫ Eg: LA+ and RA-, Active and indifferent

• The output from each pair is known as a lead.

• Each lead is said to look at the heart from a different angle.

• Usually, ECG is recorded in 12 leads:

▫ Bipolar▫ Unipolar

Bipolar leads• Electrodes are connected to two limbs one being a

positive pole and other being a negative pole

• The limb leads form the points of Einthoven's triangle

• They are:• Limb lead I: LA+, RA-

• Limb lead II: RA-, LL+

• Limb lead III: LA-, LL+

Unipolar leads• Here the electrodes have two poles, one is active

and the other inactive.• They are:

▫Augmented limb leads▫Precordial leads

• The negative pole is produced by connecting the electrodes, RA; LA; and LL, together, via a simple resistive network.

• Positive pole is active and negative pole inactive

Augmented limb leads• They are: aVR , aVF, aVL• Lead augmented vector right (aVR):• +ve electrode: right arm• -ve electrode: left arm & left foot

• Lead augmented vector left (aVL): • +ve electrode: left arm• -ve electrode: right arm & the left foot

• Lead augmented vector foot (aVF):• +ve electrode: left foot. • -ve electrode: right arm & left arm

Precordial leads• Active electrode-placed directly on 6 points on

the chest.

• Electrodes do not require augmentation.

• They are:▫ V1:4th intercostal space near right sternal margin.▫ V2:4th intercostal space near the left sternal

margin.▫ V4: left 5th intercostal space on midclavicular

line.▫ V3: between V2 and V4.▫ V5: left 5th intercostal space on anterior axillary

line.▫ V6: left 5th intercostal space on mid axillary line.

• Vector: direction of travel of heart’s electrical potential in an instant.

Procedure• Patient lies down on his back. • Several areas on skin of arms,

legs, and chest are cleaned and shaved, and small patches i.e electrodes are attached to these areas.

• The patches are connected by wires to the ECG machine

• The heart's electrical signals are printed into wavy lines on paper.

• Variations in size and length of the different parts of the tracing may indicate a problem in the part of the heart associated with that particular lead.

Devices: Holter monitor, Event monitor, 12 lead electrocardiograph

Cardiac Stress Test

Normal waves

Feature Description CauseP wave Impulse travels from

the SA node towards the AV node, and spreads from the right atrium to the left atrium

Atrial depolarization [contraction]

QRS complex From beginning of Q wave to end of S wave

Ventricular depolarization

T wave Relaxation of ventricles

Ventricular repolarization

Features

Descirption Cause

PR interval

Onset of P wave to onset of Q waveIsoelectric line

Atrial depolarization and conduction through AV node

QT interval

Onset of Q wave and end of T wave

Electrical activity in ventricles [ depolarization and repolarization]

ST segment

End Of S wave and onset of T waveIsoelectric line

Ventricles already depolarized

Purpose: Indications: To measure:• Any damage to the heart• Heart disease• The effects of drugs[Digitalis] or

devices (pacemaker) used to control the heart

• The size and position of the heart chambers

• Heart rate • Heart rhythm

Symptoms like:• Cardiac murmurs• Syncope or collapse• Seizures• Perceived cardiac

dysrhythmias• Angina, palpitations,

breathlesness.

Abnormal ECGHelpful in diagnosing:• Arrhythmias

▫ Tachycardia/Bradycardia▫ Ectopic heart beat▫ Heart block-BBB▫ Atrial flutter and fibrillation▫ Extrasystole▫ Paroxysomal tachycardia▫ Wolff-Parkinson-White syndrome

• Myocardial infarction• Hypertrophy of heart chambers• Coronary Artery Disease• Congenital heart disease

▫ Tetralogy of Fallot▫ PDA

• Cardiac Ischemia• Stable and Unstable Angina

• Infective endocarditis• Valvular heart disease.

▫ Mitral regurgitation▫ Mitral stenosis▫ Mitral valve prolapse▫ Aortic stenosis ▫ Aortic insufficiency▫ Pulmonary valve stenosis▫ Tricuspid regurgitation

• Pericarditis• Aortic dissection• Coarctation of the aorta• C ardiac failure• Hypertensive heart disease• Cardiomyopathy-hypertrophic

/alcoholic/dilated/idiopathic/ peripartum

• Cardiac Tamponade• Atrial Myxoma• Myocarditis• Primary amyloidosis• Stroke

• Myocardial Infarction:▫ Ischaemia-Raised ST segment convex

upwards.▫ Injury-Inverted T -waves peaked and

symmetrical

Echocardiography• It is the diagnostic

procedure which uses ultrasound waves(fq>20000 Hz) to produce 2D 0r 3D image slices of the heart muscle.

• It determines size, shape, movement of valves and heart chambers and flow of blood through the heart.

Working• A transducer containing piezoelectric crystals converts

electrical energy into an ultrasound beam• This beam is directed towards heart.• The beam is reflected when it strikes the surface between tissues

of different densities.• Reflected ultrasound/echo is converted to electrical energy by

piezoelectric crystals which constructs image based on▫ Intensity of echos▫ Time taken for echoes to return

Procedure

•Trans-thoracic echocardiogram(TTE):▫Echocardiogram of the heart through the

thorax external to the body.▫Non-invasive, painless, highly accurate and

quick.

• Trans-esophageal echocardiogram(TEE)▫Echocardiogram of the heart through a

catheter placed in the esophagus which is attached to an ultrasound transducer.

▫Invasive and must be performed under supervision.

• Doppler echocardiography:

▫Waves reflected from RBCs have different frequency than that of transmitted waves.

▫Determines direction and velocity of blood flow.

▫Assessment of Cardiac valve areas and function Abnormal communications between

the left and right side of the heart Valvular regurgitation Calculation of the cardiac output

and ejection fraction.

Heart valve defect

Uses and Indications Assessment of

▫Pericardial effusion▫Congenital Heart Defects▫Valvular heart diseases▫Myocardial Infarction▫High blood pressure/ Hypertensive heart disease▫Hypertrophic cardiomyopathy▫Intracardiac tumors [myxomas] and blood clots▫Aortic regurgitation/stenosis/aneurysm and dissection▫Calcification of valves▫Rheumatic mitral valve disease▫Cardiac failure

VSD

Advantages

•No known risks or side effects.

•No radiation involved.

•Both 2D and 3D images can be

viewed.

Cardiac Angiography• Cardiac

Angiography or arteriography is a medical imaging technique used to visualize the  lumen of the blood vessels [ arteries, veins] and the heart chambers.

• This is traditionally done by inserting a catheter followed by injecting a radio-opaque contrast agent[dye which absorbs the x-rays] into the blood vessel and imaging using a camera and X-ray based techniques such as fluoroscopy.

Procedure• Cardiac Catheterization + X ray fluoroscopy• Patient lies on his back on the X-ray table.• Precautions• A round cylinder or rectangular box that takes the

pictures during fluoroscopy will be moved under the patient during the test.

• The place where the catheter is inserted is shaved and cleaned.

• The doctor numbs the area with a local anesthetic.

• A needle is put into the femoral artery /vein [near groin] or brachial artery/vein[above elbow].

• A guide wire is put through the needle into the blood vessel and the needle is removed.

• The thin flexible catheter is placed over the guide wire and moved into the blood vessel.

• The catheter is then guided through the blood vessels until it reaches the area to be studied [aorta, coronary arteries, left ventricle and atrium and inferior vena cava , right atrium and ventricles, pulmonary artery etc]----Cardiac Catheterization

• The fluoroscope is used to watch the movement of the catheter in the blood vessels.

• When the catheter is in place, Iodine dye is injected through it.

• Several X-ray pictures are taken one after another which may either be still images, displayed on a image intensifier or film, or motion images stored digitally on computer.

• Duration: 1-3 hrs• The catheter is taken out after the

angiogram, and pressure is put on the needle site for 10 to 15 minutes to stop any bleeding.

Uses• Mainly used to detect abnormalities of blood flow

:

▫ A tear in a blood vessel (which can cause blockage or internal bleeding)

▫ Haemorrhages▫ Aneurysms▫ Stenosis ▫ Pattern of blood flow to a tumor. ▫ Abnormal position of blood vessels▫ Abnormal branching of blood vessels since birth▫ Changes in the blood vessels of injured heart.

• Presence or absence of atherosclerosis within the walls of the arteries cannot be clearly determined.

• Not confirmatory..

Intravascular Ultrasound• Principle:

▫ Coronary catheterization+ Ultrasound

• Ultrasound transducer attached at the tip of catheter guided through coronary arteries from femoral/brachial artery.

• Proximal end of catheter attached to ultrasound equipment

• Evaluates▫ Coronary plaques—structure and

composition [not seen in angiography]▫ Wall of blood vessel▫ Connective tissue surrounding vessel

• Prescribed for▫ Coronary angioplasty▫ Stenting

Nuclear Heart Scan• A nuclear heart scan is a type of medical test where a safe, radioactive

material called a tracer is injected through a vein into the bloodstream.

• The tracer travels to the heart and releases energy, which special cameras outside of the body detect to create pictures of different parts of the heart.

• Using computer software, the images are made to appear as if the heart is moving.

ProcedurePretest• The radioactive tracer is injected into the

bloodstream through the intravenous line. • ECG patches are attached to the body to

check the heart's electrical activity during the

test.

Exercise• An exercise stress test maybe done as a part

of nuclear heart scan

Chemical stress• If Patient is unable to exercise, medicine is

used to make the heart beat faster. This is called a chemical stress test.

• Before the exercise or the chemical stress test stops, the tracer is again injected through the IV line.

• The patient then lies very still on a padded table.

• The nuclear heart scan camera, called a gamma camera,[sometimes doughnut shaped] is enclosed in a metal housing which is put in several positions around the body.

• The computer collects the pictures of the heart nearby or in another room.

• Two sets of pictures is taken. One is taken right after exercise /chemical stress test and the other is taken after a period of rest.

• Each set of pictures takes about 15 to 30 minutes.

TypesTwo main types:•Single positron emission

computed tomography (SPECT)

•Cardiac positron emission tomography (PET)

UsesDetects :• The flow of blood throughout the

heart muscle --myocardial perfusion scanning.

• To look for damaged heart muscle due to a previous heart attack, injury, infection, or medicine---myocardial viability testing.

• Pumping action of heart to the body--ventricular function scanning.

UsesAlso evaluates:

▫ Coronary Artery Disease▫ Heart valve diseases▫ Past heart attack (myocardial infarction)▫ Poor pumping function and heart failure

• Decides whether coronary angiography or cardiac catheterization will be helpful.

• Decides whether angioplasty or coronary artery bypass grafting (CABG) will be needed

• Monitors procedures or surgeries, such as CABG or a heart transplant

IndicationsConditions under which the test may be

performed:▫Atrial septal defect▫Dilated cardiomyopathy▫Idiopathic cardiomyopathy▫Peripartum cardiomyopathy▫Senile cardiac amyloid▫Heart failure

Chest X rayA chest X-ray uses a very small amount of radiation to

produce an image of the heart, lungs, and chest bones on film.

Procedure• Patient has to remove all clothes and metallic jewelry from the

waist up and put on a hospital gown for the test.

• Patient then stands very still with his chest against the cassette that contains the film.

• The X-ray machine sends a beam of ionizing radiation through an X-ray tube.

• This energy passes through the chest and is absorbed on film to create a picture.

• Bones and other dense areas show up as lighter shades of gray • Areas that don't absorb the radiation appear as dark gray.

• The entire test takes no more than 10 to 15 minutes.

ViewsPA or postero-anterior view:• Patient stands with his chest

against the container of the film• The X-ray beam from the

machine comes from the posterior/back and moves through the chest to the anterior/front.

Lateral view:• Patient stands sideways in front of

the film with arms raised up. • The X rays penetrate the chest

from the sides.

Uses• Helps to diagnose heart diseases such as

▫Cardiomegaly▫Aneurysm and Coarctation of aorta▫Acute Myocardial Infarction▫Heart failure ▫Pericardial effusion with Tamponade▫ASD, VSD, PDA

• Evaluates placement of devices (pacemakers, defibrillators) or catheters, chest tubes placed during hospitalization.

Cardiomegaly

Heart failure

Sphygmomanometry• A sphygmomanometer is a

device used to measure blood pressure. It is always used in conjunction with a stethoscope.

• A manual sphygmomanometer consists of an inflatable cuff to restrict blood flow, a measuring unit -the mercury manometer or aneroid gauge, and inflation bulb and valve.

Procedure• Patient lies in supine or sitting position

with the Sphygmomanometer at level of the heart

• The arm cuff is tied around the upper arm above the cubital fossa

• Size of cuff should be appropriate for arm• Cuff is attached to the mercury

manometer.• 3 methods:

▫ Palpatory method: Radial artery is palpated Cuff is inflated until radial pulse disappears Pressure is increased further by 20 mm Hg

Pressure is then released slowly through opening of valve

Mercury column is noted when the pulse reappears and is felt

Systolic pressure is obtained

▫Auscultatory Method: Stethoscope placed over the

brachial artery in cubital fossa

Pressure is raised by 20 mm Hg after pulse disappears to occlude the Brachial artery

Pressure is released from cuff through opening of the valve

• A series of sounds—Korotkoff’s sounds are heard▫1st phase:

Sudden clear tapping sound Louder on releasing pressure Appearance-Systolic pressure

▫2nd phase: Murmuring sound

▫3rd phase: Clear louder GONG type of sound

▫4th phase Mild muffled sound

▫5th phase Disappearance of sound Diastolic Blood pressure

▫Oscillatory method: Pressure is increased above

systolic pressure –mercury column remains still

When pressure is decreased—some oscillations occur

When pressure is reduced further-- Amplitude and duration of

oscillations suddenly increase--Systolic BP

When further deflated – amplitude and duration of oscillations is reduced--- Diastolic BP

Inaccurate

UsesDiagnosing•Hypotension•Hypertension

▫Can be indicative of Congestive Heart failure Stroke Myocardial Infarction

Cardiac CT Scan (CCT)• Computerised Tomography (CT) is a

medical imaging method employing tomography, created by computer processing.

• Tomography refers to imaging by sections or sectioning, through the use of any kind of penetrating wave [radiation].

• A three-dimensional image of the inside of the heart is generated from a large series of two-dimensional X-ray picture taken around a single axis of rotation.

• In simpler terms, it is an imaging method that uses x-rays to create cross-sectional pictures of the heart.

Procedure• The patient will be asked to lie on a narrow

table that slides into the center of the CT scanner.

• Once he is inside the scanner, the machine's x-ray beam rotates around him.

• A computer creates separate images of the body area, called slices.

• Three-dimensional models of the body area can be created by stacking the slices together.

• Sometimes an iodine-based dye (contrast dye) is injected intravenously during the scan. The contrast dye travels through the blood vessels, which helps highlight them on the x-ray pictures.

•These images can be stored/ viewed on a monitor, or printed on film.

•Patient must be still during the exam, because movement causes blurred images.

Uses:Helps in evaluating:• Calcium buildup in the walls of

the coronary arteries-coronary calcium scan

• Coronary Artery Disease• Problems with heart function

and heart valves. • Aneurysm and Dissection of

Aorta• Atrial Fibrillation• Pericardial Disease• Wall motion and Ejection

fraction• Cardiac masses and post-

operative abnormalities• Congenital Heart Diseases

Indications:The Patient is Asymptomatic• Family history of coronary artery disease• Persistent high triglyceride levels • Other high risk factors such as smoking, diabetes,

etc.• ECG abnormalities• Abnormalities on a routine stress test• Moderate to severe hypertension• Earlier to non-coronary surgery in the adult

population such as a. Pre-ASD repairb. Pre-valvular repairc. Pre-tumor surgery

Indications The Patient is Symptomatic :• Atypical chest pain (right side,

shoulder tip, etc.)• Suspected dilated cardiomyopathy• Anomalous coronary arteries, ectasia

or aneurysms

Other:• Post-bypass: assessing the status of

bypass grafts. • Post-stent: for assessing in-stent

lumen. • Tumors and cardiac neoplasms

Cardiac Magnetic Resonance Imaging • Cardiovascular magnetic resonance

imaging (CMR) / cardiac MRI, is a medical imaging technology that uses powerful magnets and radio waves to create pictures of the body.

• Single MRI images produced are called slices.

• One exam produces dozens or sometimes hundreds of images which can be combined to produce 3D models.

• The images can be stored on a computer or printed on film.

Principle• The single proton of the nucleus of a hydrogen atom vibrates

, or "resonates," when exposed to bursts of magnetic energy. • When many hydrogen nuclei resonate in response to changes

in a magnetic field, they emit radiofrequency energy. • The MRI machine detects this emitted energy, and converts it

to an image.• Hydrogen nuclei are used because hydrogen atoms are

present in water molecules (H2O), and therefore are present in every tissue in the body.

• Subtle differences in the hydrogen atoms between various parts of a tissue - emit different amounts of energy.

• These energy differences show up as different shades of gray on the MRI which is helpful in detecting areas of cardiac tissue that have poor blood flow (coronary artery disease) or that has been damaged (heart attack).

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Procedure• Patient is asked to wear a hospital gown or clothing without

metal items or ornaments• Patient will lie on a narrow table, which slides into a large

tunnel-shaped scanner. • Sometimes a dye is usually injected before the test

intravenously in the hand or forearm to see images more clearly• Small devices, called coils, may be placed around the head, arm,

or leg, or other areas to be studied. These devices help send and receive the radio waves, and improve the quality of the images.

• During the MRI, the person who operates the machine will watch you from another room.

• An intercom in the room allows patient to speak to the monitoring person at any time.

• The test most often lasts 30-60 minutes, but may take longer.

Closed MRIOpen MRI

Uses• Helps in visualising

▫Heart muscle scar or fat without using a contrast agent▫Heart function using cine imaging▫Infarct imaging using contrast▫Perfusion defects▫Congenital Heart Defects▫Aortic Dissection▫Cardiac tumor▫Cardiomyopathies▫Thrombus▫Pericarditis▫Stenosis of valves

▫Assessing Volume of blood flow and

Ejection fraction Damage caused by Heart

attack Heart Failure Coronary Artery Disease

▫Distinguishing between "stable atherosclerotic plaques and "vulnerable" plaques.

▫Visualising blood vessels and the flow of blood through them -- magnetic resonance angiography (MRA).

Advantages• Safe, non-invasive test• MRI uses radio waves, without ionizing radiation or X

rays• Unlike CT does not carry any risk of causing cancer.• The images generated remarkably complete, detailed

and precise• MRI has the potential of replacing other cardiac tests

like: ▫Echocardiogram, ▫NH scan, ▫Thallium scan▫Diagnostic cardiac catheterization.

References:Books:•Essentials of Medical Physiology - Sembulingam•Hutchinson’s Clinical Methods – Michael Swash•Practical Medicine – P. J Mehta•Macleod’s Clinical Examination – Douglas,

Nicol, Robertson

Internet:•www.google.com•www.wikipedia.org